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The Project Gutenberg eBook of Langley Memoir on
Mechanical Flight, Parts I and II
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Title: Langley Memoir on Mechanical Flight, Parts I and II
Author: S. P. Langley
Charles M. Manly
Release date: January 17, 2015 [eBook #47981]
Most recently updated: October 24, 2024
Language: English
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Credits: E-text prepared by Charlene Taylor, RichardW, and the Online
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*** START OF THE PROJECT GUTENBERG EBOOK LANGLEY
MEMOIR ON MECHANICAL FLIGHT, PARTS I AND II ***
Mechanical Flight, Parts I and II
This eBook is for the use of anyone anywhere in the United States and
most other parts of the world at no cost and with almost no restrictions
whatsoever. You may copy it, give it away or re-use it under the terms
of the Project Gutenberg License included with this eBook or online at
www.gutenberg.org. If you are not located in the United States, you
will have to check the laws of the country where you are located
before using this eBook.
Title: Langley Memoir on Mechanical Flight, Parts I and II
Author: S. P. Langley
Charles M. Manly
Release date: January 17, 2015 [eBook #47981]
Most recently updated: October 24, 2024
Language: English
Other information and formats: www.gutenberg.org/ebooks/47981
Credits: E-text prepared by Charlene Taylor, RichardW, and the Online
Distributed Proofreading Team (http://www.pgdp.net) from
page images generously made available by Internet
Archive/American Libraries
(https://archive.org/details/americana)
*** START OF THE PROJECT GUTENBERG EBOOK LANGLEY
MEMOIR ON MECHANICAL FLIGHT, PARTS I AND II ***
Page 4
The Project Gutenberg eBook, Langley Memoir on Mechanical Flight,
Parts I and II, by S. P. (Samuel Pierpont) Langley and Charles M. (Charles
Matthews) Manly
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◊ Contents
Transcriber's Endnote
Parts I and II, by S. P. (Samuel Pierpont) Langley and Charles M. (Charles
Matthews) Manly
Note:
Images of the original pages are available through Internet Archive/American Libraries. See
https://archive.org/details/langleymemoironm00lang
Some characters might not display in this html version. If so, the reader should consult the
original page images referred to above.
◊ Contents
Transcriber's Endnote
Page 5
SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE
VOLUME 27 NUMBER 3
LANGLEY MEMOIR
ON
MECHANICAL FLIGHT
PART I. 1887 TO 1896
BY
SAMUEL PIERPONT LANGLEY
EDITED BY CHARLES M. MANLY
PART II. 1897 TO 1903
BY
CHARLES M. MANLY
Assistant in Charge of Experiments
VOLUME 27 NUMBER 3
LANGLEY MEMOIR
ON
MECHANICAL FLIGHT
PART I. 1887 TO 1896
BY
SAMUEL PIERPONT LANGLEY
EDITED BY CHARLES M. MANLY
PART II. 1897 TO 1903
BY
CHARLES M. MANLY
Assistant in Charge of Experiments
Page 6
(PUBLICATION 1948)
CITY OF WASHINGTON
PUBLISHED BY THE SMITHSONIAN INSTITUTION
1911
CITY OF WASHINGTON
PUBLISHED BY THE SMITHSONIAN INSTITUTION
1911
Page 7
Commission to whom this Memoir
has been referred:
OTTO HILGARD TITTMAN,
GEORGE OWEN SQUIER,
ALBERT FRANCIS ZAHM.
The Lord Baltimore Press
BALTIMORE, MD., U. S. A.
has been referred:
OTTO HILGARD TITTMAN,
GEORGE OWEN SQUIER,
ALBERT FRANCIS ZAHM.
The Lord Baltimore Press
BALTIMORE, MD., U. S. A.
Page 8
◊
ADVERTISEMENT
The present work, entitled “Langley Memoir on Mechanical Flight,” as
planned by the late Secretary Samuel Pierpont Langley, follows his
publications on “Experiments in Aerodynamics” and “The Internal Work of
the Wind” printed in 1891 and 1893, respectively, as parts of Volume 27 of
the Smithsonian Contributions to Knowledge.
This Memoir was in preparation at the time of Mr. Langley’s death in
1906, and Part I, recording experiments from 1887 to 1896, was written by
him. Part II, on experiments from 1897 to 1903, has been written by Mr.
Charles M. Manly, who became Mr. Langley’s Chief Assistant in June,
1898. The sources of information for this Part were the original carefully
recorded accounts of the experiments described.
It is expected later to publish a third part of the present memoir, to
consist largely of the extensive technical data of tests of the working of
various types of curved surfaces, propellers, and other apparatus.
It is of interest here to note that experiments with the Langley type of
aerodrome1 did not actually cease in December, 1903, when he made his
last trial with the man-carrying machine, but as recently as August 6, 1907,
a French aviator made a flight of nearly 500 feet with an aerodrome of
essentially the same design. (See Appendix.)
ADVERTISEMENT
The present work, entitled “Langley Memoir on Mechanical Flight,” as
planned by the late Secretary Samuel Pierpont Langley, follows his
publications on “Experiments in Aerodynamics” and “The Internal Work of
the Wind” printed in 1891 and 1893, respectively, as parts of Volume 27 of
the Smithsonian Contributions to Knowledge.
This Memoir was in preparation at the time of Mr. Langley’s death in
1906, and Part I, recording experiments from 1887 to 1896, was written by
him. Part II, on experiments from 1897 to 1903, has been written by Mr.
Charles M. Manly, who became Mr. Langley’s Chief Assistant in June,
1898. The sources of information for this Part were the original carefully
recorded accounts of the experiments described.
It is expected later to publish a third part of the present memoir, to
consist largely of the extensive technical data of tests of the working of
various types of curved surfaces, propellers, and other apparatus.
It is of interest here to note that experiments with the Langley type of
aerodrome1 did not actually cease in December, 1903, when he made his
last trial with the man-carrying machine, but as recently as August 6, 1907,
a French aviator made a flight of nearly 500 feet with an aerodrome of
essentially the same design. (See Appendix.)
Page 9
In accordance with the established custom of referring to experts in the
subject treated, all manuscripts intended for publication in the Smithsonian
Contributions to Knowledge, this work was examined and recommended by
a Commission consisting of Mr. O. H. Tittman, Superintendent of the
United States Coast and Geodetic Survey, who witnessed some of the field
trials, George O. Squier, Ph. D. (Johns Hopkins), Major, Signal Corps, U. S.
Army, and Albert Francis Zahm, Ph. D., of Washington City.
CHARLES D. WALCOTT ,
Secretary of the Smithsonian Institution.
[1] The name “aerodrome” was given by Secretary Langley to the flying machine in 1893,
from ἀεροδρομέω (to traverse the air) and ἀεροδρόμος air runner.—Internal Work of the Wind, p.
5.
subject treated, all manuscripts intended for publication in the Smithsonian
Contributions to Knowledge, this work was examined and recommended by
a Commission consisting of Mr. O. H. Tittman, Superintendent of the
United States Coast and Geodetic Survey, who witnessed some of the field
trials, George O. Squier, Ph. D. (Johns Hopkins), Major, Signal Corps, U. S.
Army, and Albert Francis Zahm, Ph. D., of Washington City.
CHARLES D. WALCOTT ,
Secretary of the Smithsonian Institution.
[1] The name “aerodrome” was given by Secretary Langley to the flying machine in 1893,
from ἀεροδρομέω (to traverse the air) and ἀεροδρόμος air runner.—Internal Work of the Wind, p.
5.
Page 10
◊
PREFACE
The present volume on Mechanical Flight consists, as the title-page
indicates, of two parts. The first, dealing with the long and notable series of
early experiments with small models, was written almost entirely by
Secretary Langley with the assistance of Mr. E. C. Huffaker and Mr. G. L.
Fowler in 1897. Such chapters as were not complete have been finished by
the writer and are easily noted as they are written in the third person. It has
been subjected only to such revision as it would have received had Mr.
Langley lived to supervise this publication, and has therefore the highest
value as an historical record. The composition of the second part, dealing
with the later experiments with the original and also new models and the
construction of the larger aerodrome, has necessarily devolved upon me.
This is in entire accordance with the plan formed by Mr. Langley when I
began to work with him in 1898, but it is to me a matter of sincere regret
that the manuscript in its final form has not had the advantage of his
criticism and suggestions. If the reader should feel that any of the
descriptions or statements in this part of the volume leave something to be
desired in fullness of detail, it is hoped that some allowance may be made
for the fact that it has been written in the scanty and scattered moments that
could be snatched from work in other lines which made heavy demands
upon the writer’s time and strength. It is believed, however, that sufficient
data are given to enable any competent engineer to understand thoroughly
even the most complicated phases of the work.
Persons who care only for the accomplished fact may be inclined to
underrate the interest and value of this record. But even they may be
reminded that but for such patient and unremitting devotion as is here
PREFACE
The present volume on Mechanical Flight consists, as the title-page
indicates, of two parts. The first, dealing with the long and notable series of
early experiments with small models, was written almost entirely by
Secretary Langley with the assistance of Mr. E. C. Huffaker and Mr. G. L.
Fowler in 1897. Such chapters as were not complete have been finished by
the writer and are easily noted as they are written in the third person. It has
been subjected only to such revision as it would have received had Mr.
Langley lived to supervise this publication, and has therefore the highest
value as an historical record. The composition of the second part, dealing
with the later experiments with the original and also new models and the
construction of the larger aerodrome, has necessarily devolved upon me.
This is in entire accordance with the plan formed by Mr. Langley when I
began to work with him in 1898, but it is to me a matter of sincere regret
that the manuscript in its final form has not had the advantage of his
criticism and suggestions. If the reader should feel that any of the
descriptions or statements in this part of the volume leave something to be
desired in fullness of detail, it is hoped that some allowance may be made
for the fact that it has been written in the scanty and scattered moments that
could be snatched from work in other lines which made heavy demands
upon the writer’s time and strength. It is believed, however, that sufficient
data are given to enable any competent engineer to understand thoroughly
even the most complicated phases of the work.
Persons who care only for the accomplished fact may be inclined to
underrate the interest and value of this record. But even they may be
reminded that but for such patient and unremitting devotion as is here
Page 11
enregistered, the now accomplished fact of mechanical flight would still
remain the wild unrealized dream which it was for so many centuries.
To such men as Mr. Langley an unsuccessful experiment is not a failure
but a means of instruction, a necessary and often an invaluable stepping-
stone to the desired end. The trials of the large aerodrome in the autumn of
1903, to which the curiosity of the public and the sensationalism of the
newspapers gave a character of finality never desired by Mr. Langley, were
to him merely members of a long series of experiments, as much so as any
trial of one of the small aerodromes or even of one of the earliest rubber-
driven models. Had his health and strength been spared, he would have
gone on with his experiments undiscouraged by these accidents in
launching and undeterred by criticism and misunderstanding.
Moreover, it is to be borne in mind that Mr. Langley’s contribution to the
solution of the problem is not to be measured solely by what he himself
accomplished, important as that is. He began his investigations at a time
when not only the general public but even the most progressive men of
science thought of mechanical flight only as a subject for ridicule, and both
by his epoch-making investigations in aerodynamics and by his own
devotion to the subject of flight itself he helped to transform into a field of
scientific inquiry what had before been almost entirely in the possession of
visionaries.
The original plans for this publication provided for a third part covering
the experimental data obtained in tests of curved surfaces and propellers.
Owing to the pressure of other matters on the writer, the preparation of this
third part is not yet complete and is reserved for later publication.
CHARLES M. MANLY .
NEW YORK CITY.
remain the wild unrealized dream which it was for so many centuries.
To such men as Mr. Langley an unsuccessful experiment is not a failure
but a means of instruction, a necessary and often an invaluable stepping-
stone to the desired end. The trials of the large aerodrome in the autumn of
1903, to which the curiosity of the public and the sensationalism of the
newspapers gave a character of finality never desired by Mr. Langley, were
to him merely members of a long series of experiments, as much so as any
trial of one of the small aerodromes or even of one of the earliest rubber-
driven models. Had his health and strength been spared, he would have
gone on with his experiments undiscouraged by these accidents in
launching and undeterred by criticism and misunderstanding.
Moreover, it is to be borne in mind that Mr. Langley’s contribution to the
solution of the problem is not to be measured solely by what he himself
accomplished, important as that is. He began his investigations at a time
when not only the general public but even the most progressive men of
science thought of mechanical flight only as a subject for ridicule, and both
by his epoch-making investigations in aerodynamics and by his own
devotion to the subject of flight itself he helped to transform into a field of
scientific inquiry what had before been almost entirely in the possession of
visionaries.
The original plans for this publication provided for a third part covering
the experimental data obtained in tests of curved surfaces and propellers.
Owing to the pressure of other matters on the writer, the preparation of this
third part is not yet complete and is reserved for later publication.
CHARLES M. MANLY .
NEW YORK CITY.
Page 12
CONTENTS
PART I
I. Introductory … 1
II. Preliminary … 5
Experiments with small models … 6
Abbreviations and symbols employed … 14
Experiments with Aerodromes Nos. 30 and 31 … 16
III. Available motors … 21
India rubber … 21
Steam engine … 24
Gunpowder, hot-water, compressed air … 25
Gas, electricity … 26
Carbonic-acid gas … 28
IV. Early steam motors and other models … 30
V. On sustaining surfaces … 41
Experiments in the open wind … 42
Relation of air to weight and power … 43
VI. Balancing the aerodrome … 45
Lateral and longitudinal stability … 45
VII. History of construction of frame and engines of aerodromes … 53
1893 … 53
1894 … 64
1895 … 75
1896 … 79
VIII. History of construction of sustaining and guiding surfaces of aerodromes 4, 5, and 6
… 80
Introduction … 80
1893, 1894 … 81
1895 … 85
1896 … 89
IX. History of launching apparatus and field trials of aerodromes 4, 5, and 6 … 92
1892 … 92
1893 … 93
Field trials … 93
PART I
I. Introductory … 1
II. Preliminary … 5
Experiments with small models … 6
Abbreviations and symbols employed … 14
Experiments with Aerodromes Nos. 30 and 31 … 16
III. Available motors … 21
India rubber … 21
Steam engine … 24
Gunpowder, hot-water, compressed air … 25
Gas, electricity … 26
Carbonic-acid gas … 28
IV. Early steam motors and other models … 30
V. On sustaining surfaces … 41
Experiments in the open wind … 42
Relation of air to weight and power … 43
VI. Balancing the aerodrome … 45
Lateral and longitudinal stability … 45
VII. History of construction of frame and engines of aerodromes … 53
1893 … 53
1894 … 64
1895 … 75
1896 … 79
VIII. History of construction of sustaining and guiding surfaces of aerodromes 4, 5, and 6
… 80
Introduction … 80
1893, 1894 … 81
1895 … 85
1896 … 89
IX. History of launching apparatus and field trials of aerodromes 4, 5, and 6 … 92
1892 … 92
1893 … 93
Field trials … 93
Page 13
1894 … 96
1895 … 101
1896 … 106
X. Description of the launching apparatus of aerodromes Nos. 5 and 6 … 110
Description of Aerodrome No. 5 … 111
Description of Aerodrome No. 6 … 120
1895 … 101
1896 … 106
X. Description of the launching apparatus of aerodromes Nos. 5 and 6 … 110
Description of Aerodrome No. 5 … 111
Description of Aerodrome No. 6 … 120
Page 14
PART II
I. Introductory … 123
II. General considerations … 128
III. Experiments with models … 133
Condensed record of flights of aerodromes Nos. 5 and 6, from June 7 to August 3,
1899 … 135
June 7—aerodrome No. 6 … 135
June 13—aerodrome No. 6 … 137
June 22—aerodrome No. 6 … 139
June 23—aerodrome No. 6 … 140
June 27—aerodrome No. 5 … 140
June 30—aerodrome No. 5 … 141
July 1 to July 8 … 142
July 11 to July 14—aerodrome No. 5 … 143
July 19—aerodrome No. 5 … 144
July 27—aerodrome No. 6 … 145
July 28—aerodrome No. 6 … 146
July 29—aerodrome No. 5 … 147
August 1—aerodrome No. 5 … 148
August 3—aerodrome No. 5 … 149
IV. House-boat and launching apparatus … 156
V. Construction of frame of large aerodrome … 164
Transverse frame … 174
Propellers … 178
Aviator’s car … 185
VI. Construction of supporting surfaces … 188
VII. Equilibrium and control … 207
VIII. The experimental engine … 218
IX. The quarter-size model aerodrome … 226
X. Construction and tests of the large engine … 234
XI. Shop tests of the aerodrome … 251
XII. Field trials in 1903 … 255
Statement made by Mr. Manly to associated press … 266
Report of War Department, January, 1904 … 276
Langley aerodrome, Official Report of Board of Ordnance, October, 1904 … 278
Statement to the Press … 280
Present status of the work … 281
Blériot Machine of 1907 on Langley type … 283
Appendix. Study of American Buzzard and “John Crow” … 285
I. Introductory … 123
II. General considerations … 128
III. Experiments with models … 133
Condensed record of flights of aerodromes Nos. 5 and 6, from June 7 to August 3,
1899 … 135
June 7—aerodrome No. 6 … 135
June 13—aerodrome No. 6 … 137
June 22—aerodrome No. 6 … 139
June 23—aerodrome No. 6 … 140
June 27—aerodrome No. 5 … 140
June 30—aerodrome No. 5 … 141
July 1 to July 8 … 142
July 11 to July 14—aerodrome No. 5 … 143
July 19—aerodrome No. 5 … 144
July 27—aerodrome No. 6 … 145
July 28—aerodrome No. 6 … 146
July 29—aerodrome No. 5 … 147
August 1—aerodrome No. 5 … 148
August 3—aerodrome No. 5 … 149
IV. House-boat and launching apparatus … 156
V. Construction of frame of large aerodrome … 164
Transverse frame … 174
Propellers … 178
Aviator’s car … 185
VI. Construction of supporting surfaces … 188
VII. Equilibrium and control … 207
VIII. The experimental engine … 218
IX. The quarter-size model aerodrome … 226
X. Construction and tests of the large engine … 234
XI. Shop tests of the aerodrome … 251
XII. Field trials in 1903 … 255
Statement made by Mr. Manly to associated press … 266
Report of War Department, January, 1904 … 276
Langley aerodrome, Official Report of Board of Ordnance, October, 1904 … 278
Statement to the Press … 280
Present status of the work … 281
Blériot Machine of 1907 on Langley type … 283
Appendix. Study of American Buzzard and “John Crow” … 285
Page 15
Instructions to assistants … 294
Data sheets 1 to 12 … 297
Index … 309
Data sheets 1 to 12 … 297
Index … 309
Page 16
LIST OF PLATES
1. Rubber-motor model aerodromes Nos. 11, 13, 14, 15, 26, 30, 31 … 16
2. Rubber-motor model aerodromes Nos. 11, 13, 14 … 16
3. Rubber-motor model aerodromes Nos. 15, 24 … 16
4. Rubber-motor model aerodrome No. 26 … 16
5. Rubber-pull model aerodrome … 24
6. Rubber-pull model aerodrome … 24
7. Rubber-pull model aerodrome … 24
8. Rubber-pull model aerodrome … 24
9. Rubber-pull model aerodrome … 24
10. Steel frames of aerodromes Nos. 0, 1, 2, 3, 1891 and 1892 … 33
11. Steel frames of aerodromes Nos. 4, 5, 6, 1893, 1895, and 1896 … 53
12. Burners, aeolipiles, and separators … 56
13. Boilers of aerodromes … 56
14. Aerodrome No. 5, December 3, 1895. Plan view. Rudder removed … 78
15. Aerodrome No. 5, December 3, 1895. Side view … 78
16. Early types of wings and systems of guying … 81
17. Aerodrome No. 5. Plan of wings and system of guying … 89
18. House-boat with overhead launching apparatus, 1896 … 106
19. Paths of aerodrome flights, May 6 and November 28, 1896, near Quantico, Va., on the Potomac
River … 108
20. Instantaneous photograph of the aerodrome at the moment after launching in its flight at
Quantico on the Potomac River, May 6, 1896. Enlarged ten times … 108
21. Instantaneous photograph of the aerodrome at a distance in the air during its flight at Quantico
on the Potomac River, May 6, 1896. Enlarged ten times … 108
22. Instantaneous photograph of the aerodrome at a distance in the air during its flight at Quantico
on the Potomac River, May 6, 1896. Enlarged ten times … 108
23. Overhead launching apparatus … 108
24. Overhead launching apparatus … 108
25. Side view of steel frame of aerodrome No. 5 suspended from launching-car, October 24, 1896
… 112
26A. Dimensioned drawing of boiler coils, burners, pump, needle valve, and thrust bearing … 116
1. Rubber-motor model aerodromes Nos. 11, 13, 14, 15, 26, 30, 31 … 16
2. Rubber-motor model aerodromes Nos. 11, 13, 14 … 16
3. Rubber-motor model aerodromes Nos. 15, 24 … 16
4. Rubber-motor model aerodrome No. 26 … 16
5. Rubber-pull model aerodrome … 24
6. Rubber-pull model aerodrome … 24
7. Rubber-pull model aerodrome … 24
8. Rubber-pull model aerodrome … 24
9. Rubber-pull model aerodrome … 24
10. Steel frames of aerodromes Nos. 0, 1, 2, 3, 1891 and 1892 … 33
11. Steel frames of aerodromes Nos. 4, 5, 6, 1893, 1895, and 1896 … 53
12. Burners, aeolipiles, and separators … 56
13. Boilers of aerodromes … 56
14. Aerodrome No. 5, December 3, 1895. Plan view. Rudder removed … 78
15. Aerodrome No. 5, December 3, 1895. Side view … 78
16. Early types of wings and systems of guying … 81
17. Aerodrome No. 5. Plan of wings and system of guying … 89
18. House-boat with overhead launching apparatus, 1896 … 106
19. Paths of aerodrome flights, May 6 and November 28, 1896, near Quantico, Va., on the Potomac
River … 108
20. Instantaneous photograph of the aerodrome at the moment after launching in its flight at
Quantico on the Potomac River, May 6, 1896. Enlarged ten times … 108
21. Instantaneous photograph of the aerodrome at a distance in the air during its flight at Quantico
on the Potomac River, May 6, 1896. Enlarged ten times … 108
22. Instantaneous photograph of the aerodrome at a distance in the air during its flight at Quantico
on the Potomac River, May 6, 1896. Enlarged ten times … 108
23. Overhead launching apparatus … 108
24. Overhead launching apparatus … 108
25. Side view of steel frame of aerodrome No. 5 suspended from launching-car, October 24, 1896
… 112
26A. Dimensioned drawing of boiler coils, burners, pump, needle valve, and thrust bearing … 116
Page 17
26B. Dimensioned drawing of engine No. 5 … 116
27A. Side and end elevations of aerodrome No. 5, May 11, 1896 … 116
27B. Aerodrome No. 5. Plan view. October 24, 1896 … 116
28. Steel frame of aerodrome No. 6 on launching car … 120
29A. Plan view of aerodrome No. 6. October 23, 1896 … 122
29B. Side elevation of aerodrome No. 6. October 23, 1896 … 122
30. Plan view of steel frames and power plants of aerodromes Nos. 5 and 6 … 122
31. Details of aerodrome No. 5 … 122
32. Drawings of proposed man-carrying aerodrome, 1898 … 130
33. Path of flight of aerodrome No. 6, June 7, 1899 … 136
34. Paths of flight of aerodrome No. 6, June 13 and 23, 1899 … 140
35. Aerodrome No. 5 on launching-ways … 142
36. Paths of flights of aerodrome No. 5, July 29, 1899 … 148
37. Experimental forms of superposed surfaces, 1898, 1899. (See also plates 64 and 65.) … 153
38. House-boat and launching apparatus, 1899 … 156
39. Method of attaching guy-wires to guy-posts to relieve torsional strain … 158
40. General plan and details of launching-car … 160
41. Aerodrome on launching-car … 160
42. Details of clutch-post for launching-car … 160
43. Front end of track just preparatory to launching aerodrome … 160
44. Resistance of wires at given velocities … 166
45. Frame of aerodrome A, January 31, 1900 … 168
46. Frame of aerodrome A, January 31, 1900 … 168
47. Frame of aerodrome A, February 1, 1900 … 168
48. Frame of aerodrome A, February 1, 1900 … 168
49. Guy-wire system, July 10, 1902 … 170
50. Guy-wire system, July 10, 1902 … 170
51. Guy-wire system, July 10, 1902 … 170
52. Scale drawing of aerodrome A. End elevation … 170
53. Scale drawing of aerodrome A. Side elevation … 170
54. Scale drawing of aerodrome A. Plan … 170
55. Frame fittings and guy-wire attachments, etc. … 174
56. Frame fittings and guy-wire attachments, etc. … 174
57. Frame fittings and guy-wire attachments, etc. … 174
58. Bed plate gears, etc. … 176
59. Wing clamps … 183
27A. Side and end elevations of aerodrome No. 5, May 11, 1896 … 116
27B. Aerodrome No. 5. Plan view. October 24, 1896 … 116
28. Steel frame of aerodrome No. 6 on launching car … 120
29A. Plan view of aerodrome No. 6. October 23, 1896 … 122
29B. Side elevation of aerodrome No. 6. October 23, 1896 … 122
30. Plan view of steel frames and power plants of aerodromes Nos. 5 and 6 … 122
31. Details of aerodrome No. 5 … 122
32. Drawings of proposed man-carrying aerodrome, 1898 … 130
33. Path of flight of aerodrome No. 6, June 7, 1899 … 136
34. Paths of flight of aerodrome No. 6, June 13 and 23, 1899 … 140
35. Aerodrome No. 5 on launching-ways … 142
36. Paths of flights of aerodrome No. 5, July 29, 1899 … 148
37. Experimental forms of superposed surfaces, 1898, 1899. (See also plates 64 and 65.) … 153
38. House-boat and launching apparatus, 1899 … 156
39. Method of attaching guy-wires to guy-posts to relieve torsional strain … 158
40. General plan and details of launching-car … 160
41. Aerodrome on launching-car … 160
42. Details of clutch-post for launching-car … 160
43. Front end of track just preparatory to launching aerodrome … 160
44. Resistance of wires at given velocities … 166
45. Frame of aerodrome A, January 31, 1900 … 168
46. Frame of aerodrome A, January 31, 1900 … 168
47. Frame of aerodrome A, February 1, 1900 … 168
48. Frame of aerodrome A, February 1, 1900 … 168
49. Guy-wire system, July 10, 1902 … 170
50. Guy-wire system, July 10, 1902 … 170
51. Guy-wire system, July 10, 1902 … 170
52. Scale drawing of aerodrome A. End elevation … 170
53. Scale drawing of aerodrome A. Side elevation … 170
54. Scale drawing of aerodrome A. Plan … 170
55. Frame fittings and guy-wire attachments, etc. … 174
56. Frame fittings and guy-wire attachments, etc. … 174
57. Frame fittings and guy-wire attachments, etc. … 174
58. Bed plate gears, etc. … 176
59. Wing clamps … 183
Page 18
60. Hoisting aerodrome to launching-track … 184
61. Aerodrome on launching-car; front wings in place, guy-wires adjusted … 184
62. Details of guy-posts … 184
63. Guy-post and pin on launching-car … 184
64. Experimental type of superposed wings, March 2, 1899 … 192
65. Experimental type of superposed wings, March 2, 1899 … 192
66. Details of ribs and fittings for wings … 200
67. Cross-section of ribs … 201
68. Automatic equilibrium devices … 212
69. Mechanism of control … 212
70. Plan view of quarter-size model aerodrome, June 1, 1900 … 232
71. Plan view of quarter-size model aerodrome … 232
72. End, side, and three-quarter elevations of quarter-size model aerodrome … 232
73. Launching-car with floats … 232
74. Launching-car with floats … 232
75. Quarter-size model aerodrome equipped with superposed surfaces, June 11, 1901. Side view
… 232
76. Quarter-size model aerodrome equipped with superposed surfaces, June 11, 1901. End view
… 232
77. Cylinders of engine of quarter-size model aerodrome … 233
78. Engine of aerodrome A. Section through cylinder and drum … 236
79. Engine of aerodrome A. End elevation, port side … 236
80. Engine of aerodrome A. Top plan … 236
81. Engine of aerodrome A. Elevation starboard bed plate, sparking mechanism … 236
82. Dynamometer tests of large engine … 248
83. Dynamometer tests of large engine … 248
84. Dynamometer tests of large engine … 248
85. Location of house-boat in center of Potomac River, July 14, 1903 … 256
86. Quarter-size model aerodrome mounted on launching-car … 260
87. Quarter-size model aerodrome in flight, August 8, 1903 … 260
88. Quarter-size model aerodrome in flight, August 8, 1903 … 260
89. Quarter-size model aerodrome in flight, August 8, 1903 … 260
90. Quarter-size model aerodrome in flight, August 8, 1903 … 260
91. Quarter-size model aerodrome in flight, August 8, 1903 … 260
92. Quarter-size model aerodrome in flight, August 8, 1903 … 260
93. Quarter-size model aerodrome at end of flight, August 8, 1903 … 260
61. Aerodrome on launching-car; front wings in place, guy-wires adjusted … 184
62. Details of guy-posts … 184
63. Guy-post and pin on launching-car … 184
64. Experimental type of superposed wings, March 2, 1899 … 192
65. Experimental type of superposed wings, March 2, 1899 … 192
66. Details of ribs and fittings for wings … 200
67. Cross-section of ribs … 201
68. Automatic equilibrium devices … 212
69. Mechanism of control … 212
70. Plan view of quarter-size model aerodrome, June 1, 1900 … 232
71. Plan view of quarter-size model aerodrome … 232
72. End, side, and three-quarter elevations of quarter-size model aerodrome … 232
73. Launching-car with floats … 232
74. Launching-car with floats … 232
75. Quarter-size model aerodrome equipped with superposed surfaces, June 11, 1901. Side view
… 232
76. Quarter-size model aerodrome equipped with superposed surfaces, June 11, 1901. End view
… 232
77. Cylinders of engine of quarter-size model aerodrome … 233
78. Engine of aerodrome A. Section through cylinder and drum … 236
79. Engine of aerodrome A. End elevation, port side … 236
80. Engine of aerodrome A. Top plan … 236
81. Engine of aerodrome A. Elevation starboard bed plate, sparking mechanism … 236
82. Dynamometer tests of large engine … 248
83. Dynamometer tests of large engine … 248
84. Dynamometer tests of large engine … 248
85. Location of house-boat in center of Potomac River, July 14, 1903 … 256
86. Quarter-size model aerodrome mounted on launching-car … 260
87. Quarter-size model aerodrome in flight, August 8, 1903 … 260
88. Quarter-size model aerodrome in flight, August 8, 1903 … 260
89. Quarter-size model aerodrome in flight, August 8, 1903 … 260
90. Quarter-size model aerodrome in flight, August 8, 1903 … 260
91. Quarter-size model aerodrome in flight, August 8, 1903 … 260
92. Quarter-size model aerodrome in flight, August 8, 1903 … 260
93. Quarter-size model aerodrome at end of flight, August 8, 1903 … 260
Page 19
94. Hoisting wing of full-size aerodrome … 263
95. Flight of large aerodrome, October 7, 1903 … 266
96. Flight of large aerodrome, October 7, 1903 … 266
97. Aerodrome being recovered, October 7, 1903 … 270
98. Aerodrome in water, October 7, 1903 … 270
99. Aerodrome in water, October 7, 1903 … 270
100. Aerodrome in water, October 7, 1903 … 270
101. Attempted launching of aerodrome, December 8, 1903 … 274
95. Flight of large aerodrome, October 7, 1903 … 266
96. Flight of large aerodrome, October 7, 1903 … 266
97. Aerodrome being recovered, October 7, 1903 … 270
98. Aerodrome in water, October 7, 1903 … 270
99. Aerodrome in water, October 7, 1903 … 270
100. Aerodrome in water, October 7, 1903 … 270
101. Attempted launching of aerodrome, December 8, 1903 … 274
Page 20
◊
REFERENCES
Aerodynamics. See Langley, S. P. Experiments in Aerodynamics.
L’Aéronaute. See Pénaud, A.
Aeronautical Society. See Harting, P.
Aéroplane automoteur. See Pénaud, A.
Balancing of Engines, Steam, Gas, and Petrol. See Sharp, A.
Century Magazine. See Maxim, H. S.
Comptes Rendus, of the Sessions of the Academy of Sciences. See Langley, S. P. Description du vol
méchanique.
Encyclopædia Britannica. See Flight and Flying Machines.
Experiments in Aerodynamics. See Langley, S. P.
Flight and Flying Machines. Encyclopædia Britannica, 9th ed., Vol. 9, 1879, Edinburgh, pp. 308–322,
figs. 1–45.
Harting, P. Observations of the relative size of the wings and the weight of the pectoral muscles in the
vertebrated flying animals. Annual Report of the Aeronautical Society of Great Britain, No. 5,
1870, Greenwich, pp. 66–77.
Il nuovo aeroplano Blériot, Bollettino della Società Aeronautica Italiana, Anno IV, N. 8, Agosto 1907,
Roma, pp. 279–282, figs. 4.
Langley, Bollettino della Società Aeronautica Italiana, Anno II, Num. 11–12, Nov.–Dic. 1905, Roma,
pp. 187–188, figs. 10.
Langley, S. P. Description du vol méchanique. Comptes Rendus de l’Académie des Sciences, T. 122,
Mai 26, 1896, Paris, pp. 1177–1178.
Langley, S. P. Experiments in Aerodynamics. Smithsonian Contributions to Knowledge, Vol. 27,
1891, Washington, D. C., pp. 115, pl. 10.
Langley, S. P. Le travail intérieur du vent. Revue de l’Aéronautique, 6e année, 3e livraison, 1893,
Paris, pp. 37–68.
Langley, S. P. The Flying Machine. McClures Magazine, Vol. 9, No. 2, June, 1897, N. Y., pp. 647–
660.
Langley, S. P. The Internal Work of the Wind. Smithsonian Contributions to Knowledge, Vol. 27,
1893, Washington, D. C., pp. 23, pl. 6.
McClure’s Magazine. See Langley, S. P. The Flying Machine.
REFERENCES
Aerodynamics. See Langley, S. P. Experiments in Aerodynamics.
L’Aéronaute. See Pénaud, A.
Aeronautical Society. See Harting, P.
Aéroplane automoteur. See Pénaud, A.
Balancing of Engines, Steam, Gas, and Petrol. See Sharp, A.
Century Magazine. See Maxim, H. S.
Comptes Rendus, of the Sessions of the Academy of Sciences. See Langley, S. P. Description du vol
méchanique.
Encyclopædia Britannica. See Flight and Flying Machines.
Experiments in Aerodynamics. See Langley, S. P.
Flight and Flying Machines. Encyclopædia Britannica, 9th ed., Vol. 9, 1879, Edinburgh, pp. 308–322,
figs. 1–45.
Harting, P. Observations of the relative size of the wings and the weight of the pectoral muscles in the
vertebrated flying animals. Annual Report of the Aeronautical Society of Great Britain, No. 5,
1870, Greenwich, pp. 66–77.
Il nuovo aeroplano Blériot, Bollettino della Società Aeronautica Italiana, Anno IV, N. 8, Agosto 1907,
Roma, pp. 279–282, figs. 4.
Langley, Bollettino della Società Aeronautica Italiana, Anno II, Num. 11–12, Nov.–Dic. 1905, Roma,
pp. 187–188, figs. 10.
Langley, S. P. Description du vol méchanique. Comptes Rendus de l’Académie des Sciences, T. 122,
Mai 26, 1896, Paris, pp. 1177–1178.
Langley, S. P. Experiments in Aerodynamics. Smithsonian Contributions to Knowledge, Vol. 27,
1891, Washington, D. C., pp. 115, pl. 10.
Langley, S. P. Le travail intérieur du vent. Revue de l’Aéronautique, 6e année, 3e livraison, 1893,
Paris, pp. 37–68.
Langley, S. P. The Flying Machine. McClures Magazine, Vol. 9, No. 2, June, 1897, N. Y., pp. 647–
660.
Langley, S. P. The Internal Work of the Wind. Smithsonian Contributions to Knowledge, Vol. 27,
1893, Washington, D. C., pp. 23, pl. 6.
McClure’s Magazine. See Langley, S. P. The Flying Machine.
Page 21
Maxim, H. S. Aerial navigation. The power required. Century Magazine, Vol. 42, No. 6, Oct., 1891,
N. Y., pp. 829–836, figs. 1–6.
Pénaud, A. Aeroplane automoteur. L’Aéronaute, 5e année, No. 1, Jan., 1872, Paris, pp. 2–9, figs. 1–4.
Revue de l’Aéronautique. See Langley, S. P. Le travail intérieur du vent.
Sharp, A. Balancing of Engines, Steam, Gas, and Petrol. New York, Longmans, Green & Co., 1907.
Wellner, Georg. Versuche ueber den Luftwiderstand gewölbter Flächen im Winde und auf
Eisenbahnen.
Zeitschrift für Luftschiffahrt, Bd. 12, Beilage, 1893, Berlin, pp. 1–48.
Zeitschrift für Luftschiffahrt. See Wellner, Georg.
N. Y., pp. 829–836, figs. 1–6.
Pénaud, A. Aeroplane automoteur. L’Aéronaute, 5e année, No. 1, Jan., 1872, Paris, pp. 2–9, figs. 1–4.
Revue de l’Aéronautique. See Langley, S. P. Le travail intérieur du vent.
Sharp, A. Balancing of Engines, Steam, Gas, and Petrol. New York, Longmans, Green & Co., 1907.
Wellner, Georg. Versuche ueber den Luftwiderstand gewölbter Flächen im Winde und auf
Eisenbahnen.
Zeitschrift für Luftschiffahrt, Bd. 12, Beilage, 1893, Berlin, pp. 1–48.
Zeitschrift für Luftschiffahrt. See Wellner, Georg.
Page 22
◊
LANGLEY MEMOIR ON MECHANICAL
FLIGHT
P ART I. 1887 TO 1896
B Y S. P. LANGLEY
EDITED BY CHARLES M. MANLY
CHAPTER I
INTRODUCTORY
I2 announced in 1891,3 as the result of experiments carried on by me
through previous years, that it was possible to construct machines which
would give such a velocity to inclined surfaces that bodies indefinitely
heavier than the air could be sustained upon it, and moved through it with
great velocity. In particular, it was stated that a plane surface in the form of
a parallelogram of 76.2 cm. × 12.2 cm. (30 × 4.8 inches), weighing 500
grammes (1.1 lbs.), could be driven through the air with a velocity of 20
metres (65.6 feet) per second in absolutely horizontal flight, with an
expenditure of 1/200 horse-power, or, in other terms, that 1 horse-power
would propel and sustain in horizontal flight, at such a velocity (that is,
about 40 miles an hour), a little over 200 pounds weight of such surface,
where the specific gravity of the plane was a matter of secondary
importance, the support being derived from the elasticity and inertia of the
air upon which the body is made to run rapidly.
It was further specifically remarked that it was not asserted that planes of
any kind were the best forms to be used in mechanical flight, nor was it
asserted, without restrictions, that mechanical flight was absolutely
LANGLEY MEMOIR ON MECHANICAL
FLIGHT
P ART I. 1887 TO 1896
B Y S. P. LANGLEY
EDITED BY CHARLES M. MANLY
CHAPTER I
INTRODUCTORY
I2 announced in 1891,3 as the result of experiments carried on by me
through previous years, that it was possible to construct machines which
would give such a velocity to inclined surfaces that bodies indefinitely
heavier than the air could be sustained upon it, and moved through it with
great velocity. In particular, it was stated that a plane surface in the form of
a parallelogram of 76.2 cm. × 12.2 cm. (30 × 4.8 inches), weighing 500
grammes (1.1 lbs.), could be driven through the air with a velocity of 20
metres (65.6 feet) per second in absolutely horizontal flight, with an
expenditure of 1/200 horse-power, or, in other terms, that 1 horse-power
would propel and sustain in horizontal flight, at such a velocity (that is,
about 40 miles an hour), a little over 200 pounds weight of such surface,
where the specific gravity of the plane was a matter of secondary
importance, the support being derived from the elasticity and inertia of the
air upon which the body is made to run rapidly.
It was further specifically remarked that it was not asserted that planes of
any kind were the best forms to be used in mechanical flight, nor was it
asserted, without restrictions, that mechanical flight was absolutely
Page 23
possible, since this depended upon our ability to get horizontal flight during
transport, and to leave the earth and to return to it in safety. Our ability
actually to do this, it was added, would result from the practice of some
unexplored art or science which might be termed Aerodromics, but on
which I was not then prepared to enter.
I had at that time, however, made certain preliminary experiments with
flying models, which have been continued up to the present year,4 and at the
same time I have continued experiments distinct from these, with the small
whirling-table established at Washington. The results obtained from the
latter being supplemental to those published in “Experiments in
Aerodynamics,” and [p002] being more or less imperfect, were at first
intended not for publication, but for my own information on matters where
even an incomplete knowledge was better than the absence of any.
It is to be remembered that the mechanical difficulties of artificial flight
have been so great that, so far as is known, never at any time in the history
of the world previous to my experiment of May, 1896, had any such
mechanism, however actuated, sustained itself in the air for more than a few
seconds—never, for instance, a single half-minute—and those models
which had sustained themselves for these few seconds, had been in almost
every case actuated by rubber springs, and had been of such a size that they
should hardly be described as more than toys. This refers to actual flights in
free air, unguided by any track or arm, for, since the most economical flight
must always be a horizontal one in a straight line,5 the fact that a machine
has lifted itself while pressed upward against an overhead track which
compels the aerodrome to move horizontally and at the proper angle for
equilibrium, is no proof at all of real “flight.”
I desire to ask the reader’s consideration of the fact that even ten years
ago,6 the whole subject of mechanical flight was so far from having
attracted the general attention of physicists or engineers, that it was
generally considered to be a field fitted rather for the pursuits of the
charlatan than for those of the man of science. Consequently, he who was
bold enough to enter it, found almost none of those experimental data which
transport, and to leave the earth and to return to it in safety. Our ability
actually to do this, it was added, would result from the practice of some
unexplored art or science which might be termed Aerodromics, but on
which I was not then prepared to enter.
I had at that time, however, made certain preliminary experiments with
flying models, which have been continued up to the present year,4 and at the
same time I have continued experiments distinct from these, with the small
whirling-table established at Washington. The results obtained from the
latter being supplemental to those published in “Experiments in
Aerodynamics,” and [p002] being more or less imperfect, were at first
intended not for publication, but for my own information on matters where
even an incomplete knowledge was better than the absence of any.
It is to be remembered that the mechanical difficulties of artificial flight
have been so great that, so far as is known, never at any time in the history
of the world previous to my experiment of May, 1896, had any such
mechanism, however actuated, sustained itself in the air for more than a few
seconds—never, for instance, a single half-minute—and those models
which had sustained themselves for these few seconds, had been in almost
every case actuated by rubber springs, and had been of such a size that they
should hardly be described as more than toys. This refers to actual flights in
free air, unguided by any track or arm, for, since the most economical flight
must always be a horizontal one in a straight line,5 the fact that a machine
has lifted itself while pressed upward against an overhead track which
compels the aerodrome to move horizontally and at the proper angle for
equilibrium, is no proof at all of real “flight.”
I desire to ask the reader’s consideration of the fact that even ten years
ago,6 the whole subject of mechanical flight was so far from having
attracted the general attention of physicists or engineers, that it was
generally considered to be a field fitted rather for the pursuits of the
charlatan than for those of the man of science. Consequently, he who was
bold enough to enter it, found almost none of those experimental data which
Page 24
are ready to hand in every recognized and reputable field of scientific labor.
Let me reiterate the statement, which even now seems strange, that such
disrepute attached so lately to the attempt to make a “flying-machine,” that
hardly any scientific men of position had made even preliminary
investigations, and that almost every experiment to be made was made for
the first time. To cover so vast a field as that which aerodromics is now seen
to open, no lifetime would have sufficed. The preliminary experiments on
the primary question of equilibrium and the intimately associated problems
of the resistance of the sustaining surfaces, the power of the engines, the
method of their application, the framing of the hull structure which held
these, the construction of the propellers, the putting of the whole in initial
motion, were all to be made, and could not be conducted with the exactness
which would render them final models of accuracy.
I beg the reader, therefore, to recall as he reads, that everything here has
been done with a view to putting a trial aerodrome successfully in flight
within a few years, and thus giving an early demonstration of the only kind
which is conclusive in the eyes of the scientific man, as well as of the
general public—a demonstration that mechanical flight is possible-—by
actually flying.
All that has been done, has been with an eye principally to this
immediate [p003] result, and all the experiments given in this book are to be
considered only as approximations to exact truth. All were made with a
view, not to some remote future, but to an arrival within the compass of a
few years at some result in actual flight that could not be gainsaid or
mistaken.
Although many experimenters have addressed themselves to the problem
within the last few years—and these have included men of education and
skill—the general failure to arrive at any actual flight has seemed to throw a
doubt over the conclusions which I had announced as theoretically possible.
When, therefore, I was able to state that on May 6, 1896, such a degree of
success had been attained that an aerodrome, built chiefly of steel, and
driven by a steam engine, had indeed flown for over half a mile—that this
machine had alighted with safety, and had performed a second flight on the
Let me reiterate the statement, which even now seems strange, that such
disrepute attached so lately to the attempt to make a “flying-machine,” that
hardly any scientific men of position had made even preliminary
investigations, and that almost every experiment to be made was made for
the first time. To cover so vast a field as that which aerodromics is now seen
to open, no lifetime would have sufficed. The preliminary experiments on
the primary question of equilibrium and the intimately associated problems
of the resistance of the sustaining surfaces, the power of the engines, the
method of their application, the framing of the hull structure which held
these, the construction of the propellers, the putting of the whole in initial
motion, were all to be made, and could not be conducted with the exactness
which would render them final models of accuracy.
I beg the reader, therefore, to recall as he reads, that everything here has
been done with a view to putting a trial aerodrome successfully in flight
within a few years, and thus giving an early demonstration of the only kind
which is conclusive in the eyes of the scientific man, as well as of the
general public—a demonstration that mechanical flight is possible-—by
actually flying.
All that has been done, has been with an eye principally to this
immediate [p003] result, and all the experiments given in this book are to be
considered only as approximations to exact truth. All were made with a
view, not to some remote future, but to an arrival within the compass of a
few years at some result in actual flight that could not be gainsaid or
mistaken.
Although many experimenters have addressed themselves to the problem
within the last few years—and these have included men of education and
skill—the general failure to arrive at any actual flight has seemed to throw a
doubt over the conclusions which I had announced as theoretically possible.
When, therefore, I was able to state that on May 6, 1896, such a degree of
success had been attained that an aerodrome, built chiefly of steel, and
driven by a steam engine, had indeed flown for over half a mile—that this
machine had alighted with safety, and had performed a second flight on the
Page 25
same day, it was felt that an advance had been made, so great as to
constitute the long desired experimental demonstration of the possibility of
mechanical flight. These results were communicated to the French
Academy in the note given below.7
Independently of the preliminary experiments in aerodynamics already
published, I had been engaged for seven years in the development of flying
models. Although the work was discouraging and often resulted in failure,
success was finally reached under the conditions just referred to, which
obviously admitted of its being reached again, and on a larger scale, if
desired. [p004]
In view of the great importance of these experiments, as demonstrating
beyond question the practicability of the art of mechanical flight, and also
in view of the yet inchoate state of this art, I have thought it worth while to
publish an account of them somewhat in detail, even though they involve an
account of failures; since it is from them, that those to whom it may fall to
continue such constructions, will learn what to avoid, as well as the raison
d’etre of the construction of the machines which have actually flown.
In an established art or science, this description of the essays and failures
which preceded full knowledge would have chiefly an historical interest.
Here almost nothing is yet established beyond the fact that mechanical
flight has actually been attained. The history of failure is in this case, then,
if I do not mistake, most necessary to an understanding of the road to future
success, to which it led, and this has been my motive in presenting what I
have next to say so largely in narrative form.
constitute the long desired experimental demonstration of the possibility of
mechanical flight. These results were communicated to the French
Academy in the note given below.7
Independently of the preliminary experiments in aerodynamics already
published, I had been engaged for seven years in the development of flying
models. Although the work was discouraging and often resulted in failure,
success was finally reached under the conditions just referred to, which
obviously admitted of its being reached again, and on a larger scale, if
desired. [p004]
In view of the great importance of these experiments, as demonstrating
beyond question the practicability of the art of mechanical flight, and also
in view of the yet inchoate state of this art, I have thought it worth while to
publish an account of them somewhat in detail, even though they involve an
account of failures; since it is from them, that those to whom it may fall to
continue such constructions, will learn what to avoid, as well as the raison
d’etre of the construction of the machines which have actually flown.
In an established art or science, this description of the essays and failures
which preceded full knowledge would have chiefly an historical interest.
Here almost nothing is yet established beyond the fact that mechanical
flight has actually been attained. The history of failure is in this case, then,
if I do not mistake, most necessary to an understanding of the road to future
success, to which it led, and this has been my motive in presenting what I
have next to say so largely in narrative form.
Page 26
[p005] ◊
CHAPTER II
PRELIMINARY
Part I of the present work is intended to include an account of the
experiments with actual flying models, made chiefly at or near Washington,
from the earliest with rubber motors up to the construction of the steam
aerodromes that performed the flights of May 6 and November 28, 1896.
An account of some observations conducted at Washington, with the
whirling table, on the reaction of various surfaces upon the air, is relegated
to a later part.
The experiments with working models, which led to the successful
flights, were commenced in 1887, and it has seemed to me preferable to put
them at first in chronological order, and to present to the reader what may
seem instructive in their history, while not withholding from him the
mistaken efforts which were necessarily made before the better path was
found. In this same connection, I may say that I have no professional
acquaintance with steam engineering, as will, indeed, be apparent from the
present record, but it may be observed that none of the counsel which I
obtained from those possessing more knowledge was useful in meeting the
special problems which presented themselves to me, and which were
solved, as far as they have been solved, by constant “trial and error.”
I shall, then, as far as practicable, follow the order of dates in presenting
the work that has been done, but the reader will observe that after the
preliminary investigations and since the close of 1893, at least four or five
independent investigations, attended with constant experiment and radically
distinct kinds of construction, have been going on simultaneously. We have,
for instance, the work in the shop, which is of two essentially different
kinds: first, that on the frames and engines, which finally led to the
construction of an engine of unprecedented lightness; second, the
experimental construction of the supporting and guiding surfaces, which
has involved an entirely different set of considerations, concerned with
CHAPTER II
PRELIMINARY
Part I of the present work is intended to include an account of the
experiments with actual flying models, made chiefly at or near Washington,
from the earliest with rubber motors up to the construction of the steam
aerodromes that performed the flights of May 6 and November 28, 1896.
An account of some observations conducted at Washington, with the
whirling table, on the reaction of various surfaces upon the air, is relegated
to a later part.
The experiments with working models, which led to the successful
flights, were commenced in 1887, and it has seemed to me preferable to put
them at first in chronological order, and to present to the reader what may
seem instructive in their history, while not withholding from him the
mistaken efforts which were necessarily made before the better path was
found. In this same connection, I may say that I have no professional
acquaintance with steam engineering, as will, indeed, be apparent from the
present record, but it may be observed that none of the counsel which I
obtained from those possessing more knowledge was useful in meeting the
special problems which presented themselves to me, and which were
solved, as far as they have been solved, by constant “trial and error.”
I shall, then, as far as practicable, follow the order of dates in presenting
the work that has been done, but the reader will observe that after the
preliminary investigations and since the close of 1893, at least four or five
independent investigations, attended with constant experiment and radically
distinct kinds of construction, have been going on simultaneously. We have,
for instance, the work in the shop, which is of two essentially different
kinds: first, that on the frames and engines, which finally led to the
construction of an engine of unprecedented lightness; second, the
experimental construction of the supporting and guiding surfaces, which
has involved an entirely different set of considerations, concerned with
Page 27
equilibrium and support in flight. These constructions, however successful,
are confined to the shop and are, as will be seen later, useless without a
launching apparatus. The construction of a suitable launching apparatus
itself involved difficulties which took years to overcome. And, finally, the
whole had to be tested by actual flights in free air, which were conducted at
a place some 30 miles distant from the shop where the original construction
went on. [p006]
Simultaneously with these, original experiments with the whirling-table
were being conducted along lines of research, which though necessary have
only been indicated. We have, then, at least five subjects, so distinct that
they can only be properly treated separately, and accordingly they will be
found in Chapters VII, VIII, IX and X, ◊ and in Part Third [in preparation].
It is inevitable that in so complex a study some repetition should present
itself, especially in the narrative form chosen as the best method of
presenting the subject to the reader. Each of these chapters, then, will
contain its own historical account of its own theme, so that each subject can
be pursued continuously in the order of its actual development, while, since
they were all interdependent and were actually going on simultaneously, the
order of dates which is followed in each chapter will be a simple and
sufficient method of reference from one to the other.
E XPERIMENTS W ITH S MALL M ODELS
In order to understand how the need arises for such experiments in fixing
conditions which it might appear were already determined in the work
“Experiments in Aerodynamics,”8 it is to be constantly borne in mind, as a
consideration of the first importance, that the latter experiments, being
conducted with the whirling-table, force the model to move in horizontal
flight and at a constant angle. Now these are ideal conditions, as they avoid
such practical difficulties as maintaining equilibrium and horizontality, and
for this reason alone give results more favorable than are to be expected in
free flight.
Besides this, the values given in “Aerodynamics” were obtained with
rigid surfaces, and these surfaces themselves were small and therefore
are confined to the shop and are, as will be seen later, useless without a
launching apparatus. The construction of a suitable launching apparatus
itself involved difficulties which took years to overcome. And, finally, the
whole had to be tested by actual flights in free air, which were conducted at
a place some 30 miles distant from the shop where the original construction
went on. [p006]
Simultaneously with these, original experiments with the whirling-table
were being conducted along lines of research, which though necessary have
only been indicated. We have, then, at least five subjects, so distinct that
they can only be properly treated separately, and accordingly they will be
found in Chapters VII, VIII, IX and X, ◊ and in Part Third [in preparation].
It is inevitable that in so complex a study some repetition should present
itself, especially in the narrative form chosen as the best method of
presenting the subject to the reader. Each of these chapters, then, will
contain its own historical account of its own theme, so that each subject can
be pursued continuously in the order of its actual development, while, since
they were all interdependent and were actually going on simultaneously, the
order of dates which is followed in each chapter will be a simple and
sufficient method of reference from one to the other.
E XPERIMENTS W ITH S MALL M ODELS
In order to understand how the need arises for such experiments in fixing
conditions which it might appear were already determined in the work
“Experiments in Aerodynamics,”8 it is to be constantly borne in mind, as a
consideration of the first importance, that the latter experiments, being
conducted with the whirling-table, force the model to move in horizontal
flight and at a constant angle. Now these are ideal conditions, as they avoid
such practical difficulties as maintaining equilibrium and horizontality, and
for this reason alone give results more favorable than are to be expected in
free flight.
Besides this, the values given in “Aerodynamics” were obtained with
rigid surfaces, and these surfaces themselves were small and therefore
Page 28
manageable, while larger surfaces, such as are used in actual flight, would
need to be stiffened by guys and like means, which offer resistance to the
air and still further reduce the results obtained. It is, therefore, fairly certain,
that nothing like the lift of 200 pounds to the horse-power for a rate of 40
miles an hour,9 obtained under these ideal conditions with the whirling-
table, will be obtained in actual flight, at least with plane wings.
The data in “Aerodynamics” were, then, insufficient to determine the
conditions of free flight, not alone because the apparatus compels the planes
to move in horizontal flight, but because other ideally perfect conditions are
obtained by surfaces rigidly attached to the whirling-table so as to present
an angle to the wind of advance which is invariable during the course of the
experiment, whereas the surfaces employed in actual flight may evidently
change this angle and cause [p007] the aerodrome to move upward or
downward, and thus depart from horizontal flight so widely as to bring
prompt destruction.
To secure this balance, or equilibrium, we know in theory, that the center
of gravity must be brought nearly under the center of pressure, by which
latter expression we mean the resultant of all the forces which tend to
sustain the aerodrome; but this center of pressure, as may in fact be inferred
from “Aerodynamics,”10 varies with the inclination of the surface. It varies
also with the nature of the surface itself, and for one and the same surface is
constantly shifted unless the whole be rigidly held, as it is on the whirling-
table, and as it cannot be in free flight.
Here, then, are conditions of the utmost importance, our knowledge of
which, as derived from ordinary aerodynamic experiments, is almost
nothing. A consideration of this led me to remark in the conclusion of
“Aerodynamics”:
“I have not asserted, without qualification, that mechanical flight is practically possible, since
this involves questions as to the method of constructing the mechanism, of securing its safe ascent
and descent, and also of securing the indispensable condition for the economic use of the power I
have shown to be at our disposal—the condition, I mean, of our ability to guide it in the desired
horizontal direction during transport—questions which, in my opinion, are only to be answered by
further experiment and which belong to the inchoate art or science of aerodromics on which I do
not enter.”
need to be stiffened by guys and like means, which offer resistance to the
air and still further reduce the results obtained. It is, therefore, fairly certain,
that nothing like the lift of 200 pounds to the horse-power for a rate of 40
miles an hour,9 obtained under these ideal conditions with the whirling-
table, will be obtained in actual flight, at least with plane wings.
The data in “Aerodynamics” were, then, insufficient to determine the
conditions of free flight, not alone because the apparatus compels the planes
to move in horizontal flight, but because other ideally perfect conditions are
obtained by surfaces rigidly attached to the whirling-table so as to present
an angle to the wind of advance which is invariable during the course of the
experiment, whereas the surfaces employed in actual flight may evidently
change this angle and cause [p007] the aerodrome to move upward or
downward, and thus depart from horizontal flight so widely as to bring
prompt destruction.
To secure this balance, or equilibrium, we know in theory, that the center
of gravity must be brought nearly under the center of pressure, by which
latter expression we mean the resultant of all the forces which tend to
sustain the aerodrome; but this center of pressure, as may in fact be inferred
from “Aerodynamics,”10 varies with the inclination of the surface. It varies
also with the nature of the surface itself, and for one and the same surface is
constantly shifted unless the whole be rigidly held, as it is on the whirling-
table, and as it cannot be in free flight.
Here, then, are conditions of the utmost importance, our knowledge of
which, as derived from ordinary aerodynamic experiments, is almost
nothing. A consideration of this led me to remark in the conclusion of
“Aerodynamics”:
“I have not asserted, without qualification, that mechanical flight is practically possible, since
this involves questions as to the method of constructing the mechanism, of securing its safe ascent
and descent, and also of securing the indispensable condition for the economic use of the power I
have shown to be at our disposal—the condition, I mean, of our ability to guide it in the desired
horizontal direction during transport—questions which, in my opinion, are only to be answered by
further experiment and which belong to the inchoate art or science of aerodromics on which I do
not enter.”
Page 29
It is this inchoate art of aerodromics which is begun in the following
experiments with actual flying machines.
In all discussions of flight, especially of soaring flight, the first source to
which one naturally looks for information is birds. But here correct
deductions from even the most accurate of observations are very difficult,
because the observation cannot include all of the conditions under which
the bird is doing its work. If we could but see the wind the problem would
be greatly simplified, but as the matter stands, it may be said that much less
assistance has been derived from studious observations on bird-flight than
might have been anticipated, perhaps because it has been found thus far
impossible to reproduce in the flying machine or aerostatic model the shape
and condition of wing with its flexible and controllable connection with the
body, and especially the instinctive control of the wing to meet the
requirements of flight that are varying from second to second, and which no
automatic adjustment can adequately meet.
At the time I commenced these experiments, almost the only flying-
machine which had really flown was a toy-like model, suggested by A.
Pénaud, a young Frenchman of singular mechanical genius, who
contributed to the world many most original and valuable papers on
Aeronautics, which may be found in the journal “L’Aeronaute.” His
aeroplane is a toy in size, with a small propeller [p008] whose blades are
usually made of two feathers, or of stiff paper, and whose motive power is a
twisted strand of rubber. This power maintains it in the air for a few seconds
and with an ordinary capacity for flight of 50 feet or so, but it embodies a
device for automatically securing horizontal flight, which its inventor was
the first to enunciate.11
Although Pénaud recognized that, theoretically, two screws are necessary
in an aerial propeller, as the use of a single one tends to make the apparatus
revolve on itself, he adopted the single screw on account of the greater
simplicity of construction that it permitted. One of these little machines is
shown as No. 11, Plates 1 and 2.
AB is a stem about 2.5 mm. in diameter and 50 cm. long. It is bent down
at each end, with an offset which supports the rubber and the shaft of the
experiments with actual flying machines.
In all discussions of flight, especially of soaring flight, the first source to
which one naturally looks for information is birds. But here correct
deductions from even the most accurate of observations are very difficult,
because the observation cannot include all of the conditions under which
the bird is doing its work. If we could but see the wind the problem would
be greatly simplified, but as the matter stands, it may be said that much less
assistance has been derived from studious observations on bird-flight than
might have been anticipated, perhaps because it has been found thus far
impossible to reproduce in the flying machine or aerostatic model the shape
and condition of wing with its flexible and controllable connection with the
body, and especially the instinctive control of the wing to meet the
requirements of flight that are varying from second to second, and which no
automatic adjustment can adequately meet.
At the time I commenced these experiments, almost the only flying-
machine which had really flown was a toy-like model, suggested by A.
Pénaud, a young Frenchman of singular mechanical genius, who
contributed to the world many most original and valuable papers on
Aeronautics, which may be found in the journal “L’Aeronaute.” His
aeroplane is a toy in size, with a small propeller [p008] whose blades are
usually made of two feathers, or of stiff paper, and whose motive power is a
twisted strand of rubber. This power maintains it in the air for a few seconds
and with an ordinary capacity for flight of 50 feet or so, but it embodies a
device for automatically securing horizontal flight, which its inventor was
the first to enunciate.11
Although Pénaud recognized that, theoretically, two screws are necessary
in an aerial propeller, as the use of a single one tends to make the apparatus
revolve on itself, he adopted the single screw on account of the greater
simplicity of construction that it permitted. One of these little machines is
shown as No. 11, Plates 1 and 2.
AB is a stem about 2.5 mm. in diameter and 50 cm. long. It is bent down
at each end, with an offset which supports the rubber and the shaft of the
Page 30
screw to which it is hooked. The screw HH 1 is 21 cm. in diameter, and has
two blades made of stiff paper; two are preferable, among other reasons,
because they can be made so that the machine will lie flat when it strikes in
its descent. About the middle of AB there is a “wing” surface DC, 45 cm.
long and 11 cm. broad, the ends C and D being raised and a little curved. In
front of the screw is the horizontal rudder GK having a shape like that of the
first surface, with its ends also turned up, and inclined at a small negative
angle with this wing surface. Along its center is a small fin-like vertical
rudder that steers the device laterally, like the rudder of a ship.
The approximately, but not exactly, horizontal rudder serves to hold the
device in horizontal flight, and its operation can best be understood from
the side elevation. Let CD be the wing plane set nearly in the line of the
stem, which stem it is desired to maintain, in flying, at a small positive
angle, α, with the horizon, α being so chosen that the tendency upward
given by it will just counteract the action of gravity. The weight of the
aeroplane, combined with the resistance due to the reaction of the air caused
by its advance would, under these conditions, just keep it moving onward in
a horizontal line, if there were no disturbance of the conditions. There is,
however, in the wing no power of self-restoration to the horizontal if these
conditions are disturbed. But such a power resides in the rudder GK, which
is not set parallel to the wing, but at a negative angle (α1) with it equal to
the positive angle of the wing with the horizon. It is obvious that, in
horizontal flight, the rudder, being set at this angle, presents its edge to the
wind of advance and consequently offers a minimum resistance as long as
the flight is horizontal. If, however, for any reason the head drops down, the
rear edge of the rudder is raised, and it is at once subjected to the action of
the air upon its upper surface, which has a tendency to lower the rear of the
machine and to restore horizontality. Should the head rise, the lower [p009]
surface of the rudder is subjected to the impact of the air, the rear end is
raised, and horizontality again attained. In addition to this, Pénaud appears
to have contemplated giving the rudder-stem a certain elasticity, and in this
shape it is perhaps as effective a control as art could devise with such
simple means.
two blades made of stiff paper; two are preferable, among other reasons,
because they can be made so that the machine will lie flat when it strikes in
its descent. About the middle of AB there is a “wing” surface DC, 45 cm.
long and 11 cm. broad, the ends C and D being raised and a little curved. In
front of the screw is the horizontal rudder GK having a shape like that of the
first surface, with its ends also turned up, and inclined at a small negative
angle with this wing surface. Along its center is a small fin-like vertical
rudder that steers the device laterally, like the rudder of a ship.
The approximately, but not exactly, horizontal rudder serves to hold the
device in horizontal flight, and its operation can best be understood from
the side elevation. Let CD be the wing plane set nearly in the line of the
stem, which stem it is desired to maintain, in flying, at a small positive
angle, α, with the horizon, α being so chosen that the tendency upward
given by it will just counteract the action of gravity. The weight of the
aeroplane, combined with the resistance due to the reaction of the air caused
by its advance would, under these conditions, just keep it moving onward in
a horizontal line, if there were no disturbance of the conditions. There is,
however, in the wing no power of self-restoration to the horizontal if these
conditions are disturbed. But such a power resides in the rudder GK, which
is not set parallel to the wing, but at a negative angle (α1) with it equal to
the positive angle of the wing with the horizon. It is obvious that, in
horizontal flight, the rudder, being set at this angle, presents its edge to the
wind of advance and consequently offers a minimum resistance as long as
the flight is horizontal. If, however, for any reason the head drops down, the
rear edge of the rudder is raised, and it is at once subjected to the action of
the air upon its upper surface, which has a tendency to lower the rear of the
machine and to restore horizontality. Should the head rise, the lower [p009]
surface of the rudder is subjected to the impact of the air, the rear end is
raised, and horizontality again attained. In addition to this, Pénaud appears
to have contemplated giving the rudder-stem a certain elasticity, and in this
shape it is perhaps as effective a control as art could devise with such
simple means.
Page 31
Of the flight of his little machine, thus directed, Pénaud says:
“If the screw be turned on itself 240 times and the whole left free in a horizontal position, it will
first drop; then, upon attaining its speed, rise and perform a regular flight at 7 or 8 feet from the
ground for a distance of about 40 metres, requiring about 11 seconds for its performance. Some
have flown 60 metres and have remained in the air 13 seconds.12 The rudder controls the
inclination to ascend or descend, causing oscillations in the flight. Finally the apparatus descends
gently in an oblique line, remaining itself horizontal.”
The motive power is a twisted hank of fine rubber strips, which weighs 5
grammes out of a total of 16 grammes for the whole machine, whose center
of gravity should be in advance of the center of surface CD, as will be
demonstrated in another place. This device attracted little notice, and I was
unfamiliar with it when I began my own first constructions at Allegheny, in
1887.
My own earliest models employed a light wooden frame with two
propellers, which were each driven by a strand of twisted rubber.13 In later
forms, the rubber was enclosed and the end strains taken up by the thinnest
tin-plate tubes, or better still, paper tubes strengthened by shellac.
Little was known to me at that time as to the proper proportions between
wing surface, weight and power; and while I at first sought to infer the
relation between wing surface and weight from that of soaring birds, where
it varies from 12 to 1 sq. ft. of wing surface to the pound, yet the ratio was
successively increased in the earlier models, until it became 4 sq. ft. to 1
pound. It may be well to add, however, that the still later experiments with
the steam-driven models, in which the supporting surface was
approximately 2 sq. ft. to the pound, proved that the lack of ability of these
early rubber-driven models to properly sustain themselves even with 4 sq.
ft. of wing surface to the pound, was largely due to the fact that the wings
themselves had not been stiff enough to prevent their being warped by the
air pressure generated by their forward motion.
During the years I presently describe, these tentative constructions were
[p010] renewed at intervals without any satisfactory result, though it became
clear from repeated failures, that the motive power at command would not
“If the screw be turned on itself 240 times and the whole left free in a horizontal position, it will
first drop; then, upon attaining its speed, rise and perform a regular flight at 7 or 8 feet from the
ground for a distance of about 40 metres, requiring about 11 seconds for its performance. Some
have flown 60 metres and have remained in the air 13 seconds.12 The rudder controls the
inclination to ascend or descend, causing oscillations in the flight. Finally the apparatus descends
gently in an oblique line, remaining itself horizontal.”
The motive power is a twisted hank of fine rubber strips, which weighs 5
grammes out of a total of 16 grammes for the whole machine, whose center
of gravity should be in advance of the center of surface CD, as will be
demonstrated in another place. This device attracted little notice, and I was
unfamiliar with it when I began my own first constructions at Allegheny, in
1887.
My own earliest models employed a light wooden frame with two
propellers, which were each driven by a strand of twisted rubber.13 In later
forms, the rubber was enclosed and the end strains taken up by the thinnest
tin-plate tubes, or better still, paper tubes strengthened by shellac.
Little was known to me at that time as to the proper proportions between
wing surface, weight and power; and while I at first sought to infer the
relation between wing surface and weight from that of soaring birds, where
it varies from 12 to 1 sq. ft. of wing surface to the pound, yet the ratio was
successively increased in the earlier models, until it became 4 sq. ft. to 1
pound. It may be well to add, however, that the still later experiments with
the steam-driven models, in which the supporting surface was
approximately 2 sq. ft. to the pound, proved that the lack of ability of these
early rubber-driven models to properly sustain themselves even with 4 sq.
ft. of wing surface to the pound, was largely due to the fact that the wings
themselves had not been stiff enough to prevent their being warped by the
air pressure generated by their forward motion.
During the years I presently describe, these tentative constructions were
[p010] renewed at intervals without any satisfactory result, though it became
clear from repeated failures, that the motive power at command would not
Page 32
suffice, even for a few seconds’ flight for models of sufficient size to enable
a real study to be made of the conditions necessary for successful flight.
In these earliest experiments everything had to be learned about the
relative position of the center of gravity, and what I have called the center
of pressure. In regard to the latter term, it might at first seem that since the
upward pressure of the air is treated as concentrated at one point of the
supporting surface, as the weight is at the center of gravity, this point should
be always in the same position for the same supporting surface. This
relation, however, is never constant. How paradoxical seems the statement
that, if ab be such a supporting surface in the form of a plane of uniform
thickness and weight, suspended at c (ac being somewhat greater than cb )
and subjected to the pressure of a wind in the direction of the arrow, the
pressure on the lesser arm cb will overpower that on the greater arm ac ! We
now know, however, that this must be so, and why, but as it was not known
to the writer till determined by experiments published later in “Experiments
in Aerodynamics,” all this was worked out by trial in the models.
FIG. 1. Diagram of suspended plane showing position of C. P.
It was also early seen that the surface of support could be advantageously
divided into two, with one behind the other, or one over the other, and this
was often, though not always, done in the models.
At the very beginning another difficulty was met which has proved a
constant and ever-increasing one with larger models—the difficulty of
launching them in the air. It is frequently proposed by those unfamiliar with
this difficulty, to launch the aerodrome by placing it upon a platform car or
upon the deck of a steamer, and running the car or boat at an increasing
speed until the aerodrome, which is free to rise, is lifted by the wind of
advance. But this is quite impracticable without means to prevent premature
a real study to be made of the conditions necessary for successful flight.
In these earliest experiments everything had to be learned about the
relative position of the center of gravity, and what I have called the center
of pressure. In regard to the latter term, it might at first seem that since the
upward pressure of the air is treated as concentrated at one point of the
supporting surface, as the weight is at the center of gravity, this point should
be always in the same position for the same supporting surface. This
relation, however, is never constant. How paradoxical seems the statement
that, if ab be such a supporting surface in the form of a plane of uniform
thickness and weight, suspended at c (ac being somewhat greater than cb )
and subjected to the pressure of a wind in the direction of the arrow, the
pressure on the lesser arm cb will overpower that on the greater arm ac ! We
now know, however, that this must be so, and why, but as it was not known
to the writer till determined by experiments published later in “Experiments
in Aerodynamics,” all this was worked out by trial in the models.
FIG. 1. Diagram of suspended plane showing position of C. P.
It was also early seen that the surface of support could be advantageously
divided into two, with one behind the other, or one over the other, and this
was often, though not always, done in the models.
At the very beginning another difficulty was met which has proved a
constant and ever-increasing one with larger models—the difficulty of
launching them in the air. It is frequently proposed by those unfamiliar with
this difficulty, to launch the aerodrome by placing it upon a platform car or
upon the deck of a steamer, and running the car or boat at an increasing
speed until the aerodrome, which is free to rise, is lifted by the wind of
advance. But this is quite impracticable without means to prevent premature
Page 33
displacement, for the large surface and slight weight renders any model of
considerable size unmanageable in the least wind, such as is always present
in the open air. It is, therefore, necessary in any launching apparatus that the
aerodrome be held rigidly until the very moment of release, and that instant
and simultaneous release from the apparatus be made at all the sustaining
points at the proper moment. [p011]
There is but a very partial analogy in this case to the launching of a ship,
which is held to her ways by her great weight. Here, the “ship” is liable to
rise from her ways or be turned over laterally at any instant, unless it is
securely fastened to them in a manner to prevent its rising, but not to
prevent its advancing.
The experiments with rubber-driven models commenced in April, 1887,
at the Allegheny Observatory, were continued at intervals (partly there, but
chiefly in Washington) for three or four years, during which time between
thirty and forty independent models were constructed, which were so
greatly altered in the course of experiment that more nearly one hundred
models were in reality tried. The result of all this extended labor was wholly
inconclusive, but as subsequent trials of other motors (such as compressed
air, carbonic-acid gas, electric batteries, and the like) proved futile, and
(before the steam engine) only the rubber gave results, however
unsatisfactory, in actual flight, from which anything could be learned, I
shall give some brief account of these experiments, which preceded and
proved the necessity of using the steam engine, or other like energetic
motor, even in experimental models.
An early attempt was made in April, 1887, with a model consisting of a
frame formed of two wooden pieces, each about 1 metre long and 4
centimetres wide, made for lightness, of star-shaped section, braced with
cross-pieces and carrying two long strips of rubber, each about 1 mm. thick,
30 mm. wide, 2 metres long, doubled, weighing 300 grammes. Each of
these strips could be wound to about 300 turns, one end being made fast to
the front of the frame, the other to the shaft of a four-bladed propeller 30
cm. in diameter. The wings were made of lightest pine frames, over which
paper was stretched, and were double, one being superposed upon the other.
considerable size unmanageable in the least wind, such as is always present
in the open air. It is, therefore, necessary in any launching apparatus that the
aerodrome be held rigidly until the very moment of release, and that instant
and simultaneous release from the apparatus be made at all the sustaining
points at the proper moment. [p011]
There is but a very partial analogy in this case to the launching of a ship,
which is held to her ways by her great weight. Here, the “ship” is liable to
rise from her ways or be turned over laterally at any instant, unless it is
securely fastened to them in a manner to prevent its rising, but not to
prevent its advancing.
The experiments with rubber-driven models commenced in April, 1887,
at the Allegheny Observatory, were continued at intervals (partly there, but
chiefly in Washington) for three or four years, during which time between
thirty and forty independent models were constructed, which were so
greatly altered in the course of experiment that more nearly one hundred
models were in reality tried. The result of all this extended labor was wholly
inconclusive, but as subsequent trials of other motors (such as compressed
air, carbonic-acid gas, electric batteries, and the like) proved futile, and
(before the steam engine) only the rubber gave results, however
unsatisfactory, in actual flight, from which anything could be learned, I
shall give some brief account of these experiments, which preceded and
proved the necessity of using the steam engine, or other like energetic
motor, even in experimental models.
An early attempt was made in April, 1887, with a model consisting of a
frame formed of two wooden pieces, each about 1 metre long and 4
centimetres wide, made for lightness, of star-shaped section, braced with
cross-pieces and carrying two long strips of rubber, each about 1 mm. thick,
30 mm. wide, 2 metres long, doubled, weighing 300 grammes. Each of
these strips could be wound to about 300 turns, one end being made fast to
the front of the frame, the other to the shaft of a four-bladed propeller 30
cm. in diameter. The wings were made of lightest pine frames, over which
paper was stretched, and were double, one being superposed upon the other.
Page 34
Each was 15 cm. wide, and 120 cm. long. The distance between them was
12 cm. and the total surface a little more than 3600 sq. cm. (4 square feet).
In flying, the rubber was so twisted that the propellers were run in opposite
directions. The weight of the whole apparatus was not quite 1 kilogramme,
or about 1 pound to 2 feet of sustaining surface, which proved to be entirely
too great a weight for the power of support. When placed upon the
whirling-table, it showed a tendency to soar at a speed of about ten miles an
hour, but its own propellers were utterly insufficient to sustain it.
In this attempt, which was useful only in showing how much was to be
learned of practical conditions, the primary difficulty lay in making the
model light enough and sufficiently strong to support its power. This
difficulty continued to be fundamental through every later form; but besides
this, the adjustment of the center of gravity to the center of pressure of the
wings, the disposition of the wings themselves, the size of the propellers,
the inclination and number of their blades, and a great number of other
details, presented themselves for examination. [p012] Even in the first model,
the difficulty of launching the machine or giving it the necessary
preliminary impulse was disclosed—a difficulty which may perhaps not
appear serious to the reader, but which in fact required years of experiment
to remove.
By June, 1887 two other models, embodying various changes that had
suggested themselves, had been constructed. Each of these had a single
propeller (one an 18 12 -inch propeller with eight adjustable blades, the other
a 24-inch propeller with four adjustable blades) and was sustained by two
pairs of curved wings 4 feet 7 inches long. It is, however, unnecessary to
dwell further on these details, since these models also proved altogether too
heavy in relation to their power, and neither of them ever made an actual
flight.
At this period my time became so fully occupied with the experiments in
aerodynamics (which are not here in question) that during the next two
years little additional was done in making direct investigations in flight.
12 cm. and the total surface a little more than 3600 sq. cm. (4 square feet).
In flying, the rubber was so twisted that the propellers were run in opposite
directions. The weight of the whole apparatus was not quite 1 kilogramme,
or about 1 pound to 2 feet of sustaining surface, which proved to be entirely
too great a weight for the power of support. When placed upon the
whirling-table, it showed a tendency to soar at a speed of about ten miles an
hour, but its own propellers were utterly insufficient to sustain it.
In this attempt, which was useful only in showing how much was to be
learned of practical conditions, the primary difficulty lay in making the
model light enough and sufficiently strong to support its power. This
difficulty continued to be fundamental through every later form; but besides
this, the adjustment of the center of gravity to the center of pressure of the
wings, the disposition of the wings themselves, the size of the propellers,
the inclination and number of their blades, and a great number of other
details, presented themselves for examination. [p012] Even in the first model,
the difficulty of launching the machine or giving it the necessary
preliminary impulse was disclosed—a difficulty which may perhaps not
appear serious to the reader, but which in fact required years of experiment
to remove.
By June, 1887 two other models, embodying various changes that had
suggested themselves, had been constructed. Each of these had a single
propeller (one an 18 12 -inch propeller with eight adjustable blades, the other
a 24-inch propeller with four adjustable blades) and was sustained by two
pairs of curved wings 4 feet 7 inches long. It is, however, unnecessary to
dwell further on these details, since these models also proved altogether too
heavy in relation to their power, and neither of them ever made an actual
flight.
At this period my time became so fully occupied with the experiments in
aerodynamics (which are not here in question) that during the next two
years little additional was done in making direct investigations in flight.
Page 35
In June, 1889, however, new rubber-driven models were made in which
the wooden frames were replaced by tubes of light metal, which, however,
were still too heavy, and these subsequently by tubes of paper covered with
shellac, which proved to be the lightest and best material in proportion to its
strength that had been found. The twisted rubber was carried within these
tubes, which were made just strong enough to withstand the end-strain it
produced. The front end of the rubber being made fast to an extremity of the
tube, the other end was attached directly to the shaft of the propeller, which
in the early models was still supplied with four blades.
A detailed description of one of these early models, No. 26, shown in
Plates 1 and 4, follows:
In each of the two tubes of paper, stiffened with shellac, which form a
part of the framing, is mounted a hank of twisted rubber, which connects
with a propeller at the rear. There are two pairs of wings, superposed and
inclined at an angle, the one above, the other below the frame. A light stem
connected with the frame bears a triangular Pénaud tail and rudder.
Length of model 105 cm.
Spread of wings 83
Width of upper wings 14
Width of lower wings 19
Diameter of propeller 29
Area of upper wings 1134 sq. cm.
Area of lower wings 1548
Area of tail 144
Weight of wings 51 grammes
Weight of tail 7
Weight of frame 38
Weight of wheels 20
Weight of rubber (.09 pound) 40
Total weight 156
No. of turns of rubber 100
Time of running down 8 seconds
Horse-power from preceding data 0.001 HP
[p013]
The aerodromes made at this time were too heavy, as well as too large, to
be easily launched by hand, and it was not until 1891 that the first one was
constructed light enough to actually fly. This first flight was obtained from
the wooden frames were replaced by tubes of light metal, which, however,
were still too heavy, and these subsequently by tubes of paper covered with
shellac, which proved to be the lightest and best material in proportion to its
strength that had been found. The twisted rubber was carried within these
tubes, which were made just strong enough to withstand the end-strain it
produced. The front end of the rubber being made fast to an extremity of the
tube, the other end was attached directly to the shaft of the propeller, which
in the early models was still supplied with four blades.
A detailed description of one of these early models, No. 26, shown in
Plates 1 and 4, follows:
In each of the two tubes of paper, stiffened with shellac, which form a
part of the framing, is mounted a hank of twisted rubber, which connects
with a propeller at the rear. There are two pairs of wings, superposed and
inclined at an angle, the one above, the other below the frame. A light stem
connected with the frame bears a triangular Pénaud tail and rudder.
Length of model 105 cm.
Spread of wings 83
Width of upper wings 14
Width of lower wings 19
Diameter of propeller 29
Area of upper wings 1134 sq. cm.
Area of lower wings 1548
Area of tail 144
Weight of wings 51 grammes
Weight of tail 7
Weight of frame 38
Weight of wheels 20
Weight of rubber (.09 pound) 40
Total weight 156
No. of turns of rubber 100
Time of running down 8 seconds
Horse-power from preceding data 0.001 HP
[p013]
The aerodromes made at this time were too heavy, as well as too large, to
be easily launched by hand, and it was not until 1891 that the first one was
constructed light enough to actually fly. This first flight was obtained from
Page 36
the north window of the dome of the Allegheny Observatory, on March 28,
1891, and imperfect as it was, served to show that the proper balancing of
the aerodrome which would bring the center of gravity under the center of
pressure, so as to give a horizontal flight, had yet to be obtained.
From this time on until 1893, experiments continued to be made with
rubber-driven models, of which, as has been stated, nearly 40 were
constructed, some with two propellers, some with one; some with one
propeller in front and one behind; some with plane, some with curved,
wings; some with single, some with superposed, wings; some with two
pairs of wings, one preceding and one following; some with the Pénaud tail;
and some with other forms. A few of these early forms are indicated on the
accompanying Plates 1 to 4, but it does not seem necessary to go into the
details of their construction.
No. 11 with which an early flight was made, closely resembles the
Pénaud model.
No. 13 has two propellers, one in front and one behind, with a single
wing.
No. 14 has two propellers, nearly side by side, but one slightly in
advance, with a single wing and a flat horizontal tail.
No. 15 has one leading propeller and two broad wings, placed one behind
the other.
No. 30 has the propeller shafts at an angle, and one pair of wings.
No. 31 has the propeller shafts at an angle, and two pairs of wings
superposed.
The wings in general were flat, but in some cases curved. The rubber was
usually wound to about 100 turns, and trouble continually arose from its
“kinking” and unequal unwinding, which often caused most erratic flights.
It is sufficient to say of these that, rude as they were, much was learned
from them about the condition of the machines in free air, which could
never be learned from the whirling-table or other constrained flight.
The advantages and also the dangers of curved wings as compared with
plane ones, were shown, and the general disposition which would secure an
even balance, was ascertained; but all this was done with extreme difficulty,
1891, and imperfect as it was, served to show that the proper balancing of
the aerodrome which would bring the center of gravity under the center of
pressure, so as to give a horizontal flight, had yet to be obtained.
From this time on until 1893, experiments continued to be made with
rubber-driven models, of which, as has been stated, nearly 40 were
constructed, some with two propellers, some with one; some with one
propeller in front and one behind; some with plane, some with curved,
wings; some with single, some with superposed, wings; some with two
pairs of wings, one preceding and one following; some with the Pénaud tail;
and some with other forms. A few of these early forms are indicated on the
accompanying Plates 1 to 4, but it does not seem necessary to go into the
details of their construction.
No. 11 with which an early flight was made, closely resembles the
Pénaud model.
No. 13 has two propellers, one in front and one behind, with a single
wing.
No. 14 has two propellers, nearly side by side, but one slightly in
advance, with a single wing and a flat horizontal tail.
No. 15 has one leading propeller and two broad wings, placed one behind
the other.
No. 30 has the propeller shafts at an angle, and one pair of wings.
No. 31 has the propeller shafts at an angle, and two pairs of wings
superposed.
The wings in general were flat, but in some cases curved. The rubber was
usually wound to about 100 turns, and trouble continually arose from its
“kinking” and unequal unwinding, which often caused most erratic flights.
It is sufficient to say of these that, rude as they were, much was learned
from them about the condition of the machines in free air, which could
never be learned from the whirling-table or other constrained flight.
The advantages and also the dangers of curved wings as compared with
plane ones, were shown, and the general disposition which would secure an
even balance, was ascertained; but all this was done with extreme difficulty,
Page 37
since the brief flights were full of anomalies, arising from the imperfect
conditions of observation. For instance, the motor power was apparently
exhausted more rapidly when the propellers were allowed to turn with the
model at rest, than when it was in motion, though in theory, in the latter
case more power would seem to be expended and a greater speed of
revolution obtained in a given time. The longest flights obtainable did not
exceed 6 or 8 seconds in time, nor 80 to 100 feet in distance, and were not
only so brief, but, owing to the spasmodic action of the rubber and other
causes, so irregular, that it was extremely difficult to obtain even the
imperfect results which were actually deduced from them. [p014]
A BBREVIATIONS AND S YMBOLS E MPLOYED
The following rules and symbols were adopted for determining the
relative position of points on the aerodrome, some of them during 1891, and
some of them since. All are given here for convenience of reference, though
their chief application is to the larger steam aerodromes described later.
Those which immediately follow were meant to give some of the notation
of descriptive geometry in untechnical language for the use of the workmen
employed. Let X, Y and Z be three lines at right angles to each other, and
passing through the same point in space, O, lying at any convenient
distance above the floor of the work-shop. The line X lies North and South;
the line Y lies East and West, and the line Z points to the zenith. Now place
the aerodrome on the floor so that its principal axis lies horizontally in the
plane XZ, with its head pointing North, and in such a position that a line
passing through the center of the propellers shall coincide with the line Y.
conditions of observation. For instance, the motor power was apparently
exhausted more rapidly when the propellers were allowed to turn with the
model at rest, than when it was in motion, though in theory, in the latter
case more power would seem to be expended and a greater speed of
revolution obtained in a given time. The longest flights obtainable did not
exceed 6 or 8 seconds in time, nor 80 to 100 feet in distance, and were not
only so brief, but, owing to the spasmodic action of the rubber and other
causes, so irregular, that it was extremely difficult to obtain even the
imperfect results which were actually deduced from them. [p014]
A BBREVIATIONS AND S YMBOLS E MPLOYED
The following rules and symbols were adopted for determining the
relative position of points on the aerodrome, some of them during 1891, and
some of them since. All are given here for convenience of reference, though
their chief application is to the larger steam aerodromes described later.
Those which immediately follow were meant to give some of the notation
of descriptive geometry in untechnical language for the use of the workmen
employed. Let X, Y and Z be three lines at right angles to each other, and
passing through the same point in space, O, lying at any convenient
distance above the floor of the work-shop. The line X lies North and South;
the line Y lies East and West, and the line Z points to the zenith. Now place
the aerodrome on the floor so that its principal axis lies horizontally in the
plane XZ, with its head pointing North, and in such a position that a line
passing through the center of the propellers shall coincide with the line Y.
Page 38
FIG. 2. Diagram showing mensural coordinates.
When measurements are made on or parallel to the line X, the point of
intersection O will be marked 1500 centimetres, and distances toward the
South will be less than, and distances toward the North greater than 1500
centimetres.
When measurements are made on or parallel to the line Z, the point O
will be considered to be marked 2500 centimetres, and distances above will
be greater than, and distances below will be less than 2500 centimetres.
[p015]
Lastly, when measurements are made on or parallel to the line Y, the
point O will be marked 3500 centimetres, and distances toward the East will
be greater than, and distances toward the West will be less than 3500
centimetres. Measurements in these latter directions will be comparatively
When measurements are made on or parallel to the line X, the point of
intersection O will be marked 1500 centimetres, and distances toward the
South will be less than, and distances toward the North greater than 1500
centimetres.
When measurements are made on or parallel to the line Z, the point O
will be considered to be marked 2500 centimetres, and distances above will
be greater than, and distances below will be less than 2500 centimetres.
[p015]
Lastly, when measurements are made on or parallel to the line Y, the
point O will be marked 3500 centimetres, and distances toward the East will
be greater than, and distances toward the West will be less than 3500
centimetres. Measurements in these latter directions will be comparatively
Page 39
infrequent because the center of gravity and center of pressure both lie in
the plane XZ.
E XAMP L E
In the figure the point T in the tail, if 15 centimetres to the South of O,
would be graduated 1485 centimetres. A weight (W ) 25 centimetres below
the axis, would be graduated 2475 centimetres. A point 50 centimetres
above the axis would be graduated 2550 centimetres, etc.
CG represents the Center of Gravity of the aerodrome, or (with subscript
letters) of any specially designated part, or with reference to some indicated
condition.
CG 1 CG 2 represent the Center of Gravity as referred to the first, or
horizontal, and to the second, or vertical plane, respectively.
CP represents the Center of Pressure14 of the whole aerodrome, or (with
a subscript) of any specially designated part.
CF represents the Center of Figure of the aerodrome, or of any specially
designated part.
Subscripts:
“fw ” refers to the front wings.
“rw ” refers to the rear wings.
“r ” refers to a state of rest.
“m ” refers to a state of motion.
“1” refers to the plane XY.
“2” refers to the plane XZ.
“3” refers to the plane YZ.
“A ” represents the total area of the supporting surface; “a ” represents the
total area of the tail; HP represents the horse-power by Prony brake
measurement. “Horse-power by formula” is given by Maxim’s formula:15
rev. × diam. of propeller × pitch × thrust
HP = .
33,000
the plane XZ.
E XAMP L E
In the figure the point T in the tail, if 15 centimetres to the South of O,
would be graduated 1485 centimetres. A weight (W ) 25 centimetres below
the axis, would be graduated 2475 centimetres. A point 50 centimetres
above the axis would be graduated 2550 centimetres, etc.
CG represents the Center of Gravity of the aerodrome, or (with subscript
letters) of any specially designated part, or with reference to some indicated
condition.
CG 1 CG 2 represent the Center of Gravity as referred to the first, or
horizontal, and to the second, or vertical plane, respectively.
CP represents the Center of Pressure14 of the whole aerodrome, or (with
a subscript) of any specially designated part.
CF represents the Center of Figure of the aerodrome, or of any specially
designated part.
Subscripts:
“fw ” refers to the front wings.
“rw ” refers to the rear wings.
“r ” refers to a state of rest.
“m ” refers to a state of motion.
“1” refers to the plane XY.
“2” refers to the plane XZ.
“3” refers to the plane YZ.
“A ” represents the total area of the supporting surface; “a ” represents the
total area of the tail; HP represents the horse-power by Prony brake
measurement. “Horse-power by formula” is given by Maxim’s formula:15
rev. × diam. of propeller × pitch × thrust
HP = .
33,000
Page 40
(This formula was not in use at the time of the rubber-motor experiments,
for which the thrust was not taken. It appears to assume the conditions
where the screws from a fixed position move a mass of still air, are the
same as those of free flight. Its results, however, are in better agreement
with experiment than might be anticipated.)
“Flying-weight” means everything borne in actual flight, including fuel
and water. [p016]
E XPERIMENTS W ITH A ERODROMES N OS. 30 AND 31.
Remembering that the principal object of all these experiments is to be
able to predict that setting of the wings and tail with reference to the center
of gravity which will secure horizontal flight, we must understand that in
the following tables (see No. 30) the figures CPm = 1516.5 cm. mean a
prediction that the center of pressure of the sustaining surfaces in motion
(CPm) is to be found in a certain position 1516.5; that is, 16.5 cm. in
advance of the line joining the propeller shafts. This prediction has been
made by means of previous calculation joined with previous experimental
adjustment. We know in a rough way where the CP will fall on the wings
when they are exposed independently if flat, and at a certain angle, and
where it will fall on the tail. From these, we can find where the resulting CP
of the whole sustaining surface will be.
It would seem that when we have obtained the center of gravity by a
simple experiment, we have only to slide the wings or tail forward and back
until the (calculated) center of pressure falls over this observed center of
gravity. But in the very act of so adjusting the wings and tail, the center of
gravity is itself altered, and the operation has to be several times repeated in
order to get the two values (the center of pressure and center of gravity) as
near each other as they are found in the above-mentioned table, our object
being to predict the position which will make the actual flight itself
horizontal. How far this result has been obtained, experiment in actual flight
alone can show, and from a comparison of the prediction with the results of
observation, we endeavor to improve the formula.
for which the thrust was not taken. It appears to assume the conditions
where the screws from a fixed position move a mass of still air, are the
same as those of free flight. Its results, however, are in better agreement
with experiment than might be anticipated.)
“Flying-weight” means everything borne in actual flight, including fuel
and water. [p016]
E XPERIMENTS W ITH A ERODROMES N OS. 30 AND 31.
Remembering that the principal object of all these experiments is to be
able to predict that setting of the wings and tail with reference to the center
of gravity which will secure horizontal flight, we must understand that in
the following tables (see No. 30) the figures CPm = 1516.5 cm. mean a
prediction that the center of pressure of the sustaining surfaces in motion
(CPm) is to be found in a certain position 1516.5; that is, 16.5 cm. in
advance of the line joining the propeller shafts. This prediction has been
made by means of previous calculation joined with previous experimental
adjustment. We know in a rough way where the CP will fall on the wings
when they are exposed independently if flat, and at a certain angle, and
where it will fall on the tail. From these, we can find where the resulting CP
of the whole sustaining surface will be.
It would seem that when we have obtained the center of gravity by a
simple experiment, we have only to slide the wings or tail forward and back
until the (calculated) center of pressure falls over this observed center of
gravity. But in the very act of so adjusting the wings and tail, the center of
gravity is itself altered, and the operation has to be several times repeated in
order to get the two values (the center of pressure and center of gravity) as
near each other as they are found in the above-mentioned table, our object
being to predict the position which will make the actual flight itself
horizontal. How far this result has been obtained, experiment in actual flight
alone can show, and from a comparison of the prediction with the results of
observation, we endeavor to improve the formula.
Page 41
The difficulties of these long-continued early experiments were enhanced
by the ever-present difficulty which continued through later ones, that it
was almost impossible to build the model light enough to enable it to fly,
and at the same time strong enough to withstand the strains which flight
imposed upon it. The models were broken up by their falls after a few
flights, and had to be continually renewed, while owing to the slightness of
their construction, the conditions of observation could not be exactly
repeated; and these flights themselves, as has already been stated, were so
brief in time (usually less than six seconds), so limited in extent (usually
less than twenty metres), and so wholly capricious and erratic, owing to the
nature of the rubber motor and other causes, that very many experiments
were insufficient to eliminate these causes of mal-observation.
It is not necessary to take the reader through many of them, but not to
pass over altogether a labor which was so great in proportion to the results,
but whose results, such as they were, were the foundation of all after
knowledge, I will, as illustrations, take from an almost unlimited mass of
such material the observations of November 20, 1891, which were
conducted with Model No. 30 with a single pair of wings, shown in Plate 1,
and with another one, No. 31, also shown [p018] in Plate 1, with superposed
wings, which was used for the purpose of comparison. S. P. Langley was
the observer, the place of observation the larger upper hall of the
Smithsonian building, at Washington, the time being taken by a stop-watch,
and the distance by a scale laid down upon the floor. The models were in
every case held by an assistant and launched by hand, being thrown off with
a slight initial velocity. In the case of No. 30, the preliminary calculation of
the position of the center of pressure had been made by the process already
described; the center of gravity, with reference to the horizontal plane, was
determined by simply suspending the whole by a cord.
by the ever-present difficulty which continued through later ones, that it
was almost impossible to build the model light enough to enable it to fly,
and at the same time strong enough to withstand the strains which flight
imposed upon it. The models were broken up by their falls after a few
flights, and had to be continually renewed, while owing to the slightness of
their construction, the conditions of observation could not be exactly
repeated; and these flights themselves, as has already been stated, were so
brief in time (usually less than six seconds), so limited in extent (usually
less than twenty metres), and so wholly capricious and erratic, owing to the
nature of the rubber motor and other causes, that very many experiments
were insufficient to eliminate these causes of mal-observation.
It is not necessary to take the reader through many of them, but not to
pass over altogether a labor which was so great in proportion to the results,
but whose results, such as they were, were the foundation of all after
knowledge, I will, as illustrations, take from an almost unlimited mass of
such material the observations of November 20, 1891, which were
conducted with Model No. 30 with a single pair of wings, shown in Plate 1,
and with another one, No. 31, also shown [p018] in Plate 1, with superposed
wings, which was used for the purpose of comparison. S. P. Langley was
the observer, the place of observation the larger upper hall of the
Smithsonian building, at Washington, the time being taken by a stop-watch,
and the distance by a scale laid down upon the floor. The models were in
every case held by an assistant and launched by hand, being thrown off with
a slight initial velocity. In the case of No. 30, the preliminary calculation of
the position of the center of pressure had been made by the process already
described; the center of gravity, with reference to the horizontal plane, was
determined by simply suspending the whole by a cord.
Page 42
PL. 1. RUBBER-MOTOR MODEL AERODROMES NOS. 11, 13, 14, 15, 26, 30, 31 ◊
Page 43
PL. 2. RUBBER-MOTOR MODEL AERODROMES NOS. 11, 13, 14 ◊
Page 44
PL. 3. RUBBER-MOTOR MODEL AERODROMES NOS. 15, 24 ◊
Page 45
PL. 4. RUBBER-MOTOR MODEL AERODROME NO. 26 ◊
Page 46
OBS E RVAT I ON OF NOVE MBE R 2 0 , 18 9 1.
OBSERVER , S.P.L. LOCALITY , UPPER HALL , SMITHSONIAN BUILDING .
No. 30. No. 31.
Single wings. Superposed wings.
CPm 1516.5 cm.
CG1 1515 1517 cm.
CFw 1528 cm.
Length (without fender) 120 cm. = 3.94 ft. 120 cm. = 3.94 ft.
Width over wing tips 120 cm. = 3.94 ft. 120 cm. = 3.94 ft.
Weight of rubber (72
grammes in each tube) 144 gr. = 0.32 lbs. 144 gr. = 0.32 lbs.
Total flying weight
(including tail) 432 gr. = 0.95 lbs. 506 gr. = 1.11 lbs.
Turns of rubber 30 30
Diameter of propellers 37 cm. = 1.21 ft. 37 cm. = 1.21 ft.
Width of propellers 7 cm. = 0.23 ft. 7 cm. = 0.23 ft.
Pitch of propellers 50 cm. = 1.64 ft. 50 cm. = 1.64 ft.
Area of wings (each 992 1984 sq.cm.= 2.13 sq.ft. Each pair 1984 sq.cm.= 2.13 sq.ft. Total
sq.cm.) 3968 sq.cm.= 4.26 sq.ft.
Area of tail 373 sq.cm.= 0.40 sq.ft. 373 sq.cm.= 0.40 sq.ft.
Area of wings and tail in No. 30, 2357 sq. cm. = 2.53 sq. ft. 2.53 sq. ft. ÷ .95 = 2.7.
Therefore, there are 2.7 or nearly 3 square feet of sustaining area to the pound.
OBSERVER , S.P.L. LOCALITY , UPPER HALL , SMITHSONIAN BUILDING .
No. 30. No. 31.
Single wings. Superposed wings.
CPm 1516.5 cm.
CG1 1515 1517 cm.
CFw 1528 cm.
Length (without fender) 120 cm. = 3.94 ft. 120 cm. = 3.94 ft.
Width over wing tips 120 cm. = 3.94 ft. 120 cm. = 3.94 ft.
Weight of rubber (72
grammes in each tube) 144 gr. = 0.32 lbs. 144 gr. = 0.32 lbs.
Total flying weight
(including tail) 432 gr. = 0.95 lbs. 506 gr. = 1.11 lbs.
Turns of rubber 30 30
Diameter of propellers 37 cm. = 1.21 ft. 37 cm. = 1.21 ft.
Width of propellers 7 cm. = 0.23 ft. 7 cm. = 0.23 ft.
Pitch of propellers 50 cm. = 1.64 ft. 50 cm. = 1.64 ft.
Area of wings (each 992 1984 sq.cm.= 2.13 sq.ft. Each pair 1984 sq.cm.= 2.13 sq.ft. Total
sq.cm.) 3968 sq.cm.= 4.26 sq.ft.
Area of tail 373 sq.cm.= 0.40 sq.ft. 373 sq.cm.= 0.40 sq.ft.
Area of wings and tail in No. 30, 2357 sq. cm. = 2.53 sq. ft. 2.53 sq. ft. ÷ .95 = 2.7.
Therefore, there are 2.7 or nearly 3 square feet of sustaining area to the pound.
Page 47
Nov. 20, 1891.
Flight. Aerodrome. Results.
1 No. 30 With 30 turns of the rubber, flew low through 10 metres.
2 No. 30 Flew heavily through 12 metres.
3 No. 31 Flew high and turned to left; distance not noted.
4 No. 31 The right wing having been weighted (to depress it and correct the
tendency to turn to the left), model flew high, but the rubber ran down
when it had obtained a flight of 10 metres.
5 No. 31 The wings were moved backward until the CP stood at 1493. The model
still turned to the left; flight lasted three and a-half seconds; distance
not noted.
6 No. 31 Vertical tail was adjusted so as to further increase the tendency to go to
the right. In spite of all this, the model turned sharply to the left, flying
with a nearly horizontal motion; time of flight not noted; distance not
noted.
7 No. 30 Straight horizontal flight; time three and three-fifth seconds, when
rubber ran down; distance 13 metres.
8 No. 30 Straight flight as before; time two and four-fifth seconds; distance 13
metres.
9 No. 30 With a curved wing in the same position as the flat wing had previously
occupied, model flew up and struck the ceiling (nearly 30 feet high),
turning to right, with a flight whose curtate length was 10 metres.
10 No. 30 Wing having been carried back 5 centimetres, model still flew up, but
not so high, and still turned to the right.
11 No. 30 Wings carried back 5 centimetres more; model still flew high; time two
and two-fifths seconds; distance 13 metres.
12 No. 30 Wings carried back 4 centimetres more; model still flew high during a
flight of 13 metres.
The observations now ceased, owing to the breaking up of the model.
The objects of these experiments, as of every other, were to find the
practical conditions of equilibrium and of horizontal flight, and to compare
the calculated with the observed positions of the center of pressure. They
enable us to make a comparison of the performances given by earlier ones
with a light rubber motor, with the relatively heavy motors used to-day, as
well as a comparison of single flat, single curved, and superposed flat
wings.
The average time of the running down of the rubber in flight was
something like three seconds, while the average time of its running down
when standing still was but one and a half seconds. It might have been
Flight. Aerodrome. Results.
1 No. 30 With 30 turns of the rubber, flew low through 10 metres.
2 No. 30 Flew heavily through 12 metres.
3 No. 31 Flew high and turned to left; distance not noted.
4 No. 31 The right wing having been weighted (to depress it and correct the
tendency to turn to the left), model flew high, but the rubber ran down
when it had obtained a flight of 10 metres.
5 No. 31 The wings were moved backward until the CP stood at 1493. The model
still turned to the left; flight lasted three and a-half seconds; distance
not noted.
6 No. 31 Vertical tail was adjusted so as to further increase the tendency to go to
the right. In spite of all this, the model turned sharply to the left, flying
with a nearly horizontal motion; time of flight not noted; distance not
noted.
7 No. 30 Straight horizontal flight; time three and three-fifth seconds, when
rubber ran down; distance 13 metres.
8 No. 30 Straight flight as before; time two and four-fifth seconds; distance 13
metres.
9 No. 30 With a curved wing in the same position as the flat wing had previously
occupied, model flew up and struck the ceiling (nearly 30 feet high),
turning to right, with a flight whose curtate length was 10 metres.
10 No. 30 Wing having been carried back 5 centimetres, model still flew up, but
not so high, and still turned to the right.
11 No. 30 Wings carried back 5 centimetres more; model still flew high; time two
and two-fifths seconds; distance 13 metres.
12 No. 30 Wings carried back 4 centimetres more; model still flew high during a
flight of 13 metres.
The observations now ceased, owing to the breaking up of the model.
The objects of these experiments, as of every other, were to find the
practical conditions of equilibrium and of horizontal flight, and to compare
the calculated with the observed positions of the center of pressure. They
enable us to make a comparison of the performances given by earlier ones
with a light rubber motor, with the relatively heavy motors used to-day, as
well as a comparison of single flat, single curved, and superposed flat
wings.
The average time of the running down of the rubber in flight was
something like three seconds, while the average time of its running down
when standing still was but one and a half seconds. It might have been
Page 48
expected from theory that it would take longer to run down when stationary,
than in flight, and this was one of the many anomalies observed, whose
explanation was found later in the inevitable defects of such apparatus.
The immediate inferences from the day’s work were:
1. That the calculated position of the CP at rest, as related to the CG, is
trustworthy only in the case of the plane wing.
2. The formula altogether failed with the curved wing, for which the CP
had to be carried indefinitely further backward.
On comparing the previous flights of November 14, with these, it seems
that with the old rubber motor of 35 grammes and 50 turns, the single wing,
either plane or curved, is altogether inferior to the double wing; while with
the increased motor power of this day, the single wing, whether plane or
curved, seems to be as good as the double wing. It also seems that the
curved wing was rather more efficient than the plane one.
The weight of the rubber in each tube was 72 grammes, or 0.16 pounds;
mean speed of flight in horizontal distance 4 12 metres (about 15 feet) per
second.16
From experiments already referred to, there were found available 300
foot-pounds of energy in a pound of rubber as employed, and in 0.16 of a
48
pound, 48 foot-pounds of energy were used; 33,000 or 0.00145 = the horse-
power exerted in [p019] one minute, but as the power was in fact expended in
1/20 of that time we have 20 × 0.00145 = 0.029; that is, during the brief
flight, about 0.03 of a horse-power was exerted, and this sustained a total
weight of only about a pound.
In comparing this flight with the ideal conditions of horizontal flight in
“Aerodynamics,” it will be remembered that this model’s flight was so
irregular and so far from horizontal, that in one case it flew up and struck
the lofty ceiling. The angle with the horizon is, of course, so variable as to
be practically unknown, and therefore no direct comparison can be
instituted with the data given on page 107 of “Experiments in
Aerodynamics,” but we find from these that at the lowest speed there given
of about 35 feet per second, 0.03 of a horse-power exerted for three seconds
than in flight, and this was one of the many anomalies observed, whose
explanation was found later in the inevitable defects of such apparatus.
The immediate inferences from the day’s work were:
1. That the calculated position of the CP at rest, as related to the CG, is
trustworthy only in the case of the plane wing.
2. The formula altogether failed with the curved wing, for which the CP
had to be carried indefinitely further backward.
On comparing the previous flights of November 14, with these, it seems
that with the old rubber motor of 35 grammes and 50 turns, the single wing,
either plane or curved, is altogether inferior to the double wing; while with
the increased motor power of this day, the single wing, whether plane or
curved, seems to be as good as the double wing. It also seems that the
curved wing was rather more efficient than the plane one.
The weight of the rubber in each tube was 72 grammes, or 0.16 pounds;
mean speed of flight in horizontal distance 4 12 metres (about 15 feet) per
second.16
From experiments already referred to, there were found available 300
foot-pounds of energy in a pound of rubber as employed, and in 0.16 of a
48
pound, 48 foot-pounds of energy were used; 33,000 or 0.00145 = the horse-
power exerted in [p019] one minute, but as the power was in fact expended in
1/20 of that time we have 20 × 0.00145 = 0.029; that is, during the brief
flight, about 0.03 of a horse-power was exerted, and this sustained a total
weight of only about a pound.
In comparing this flight with the ideal conditions of horizontal flight in
“Aerodynamics,” it will be remembered that this model’s flight was so
irregular and so far from horizontal, that in one case it flew up and struck
the lofty ceiling. The angle with the horizon is, of course, so variable as to
be practically unknown, and therefore no direct comparison can be
instituted with the data given on page 107 of “Experiments in
Aerodynamics,” but we find from these that at the lowest speed there given
of about 35 feet per second, 0.03 of a horse-power exerted for three seconds
Page 49
would carry nearly one pound through a distance of somewhat over 100 feet
in horizontal flight.
The number of turns of the propellers multiplied by the pitch corresponds
to a flight of about 16 metres, while the mean actual flight was about 12. It
is probable, however, that there was really more slip than this part of the
observation would indicate. It was also observed that there seemed to be
very little additional compensatory gain in the steering of No. 30 for the
weight of the long rudder-tail it carried. It may be remarked that in
subsequent observations the superiority of the curved wing in lifting power
was confirmed, though it was found more liable to accident than the flatter
one, tending to turn the model over unless it was very carefully adjusted.
It may also be observed that these and subsequent observations show, as
might have been anticipated, that as the motor power increased, the
necessary wing surface diminished, but that it was in general an easier and
more efficient employment of power to carry a surface of four feet
sustaining area to the pound than one of three, while one of two feet to the
pound was nearly the limit that could be used with the rubber motor.17
It may be remarked that the flights this day, reckoned in horizontal
distance, were exceptionally short, but that the best flights at other times
obtained with these models (30 and 31) did not exceed 25 metres. Such
observations were continued in hundreds of trials, without any much more
conclusive results. [p020]
The final results, then, of the observations with rubber-driven models
(which were commenced as early as 1887, continued actively through the
greater portion of the year 1891 and resumed, as will be seen later, even as
late as 1895), were not such as to give information proportioned to their
trouble and cost, and it was decided to commence experiments with a
steam-driven aerodrome on a large scale.
in horizontal flight.
The number of turns of the propellers multiplied by the pitch corresponds
to a flight of about 16 metres, while the mean actual flight was about 12. It
is probable, however, that there was really more slip than this part of the
observation would indicate. It was also observed that there seemed to be
very little additional compensatory gain in the steering of No. 30 for the
weight of the long rudder-tail it carried. It may be remarked that in
subsequent observations the superiority of the curved wing in lifting power
was confirmed, though it was found more liable to accident than the flatter
one, tending to turn the model over unless it was very carefully adjusted.
It may also be observed that these and subsequent observations show, as
might have been anticipated, that as the motor power increased, the
necessary wing surface diminished, but that it was in general an easier and
more efficient employment of power to carry a surface of four feet
sustaining area to the pound than one of three, while one of two feet to the
pound was nearly the limit that could be used with the rubber motor.17
It may be remarked that the flights this day, reckoned in horizontal
distance, were exceptionally short, but that the best flights at other times
obtained with these models (30 and 31) did not exceed 25 metres. Such
observations were continued in hundreds of trials, without any much more
conclusive results. [p020]
The final results, then, of the observations with rubber-driven models
(which were commenced as early as 1887, continued actively through the
greater portion of the year 1891 and resumed, as will be seen later, even as
late as 1895), were not such as to give information proportioned to their
trouble and cost, and it was decided to commence experiments with a
steam-driven aerodrome on a large scale.
Page 50
[p021] ◊
CHAPTER III
AVAILABLE MOTORS
In the introductory chapter to “Experiments in Aerodynamics,” it was
asserted that
“These researches have led to the result that mechanical sustentation of heavy bodies in the air,
combined with very great speeds, is not only possible, but within the reach of mechanical means
we actually possess.”
It was, however, necessary to make a proper selection in order to secure
that source of power which is best adapted to the requirements of
mechanical flight. Pénaud had used india rubber as the cheapest and at the
same time the most available motor for the toys with which he was
experimenting, but when models were constructed that were heavier than
anything made prior to 1887, it appeared, after the exhaustive trials with
rubber referred to in the preceding chapter, that something which could give
longer and steadier flights must be used as a motor, even for the preliminary
trials, and the construction of the large steam-driven model known as No. 0,
and elsewhere described, was begun. Even before the completion of this,
the probability of its failure grew so strong that experiments were
commenced with other motors, which it was hoped might be consistent with
a lighter construction.
These experiments which commenced in the spring of 1892 and
continued for nearly a twelvemonth, were made upon the use of compressed
air, carbonic-acid gas, electricity in primary and storage batteries, and
numerous other contrivances, with the result that the steam engine was
finally returned to, as being the only one that gave any promise of
immediate success in supporting a machine which would teach the
conditions of flight by actual trial, though it may be added that the gas
engine which was not tried at this time on account of engineering
difficulties, was regarded from the first as being the best in theory and
likely to be ultimately resorted to. All others were fundamentally too heavy,
and weight was always the greatest enemy.
CHAPTER III
AVAILABLE MOTORS
In the introductory chapter to “Experiments in Aerodynamics,” it was
asserted that
“These researches have led to the result that mechanical sustentation of heavy bodies in the air,
combined with very great speeds, is not only possible, but within the reach of mechanical means
we actually possess.”
It was, however, necessary to make a proper selection in order to secure
that source of power which is best adapted to the requirements of
mechanical flight. Pénaud had used india rubber as the cheapest and at the
same time the most available motor for the toys with which he was
experimenting, but when models were constructed that were heavier than
anything made prior to 1887, it appeared, after the exhaustive trials with
rubber referred to in the preceding chapter, that something which could give
longer and steadier flights must be used as a motor, even for the preliminary
trials, and the construction of the large steam-driven model known as No. 0,
and elsewhere described, was begun. Even before the completion of this,
the probability of its failure grew so strong that experiments were
commenced with other motors, which it was hoped might be consistent with
a lighter construction.
These experiments which commenced in the spring of 1892 and
continued for nearly a twelvemonth, were made upon the use of compressed
air, carbonic-acid gas, electricity in primary and storage batteries, and
numerous other contrivances, with the result that the steam engine was
finally returned to, as being the only one that gave any promise of
immediate success in supporting a machine which would teach the
conditions of flight by actual trial, though it may be added that the gas
engine which was not tried at this time on account of engineering
difficulties, was regarded from the first as being the best in theory and
likely to be ultimately resorted to. All others were fundamentally too heavy,
and weight was always the greatest enemy.
Page 51
It is the purpose of this chapter to pass in brief review the work that was
done and the amount of energy that was obtained with these several types of
motors, as well as the obstacles which they presented to practical
application upon working aerodromes.
I NDIA R UBBER
India rubber is the source of power to which the designer of a working
model naturally turns, where it is desirable that it shall be, above all, light
and free from the necessity of using complicated mechanism. Rubber
motors were, [p022] therefore, used on all of the earlier models, and served
as the basis of calculations made to determine the amount of power that
would be required to propel aerodromes with other sources of energy.
Some of the disadvantages inherent in the use of rubber are at once
apparent, such as the limited time during which its action is available, the
small total amount of power, and the variability in the amount of power put
forth in a unit of time between the moment of release and the exhaustion of
the power. In addition, serious, though less obvious difficulties, present
themselves in practice.
There are two ways in which rubber can be used; one by twisting a hank
of strands, and, while one end is held fast, allowing the other to revolve; the
other, by a direct longitudinal stretching of the rubber, one end being held
fast and the other attached to the moving parts of the mechanism. The
former method was adopted by Pénaud, and was also used in all of my early
constructions, but while it is most convenient and simple in its (theoretical)
application, it has, in addition to the above drawbacks, that of knotting or
kinking, when wound too many turns, in such a way as to cause friction on
any containing tube not made impracticably large, and also that of
unwinding so irregularly as to make the result of one experiment useless for
comparison with another.
In 1895, some experiments were made in which the latter method was
used, but this was found to involve an almost impracticable weight, because
of the frame (which must be strong enough to withstand the end pull of the
done and the amount of energy that was obtained with these several types of
motors, as well as the obstacles which they presented to practical
application upon working aerodromes.
I NDIA R UBBER
India rubber is the source of power to which the designer of a working
model naturally turns, where it is desirable that it shall be, above all, light
and free from the necessity of using complicated mechanism. Rubber
motors were, [p022] therefore, used on all of the earlier models, and served
as the basis of calculations made to determine the amount of power that
would be required to propel aerodromes with other sources of energy.
Some of the disadvantages inherent in the use of rubber are at once
apparent, such as the limited time during which its action is available, the
small total amount of power, and the variability in the amount of power put
forth in a unit of time between the moment of release and the exhaustion of
the power. In addition, serious, though less obvious difficulties, present
themselves in practice.
There are two ways in which rubber can be used; one by twisting a hank
of strands, and, while one end is held fast, allowing the other to revolve; the
other, by a direct longitudinal stretching of the rubber, one end being held
fast and the other attached to the moving parts of the mechanism. The
former method was adopted by Pénaud, and was also used in all of my early
constructions, but while it is most convenient and simple in its (theoretical)
application, it has, in addition to the above drawbacks, that of knotting or
kinking, when wound too many turns, in such a way as to cause friction on
any containing tube not made impracticably large, and also that of
unwinding so irregularly as to make the result of one experiment useless for
comparison with another.
In 1895, some experiments were made in which the latter method was
used, but this was found to involve an almost impracticable weight, because
of the frame (which must be strong enough to withstand the end pull of the
Page 52
rubber) and the mechanism needed to convert the pull into a movement of
rotation.
As the power put forth in a unit of time varies, so there is a
corresponding variation according to the original tension to which the
rubber is subjected. Thus in some experiments made in 1889 with a six-
bladed propeller 18.8 inches in diameter, driven by a rubber spring 1.3
inches wide, 0.12 inch thick and 3 feet long, doubled, and weighing 0.38
pound, the following results were obtained:
Number of twists of rubber 50 75 100
Time required to run down 7 sec. 10 sec. 12 sec.
Foot-pounds developed 37.5 63.0 124.6
Foot-pounds developed per min. 321.4 378.0 623.0
Horse-power developed 0.0097 0.0115 0.0189
Thus we see that, with twice the number of turns, more than three times the
amount of work was done and almost twice the amount of power
developed, giving as a maximum for this particular instance 328 foot-
pounds per pound of rubber.
The usual method of employing the twisted rubber was to use a number
of fine strands formed into a hank looped at each end. One of these hanks,
consisting of 162 single or 81 double strands of rubber, and weighing 73
grammes, when given 51 turns developed 55 foot-pounds of work, which
was put out in 4 seconds. This corresponds to 0.01 horse-power per minute
for one pound of rubber. [p023]
The results of a large number of tests show that one pound of twisted
rubber can put forth from 450 to 500 or more foot-pounds of work, but at
the cost of an overstrain, and that a safe working factor can hardly be taken
at higher than 300 foot-pounds, if we are to avoid the “fatigue” of the
rubber, which otherwise becomes as marked as that of a human muscle.
While twisting is an exceedingly convenient form of application of the
resilience of rubber to the turning of propelling wheels, the direct stretch is,
as has been remarked, much more efficient in foot-pounds of energy
developed by the same weight of rubber. It was found that rubber could not,
without undue “fatigue,” be stretched to more than four and a half times its
rotation.
As the power put forth in a unit of time varies, so there is a
corresponding variation according to the original tension to which the
rubber is subjected. Thus in some experiments made in 1889 with a six-
bladed propeller 18.8 inches in diameter, driven by a rubber spring 1.3
inches wide, 0.12 inch thick and 3 feet long, doubled, and weighing 0.38
pound, the following results were obtained:
Number of twists of rubber 50 75 100
Time required to run down 7 sec. 10 sec. 12 sec.
Foot-pounds developed 37.5 63.0 124.6
Foot-pounds developed per min. 321.4 378.0 623.0
Horse-power developed 0.0097 0.0115 0.0189
Thus we see that, with twice the number of turns, more than three times the
amount of work was done and almost twice the amount of power
developed, giving as a maximum for this particular instance 328 foot-
pounds per pound of rubber.
The usual method of employing the twisted rubber was to use a number
of fine strands formed into a hank looped at each end. One of these hanks,
consisting of 162 single or 81 double strands of rubber, and weighing 73
grammes, when given 51 turns developed 55 foot-pounds of work, which
was put out in 4 seconds. This corresponds to 0.01 horse-power per minute
for one pound of rubber. [p023]
The results of a large number of tests show that one pound of twisted
rubber can put forth from 450 to 500 or more foot-pounds of work, but at
the cost of an overstrain, and that a safe working factor can hardly be taken
at higher than 300 foot-pounds, if we are to avoid the “fatigue” of the
rubber, which otherwise becomes as marked as that of a human muscle.
While twisting is an exceedingly convenient form of application of the
resilience of rubber to the turning of propelling wheels, the direct stretch is,
as has been remarked, much more efficient in foot-pounds of energy
developed by the same weight of rubber. It was found that rubber could not,
without undue “fatigue,” be stretched to more than four and a half times its
Page 53
original length, though experiments were made to determine the amount of
work that a rubber band, weighing one pound, was capable of doing, the
stretching being carried to seven times its original length. The results varied
with the rubber used and the conditions of temperature under which the
experiments were tried, ranging from 1543 foot-pounds to 2600 foot-
pounds. The tests led to the conclusion that, for average working, one
pound of rubber so stretched, is capable of doing 2000 foot-pounds of work,
but, owing to the weight of the supporting frame and of the mechanism, this
result can be obtained only under conditions impracticable for a flying
machine. In the more practicable twisted form it furnishes, as has been said,
less than a fifth of that amount.
The conclusions reached from these experiments are:
1. The length of the unstretched rubber remaining the same, the
sustaining power will be directly proportional to the weight of rubber;
2. With a given weight of rubber, the end strain is inversely proportional
to the length of the unstretched rubber;
3. With a given weight of rubber, the work done is constant, whatever the
form; hence if we let w = the work in foot-pounds, g = the weight of the
rubber in pounds, and k = a constant taken at 2000 as given above, we have
w = kg = 2000 g foot-pounds.
This is for an extension of seven units of length, so that for a unit of
extension we would have approximately
w = 300 g foot-pounds
which for four units of extension corresponds very closely to the 1300 foot-
pounds which Pénaud claims to have obtained.
4. The end strain varies with the cross-section for a given unit of
extension.
These results can lead to but one conclusion; that for the development of
the same amount of power when that amount shall be 1 horse-power or
more, rubber weighs enormously more than a steam engine, besides being
less reliable [p024] for a sustained effort, and, therefore, cannot be used for
work that a rubber band, weighing one pound, was capable of doing, the
stretching being carried to seven times its original length. The results varied
with the rubber used and the conditions of temperature under which the
experiments were tried, ranging from 1543 foot-pounds to 2600 foot-
pounds. The tests led to the conclusion that, for average working, one
pound of rubber so stretched, is capable of doing 2000 foot-pounds of work,
but, owing to the weight of the supporting frame and of the mechanism, this
result can be obtained only under conditions impracticable for a flying
machine. In the more practicable twisted form it furnishes, as has been said,
less than a fifth of that amount.
The conclusions reached from these experiments are:
1. The length of the unstretched rubber remaining the same, the
sustaining power will be directly proportional to the weight of rubber;
2. With a given weight of rubber, the end strain is inversely proportional
to the length of the unstretched rubber;
3. With a given weight of rubber, the work done is constant, whatever the
form; hence if we let w = the work in foot-pounds, g = the weight of the
rubber in pounds, and k = a constant taken at 2000 as given above, we have
w = kg = 2000 g foot-pounds.
This is for an extension of seven units of length, so that for a unit of
extension we would have approximately
w = 300 g foot-pounds
which for four units of extension corresponds very closely to the 1300 foot-
pounds which Pénaud claims to have obtained.
4. The end strain varies with the cross-section for a given unit of
extension.
These results can lead to but one conclusion; that for the development of
the same amount of power when that amount shall be 1 horse-power or
more, rubber weighs enormously more than a steam engine, besides being
less reliable [p024] for a sustained effort, and, therefore, cannot be used for
Page 54
propelling aerodromes intended for a flight that is to be prolonged beyond a
few seconds.18
It may be desirable to present a tabular view of the theoretical energy of
available motors, which it will be noticed is a wholly different thing from
the results obtained in practice. Thus, we represent the weight of rubber
only, without regard to the weight of the frame required to hold it. In the
steam engine, we consider the theoretical efficiency per pound of fuel,
without regarding the enormous waste of weight in water in such small
engines as these, or the weight of the engine itself. We treat the hot-water
engine in like manner, and in regard to carbonic acid and compressed air,
we take no note of the weight of the containing vessel, or of the cylinders
and moving parts. In the same way we have the theoretical potency of
electricity in primary and storage batteries, without counting the weight of
the necessary electromotors; and of the inertia-engine without discussing
that of the mechanism needed to transmit its power.
Foot-pounds of energy in one pound of
Gasoline 15,625,280
Alcohol 9,721,806
Gunpowder 960,000
Hot water, under pressure of 100 atmospheres 383,712
Air, under pressure of 100 atmospheres, isothermal expansion 120,584
Liquid carbonic acid, at temperature of 30° and pressure of 100 atmospheres 78,800
Electric battery; short-lived, thin walled; chromic acid and platinum 75,000
Steel ring, 8 inches in diameter, at speed of 3000 turns per minute 19,000
Storage battery 17,560
Rubber, pulled 2,000
Rubber, twisted 300
It may be interesting to consider next, in even a roughly approximate
way, what may be expected from these various sources of energy in
practice.
S TEAM E NGINE
The steam engine on a small scale, and under the actual restrictions of the
model, must necessarily be extremely wasteful of power. If we suppose it to
realize 2 per cent of the theoretical energy contained in the fuel, we shall be
assuming more than was actually obtained. The energy of the fuel cannot be
few seconds.18
It may be desirable to present a tabular view of the theoretical energy of
available motors, which it will be noticed is a wholly different thing from
the results obtained in practice. Thus, we represent the weight of rubber
only, without regard to the weight of the frame required to hold it. In the
steam engine, we consider the theoretical efficiency per pound of fuel,
without regarding the enormous waste of weight in water in such small
engines as these, or the weight of the engine itself. We treat the hot-water
engine in like manner, and in regard to carbonic acid and compressed air,
we take no note of the weight of the containing vessel, or of the cylinders
and moving parts. In the same way we have the theoretical potency of
electricity in primary and storage batteries, without counting the weight of
the necessary electromotors; and of the inertia-engine without discussing
that of the mechanism needed to transmit its power.
Foot-pounds of energy in one pound of
Gasoline 15,625,280
Alcohol 9,721,806
Gunpowder 960,000
Hot water, under pressure of 100 atmospheres 383,712
Air, under pressure of 100 atmospheres, isothermal expansion 120,584
Liquid carbonic acid, at temperature of 30° and pressure of 100 atmospheres 78,800
Electric battery; short-lived, thin walled; chromic acid and platinum 75,000
Steel ring, 8 inches in diameter, at speed of 3000 turns per minute 19,000
Storage battery 17,560
Rubber, pulled 2,000
Rubber, twisted 300
It may be interesting to consider next, in even a roughly approximate
way, what may be expected from these various sources of energy in
practice.
S TEAM E NGINE
The steam engine on a small scale, and under the actual restrictions of the
model, must necessarily be extremely wasteful of power. If we suppose it to
realize 2 per cent of the theoretical energy contained in the fuel, we shall be
assuming more than was actually obtained. The energy of the fuel cannot be
Page 55
obtained at all, of course, without boiler and engine, whose weight, for the
purpose of the following calculation, must be added to that of the fuel; and
if we suppose the weight of the boilers, engines and water, for a single
minute’s flight, to be collectively ten pounds, we shall take an optimistic
view of what may be expected under ordinary conditions. We have in this
view 1/500 of the [p025] theoretical capacity possibly realizable under such
conditions, but if we take 1/1000 we shall probably be nearer the mark.
Even in this case we have, when using gasoline as fuel, 15,625 foot-pounds
per minute, or nearly 0.50 horse-power, as against .0091 horse-power in the
case of the rubber, so that even with this waste and with the weight of the
engines necessary for a single minute’s service, the unit weight of fuel
employed in the steam engine gives 55 times the result we get with rubber.
purpose of the following calculation, must be added to that of the fuel; and
if we suppose the weight of the boilers, engines and water, for a single
minute’s flight, to be collectively ten pounds, we shall take an optimistic
view of what may be expected under ordinary conditions. We have in this
view 1/500 of the [p025] theoretical capacity possibly realizable under such
conditions, but if we take 1/1000 we shall probably be nearer the mark.
Even in this case we have, when using gasoline as fuel, 15,625 foot-pounds
per minute, or nearly 0.50 horse-power, as against .0091 horse-power in the
case of the rubber, so that even with this waste and with the weight of the
engines necessary for a single minute’s service, the unit weight of fuel
employed in the steam engine gives 55 times the result we get with rubber.
Page 56
PL. 5. RUBBER-PULL MODEL AERODROME ◊
Page 57
PL. 6. RUBBER-PULL MODEL AERODROME ◊
Page 58
PL. 7. RUBBER-PULL MODEL AERODROME ◊
Page 59
PL. 8. RUBBER-PULL MODEL AERODROME ◊
Page 60
PL. 9. RUBBER-PULL MODEL AERODROME ◊
Page 61
With alcohol we have about 23 the result that is furnished by gasoline,
since nearly the same boiler and engine will be used in either case. Certain
difficulties which at first appeared to be attendant on the use of gasoline on
a small scale induced me to make the initial experiments with alcohol. This
was continued because of its convenience during a considerable time, but it
was finally displaced in favor of gasoline, not so much on account of the
superior theoretical efficiency of the latter, as for certain practical
advantages, such as its maintaining its flame while exposed to wind, and
like considerations.
G UNPOWDER
Although there are other explosives possessing a much greater energy in
proportion to their weight than gunpowder, this is the only one which could
be considered in relation to the present work, and the conclusion was finally
reached that it involved so great a weight in the containing apparatus and so
much experiment, that, although the simplicity of its action is in its favor
where crude means are necessary, experiments with it had better be deferred
until other things had been tried.
H OT - W ATER E NGINE
A great deal of attention was given to the hot-water engine, but it was
never put to practical use in the construction of an aerodrome, partly on
account of the necessary weight of a sufficiently strong containing vessel.
C OMPRESSED A IR
Compressed air, like the other possible sources of power, was
investigated, but calculations from well-authenticated data showed that this
system of propelling engines would probably be inadequate to sustain even
the models in long flights. As the chief difficulty lies in the weight, not of
the air, but of the containing vessel, numerous experiments were made in
the construction of one at once strong and light. The best result obtained
was with a steel tube 40 mm. in diameter, 428 mm. in length, closed at the
since nearly the same boiler and engine will be used in either case. Certain
difficulties which at first appeared to be attendant on the use of gasoline on
a small scale induced me to make the initial experiments with alcohol. This
was continued because of its convenience during a considerable time, but it
was finally displaced in favor of gasoline, not so much on account of the
superior theoretical efficiency of the latter, as for certain practical
advantages, such as its maintaining its flame while exposed to wind, and
like considerations.
G UNPOWDER
Although there are other explosives possessing a much greater energy in
proportion to their weight than gunpowder, this is the only one which could
be considered in relation to the present work, and the conclusion was finally
reached that it involved so great a weight in the containing apparatus and so
much experiment, that, although the simplicity of its action is in its favor
where crude means are necessary, experiments with it had better be deferred
until other things had been tried.
H OT - W ATER E NGINE
A great deal of attention was given to the hot-water engine, but it was
never put to practical use in the construction of an aerodrome, partly on
account of the necessary weight of a sufficiently strong containing vessel.
C OMPRESSED A IR
Compressed air, like the other possible sources of power, was
investigated, but calculations from well-authenticated data showed that this
system of propelling engines would probably be inadequate to sustain even
the models in long flights. As the chief difficulty lies in the weight, not of
the air, but of the containing vessel, numerous experiments were made in
the construction of one at once strong and light. The best result obtained
was with a steel tube 40 mm. in diameter, 428 mm. in length, closed at the
Page 62
ends by heads united by wires, which safely contained 538 cubic cm. of air
at an initial pressure of 100 atmospheres for a weight of 521 grammes. [p026]
If we suppose this to be used, by means of a proper reducing valve, at a
mean pressure of 100 pounds, for such an engine as that of Aerodrome No.
5, which takes 60 cubic cm. of air at each stroke, we find that (if we take no
account of the loss by expansion) we have 18,329 foot-pounds of energy
available, which on the engine described will give 302 revolutions of the
propellers.
There are such limits of weight, and the engines must be driven at such
high speeds, that the increased economy that might be obtained by re-
heating the air would be out of the question. The principal object in using it
would have been the avoidance of fire upon the aerodrome, and the
expansion of the unheated air would probably have caused trouble with
freezing, while the use of hot (i. e. superheated) water was impracticable.
So when, after a careful computation, it was found that, having regard to the
weight of the containing vessel, only enough compressed air could be
stored at 72 atmospheres and used at 4, to run a pair of engines with
cylinders 0.9 inch in diameter by 1.6 inches stroke, at a speed of 1200
revolutions per minute for 20 seconds, all further consideration of its
adaptation to the immediate purpose was definitely abandoned. This course,
however, was not taken until after a model aerodrome for using compressed
air had been designed and partially built. Then, after due consideration, it
was decided to make the test with carbonic-acid gas instead.
G AS
The gas engine possesses great theoretical advantages. At the time of
these experiments, the gas engine most available for the special purposes of
the models was one driven by air drawn through gasoline. As the builders
could not agree to reduce the weight of a one horse-power engine more than
one-half of the then usual model, and as the weight of the standard engine
was 470 pounds, it was obvious that to reduce this weight to the limit of
less than 3 pounds was impracticable under the existing conditions, and all
consideration of the use of gas was abandoned provisionally, although a
at an initial pressure of 100 atmospheres for a weight of 521 grammes. [p026]
If we suppose this to be used, by means of a proper reducing valve, at a
mean pressure of 100 pounds, for such an engine as that of Aerodrome No.
5, which takes 60 cubic cm. of air at each stroke, we find that (if we take no
account of the loss by expansion) we have 18,329 foot-pounds of energy
available, which on the engine described will give 302 revolutions of the
propellers.
There are such limits of weight, and the engines must be driven at such
high speeds, that the increased economy that might be obtained by re-
heating the air would be out of the question. The principal object in using it
would have been the avoidance of fire upon the aerodrome, and the
expansion of the unheated air would probably have caused trouble with
freezing, while the use of hot (i. e. superheated) water was impracticable.
So when, after a careful computation, it was found that, having regard to the
weight of the containing vessel, only enough compressed air could be
stored at 72 atmospheres and used at 4, to run a pair of engines with
cylinders 0.9 inch in diameter by 1.6 inches stroke, at a speed of 1200
revolutions per minute for 20 seconds, all further consideration of its
adaptation to the immediate purpose was definitely abandoned. This course,
however, was not taken until after a model aerodrome for using compressed
air had been designed and partially built. Then, after due consideration, it
was decided to make the test with carbonic-acid gas instead.
G AS
The gas engine possesses great theoretical advantages. At the time of
these experiments, the gas engine most available for the special purposes of
the models was one driven by air drawn through gasoline. As the builders
could not agree to reduce the weight of a one horse-power engine more than
one-half of the then usual model, and as the weight of the standard engine
was 470 pounds, it was obvious that to reduce this weight to the limit of
less than 3 pounds was impracticable under the existing conditions, and all
consideration of the use of gas was abandoned provisionally, although a
Page 63
gasoline engine of elementary simplicity was designed but never built. I
purposed, however, to return to this attractive form of power if I were ever
able to realize its theoretical advantages on the larger scale which would be
desirable.
E LECTRICITY
As it was not intended to build the model aerodromes for a long flight, it
was thought that the electric motor driven by a primary or storage battery
might possibly be utilized. It therefore occurred to me that a battery might
be constructed to give great power in proportion to its weight on condition
of being short-lived, and that in this form a battery might perhaps
advantageously take the place of the dangerous compressed-air tubes that
were at the time (1893) [p027] under consideration for driving the models. I
assumed that the longest flight of the model would be less than five
minutes. Any weight of battery, then, that the model carried in consumable
parts lasting beyond this five minutes would be lost, and hence it was
proposed to build a battery, the whole active life of which would be
comprised in this time, to actuate a motor or motors driving one or two
propellers.
According to Daniell, when energy is stored in secondary batteries, over
300,000 megergs per kilogramme of weight can be recovered and utilized if
freshly charged.
300,000 megergs = 0.696 horse-power for 1 min.
300,000 megergs = 0.139 horse-power for 5 min.
In a zinc and copper primary battery with sulphuric acid and water, one
kilogramme of zinc, oxidized, furnishes at least 1200 calories as against
8000 for one kilogramme of carbon, but it is stated that the zinc energy
comes in so much more utilizable a form that the zinc, weight for weight,
gives practically, that is in work, 40 per cent that of carbon. The
kilogramme of carbon gives about 8000 heat units, each equal to 107
kilogrammetres, or about 6,176,000 foot-pounds. Of this, in light engines,
from 5 to 10 per cent, or at least 308,800 foot-pounds, is utilized, and 25 of
purposed, however, to return to this attractive form of power if I were ever
able to realize its theoretical advantages on the larger scale which would be
desirable.
E LECTRICITY
As it was not intended to build the model aerodromes for a long flight, it
was thought that the electric motor driven by a primary or storage battery
might possibly be utilized. It therefore occurred to me that a battery might
be constructed to give great power in proportion to its weight on condition
of being short-lived, and that in this form a battery might perhaps
advantageously take the place of the dangerous compressed-air tubes that
were at the time (1893) [p027] under consideration for driving the models. I
assumed that the longest flight of the model would be less than five
minutes. Any weight of battery, then, that the model carried in consumable
parts lasting beyond this five minutes would be lost, and hence it was
proposed to build a battery, the whole active life of which would be
comprised in this time, to actuate a motor or motors driving one or two
propellers.
According to Daniell, when energy is stored in secondary batteries, over
300,000 megergs per kilogramme of weight can be recovered and utilized if
freshly charged.
300,000 megergs = 0.696 horse-power for 1 min.
300,000 megergs = 0.139 horse-power for 5 min.
In a zinc and copper primary battery with sulphuric acid and water, one
kilogramme of zinc, oxidized, furnishes at least 1200 calories as against
8000 for one kilogramme of carbon, but it is stated that the zinc energy
comes in so much more utilizable a form that the zinc, weight for weight,
gives practically, that is in work, 40 per cent that of carbon. The
kilogramme of carbon gives about 8000 heat units, each equal to 107
kilogrammetres, or about 6,176,000 foot-pounds. Of this, in light engines,
from 5 to 10 per cent, or at least 308,800 foot-pounds, is utilized, and 25 of
Page 64
this, or about 124,000 foot-pounds, would seem to be what the kilogramme
of zinc would give in actual work. But to form the battery, we must have a
larger weight of fluid than of zinc, and something must be allowed for
copper. If we suppose these to bring the weight up to 1 kilogramme, we
might still hope to have 50,000 foot-pounds or 1.5 horse-power for one
minute, or 0.3 horse-power for 5 minutes.
Storage batteries were offered with a capacity of .25 horse-power for 5
minutes per kilogramme, but according to Daniell one cannot expect to get
more than 0.139 horse-power from a freshly charged battery of that weight
for the same time.
The plan of constructing a battery of a long roll of extremely thin zinc or
magnesium, winding it up with a narrower roll of copper or platinized
silver, insulating the two metals and then pouring over enough acid to
consume the major portion of the zinc in 5 minutes, was carefully
considered, but the difficulties were so discouraging, that the work was not
undertaken.
The lightest motors of 1 horse-power capacity of which any trace could
be found weighed 25 pounds, and a prominent electrician stated that he
would not attempt to construct one of that weight.
In trials with a 12 horse-power motor driving an 80 cm. propeller of 1.00
pitch-ratio, I apparently obtained a development of 0.56 indicated horse-
power at 1265 revolutions; but at lower speeds when tried with the Prony
brake, the brake horse-power fell to 0.10 at 546 revolutions, and even at
1650 revolutions [p028] it was but 0.262 indicated, with a brake horse-power
of 0.144, or 55 per cent of that indicated.
With these results both of theoretical calculation and practical
experiment, all thought of propelling the proposed aerodrome by electricity
was necessarily abandoned.
C ARBONIC - A CID G AS
At the first inception of the idea, it seemed that carbonic-acid gas would
be the motive power best adapted for short flights. It can be obtained in the
liquid form, is compact, gives off the gas at a uniform pressure dependent
of zinc would give in actual work. But to form the battery, we must have a
larger weight of fluid than of zinc, and something must be allowed for
copper. If we suppose these to bring the weight up to 1 kilogramme, we
might still hope to have 50,000 foot-pounds or 1.5 horse-power for one
minute, or 0.3 horse-power for 5 minutes.
Storage batteries were offered with a capacity of .25 horse-power for 5
minutes per kilogramme, but according to Daniell one cannot expect to get
more than 0.139 horse-power from a freshly charged battery of that weight
for the same time.
The plan of constructing a battery of a long roll of extremely thin zinc or
magnesium, winding it up with a narrower roll of copper or platinized
silver, insulating the two metals and then pouring over enough acid to
consume the major portion of the zinc in 5 minutes, was carefully
considered, but the difficulties were so discouraging, that the work was not
undertaken.
The lightest motors of 1 horse-power capacity of which any trace could
be found weighed 25 pounds, and a prominent electrician stated that he
would not attempt to construct one of that weight.
In trials with a 12 horse-power motor driving an 80 cm. propeller of 1.00
pitch-ratio, I apparently obtained a development of 0.56 indicated horse-
power at 1265 revolutions; but at lower speeds when tried with the Prony
brake, the brake horse-power fell to 0.10 at 546 revolutions, and even at
1650 revolutions [p028] it was but 0.262 indicated, with a brake horse-power
of 0.144, or 55 per cent of that indicated.
With these results both of theoretical calculation and practical
experiment, all thought of propelling the proposed aerodrome by electricity
was necessarily abandoned.
C ARBONIC - A CID G AS
At the first inception of the idea, it seemed that carbonic-acid gas would
be the motive power best adapted for short flights. It can be obtained in the
liquid form, is compact, gives off the gas at a uniform pressure dependent
Page 65
upon the temperature, and can be used in the ordinary steam engine without
any essential modifications. The only provision that it seemed, in advance,
necessary to make, was that of some sort of a heater between the reservoir
of liquid and the engine, in order to prevent freezing, unless the liquid itself
could be heated previous to launching.
The engines in which it was first intended to use carbonic acid were the
little oscillating cylinder engines belonging to Aerodrome No. 1. The
capacity of each cylinder was 21.2 cu. cm., so that 84.8 cu. cm. of gas
would be required to turn the propellers one revolution when admitted for
the full stroke, and 101,760 cubic cm. for 1200 revolutions. The density of
the liquid at a temperature of 24° C. was taken as .72, and as 1 volume of
liquid gives 180 volumes of gas at a pressure of 2 12 atmospheres, we have
101,760
180
= 565 cu. cm. of liquid, or 407 grammes required for 1200
revolutions of the engines.
Thus, a theoretical calculation seemed to indicate that a kilogramme of
liquid carbonic acid would be an ample supply for a run of two minutes.
The experiments were, at first, somewhat encouraging. The speed and
apparent power of the engines were sufficient for the purpose, but the
length of time during which power could be obtained was limited.
In 1892, 415 grammes of carbonic acid drove the engines of Aerodrome
No. 3 700 revolutions in 60 seconds, 900 in 75, and 1000 in 85 seconds, at
the end of which time the gas was entirely expended. The diameter of these
cylinders was 2.4 cm., the stroke of the pistons 7 cm., and the work done,
that of driving a pair of 50 cm. propellers, when taken in comparison with
the propeller tests detailed elsewhere, amounted to an effective horse-power
of about 0.10 for the output of the engine.
The difficulties, however, that were experienced were those partially
foreseen. The expansion of the gas made such serious inroads upon the
latent heat of the liquid, that lumps of solid acid were formed in the
reservoir, and could be heard rattling against the sides when the latter was
shaken, while the expansion of the exhaust caused such a lowering of
any essential modifications. The only provision that it seemed, in advance,
necessary to make, was that of some sort of a heater between the reservoir
of liquid and the engine, in order to prevent freezing, unless the liquid itself
could be heated previous to launching.
The engines in which it was first intended to use carbonic acid were the
little oscillating cylinder engines belonging to Aerodrome No. 1. The
capacity of each cylinder was 21.2 cu. cm., so that 84.8 cu. cm. of gas
would be required to turn the propellers one revolution when admitted for
the full stroke, and 101,760 cubic cm. for 1200 revolutions. The density of
the liquid at a temperature of 24° C. was taken as .72, and as 1 volume of
liquid gives 180 volumes of gas at a pressure of 2 12 atmospheres, we have
101,760
180
= 565 cu. cm. of liquid, or 407 grammes required for 1200
revolutions of the engines.
Thus, a theoretical calculation seemed to indicate that a kilogramme of
liquid carbonic acid would be an ample supply for a run of two minutes.
The experiments were, at first, somewhat encouraging. The speed and
apparent power of the engines were sufficient for the purpose, but the
length of time during which power could be obtained was limited.
In 1892, 415 grammes of carbonic acid drove the engines of Aerodrome
No. 3 700 revolutions in 60 seconds, 900 in 75, and 1000 in 85 seconds, at
the end of which time the gas was entirely expended. The diameter of these
cylinders was 2.4 cm., the stroke of the pistons 7 cm., and the work done,
that of driving a pair of 50 cm. propellers, when taken in comparison with
the propeller tests detailed elsewhere, amounted to an effective horse-power
of about 0.10 for the output of the engine.
The difficulties, however, that were experienced were those partially
foreseen. The expansion of the gas made such serious inroads upon the
latent heat of the liquid, that lumps of solid acid were formed in the
reservoir, and could be heard rattling against the sides when the latter was
shaken, while the expansion of the exhaust caused such a lowering of
Page 66
temperature at that point, that the [p029] pipes were soon covered with a
thick layer of ice, and the free exit of the escaping gas was prevented.
Such difficulties are to be expected with this material, but here they were
enhanced by the small scale of the construction and the constant demand for
lightness. And it was found to be very hard to fill the small reservoirs
intended to carry the supply for the engines. When they were screwed to the
large case in which the liquid was received and the whole inverted, the
small reservoir would be filled from one-third to one-half full, and nothing
that could be done would force any more liquid to enter.
In view of these difficulties, and the objections to using a heater of any
sort for the gas, as well as the absolute lack of success attendant upon the
experiments of others who were attempting to use liquid CO2 as a motive
power on a large scale elsewhere, experiments were at first temporarily and
afterwards permanently abandoned.
The above experiments extended over nearly a year in time, chiefly
during 1892, and involved the construction and use of the small aerodromes
Nos. 1, 2, and 3, presently described.
thick layer of ice, and the free exit of the escaping gas was prevented.
Such difficulties are to be expected with this material, but here they were
enhanced by the small scale of the construction and the constant demand for
lightness. And it was found to be very hard to fill the small reservoirs
intended to carry the supply for the engines. When they were screwed to the
large case in which the liquid was received and the whole inverted, the
small reservoir would be filled from one-third to one-half full, and nothing
that could be done would force any more liquid to enter.
In view of these difficulties, and the objections to using a heater of any
sort for the gas, as well as the absolute lack of success attendant upon the
experiments of others who were attempting to use liquid CO2 as a motive
power on a large scale elsewhere, experiments were at first temporarily and
afterwards permanently abandoned.
The above experiments extended over nearly a year in time, chiefly
during 1892, and involved the construction and use of the small aerodromes
Nos. 1, 2, and 3, presently described.
Page 67
[p030] ◊
CHAPTER IV
EARLY STEAM MOTORS AND OTHER MODELS
In dealing with the development of the aerodrome, subsequent to the
early rubber-driven models, the very considerable work done and the
failures incurred with other types of motors than steam, have been briefly
dealt with in the preceding chapter, but are scarcely mentioned here, as no
attempts at long flights were ever successful with any other motor than
steam, and no information was gained from any of the experiments made
with compressed air, gas, carbonic acid, or electricity, that was of much
value in the development of the successful steam machines.
In November, 1891, after the long and unsatisfactory experiments with
rubber-driven models already referred to, and before most of the
experiments with other available motors than steam had been made, I
commenced the construction of the engines and the design of the hull of a
steam-driven aerodrome, which was intended to supplement the
experiments given in “Aerodynamics” by others made under the conditions
of actual flight.
In designing this first aerodrome, here called No. 0, there was no
precedent or example, and except for the purely theoretical conditions
ascertained by the experiments described in “Aerodynamics,” everything
was unknown. Next to nothing was known as to the size or form, as to the
requisite strength, or as to the way of attaching the sustaining surfaces;
almost nothing was known as to the weight permissible, and nothing as to
the proper scale on which to build the aerodrome, even if the design had
been obtained, while everything which related to the actual construction of
boiler and engines working under such unprecedented conditions was yet to
be determined by experiment.
The scale of the actual construction was adopted under the belief that it
must be large enough to carry certain automatic steering apparatus which I
had designed, and which possessed considerable weight. I decided that a
CHAPTER IV
EARLY STEAM MOTORS AND OTHER MODELS
In dealing with the development of the aerodrome, subsequent to the
early rubber-driven models, the very considerable work done and the
failures incurred with other types of motors than steam, have been briefly
dealt with in the preceding chapter, but are scarcely mentioned here, as no
attempts at long flights were ever successful with any other motor than
steam, and no information was gained from any of the experiments made
with compressed air, gas, carbonic acid, or electricity, that was of much
value in the development of the successful steam machines.
In November, 1891, after the long and unsatisfactory experiments with
rubber-driven models already referred to, and before most of the
experiments with other available motors than steam had been made, I
commenced the construction of the engines and the design of the hull of a
steam-driven aerodrome, which was intended to supplement the
experiments given in “Aerodynamics” by others made under the conditions
of actual flight.
In designing this first aerodrome, here called No. 0, there was no
precedent or example, and except for the purely theoretical conditions
ascertained by the experiments described in “Aerodynamics,” everything
was unknown. Next to nothing was known as to the size or form, as to the
requisite strength, or as to the way of attaching the sustaining surfaces;
almost nothing was known as to the weight permissible, and nothing as to
the proper scale on which to build the aerodrome, even if the design had
been obtained, while everything which related to the actual construction of
boiler and engines working under such unprecedented conditions was yet to
be determined by experiment.
The scale of the actual construction was adopted under the belief that it
must be large enough to carry certain automatic steering apparatus which I
had designed, and which possessed considerable weight. I decided that a
Page 68
flying machine if not large enough to carry a manager, should in the
absence of a human directing intelligence, have some sort of automatic
substitute for it, and be large enough to have the means of maintaining a
long and steady flight, during which the problems (which the rubber-driven
models so imperfectly answered) could be effectually solved.
When, in 1891, it was decided to attempt to build this steam aerodrome,
the only engine that had been made up to that time with any claim to the
lightness and power I was seeking, was the Stringfellow engine, exhibited
at the Crystal Palace in London, in 1868, which it was then announced
developed 1 horse-power [p031] for a total weight (boiler and engines) of 13
pounds. The original engine came into the possession of the Institution in
1889 as an historical curiosity, but on examination, it was at once evident
that it never had developed, and never could develop the power that had
been attributed to it, and probably not one-tenth so much.
With the results obtained on the whirling-table at Allegheny as a basis, a
theoretical computation of the weight which 1 horse-power would cause to
soar showed that, with a plane whose efficiency should be equal to that of a
30 × 4.8 inch plane set at an angle of 5° and moving at a speed of 34 miles
an hour, 1 horse-power would support 120 pounds.19 With a smaller angle
even better results could be obtained, but as the difficulties of guidance
increase as the angle diminishes, I did not venture to aim at less than this. In
this computation, no allowance was made for the fact that these results were
obtained by a mechanism which forcibly maintained the supporting surface
in the ideal condition of the best attainable angle of attack as if in perfect
equilibrium, and above all in the equally ideal condition of perfectly
horizontal flight.
Besides this, I had to consider in actual flight the air resistance due to the
guy wires and hull, but after making an allowance of as much as three-
quarters for these differences between the conditions of experiment and
those of free flight, I hoped that 1 horse-power would serve to carry 30
pounds through the air if a supporting surface as large as 3 feet to the pound
could be provided, and this was the basis of the construction which I will
now describe.
absence of a human directing intelligence, have some sort of automatic
substitute for it, and be large enough to have the means of maintaining a
long and steady flight, during which the problems (which the rubber-driven
models so imperfectly answered) could be effectually solved.
When, in 1891, it was decided to attempt to build this steam aerodrome,
the only engine that had been made up to that time with any claim to the
lightness and power I was seeking, was the Stringfellow engine, exhibited
at the Crystal Palace in London, in 1868, which it was then announced
developed 1 horse-power [p031] for a total weight (boiler and engines) of 13
pounds. The original engine came into the possession of the Institution in
1889 as an historical curiosity, but on examination, it was at once evident
that it never had developed, and never could develop the power that had
been attributed to it, and probably not one-tenth so much.
With the results obtained on the whirling-table at Allegheny as a basis, a
theoretical computation of the weight which 1 horse-power would cause to
soar showed that, with a plane whose efficiency should be equal to that of a
30 × 4.8 inch plane set at an angle of 5° and moving at a speed of 34 miles
an hour, 1 horse-power would support 120 pounds.19 With a smaller angle
even better results could be obtained, but as the difficulties of guidance
increase as the angle diminishes, I did not venture to aim at less than this. In
this computation, no allowance was made for the fact that these results were
obtained by a mechanism which forcibly maintained the supporting surface
in the ideal condition of the best attainable angle of attack as if in perfect
equilibrium, and above all in the equally ideal condition of perfectly
horizontal flight.
Besides this, I had to consider in actual flight the air resistance due to the
guy wires and hull, but after making an allowance of as much as three-
quarters for these differences between the conditions of experiment and
those of free flight, I hoped that 1 horse-power would serve to carry 30
pounds through the air if a supporting surface as large as 3 feet to the pound
could be provided, and this was the basis of the construction which I will
now describe.
Page 69
The general form of this Aerodrome No. 0, without wings or propellers,
is shown in the accompanying photograph in Plate 10. Its dimensions and
its weights, as first designed, and as finally found necessary, are as follows:
COMPARISON OF ESTIMATED AND ACTUAL WEIGHTS OF PARTS OF AERODROME
“0”—IN POUNDS AND OUNCES.
Estimated Actual
lbs. oz. lbs. oz.
Engines 4 0 4 1
Boilers and Burners 8 11 13 14
Pumps and Attachments 0 0 1 10
Steering Apparatus 0 6 0 0
Frame of Hull and Braces, including bowsprit and tail tube 7 7 8 11
Oil tank covering and pipes 0 0 0 13
Shafts, ball bearings (2:1) and wooden propellers (1:7) 1 14 3 8
Wings (5:4) and guys (0:9) 4 0 5 13
Tail 1 5 2 2
Jacket at prow 0 0 4 0
Total without oil or water 27 11 44 8
(The weights attained in the actual making were, as is seen, nearly double
those first estimated, and this constant increase of weight under the
exigencies of construction was a feature which could never be wholly
eliminated.) [p032]
After studying various forms for the hull or body of the prospective
aerodrome, I was led to adopt the lines which Nature has used in the
mackerel as most advantageous so far as the resistance of the air was
concerned, but it proved to be difficult in construction to make the lines of
the bow materially different from those of the stern, and in this first model
the figure was symmetrical throughout.
As I wish that my experience may be of benefit to the reader, even in its
failures, I will add that I made the not unnatural mistake of building on the
plan on which the hull of an ordinary ship is constructed; that is, making the
hull support the projecting bowsprit and other parts. In the aerodrome, what
corresponds to the bowsprit must project far in advance of the hull to
sustain the front wings, and a like piece must project behind it to sustain the
rear wings and the tail, or the supporting surfaces of whatever kind. The
mistake of the construction lay in disjoining these two and connecting them
is shown in the accompanying photograph in Plate 10. Its dimensions and
its weights, as first designed, and as finally found necessary, are as follows:
COMPARISON OF ESTIMATED AND ACTUAL WEIGHTS OF PARTS OF AERODROME
“0”—IN POUNDS AND OUNCES.
Estimated Actual
lbs. oz. lbs. oz.
Engines 4 0 4 1
Boilers and Burners 8 11 13 14
Pumps and Attachments 0 0 1 10
Steering Apparatus 0 6 0 0
Frame of Hull and Braces, including bowsprit and tail tube 7 7 8 11
Oil tank covering and pipes 0 0 0 13
Shafts, ball bearings (2:1) and wooden propellers (1:7) 1 14 3 8
Wings (5:4) and guys (0:9) 4 0 5 13
Tail 1 5 2 2
Jacket at prow 0 0 4 0
Total without oil or water 27 11 44 8
(The weights attained in the actual making were, as is seen, nearly double
those first estimated, and this constant increase of weight under the
exigencies of construction was a feature which could never be wholly
eliminated.) [p032]
After studying various forms for the hull or body of the prospective
aerodrome, I was led to adopt the lines which Nature has used in the
mackerel as most advantageous so far as the resistance of the air was
concerned, but it proved to be difficult in construction to make the lines of
the bow materially different from those of the stern, and in this first model
the figure was symmetrical throughout.
As I wish that my experience may be of benefit to the reader, even in its
failures, I will add that I made the not unnatural mistake of building on the
plan on which the hull of an ordinary ship is constructed; that is, making the
hull support the projecting bowsprit and other parts. In the aerodrome, what
corresponds to the bowsprit must project far in advance of the hull to
sustain the front wings, and a like piece must project behind it to sustain the
rear wings and the tail, or the supporting surfaces of whatever kind. The
mistake of the construction lay in disjoining these two and connecting them
Page 70
indirectly by the insufficiently strong hull which supported them. This hull
was formed of longitudinal U-shaped ribs of thin steel, which rested on
rings made of an alloy of aluminum, which possessed the lightness of the
latter metal with very considerable toughness, but which was finally
unsatisfactory. I may say parenthetically that in none of the subsequent
constructions has the lightness of aluminum been found to compensate for
its very many disadvantages. The two rods, which were each 1 metre in
length, were with difficulty kept rigorously in line, owing to the yielding of
the constructionally weak hull. It would have been better, in fact, to have
carried the rod straight through at any inconvenience to the disposition of
the boilers and the engine.
was formed of longitudinal U-shaped ribs of thin steel, which rested on
rings made of an alloy of aluminum, which possessed the lightness of the
latter metal with very considerable toughness, but which was finally
unsatisfactory. I may say parenthetically that in none of the subsequent
constructions has the lightness of aluminum been found to compensate for
its very many disadvantages. The two rods, which were each 1 metre in
length, were with difficulty kept rigorously in line, owing to the yielding of
the constructionally weak hull. It would have been better, in fact, to have
carried the rod straight through at any inconvenience to the disposition of
the boilers and the engine.
Page 71
PL. 10. STEEL FRAMES OF AERODROMES NOS. 0, 1, 2, 3, 1891 AND 1892 ◊
Page 72
I may add that the sustaining surfaces, which were to be nearly flat
wings, composed of silk stretched from a steel tube with wooden
attachments, were to [p033] have been carried on the front rod, but, as
subsequent experience has shown, these wings would have been inadequate
to the work, both from their insufficient size and their lack of rigidity.
The propellers, which were to be 80 cm. in diameter, 1.25 pitch-ratio, and
which were expected to make from five to six hundred revolutions a
minute, were carried on the end of long tubular shafts, not parallel, but
making with each other an angle of 25 degrees, and united by gears near the
bow of the vessel in the manner shown in Plate 10.
The first engines were of the oscillating type, with the piston-rod
connected directly to the crank; were very light, and were unprovided with
many of the usual fittings belonging to a steam engine, such as rod or piston
packing; and their construction was crude in comparison with their
successors. They were tested with the Prony brake and found to be deficient
in power, for with a steam pressure of 80 pounds to the square inch, they
ran at the rate of 1170 revolutions per minute, and developed only .363
horse-power. It soon became evident that they were too light for the work
that it was intended that they should do, and steps were taken, even before
the completion of these tests, for the construction of a pair of more
powerful cylinders, which should also be provided with a special boiler for
the generation of the steam. Acting upon the supposition, in a saving of
steam, it was decided to work with compounded cylinders. As two
propellers were to be used, they were each fitted with a distinct pair of
cylinders working directly upon the shaft, but so connected by gearing that
they were compelled to turn at the same rate of speed.
The cylinders were of the inverted oscillating type, like the first pair of
engines, but, unlike them, they were single-acting. The dimensions were:
diameter of high-pressure cylinder 1.25 inches; low pressure, 1.94 inches,
with a common stroke of 2 inches, and with cranks set opposite to each
other so that one cylinder was always at work. The cylinders were held at
their upper ends by a strap passing around a hollow conical trunk, which
served the double purpose of a support for the cylinders and an intermediate
wings, composed of silk stretched from a steel tube with wooden
attachments, were to [p033] have been carried on the front rod, but, as
subsequent experience has shown, these wings would have been inadequate
to the work, both from their insufficient size and their lack of rigidity.
The propellers, which were to be 80 cm. in diameter, 1.25 pitch-ratio, and
which were expected to make from five to six hundred revolutions a
minute, were carried on the end of long tubular shafts, not parallel, but
making with each other an angle of 25 degrees, and united by gears near the
bow of the vessel in the manner shown in Plate 10.
The first engines were of the oscillating type, with the piston-rod
connected directly to the crank; were very light, and were unprovided with
many of the usual fittings belonging to a steam engine, such as rod or piston
packing; and their construction was crude in comparison with their
successors. They were tested with the Prony brake and found to be deficient
in power, for with a steam pressure of 80 pounds to the square inch, they
ran at the rate of 1170 revolutions per minute, and developed only .363
horse-power. It soon became evident that they were too light for the work
that it was intended that they should do, and steps were taken, even before
the completion of these tests, for the construction of a pair of more
powerful cylinders, which should also be provided with a special boiler for
the generation of the steam. Acting upon the supposition, in a saving of
steam, it was decided to work with compounded cylinders. As two
propellers were to be used, they were each fitted with a distinct pair of
cylinders working directly upon the shaft, but so connected by gearing that
they were compelled to turn at the same rate of speed.
The cylinders were of the inverted oscillating type, like the first pair of
engines, but, unlike them, they were single-acting. The dimensions were:
diameter of high-pressure cylinder 1.25 inches; low pressure, 1.94 inches,
with a common stroke of 2 inches, and with cranks set opposite to each
other so that one cylinder was always at work. The cylinders were held at
their upper ends by a strap passing around a hollow conical trunk, which
served the double purpose of a support for the cylinders and an intermediate
Page 73
receiver between them. This receiver had a mean inside diameter of 1.25
inches, with a length of 4.75 inches, so that it had about twice the cubical
capacity of the high-pressure cylinder, while the displacement of the low-
pressure cylinder was about 2.5 times that of the high; ratios that would
have given satisfactory results, perhaps, had the steam pressure and other
conditions been favorable to the use of the compound principle in this
place. There were no valves for the admission of the steam, for, inasmuch
as the engines were single-acting, it was possible to make ports in the
cylinder-head act as the admission and exhaust ports as the cylinder
oscillated, and thus avoid the complication and weight of eccentric and
valves. [p034]
These cylinders were set in a light frame at an angle of 25° with each
other, or 12.5° with the median line of the aerodrome, and drove the long
propeller shafts as shown in Plate 10, No. 0. At the extreme forward end of
the crank-shafts there was a pair of intermeshing bevel gears which served
to maintain the rate of revolution of the two propellers the same.
inches, with a length of 4.75 inches, so that it had about twice the cubical
capacity of the high-pressure cylinder, while the displacement of the low-
pressure cylinder was about 2.5 times that of the high; ratios that would
have given satisfactory results, perhaps, had the steam pressure and other
conditions been favorable to the use of the compound principle in this
place. There were no valves for the admission of the steam, for, inasmuch
as the engines were single-acting, it was possible to make ports in the
cylinder-head act as the admission and exhaust ports as the cylinder
oscillated, and thus avoid the complication and weight of eccentric and
valves. [p034]
These cylinders were set in a light frame at an angle of 25° with each
other, or 12.5° with the median line of the aerodrome, and drove the long
propeller shafts as shown in Plate 10, No. 0. At the extreme forward end of
the crank-shafts there was a pair of intermeshing bevel gears which served
to maintain the rate of revolution of the two propellers the same.
Page 74
FIG. 3. Boilers in use in 1891–1892.
The boiler built for this work was a beehive-shaped arrangement of coils
of pipe. It consisted at first, as shown in Fig. 3, of three double coils of
3
8
-inch copper pipe coiled up in the shape of a truncated cone, carrying in
the central portion a pear-shaped receiver into the upper portion of which
the water circulating through the coils discharged. Each of these receivers
was connected at the top with the bottom of a long cylindrical drum, with
hemispherical ends, which formed a steam space from which supply for the
engines was drawn. The lower ends of the coils were connected with an
injection pipe supplying the water. Each “beehive” had 23 turns of tubing,
and had a base of 7.5 inches and a top diameter of 6 inches, the steam drum
being 2.5 inches in diameter. I may here say that in the selection of the
general type of boiler for the work to be done, there was never any
hesitation regarding the use of the water-tube variety. Their superiority for
the quick generation of large volumes of steam had been so pronounced that
The boiler built for this work was a beehive-shaped arrangement of coils
of pipe. It consisted at first, as shown in Fig. 3, of three double coils of
3
8
-inch copper pipe coiled up in the shape of a truncated cone, carrying in
the central portion a pear-shaped receiver into the upper portion of which
the water circulating through the coils discharged. Each of these receivers
was connected at the top with the bottom of a long cylindrical drum, with
hemispherical ends, which formed a steam space from which supply for the
engines was drawn. The lower ends of the coils were connected with an
injection pipe supplying the water. Each “beehive” had 23 turns of tubing,
and had a base of 7.5 inches and a top diameter of 6 inches, the steam drum
being 2.5 inches in diameter. I may here say that in the selection of the
general type of boiler for the work to be done, there was never any
hesitation regarding the use of the water-tube variety. Their superiority for
the quick generation of large volumes of steam had been so pronounced that
Page 75
nothing else seemed capable of competing with [p035] them in this respect,
regardless of the absolute economy of fuel that might or might not be
exhibited. Hence, to the end of my experiments nothing else was used.
Even before the “beehive” boiler was completed, I was anxious to
ascertain what could be done with a coil of pipe with a stream of water
circulating through it, as well as with various forms of burners, for I
realized that the success of the apparatus depended not only upon getting an
exceedingly effective heating surface, but also an equally effective flame to
do the heating.
For fuel I naturally turned to the liquids as being more compact and
readily regulated. Whether to use some of the more volatile hydrocarbons or
alcohol, was still an unsolved problem, but my opinion at the time was that,
on the limited scale of the model, better results could probably be obtained
with alcohol.
In the experiments made with a coil preliminary to the trial of the
“beehive” boiler, I tried a simple horizontal coil of 38 -inch copper pipe into
which two forked burners working on the Bunsen principle and using city
illuminating gas, were thrust. The jets were about 12 inch apart. The
arrangement primed so badly that the engines could not get rid of the
entrained water, and would only make a few turns.
I then tried the same coil with two 1.25-inch drums in the inside and with
five longitudinal water tubes at the bottom, beneath which were the same
two forked burners used in the previous experiment. The coils were covered
with a sheet of asbestos, and two round burners were added. This boiler
would hold a steam pressure of about 15 pounds and run the engine slowly;
but if the pressure were allowed to rise to 60 pounds, the engine would
drive a 2-foot propeller of 18-inch pitch at the rate of about 650 turns per
minute for from 80 to 90 seconds, while the steam ran down to 10 pounds,
showing that this boiler, at least, was too small. This was further shown in a
trial of the plain coil made in October, 1891; 6 pounds of water were
evaporated in 32 minutes under a pressure of 60 pounds. This was at the
rate of 11.25 pounds per hour, or, taking the U. S. Centennial standard of 30
regardless of the absolute economy of fuel that might or might not be
exhibited. Hence, to the end of my experiments nothing else was used.
Even before the “beehive” boiler was completed, I was anxious to
ascertain what could be done with a coil of pipe with a stream of water
circulating through it, as well as with various forms of burners, for I
realized that the success of the apparatus depended not only upon getting an
exceedingly effective heating surface, but also an equally effective flame to
do the heating.
For fuel I naturally turned to the liquids as being more compact and
readily regulated. Whether to use some of the more volatile hydrocarbons or
alcohol, was still an unsolved problem, but my opinion at the time was that,
on the limited scale of the model, better results could probably be obtained
with alcohol.
In the experiments made with a coil preliminary to the trial of the
“beehive” boiler, I tried a simple horizontal coil of 38 -inch copper pipe into
which two forked burners working on the Bunsen principle and using city
illuminating gas, were thrust. The jets were about 12 inch apart. The
arrangement primed so badly that the engines could not get rid of the
entrained water, and would only make a few turns.
I then tried the same coil with two 1.25-inch drums in the inside and with
five longitudinal water tubes at the bottom, beneath which were the same
two forked burners used in the previous experiment. The coils were covered
with a sheet of asbestos, and two round burners were added. This boiler
would hold a steam pressure of about 15 pounds and run the engine slowly;
but if the pressure were allowed to rise to 60 pounds, the engine would
drive a 2-foot propeller of 18-inch pitch at the rate of about 650 turns per
minute for from 80 to 90 seconds, while the steam ran down to 10 pounds,
showing that this boiler, at least, was too small. This was further shown in a
trial of the plain coil made in October, 1891; 6 pounds of water were
evaporated in 32 minutes under a pressure of 60 pounds. This was at the
rate of 11.25 pounds per hour, or, taking the U. S. Centennial standard of 30
Page 76
pounds of evaporation per horse-power, gave an available output of less
than 13 horse-power.
With these results before me, I decided to make a trial of the “beehive”
principle upon a smaller scale than in the boiler designed for Aerodrome
No. 0. I used a small boiler of which the inner coil consisted of 8 turns of
3
8
-inch copper tube about 28 gauge thick, and the outer coil of 11 turns of
1 3 1
4
-inch copper pipe. This gave 12 feet of 8
-inch, and 16 feet of 4
-inch
tubing. The drum was of No. 27 gauge, hard planished copper. With this
boiler consuming 6 oz. of fuel, 80.3 oz. of water were evaporated in 28
minutes, or at the rate of about 10.75 pounds per hour. As these coils
contained but 2.22 square feet of heating surface, and as the three to be built
would contain 3.7 square feet each, it was estimated the [p036] 10 square feet
afforded by them could safely be depended upon to provide steam for a 1
horse-power engine. As far as fuel consumption was concerned, the rate of
evaporation was about 15.6 pounds of water per pound of gasoline, all of
which was satisfactory.
The burner originally designed for use in connection with the “beehive”
boilers, consisted of a small tank in which a quantity of gasoline was
placed, the space above being filled with compressed air. Rising from the
bottom of this tank was a small pipe coiling back and down and ending in
an upturned jet from which the gas generated in the coil would issue. The
burner thus served to generate its own gas and act as a heater for the boilers
at the same time.
In the construction of Aerodrome No. 0, four of the “beehive” coils were
placed in a line fore and aft. The fuel tank was located immediately back of
the rear coil and consisted of a copper cylinder 11 cm. in diameter and 9
cm. long. The engines were placed immediately in front of the coils, all the
apparatus being enclosed in a light framing, as shown in the photograph
(Plate 10).
Extending front and back from the hull were the tubes for supporting the
wings and tail, each one metre in length. The cross-framing for carrying the
than 13 horse-power.
With these results before me, I decided to make a trial of the “beehive”
principle upon a smaller scale than in the boiler designed for Aerodrome
No. 0. I used a small boiler of which the inner coil consisted of 8 turns of
3
8
-inch copper tube about 28 gauge thick, and the outer coil of 11 turns of
1 3 1
4
-inch copper pipe. This gave 12 feet of 8
-inch, and 16 feet of 4
-inch
tubing. The drum was of No. 27 gauge, hard planished copper. With this
boiler consuming 6 oz. of fuel, 80.3 oz. of water were evaporated in 28
minutes, or at the rate of about 10.75 pounds per hour. As these coils
contained but 2.22 square feet of heating surface, and as the three to be built
would contain 3.7 square feet each, it was estimated the [p036] 10 square feet
afforded by them could safely be depended upon to provide steam for a 1
horse-power engine. As far as fuel consumption was concerned, the rate of
evaporation was about 15.6 pounds of water per pound of gasoline, all of
which was satisfactory.
The burner originally designed for use in connection with the “beehive”
boilers, consisted of a small tank in which a quantity of gasoline was
placed, the space above being filled with compressed air. Rising from the
bottom of this tank was a small pipe coiling back and down and ending in
an upturned jet from which the gas generated in the coil would issue. The
burner thus served to generate its own gas and act as a heater for the boilers
at the same time.
In the construction of Aerodrome No. 0, four of the “beehive” coils were
placed in a line fore and aft. The fuel tank was located immediately back of
the rear coil and consisted of a copper cylinder 11 cm. in diameter and 9
cm. long. The engines were placed immediately in front of the coils, all the
apparatus being enclosed in a light framing, as shown in the photograph
(Plate 10).
Extending front and back from the hull were the tubes for supporting the
wings and tail, each one metre in length. The cross-framing for carrying the
Page 77
propeller shafts was built of tubing 1.5 cm. diameter, and the shafts
themselves were of the same size. The ribs of the hull were rings made of
angle-irons measuring 1.50 × 1.75 cm., which were held in place
longitudinally by five 0.7 cm. channel bars.
As it had been learned in the preliminary experiments with the model
“beehive” boiler that the heated water would not of itself cause a
sufficiently rapid circulation to be maintained through the tubes to prevent
them from becoming red-hot, two circulating pumps were added for forcing
the water through the coils of the two forward and two rear boilers
respectively, the water being taken from the lower side of the drum and
delivered into the bottom of the coils, which were united at that point for
the purpose. A worm was placed upon each of the propeller shafts, just back
of the engines, meshing in with a gear on a crank-shaft from which the
pumps were driven. This shaft rotated at the rate of 1 to 24, so that for 1200
revolutions of the engine, it would make but 50, driving a single-acting
plunger 1.2 cm. in diameter and 2 cm. stroke.
Apparently all was going well until I began to try the apparatus. First,
there was a difficulty with the burner, which could not be made to give forth
the relative amount of heat that had been obtained from the smaller model,
and steam could not be maintained. With one “beehive” connected with the
compound engine, and a 70 cm. propeller on the shaft, there were about 250
turns per minute for a space of about 50 seconds, in which time the steam
would fall from 90 pounds to 25 pounds, and the engine would stop. Then,
as we had no air-chamber on the pumps at the time, they would not drive
the water through the coils. Subsequent experiments, however, showed that
the boilers could be [p037] depended upon to supply the steam that the
compound engines would require; but after the whole was completed, the
weight, if nothing else, was prohibitory.
I had gone on from one thing to another, adding a little here and a little
there, strengthening this part and that, until when the hull was finally
completed with the engines and boilers in place, ready for the application of
the wings, the weight of the whole was found (allowing 7 pounds for the
weight of the wings and tail) to be almost exactly 45 pounds, and nearly 52
themselves were of the same size. The ribs of the hull were rings made of
angle-irons measuring 1.50 × 1.75 cm., which were held in place
longitudinally by five 0.7 cm. channel bars.
As it had been learned in the preliminary experiments with the model
“beehive” boiler that the heated water would not of itself cause a
sufficiently rapid circulation to be maintained through the tubes to prevent
them from becoming red-hot, two circulating pumps were added for forcing
the water through the coils of the two forward and two rear boilers
respectively, the water being taken from the lower side of the drum and
delivered into the bottom of the coils, which were united at that point for
the purpose. A worm was placed upon each of the propeller shafts, just back
of the engines, meshing in with a gear on a crank-shaft from which the
pumps were driven. This shaft rotated at the rate of 1 to 24, so that for 1200
revolutions of the engine, it would make but 50, driving a single-acting
plunger 1.2 cm. in diameter and 2 cm. stroke.
Apparently all was going well until I began to try the apparatus. First,
there was a difficulty with the burner, which could not be made to give forth
the relative amount of heat that had been obtained from the smaller model,
and steam could not be maintained. With one “beehive” connected with the
compound engine, and a 70 cm. propeller on the shaft, there were about 250
turns per minute for a space of about 50 seconds, in which time the steam
would fall from 90 pounds to 25 pounds, and the engine would stop. Then,
as we had no air-chamber on the pumps at the time, they would not drive
the water through the coils. Subsequent experiments, however, showed that
the boilers could be [p037] depended upon to supply the steam that the
compound engines would require; but after the whole was completed, the
weight, if nothing else, was prohibitory.
I had gone on from one thing to another, adding a little here and a little
there, strengthening this part and that, until when the hull was finally
completed with the engines and boilers in place, ready for the application of
the wings, the weight of the whole was found (allowing 7 pounds for the
weight of the wings and tail) to be almost exactly 45 pounds, and nearly 52
Page 78
pounds with fuel and water. To this excessive weight would have to be
added that of the propellers, and as the wings would necessarily have to be
made very large in order to carry the machine, and as the difficulties of
launching had still to be met, nothing was attempted in the way of field
trials, and with great disappointment the decision was made in May, 1892
(wisely, as it subsequently appeared) to proceed no further with this special
apparatus.
However, inasmuch as this aerodrome with its engines and boilers had
been completed at considerable expense, it was decided to use the apparatus
as far as it might be practicable, in order to learn what must be done to
secure a greater amount of success in the future. The fundamental trouble
was to get heat. In the first place there was trouble with the burners, for it
seemed to be impossible to get one that would vaporize the gasoline in
sufficient quantity to do the work, and various forms were successively
tried.
All of the early part of 1892 was passed in trying to get the boilers to
work at a steam pressure of 100 pounds per square inch. On account of the
defects in the tubes and elsewhere this required much patient labor. The
writer, even thus early, devised a plan of using a sort of aeolipile, which
should actuate its own blast, but this had to be abandoned on account of the
fact that the pear-shaped receivers would not stand the heat. This
necessitated a number of experiments in the distillation of gas, in the course
of which there was trouble with the pumps, and a continual series of
breakages and leakages, so that the middle of April came before I had
secured any further satisfaction than to demonstrate that possibly the boilers
might have a capacity sufficient for the work laid out for them to do; but
subsequent experiments showed that even in this I was mistaken, for it was
only after additional jets had been put in between the coils that I succeeded
in getting an effective horse-power of 0.43 out of the combination.
Finally, on the 14th of April, after having reduced the capacity of the
pumps to the dimensions given above (for the stroke was originally 1.25
inch) I obtained the development of 1 full horse-power by the engine for 41
seconds, with a steam pressure of 100 pounds per square inch, and a rate of
added that of the propellers, and as the wings would necessarily have to be
made very large in order to carry the machine, and as the difficulties of
launching had still to be met, nothing was attempted in the way of field
trials, and with great disappointment the decision was made in May, 1892
(wisely, as it subsequently appeared) to proceed no further with this special
apparatus.
However, inasmuch as this aerodrome with its engines and boilers had
been completed at considerable expense, it was decided to use the apparatus
as far as it might be practicable, in order to learn what must be done to
secure a greater amount of success in the future. The fundamental trouble
was to get heat. In the first place there was trouble with the burners, for it
seemed to be impossible to get one that would vaporize the gasoline in
sufficient quantity to do the work, and various forms were successively
tried.
All of the early part of 1892 was passed in trying to get the boilers to
work at a steam pressure of 100 pounds per square inch. On account of the
defects in the tubes and elsewhere this required much patient labor. The
writer, even thus early, devised a plan of using a sort of aeolipile, which
should actuate its own blast, but this had to be abandoned on account of the
fact that the pear-shaped receivers would not stand the heat. This
necessitated a number of experiments in the distillation of gas, in the course
of which there was trouble with the pumps, and a continual series of
breakages and leakages, so that the middle of April came before I had
secured any further satisfaction than to demonstrate that possibly the boilers
might have a capacity sufficient for the work laid out for them to do; but
subsequent experiments showed that even in this I was mistaken, for it was
only after additional jets had been put in between the coils that I succeeded
in getting an effective horse-power of 0.43 out of the combination.
Finally, on the 14th of April, after having reduced the capacity of the
pumps to the dimensions given above (for the stroke was originally 1.25
inch) I obtained the development of 1 full horse-power by the engine for 41
seconds, with a steam pressure of 100 pounds per square inch, and a rate of
Page 79
revolution of 720 per minute. But at the end of this brief period, the shafts
sprung and the worm was thrown out of gear. [p038]
I pass over numerous other experiments, for their only result was to make
it clear that the aerodrome, as it had been constructed, could not be made to
work efficiently, even if its great weight had not served as a bar to its flight.
It was, therefore, decided to proceed with the construction of another.
After the failure of the first steam-driven model No. 0, which has just
been described, subsequent light models were constructed. These, three in
number, made with a view to the employment of carbonic acid or
compressed air, but also to the possible use of steam, are shown in Plate 10,
Nos. 1, 2, 3; on the same scale as the larger model which had preceded
them. In describing these, it will be well to mention constructive features
which were experimented on in them, as well as to describe the engines
used.
In No. 1, which was intended to be on about 25 the linear scale of No. 0,
the constructive fault of the latter, that of making the support depend on a
too flexible hull, was avoided, and the straight steel tube (“midrod” it will
hereafter be called) was carried through from end to end, though at the cost
of inconvenience in the placing of the machinery, in what may be called the
hull, which now became simply a protective case built around this midrod.
The mistaken device of the long shafts meeting at an angle, was, however,
retained, and the engines first tried were a pair of very light ones of crude
construction.
These were later replaced by a pair of oscillating engines, each 3 cm.
diameter by 3 cm. stroke, with a combined capacity of 42 cubic cm. and
without cut-off. The midrod was made of light steel tubing 2 cm. outside
diameter. The framing for the hull was formed by a single ring of U section,
8 cm. across and 18 cm. in depth, stayed by five ribs of wood measuring
0.7 × 0.3 cm. The inclined propeller shafts, which were connected by a pair
of bevel gears as in No. 0, were made of tubing 0.5 cm. outside diameter,
and were intended to turn propellers of from 40 to 45 cm. in diameter. The
weight, without engine or reservoir for gas, was 1161 grammes. With a
sprung and the worm was thrown out of gear. [p038]
I pass over numerous other experiments, for their only result was to make
it clear that the aerodrome, as it had been constructed, could not be made to
work efficiently, even if its great weight had not served as a bar to its flight.
It was, therefore, decided to proceed with the construction of another.
After the failure of the first steam-driven model No. 0, which has just
been described, subsequent light models were constructed. These, three in
number, made with a view to the employment of carbonic acid or
compressed air, but also to the possible use of steam, are shown in Plate 10,
Nos. 1, 2, 3; on the same scale as the larger model which had preceded
them. In describing these, it will be well to mention constructive features
which were experimented on in them, as well as to describe the engines
used.
In No. 1, which was intended to be on about 25 the linear scale of No. 0,
the constructive fault of the latter, that of making the support depend on a
too flexible hull, was avoided, and the straight steel tube (“midrod” it will
hereafter be called) was carried through from end to end, though at the cost
of inconvenience in the placing of the machinery, in what may be called the
hull, which now became simply a protective case built around this midrod.
The mistaken device of the long shafts meeting at an angle, was, however,
retained, and the engines first tried were a pair of very light ones of crude
construction.
These were later replaced by a pair of oscillating engines, each 3 cm.
diameter by 3 cm. stroke, with a combined capacity of 42 cubic cm. and
without cut-off. The midrod was made of light steel tubing 2 cm. outside
diameter. The framing for the hull was formed by a single ring of U section,
8 cm. across and 18 cm. in depth, stayed by five ribs of wood measuring
0.7 × 0.3 cm. The inclined propeller shafts, which were connected by a pair
of bevel gears as in No. 0, were made of tubing 0.5 cm. outside diameter,
and were intended to turn propellers of from 40 to 45 cm. in diameter. The
weight, without engine or reservoir for gas, was 1161 grammes. With a
Page 80
weight equivalent to that of the intended reservoir and engines plus that of
the proposed supporting surfaces, the whole weight, independent of fuel or
water, was 2.2 kilogrammes.
The engines, which were not strong enough to sustain a pressure of over
2 atmospheres, at an actual pressure of 20 pounds drove the 45 cm.
propellers through the long V shafts and lifted only about 17 of the flying
weight of the machine. The power developed at the Prony brake was
collectively only about .04 horse-power, giving 1200 turns a minute to two
40 cm. propellers. This was the best result obtained.
This aerodrome was completed in June, 1892, but changes in the engines
and other attempted improvements kept it under experiment until November
of that year, when it appeared to be inexpedient to do anything more with it.
Aerodrome No. 2 (see Plate 10), was a still smaller and still lighter
construction, in which, however, the midrod was bent (not clearly shown in
the [p039] photograph), so as to afford more room in the hull. This
introduced a constructional weakness which was not compensated by the
added convenience, but the principal improvement was the abandonment of
the inclined propeller shafts, which was done at the suggestion of Mr. J. E.
Watkins, so that the propellers were carried on parallel shafts as in marine
practice. These parallel shafts were driven by two very small engines with
cylinders 2.3 cm. in diameter by 4 cm. stroke, with a collective capacity of
33 cu. cm. and without cut-off, which were mounted on a cross-frame
attached to the midrod at right angles near the rear end of the hull.
These engines, driven either by steam or by carbonic-acid gas developed
0.035 horse-power at the Prony brake, giving 750 revolutions of the 45 cm.
propellers, and lifting about 15 of the total weight which it was necessary to
provide for in actual flight. A higher rate of revolution and a better lift were
occasionally obtained, but there was little more hope with this than with the
preceding models of obtaining power enough to support the actual weight in
flight, although such sacrifices had been made for lightness that every
portion of the little model had been reduced to what seemed the limit of
possible frailty consistent with anything like safety. Thus the midrod was
the proposed supporting surfaces, the whole weight, independent of fuel or
water, was 2.2 kilogrammes.
The engines, which were not strong enough to sustain a pressure of over
2 atmospheres, at an actual pressure of 20 pounds drove the 45 cm.
propellers through the long V shafts and lifted only about 17 of the flying
weight of the machine. The power developed at the Prony brake was
collectively only about .04 horse-power, giving 1200 turns a minute to two
40 cm. propellers. This was the best result obtained.
This aerodrome was completed in June, 1892, but changes in the engines
and other attempted improvements kept it under experiment until November
of that year, when it appeared to be inexpedient to do anything more with it.
Aerodrome No. 2 (see Plate 10), was a still smaller and still lighter
construction, in which, however, the midrod was bent (not clearly shown in
the [p039] photograph), so as to afford more room in the hull. This
introduced a constructional weakness which was not compensated by the
added convenience, but the principal improvement was the abandonment of
the inclined propeller shafts, which was done at the suggestion of Mr. J. E.
Watkins, so that the propellers were carried on parallel shafts as in marine
practice. These parallel shafts were driven by two very small engines with
cylinders 2.3 cm. in diameter by 4 cm. stroke, with a collective capacity of
33 cu. cm. and without cut-off, which were mounted on a cross-frame
attached to the midrod at right angles near the rear end of the hull.
These engines, driven either by steam or by carbonic-acid gas developed
0.035 horse-power at the Prony brake, giving 750 revolutions of the 45 cm.
propellers, and lifting about 15 of the total weight which it was necessary to
provide for in actual flight. A higher rate of revolution and a better lift were
occasionally obtained, but there was little more hope with this than with the
preceding models of obtaining power enough to support the actual weight in
flight, although such sacrifices had been made for lightness that every
portion of the little model had been reduced to what seemed the limit of
possible frailty consistent with anything like safety. Thus the midrod was
Page 81
lighter than that of No. 1, being only 1 cm. in outside diameter. The frame
was made of thin wooden strips 5 mm. × 3.5 mm., united by light steel
rings. The cross framing carrying the engines was also of wood, and was
formed of four strips, each 7 mm. × 3 mm. The shafts were but 4 mm. in
diameter.
As these engines did not give results that were satisfactory, when using
carbonic-acid gas, experiments were commenced to secure a boiler that
would furnish the requisite steam. As the “beehive” boiler had proved to be
too heavy, and as the steam obtained from it had been inadequate to the
requirements, something else had to be devised. A few of the boilers used in
1892 are shown in Fig. 3. The one marked A is one of the “beehives,” while
an element of another form tried is that marked B. It consisted of 38 -inch
copper tubes joined to a drum of 10-oz. copper. This was made in May,
1892, and was tested to a pressure of 50 atmospheres, when it burst without
any tearing of the metal.
In July another boiler like that shown at C in Fig. 3 was made. This was
formed of tubes 3 cm. in diameter, and weighed 348 grammes. It carried
about 300 grammes of water and stood a steam pressure of 125 pounds per
square inch, but failed to maintain sufficient steam pressure.
Accordingly, in the same month, a third boiler like that shown at D was
built. It consisted of a tube 12 inches long to which were attached fifteen
1
4
-inch tubes each 7 inches long, in the manner shown. The heating surface
of this boiler, including the tubes and the lower half of the drum, amounted
to 750 square cm., and it was thought that this would be sufficient to supply
steam for a flight of a [p040] minute and a half. But when a test was made, it
also was found to be deficient in steaming power even after changes were
made in it which occupied much time.
By the first of October, 1892, there had been built one large aerodrome
that could not possibly fly, a smaller one, No. 1, on 25 the linear scale of No.
0, with a pair of engines but no means of driving them, and the still smaller
No. 2 with a boiler that was yet untried.
was made of thin wooden strips 5 mm. × 3.5 mm., united by light steel
rings. The cross framing carrying the engines was also of wood, and was
formed of four strips, each 7 mm. × 3 mm. The shafts were but 4 mm. in
diameter.
As these engines did not give results that were satisfactory, when using
carbonic-acid gas, experiments were commenced to secure a boiler that
would furnish the requisite steam. As the “beehive” boiler had proved to be
too heavy, and as the steam obtained from it had been inadequate to the
requirements, something else had to be devised. A few of the boilers used in
1892 are shown in Fig. 3. The one marked A is one of the “beehives,” while
an element of another form tried is that marked B. It consisted of 38 -inch
copper tubes joined to a drum of 10-oz. copper. This was made in May,
1892, and was tested to a pressure of 50 atmospheres, when it burst without
any tearing of the metal.
In July another boiler like that shown at C in Fig. 3 was made. This was
formed of tubes 3 cm. in diameter, and weighed 348 grammes. It carried
about 300 grammes of water and stood a steam pressure of 125 pounds per
square inch, but failed to maintain sufficient steam pressure.
Accordingly, in the same month, a third boiler like that shown at D was
built. It consisted of a tube 12 inches long to which were attached fifteen
1
4
-inch tubes each 7 inches long, in the manner shown. The heating surface
of this boiler, including the tubes and the lower half of the drum, amounted
to 750 square cm., and it was thought that this would be sufficient to supply
steam for a flight of a [p040] minute and a half. But when a test was made, it
also was found to be deficient in steaming power even after changes were
made in it which occupied much time.
By the first of October, 1892, there had been built one large aerodrome
that could not possibly fly, a smaller one, No. 1, on 25 the linear scale of No.
0, with a pair of engines but no means of driving them, and the still smaller
No. 2 with a boiler that was yet untried.
Page 82
Aerodrome No. 3 (Plate 10) was an attempt to obtain better conditions
than had existed in the preceding model without any radical change except
that of moving the cross frame, which carried the engines and propellers,
nearer the front of the machine. Instead of the oscillatory engines used up to
this time, two stationary cylinder engines, each 2.4 cm. in diameter and 4
cm. stroke, having a combined capacity of 36 cu. cm. without cut-off were
employed for driving the propellers. The engines, though occasionally run
in trials with steam from a stationary boiler, were intended to be actuated
either by compressed air or carbonic-acid gas contained in a reservoir which
was not actually constructed, but whose weight was provisionally estimated
at 1 kilogramme. The weight of the aerodrome without this reservoir was
but 1050 grammes, including the estimated weight of the sustaining
surfaces, which consisted principally of two wings, each about 1 metre in
length by 30 cm. in breadth and which were in fact so slight in their
construction, that it is now certain that they could not have retained their
shape in actual flight.
The only trials made with this aerodrome, then, were in the shop, of
which it is sufficient to cite those of November 22, 1892, when under a
pressure of 30 pounds, the maximum which the engines would bear, two 50
cm. propellers were driven at 900 revolutions per minute, with an estimated
horse-power of 0.07, about 35 per cent of the weight of the whole machine
being lifted. This was a much more encouraging result than any which had
preceded, and indicated that it was possible to make an actual flight with
the aerodrome if the boilers could be ignored, the best result having been
obtained only with carbonic acid supplied without limit from a neighboring
ample reservoir.
This aerodrome was also tested while mounted upon a whirling-arm and
allowed to operate during its advance through the air. The conclusion
reached with it at the close of 1892, after a large part of the year passed in
experiments with carbonic-acid gas and compressed air, was that it was
necessary to revert to steam, and that whatever difficulties lay in the way,
some means must be found of getting sufficient power without the weight
which had proved prohibitory in No. 0.
than had existed in the preceding model without any radical change except
that of moving the cross frame, which carried the engines and propellers,
nearer the front of the machine. Instead of the oscillatory engines used up to
this time, two stationary cylinder engines, each 2.4 cm. in diameter and 4
cm. stroke, having a combined capacity of 36 cu. cm. without cut-off were
employed for driving the propellers. The engines, though occasionally run
in trials with steam from a stationary boiler, were intended to be actuated
either by compressed air or carbonic-acid gas contained in a reservoir which
was not actually constructed, but whose weight was provisionally estimated
at 1 kilogramme. The weight of the aerodrome without this reservoir was
but 1050 grammes, including the estimated weight of the sustaining
surfaces, which consisted principally of two wings, each about 1 metre in
length by 30 cm. in breadth and which were in fact so slight in their
construction, that it is now certain that they could not have retained their
shape in actual flight.
The only trials made with this aerodrome, then, were in the shop, of
which it is sufficient to cite those of November 22, 1892, when under a
pressure of 30 pounds, the maximum which the engines would bear, two 50
cm. propellers were driven at 900 revolutions per minute, with an estimated
horse-power of 0.07, about 35 per cent of the weight of the whole machine
being lifted. This was a much more encouraging result than any which had
preceded, and indicated that it was possible to make an actual flight with
the aerodrome if the boilers could be ignored, the best result having been
obtained only with carbonic acid supplied without limit from a neighboring
ample reservoir.
This aerodrome was also tested while mounted upon a whirling-arm and
allowed to operate during its advance through the air. The conclusion
reached with it at the close of 1892, after a large part of the year passed in
experiments with carbonic-acid gas and compressed air, was that it was
necessary to revert to steam, and that whatever difficulties lay in the way,
some means must be found of getting sufficient power without the weight
which had proved prohibitory in No. 0.
Page 83
With this chapter, then, and with the end of the year 1892, I close this
very brief account of between one and two years of fruitless experiment in
the construction of models supplied with various motors, subsequent to and
on a larger scale indeed than the toy-like ones of india rubber, but not even
so efficient as those had been, since they had never procured a single actual
flight.
very brief account of between one and two years of fruitless experiment in
the construction of models supplied with various motors, subsequent to and
on a larger scale indeed than the toy-like ones of india rubber, but not even
so efficient as those had been, since they had never procured a single actual
flight.
Page 84
[p041] ◊
CHAPTER V
ON SUSTAINING SURFACES
The following general considerations may conveniently precede the
particular description of the balancing of the aerodrome.
In “Experiments in Aerodynamics,” I have given the result of trials,
showing that the pressure (or total resistance) of a wind on a surface 1 foot
square, moving normally at the velocity of 1 foot per second, is 0.00166
pounds, and that this pressure increases directly as the surface of the plane,
and (within our experimental condition) as the square of the velocity,20
results in general accordance with those of earlier observers.
I have further shown by independent investigations that while the shape
of the plane is of secondary importance if its movement be normal, the
shape and “aspect” greatly affect the resultant pressure when the plane is
inclined at a small angle, and propelled by such a force that its flight is
horizontal, that is, under the actual conditions of soaring flight.
I have given on page 60 of “Aerodynamics,” the primary equations,
Pα = P90F (α) = kAV 2F (α),
W = Pα cos α = kAV 2F (α) cos α,
R = Pα sin α = kAV 2F (α) sin α,
where W is the weight of the plane under examination (sometimes called
the “lift”); R the horizontal component of pressure (sometimes called the
“drift”); k is the constant already given; A the area in square feet; V the
velocity in feet per second; F a function of α (to be determined by
experiment); α the angle which, under these conditions, gives horizontal
flight.
I have also given on page 66 of the same work the following table
showing the actual values obtained by experiment on a plane, 30 × 4.8
inches (= 1 sq. ft.), weighing 500 grammes (1.1 pounds):
CHAPTER V
ON SUSTAINING SURFACES
The following general considerations may conveniently precede the
particular description of the balancing of the aerodrome.
In “Experiments in Aerodynamics,” I have given the result of trials,
showing that the pressure (or total resistance) of a wind on a surface 1 foot
square, moving normally at the velocity of 1 foot per second, is 0.00166
pounds, and that this pressure increases directly as the surface of the plane,
and (within our experimental condition) as the square of the velocity,20
results in general accordance with those of earlier observers.
I have further shown by independent investigations that while the shape
of the plane is of secondary importance if its movement be normal, the
shape and “aspect” greatly affect the resultant pressure when the plane is
inclined at a small angle, and propelled by such a force that its flight is
horizontal, that is, under the actual conditions of soaring flight.
I have given on page 60 of “Aerodynamics,” the primary equations,
Pα = P90F (α) = kAV 2F (α),
W = Pα cos α = kAV 2F (α) cos α,
R = Pα sin α = kAV 2F (α) sin α,
where W is the weight of the plane under examination (sometimes called
the “lift”); R the horizontal component of pressure (sometimes called the
“drift”); k is the constant already given; A the area in square feet; V the
velocity in feet per second; F a function of α (to be determined by
experiment); α the angle which, under these conditions, gives horizontal
flight.
I have also given on page 66 of the same work the following table
showing the actual values obtained by experiment on a plane, 30 × 4.8
inches (= 1 sq. ft.), weighing 500 grammes (1.1 pounds):
Page 85
Weight with planes of
Horiz-
Work expended like form that 1 horse-
Angle Soaring speed ontal
per minute power will drive
with V. pres-
60 RV. through the air at
horizon sure R.
velocity V.
α.
Kgm- Foot-
Metres per sec. Feet per sec. Gm. Kgm. Pounds.
metres. pounds.
45° 11.2 36.7 500 336 2,434 6.8 15
30 10.6 34.8 275 175 1,268 13.0 29
15 11.2 36.7 128 86 623 26.5 58
10 12.4 40.7 88 65 474 34.8 77
5 15.2 49.8 45 41 297 55.5 122
2 20.0 65.6 20 24 174 95.0 209
[p042]
It cannot be too clearly kept in mind that these values refer to horizontal
flight, and that for this the weight, the work, the area, the angle and the
velocity are inseparably connected by the formulæ already given.
It is to be constantly remembered also, that they apply to results obtained
under almost perfect theoretical conditions as regards not only the
maintenance of equilibrium and horizontality, but also the rigid
maintenance of the angle α and the comparative absence of friction, and
that these conditions are especially “theoretical” in their exclusion of the
internal work of the wind observable in experiments made in the open wind.
E XPERIMENTS IN THE O PEN W IND
I have pointed out21 that an indefinite source of power for the
maintenance of mechanical flight, lies in what I have called the “internal
work” of the wind. It is easy to see that the actual effect of the free wind,
which is filled with almost infinitely numerous and incessant changes of
velocity and direction, must differ widely from that of a uniform wind such
as mathematicians and physicists have almost invariably contemplated in
their discussions.
Now the artificial wind produced by the whirling-table differs from the
real wind not only in being caused by the advancing object, whose direction
is not strictly linear, and in other comparatively negligible particulars, but
especially in this, that in spite of little artificial currents the movement on
Horiz-
Work expended like form that 1 horse-
Angle Soaring speed ontal
per minute power will drive
with V. pres-
60 RV. through the air at
horizon sure R.
velocity V.
α.
Kgm- Foot-
Metres per sec. Feet per sec. Gm. Kgm. Pounds.
metres. pounds.
45° 11.2 36.7 500 336 2,434 6.8 15
30 10.6 34.8 275 175 1,268 13.0 29
15 11.2 36.7 128 86 623 26.5 58
10 12.4 40.7 88 65 474 34.8 77
5 15.2 49.8 45 41 297 55.5 122
2 20.0 65.6 20 24 174 95.0 209
[p042]
It cannot be too clearly kept in mind that these values refer to horizontal
flight, and that for this the weight, the work, the area, the angle and the
velocity are inseparably connected by the formulæ already given.
It is to be constantly remembered also, that they apply to results obtained
under almost perfect theoretical conditions as regards not only the
maintenance of equilibrium and horizontality, but also the rigid
maintenance of the angle α and the comparative absence of friction, and
that these conditions are especially “theoretical” in their exclusion of the
internal work of the wind observable in experiments made in the open wind.
E XPERIMENTS IN THE O PEN W IND
I have pointed out21 that an indefinite source of power for the
maintenance of mechanical flight, lies in what I have called the “internal
work” of the wind. It is easy to see that the actual effect of the free wind,
which is filled with almost infinitely numerous and incessant changes of
velocity and direction, must differ widely from that of a uniform wind such
as mathematicians and physicists have almost invariably contemplated in
their discussions.
Now the artificial wind produced by the whirling-table differs from the
real wind not only in being caused by the advancing object, whose direction
is not strictly linear, and in other comparatively negligible particulars, but
especially in this, that in spite of little artificial currents the movement on
Page 86
the whole is regular and uniform to a degree strikingly in contrast with that
of the open wind in nature.
In a note to the French edition of my work, I have called the attention of
the reader to the fact that the figures given in the Smithsonian publication
can show only a small part of the virtual work of the wind, while the plane,
which is used for simplicity of exposition, is not the most advantageous
form for flight; so that, as I go on to state, the realization of the actually
successful aerodrome must take account of the more complex conditions
actually existing in nature, which were only alluded to in the memoir,
whose object was to bring to attention the little considered importance of
the then almost unobserved and unstudied minute fluctuations which
constitute the internal work of the wind. I added that I might later publish
some experimental investigations on the superior efficiency of the real wind
over that artificially created. The experiments which were thus alluded to in
1893, were sufficient to indicate the importance of the subject, but the data
have not been preserved.
What immediately follows refers, it will be observed, more particularly
to the work of the whirling-table. [p043]
R ELATION OF A REA TO W EIGHT AND P OWER
In order to get a more precise idea of the character of the alteration
introduced into these theoretical conditions by the variation of any of them,
let us, still confining ourselves to the use of the whirling-table, suppose that
the plane in question while possessing the same weight, shape, and angle of
inclination, were to have its area increased, and to fix our ideas, we will
suppose that it became 4 square feet instead of 1 as before. Then, from what
has already been said, V, the velocity, must vary inversely as the square root
of the area; that is, it must, under the given condition, become one-half of
what it had been, for if V did not alter, the impelling force continuing the
same, the plane would rise and its flight no longer be horizontal, unless the
weight, now supposed to be constant, were itself increased so as to restore
horizontality.
of the open wind in nature.
In a note to the French edition of my work, I have called the attention of
the reader to the fact that the figures given in the Smithsonian publication
can show only a small part of the virtual work of the wind, while the plane,
which is used for simplicity of exposition, is not the most advantageous
form for flight; so that, as I go on to state, the realization of the actually
successful aerodrome must take account of the more complex conditions
actually existing in nature, which were only alluded to in the memoir,
whose object was to bring to attention the little considered importance of
the then almost unobserved and unstudied minute fluctuations which
constitute the internal work of the wind. I added that I might later publish
some experimental investigations on the superior efficiency of the real wind
over that artificially created. The experiments which were thus alluded to in
1893, were sufficient to indicate the importance of the subject, but the data
have not been preserved.
What immediately follows refers, it will be observed, more particularly
to the work of the whirling-table. [p043]
R ELATION OF A REA TO W EIGHT AND P OWER
In order to get a more precise idea of the character of the alteration
introduced into these theoretical conditions by the variation of any of them,
let us, still confining ourselves to the use of the whirling-table, suppose that
the plane in question while possessing the same weight, shape, and angle of
inclination, were to have its area increased, and to fix our ideas, we will
suppose that it became 4 square feet instead of 1 as before. Then, from what
has already been said, V, the velocity, must vary inversely as the square root
of the area; that is, it must, under the given condition, become one-half of
what it had been, for if V did not alter, the impelling force continuing the
same, the plane would rise and its flight no longer be horizontal, unless the
weight, now supposed to be constant, were itself increased so as to restore
horizontality.
Page 87
I have repeated Table XIII under the condition that the area be
quadrupled, while all the other conditions remain constant, except the
soaring speed, which must vary.
Work. Weight.
Weight of like planes
Soaring speed (feet per Work expended per minute.
which 1 H.P. will drive
α second) A=4 sq.ft.
through the air with
V′. W=500gr. = 1.1lbs.
velocity V′.
Foot-pounds. Pounds.
45° 18.4 1,217 30
30 17.4 634 57
15 18.4 312 116
10 20.4 237 154
5 24.9 148 244
2 32.8 87 418
W is the weight of the single plane; A is the area; R is the horizontal “drift.” Wt is the weight
of like planes which 1 H. P. will drive at velocity V. Work is RV.
1
I. If Work is constant, R varies as A . II. If R is constant, Work varies as . III. If W
A
is constant while A varies, the weight which 1 H. P. will support varies as √A .
The reader is reminded that these are simply deductions from the
equations given in “Aerodynamics,” and that these deductions have not
been verified by direct trial, such as would show that no new conditions
have in fact been introduced in this new application. While, however, these
deductions cannot convey any confidence beyond what is warranted by the
original experiments, in their general trustworthiness as working formulæ at
this stage of the investigations, we may, I think, feel confidence.
I may, in view of its importance, repeat my remark that the relation of
area and weight which obtain in practice, will depend upon yet other than
these theoretical considerations, for, as the flight of the free aerodrome
cannot be expected to be exactly horizontal nor maintained at any constant
small angle, the [p044] data of “Aerodynamics” (obtained in constrained
horizontal flight with the whirling-table) are here insufficient. They are
insufficient also because these values are obtained with small rigid planes,
while the surfaces we are now to use cannot be made rigid under the
quadrupled, while all the other conditions remain constant, except the
soaring speed, which must vary.
Work. Weight.
Weight of like planes
Soaring speed (feet per Work expended per minute.
which 1 H.P. will drive
α second) A=4 sq.ft.
through the air with
V′. W=500gr. = 1.1lbs.
velocity V′.
Foot-pounds. Pounds.
45° 18.4 1,217 30
30 17.4 634 57
15 18.4 312 116
10 20.4 237 154
5 24.9 148 244
2 32.8 87 418
W is the weight of the single plane; A is the area; R is the horizontal “drift.” Wt is the weight
of like planes which 1 H. P. will drive at velocity V. Work is RV.
1
I. If Work is constant, R varies as A . II. If R is constant, Work varies as . III. If W
A
is constant while A varies, the weight which 1 H. P. will support varies as √A .
The reader is reminded that these are simply deductions from the
equations given in “Aerodynamics,” and that these deductions have not
been verified by direct trial, such as would show that no new conditions
have in fact been introduced in this new application. While, however, these
deductions cannot convey any confidence beyond what is warranted by the
original experiments, in their general trustworthiness as working formulæ at
this stage of the investigations, we may, I think, feel confidence.
I may, in view of its importance, repeat my remark that the relation of
area and weight which obtain in practice, will depend upon yet other than
these theoretical considerations, for, as the flight of the free aerodrome
cannot be expected to be exactly horizontal nor maintained at any constant
small angle, the [p044] data of “Aerodynamics” (obtained in constrained
horizontal flight with the whirling-table) are here insufficient. They are
insufficient also because these values are obtained with small rigid planes,
while the surfaces we are now to use cannot be made rigid under the
Page 88
necessary requirements of weight, without the use of guy wires and other
adjuncts which introduce head resistance.
Against all these unfavorable conditions we have the favoring one that,
other things being equal, somewhat more efficiency can be obtained with
suitable curved surfaces than with planes.22
I have made numerous experiments with curves of various forms upon
the whirling-table, and constructed many such supporting surfaces, some of
which have been tested in actual flight. It might be expected that fuller
results from these experiments should be given than those now presented
here, but I am not yet prepared to offer any more detailed evidence at
present for the performance of curved surfaces than will be found in Part
III.23 I do not question that curves are in some degree more efficient, but the
extreme increase of efficiency in curves over planes understood to be
asserted by Lilienthal and by Wellner, appears to have been associated
either with some imperfect enunciation of conditions which gave little more
than an apparent advantage, or with conditions nearly impossible for us to
obtain in actual flight.
All these circumstances considered, we may anticipate that the power
required (or the proportion of supporting area to weight) will be very much
greater in actual than in theoretical (that is, in constrained horizontal) flight,
and the early experiments with rubber-driven models were in fact successful
only when there were from three to four feet of sustaining surface to a
pound of weight. When such a relatively large area is sought in a large
aerodrome, the construction of light, yet rigid, supporting surfaces becomes
a nearly insuperable difficulty, and this must be remembered as
consequently affecting the question of the construction of boiler, engines
and hulls, whose weight cannot be increased without increasing the wing
area.
adjuncts which introduce head resistance.
Against all these unfavorable conditions we have the favoring one that,
other things being equal, somewhat more efficiency can be obtained with
suitable curved surfaces than with planes.22
I have made numerous experiments with curves of various forms upon
the whirling-table, and constructed many such supporting surfaces, some of
which have been tested in actual flight. It might be expected that fuller
results from these experiments should be given than those now presented
here, but I am not yet prepared to offer any more detailed evidence at
present for the performance of curved surfaces than will be found in Part
III.23 I do not question that curves are in some degree more efficient, but the
extreme increase of efficiency in curves over planes understood to be
asserted by Lilienthal and by Wellner, appears to have been associated
either with some imperfect enunciation of conditions which gave little more
than an apparent advantage, or with conditions nearly impossible for us to
obtain in actual flight.
All these circumstances considered, we may anticipate that the power
required (or the proportion of supporting area to weight) will be very much
greater in actual than in theoretical (that is, in constrained horizontal) flight,
and the early experiments with rubber-driven models were in fact successful
only when there were from three to four feet of sustaining surface to a
pound of weight. When such a relatively large area is sought in a large
aerodrome, the construction of light, yet rigid, supporting surfaces becomes
a nearly insuperable difficulty, and this must be remembered as
consequently affecting the question of the construction of boiler, engines
and hulls, whose weight cannot be increased without increasing the wing
area.
Page 89
[p045] ◊
CHAPTER VI
BALANCING THE AERODROME
By “balancing” I mean such an adjustment of the mean center of pressure
of the supporting surfaces with reference to the center of gravity and to the
line of thrust, that for a given speed the aerodrome will be in equilibrium,
and will maintain steady horizontal flight. “Balance” and “equilibrium” as
here used are nearly convertible terms.
L ATERAL S TABILITY
Equilibrium may be considered with reference to lateral or longitudinal
stability. The lateral part is approximately secured with comparative ease,
by imitating Nature’s plan, and setting the wings at a diedral angle, which I
have usually made 150°. Stability in this sense cannot be secured in what at
first seems an obvious way—by putting a considerable weight in the central
plane and far below the center of gravity of the aerodrome proper, for this
introduces rolling. Thence ensues the necessity of carrying the center of
gravity more nearly up to the center of pressure than would otherwise be
necessary, and so far introducing conditions which tend to instability, but
which seem to be imposed upon us by the circumstances of actual flight.
With these brief considerations concerning lateral stability, I pass on to the
far more difficult subject of longitudinal stability.
L ONGITUDINAL S TABILITY
My most primitive observation with small gliding models was of the fact
that greater stability was obtained with two pairs of wings, one behind the
other, than with one pair (greater, that is, in the absence of any instinctive
power of adjustment).
This is connected with the fact that the upward pressure of the air upon
both pairs may be resolved into a single point which I will call the “center
of pressure,” and which, in stable flight, should (apart from the disturbance
by the propeller thrust) be over the center of gravity. The center of pressure
CHAPTER VI
BALANCING THE AERODROME
By “balancing” I mean such an adjustment of the mean center of pressure
of the supporting surfaces with reference to the center of gravity and to the
line of thrust, that for a given speed the aerodrome will be in equilibrium,
and will maintain steady horizontal flight. “Balance” and “equilibrium” as
here used are nearly convertible terms.
L ATERAL S TABILITY
Equilibrium may be considered with reference to lateral or longitudinal
stability. The lateral part is approximately secured with comparative ease,
by imitating Nature’s plan, and setting the wings at a diedral angle, which I
have usually made 150°. Stability in this sense cannot be secured in what at
first seems an obvious way—by putting a considerable weight in the central
plane and far below the center of gravity of the aerodrome proper, for this
introduces rolling. Thence ensues the necessity of carrying the center of
gravity more nearly up to the center of pressure than would otherwise be
necessary, and so far introducing conditions which tend to instability, but
which seem to be imposed upon us by the circumstances of actual flight.
With these brief considerations concerning lateral stability, I pass on to the
far more difficult subject of longitudinal stability.
L ONGITUDINAL S TABILITY
My most primitive observation with small gliding models was of the fact
that greater stability was obtained with two pairs of wings, one behind the
other, than with one pair (greater, that is, in the absence of any instinctive
power of adjustment).
This is connected with the fact that the upward pressure of the air upon
both pairs may be resolved into a single point which I will call the “center
of pressure,” and which, in stable flight, should (apart from the disturbance
by the propeller thrust) be over the center of gravity. The center of pressure
Page 90
in an advancing inclined plane in soaring flight is, as I have shown in
“Aerodynamics,” and as is otherwise well known, always in advance of the
center of figure, and moves forward as the angle of inclination of the
sustaining surfaces diminishes, and, to a less extent, as horizontal flight
increases in velocity. These facts furnish the elementary ideas necessary in
discussing this problem of equilibrium, whose solution is of the most vital
importance in successful flight. [p046]
The solution would be comparatively simple if the position of the CP
could be accurately known beforehand, but how difficult the solution is may
be realized from a consideration of one of the facts just stated, namely, that
the position of the center of pressure in horizontal flight shifts with the
velocity of the flight itself, much as though in marine navigation the trim of
a steamboat’s hull were to be completely altered at every change of speed.
It may be remarked here that the center of pressure, from the symmetry of
the aerodrome, necessarily lies in the vertical medial plane, but it may be
considered with reference to its position either in the plane XY (cp1) or in
the plane YZ (cp2). The latter center of pressure, as referred to in the plane
YZ, is here approximately calculated on the assumption that it lies in the
intersection of this vertical plane by a horizontal one passing through the
wings half way from root to tip.
Experiments made in Washington, later than those given in
“Aerodynamics,” show that the center of pressure, (cp1) on a plane at slight
angles of inclination, may be at least as far forward as one-sixth the width
from the front edge. From these later experiments it appears probable also
that the center of pressure moves forward for an increased speed even when
there has been no perceptible diminution of the angle of the plane with the
horizon, but these considerations are of little value as applied to curved
wings such as are here used. Some observations of a very general nature
may, however, be made with regard to the position of the wings and tail.
In the case where there are two pairs of wings, one following the other,
the rear pair is less efficient in an indefinite degree than the front, but the
action of the wings is greatly modified by their position with reference to
“Aerodynamics,” and as is otherwise well known, always in advance of the
center of figure, and moves forward as the angle of inclination of the
sustaining surfaces diminishes, and, to a less extent, as horizontal flight
increases in velocity. These facts furnish the elementary ideas necessary in
discussing this problem of equilibrium, whose solution is of the most vital
importance in successful flight. [p046]
The solution would be comparatively simple if the position of the CP
could be accurately known beforehand, but how difficult the solution is may
be realized from a consideration of one of the facts just stated, namely, that
the position of the center of pressure in horizontal flight shifts with the
velocity of the flight itself, much as though in marine navigation the trim of
a steamboat’s hull were to be completely altered at every change of speed.
It may be remarked here that the center of pressure, from the symmetry of
the aerodrome, necessarily lies in the vertical medial plane, but it may be
considered with reference to its position either in the plane XY (cp1) or in
the plane YZ (cp2). The latter center of pressure, as referred to in the plane
YZ, is here approximately calculated on the assumption that it lies in the
intersection of this vertical plane by a horizontal one passing through the
wings half way from root to tip.
Experiments made in Washington, later than those given in
“Aerodynamics,” show that the center of pressure, (cp1) on a plane at slight
angles of inclination, may be at least as far forward as one-sixth the width
from the front edge. From these later experiments it appears probable also
that the center of pressure moves forward for an increased speed even when
there has been no perceptible diminution of the angle of the plane with the
horizon, but these considerations are of little value as applied to curved
wings such as are here used. Some observations of a very general nature
may, however, be made with regard to the position of the wings and tail.
In the case where there are two pairs of wings, one following the other,
the rear pair is less efficient in an indefinite degree than the front, but the
action of the wings is greatly modified by their position with reference to
Page 91
the propellers, and from so many other causes, that, as a result of a great
deal of experiment, it seems almost impossible at this time to lay down any
absolute rule with regard to the center of pressure of any pair of curved
wings used in practice.
Later experiments conducted under my direction by Mr. E. C. Huffaker,
some of which will appear in Part III, indicate that upon the curved surfaces
I employed, the center of pressure moves forward with an increase in the
(small) angle of elevation, and backward with a decrease, so that it may lie
even behind the center of the surface. Since for some surfaces the center of
pressure moves backward, and for others forward, it would seem that there
might be some other surface for which it will be fixed. Such a surface in
fact appears to exist in the wing of the soaring bird. These experiments have
been chiefly with rigid surfaces, and though some have been made with
elastic rear surfaces, these have not been carried far enough to give positive
results.
The curved wings used on the aerodromes in late years have a rise of one
in twelve, or in some cases of one in eighteen,24 and for these latter the
following empirical local rule has been adopted: [p047]
The center of pressure on each wing with a horizontal motion of 2000 feet per minute, is two-
fifths of the distance from front to rear. Where there are two pairs of wings of equal size, one
following the other, and placed at such a distance apart and with such a relation to the propellers as
here used, the following wing is assumed to have two-thirds of the efficiency of the leader per unit
of surface. If it is half the size of the leader, the efficiency is assumed to be one-half per unit of
surface. If it is half as large again as the leader, its efficiency is assumed to be eight-tenths per unit
of surface. For intermediate sizes of following wing, intermediate values of the efficiency may be
assumed.
These rules are purely empirical and only approximate. As
approximations, they are useful in giving a preliminary balance, but the
exact position of the center of pressure is rarely determinable in either the
horizontal or vertical plane, except by experiment in actual flight. The
position of the center of gravity is found with all needed precision by
suspending the aerodrome by a plumb-line in two positions, and noting the
point of intersection of the traces of the line, and this method is so superior
deal of experiment, it seems almost impossible at this time to lay down any
absolute rule with regard to the center of pressure of any pair of curved
wings used in practice.
Later experiments conducted under my direction by Mr. E. C. Huffaker,
some of which will appear in Part III, indicate that upon the curved surfaces
I employed, the center of pressure moves forward with an increase in the
(small) angle of elevation, and backward with a decrease, so that it may lie
even behind the center of the surface. Since for some surfaces the center of
pressure moves backward, and for others forward, it would seem that there
might be some other surface for which it will be fixed. Such a surface in
fact appears to exist in the wing of the soaring bird. These experiments have
been chiefly with rigid surfaces, and though some have been made with
elastic rear surfaces, these have not been carried far enough to give positive
results.
The curved wings used on the aerodromes in late years have a rise of one
in twelve, or in some cases of one in eighteen,24 and for these latter the
following empirical local rule has been adopted: [p047]
The center of pressure on each wing with a horizontal motion of 2000 feet per minute, is two-
fifths of the distance from front to rear. Where there are two pairs of wings of equal size, one
following the other, and placed at such a distance apart and with such a relation to the propellers as
here used, the following wing is assumed to have two-thirds of the efficiency of the leader per unit
of surface. If it is half the size of the leader, the efficiency is assumed to be one-half per unit of
surface. If it is half as large again as the leader, its efficiency is assumed to be eight-tenths per unit
of surface. For intermediate sizes of following wing, intermediate values of the efficiency may be
assumed.
These rules are purely empirical and only approximate. As
approximations, they are useful in giving a preliminary balance, but the
exact position of the center of pressure is rarely determinable in either the
horizontal or vertical plane, except by experiment in actual flight. The
position of the center of gravity is found with all needed precision by
suspending the aerodrome by a plumb-line in two positions, and noting the
point of intersection of the traces of the line, and this method is so superior
Page 92
to that by calculation, that it will probably continue in use even for much
larger constructions than the present.
The principal factor in the adjustment is the position of the wings with
reference to the center of gravity, but the aerodrome is moved forward by
the thrust of its propellers, and we must next recall the fact of experiment
that as it is for constructional reasons difficult to bring the thrust line in the
plane of the center of pressure of the wings, it is in practice sufficiently
below them to tend to tip the front of the aerodrome upward, so that it may
be that equilibrium will be attained only when CP1 is not over CG1.
In the discussion of the equilibrium, then, we must consider also the
effect of thrust, and usually assume that this thrust-line is at some
appreciable distance below the center of pressure.
We may conveniently consider two cases:
1. That the center of pressure is not directly over the center of gravity;
that is, CG1−CP1 = a, and estimate what the value of a should be in order
that, during horizontal flight, the aerodrome itself shall be horizontal; or,
[p048]
2. Consider that the center of pressure is directly over the center of
gravity (CP1−CG1 = 0), and in this case inquire what angle the aerodrome
itself may take during horizontal flight.
First case. The diagram (Fig. 4) represents the resultants of the separate
system of forces acting on the aerodrome, and these resultants will lie in a
vertical medial plane from the symmetry of their disposition.
Let af represent the resultant of the vertical components of the pressure
on the wings; the horizontal component will lie in the line ae.
larger constructions than the present.
The principal factor in the adjustment is the position of the wings with
reference to the center of gravity, but the aerodrome is moved forward by
the thrust of its propellers, and we must next recall the fact of experiment
that as it is for constructional reasons difficult to bring the thrust line in the
plane of the center of pressure of the wings, it is in practice sufficiently
below them to tend to tip the front of the aerodrome upward, so that it may
be that equilibrium will be attained only when CP1 is not over CG1.
In the discussion of the equilibrium, then, we must consider also the
effect of thrust, and usually assume that this thrust-line is at some
appreciable distance below the center of pressure.
We may conveniently consider two cases:
1. That the center of pressure is not directly over the center of gravity;
that is, CG1−CP1 = a, and estimate what the value of a should be in order
that, during horizontal flight, the aerodrome itself shall be horizontal; or,
[p048]
2. Consider that the center of pressure is directly over the center of
gravity (CP1−CG1 = 0), and in this case inquire what angle the aerodrome
itself may take during horizontal flight.
First case. The diagram (Fig. 4) represents the resultants of the separate
system of forces acting on the aerodrome, and these resultants will lie in a
vertical medial plane from the symmetry of their disposition.
Let af represent the resultant of the vertical components of the pressure
on the wings; the horizontal component will lie in the line ae.
Page 93
FIG. 4. Diagram showing relation under certain conditions of
thrust, C. P. and C. G.
Let the center of gravity be in the line bd, and the resultant thrust of the
propellers be represented by cd.
Let W = weight of aerodrome.
Let T = thrust of propellers.
Then if we neglect the horizontal hull resistance, which is small in
comparison with the weight, equilibrium obtains when W × ab = T × bd.
Second case. The diagram (Fig. 5) represents the same system of forces
as Fig. 4, but in this case the point of support is directly over the center of
gravity g, when the axis of the aerodrome is horizontal.
Let W = weight of aerodrome.
Let T = thrust of propellers.
Let R = distance of CG2 below CP2 = ag.
Let S = distance of thrust-line below CP2 = ad.
If now the aerodrome under the action of the propellers be supposed to
turn about the CP2 (or, a ) through an angle α, so that g takes the position g′,
thrust, C. P. and C. G.
Let the center of gravity be in the line bd, and the resultant thrust of the
propellers be represented by cd.
Let W = weight of aerodrome.
Let T = thrust of propellers.
Then if we neglect the horizontal hull resistance, which is small in
comparison with the weight, equilibrium obtains when W × ab = T × bd.
Second case. The diagram (Fig. 5) represents the same system of forces
as Fig. 4, but in this case the point of support is directly over the center of
gravity g, when the axis of the aerodrome is horizontal.
Let W = weight of aerodrome.
Let T = thrust of propellers.
Let R = distance of CG2 below CP2 = ag.
Let S = distance of thrust-line below CP2 = ad.
If now the aerodrome under the action of the propellers be supposed to
turn about the CP2 (or, a ) through an angle α, so that g takes the position g′,
Page 94
we [p049] obtain by the decomposition of the force of gravity an element
g′k = W sin α which acts in a direction parallel to the thrust-line.
If we again neglect the horizontal hull resistance, equilibrium will be
obtained when
kg′ × ag′ = T × ad′
or WR sin α = TS
TS
∴ α = sin−1 WR
Fig. 5. Diagram showing relation under certain conditions of
thrust, C. P. and C. G.
The practical application of these rules is greatly limited by the
uncertainty that attaches to the actual position of the center of pressure, and
this fact and also the numerical values involved may be illustrated by
examples.
C ONDITION OF A ERODROME N O. 6 , N OVEMBER 2 8, 18 96
g′k = W sin α which acts in a direction parallel to the thrust-line.
If we again neglect the horizontal hull resistance, equilibrium will be
obtained when
kg′ × ag′ = T × ad′
or WR sin α = TS
TS
∴ α = sin−1 WR
Fig. 5. Diagram showing relation under certain conditions of
thrust, C. P. and C. G.
The practical application of these rules is greatly limited by the
uncertainty that attaches to the actual position of the center of pressure, and
this fact and also the numerical values involved may be illustrated by
examples.
C ONDITION OF A ERODROME N O. 6 , N OVEMBER 2 8, 18 96
Page 95
The weight was 12.5 kilos. On November 28, the steam pressure was less
than 100 pounds, and the thrust may be taken at 4.5 kilos. The distance bd
was 25 cm.
Hence 12.5 × ab = 4.5 x 25 cm.
ab = 9 cm.
This appears to give the position of CP1, but CP1 is a resultant of the
pressure on both wings, and its position is determined by the empirical rule
just cited. We [p050] cannot tell in fact, then, with exactness how to adjust
the wings so that CG1−CP1 may be 9 cm., and equilibrium was in fact
obtained in flight when (the empirically determined) CG1−CP1 = 3 cm.
Again, let it be supposed that CP1 was really over CG1 . . . . The distance
of the center of gravity below the center of pressure is 43 cm. = R.
Then 4.5 × 25
α = sin−1 12.5 × 43
= 12° nearly.
The doubt as to the actual position of the resultant center of pressure, then,
renders the application of the rule uncertain. In practice, we are compelled
(unfortunately) after first calculating the balance, by such rules as the
above, and after it has been thus found with approximate correctness, to try
a preliminary flight. Having witnessed the actual conditions of flight, we
must then readjust the position of the wings with reference to the center of
gravity, arbitrarily, within the range which is necessary. This readjustment
should be small.
FIG. 6. Diagram showing effect of Pénaud tail.
In the preceding discussion it has been assumed that, if there is a flat tail
or horizontal rudder, it supports no portion of the weight. This is not an
indispensable condition but it is very convenient, and we shall assume it. In
than 100 pounds, and the thrust may be taken at 4.5 kilos. The distance bd
was 25 cm.
Hence 12.5 × ab = 4.5 x 25 cm.
ab = 9 cm.
This appears to give the position of CP1, but CP1 is a resultant of the
pressure on both wings, and its position is determined by the empirical rule
just cited. We [p050] cannot tell in fact, then, with exactness how to adjust
the wings so that CG1−CP1 may be 9 cm., and equilibrium was in fact
obtained in flight when (the empirically determined) CG1−CP1 = 3 cm.
Again, let it be supposed that CP1 was really over CG1 . . . . The distance
of the center of gravity below the center of pressure is 43 cm. = R.
Then 4.5 × 25
α = sin−1 12.5 × 43
= 12° nearly.
The doubt as to the actual position of the resultant center of pressure, then,
renders the application of the rule uncertain. In practice, we are compelled
(unfortunately) after first calculating the balance, by such rules as the
above, and after it has been thus found with approximate correctness, to try
a preliminary flight. Having witnessed the actual conditions of flight, we
must then readjust the position of the wings with reference to the center of
gravity, arbitrarily, within the range which is necessary. This readjustment
should be small.
FIG. 6. Diagram showing effect of Pénaud tail.
In the preceding discussion it has been assumed that, if there is a flat tail
or horizontal rudder, it supports no portion of the weight. This is not an
indispensable condition but it is very convenient, and we shall assume it. In
Page 96
this case the action of the so-called Pénaud rudder becomes easily
intelligible. This is a device, already referred to in Chapter II ◊, made by
Alphonse Pénaud for the automatic regulation of horizontal flight, and it is
as beautiful as it is simple.
Let AB (Fig. 6) be a schematic representation of an aerodrome whose
supporting surface is Bb, and let it be inclined to the horizon at such an
angle α that its course at a given speed may be horizontal. So far it does not
appear that, if the aerodrome be disturbed from this horizontal course, there
is any self-regulating power which could restore it to its original course; but
now let there be added a flat tail AC set at an angle −α with the wing. This
tail serves simply for direction, and not for the support of the aerodrome,
which, as already stated, is balanced so that the CG comes under the CP of
the wing Bb.
It will be seen on a simple inspection that the tail under the given
conditions is horizontal, and that, presenting its edge to the wind of
advance, it offers no resistance to it, so that if the front rises and the angle α
increases, the wind will strike on the under side of the tail and thereby tend
to raise the rear and depress [p051] the front again. If the angle α diminish, so
that the front drops, the wind will strike the upper surface of the tail, and
equally restore the angle α to the amount which is requisite to give
horizontal flight. If the angle α is not chosen originally with reference to the
speed so as to give horizontal flight, the device will still tend to continue the
flight in the straight line which the conditions impose, whether that be
horizontal or not.
From this description of its action, it will be seen that the Pénaud tail has
the disadvantage of giving an undulatory flight, if the tail is made rigid.
This objection, however, can be easily overcome by giving to it a certain
amount of elasticity. It does not appear that Pénaud gave much attention to
this feature, but stress is laid upon it in the article “Flight,” in the ninth
edition of the Encyclopædia Britannica, and I have introduced a simple
device for securing it.
The complete success of the device implies a strictly uniform velocity
and other conditions which cannot well he fulfilled in practice.
intelligible. This is a device, already referred to in Chapter II ◊, made by
Alphonse Pénaud for the automatic regulation of horizontal flight, and it is
as beautiful as it is simple.
Let AB (Fig. 6) be a schematic representation of an aerodrome whose
supporting surface is Bb, and let it be inclined to the horizon at such an
angle α that its course at a given speed may be horizontal. So far it does not
appear that, if the aerodrome be disturbed from this horizontal course, there
is any self-regulating power which could restore it to its original course; but
now let there be added a flat tail AC set at an angle −α with the wing. This
tail serves simply for direction, and not for the support of the aerodrome,
which, as already stated, is balanced so that the CG comes under the CP of
the wing Bb.
It will be seen on a simple inspection that the tail under the given
conditions is horizontal, and that, presenting its edge to the wind of
advance, it offers no resistance to it, so that if the front rises and the angle α
increases, the wind will strike on the under side of the tail and thereby tend
to raise the rear and depress [p051] the front again. If the angle α diminish, so
that the front drops, the wind will strike the upper surface of the tail, and
equally restore the angle α to the amount which is requisite to give
horizontal flight. If the angle α is not chosen originally with reference to the
speed so as to give horizontal flight, the device will still tend to continue the
flight in the straight line which the conditions impose, whether that be
horizontal or not.
From this description of its action, it will be seen that the Pénaud tail has
the disadvantage of giving an undulatory flight, if the tail is made rigid.
This objection, however, can be easily overcome by giving to it a certain
amount of elasticity. It does not appear that Pénaud gave much attention to
this feature, but stress is laid upon it in the article “Flight,” in the ninth
edition of the Encyclopædia Britannica, and I have introduced a simple
device for securing it.
The complete success of the device implies a strictly uniform velocity
and other conditions which cannot well he fulfilled in practice.
Page 97
Nevertheless, it is as efficient a contrivance for its object as has yet been
obtained.
More elaborate devices have been proposed, and a number of them,
depending for their efficiency upon the action of a variety of forces, have
been constructed by the writer, one of which will be described later. This
has the advantage that it tends to secure absolutely horizontal flight, but it is
much inferior in simplicity to the Pénaud tail.
Apart from considerations about the thrust, the CP is in practice always
almost directly over the CG, and this relationship is, according to what has
been suggested, obtained by moving the supporting surfaces relatively to
the CG, or vice versa, remembering, however, that, as these surfaces have
weight, any movement of them alters the CG of the whole, so that
successive readjustments may be needed. The adjustment is further
complicated by another important consideration, namely, that those parts
which change their weight during flight (like the water and the fuel) must
be kept very near the CG. As the water and fuel tanks are fixed, it appears,
then, that the center of gravity of the whole is practically fixed also, and this
consideration makes the adjustment a much more difficult problem than it
would be otherwise.25
obtained.
More elaborate devices have been proposed, and a number of them,
depending for their efficiency upon the action of a variety of forces, have
been constructed by the writer, one of which will be described later. This
has the advantage that it tends to secure absolutely horizontal flight, but it is
much inferior in simplicity to the Pénaud tail.
Apart from considerations about the thrust, the CP is in practice always
almost directly over the CG, and this relationship is, according to what has
been suggested, obtained by moving the supporting surfaces relatively to
the CG, or vice versa, remembering, however, that, as these surfaces have
weight, any movement of them alters the CG of the whole, so that
successive readjustments may be needed. The adjustment is further
complicated by another important consideration, namely, that those parts
which change their weight during flight (like the water and the fuel) must
be kept very near the CG. As the water and fuel tanks are fixed, it appears,
then, that the center of gravity of the whole is practically fixed also, and this
consideration makes the adjustment a much more difficult problem than it
would be otherwise.25
Page 98
PL. 11. STEEL FRAMES OF AERODROMES NOS. 4, 5, 6. 1893, 1895 AND 1896 ◊
Page 99
[p053] ◊
CHAPTER VII
HISTORY OF CONSTRUCTION OF FRAME AND ENGINES OF
AERODROMES
During the years 1892 and 1893, it will be recalled, four aerodromes,
known as Nos. 0, 1, 2, and 3, had been built, which were of two general
types of construction. First, that represented by No. 0, in which a radically
weak hull was made to support rods at the front and rear, to which the
wings and tail were attached. This aerodrome was abandoned on account of
the inability to provide it with sufficient power, as well as because of its
constructional weakness. Second, that type represented by Nos. 1, 2, and 3,
in which a midrod was carried through from front to rear, around which the
hull supporting the machinery was built. These models were much lighter
than No. 0, but were all abandoned because it was found impossible to
propel even the lightest of them. While all these machines were in the
strictest sense failures, inasmuch as none of them was ever equipped with
supporting surfaces, yet the experience gained in the construction of them
was of the very greatest value in determining the points at which strength
was needed, and in indicating the mode of construction by which strength
and rigidity could be obtained.26
189 3
Another aerodrome, known as No. 4 (shown in Plate 11), was designed in
the latter part of 1892, and by the end of March, 1893, its construction was
well under way. It was of the second type, in that the midrod was
continuous, but it differed from the preceding forms in having the
machinery (boilers, burners, and tanks) attached directly to the midrod, the
hull now taking the form of a mere protective sheathing. As in Nos. 2 and 3,
two engines were used, which were mounted on a cross-frame of light
tubing attached to the midrod at right angles. It had, as at first constructed,
no provision for the generation of steam, but only for carrying a reservoir of
carbonic acid to supply gas for the engines.
CHAPTER VII
HISTORY OF CONSTRUCTION OF FRAME AND ENGINES OF
AERODROMES
During the years 1892 and 1893, it will be recalled, four aerodromes,
known as Nos. 0, 1, 2, and 3, had been built, which were of two general
types of construction. First, that represented by No. 0, in which a radically
weak hull was made to support rods at the front and rear, to which the
wings and tail were attached. This aerodrome was abandoned on account of
the inability to provide it with sufficient power, as well as because of its
constructional weakness. Second, that type represented by Nos. 1, 2, and 3,
in which a midrod was carried through from front to rear, around which the
hull supporting the machinery was built. These models were much lighter
than No. 0, but were all abandoned because it was found impossible to
propel even the lightest of them. While all these machines were in the
strictest sense failures, inasmuch as none of them was ever equipped with
supporting surfaces, yet the experience gained in the construction of them
was of the very greatest value in determining the points at which strength
was needed, and in indicating the mode of construction by which strength
and rigidity could be obtained.26
189 3
Another aerodrome, known as No. 4 (shown in Plate 11), was designed in
the latter part of 1892, and by the end of March, 1893, its construction was
well under way. It was of the second type, in that the midrod was
continuous, but it differed from the preceding forms in having the
machinery (boilers, burners, and tanks) attached directly to the midrod, the
hull now taking the form of a mere protective sheathing. As in Nos. 2 and 3,
two engines were used, which were mounted on a cross-frame of light
tubing attached to the midrod at right angles. It had, as at first constructed,
no provision for the generation of steam, but only for carrying a reservoir of
carbonic acid to supply gas for the engines.
Page 100
The whole, including wings, tail, and engines, but without the carbonic
acid reservoir, weighed 1898 grammes (4.18 lbs.). A cylindrical reservoir,
weighing 521 grammes (1.14 lbs.) and capable of holding 1506 cu. cm. (92
cu. in.) was constructed for this purpose, and tested for 30 minutes with a
pressure of 100 [p054] atmospheres. If the weight of the cylinder, with its
contents and adjuncts, be taken as 800 grammes (1.76 lbs.), the total weight
of the aerodrome was 2698 grammes (5.95 lbs.). The wings were plane
surfaces of silk, stretched over a very light frame, with no intermediate ribs
to prevent the wing from being completely distorted by the upward pressure
of the air. Even if they had been sufficiently strong and stiff, the total
surface of both wings and tail was but 2601 sq. cm. (2.8 sq. ft.) or
approximately 0.5 sq. ft. of supporting surface to the pound, much less than
was found adequate, even under the most favorable circumstances. The
weight was much more than had been contemplated when the wings were
designed, yet, if all the other features of the aerodrome had been
satisfactory, and sufficient power had been secured, the work of providing
suitable supporting surfaces would have been attempted. But as it was
found that the engines when supplied with carbonic-acid gas were unable to
develop anything like the power necessary to propel the aerodrome, and
that the construction could be greatly improved in many other ways, this
aerodrome was entirely rebuilt. The work of the engines with carbonic acid
had been so completely unsatisfactory that the idea was entirely abandoned,
and no further attempts to develop an efficient motor other than steam were
made.
It now became realized more completely than ever before that the
primary requisite was to secure sufficient power, and that this could be
obtained only by the use of steam. This involved a number of problems, all
of which would have to be solved before any hope of a successful machine
could be entertained. In the first place, engines of sufficient power and
strength, but of the lightest possible construction, must be built. Second, a
boiler must be constructed of the least possible weight, which would
develop quickly and maintain steadily steam at a high enough pressure to
drive the engines. This demanded some form of heating apparatus, which
acid reservoir, weighed 1898 grammes (4.18 lbs.). A cylindrical reservoir,
weighing 521 grammes (1.14 lbs.) and capable of holding 1506 cu. cm. (92
cu. in.) was constructed for this purpose, and tested for 30 minutes with a
pressure of 100 [p054] atmospheres. If the weight of the cylinder, with its
contents and adjuncts, be taken as 800 grammes (1.76 lbs.), the total weight
of the aerodrome was 2698 grammes (5.95 lbs.). The wings were plane
surfaces of silk, stretched over a very light frame, with no intermediate ribs
to prevent the wing from being completely distorted by the upward pressure
of the air. Even if they had been sufficiently strong and stiff, the total
surface of both wings and tail was but 2601 sq. cm. (2.8 sq. ft.) or
approximately 0.5 sq. ft. of supporting surface to the pound, much less than
was found adequate, even under the most favorable circumstances. The
weight was much more than had been contemplated when the wings were
designed, yet, if all the other features of the aerodrome had been
satisfactory, and sufficient power had been secured, the work of providing
suitable supporting surfaces would have been attempted. But as it was
found that the engines when supplied with carbonic-acid gas were unable to
develop anything like the power necessary to propel the aerodrome, and
that the construction could be greatly improved in many other ways, this
aerodrome was entirely rebuilt. The work of the engines with carbonic acid
had been so completely unsatisfactory that the idea was entirely abandoned,
and no further attempts to develop an efficient motor other than steam were
made.
It now became realized more completely than ever before that the
primary requisite was to secure sufficient power, and that this could be
obtained only by the use of steam. This involved a number of problems, all
of which would have to be solved before any hope of a successful machine
could be entertained. In the first place, engines of sufficient power and
strength, but of the lightest possible construction, must be built. Second, a
boiler must be constructed of the least possible weight, which would
develop quickly and maintain steadily steam at a high enough pressure to
drive the engines. This demanded some form of heating apparatus, which
Page 101
could work under the adverse condition of enclosure in a narrow hull, and
steadily supply enough heat to develop the relatively large quantity of steam
required by the engines.
The first of these problems, that of procuring suitable engines, was at
least temporarily solved by the construction of two engines with brass
cylinders, which had a diameter of 2.4 cm. (0.95 in.), and a piston stroke of
5 cm. (1.97 in.). The valve was a simple slide-valve of the piston type,
arranged to cut off steam at one-half stroke. No packing was used for the
piston or the valve, which were turned to an accurate fit to the cylinder and
the steam-chest respectively. In the engines built up to this time, the parts
had frequently been soldered together, and a great deal of trouble and delay
had arisen from this cause. In these new engines, however, as strong and
careful a construction was made as was possible within the very narrow
limits of weight, with the result that the engines, though by no means as
efficient as those constructed later, were used in all the experiments of 1893
and also during the first part of 1894. [p055]
As soon as these engines were completed, in February, 1893, a test was
made of one of the cylinders, steam being supplied from the boiler of the
shop-engine. The experiments were made with the Prony brake, and showed
that at a speed of 1000 revolutions per minute, the power developed from a
single cylinder was 0.208 H. P., with a mean effective pressure in the
cylinder of only about 21 pounds per square inch of piston area, allowing a
loss of 25 per cent for the internal resistance of the engine. This pressure
was so much less than should have been obtained with the steam pressure
used, that it now seems evident that the steam passages and ports were too
small to admit and exhaust the steam with sufficient rapidity to do the work
with the same efficiency that is obtained in common practice. This,
however, was not immediately recognized. The piston speed at 1000 R. P.
M. was 328 feet per minute, at which speed the steam at a pressure of 80
pounds should have been able to follow up the piston and maintain almost,
if not quite, full boiler pressure to the point of cut-off, but it did not do so.
The problem of generating steam was much more difficult and required a
long and tedious series of experiments, which consumed the greater part of
steadily supply enough heat to develop the relatively large quantity of steam
required by the engines.
The first of these problems, that of procuring suitable engines, was at
least temporarily solved by the construction of two engines with brass
cylinders, which had a diameter of 2.4 cm. (0.95 in.), and a piston stroke of
5 cm. (1.97 in.). The valve was a simple slide-valve of the piston type,
arranged to cut off steam at one-half stroke. No packing was used for the
piston or the valve, which were turned to an accurate fit to the cylinder and
the steam-chest respectively. In the engines built up to this time, the parts
had frequently been soldered together, and a great deal of trouble and delay
had arisen from this cause. In these new engines, however, as strong and
careful a construction was made as was possible within the very narrow
limits of weight, with the result that the engines, though by no means as
efficient as those constructed later, were used in all the experiments of 1893
and also during the first part of 1894. [p055]
As soon as these engines were completed, in February, 1893, a test was
made of one of the cylinders, steam being supplied from the boiler of the
shop-engine. The experiments were made with the Prony brake, and showed
that at a speed of 1000 revolutions per minute, the power developed from a
single cylinder was 0.208 H. P., with a mean effective pressure in the
cylinder of only about 21 pounds per square inch of piston area, allowing a
loss of 25 per cent for the internal resistance of the engine. This pressure
was so much less than should have been obtained with the steam pressure
used, that it now seems evident that the steam passages and ports were too
small to admit and exhaust the steam with sufficient rapidity to do the work
with the same efficiency that is obtained in common practice. This,
however, was not immediately recognized. The piston speed at 1000 R. P.
M. was 328 feet per minute, at which speed the steam at a pressure of 80
pounds should have been able to follow up the piston and maintain almost,
if not quite, full boiler pressure to the point of cut-off, but it did not do so.
The problem of generating steam was much more difficult and required a
long and tedious series of experiments, which consumed the greater part of
Page 102
the year before any considerable degree of success had been attained. In the
course of these experiments many unexpected difficulties were
encountered, which necessitated the construction of special forms of
apparatus, which will be described at the proper point. Numerous features
of construction, which seemed to be of value when first conceived, but
which proved useless when rigorously tested, will be noted here, whenever
a knowledge of their valuelessness may seem to be of advantage to the
reader.
The boiler was necessarily developed simultaneously with the
development of the heating apparatus, and in the following pages, as far as
possible, they will be treated together; but often for the sake of clearness
and to avoid repetition, separate treatment will be necessary.
At the beginning of these experiments, there was much doubt as to
whether alcohol or gasoline would be found most suitable for the immediate
purpose. An alcohol burner had been used in connection with the earliest
aerodrome, No. 0, but from the results obtained with it at that time, there
seemed to be little reason to hope for success with it. It is to be premised
that the problem, which at first seemed insoluble, was no less than to
produce steam for something like 1 H. P. by a fire-grate, which should
occupy only a few cubic inches (about the size of a clenched hand) and
weigh but a few ounces. It had to be attacked, however, and as alcohol
offered the great advantage of high calorific properties with freedom from
all danger of explosion, it was at first used.
Early in 1893, it occurred to me to modify the burner so as to make it
essentially an aeolipile, and in April of that year the first experimental
aeolipile model shown at A (Plate 12) was made. It was very small and
intended for the [p056] demonstration of a principle rather than for actual
service, but the construction of this small aeolipile was an epoch in the
history of the aerodrome. It furnished immensely more heat than anything
that had preceded it, and weighed so little and worked so well that in May
the aeolipile marked B was made. In this design two pipes were led from
the upper portion of the cylinder, one to a large Bunsen burner which heated
the boiler, the other to a small burner placed under the tank to vaporize the
course of these experiments many unexpected difficulties were
encountered, which necessitated the construction of special forms of
apparatus, which will be described at the proper point. Numerous features
of construction, which seemed to be of value when first conceived, but
which proved useless when rigorously tested, will be noted here, whenever
a knowledge of their valuelessness may seem to be of advantage to the
reader.
The boiler was necessarily developed simultaneously with the
development of the heating apparatus, and in the following pages, as far as
possible, they will be treated together; but often for the sake of clearness
and to avoid repetition, separate treatment will be necessary.
At the beginning of these experiments, there was much doubt as to
whether alcohol or gasoline would be found most suitable for the immediate
purpose. An alcohol burner had been used in connection with the earliest
aerodrome, No. 0, but from the results obtained with it at that time, there
seemed to be little reason to hope for success with it. It is to be premised
that the problem, which at first seemed insoluble, was no less than to
produce steam for something like 1 H. P. by a fire-grate, which should
occupy only a few cubic inches (about the size of a clenched hand) and
weigh but a few ounces. It had to be attacked, however, and as alcohol
offered the great advantage of high calorific properties with freedom from
all danger of explosion, it was at first used.
Early in 1893, it occurred to me to modify the burner so as to make it
essentially an aeolipile, and in April of that year the first experimental
aeolipile model shown at A (Plate 12) was made. It was very small and
intended for the [p056] demonstration of a principle rather than for actual
service, but the construction of this small aeolipile was an epoch in the
history of the aerodrome. It furnished immensely more heat than anything
that had preceded it, and weighed so little and worked so well that in May
the aeolipile marked B was made. In this design two pipes were led from
the upper portion of the cylinder, one to a large Bunsen burner which heated
the boiler, the other to a small burner placed under the tank to vaporize the
Page 103
alcohol. This was followed by the one shown at C, wherein the heating
burner was smaller and the gas pipe, leading to the main burner, larger.
Figures D, E, F, and G (Plate 12) were really continuations and
improvements of the same idea. In C there was simply a tube or flue
through the tank; in F, however, this tube discharged into a smoke-stack
fastened to the end of the cylinder, while in G the flue turned upward within
the tank itself and discharged into the short stack on top. The object of these
changes was to increase the draft and heating power of the small flame, so
that the gas would be more rapidly generated and a greater quantity be thus
made available for use under the boiler in a unit of time. They were,
however, though improvements in a construction which was itself a great
advance, still inadequate to give out a sufficient amount of heat to meet the
excessive demands of the required quantity of steam. The boilers in
connection with which these aeolipiles were used must now be considered.
The first boiler E (Plate 13) made during this year was a double-coil
boiler of the Serpollet type, formed of 19 feet of copper tubing having an
internal diameter of about 18 inch. Attached to the boiler was a small vertical
drum, from the top of which steam was led to the engine, a pipe from the
bottom leading to the pump. This boiler was tested in April with an alcohol
heater, the pump in this trial being worked by hand. This apparatus
developed a steam pressure varying from 25 to 75 pounds, which caused the
engines to drive a 60 cm. propeller of 1.25 pitch-ratio 565 revolutions per
minute. The greatest difficulty was experienced in securing a sufficient and
uniform circulation in the boiler coils. The action in the present case was
extremely irregular, as the pressure sometimes rose to 150 pounds, driving
the engines at a dangerous speed and bending the eccentric rod, while at
other times it would fall so low that the engines stopped completely.
As the pump used in this trial had proved so unsatisfactory and
unreliable, it was replaced by a reservoir of water having an air-chamber
charged to 10 atmospheres, the flow from which could apparently be
regulated with the greatest nicety by a needle valve at the point of egress;
burner was smaller and the gas pipe, leading to the main burner, larger.
Figures D, E, F, and G (Plate 12) were really continuations and
improvements of the same idea. In C there was simply a tube or flue
through the tank; in F, however, this tube discharged into a smoke-stack
fastened to the end of the cylinder, while in G the flue turned upward within
the tank itself and discharged into the short stack on top. The object of these
changes was to increase the draft and heating power of the small flame, so
that the gas would be more rapidly generated and a greater quantity be thus
made available for use under the boiler in a unit of time. They were,
however, though improvements in a construction which was itself a great
advance, still inadequate to give out a sufficient amount of heat to meet the
excessive demands of the required quantity of steam. The boilers in
connection with which these aeolipiles were used must now be considered.
The first boiler E (Plate 13) made during this year was a double-coil
boiler of the Serpollet type, formed of 19 feet of copper tubing having an
internal diameter of about 18 inch. Attached to the boiler was a small vertical
drum, from the top of which steam was led to the engine, a pipe from the
bottom leading to the pump. This boiler was tested in April with an alcohol
heater, the pump in this trial being worked by hand. This apparatus
developed a steam pressure varying from 25 to 75 pounds, which caused the
engines to drive a 60 cm. propeller of 1.25 pitch-ratio 565 revolutions per
minute. The greatest difficulty was experienced in securing a sufficient and
uniform circulation in the boiler coils. The action in the present case was
extremely irregular, as the pressure sometimes rose to 150 pounds, driving
the engines at a dangerous speed and bending the eccentric rod, while at
other times it would fall so low that the engines stopped completely.
As the pump used in this trial had proved so unsatisfactory and
unreliable, it was replaced by a reservoir of water having an air-chamber
charged to 10 atmospheres, the flow from which could apparently be
regulated with the greatest nicety by a needle valve at the point of egress;
Page 104
but for some reason its performance was unsatisfactory and remained so
after weeks of experiment.
after weeks of experiment.
Page 105
PL. 12. BURNERS, AEOLIPILES, AND SEPARATORS ◊
Page 106
PL. 13. BOILERS OF AERODROMES ◊
There was used in connection with this device the double-coil boiler
shown at F (Plate 13) which was made of tubes flattened so as to be nearly
capillary. The idea of this was to obtain a larger heating surface and a
smaller volume of [p057] water, so that by proper regulation at the needle
valve, just that quantity would be delivered which could be converted into
steam in its passage through the coils, and be ready for use in the engines as
it left the boiler at the farther extremity. The results obtained from this were
an improvement over those from the original coil, and a third set of coils
(G, in Plate 13) was made. This boiler consisted of three flattened tubes
superposed one over another.
There was used in connection with this device the double-coil boiler
shown at F (Plate 13) which was made of tubes flattened so as to be nearly
capillary. The idea of this was to obtain a larger heating surface and a
smaller volume of [p057] water, so that by proper regulation at the needle
valve, just that quantity would be delivered which could be converted into
steam in its passage through the coils, and be ready for use in the engines as
it left the boiler at the farther extremity. The results obtained from this were
an improvement over those from the original coil, and a third set of coils
(G, in Plate 13) was made. This boiler consisted of three flattened tubes
superposed one over another.
Page 107
These two boilers were tried by placing them in a charcoal fire and
turning on an alcohol blast, while water from a reservoir under constant air
pressure was forced through them past a pin valve. The result was that the
two-stranded coil supplied steam at from 10 to 40 pounds pressure to run
the engines at about 400 revolutions per minute. The pressure rose steadily
for about 40 seconds and then suddenly fell away, though the coils were
red-hot, and neither the water nor the alcohol was exhausted—apparently
because of the irregularity of the supply of water, due to the time taken by it
after passing the valve to fill the considerable space intervening between
that point and the boiler.
An attempt was made to overcome this difficulty by putting a stop-cock
directly in front of the boiler so that the water, while still under the control
of the needle valve, could be turned in at once; the alcohol blast was also
arranged to be turned on or off at pleasure, and provision was made, by
taking out the end of the flue inclosing the boiler, to provide for an
increased air supply. With this arrangement a flame eight or nine inches
long was obtained, but a test showed that not more than 25 grammes of
water per minute passed through the tubes, which was not enough.
Further tests with these boilers were so far satisfactory as to show that
with the flattened-tube Serpollet boiler, comprising from 60 to 80 feet of
tubing, from 80 to 100 pounds pressure of steam could be maintained, but
not steadily. As there were difficulties in flattening the tubes to make a
boiler of this sort, a compromise was effected in the construction of the one
shown at H (Plate 13), which was made of light copper tubes 5 mm. in
diameter, laid up in three lengths of 6 metres each. The ends of these coils
were so attached to each other that the water entering at one end of the
smallest coil would pass through it and then enter the middle coil, whence it
passed through the third or outer coil. Two sets of these coils were made
and placed in the thin sheathings shown in the photograph. Repeated
experiments with these boilers demonstrated that the pressure did not rise
high enough in proportion to the heat applied, and that even the pressures
obtained were irregular and untrustworthy. The principal difficulty still lay
in maintaining an active and uniform circulation through the coils, and for
turning on an alcohol blast, while water from a reservoir under constant air
pressure was forced through them past a pin valve. The result was that the
two-stranded coil supplied steam at from 10 to 40 pounds pressure to run
the engines at about 400 revolutions per minute. The pressure rose steadily
for about 40 seconds and then suddenly fell away, though the coils were
red-hot, and neither the water nor the alcohol was exhausted—apparently
because of the irregularity of the supply of water, due to the time taken by it
after passing the valve to fill the considerable space intervening between
that point and the boiler.
An attempt was made to overcome this difficulty by putting a stop-cock
directly in front of the boiler so that the water, while still under the control
of the needle valve, could be turned in at once; the alcohol blast was also
arranged to be turned on or off at pleasure, and provision was made, by
taking out the end of the flue inclosing the boiler, to provide for an
increased air supply. With this arrangement a flame eight or nine inches
long was obtained, but a test showed that not more than 25 grammes of
water per minute passed through the tubes, which was not enough.
Further tests with these boilers were so far satisfactory as to show that
with the flattened-tube Serpollet boiler, comprising from 60 to 80 feet of
tubing, from 80 to 100 pounds pressure of steam could be maintained, but
not steadily. As there were difficulties in flattening the tubes to make a
boiler of this sort, a compromise was effected in the construction of the one
shown at H (Plate 13), which was made of light copper tubes 5 mm. in
diameter, laid up in three lengths of 6 metres each. The ends of these coils
were so attached to each other that the water entering at one end of the
smallest coil would pass through it and then enter the middle coil, whence it
passed through the third or outer coil. Two sets of these coils were made
and placed in the thin sheathings shown in the photograph. Repeated
experiments with these boilers demonstrated that the pressure did not rise
high enough in proportion to the heat applied, and that even the pressures
obtained were irregular and untrustworthy. The principal difficulty still lay
in maintaining an active and uniform circulation through the coils, and for
Page 108
this purpose the water reservoir under constant air pressure had proved
itself inadequate. This pointed to a return to the use of the force pump, the
construction of which had hitherto presented so many special difficulties
that it had been temporarily abandoned. [p058]
A further difficulty experienced in the use of these boilers had been that
of obtaining dry steam for the engines, as during the early experiments the
steam had been delivered directly into the engines from the boiler coils. But
in August the writer devised a chamber, known as the “separator,” where it
had an opportunity to separate from the water and issue as dry steam, or at
least approximately dry steam. This was an arrangement familiar in
principle to steam engineers under another form, but it was one of the many
things which, in the ignorance of steam engineering the writer has already
freely admitted, he had to reinvent for himself.
At about the same time, a new pump was designed to drive the water
from the bottom of the separator, which served the double purpose of steam
drum and reservoir, into the coils. This pump had a diameter of 4.8 cm., and
was run at 180 strokes per minute.
The result of the first experiments with these improvements demonstrated
that, within certain limits, the amount of water evaporated is proportional to
the circulation, and in this boiler the circulation was still the thing that was
at fault. Finally, the results of the experiments with the two-stranded, triple-
coil boiler may be summed up in the statement that it was possible to
maintain a pressure of 80 pounds, and that with it the engines could be
made to develop from 0.3 to 0.4 H. P. at best. It weighed 650 grammes
(1.43 pounds) without the asbestos jacket.
About this time the writer had the good fortune to secure the temporary
services of Dr. Carl Barus, an accomplished physicist, with whose aid a
great variety of boilers were experimented on.
The next form of boiler tested was that shown at N (Plate 13), made on a
system of coils in parallel, of which there were twenty complete turns. In
the first test it generated but 20 pounds of steam, because the flame refused
to work in the colder coils. The work of this boiler was very unsatisfactory,
and it was only with the greatest difficulty that more than ten pounds
itself inadequate. This pointed to a return to the use of the force pump, the
construction of which had hitherto presented so many special difficulties
that it had been temporarily abandoned. [p058]
A further difficulty experienced in the use of these boilers had been that
of obtaining dry steam for the engines, as during the early experiments the
steam had been delivered directly into the engines from the boiler coils. But
in August the writer devised a chamber, known as the “separator,” where it
had an opportunity to separate from the water and issue as dry steam, or at
least approximately dry steam. This was an arrangement familiar in
principle to steam engineers under another form, but it was one of the many
things which, in the ignorance of steam engineering the writer has already
freely admitted, he had to reinvent for himself.
At about the same time, a new pump was designed to drive the water
from the bottom of the separator, which served the double purpose of steam
drum and reservoir, into the coils. This pump had a diameter of 4.8 cm., and
was run at 180 strokes per minute.
The result of the first experiments with these improvements demonstrated
that, within certain limits, the amount of water evaporated is proportional to
the circulation, and in this boiler the circulation was still the thing that was
at fault. Finally, the results of the experiments with the two-stranded, triple-
coil boiler may be summed up in the statement that it was possible to
maintain a pressure of 80 pounds, and that with it the engines could be
made to develop from 0.3 to 0.4 H. P. at best. It weighed 650 grammes
(1.43 pounds) without the asbestos jacket.
About this time the writer had the good fortune to secure the temporary
services of Dr. Carl Barus, an accomplished physicist, with whose aid a
great variety of boilers were experimented on.
The next form of boiler tested was that shown at N (Plate 13), made on a
system of coils in parallel, of which there were twenty complete turns. In
the first test it generated but 20 pounds of steam, because the flame refused
to work in the colder coils. The work of this boiler was very unsatisfactory,
and it was only with the greatest difficulty that more than ten pounds
Page 109
pressure could be maintained. There was trouble, too, with the circulation,
in that when the flame was in full play the pump seemed to meet an almost
solid resistance, so that it could not be made to do its work.
A new boiler was accordingly made, consisting of three coils of four
strands each. With this the pump worked easily, but whereas it was expected
to get 120 pounds pressure, the best that could be obtained was 70 pounds.
The outer coil was then stripped off, and a trial made in which everything
ran smoothly and the pressure mounted momentarily to 90 pounds. After
some adjustment, a mean pressure of 80 pounds was obtained, giving 730
revolutions of the engine per minute, with an indicated horse-power of 0.32.
It was shown in this work that, within certain limits, steam is generated
most rapidly when it is used most rapidly, so that two engines could be used
[p059] almost as well as one, the reason apparently being that the rapid
circulation increased the steam generating power of the boiler, and that the
engines worked best at about 80 pounds. It was also found that a larger
tubing was better than the small, weight for weight, this fact being due to
the greater ease with which circulation could be maintained, since fewer
coils were necessary in order to obtain the same external heating surface.
The pressure in the coils and the separator was also much more nearly
equalized. The result was that the boiler temporarily approved was one
made of tubing 6.35 mm. (0.25 inch) in diameter, bent into a two-coil, two-
stranded boiler, having sixteen complete turns for each strand in each coil.
The total weight was 560 grammes (1.23 pounds) with a total heating
surface of 1300 sq. cm. (1.4 sq. ft.).
The separator used in the experiments made during August and
September was of a form in which the water was forced below a series of
partitions that prevented it from following the steam over into the cylinders
of the engines. It weighed 410 grammes (0.9 pound) and was most
conveniently worked with 700 grammes (1.54 pounds) of water. The boiler
and separator together weighed 970 grammes (2.1 pounds).
A new separator was, however, designed, which was horizontal instead of
vertical, as it was intended that it should be placed just below the midrod.
Another form, devised for constructional reasons, consisted of a cylinder in
in that when the flame was in full play the pump seemed to meet an almost
solid resistance, so that it could not be made to do its work.
A new boiler was accordingly made, consisting of three coils of four
strands each. With this the pump worked easily, but whereas it was expected
to get 120 pounds pressure, the best that could be obtained was 70 pounds.
The outer coil was then stripped off, and a trial made in which everything
ran smoothly and the pressure mounted momentarily to 90 pounds. After
some adjustment, a mean pressure of 80 pounds was obtained, giving 730
revolutions of the engine per minute, with an indicated horse-power of 0.32.
It was shown in this work that, within certain limits, steam is generated
most rapidly when it is used most rapidly, so that two engines could be used
[p059] almost as well as one, the reason apparently being that the rapid
circulation increased the steam generating power of the boiler, and that the
engines worked best at about 80 pounds. It was also found that a larger
tubing was better than the small, weight for weight, this fact being due to
the greater ease with which circulation could be maintained, since fewer
coils were necessary in order to obtain the same external heating surface.
The pressure in the coils and the separator was also much more nearly
equalized. The result was that the boiler temporarily approved was one
made of tubing 6.35 mm. (0.25 inch) in diameter, bent into a two-coil, two-
stranded boiler, having sixteen complete turns for each strand in each coil.
The total weight was 560 grammes (1.23 pounds) with a total heating
surface of 1300 sq. cm. (1.4 sq. ft.).
The separator used in the experiments made during August and
September was of a form in which the water was forced below a series of
partitions that prevented it from following the steam over into the cylinders
of the engines. It weighed 410 grammes (0.9 pound) and was most
conveniently worked with 700 grammes (1.54 pounds) of water. The boiler
and separator together weighed 970 grammes (2.1 pounds).
A new separator was, however, designed, which was horizontal instead of
vertical, as it was intended that it should be placed just below the midrod.
Another form, devised for constructional reasons, consisted of a cylinder in
Page 110
which a pump was imbedded. Heretofore the pump used had been single-
acting, but it was now proposed to make a double-acting pump. Upon
testing this apparatus, it was found that when using an aeolipile, it took 150
grammes of alcohol to evaporate 600 grammes of water. It was evident that
the latter was used very wastefully, so that the thermal efficiency of the
engine was not over one per cent; but it was also evident that, under the
necessity of sacrificing everything to lightness, this waste was largely
inevitable.
About the middle of October, another boiler (O, Plate 13) was made,
which consisted of two coils wound in right and left hand screw-threads,
one fitting loosely over the other, so as to make a cylindrical lattice-work 32
cm. (12.6 in.) long. Each coil contained two strands of copper tube 0.3 mm.
thick, and weighing 54 grammes to the metre (0.036 pound to the foot). The
inner coil had a diameter of 5.63 cm. (2.22 in.), with nine turns of tube to
the strand, the two strands making a length of 319 cm. (10.5 feet) for the
coil. The outer coil had a mean diameter of 6.88 cm. (2.71 in.) and a length
of 388 cm. (12.7 feet) for the two strands. The total length of the two coils
was, therefore, 707 cm. (23.2 feet), with a heating surface of about 1415 sq.
cm. (1.52 sq. ft.) and a total weight of 382 grammes (0.84 pound).
The results obtained with this boiler were so far satisfactory as to show
that, under the most favorable conditions, when air was supplied in
unlimited quantities and there were no disturbing currents to put out or
interfere with the work [p060] of the burners, steam could be supplied at a
sufficient pressure to run the engines. It was realized, however, that the
conditions in flight would be very different, and that in order to protect the
apparatus from the wind, some sort of protecting covering would have to be
devised, which would of itself introduce new difficulties in providing the
burners with a proper and uniform draft.
acting, but it was now proposed to make a double-acting pump. Upon
testing this apparatus, it was found that when using an aeolipile, it took 150
grammes of alcohol to evaporate 600 grammes of water. It was evident that
the latter was used very wastefully, so that the thermal efficiency of the
engine was not over one per cent; but it was also evident that, under the
necessity of sacrificing everything to lightness, this waste was largely
inevitable.
About the middle of October, another boiler (O, Plate 13) was made,
which consisted of two coils wound in right and left hand screw-threads,
one fitting loosely over the other, so as to make a cylindrical lattice-work 32
cm. (12.6 in.) long. Each coil contained two strands of copper tube 0.3 mm.
thick, and weighing 54 grammes to the metre (0.036 pound to the foot). The
inner coil had a diameter of 5.63 cm. (2.22 in.), with nine turns of tube to
the strand, the two strands making a length of 319 cm. (10.5 feet) for the
coil. The outer coil had a mean diameter of 6.88 cm. (2.71 in.) and a length
of 388 cm. (12.7 feet) for the two strands. The total length of the two coils
was, therefore, 707 cm. (23.2 feet), with a heating surface of about 1415 sq.
cm. (1.52 sq. ft.) and a total weight of 382 grammes (0.84 pound).
The results obtained with this boiler were so far satisfactory as to show
that, under the most favorable conditions, when air was supplied in
unlimited quantities and there were no disturbing currents to put out or
interfere with the work [p060] of the burners, steam could be supplied at a
sufficient pressure to run the engines. It was realized, however, that the
conditions in flight would be very different, and that in order to protect the
apparatus from the wind, some sort of protecting covering would have to be
devised, which would of itself introduce new difficulties in providing the
burners with a proper and uniform draft.
Page 111
FIG. 10. Diagram of pendulum.
The hull, as at first constructed, consisted of a cylindrical sheathing open
in front, through the rear end of which the boiler and aeolipile projected
inward, so that the air taken in at the front would be drawn through the
boiler and hearth to the exclusion of lateral currents. In the first tests,
however, after the hull had been applied, it was impossible to secure a
proper rate of combustion, nearly the whole hull being filled with a bluish
flame, while only a very small portion of the gases of combustion passed
into the coils of the boiler. The remedy for this lay in obtaining an increased
draft, and a small stack was, therefore, arranged to carry off the products of
combustion. This proved inadequate, and it was only after several weeks of
experiment with various types of smoke-stack, and constant alteration of the
aeolipile, that it was possible to make the apparatus work [p061] efficiently
when it was inside the hull. Finally such a degree of success was attained
The hull, as at first constructed, consisted of a cylindrical sheathing open
in front, through the rear end of which the boiler and aeolipile projected
inward, so that the air taken in at the front would be drawn through the
boiler and hearth to the exclusion of lateral currents. In the first tests,
however, after the hull had been applied, it was impossible to secure a
proper rate of combustion, nearly the whole hull being filled with a bluish
flame, while only a very small portion of the gases of combustion passed
into the coils of the boiler. The remedy for this lay in obtaining an increased
draft, and a small stack was, therefore, arranged to carry off the products of
combustion. This proved inadequate, and it was only after several weeks of
experiment with various types of smoke-stack, and constant alteration of the
aeolipile, that it was possible to make the apparatus work [p061] efficiently
when it was inside the hull. Finally such a degree of success was attained
Page 112
that the burners could be kept lighted even when the aerodrome was placed
in a considerable artificial breeze, created by a blower in the shop.
In connection with these tests of the engines and boilers, some method
was desired, in addition to the Prony brake tests, by which the thrust of the
propellers when driven by the engines at various speeds could be measured
accurately and in terms which would be readily available in judging
whether the aerodromes were ready to be given an actual trial in free flight.
Such a method was found in the use of an apparatus known as the
“pendulum,” which was introduced near the end of 1892, but was not
generally used until the end of 1893. After this time, however, this test was
made a condition prerequisite to taking any of the aerodromes into the field,
and proved of the greatest assistance in estimating the probable outcome of
the trials.
The apparatus used, which is diagrammatically shown in Fig. 10, was
extremely simple both in theory and operation. It consisted primarily of a
horizontal arm AC carrying the knife-edge B by which it is pivoted on each
side on supporting beams not shown. Depending from AC is the light
vertical arm DE, rigidly joined to it and carrying the lower horizontal arm
FG, all of which are braced together so as to maintain the arm DE
constantly perpendicular to AC. To this arm FG the model was rigidly
attached with its center of gravity in line with the vertical arm DE and its
weight increased by the addition of properly disposed flat weights, in order
to make the angle of lift for a given thrust of the propellers smaller and less
likely to interfere with the working of the boiler and separator.
Before the actual test of the “lift” could be made, it was necessary to
know the exact distance of the vertical center of gravity of the model and
the extra weights from the knife-edge B. This was determined by the
following method: A known weight was suspended from the arm AB at
some arbitrarily selected distance from the point B. This weight caused the
perpendicular arms AB and DE to rotate through an angle, θ, which was
measured on the scale KL. Knowing, then, the weight on the arm AB, its
point of application, the weight of the aerodrome suspended on the arm DE,
and the angle of rotation, it is easy, by a simple application of trigonometric
in a considerable artificial breeze, created by a blower in the shop.
In connection with these tests of the engines and boilers, some method
was desired, in addition to the Prony brake tests, by which the thrust of the
propellers when driven by the engines at various speeds could be measured
accurately and in terms which would be readily available in judging
whether the aerodromes were ready to be given an actual trial in free flight.
Such a method was found in the use of an apparatus known as the
“pendulum,” which was introduced near the end of 1892, but was not
generally used until the end of 1893. After this time, however, this test was
made a condition prerequisite to taking any of the aerodromes into the field,
and proved of the greatest assistance in estimating the probable outcome of
the trials.
The apparatus used, which is diagrammatically shown in Fig. 10, was
extremely simple both in theory and operation. It consisted primarily of a
horizontal arm AC carrying the knife-edge B by which it is pivoted on each
side on supporting beams not shown. Depending from AC is the light
vertical arm DE, rigidly joined to it and carrying the lower horizontal arm
FG, all of which are braced together so as to maintain the arm DE
constantly perpendicular to AC. To this arm FG the model was rigidly
attached with its center of gravity in line with the vertical arm DE and its
weight increased by the addition of properly disposed flat weights, in order
to make the angle of lift for a given thrust of the propellers smaller and less
likely to interfere with the working of the boiler and separator.
Before the actual test of the “lift” could be made, it was necessary to
know the exact distance of the vertical center of gravity of the model and
the extra weights from the knife-edge B. This was determined by the
following method: A known weight was suspended from the arm AB at
some arbitrarily selected distance from the point B. This weight caused the
perpendicular arms AB and DE to rotate through an angle, θ, which was
measured on the scale KL. Knowing, then, the weight on the arm AB, its
point of application, the weight of the aerodrome suspended on the arm DE,
and the angle of rotation, it is easy, by a simple application of trigonometric
Page 113
functions, to determine the distance of the center of gravity of the model
from the point B.
In a test of Aerodrome No. 6 made on September 23, 1898, the weight
suspended from AB was 10,000 grammes, its point of application 50 cm.,
the model was weighted to 20,450 grammes, and the angle of rotation, θ,
was 7° 2′. Letting y equal the distance of the CG from B, we may equate the
balanced forces thus:
10,000×50 cos 7° 2′ = 20,450×y sin 7° 2′
10,000×50 cot 7° 2′ = 20,450y
y = 198.2 cm.
[p062]
Having determined this distance, the weight on AB was removed and the
aerodrome was allowed to regain its former position. The distance of the
center of thrust from B was then measured. The engine was next started and
the number of revolutions of the propellers counted by a tachometer. The
thrust of the propellers, acting perpendicularly to the arm BD, produced
rotation around the point B, the angle of which was measured as above.
In the power test of No. 6, the following data were obtained:
W = weight of aerodrome = 20,450 grammes.
θ = angle of lift = 19° 30′.
Distance of CG from center of rotation = 198.2 cm.
Distance of center of thrust from center of rotation = 186.3 cm.
As the propeller thrust and the weight of the model are forces acting in
opposite directions at known distances from a center of rotation, letting L
equal the “dead lift,” we may express the equation thus:
W sin θ × 198.2 = L × 186.3,
L = 198.2
186.3
× sin 19° 30′ × 20,450,
L = 7,263 grammes “dead lift.”
The flying weight of Aerodrome No. 6 was 12,064 grammes, and the per
cent of this weight lifted was, therefore,
from the point B.
In a test of Aerodrome No. 6 made on September 23, 1898, the weight
suspended from AB was 10,000 grammes, its point of application 50 cm.,
the model was weighted to 20,450 grammes, and the angle of rotation, θ,
was 7° 2′. Letting y equal the distance of the CG from B, we may equate the
balanced forces thus:
10,000×50 cos 7° 2′ = 20,450×y sin 7° 2′
10,000×50 cot 7° 2′ = 20,450y
y = 198.2 cm.
[p062]
Having determined this distance, the weight on AB was removed and the
aerodrome was allowed to regain its former position. The distance of the
center of thrust from B was then measured. The engine was next started and
the number of revolutions of the propellers counted by a tachometer. The
thrust of the propellers, acting perpendicularly to the arm BD, produced
rotation around the point B, the angle of which was measured as above.
In the power test of No. 6, the following data were obtained:
W = weight of aerodrome = 20,450 grammes.
θ = angle of lift = 19° 30′.
Distance of CG from center of rotation = 198.2 cm.
Distance of center of thrust from center of rotation = 186.3 cm.
As the propeller thrust and the weight of the model are forces acting in
opposite directions at known distances from a center of rotation, letting L
equal the “dead lift,” we may express the equation thus:
W sin θ × 198.2 = L × 186.3,
L = 198.2
186.3
× sin 19° 30′ × 20,450,
L = 7,263 grammes “dead lift.”
The flying weight of Aerodrome No. 6 was 12,064 grammes, and the per
cent of this weight lifted was, therefore,
Page 114
7,263
12,064
= 60.3.
This was much more than was necessary for flight, but in order to insure
successful flights and avoid delay, the rule was made in 1895 that no
aerodrome was to be launched until it had previously demonstrated its
ability to generate enough power to maintain for at least two minutes a lift
of 50 per cent of the total flying weight. At the same time other important
data were obtained, such as the steam-pressure, the time required to raise
sufficient steam, the total time of the run, and the general working of the
boilers and engines.
As will easily be seen, these tests afforded a most satisfactory basis of
judging what the aerodromes might be expected to do in actual flight if the
balancing were correct.
At this time, October, 1893, the aerodrome (Old No. 4) was practically
complete, and the most anxious thought was given to lightening it in every
way consistent with the ever-present demand for more power, which
necessitated an increase in the weight of both burners and boilers to supply
the requisite steam.
On November 14, when the aerodrome was prepared to be shipped to
Quantico for trial, its condition was about as follows. The steam-generating
apparatus—the parts of which were of substantially the forms last
described, although some slight improvements had been introduced—had
been developed to [p063] such a point that a pressure of from 70 to 80
pounds of steam could be maintained for 70 seconds, when it was tested in
the shop. What it would do under the unfavorable conditions imposed by
flight was to be learned only by trial.
At this pressure, the engines, the efficiency of which had been increased
by an improvement in packing, would develop approximately 0.4 indicated
H. P., while at 105 pounds pressure they at times developed as much as 0.8
H. P. When the aerodrome was tested on the pendulum, these engines, when
making less than 700 revolutions per minute, lifted over 40 per cent of the
total flying weight.
12,064
= 60.3.
This was much more than was necessary for flight, but in order to insure
successful flights and avoid delay, the rule was made in 1895 that no
aerodrome was to be launched until it had previously demonstrated its
ability to generate enough power to maintain for at least two minutes a lift
of 50 per cent of the total flying weight. At the same time other important
data were obtained, such as the steam-pressure, the time required to raise
sufficient steam, the total time of the run, and the general working of the
boilers and engines.
As will easily be seen, these tests afforded a most satisfactory basis of
judging what the aerodromes might be expected to do in actual flight if the
balancing were correct.
At this time, October, 1893, the aerodrome (Old No. 4) was practically
complete, and the most anxious thought was given to lightening it in every
way consistent with the ever-present demand for more power, which
necessitated an increase in the weight of both burners and boilers to supply
the requisite steam.
On November 14, when the aerodrome was prepared to be shipped to
Quantico for trial, its condition was about as follows. The steam-generating
apparatus—the parts of which were of substantially the forms last
described, although some slight improvements had been introduced—had
been developed to [p063] such a point that a pressure of from 70 to 80
pounds of steam could be maintained for 70 seconds, when it was tested in
the shop. What it would do under the unfavorable conditions imposed by
flight was to be learned only by trial.
At this pressure, the engines, the efficiency of which had been increased
by an improvement in packing, would develop approximately 0.4 indicated
H. P., while at 105 pounds pressure they at times developed as much as 0.8
H. P. When the aerodrome was tested on the pendulum, these engines, when
making less than 700 revolutions per minute, lifted over 40 per cent of the
total flying weight.
Page 115
The propellers used at this time were accurate helices, having a diameter
of 60 cm., a width of blade of approximately 36 degrees, and a pitch-ratio
of 1.25. They were formed of wood, and were bushed with brass where they
were attached to the shafts.
of 60 cm., a width of blade of approximately 36 degrees, and a pitch-ratio
of 1.25. They were formed of wood, and were bushed with brass where they
were attached to the shafts.
Page 116
AERODROME OLD NO. 4
AS PREPARED FOR FLIGHT BEFORE BEING SHIPPED FOR TRIAL ON NOVEMBER
14, 1893
Part. Copper. Steel. Brass. Iron.
gms. gms. gms. gms.
Aeolipile 200 .. 92 ..
Boiler 350 .. 37 ..
Separator and pumps 300 30 100 20
Engine and frame .. 350 570 ..
Midrod (200 cm. long) .. 220 .. ..
Two smoke-stacks 70 .. .. ..
Asbestos jacketing .. .. .. ..
Air chamber .. .. .. 82
Spider between boiler and burner 32 .. .. ..
Intake valve .. .. 15 ..
Total 952 600 814 102
Hull 50 .. 50 ..
Pins for starter .. 15 .. ..
Two large wings and tail .. .. .. ..
Buffer and steerer .. .. .. ..
Propellers .. .. .. ..
Total 50 15 50 ..
Grand total 1002 615 864 102
Density 8.9 7.8 8.5 7.5
Volume (cu. cms.) 113 79 102 136
Alcohol .. .. .. ..
Water .. .. .. ..
Total .. .. .. ..
Density .. .. .. ..
Volume (cu. cm.) .. .. .. ..
AS PREPARED FOR FLIGHT BEFORE BEING SHIPPED FOR TRIAL ON NOVEMBER
14, 1893
Part. Copper. Steel. Brass. Iron.
gms. gms. gms. gms.
Aeolipile 200 .. 92 ..
Boiler 350 .. 37 ..
Separator and pumps 300 30 100 20
Engine and frame .. 350 570 ..
Midrod (200 cm. long) .. 220 .. ..
Two smoke-stacks 70 .. .. ..
Asbestos jacketing .. .. .. ..
Air chamber .. .. .. 82
Spider between boiler and burner 32 .. .. ..
Intake valve .. .. 15 ..
Total 952 600 814 102
Hull 50 .. 50 ..
Pins for starter .. 15 .. ..
Two large wings and tail .. .. .. ..
Buffer and steerer .. .. .. ..
Propellers .. .. .. ..
Total 50 15 50 ..
Grand total 1002 615 864 102
Density 8.9 7.8 8.5 7.5
Volume (cu. cms.) 113 79 102 136
Alcohol .. .. .. ..
Water .. .. .. ..
Total .. .. .. ..
Density .. .. .. ..
Volume (cu. cm.) .. .. .. ..
Page 117
AERODROME OLD NO. 4 DATA, CONTINUED
Wood and Mica and Total and mean
Part. Fluid.
silk. asbestos. weights.
gms. gms. gms. gms.
Aeolipile .. .. .. 292
Boiler .. .. .. 387
Separator and pumps .. .. .. 450
Engine and frame .. .. .. 920
Midrod (200 cm. long) .. .. .. 220
Two smoke-stacks .. .. .. 70
Asbestos jacketing .. 50 .. 50
Air chamber .. .. .. 82
Spider between boiler and
.. .. .. 32
burner
Intake valve .. .. .. 15
Total .. 50 .. 2518 =5.54lbs.
Hull .. 25 .. 125
Pins for starter .. .. .. 15
Two large wings and tail 571 .. .. 571
Buffer and steerer 53 .. .. 53
Propellers 250 .. .. 250
Total 874 25 .. 1014 =2.33lbs.
Grandtotal 874 75 ..
Density 0.8 3.0 ..
Volume (cu. cms.) 1092 25 ..
Alcohol .. .. 100 100
Water .. .. 500 500
Total .. .. ..
Density .. ..
Volume (cu. cm.) .. .. ..
Permanent air spaces:
in midrod, vol. = 355 cc. 4132
in engine frame, vol. = 100 cc. Density = = 1.65 III.
2505
volume as per II. 2050 cc.
2505 cc.
[p064]
The total flying weight of Old No. 4, including fuel and water, was 4132
grammes (9.1 lbs.), a much larger weight than had been contemplated when
the original designs were made. A detailed statement of the weights of the
various parts of the aerodrome, together with some data as to its density, is
Wood and Mica and Total and mean
Part. Fluid.
silk. asbestos. weights.
gms. gms. gms. gms.
Aeolipile .. .. .. 292
Boiler .. .. .. 387
Separator and pumps .. .. .. 450
Engine and frame .. .. .. 920
Midrod (200 cm. long) .. .. .. 220
Two smoke-stacks .. .. .. 70
Asbestos jacketing .. 50 .. 50
Air chamber .. .. .. 82
Spider between boiler and
.. .. .. 32
burner
Intake valve .. .. .. 15
Total .. 50 .. 2518 =5.54lbs.
Hull .. 25 .. 125
Pins for starter .. .. .. 15
Two large wings and tail 571 .. .. 571
Buffer and steerer 53 .. .. 53
Propellers 250 .. .. 250
Total 874 25 .. 1014 =2.33lbs.
Grandtotal 874 75 ..
Density 0.8 3.0 ..
Volume (cu. cms.) 1092 25 ..
Alcohol .. .. 100 100
Water .. .. 500 500
Total .. .. ..
Density .. ..
Volume (cu. cm.) .. .. ..
Permanent air spaces:
in midrod, vol. = 355 cc. 4132
in engine frame, vol. = 100 cc. Density = = 1.65 III.
2505
volume as per II. 2050 cc.
2505 cc.
[p064]
The total flying weight of Old No. 4, including fuel and water, was 4132
grammes (9.1 lbs.), a much larger weight than had been contemplated when
the original designs were made. A detailed statement of the weights of the
various parts of the aerodrome, together with some data as to its density, is
Page 118
given on the preceding page. There were provided in the wings and tail
approximately 2 sq. ft. of supporting surface to the pound of weight, which
would have been barely sufficient to sustain the aerodrome, even if it had
been successfully launched and the wings had been built much stronger
than the flimsy construction in use at this time.
An air chamber, which served the double purpose of floating the
aerodrome and of providing a moveable weight by which the center of
gravity could be shifted to the proper position relatively to the center of
pressure, was constructed of the thinnest sheet-iron and attached to the
midrod.
This aerodrome, the fifth in actual construction, and the first, after years
of experiment, to be carried into the field, was transported to Quantico,
where the first trial with it was made on November 20, under the conditions
described in Chapter IX ◊.
189 4
The aerodrome, No. 4, which has just been described, had not been put to
the test of an actual flight, for reasons connected with the difficulties of
launching, which are more fully described elsewhere; but, when the
completed machine was more fully studied in connection with the
unfavorable conditions which it was seen would be imposed on it in trials in
the open air, many possibilities for improvement presented themselves. It
was seen, for instance, that a better design might be made, in which the
engines, boiler and aeolipile might be placed so that the center of gravity of
each would lie in the same vertical plane as the central line of the
aerodrome. In order to do this the construction of a single midrod, which
was the distinguishing feature of Old No. 4, had to be essentially departed
from, the midrod of this new one, No. 5, being opened out into two rods, so
to speak, which were bent out so that the open space between them
furnished a sufficiently large hull space to hold the entire power generating
apparatus. In arranging the machinery within this hull, it was provided that,
as the water and fuel were expended, the center of gravity of the aerodrome
would shift little, and, if at all, backward relatively to the center of pressure.
approximately 2 sq. ft. of supporting surface to the pound of weight, which
would have been barely sufficient to sustain the aerodrome, even if it had
been successfully launched and the wings had been built much stronger
than the flimsy construction in use at this time.
An air chamber, which served the double purpose of floating the
aerodrome and of providing a moveable weight by which the center of
gravity could be shifted to the proper position relatively to the center of
pressure, was constructed of the thinnest sheet-iron and attached to the
midrod.
This aerodrome, the fifth in actual construction, and the first, after years
of experiment, to be carried into the field, was transported to Quantico,
where the first trial with it was made on November 20, under the conditions
described in Chapter IX ◊.
189 4
The aerodrome, No. 4, which has just been described, had not been put to
the test of an actual flight, for reasons connected with the difficulties of
launching, which are more fully described elsewhere; but, when the
completed machine was more fully studied in connection with the
unfavorable conditions which it was seen would be imposed on it in trials in
the open air, many possibilities for improvement presented themselves. It
was seen, for instance, that a better design might be made, in which the
engines, boiler and aeolipile might be placed so that the center of gravity of
each would lie in the same vertical plane as the central line of the
aerodrome. In order to do this the construction of a single midrod, which
was the distinguishing feature of Old No. 4, had to be essentially departed
from, the midrod of this new one, No. 5, being opened out into two rods, so
to speak, which were bent out so that the open space between them
furnished a sufficiently large hull space to hold the entire power generating
apparatus. In arranging the machinery within this hull, it was provided that,
as the water and fuel were expended, the center of gravity of the aerodrome
would shift little, and, if at all, backward relatively to the center of pressure.
Page 119
Instead of the two small engines, which it will be remembered were
mounted on the cross-frame in No. 4, a single engine with a larger cylinder,
having a diameter of 3.3 cm. (1.3 in.) and a stroke of 7 cm. (2.76 in.),
capable of developing about 1 H. P. was used. This engine was mounted
within the hull near the forward end and drove the propellers by suitable
gearing. [p065]
In addition to these radical changes many important improvements were
made in the different parts. Internal compartments were built in the
separator, so that even if the water was displaced by the pitching of the
aerodrome, it could still perform its functions properly. The pump was
provided with a ratchet, so that it could be worked by hand after the burners
were lighted, and before enough steam had been raised to enable the engine
to run it. An active circulation was thus maintained in the coils of the boiler
as soon as the burner was lighted and before the engine was started, which
prevented the tubing from being burnt out, as had frequently happened
previously. The wing construction was also improved and many other
changes were introduced, which will be treated separately.
In the meantime, No. 4, which had been damaged in the attempted
launching in November, 1893, was strengthened and prepared for another
trial which took place in January, 1894.
By the end of the first week in February, the engine of No. 5 was ready
for trial, and with a boiler pressure of about 80 pounds per square inch,
apparently developed 0.56 H. P. on the Prony brake, when making 800
revolutions per minute. To accomplish this called for such good distribution
of steam in the cylinder, that it is doubtful if the power could be exceeded at
that speed and pressure.
It was, however, apparent that it was desirable to have a boiler capable of
supplying steam for at least one horse-power, and that in order to do this,
there must be an improvement in the aeolipiles. The problem consisted in
arranging to evaporate more than 500 cu. cm., and in fact as nearly as
possible 1000 cu. cm. (61 cu. in.) of water per minute, and, since from 200
to 300 cu. cm. per minute had already been evaporated, this was not
regarded as impossible of accomplishment. The theoretical advantages of
mounted on the cross-frame in No. 4, a single engine with a larger cylinder,
having a diameter of 3.3 cm. (1.3 in.) and a stroke of 7 cm. (2.76 in.),
capable of developing about 1 H. P. was used. This engine was mounted
within the hull near the forward end and drove the propellers by suitable
gearing. [p065]
In addition to these radical changes many important improvements were
made in the different parts. Internal compartments were built in the
separator, so that even if the water was displaced by the pitching of the
aerodrome, it could still perform its functions properly. The pump was
provided with a ratchet, so that it could be worked by hand after the burners
were lighted, and before enough steam had been raised to enable the engine
to run it. An active circulation was thus maintained in the coils of the boiler
as soon as the burner was lighted and before the engine was started, which
prevented the tubing from being burnt out, as had frequently happened
previously. The wing construction was also improved and many other
changes were introduced, which will be treated separately.
In the meantime, No. 4, which had been damaged in the attempted
launching in November, 1893, was strengthened and prepared for another
trial which took place in January, 1894.
By the end of the first week in February, the engine of No. 5 was ready
for trial, and with a boiler pressure of about 80 pounds per square inch,
apparently developed 0.56 H. P. on the Prony brake, when making 800
revolutions per minute. To accomplish this called for such good distribution
of steam in the cylinder, that it is doubtful if the power could be exceeded at
that speed and pressure.
It was, however, apparent that it was desirable to have a boiler capable of
supplying steam for at least one horse-power, and that in order to do this,
there must be an improvement in the aeolipiles. The problem consisted in
arranging to evaporate more than 500 cu. cm., and in fact as nearly as
possible 1000 cu. cm. (61 cu. in.) of water per minute, and, since from 200
to 300 cu. cm. per minute had already been evaporated, this was not
regarded as impossible of accomplishment. The theoretical advantages of
Page 120
gasoline had for a long time been recognized, as well as the very practical
advantage possessed by it of keeping lighted in a breeze, and several
attempts had been made during the latter part of the previous year to
construct a suitable burner for use with it. These had not been very
successful; but in view of the increasing demand for a flame of greater
efficiency than that of the alcohol aeolipiles, it was decided to resume the
experiments with it.
Accordingly, a gasoline evaporator was tried, consisting in the first
experiment of a gasoline tank with nine flues, through which steam was
passed. A flow of steam gave a rapid evaporation of gasoline when the
pressure did not exceed 5 pounds. The chief difficulty with the burner
employed was that the supply of gasoline gas would rise and fall as the
steam rose and fell, conditions just the opposite of what was really desired.
On the other hand, it was thought that this gasoline tank would form a real
condenser for the steam, so that a [p066] portion of the exhaust steam would
be condensed and be available for use in the boiler again. The gasoline
vapor had many advantages over the alcohol; but it was at first possible to
evaporate only 120 cu. cm. of gasoline in a minute.
In the experiments that were made at this time (March 9) with gasoline,
the main object in view was to obtain a smooth blue flame at 10 pounds
pressure. There had been failures to accomplish this, owing to the high
boiling point of the liquid, and while the work was in progress it was still
evident that the problem of the boiler and the flame which was to heat it had
not been solved. A Prony brake test gave, at 130 pounds pressure, 1.1 H. P.
with about 1000 revolutions of the propellers; but this was with steam
supplied from the boiler of the stationary shop engine.
On April 1, 1894, the following record was made of the condition of
Aerodrome No. 5:
“The wings, the tail, and the two 80 cm. propellers, as well as the two smaller propellers, are
ready. The cylinders, gear, pump, and every essential of the running gear, are in place. The boilers,
separators, and adjuncts are still under experiment, but may be hoped to be ready in a few days. At
present, the boilers give from 450 to 600 grammes of mixed steam and water per minute. With 130
pounds of steam, the engine has actually developed at the brake, without cut-off, considerably
more than 1 H. P., so that it may be confidently considered that at 150 pounds, with cut-off, it will
give at least 0.8 H. P., if it works proportionately well.”
advantage possessed by it of keeping lighted in a breeze, and several
attempts had been made during the latter part of the previous year to
construct a suitable burner for use with it. These had not been very
successful; but in view of the increasing demand for a flame of greater
efficiency than that of the alcohol aeolipiles, it was decided to resume the
experiments with it.
Accordingly, a gasoline evaporator was tried, consisting in the first
experiment of a gasoline tank with nine flues, through which steam was
passed. A flow of steam gave a rapid evaporation of gasoline when the
pressure did not exceed 5 pounds. The chief difficulty with the burner
employed was that the supply of gasoline gas would rise and fall as the
steam rose and fell, conditions just the opposite of what was really desired.
On the other hand, it was thought that this gasoline tank would form a real
condenser for the steam, so that a [p066] portion of the exhaust steam would
be condensed and be available for use in the boiler again. The gasoline
vapor had many advantages over the alcohol; but it was at first possible to
evaporate only 120 cu. cm. of gasoline in a minute.
In the experiments that were made at this time (March 9) with gasoline,
the main object in view was to obtain a smooth blue flame at 10 pounds
pressure. There had been failures to accomplish this, owing to the high
boiling point of the liquid, and while the work was in progress it was still
evident that the problem of the boiler and the flame which was to heat it had
not been solved. A Prony brake test gave, at 130 pounds pressure, 1.1 H. P.
with about 1000 revolutions of the propellers; but this was with steam
supplied from the boiler of the stationary shop engine.
On April 1, 1894, the following record was made of the condition of
Aerodrome No. 5:
“The wings, the tail, and the two 80 cm. propellers, as well as the two smaller propellers, are
ready. The cylinders, gear, pump, and every essential of the running gear, are in place. The boilers,
separators, and adjuncts are still under experiment, but may be hoped to be ready in a few days. At
present, the boilers give from 450 to 600 grammes of mixed steam and water per minute. With 130
pounds of steam, the engine has actually developed at the brake, without cut-off, considerably
more than 1 H. P., so that it may be confidently considered that at 150 pounds, with cut-off, it will
give at least 0.8 H. P., if it works proportionately well.”
Page 121
The delays incident to the accomplishment of the work in hand were
always greater than anticipated, as is instanced by the fact that it was the
latter part of September before the work was actually completed. The
greater part of this delay was due to the necessity for a constant series of
experiments during the spring and summer to determine the power that it
was possible to obtain with the various styles of boilers, aeolipiles, and
gasoline burners.
While No. 5 was thus under construction, new and somewhat larger
engines had been built for No. 4, the work on them having been begun in
January. The cylinders of these engines, which are more fully described in
connection with Aerodrome No. 6, were 2.8 cm. in diameter, with a 5 cm.
stroke, each cylinder thus having a capacity of 30.8 cu. cm., which was an
increase of 36 per cent over that of the old brass cylinder engines, which
had previously been used on No. 4. On April 28, under a pressure of 70
pounds, these engines drove the two 60 cm. propellers at a rate of 900 R. P.
M., and lifted on the pendulum nearly 40 per cent of the total flying weight
of Aerodrome No. 4, which was now approximately 5 kilos. A trial was
made at Quantico in the latter part of May, which is described in Chapter IX
◊. It is only necessary to mention in this connection that there was a great
deal of trouble experienced with the alcohol aeolipile, the flame being
extinguished in the moderate wind to which the [p067] aerodrome was
subjected while preparations for the launch were being made. Moreover the
flame was so nearly invisible in the sunlight that it was uncertain whether it
was burning in the critical instants just before the launch, when doubt might
be fatal. These conditions resulted in a final decision in favor of gasoline,
on account of its greater inflammability, and in the provision of such hull
covering that the fires could be lighted and maintained in a breeze.
In June, I tried a modification of the burner, in which the gasoline was
delivered under the pressure of air to the evaporating coil. In the first trial
steam was raised to a final pressure of about 70 pounds, and a run of 45
seconds was secured under a pressure of 40 pounds in the gasoline tank,
which was thought to be altogether too high; for, at the end of the run, the
always greater than anticipated, as is instanced by the fact that it was the
latter part of September before the work was actually completed. The
greater part of this delay was due to the necessity for a constant series of
experiments during the spring and summer to determine the power that it
was possible to obtain with the various styles of boilers, aeolipiles, and
gasoline burners.
While No. 5 was thus under construction, new and somewhat larger
engines had been built for No. 4, the work on them having been begun in
January. The cylinders of these engines, which are more fully described in
connection with Aerodrome No. 6, were 2.8 cm. in diameter, with a 5 cm.
stroke, each cylinder thus having a capacity of 30.8 cu. cm., which was an
increase of 36 per cent over that of the old brass cylinder engines, which
had previously been used on No. 4. On April 28, under a pressure of 70
pounds, these engines drove the two 60 cm. propellers at a rate of 900 R. P.
M., and lifted on the pendulum nearly 40 per cent of the total flying weight
of Aerodrome No. 4, which was now approximately 5 kilos. A trial was
made at Quantico in the latter part of May, which is described in Chapter IX
◊. It is only necessary to mention in this connection that there was a great
deal of trouble experienced with the alcohol aeolipile, the flame being
extinguished in the moderate wind to which the [p067] aerodrome was
subjected while preparations for the launch were being made. Moreover the
flame was so nearly invisible in the sunlight that it was uncertain whether it
was burning in the critical instants just before the launch, when doubt might
be fatal. These conditions resulted in a final decision in favor of gasoline,
on account of its greater inflammability, and in the provision of such hull
covering that the fires could be lighted and maintained in a breeze.
In June, I tried a modification of the burner, in which the gasoline was
delivered under the pressure of air to the evaporating coil. In the first trial
steam was raised to a final pressure of about 70 pounds, and a run of 45
seconds was secured under a pressure of 40 pounds in the gasoline tank,
which was thought to be altogether too high; for, at the end of the run, the
Page 122
whole apparatus was enveloped in flames, because of the gasoline that was
projected through the burner-tips.
Continual experiments with different forms of burner, illustrated in Plate
12, occupied the time, with delays and imperfect results, which were trying
to the investigator, but are omitted as of little interest to the reader. They
had, however, the incidental result of proving the practical superiority of
gasoline over alcohol, and culminated in the evolution of the burner that
was finally used successfully. It consisted of a tank for the gasoline, from
which compressed air delivered the liquid to a small coil surrounded by
asbestos, in which it was vaporized. At the rear end of this coil three pipes
were led off, one of which was a small “bleeder,” which fed the burner for
heating the gasoline, the other two leading to the main burners. After the
generation of gas in the small coil had been started, the heat from the small
burner was expected to continue the vaporization, so that nothing but gas
would be able to reach the main burners. A device was also introduced,
which had greatly increased the amount and uniformity of the draft and
consequently made the burners and boilers more efficient than before. This
consisted simply in passing the exhaust steam from the engines into the
smoke-stack, and it is remarkable that it was not thought of earlier.
By the middle of September, 1894, both aerodromes were completed and
ready for another test. On September 27 the condition of Aerodrome No. 4
was as follows: The general type of construction, namely, that of a single
midrod, to which all the steam generating apparatus was attached, and
which supported also the cross-frame and the wings, was the same as in the
construction of 1893. On account of the increased weight of the model, and
the substitution of an inferior piece of tubing in place of the former midrod,
it was found necessary to stiffen it by the use of temporary trusses.
Permanent bearing points for holding the aerodrome securely to the newly
devised launching apparatus were also attached to this midrod. [p068]
The engines in use at this time were the small steel cylinders described
above, which were mounted on the cross-frame, and drove the propellers
directly. These engines were capable of delivering to the propellers, as had
been proved by repeated tests, at least 0.66 brake horse-power.
projected through the burner-tips.
Continual experiments with different forms of burner, illustrated in Plate
12, occupied the time, with delays and imperfect results, which were trying
to the investigator, but are omitted as of little interest to the reader. They
had, however, the incidental result of proving the practical superiority of
gasoline over alcohol, and culminated in the evolution of the burner that
was finally used successfully. It consisted of a tank for the gasoline, from
which compressed air delivered the liquid to a small coil surrounded by
asbestos, in which it was vaporized. At the rear end of this coil three pipes
were led off, one of which was a small “bleeder,” which fed the burner for
heating the gasoline, the other two leading to the main burners. After the
generation of gas in the small coil had been started, the heat from the small
burner was expected to continue the vaporization, so that nothing but gas
would be able to reach the main burners. A device was also introduced,
which had greatly increased the amount and uniformity of the draft and
consequently made the burners and boilers more efficient than before. This
consisted simply in passing the exhaust steam from the engines into the
smoke-stack, and it is remarkable that it was not thought of earlier.
By the middle of September, 1894, both aerodromes were completed and
ready for another test. On September 27 the condition of Aerodrome No. 4
was as follows: The general type of construction, namely, that of a single
midrod, to which all the steam generating apparatus was attached, and
which supported also the cross-frame and the wings, was the same as in the
construction of 1893. On account of the increased weight of the model, and
the substitution of an inferior piece of tubing in place of the former midrod,
it was found necessary to stiffen it by the use of temporary trusses.
Permanent bearing points for holding the aerodrome securely to the newly
devised launching apparatus were also attached to this midrod. [p068]
The engines in use at this time were the small steel cylinders described
above, which were mounted on the cross-frame, and drove the propellers
directly. These engines were capable of delivering to the propellers, as had
been proved by repeated tests, at least 0.66 brake horse-power.
Page 123
The boiler consisted of two inner coils and an enveloping outer coil,
loosely wound and connected in series. The inner coils, each of which had
about 17 turns of 8 mm. diameter, 0.2 mm. thick tubing, developed about 80
per cent of the steam; the outer coil of 8 turns, while not exactly useless as a
steam generator, afforded an efficient means of fastening the smoke-stack
and cover of the boiler, and for attaching the latter to the midrod. This
boiler was externally 30 cm. long, 16 cm. wide, and 10 cm. deep, weighing
with its cover approximately 650 grammes. The stack for the burnt gases,
into which exhaust steam was led from a central jet, was about 1 foot long.
At best this boiler was capable of developing slightly over 100 pounds of
steam.
The separator was of the form last described, except that the steam dome
had been moved toward the front, to prevent the jerk of the launching car in
starting from causing water to be pitched over into the engines. It was
constructed of sheet aluminum-bronze, and weighed, together with its
pump, 580 grammes. The pump, which was double-acting and fitted with
ball valves, was capable of discharging 4.5 grammes of cold water per
stroke, its efficiency being only about one-half as great with hot water.
The gasoline burner, which had been finally adopted in place of the
alcohol aeolipiles, had now been perfected to the form in which it was
finally used. Two Bunsen burners of special construction were provided
with gasoline gas by the heat of an intermediate accessory burner, which
played upon a coil to which all three burners were connected. Gasoline was
furnished from a tank made of aluminum-bronze, under an air pressure of
about 20 pounds, the fluid being under the control of a screw stop-cock.
This tank, which was capable of holding 100 to 150 cu. cm. of gasoline,
weighed 180 grammes, and the burners with an outer sheathing weighed
302 grammes.
It was calculated that about 3300 cu. cm. (201 cu. in.) of air space would
be required to float the aerodrome in water, and this was supplied by an air
chamber, having a capacity of 2700 cu. cm. (165 cu. in.), which could be
shifted to adjust the longitudinal equilibrium of the aerodrome, and about
900 cu. cm. (55 cu. in.) of space in the gasoline tank and the midrod. The
loosely wound and connected in series. The inner coils, each of which had
about 17 turns of 8 mm. diameter, 0.2 mm. thick tubing, developed about 80
per cent of the steam; the outer coil of 8 turns, while not exactly useless as a
steam generator, afforded an efficient means of fastening the smoke-stack
and cover of the boiler, and for attaching the latter to the midrod. This
boiler was externally 30 cm. long, 16 cm. wide, and 10 cm. deep, weighing
with its cover approximately 650 grammes. The stack for the burnt gases,
into which exhaust steam was led from a central jet, was about 1 foot long.
At best this boiler was capable of developing slightly over 100 pounds of
steam.
The separator was of the form last described, except that the steam dome
had been moved toward the front, to prevent the jerk of the launching car in
starting from causing water to be pitched over into the engines. It was
constructed of sheet aluminum-bronze, and weighed, together with its
pump, 580 grammes. The pump, which was double-acting and fitted with
ball valves, was capable of discharging 4.5 grammes of cold water per
stroke, its efficiency being only about one-half as great with hot water.
The gasoline burner, which had been finally adopted in place of the
alcohol aeolipiles, had now been perfected to the form in which it was
finally used. Two Bunsen burners of special construction were provided
with gasoline gas by the heat of an intermediate accessory burner, which
played upon a coil to which all three burners were connected. Gasoline was
furnished from a tank made of aluminum-bronze, under an air pressure of
about 20 pounds, the fluid being under the control of a screw stop-cock.
This tank, which was capable of holding 100 to 150 cu. cm. of gasoline,
weighed 180 grammes, and the burners with an outer sheathing weighed
302 grammes.
It was calculated that about 3300 cu. cm. (201 cu. in.) of air space would
be required to float the aerodrome in water, and this was supplied by an air
chamber, having a capacity of 2700 cu. cm. (165 cu. in.), which could be
shifted to adjust the longitudinal equilibrium of the aerodrome, and about
900 cu. cm. (55 cu. in.) of space in the gasoline tank and the midrod. The
Page 124
reel and float, which served to indicate the location of the aerodrome, if for
any reason it should be submerged, were in one piece, and so moored that
there was no danger of fouling the propellers.
The total weight of the aerodrome was about 6 kilogrammes (13.2 lbs.),
or, with a maximum quantity of fuel (850 cu. cm. of water, 150 cu. cm. of
gasoline), [p069] less than 7 kilogrammes. From 60 to 90 pounds of steam
could be maintained by the boilers for about 2 minutes, at which pressure
the engines developed about 0.66 brake horse-power, driving the 70 cm.,
1.25 pitch-ratio propellers at 700 R. P. M., and giving a lift of from 2.6 to
3.0 kilos (5.7 to 6.6 pounds), or about 40 per cent of the flying weight.
The wings and tail had a total surface of 2.62 sq. m. (28.2 sq. ft.), giving
a ratio of 2.7 kilos to 1 sq. m. of wing surface (1.8 sq. ft. per pound). If the
hull resistance be neglected, the soaring speed of this aerodrome was about
5.9 metres (19 feet) per second, or 13 miles per hour.
Turning now to the completed No. 5, its frame was of the “double
midrod” type described above, the two tubes which formed the frame being
prolonged at the front and rear to afford points of attachment for the wings
and tail. The range through which the wings could be shifted to adjust the
position of the center of pressure was, however, very small. The hull,
which, it will be remembered, contained all the power generating apparatus,
was much stronger and heavier than that of No. 4, and resembled somewhat
the hull of a ship. It had a frame-work of steel tubing brazed to the midrod,
to which an outer sheathing of sheet aluminum 0.3 mm. thick was attached.
It was, however, excessively heavy, weighing nearly 800 grammes.
The engine, which was mounted near the front of the hull, was the single
cylinder, one horse-power engine, described above, which drove the two
propellers by suitable gearing. The remaining parts of the power plant were
identical with those already described in connection with No. 4, but the
more advantageous location of them in No. 5 rendered them somewhat
more efficient.
It had been planned to use 80 cm. propellers of 1.25 pitch-ratio on No. 5,
but it was found in the shop tests of the aerodrome that the cross-frame was
not strong enough to withstand the strains, and that the engine could be
any reason it should be submerged, were in one piece, and so moored that
there was no danger of fouling the propellers.
The total weight of the aerodrome was about 6 kilogrammes (13.2 lbs.),
or, with a maximum quantity of fuel (850 cu. cm. of water, 150 cu. cm. of
gasoline), [p069] less than 7 kilogrammes. From 60 to 90 pounds of steam
could be maintained by the boilers for about 2 minutes, at which pressure
the engines developed about 0.66 brake horse-power, driving the 70 cm.,
1.25 pitch-ratio propellers at 700 R. P. M., and giving a lift of from 2.6 to
3.0 kilos (5.7 to 6.6 pounds), or about 40 per cent of the flying weight.
The wings and tail had a total surface of 2.62 sq. m. (28.2 sq. ft.), giving
a ratio of 2.7 kilos to 1 sq. m. of wing surface (1.8 sq. ft. per pound). If the
hull resistance be neglected, the soaring speed of this aerodrome was about
5.9 metres (19 feet) per second, or 13 miles per hour.
Turning now to the completed No. 5, its frame was of the “double
midrod” type described above, the two tubes which formed the frame being
prolonged at the front and rear to afford points of attachment for the wings
and tail. The range through which the wings could be shifted to adjust the
position of the center of pressure was, however, very small. The hull,
which, it will be remembered, contained all the power generating apparatus,
was much stronger and heavier than that of No. 4, and resembled somewhat
the hull of a ship. It had a frame-work of steel tubing brazed to the midrod,
to which an outer sheathing of sheet aluminum 0.3 mm. thick was attached.
It was, however, excessively heavy, weighing nearly 800 grammes.
The engine, which was mounted near the front of the hull, was the single
cylinder, one horse-power engine, described above, which drove the two
propellers by suitable gearing. The remaining parts of the power plant were
identical with those already described in connection with No. 4, but the
more advantageous location of them in No. 5 rendered them somewhat
more efficient.
It had been planned to use 80 cm. propellers of 1.25 pitch-ratio on No. 5,
but it was found in the shop tests of the aerodrome that the cross-frame was
not strong enough to withstand the strains, and that the engine could be
Page 125
made to work much more steadily with a smaller propeller. Accordingly,
propellers of 70 cm. diameter and 1.25 pitch-ratio, similar to those used on
No. 4, were finally substituted.
For floating the aerodrome, when it descended into the water, an air-
chamber similar to that of No. 4, but of a larger capacity was provided.
With this in place on the aerodrome, it was calculated that, if all the parts
except this float and the gasoline tank were filled with water, there would
still be a buoyancy of over 2 kilogrammes.
The total weight of No. 5 was 8200 grammes, or with its full supply of
fuel and water 9200 grammes. In this aerodrome the same boilers used in
No. 4 were capable of maintaining for at least a minute 115 pounds of
steam, so that the engine now gave the maximum of one brake horse-power
for which it was designed, and, driving the 70 cm. propellers, lifted
repeatedly nearly 45 per cent of the flying weight. [p070]
The wings and tail constructed for No. 5 were identical with those of No.
4, being slightly curved and containing 2.62 sq. m. (28.2 sq. ft.), equivalent
to 1.4 sq. ft. to the pound, which with the flimsy construction of the wings
gave an entirely inadequate support to the aerodrome.
During the summer a launching apparatus of a new and improved type,
which is described in Chapter X ◊, had been perfected, and with it repeated
tests were made of both aerodromes in October, November, and December,
with the unsatisfactory results recorded in Chapter IX ◊. In the course of
these experiments, many slight modifications of the burners and boilers
were made, but no important changes were introduced except that the cross-
frame of No. 5 was enlarged and strengthened so as to admit of its carrying
one metre propellers safely. The results, however, which were obtained, did
not compensate for the increased weight of the larger frame.
Viewing the work of this year from the standpoint of results obtained in
the numerous attempts at flight, it would seem that very little progress had
been made, and that there was small reason to expect to achieve final
success. However, if the work be examined more particularly, it will be seen
that two of the most difficult problems had been solved, one completely as
far as the models were concerned, and the other to a very satisfactory
propellers of 70 cm. diameter and 1.25 pitch-ratio, similar to those used on
No. 4, were finally substituted.
For floating the aerodrome, when it descended into the water, an air-
chamber similar to that of No. 4, but of a larger capacity was provided.
With this in place on the aerodrome, it was calculated that, if all the parts
except this float and the gasoline tank were filled with water, there would
still be a buoyancy of over 2 kilogrammes.
The total weight of No. 5 was 8200 grammes, or with its full supply of
fuel and water 9200 grammes. In this aerodrome the same boilers used in
No. 4 were capable of maintaining for at least a minute 115 pounds of
steam, so that the engine now gave the maximum of one brake horse-power
for which it was designed, and, driving the 70 cm. propellers, lifted
repeatedly nearly 45 per cent of the flying weight. [p070]
The wings and tail constructed for No. 5 were identical with those of No.
4, being slightly curved and containing 2.62 sq. m. (28.2 sq. ft.), equivalent
to 1.4 sq. ft. to the pound, which with the flimsy construction of the wings
gave an entirely inadequate support to the aerodrome.
During the summer a launching apparatus of a new and improved type,
which is described in Chapter X ◊, had been perfected, and with it repeated
tests were made of both aerodromes in October, November, and December,
with the unsatisfactory results recorded in Chapter IX ◊. In the course of
these experiments, many slight modifications of the burners and boilers
were made, but no important changes were introduced except that the cross-
frame of No. 5 was enlarged and strengthened so as to admit of its carrying
one metre propellers safely. The results, however, which were obtained, did
not compensate for the increased weight of the larger frame.
Viewing the work of this year from the standpoint of results obtained in
the numerous attempts at flight, it would seem that very little progress had
been made, and that there was small reason to expect to achieve final
success. However, if the work be examined more particularly, it will be seen
that two of the most difficult problems had been solved, one completely as
far as the models were concerned, and the other to a very satisfactory
Page 126
degree. First, a launching apparatus, with which it was possible to give the
aerodrome any desired initial velocity, had been devised, and so far
perfected that no trouble was ever experienced with it in testing the models.
Second, as a result of the extended and systematic series of experiments,
which had been conducted under the direction of Dr. Barus, a steam
pressure of 115 pounds could be maintained steadily in the boilers for at
least a minute, and the burners could be kept lighted even in a considerable
breeze.
A summary of these experiments, together with some account of the
difficulties encountered and the results finally obtained with the apparatus
in use at the end of the year, is given in the following report, which was
prepared by Dr. Barus in December, 1894.
“If water be sprayed upon a surface kept in a permanent state of ignition, any quantity of steam
might be generated per time unit. Similarly advantageous conditions would be given if threads of
water could be passed through a flame. In practice this method would encounter two serious
difficulties, the importance of which is accentuated when the boiler apparatus is to be kept within
the degree of lightness essential in aerodromics. These difficulties are (1) the danger of chilling the
flame below the point of ignition or of combustion of the gases, and (2) the practical impossibility
of maintaining threads of water in the flame. For it is clear that the threads must be joined in
multiple arc, so as to allow a large bulk of water to circulate through the boiler, whereas even when
there are but two independent passages for the water through the furnace, it is hard to keep both
supplied with liquid without unduly straining the pump. If the water be even slightly deficient,
circumstances will arise in which one of [p071] the passages is better than the other. This conduit
will then generate more steam and drive the water under force through the other passage,
increasing the temperature discrepancy between them. Eventually the hot passage reaches ignition
and either bursts or melts. This is what sooner or later takes place in boilers adapted for flying
machines and consisting of tubes joined in multiple arc, when a single moderately strong
circulating pump supplies the system.
“To avoid these annoyances, i. e., to increase the length of life of the boiler, the boiler tubes are
joined in series to the effect that a single current of water may flow successively through all of
them. It is needful therefore to select wide tubes, such as will admit of an easy circulation in
consideration of the length of tubing employed without straining the pump and at the same time to
allow sufficient room for the efflux of steam. Other considerations enter here, the bearing of which
will be seen presently: if the tube be too wide the difficulty of coiling it on a mandrel of small
diameter is increased, while at the same time the tube loses strength (cæt. par. ) in virtue of the
increased width.
aerodrome any desired initial velocity, had been devised, and so far
perfected that no trouble was ever experienced with it in testing the models.
Second, as a result of the extended and systematic series of experiments,
which had been conducted under the direction of Dr. Barus, a steam
pressure of 115 pounds could be maintained steadily in the boilers for at
least a minute, and the burners could be kept lighted even in a considerable
breeze.
A summary of these experiments, together with some account of the
difficulties encountered and the results finally obtained with the apparatus
in use at the end of the year, is given in the following report, which was
prepared by Dr. Barus in December, 1894.
“If water be sprayed upon a surface kept in a permanent state of ignition, any quantity of steam
might be generated per time unit. Similarly advantageous conditions would be given if threads of
water could be passed through a flame. In practice this method would encounter two serious
difficulties, the importance of which is accentuated when the boiler apparatus is to be kept within
the degree of lightness essential in aerodromics. These difficulties are (1) the danger of chilling the
flame below the point of ignition or of combustion of the gases, and (2) the practical impossibility
of maintaining threads of water in the flame. For it is clear that the threads must be joined in
multiple arc, so as to allow a large bulk of water to circulate through the boiler, whereas even when
there are but two independent passages for the water through the furnace, it is hard to keep both
supplied with liquid without unduly straining the pump. If the water be even slightly deficient,
circumstances will arise in which one of [p071] the passages is better than the other. This conduit
will then generate more steam and drive the water under force through the other passage,
increasing the temperature discrepancy between them. Eventually the hot passage reaches ignition
and either bursts or melts. This is what sooner or later takes place in boilers adapted for flying
machines and consisting of tubes joined in multiple arc, when a single moderately strong
circulating pump supplies the system.
“To avoid these annoyances, i. e., to increase the length of life of the boiler, the boiler tubes are
joined in series to the effect that a single current of water may flow successively through all of
them. It is needful therefore to select wide tubes, such as will admit of an easy circulation in
consideration of the length of tubing employed without straining the pump and at the same time to
allow sufficient room for the efflux of steam. Other considerations enter here, the bearing of which
will be seen presently: if the tube be too wide the difficulty of coiling it on a mandrel of small
diameter is increased, while at the same time the tube loses strength (cæt. par. ) in virtue of the
increased width.
Page 127
Diagram 1. Diagram 2.
FIG. 11.
“It is from considerations such as these that, in the course of many experiments, copper tubing
about 8 mm. in diameter has been adopted. Copper is selected because of its freedom from internal
corrosion, easy coiling, and because of its availability in the market. The thinnest tube to be had
(walls only 0.1 mm. thick) will withstand more pressure than can be entrusted to the larger steam
receivers in circuit with the boiler. The boiler weight is thus a negligible factor, and it is quite
feasible to reduce the thickness of boiler tubing, by the superficial application of moderately strong
nitric acid, to 200–400 grammes per horse-power of steam supplied. External corrosion due to
flames occurs only in case of deficient water, and if the boiler be made of tubing with the walls 0.2
mm. thick, it is in view of the possibility of such accidents. Boilers may then be tested to 25 atm.
without endangering the metal.
“Boilers are wound or coiled with regard to the two points above suggested, viz.: to avoid
chilling the flame the successive turns are spaced on all sides, and to bring the water as nearly into
the flame as possible, the diameter of the coils is chosen as small as expedient. Further reasons for
this will presently be adduced. The type of boiler eventually adopted is shown in the
accompanying diagrams, 1 and 2, Fig. 11.
“Diagram 1, is a perspective diagram showing the plan of winding and Diagram 2, an end view.
The circulation is indicated. There are two inner coils [p072] each containing about 17 turns,
wound on a mandrel 5 cm. in diameter. The turns are spaced so as to allow about 1 cm. clear
between successive turns. The outer coil envelopes both, and in this there are about 3 cm. between
successive turns, and 8 turns in all. Length, say, 30 cm., breadth 16 cm., thickness 10 cm., give the
external dimensions of the boiler. The shell space between outer and inner layers of tubing must
nowhere be less than 1 cm. When so wound, the inner coils (here as in other boiler forms) raise
about 80 per cent or more of the steam; the outer or enveloping coil, while not quite useless, make
the most effective frame work for the boiler jacket which has been devised. The coils are brazed
together by blind tubes, as shown in Diagram 2, to keep the whole in shape. Weight with couplings
and cover when complete 535 grammes.
“The cover is preferably of mica, through which the flame within the boiler may be seen, and in
which lightness, nonconduction, and resistance to the disintegrating effects of high temperature are
FIG. 11.
“It is from considerations such as these that, in the course of many experiments, copper tubing
about 8 mm. in diameter has been adopted. Copper is selected because of its freedom from internal
corrosion, easy coiling, and because of its availability in the market. The thinnest tube to be had
(walls only 0.1 mm. thick) will withstand more pressure than can be entrusted to the larger steam
receivers in circuit with the boiler. The boiler weight is thus a negligible factor, and it is quite
feasible to reduce the thickness of boiler tubing, by the superficial application of moderately strong
nitric acid, to 200–400 grammes per horse-power of steam supplied. External corrosion due to
flames occurs only in case of deficient water, and if the boiler be made of tubing with the walls 0.2
mm. thick, it is in view of the possibility of such accidents. Boilers may then be tested to 25 atm.
without endangering the metal.
“Boilers are wound or coiled with regard to the two points above suggested, viz.: to avoid
chilling the flame the successive turns are spaced on all sides, and to bring the water as nearly into
the flame as possible, the diameter of the coils is chosen as small as expedient. Further reasons for
this will presently be adduced. The type of boiler eventually adopted is shown in the
accompanying diagrams, 1 and 2, Fig. 11.
“Diagram 1, is a perspective diagram showing the plan of winding and Diagram 2, an end view.
The circulation is indicated. There are two inner coils [p072] each containing about 17 turns,
wound on a mandrel 5 cm. in diameter. The turns are spaced so as to allow about 1 cm. clear
between successive turns. The outer coil envelopes both, and in this there are about 3 cm. between
successive turns, and 8 turns in all. Length, say, 30 cm., breadth 16 cm., thickness 10 cm., give the
external dimensions of the boiler. The shell space between outer and inner layers of tubing must
nowhere be less than 1 cm. When so wound, the inner coils (here as in other boiler forms) raise
about 80 per cent or more of the steam; the outer or enveloping coil, while not quite useless, make
the most effective frame work for the boiler jacket which has been devised. The coils are brazed
together by blind tubes, as shown in Diagram 2, to keep the whole in shape. Weight with couplings
and cover when complete 535 grammes.
“The cover is preferably of mica, through which the flame within the boiler may be seen, and in
which lightness, nonconduction, and resistance to the disintegrating effects of high temperature are
Page 128
met with in a pronounced degree. This jacket is held down by copper bands and the end band is
continuous with the long smoke-stack, as will be presently shown.
“The wide form of boiler with two coils within the envelope is not absolutely essential. The
same amount of steam can be generated from one coil in an envelope in other respects equal to
Diagram 1 if a sufficiently hot flame be passed axially through the coils. Such a flame, however, is
unstable, and for this reason two milder flames with a good air access are to be preferred on
practical grounds even if the weight is thereby increased.
“To further understand the boiler construction it is advisable to consider the action of the flame.
Inasmuch as wide tubes must be used, the problem of evaporating water as fast as possible is
equivalent to getting heat into the current (water and steam circulating through the coils) as fast as
possible from without. If, therefore, t is the mean temperature of the fluids within the coils, and T
the effective temperature surrounding the tube, then the rate at which heat will flow into the tubes
is proportional to T−t. Now t the temperature of the steam is nearly constant (100°–150°) whereas
T the effective flame temperature may vary from 800° to, say, 1600°. It is for this reason that the
heat sponged up by the boiler depends almost directly on the flame temperature.
“What conditions, therefore, will make the flame effectively hot?
“(1) The coils must obviously be brought as nearly into the flame as feasible: for this purpose
the cylindrical helix is better than any other form. But
“(2) The turns and coils must not be so crowded together as to chill the flame into imperfect
combustion in various parts of its extent. Hence the loose form of winding. Again
“(3) There must be oxygen enough to allow complete combustion, and
“(4) The flame itself must be hot and the radiation checked by good jacketing.
“To take up the last points: the effective heat of the flame depends not only on the combustion
heat of the fuel used; it depends also, among other things, on the speed with which this combustion
takes place. A flame burning from a low pressure of alcohol gas will be at low temperature as
compared with a flame burning from high pressures of the gas. If the flame be burnt from a
Bunsen burner in the usual way it is an interesting question to know how flame temperature will
vary with gas pressure. At present we know it merely in steam pressures incidently produced in a
given engine (No. 4) as for instance:
Flame pressure, 10 lbs., 20 lbs., 30 lbs.
Steam pressure, 40 lbs., 80 lbs., 120 lbs.
in the running engine.
[p073]
“Unfortunately there is a limit set to this process of increasing the steam supply, quite aside
from conditions inherent in the method. This is due to the fact that a certain speed of efflux cannot
be exceeded without putting the flame out. Suppose, for instance, in Fig. 12, that a gas generated
from a liquid is ignited at the end of the Bunsen burner F ; then if the velocity of efflux of mixed
gas and air in the direction AB from the mouth of F exceeds the velocity of combustion in the
direction BA, the flame will obviously be carried away from the mouth of the tube and dissipated.
This state of things is actually realized at pressures exceeding about 15 lbs., depending on the
degree of mixture of the combustible gases used, and therefore on apparently haphazard conditions
connected with the jet, the air holes, the air supply, etc.
continuous with the long smoke-stack, as will be presently shown.
“The wide form of boiler with two coils within the envelope is not absolutely essential. The
same amount of steam can be generated from one coil in an envelope in other respects equal to
Diagram 1 if a sufficiently hot flame be passed axially through the coils. Such a flame, however, is
unstable, and for this reason two milder flames with a good air access are to be preferred on
practical grounds even if the weight is thereby increased.
“To further understand the boiler construction it is advisable to consider the action of the flame.
Inasmuch as wide tubes must be used, the problem of evaporating water as fast as possible is
equivalent to getting heat into the current (water and steam circulating through the coils) as fast as
possible from without. If, therefore, t is the mean temperature of the fluids within the coils, and T
the effective temperature surrounding the tube, then the rate at which heat will flow into the tubes
is proportional to T−t. Now t the temperature of the steam is nearly constant (100°–150°) whereas
T the effective flame temperature may vary from 800° to, say, 1600°. It is for this reason that the
heat sponged up by the boiler depends almost directly on the flame temperature.
“What conditions, therefore, will make the flame effectively hot?
“(1) The coils must obviously be brought as nearly into the flame as feasible: for this purpose
the cylindrical helix is better than any other form. But
“(2) The turns and coils must not be so crowded together as to chill the flame into imperfect
combustion in various parts of its extent. Hence the loose form of winding. Again
“(3) There must be oxygen enough to allow complete combustion, and
“(4) The flame itself must be hot and the radiation checked by good jacketing.
“To take up the last points: the effective heat of the flame depends not only on the combustion
heat of the fuel used; it depends also, among other things, on the speed with which this combustion
takes place. A flame burning from a low pressure of alcohol gas will be at low temperature as
compared with a flame burning from high pressures of the gas. If the flame be burnt from a
Bunsen burner in the usual way it is an interesting question to know how flame temperature will
vary with gas pressure. At present we know it merely in steam pressures incidently produced in a
given engine (No. 4) as for instance:
Flame pressure, 10 lbs., 20 lbs., 30 lbs.
Steam pressure, 40 lbs., 80 lbs., 120 lbs.
in the running engine.
[p073]
“Unfortunately there is a limit set to this process of increasing the steam supply, quite aside
from conditions inherent in the method. This is due to the fact that a certain speed of efflux cannot
be exceeded without putting the flame out. Suppose, for instance, in Fig. 12, that a gas generated
from a liquid is ignited at the end of the Bunsen burner F ; then if the velocity of efflux of mixed
gas and air in the direction AB from the mouth of F exceeds the velocity of combustion in the
direction BA, the flame will obviously be carried away from the mouth of the tube and dissipated.
This state of things is actually realized at pressures exceeding about 15 lbs., depending on the
degree of mixture of the combustible gases used, and therefore on apparently haphazard conditions
connected with the jet, the air holes, the air supply, etc.
Page 129
FIG. 12.
FIG. 13.
“If, however, the velocity of the jet at the point of efflux be checked by an obstruction like a
cylinder C, Fig. 13, placed co-axially with the burner tube F, the speed of combustion will no
longer be exceeded (supposing C properly chosen) and flames will then burn from high-pressure
gas. In this way flames were maintained generated from alcohol gas at even 40 lbs. and above.
FIG. 14.
“The gas escaping from the Bunsen burner is never sufficiently aërated to burn completely.
Otherwise there would (in general) be explosions in the tube F. A part of this air is supplied at the
mouth of the boiler B, Fig. 14, and the amount available here will depend on the velocity of the jet
F. Hence it does not follow that a high-pressure burner like that in Fig. 11 will supply a
proportionate amount of heat, since its jet suction is not intense and the combustion within the
boiler is incomplete. This difficulty may be remedied by placing [p074] air holes in the jacket of
the boiler, provided the boiler be wrapped loosely enough not to chill the flame below ignition. It
is with reference to this effect that the boilers, Fig. 11, were wound. A number of rifts aaa, Fig. 15,
are then left in the jacket through which air may enter in virtue of the burner flame acting as a jet
at the mouth of the boiler.
FIG. 13.
“If, however, the velocity of the jet at the point of efflux be checked by an obstruction like a
cylinder C, Fig. 13, placed co-axially with the burner tube F, the speed of combustion will no
longer be exceeded (supposing C properly chosen) and flames will then burn from high-pressure
gas. In this way flames were maintained generated from alcohol gas at even 40 lbs. and above.
FIG. 14.
“The gas escaping from the Bunsen burner is never sufficiently aërated to burn completely.
Otherwise there would (in general) be explosions in the tube F. A part of this air is supplied at the
mouth of the boiler B, Fig. 14, and the amount available here will depend on the velocity of the jet
F. Hence it does not follow that a high-pressure burner like that in Fig. 11 will supply a
proportionate amount of heat, since its jet suction is not intense and the combustion within the
boiler is incomplete. This difficulty may be remedied by placing [p074] air holes in the jacket of
the boiler, provided the boiler be wrapped loosely enough not to chill the flame below ignition. It
is with reference to this effect that the boilers, Fig. 11, were wound. A number of rifts aaa, Fig. 15,
are then left in the jacket through which air may enter in virtue of the burner flame acting as a jet
at the mouth of the boiler.
Page 130
“When so constructed the flame at first enters the inner coil only; but after a little while it
suddenly spreads out throughout the whole interior space and envelops the coils. This sudden
expansion is due, probably, to the assumption of the spheroidal state by the water within the coils,
the current now flaring on an enveloping cushion of steam. The pump must work well, for
deficient water means a hot tube and deficient steam, or eventually a rupture of the tube.
“Thus far the dependence for draft has been on the burner jet and the suction of the smoke-stack
in virtue of the inertia of the moving gases. But even with this ventilated boiler, this method is
limited to certain dimensions of the boiler. Thus a boiler 80 cm. long yielded about the same
quantity of steam as a boiler half as long and otherwise similar. Only the initial parts of the boiler
are, therefore, relatively efficient, and the reason of this seems to be that, apart from shape, etc.,
the flame as a heat-producing agent is practically defunct, when a certain amount of heat has been
taken out of it: in other words, even with fair ventilation the flame is eventually chilled off by the
voluminous products of combustion continually accumulating in the boiler. The same choking
action accompanies the presence of unburnt gases. If, for instance, the flame be burnt in the air, it
is slender and much smaller in volume than in the boiler. The flame is also of small volume and
burns completely in a wide boiler, but the steam is always deficient, because of the distance
1
between flame and coils (see above). With the above apparatus about 2 lb. of dry steam per minute
per square foot of heating surface was attained.
FIG. 15.
“This introduces the final condition for rapid steam generation. There must be artificial suction
at the smoke-stack. By passing the exhaust steam in the form of a central jet through the smoke-
stack the yield of steam was increased 20 to 30 per cent. In fact as the supply of gas from the
burner is given, the artificial suction in question means more air in the boiler for the same amount
of gas and it means also a more rapid removal of the exhaust gases. The experiments with steam
suction are yet to be completed, and with them the boiler question is to be finally laid at rest. The
chief points at issue are these:
“1. Seeing that the jet suction increases with the length of the smoke-stack, up to a certain length
at least, how long and how wide must the efficient smoke-stack be made? Thus a smoke-stack 10
cm. long is all but useless. Good results are obtained when the stack measures 30 cm. in length
beyond the end of the steam jet. [p075]
“2. What is the relative efficiency of the initial and final halves of the length of the boiler? This
will show in how far it is useful to increase the length of the boiler for a given burner and steam
jet. It will also show what advantage is to be gained from triplicate boilers with three burners, as
compared with duplicate boilers with two burners, or single boilers with one burner, when the
same weight of tubing is used throughout.
“3. What is the effect of pressure on the aeolipile tank, or in how far does the steam generated
depend on what may be called the pressure of the flame? This is also an important point which
suddenly spreads out throughout the whole interior space and envelops the coils. This sudden
expansion is due, probably, to the assumption of the spheroidal state by the water within the coils,
the current now flaring on an enveloping cushion of steam. The pump must work well, for
deficient water means a hot tube and deficient steam, or eventually a rupture of the tube.
“Thus far the dependence for draft has been on the burner jet and the suction of the smoke-stack
in virtue of the inertia of the moving gases. But even with this ventilated boiler, this method is
limited to certain dimensions of the boiler. Thus a boiler 80 cm. long yielded about the same
quantity of steam as a boiler half as long and otherwise similar. Only the initial parts of the boiler
are, therefore, relatively efficient, and the reason of this seems to be that, apart from shape, etc.,
the flame as a heat-producing agent is practically defunct, when a certain amount of heat has been
taken out of it: in other words, even with fair ventilation the flame is eventually chilled off by the
voluminous products of combustion continually accumulating in the boiler. The same choking
action accompanies the presence of unburnt gases. If, for instance, the flame be burnt in the air, it
is slender and much smaller in volume than in the boiler. The flame is also of small volume and
burns completely in a wide boiler, but the steam is always deficient, because of the distance
1
between flame and coils (see above). With the above apparatus about 2 lb. of dry steam per minute
per square foot of heating surface was attained.
FIG. 15.
“This introduces the final condition for rapid steam generation. There must be artificial suction
at the smoke-stack. By passing the exhaust steam in the form of a central jet through the smoke-
stack the yield of steam was increased 20 to 30 per cent. In fact as the supply of gas from the
burner is given, the artificial suction in question means more air in the boiler for the same amount
of gas and it means also a more rapid removal of the exhaust gases. The experiments with steam
suction are yet to be completed, and with them the boiler question is to be finally laid at rest. The
chief points at issue are these:
“1. Seeing that the jet suction increases with the length of the smoke-stack, up to a certain length
at least, how long and how wide must the efficient smoke-stack be made? Thus a smoke-stack 10
cm. long is all but useless. Good results are obtained when the stack measures 30 cm. in length
beyond the end of the steam jet. [p075]
“2. What is the relative efficiency of the initial and final halves of the length of the boiler? This
will show in how far it is useful to increase the length of the boiler for a given burner and steam
jet. It will also show what advantage is to be gained from triplicate boilers with three burners, as
compared with duplicate boilers with two burners, or single boilers with one burner, when the
same weight of tubing is used throughout.
“3. What is the effect of pressure on the aeolipile tank, or in how far does the steam generated
depend on what may be called the pressure of the flame? This is also an important point which
Page 131
remains for quantitative solution. It can be approached in two ways: either by finding the steam
evaporated in terms of the tank pressure, or by finding the temperature of the flame pyrometrically.
“4. What speed of water circulation best conduces to steam generation? A good pump is now
installed by which the circulation can be varied. If water can be put into the boiler just fast enough
to come out dry steam at the other end, the efficiency ought to be a maximum, but it does not
follow that it will be so, for one can imagine a wet circulation sponging up more heat than one
which is just dry at the end.”
189 5
During January and February, 1895, the experiments with boilers and
burners were continued and even better and more uniform results than those
given above were obtained. The boilers of Aerodrome No. 5 were finally
brought to such a state of efficiency, that under favorable conditions a lift of
nearly sixty per cent of the flying weight was secured. This was much more
than was required for flight, but it was decided to postpone the trials until
No. 4 could also be made ready for a test and the frame of No. 5 could itself
be strengthened in many weak places.
Upon examining No. 4, which had been put aside since the trials in
December, it was found to have rusted so badly throughout and to be so
unfit in every way for trial, that a complete reconstruction of the whole
would be necessary. So many advantages had been gained in No. 5 by the
double midrod type of construction that it was decided to rebuild No. 4 on a
modification of the same plan, as shown in Plate 11, retaining, however, the
same engines which had been used before.
In this a very guarded return was made to the type which had proved so
unsatisfactory in No. 0, that is, making the hull support rods at the front and
rear for attaching the wings and tail. In this case, however, the hull was
constructed very rigidly, and the tubes at the front and rear were firmly
attached and braced so that they could withstand a considerable strain
without undue distortion. The work on this frame was completed in March,
but the other parts were not in entirely efficient condition even in May,
when the aerodromes were taken to Quantico for trial. Moreover, it was
found that the weight of this aerodrome had increased far beyond the
original estimates. [p076]
evaporated in terms of the tank pressure, or by finding the temperature of the flame pyrometrically.
“4. What speed of water circulation best conduces to steam generation? A good pump is now
installed by which the circulation can be varied. If water can be put into the boiler just fast enough
to come out dry steam at the other end, the efficiency ought to be a maximum, but it does not
follow that it will be so, for one can imagine a wet circulation sponging up more heat than one
which is just dry at the end.”
189 5
During January and February, 1895, the experiments with boilers and
burners were continued and even better and more uniform results than those
given above were obtained. The boilers of Aerodrome No. 5 were finally
brought to such a state of efficiency, that under favorable conditions a lift of
nearly sixty per cent of the flying weight was secured. This was much more
than was required for flight, but it was decided to postpone the trials until
No. 4 could also be made ready for a test and the frame of No. 5 could itself
be strengthened in many weak places.
Upon examining No. 4, which had been put aside since the trials in
December, it was found to have rusted so badly throughout and to be so
unfit in every way for trial, that a complete reconstruction of the whole
would be necessary. So many advantages had been gained in No. 5 by the
double midrod type of construction that it was decided to rebuild No. 4 on a
modification of the same plan, as shown in Plate 11, retaining, however, the
same engines which had been used before.
In this a very guarded return was made to the type which had proved so
unsatisfactory in No. 0, that is, making the hull support rods at the front and
rear for attaching the wings and tail. In this case, however, the hull was
constructed very rigidly, and the tubes at the front and rear were firmly
attached and braced so that they could withstand a considerable strain
without undue distortion. The work on this frame was completed in March,
but the other parts were not in entirely efficient condition even in May,
when the aerodromes were taken to Quantico for trial. Moreover, it was
found that the weight of this aerodrome had increased far beyond the
original estimates. [p076]
Page 132
In view of the disasters from trials in the field, due to inability to obtain
automatic equilibrium in flight and to the flexure of the large wings rather
than to defects of the engines, the conditions at this time, after three years
of failure, seemed so nearly hopeless, that without abandoning the work on
these steam aerodromes, I again had recourse to the early plan of
constructing smaller models driven by India rubber, in which the small
wings employed could be made of the requisite stiffness. Instead of
employing twisted rubber, however, the defects of which had been amply
proved in previous trials, these new constructions were meant to employ
rubber directly stretched and pulling. In this condition the rubber exercises
nearly six times the power in proportion to weight that it does when twisted,
but on the other hand it requires a very strong frame and subordinate parts.
I spent an inordinate amount of time and labor during this year in
attempting to employ this latter form of construction and finally got a few
useful results from it, but none in proportion to the labor expended.
During March, Aerodrome No. 5, the frame of which had proved on test
to be radically weak, was completely refinished except for the wings. The
propellers had hitherto been made of wood, but in May, I commenced a new
construction of steel, wood and cloth, on a plan giving a figure which,
though not rigorously helicoidal, was practically near enough to the
theoretical form and was also both lighter and more elastic than the wooden
construction.
On May 8 and June 7 Aerodrome No. 5 was again tried at Quantico, and
although the tests were unsuccessful, in that the aerodrome failed to fly,
partly because of the fact that so much time was spent in raising steam that
practically the entire supply of fuel and water was exhausted before the
aerodrome was actually launched, yet it had come so much nearer flying
than any machine had previously done, that it was felt that if either the
power could be increased or the weight decreased even a slight amount, the
aerodrome would probably fly. In view of the great care that had been
exercised in keeping down the weight, it seemed almost hopeless to attempt
to reduce it, and it also seemed equally hopeless to attempt to get more
power without increasing the weight. However, something had to be done
automatic equilibrium in flight and to the flexure of the large wings rather
than to defects of the engines, the conditions at this time, after three years
of failure, seemed so nearly hopeless, that without abandoning the work on
these steam aerodromes, I again had recourse to the early plan of
constructing smaller models driven by India rubber, in which the small
wings employed could be made of the requisite stiffness. Instead of
employing twisted rubber, however, the defects of which had been amply
proved in previous trials, these new constructions were meant to employ
rubber directly stretched and pulling. In this condition the rubber exercises
nearly six times the power in proportion to weight that it does when twisted,
but on the other hand it requires a very strong frame and subordinate parts.
I spent an inordinate amount of time and labor during this year in
attempting to employ this latter form of construction and finally got a few
useful results from it, but none in proportion to the labor expended.
During March, Aerodrome No. 5, the frame of which had proved on test
to be radically weak, was completely refinished except for the wings. The
propellers had hitherto been made of wood, but in May, I commenced a new
construction of steel, wood and cloth, on a plan giving a figure which,
though not rigorously helicoidal, was practically near enough to the
theoretical form and was also both lighter and more elastic than the wooden
construction.
On May 8 and June 7 Aerodrome No. 5 was again tried at Quantico, and
although the tests were unsuccessful, in that the aerodrome failed to fly,
partly because of the fact that so much time was spent in raising steam that
practically the entire supply of fuel and water was exhausted before the
aerodrome was actually launched, yet it had come so much nearer flying
than any machine had previously done, that it was felt that if either the
power could be increased or the weight decreased even a slight amount, the
aerodrome would probably fly. In view of the great care that had been
exercised in keeping down the weight, it seemed almost hopeless to attempt
to reduce it, and it also seemed equally hopeless to attempt to get more
power without increasing the weight. However, something had to be done
Page 133
to increase the ratio of power to weight, and as it was seen that this would
involve extensive changes in No. 5, it was decided to entirely rebuild No. 4
with this idea in view, though it was evident that it involved a plan of
construction even lighter than the dangerously light plan on which No. 4
had already been constructed.
During Mr. Langley’s absence in Europe in the summer, Aerodrome No.
4 was entirely reconstructed and made to embody many new characteristics,
the changes introduced being so radical that this model was henceforth
designated as “New No. 4.” The new characteristics of this model were its
unprecedentedly [p077] light frame and the elevation of the transverse frame
12 centimeters above the midrod, whereby the position of the line of thrust
was raised so that it was 20 centimetres from the center of pressure, which
from theory seemed to be very nearly its correct position. The total flying
weight was but 6400 grammes (14 pounds), with a total supporting surface
of fifty-four square feet, equivalent to very nearly four square feet per
pound. It was hoped that with this extremely light construction the “dead
lift” would amount to a large percentage of the flying weight, and as much
as sixty per cent was actually lifted on the pendulum. As, however, the
aerodrome approached completion it became more and more evident that
the construction was hopelessly fragile, the frame being scarcely able to
support itself in the shop. By November this conclusion became certain, and
this aerodrome (New No. 4) was never put to an actual test in the field. The
very expensive set of wings covered with gold beater’s skin, which were
also constructed at this time for this model, proved so weak under test that
they were entirely abandoned.
When Mr. Langley returned to Washington in the fall, many important
points, which had been under special consideration during the past year,
particularly those relating to the disposition of sustaining surfaces, and the
provision of automatic equilibrium, were still not definitely determined. It
was not yet decided whether two sets of wings of equal area should be used
for the aerodrome, or what the efficiency per unit of area of the following
surfaces was in comparison with the leading surfaces. To aid in determining
these and other important points concerning the relative position of the
involve extensive changes in No. 5, it was decided to entirely rebuild No. 4
with this idea in view, though it was evident that it involved a plan of
construction even lighter than the dangerously light plan on which No. 4
had already been constructed.
During Mr. Langley’s absence in Europe in the summer, Aerodrome No.
4 was entirely reconstructed and made to embody many new characteristics,
the changes introduced being so radical that this model was henceforth
designated as “New No. 4.” The new characteristics of this model were its
unprecedentedly [p077] light frame and the elevation of the transverse frame
12 centimeters above the midrod, whereby the position of the line of thrust
was raised so that it was 20 centimetres from the center of pressure, which
from theory seemed to be very nearly its correct position. The total flying
weight was but 6400 grammes (14 pounds), with a total supporting surface
of fifty-four square feet, equivalent to very nearly four square feet per
pound. It was hoped that with this extremely light construction the “dead
lift” would amount to a large percentage of the flying weight, and as much
as sixty per cent was actually lifted on the pendulum. As, however, the
aerodrome approached completion it became more and more evident that
the construction was hopelessly fragile, the frame being scarcely able to
support itself in the shop. By November this conclusion became certain, and
this aerodrome (New No. 4) was never put to an actual test in the field. The
very expensive set of wings covered with gold beater’s skin, which were
also constructed at this time for this model, proved so weak under test that
they were entirely abandoned.
When Mr. Langley returned to Washington in the fall, many important
points, which had been under special consideration during the past year,
particularly those relating to the disposition of sustaining surfaces, and the
provision of automatic equilibrium, were still not definitely determined. It
was not yet decided whether two sets of wings of equal area should be used
for the aerodrome, or what the efficiency per unit of area of the following
surfaces was in comparison with the leading surfaces. To aid in determining
these and other important points concerning the relative position of the
Page 134
center of gravity and the center of pressure in the horizontal planes, he had
several small gliding models made, which could be used with either one or
two pairs of wings, and afforded an opportunity for testing and comparing
several types of curved surfaces.
These models were built so that the center of gravity could be adjusted to
any desired point, and had in addition, as a means of assisting in preserving
equilibrium, a small tail-rudder, shaped somewhat like a child’s dart, which
was intended to support no part of the weight.
The tests with these models were very satisfactory and aided greatly in
the final development of what is known as the “Langley type.” Indeed, in
the single month of November all the points, which had hitherto been more
or less indefinite, were finally decided upon, and the tests of the following
spring proved these decisions correct.
Two sets of wings of equal area were hereafter provided for every
aerodrome, which not only greatly increased the stability, but also overcame
the difficulty hitherto experienced in bringing the CP over the CG. The tail-
rudder, formed of planes intersecting at right angles, was adopted as the
means of control. In use on the aerodromes it was set at a negative angle,
and given a certain [p078] degree of elasticity, which was at first provided in
the frame of the rudder, but was later given by a flat wooden spring, by
which it was attached to the aerodrome. The tail in this form now became
the sole means of controlling the equilibrium, and the results obtained with
it were so very satisfactory that no further attention was given either to the
gyroscopic control built during the previous summer, or to any of the
electrical forms of control constructed prior to that time, all of which
involved more or less delicate apparatus.
The definite form into which these ideas crystallized is perhaps best
exemplified in the letter of instructions issued by Mr. Langley on November
30, 1895 to the men employed on the work. The text of this letter is given in
the Appendix, and the forms referred to in it for recording the weights and
adjustments of the aerodromes are those used in the data sheets after this
time.
several small gliding models made, which could be used with either one or
two pairs of wings, and afforded an opportunity for testing and comparing
several types of curved surfaces.
These models were built so that the center of gravity could be adjusted to
any desired point, and had in addition, as a means of assisting in preserving
equilibrium, a small tail-rudder, shaped somewhat like a child’s dart, which
was intended to support no part of the weight.
The tests with these models were very satisfactory and aided greatly in
the final development of what is known as the “Langley type.” Indeed, in
the single month of November all the points, which had hitherto been more
or less indefinite, were finally decided upon, and the tests of the following
spring proved these decisions correct.
Two sets of wings of equal area were hereafter provided for every
aerodrome, which not only greatly increased the stability, but also overcame
the difficulty hitherto experienced in bringing the CP over the CG. The tail-
rudder, formed of planes intersecting at right angles, was adopted as the
means of control. In use on the aerodromes it was set at a negative angle,
and given a certain [p078] degree of elasticity, which was at first provided in
the frame of the rudder, but was later given by a flat wooden spring, by
which it was attached to the aerodrome. The tail in this form now became
the sole means of controlling the equilibrium, and the results obtained with
it were so very satisfactory that no further attention was given either to the
gyroscopic control built during the previous summer, or to any of the
electrical forms of control constructed prior to that time, all of which
involved more or less delicate apparatus.
The definite form into which these ideas crystallized is perhaps best
exemplified in the letter of instructions issued by Mr. Langley on November
30, 1895 to the men employed on the work. The text of this letter is given in
the Appendix, and the forms referred to in it for recording the weights and
adjustments of the aerodromes are those used in the data sheets after this
time.
Page 135
In October work was resumed on Aerodrome No. 5, on which nothing
had been done since its test on June 7. The reconstruction of “Old No. 4”
into “New No. 4” which had occupied the entire summer, and the final
result of which was the production of a machine so radically weak as to be
useless, had been so discouraging that it seemed vain to attempt in any way
to decrease the weight of No. 5. The addition of the rear wings in place of
the tail had, however, so greatly increased the supporting surface that it
seemed possible that No. 5 might now be able to fly with no greater engine
power than it had on June 7. Some weak places in its frame were, therefore,
strengthened and the midrod at the front was raised five centimetres in
order to raise the center of pressure farther above the center of gravity and
give the front wings a greater range of adjustment. Some slight changes
were also made in the gearing which drove the pump, so as to make it work
faster, and new burners, boilers and a gasoline tank were constructed during
November. Later the midrod, which had formerly consisted of two separate
pieces attached at the front and rear respectively of the main frame, was
made continuous, and in order to avoid passing it through the smoke-stack,
the stack was made to fork at this point. These changes are clearly shown in
Plates 14 and 15, which are photographs taken on December 3. This plan
was, however, soon changed so that the midrod passed through the smoke-
stack and was rigidly attached to the frame at several points, and a new
pump and new boilers were substituted for those which had been worn out.
Aside from these changes, which although small, added very materially to
the general strength of the frame, no important changes were made in No. 5
prior to its remarkable flight of May 6, 1896.
had been done since its test on June 7. The reconstruction of “Old No. 4”
into “New No. 4” which had occupied the entire summer, and the final
result of which was the production of a machine so radically weak as to be
useless, had been so discouraging that it seemed vain to attempt in any way
to decrease the weight of No. 5. The addition of the rear wings in place of
the tail had, however, so greatly increased the supporting surface that it
seemed possible that No. 5 might now be able to fly with no greater engine
power than it had on June 7. Some weak places in its frame were, therefore,
strengthened and the midrod at the front was raised five centimetres in
order to raise the center of pressure farther above the center of gravity and
give the front wings a greater range of adjustment. Some slight changes
were also made in the gearing which drove the pump, so as to make it work
faster, and new burners, boilers and a gasoline tank were constructed during
November. Later the midrod, which had formerly consisted of two separate
pieces attached at the front and rear respectively of the main frame, was
made continuous, and in order to avoid passing it through the smoke-stack,
the stack was made to fork at this point. These changes are clearly shown in
Plates 14 and 15, which are photographs taken on December 3. This plan
was, however, soon changed so that the midrod passed through the smoke-
stack and was rigidly attached to the frame at several points, and a new
pump and new boilers were substituted for those which had been worn out.
Aside from these changes, which although small, added very materially to
the general strength of the frame, no important changes were made in No. 5
prior to its remarkable flight of May 6, 1896.
Page 136
PL. 14. AERODROME NO. 5, DECEMBER 3, 1895. PLAN VIEW.
RUDDER REMOVED ◊
RUDDER REMOVED ◊
Page 137
PL. 15. AERODROME NO. 5, DECEMBER 3, 1895.
SIDE VIEW ◊
SIDE VIEW ◊
Page 138
While these changes were being made in No. 5, similar ones were also
being carried out in New No. 4, and the addition of the rear wings to No. 4,
together with other slight changes, made it such a distinctively different
machine from what it had been, that it was now designated as No. 6. After
making extensive [p079] repairs to the extremely light frame of No. 6
(formerly New No. 4) it was thought to be in suitable condition for flight
and was accordingly boxed preparatory to sending it to Quantico.
The year, therefore, closed with No. 6 apparently in condition for test, but
it was decided not to take it to Quantico until No. 5, which was still
undergoing repairs, could also be got ready.
189 6
A few days after the beginning of the new year, while the repairs on No.
5 were being completed, it was decided that the frame of No. 6 which had
been boxed ready to be carried into the field for trial, was so weak that
before putting it to an actual test in flight it would be best to make some
tests on the strength of its frame. While testing the frame for torsional
strength, it broke under the moderate test of a weight of 500 grammes
placed at the tips of the wings, the angle of deflection just prior to its
breaking being 35°, while the frame of Old No. 4 in March, 1895, had
shown a deflection of only 10.5° under a similar test. This breaking of the
frame showed very plainly that the worst fears in regard to it had been
realized and that by some means or other the frame must be strengthened.
This was finally accomplished by making the midrod continuous through
the smoke-stack as had already been done in No. 5, and at the same time an
additional improvement was made in the means of attaching the Pénaud
tail, whereby it was lowered in order to give it a greater clearance in passing
under the launching car in actual test. Later the boilers proved defective and
new ones were substituted, but except for some minute details no further
changes were made in Aerodrome No. 6 prior to its test in May.
On May 6, No. 6 was unsuccessfully tried at Quantico just prior to the
very successful test of No. 5. In this test no serious damage was done to the
frame, but before going to Europe in the summer, Mr. Langley ordered that
being carried out in New No. 4, and the addition of the rear wings to No. 4,
together with other slight changes, made it such a distinctively different
machine from what it had been, that it was now designated as No. 6. After
making extensive [p079] repairs to the extremely light frame of No. 6
(formerly New No. 4) it was thought to be in suitable condition for flight
and was accordingly boxed preparatory to sending it to Quantico.
The year, therefore, closed with No. 6 apparently in condition for test, but
it was decided not to take it to Quantico until No. 5, which was still
undergoing repairs, could also be got ready.
189 6
A few days after the beginning of the new year, while the repairs on No.
5 were being completed, it was decided that the frame of No. 6 which had
been boxed ready to be carried into the field for trial, was so weak that
before putting it to an actual test in flight it would be best to make some
tests on the strength of its frame. While testing the frame for torsional
strength, it broke under the moderate test of a weight of 500 grammes
placed at the tips of the wings, the angle of deflection just prior to its
breaking being 35°, while the frame of Old No. 4 in March, 1895, had
shown a deflection of only 10.5° under a similar test. This breaking of the
frame showed very plainly that the worst fears in regard to it had been
realized and that by some means or other the frame must be strengthened.
This was finally accomplished by making the midrod continuous through
the smoke-stack as had already been done in No. 5, and at the same time an
additional improvement was made in the means of attaching the Pénaud
tail, whereby it was lowered in order to give it a greater clearance in passing
under the launching car in actual test. Later the boilers proved defective and
new ones were substituted, but except for some minute details no further
changes were made in Aerodrome No. 6 prior to its test in May.
On May 6, No. 6 was unsuccessfully tried at Quantico just prior to the
very successful test of No. 5. In this test no serious damage was done to the
frame, but before going to Europe in the summer, Mr. Langley ordered that
Page 139
both aerodromes be completely overhauled and put in condition for further
experiments in the fall. In this remodelling practically no changes were
introduced in the frame of either No. 5 or No. 6, but the engines of No. 6
were refitted and a new boiler was substituted, which, with slight
improvements in the burner, resulted in a somewhat increased power in the
engines.
A complete description, giving all essential details of both Aerodromes
Nos. 5 and 6, will be found in Chapter X ◊.
experiments in the fall. In this remodelling practically no changes were
introduced in the frame of either No. 5 or No. 6, but the engines of No. 6
were refitted and a new boiler was substituted, which, with slight
improvements in the burner, resulted in a somewhat increased power in the
engines.
A complete description, giving all essential details of both Aerodromes
Nos. 5 and 6, will be found in Chapter X ◊.
Page 140
[p080] ◊
CHAPTER VIII
HISTORY OF CONSTRUCTION OF SUSTAINING AND
GUIDING SURFACES OF AERODROMES 4, 5 AND 6
I NTRODUCTION
In some early experiments in 1887 with the small models without motor
power, which have not been particularly described, two pairs of wings, in
the same plane, were employed for reasons connected with stability.
Afterward, in many of the rubber-driven motor models, which have been
described in Chapter II ◊, two large front wings were employed and the
following pair were diminished into what may properly be called a tail. This
plan was a retrogression in design, and it was pursued by the writer with a
pertinacity which was not justified by the results obtained, being used even
on the early rubber-driven models.
In this construction, it will be observed that the flat tail was in fact not
only a guiding but a sustaining surface, since it bore its own share of the
weight. It was not until a much later date (November, 1895) that the writer
returned to his earlier construction of two pairs of wings in the same plane
bearing the whole weight of the aerodrome, to which was now added a flat
tail, whose function was not to support, but wholly to guide. This was
developed into the final construction by the addition of a vertical rudder or
rudders.
The present chapter is not concerned with the history of the earlier
attempts with small models, or of those numerous constructions of
sustaining surfaces which were never put to actual trial; nor does it give any
description of the experiments which were made in placing one set of
surfaces over the other, according to a method suggested in “Experiments in
Aerodynamics.”27
The experiments in “Aerodynamics,” and the theoretical considerations
given in Chapter V ◊ on sustaining surfaces, would never alone have led to
the construction which was finally reached, which was largely due to the
CHAPTER VIII
HISTORY OF CONSTRUCTION OF SUSTAINING AND
GUIDING SURFACES OF AERODROMES 4, 5 AND 6
I NTRODUCTION
In some early experiments in 1887 with the small models without motor
power, which have not been particularly described, two pairs of wings, in
the same plane, were employed for reasons connected with stability.
Afterward, in many of the rubber-driven motor models, which have been
described in Chapter II ◊, two large front wings were employed and the
following pair were diminished into what may properly be called a tail. This
plan was a retrogression in design, and it was pursued by the writer with a
pertinacity which was not justified by the results obtained, being used even
on the early rubber-driven models.
In this construction, it will be observed that the flat tail was in fact not
only a guiding but a sustaining surface, since it bore its own share of the
weight. It was not until a much later date (November, 1895) that the writer
returned to his earlier construction of two pairs of wings in the same plane
bearing the whole weight of the aerodrome, to which was now added a flat
tail, whose function was not to support, but wholly to guide. This was
developed into the final construction by the addition of a vertical rudder or
rudders.
The present chapter is not concerned with the history of the earlier
attempts with small models, or of those numerous constructions of
sustaining surfaces which were never put to actual trial; nor does it give any
description of the experiments which were made in placing one set of
surfaces over the other, according to a method suggested in “Experiments in
Aerodynamics.”27
The experiments in “Aerodynamics,” and the theoretical considerations
given in Chapter V ◊ on sustaining surfaces, would never alone have led to
the construction which was finally reached, which was largely due to the
Page 141
hard lessons taught by incessant accident and failure in the field. The
present chapter, therefore, should be read in connection not only with the
pages of “Aerodynamics,” but with Chapters V and IX ◊ of this book.
present chapter, therefore, should be read in connection not only with the
pages of “Aerodynamics,” but with Chapters V and IX ◊ of this book.
Page 142
PL. 16. EARLY TYPES OF WINGS AND SYSTEMS OF GUYING ◊
Page 143
It is to be remembered that, while the center of gravity of the aerodrome
could be determined readily and exactly, the center of pressure could be
determined only approximately in advance of trial in actual flight. The
positions [p081] of the supporting surfaces given in this chapter are, then,
approximations made from rules for “balancing,” i. e., for obtaining
equilibrium in actual flight, rules which are in fact tentative, since they are
founded on a priori considerations with partial correction from the
empirical knowledge gained by previous field trials. For these rules see
Chapter VI ◊.
189 3
With reference to the supporting and guiding surfaces of Aerodromes
Nos. 4, 5, and 6, Aerodrome No. 4, in its earliest condition mentioned in the
preceding chapter, was taken into the field, but never brought to trial in the
air. It is sufficient to say that in the largest of the three sets of wings
constructed, each wing was 17 × 51 inches, and therefore contained about
six square feet, so that with the tail (which was at this time a supporting
surface), whose area was one-half that of the two wings, the total
supporting surface was 18 square feet, or since the flying weight was 9.1
pounds, the proportion of surface to weight was somewhat less than 2
square feet to the pound. The wings were at this time ribless, it being
expected that the silk cover which was purposely left loose would take its
curve from the air filling it, which subsequent experience has shown would
have led to certain disaster if the aerodrome had been launched. It may be
added that there was a vertical rudder of what is now seen to have been a
wholly inadequate size. These remarks may be applied with little
modification to the attempted flight with No. 4 on May 25, except that the
vertical rudder had been made larger, but was still much too small.
189 4
From the account of the field trials to be given in Chapter IX ◊, it will be
seen that in numerous attempts at flight prior to October 6, 1894, the cause
of failure can in every instance be traced to imperfections more
could be determined readily and exactly, the center of pressure could be
determined only approximately in advance of trial in actual flight. The
positions [p081] of the supporting surfaces given in this chapter are, then,
approximations made from rules for “balancing,” i. e., for obtaining
equilibrium in actual flight, rules which are in fact tentative, since they are
founded on a priori considerations with partial correction from the
empirical knowledge gained by previous field trials. For these rules see
Chapter VI ◊.
189 3
With reference to the supporting and guiding surfaces of Aerodromes
Nos. 4, 5, and 6, Aerodrome No. 4, in its earliest condition mentioned in the
preceding chapter, was taken into the field, but never brought to trial in the
air. It is sufficient to say that in the largest of the three sets of wings
constructed, each wing was 17 × 51 inches, and therefore contained about
six square feet, so that with the tail (which was at this time a supporting
surface), whose area was one-half that of the two wings, the total
supporting surface was 18 square feet, or since the flying weight was 9.1
pounds, the proportion of surface to weight was somewhat less than 2
square feet to the pound. The wings were at this time ribless, it being
expected that the silk cover which was purposely left loose would take its
curve from the air filling it, which subsequent experience has shown would
have led to certain disaster if the aerodrome had been launched. It may be
added that there was a vertical rudder of what is now seen to have been a
wholly inadequate size. These remarks may be applied with little
modification to the attempted flight with No. 4 on May 25, except that the
vertical rudder had been made larger, but was still much too small.
189 4
From the account of the field trials to be given in Chapter IX ◊, it will be
seen that in numerous attempts at flight prior to October 6, 1894, the cause
of failure can in every instance be traced to imperfections more
Page 144
fundamental than those of the sustaining surfaces, either the launching
device or some other part failing to work satisfactorily. I therefore
commence a description of the sustaining surfaces with those of Nos. 4 and
5 as used on that day.
The construction of the wings of No. 4 and No. 5, which were nearly
identical, is shown in Fig. A Plate 16. A rod of hickory, tapering from 12 inch
in diameter at the larger end to 14 inch at the smaller, was steamed and bent,
as shown in the drawing, to form the main front rib of the wing. This was
firmly clamped to the midrod, and to the rib in turn were attached a number
of cross-ribs of hickory, slightly curved, the inner one of which was
fastened to the hull at its inner extremity, while the whole was covered with
silk. The length of each wing was 162 cm. (63.75 inches), and the width 54
cm. (21.25 inches). The tail was plane and equal in area to one of the wings,
so that the joint area of the wings and tail was 2.62 square metres (28.2 sq.
ft.). [p082]
Each wing was attached to the midrod by a single clamp, different forms
of which are shown at F, G, H, I (Fig. 16). The clamp consisted of two short
split tubes, into which the main front ribs were securely clamped by means
of screws. They were set at an angle and united to a grooved frame, by
which the wings could be readily attached to a second piece clamped about
the midrod. The tail clamp, like the wing clamp, was composed of two
pieces, sliding one upon the other, but as the tail formed a single surface,
one part was permanently attached to it. Clamps F, G were fitted to
aerodrome No. 4, and H, I to No. 5. The wings were set at a diedral angle of
about 150°, but as they were not guyed in any way, this angle in flight and
under the upward pressure of the air probably became much less. The tail
was plane but ribbed like the wings.
device or some other part failing to work satisfactorily. I therefore
commence a description of the sustaining surfaces with those of Nos. 4 and
5 as used on that day.
The construction of the wings of No. 4 and No. 5, which were nearly
identical, is shown in Fig. A Plate 16. A rod of hickory, tapering from 12 inch
in diameter at the larger end to 14 inch at the smaller, was steamed and bent,
as shown in the drawing, to form the main front rib of the wing. This was
firmly clamped to the midrod, and to the rib in turn were attached a number
of cross-ribs of hickory, slightly curved, the inner one of which was
fastened to the hull at its inner extremity, while the whole was covered with
silk. The length of each wing was 162 cm. (63.75 inches), and the width 54
cm. (21.25 inches). The tail was plane and equal in area to one of the wings,
so that the joint area of the wings and tail was 2.62 square metres (28.2 sq.
ft.). [p082]
Each wing was attached to the midrod by a single clamp, different forms
of which are shown at F, G, H, I (Fig. 16). The clamp consisted of two short
split tubes, into which the main front ribs were securely clamped by means
of screws. They were set at an angle and united to a grooved frame, by
which the wings could be readily attached to a second piece clamped about
the midrod. The tail clamp, like the wing clamp, was composed of two
pieces, sliding one upon the other, but as the tail formed a single surface,
one part was permanently attached to it. Clamps F, G were fitted to
aerodrome No. 4, and H, I to No. 5. The wings were set at a diedral angle of
about 150°, but as they were not guyed in any way, this angle in flight and
under the upward pressure of the air probably became much less. The tail
was plane but ribbed like the wings.
Page 145
FIG. 16. Wing clamps, 1892–1896.
In preparing the machine for flight, the wings and tail of No. 4 were set at
a very small root angle with the midrod, perhaps not exceeding 3°, but
while this angle might be maintained at the firmly held root of the wing, it
was later seen to be probable that the extremity of the wing was flexed by
the upward pressure of the air after launching, though the full extent and
evil effect of this flexure was not recognized at the time. In the
approximative calculations for “balance,” made at this time, the tail was
treated as bearing 13 of the weight of the aerodrome, as it was 13 of the
supporting area, for though it was recognized that its position in the “lee” of
the wings rendered it less efficient, the degree of this diminution of
efficiency was not realized. A vertical rudder 20 cm. × 70 cm. (8 in. × 28
in.), with an area of 0.14 metres (1.5 sq. ft.) was used. [p083]
The particulars of the launch will be found in Chapter IX ◊. In the present
connection, it is sufficient to say that though launched with the requisite
velocity and without accident, it fell into the water at a distance of about 15
metres (49 feet) with the midrod nearly horizontal, the combined effect of
engines and initial impulse having in fact kept it in the air for less than two
In preparing the machine for flight, the wings and tail of No. 4 were set at
a very small root angle with the midrod, perhaps not exceeding 3°, but
while this angle might be maintained at the firmly held root of the wing, it
was later seen to be probable that the extremity of the wing was flexed by
the upward pressure of the air after launching, though the full extent and
evil effect of this flexure was not recognized at the time. In the
approximative calculations for “balance,” made at this time, the tail was
treated as bearing 13 of the weight of the aerodrome, as it was 13 of the
supporting area, for though it was recognized that its position in the “lee” of
the wings rendered it less efficient, the degree of this diminution of
efficiency was not realized. A vertical rudder 20 cm. × 70 cm. (8 in. × 28
in.), with an area of 0.14 metres (1.5 sq. ft.) was used. [p083]
The particulars of the launch will be found in Chapter IX ◊. In the present
connection, it is sufficient to say that though launched with the requisite
velocity and without accident, it fell into the water at a distance of about 15
metres (49 feet) with the midrod nearly horizontal, the combined effect of
engines and initial impulse having in fact kept it in the air for less than two
Page 146
seconds. The true cause of this failure not then being recognized, it was
attributed to the angle of the wings with the midrod having been too small.
The launch of No. 5 followed almost immediately, but taking warning by
the supposed cause of failure of No. 4, its wings were set at a root angle of
20°, and a hurried adjustment was made to secure greater rigidity, the tip
being partly secured against twisting by a light cross-piece, and guyed so
that the wing as a whole was not only at a greater angle, but stiffer than in
the case of No. 4. These changes it was hoped would cause the aerodrome
to advance at a considerable initial angle with the horizontal, and it did so,
for instantly after the launch, as the aerodrome escaped from its bonds into
free air, the inclination of the midrod increased until it stood at about 60°,
when the machine, after struggling a moment to maintain itself, slid
backward into the water (with its engines working at full speed) after
advancing about 12 metres (39 feet), and remaining in the air about 3
seconds.
On the whole, the result of the first actual trial of an aerodrome in the
field was disconcerting, for unless the result was due to the wings being
placed in a position wholly unfavorable to support, there seemed to be no
doubt that either the engine power or the supporting surface was
insufficient. Now this engine power was by computation between three and
four times what was necessary to support the aerodrome in horizontal flight
at an angle of 20°, and after making every allowance for slip, there should
have been still an excess of power for the first flight of No. 4, whereas
actual trial indicated that it was insufficient. But on the other hand, the
experiment with No. 5, which momentarily held its position in the air at an
angle of 60°, seemed to indicate that the engine power was abundant, and
that the failure must be traced to some other cause.
As a result of these experiments it was concluded, “that it is an all-
important thing that the angle of the front wing shall be correct, and that
this cannot be calculated unless it is known how much the tip will turn up
under pressure of the weight.” I felt, then, that I had learned something
from the failures as to the need of greater rigidity of the wings, though how
to obtain this without adding to their weight was a trying problem. It was
attributed to the angle of the wings with the midrod having been too small.
The launch of No. 5 followed almost immediately, but taking warning by
the supposed cause of failure of No. 4, its wings were set at a root angle of
20°, and a hurried adjustment was made to secure greater rigidity, the tip
being partly secured against twisting by a light cross-piece, and guyed so
that the wing as a whole was not only at a greater angle, but stiffer than in
the case of No. 4. These changes it was hoped would cause the aerodrome
to advance at a considerable initial angle with the horizontal, and it did so,
for instantly after the launch, as the aerodrome escaped from its bonds into
free air, the inclination of the midrod increased until it stood at about 60°,
when the machine, after struggling a moment to maintain itself, slid
backward into the water (with its engines working at full speed) after
advancing about 12 metres (39 feet), and remaining in the air about 3
seconds.
On the whole, the result of the first actual trial of an aerodrome in the
field was disconcerting, for unless the result was due to the wings being
placed in a position wholly unfavorable to support, there seemed to be no
doubt that either the engine power or the supporting surface was
insufficient. Now this engine power was by computation between three and
four times what was necessary to support the aerodrome in horizontal flight
at an angle of 20°, and after making every allowance for slip, there should
have been still an excess of power for the first flight of No. 4, whereas
actual trial indicated that it was insufficient. But on the other hand, the
experiment with No. 5, which momentarily held its position in the air at an
angle of 60°, seemed to indicate that the engine power was abundant, and
that the failure must be traced to some other cause.
As a result of these experiments it was concluded, “that it is an all-
important thing that the angle of the front wing shall be correct, and that
this cannot be calculated unless it is known how much the tip will turn up
under pressure of the weight.” I felt, then, that I had learned something
from the failures as to the need of greater rigidity of the wings, though how
to obtain this without adding to their weight was a trying problem. It was
Page 147
thus at an early stage suspected that the evil to be guarded against in wing
construction was the distortion of the form of the wing under pressure,
chiefly by torsion, which is specially hard to provide against without a
construction which is [p084] necessarily heavy. This suspicion was a correct
one, though the full extent of the evil was not yet surmised.
In the light of subsequent experiment it may now be confidently stated
that the trouble was with the wings, which at the moment after launching
were flexed wholly out of the shape which they were designed to have, and
which they retained up to that critical moment.
After returning to Washington, one of the wings was inverted, and a
quantity of sand, equal in weight to the pressure upon the wing in flight,
was added, under which the yielding at the tip amounted to 65°, or
from +20° to −45°, showing that the wings were entirely too weak to
sustain the aerodrome.
In speaking of the efforts to strengthen the wings, it must be constantly
remembered that this could hardly be done in any way which did not
involve increased weight; that is, it could hardly be done at all, since
increased weight was forbidden.
The first attempt at systematic guying was made on October 27. As
shown in Fig. B, Plate 16, two guy-posts extending beneath the midrod
were connected by guy-wires with the outer extremities of the wing, by
means of which it was sought to hold the wing in place and prevent its
extremity from twisting upward, while a third wire connecting with the
bowsprit prevented its moving backward. In addition, two aluminum wires,
stretched across above from wing to wing, kept the lower guys tight.
On October 27, Aerodrome No. 5, equipped with large new wings and
tail, having a combined area of 3.7 square metres (40 sq. ft.), the wings
being each 64 cm. × 192 cm. (25.25 in. × 75.75 in.), turned sharply and
completely round, apparently through some internal current of the main
wind against which it was advancing. Owing to this almost instantaneous
turn, it lost headway and came down. This led to the subsequent
construction and use of a much larger vertical rudder, intended to prevent in
future any such sudden pivoting and consequent loss of momentum. The
construction was the distortion of the form of the wing under pressure,
chiefly by torsion, which is specially hard to provide against without a
construction which is [p084] necessarily heavy. This suspicion was a correct
one, though the full extent of the evil was not yet surmised.
In the light of subsequent experiment it may now be confidently stated
that the trouble was with the wings, which at the moment after launching
were flexed wholly out of the shape which they were designed to have, and
which they retained up to that critical moment.
After returning to Washington, one of the wings was inverted, and a
quantity of sand, equal in weight to the pressure upon the wing in flight,
was added, under which the yielding at the tip amounted to 65°, or
from +20° to −45°, showing that the wings were entirely too weak to
sustain the aerodrome.
In speaking of the efforts to strengthen the wings, it must be constantly
remembered that this could hardly be done in any way which did not
involve increased weight; that is, it could hardly be done at all, since
increased weight was forbidden.
The first attempt at systematic guying was made on October 27. As
shown in Fig. B, Plate 16, two guy-posts extending beneath the midrod
were connected by guy-wires with the outer extremities of the wing, by
means of which it was sought to hold the wing in place and prevent its
extremity from twisting upward, while a third wire connecting with the
bowsprit prevented its moving backward. In addition, two aluminum wires,
stretched across above from wing to wing, kept the lower guys tight.
On October 27, Aerodrome No. 5, equipped with large new wings and
tail, having a combined area of 3.7 square metres (40 sq. ft.), the wings
being each 64 cm. × 192 cm. (25.25 in. × 75.75 in.), turned sharply and
completely round, apparently through some internal current of the main
wind against which it was advancing. Owing to this almost instantaneous
turn, it lost headway and came down. This led to the subsequent
construction and use of a much larger vertical rudder, intended to prevent in
future any such sudden pivoting and consequent loss of momentum. The
Page 148
wings showed a tendency to “pocket”28 and bag, which indicated some
serious fault in their construction.
As a result of these experiments, it was decided on October 29 to attempt
to make the wings stiffer (though their weight was almost prohibitory), by
inserting more cross-pieces, cross-pinning and guying them so as to make
them more rigid as a whole, and less liable to pocket.
At this time an automatic device in the form of a sliding tail was
designed, which it was thought would cause the center of pressure to move
backward when the aerodrome reared, and forward when it plunged
downward, but the device, though afterward constructed, was never brought
to trial in the field.
Aerodrome No. 5, equipped with a new set of wings similar to those used
[p085] on October 27, and guyed as in the previous experiment, was again
launched on November 21, with the results recorded in Chapter IX ◊. The
failure was attributed to the twisting of the wings under pressure to such an
extent that not only was their effective area greatly reduced, but the outer
portions were upturned so as to catch the air upon the upper surfaces, the
result being in part a downward pressure.
On the following day a pair of the wings was inverted and a weight of
sand equal to the air pressure to which they were subjected in flight, was
distributed over their surfaces. Under the action of this, the twisting of the
wing was seen to increase from the root, which was held with comparative
rigidity, up to the tip, where in spite of the cross-ribs it amounted to 45°.
The resistance to torsion lay chiefly in the front rib, which, in addition,
could be bent easily, allowing the surface to become distorted with great
loss of lifting power.
The experiments of 1894 had demonstrated the urgent necessity for
greater rigidity in the sustaining surfaces, which might, as it seemed, be
obtained either by increasing the strength of the framing (which meant
additional weight) or by resorting to some new and untried construction, or
by a proper system of guying. Guying seemingly offered the most feasible
solution of the problem; but although the system of wire guying was
serious fault in their construction.
As a result of these experiments, it was decided on October 29 to attempt
to make the wings stiffer (though their weight was almost prohibitory), by
inserting more cross-pieces, cross-pinning and guying them so as to make
them more rigid as a whole, and less liable to pocket.
At this time an automatic device in the form of a sliding tail was
designed, which it was thought would cause the center of pressure to move
backward when the aerodrome reared, and forward when it plunged
downward, but the device, though afterward constructed, was never brought
to trial in the field.
Aerodrome No. 5, equipped with a new set of wings similar to those used
[p085] on October 27, and guyed as in the previous experiment, was again
launched on November 21, with the results recorded in Chapter IX ◊. The
failure was attributed to the twisting of the wings under pressure to such an
extent that not only was their effective area greatly reduced, but the outer
portions were upturned so as to catch the air upon the upper surfaces, the
result being in part a downward pressure.
On the following day a pair of the wings was inverted and a weight of
sand equal to the air pressure to which they were subjected in flight, was
distributed over their surfaces. Under the action of this, the twisting of the
wing was seen to increase from the root, which was held with comparative
rigidity, up to the tip, where in spite of the cross-ribs it amounted to 45°.
The resistance to torsion lay chiefly in the front rib, which, in addition,
could be bent easily, allowing the surface to become distorted with great
loss of lifting power.
The experiments of 1894 had demonstrated the urgent necessity for
greater rigidity in the sustaining surfaces, which might, as it seemed, be
obtained either by increasing the strength of the framing (which meant
additional weight) or by resorting to some new and untried construction, or
by a proper system of guying. Guying seemingly offered the most feasible
solution of the problem; but although the system of wire guying was
Page 149
thoroughly tried, the result was very unsatisfactory, as the wings continued
to twist and bag in a way that was extremely discouraging.
189 5
I accordingly had recourse in 1895 to the system of wooden guy-sticks
shown in Fig. D, Plate 16, which necessarily added greatly to the weight of
the sustaining surfaces. Each wing was separately strengthened by means of
a light rod of spruce, in cross-section about the size of the main front rib,
extending across the upper surface of the wing, at a distance of about one-
third the width of the wing behind the front rib. It was tied to each of the
cross-ribs and to the outer bent portion of the front rib, and at its root was
fastened to the frame of the aerodrome.
This effectually prevented the bending of the front rib and the consequent
bagging of the cover, and to that extent marked a decided advance in wing
construction. But it was faulty, in that, not being supplemented by wire
guying, it offered little resistance to the twisting of the wing about the main
front rib, the rear tip of the wing being free to turn up under pressure, as it
had done on former occasions. A similar guy-stick was stretched across the
tail. To guard against torsion, rods extending diagonally across the wings
and tail were used, which, with the aid of the guy-sticks just described,
prevented the surfaces from twisting greatly. In addition, a rod joining the
front ribs and stretching across from wing to wing tended to maintain a
fixed diedral angle. [p086]
The wings as thus guyed were rigid enough, and in the field-trials of No.
5 on May 8 and June 6, did not yield noticeably under pressure, and there
seemed to be no serious default in their lifting power, but the guy-sticks
were heavy and the system was not again employed. The wings used in
these trials, shown in Fig. C, Plate 16, had a frame of hickory, consisting of
a front rib and nine cross-ribs, over which the silk was tightly stretched. The
curvature of the wings, which is shown in the cross-sectional drawing, had
a rise of about one-twelfth the width, the highest point of curvature
occurring about one-fourth the distance from front to rear. Each wing was
64 cm. × 192 cm. (25.25 in. × 75.75 in.), the two with the tail, in surface
to twist and bag in a way that was extremely discouraging.
189 5
I accordingly had recourse in 1895 to the system of wooden guy-sticks
shown in Fig. D, Plate 16, which necessarily added greatly to the weight of
the sustaining surfaces. Each wing was separately strengthened by means of
a light rod of spruce, in cross-section about the size of the main front rib,
extending across the upper surface of the wing, at a distance of about one-
third the width of the wing behind the front rib. It was tied to each of the
cross-ribs and to the outer bent portion of the front rib, and at its root was
fastened to the frame of the aerodrome.
This effectually prevented the bending of the front rib and the consequent
bagging of the cover, and to that extent marked a decided advance in wing
construction. But it was faulty, in that, not being supplemented by wire
guying, it offered little resistance to the twisting of the wing about the main
front rib, the rear tip of the wing being free to turn up under pressure, as it
had done on former occasions. A similar guy-stick was stretched across the
tail. To guard against torsion, rods extending diagonally across the wings
and tail were used, which, with the aid of the guy-sticks just described,
prevented the surfaces from twisting greatly. In addition, a rod joining the
front ribs and stretching across from wing to wing tended to maintain a
fixed diedral angle. [p086]
The wings as thus guyed were rigid enough, and in the field-trials of No.
5 on May 8 and June 6, did not yield noticeably under pressure, and there
seemed to be no serious default in their lifting power, but the guy-sticks
were heavy and the system was not again employed. The wings used in
these trials, shown in Fig. C, Plate 16, had a frame of hickory, consisting of
a front rib and nine cross-ribs, over which the silk was tightly stretched. The
curvature of the wings, which is shown in the cross-sectional drawing, had
a rise of about one-twelfth the width, the highest point of curvature
occurring about one-fourth the distance from front to rear. Each wing was
64 cm. × 192 cm. (25.25 in. × 75.75 in.), the two with the tail, in surface
Page 150
equal to a single wing, having an area of 3.7 square metres (40 sq. ft.). The
combined weight of the wings was 1150 grammes (2.53 pounds), and of the
tail, 583 grammes (1.28 pounds).
The evolution of a vertical rudder had meanwhile been going steadily
forward. Those first used had been small, rectangular, stiff, and heavy, but
in the experiments of May 8 a much lighter and larger construction,
consisting of a frame 92 cm. × 76 cm. (36 in. × 30 in.) covered with paper,
was used, and on June 7 this was replaced by a long, diamond-shaped
rudder, having a spruce frame covered with silk, very light and seemingly
more effective than any hitherto used.
I had in the meantime designed a “tail-rudder,” consisting of a horizontal
tail and vertical rudder combined, each having an area of about 0.6 square
metres (6.5 sq. ft.) which, however, was not used until 1896.
In August was begun the construction of a deeply curved and arched pair
of wings for No. 4, which consisted of a light framing of spruce elaborately
guyed and covered with gold-beater’s skin drawn tight as a drum-head with
pyroxelene varnish. In their construction a new feature, foreshadowed in the
method of guying the separate wings used in the field-trials of May and
June, was introduced, which was adopted in all subsequent constructions—
the guy-stick, previously described as stretching lengthwise across the wing
being now made a part of the wing itself, which was thus provided with two
longitudinal ribs instead of one. The additional rib occupied a central
position, and like the front rib was attached to the midrod by means of a
strong wing clamp. Its outer end was united to the front rib, which was here
bent into a quadrant of a circle. This pair of wings had an expanse of 435
cm. (14.3 feet), an area of 2.5 square metres (26.8 sq. ft.), a weight of 660
grammes (1.45 pounds), and a depth of curvature equal to one-tenth their
width.
This construction offered a two-fold advantage in its resistance to both
torsion and bagging, for as the pressures upon the wing were nearly
balanced about the middle rib, the tendency to twist was reduced to a
minimum, while the bagging, which results from the bending of the
framework, as distinct from [p087] its twisting, was greatly reduced by the
combined weight of the wings was 1150 grammes (2.53 pounds), and of the
tail, 583 grammes (1.28 pounds).
The evolution of a vertical rudder had meanwhile been going steadily
forward. Those first used had been small, rectangular, stiff, and heavy, but
in the experiments of May 8 a much lighter and larger construction,
consisting of a frame 92 cm. × 76 cm. (36 in. × 30 in.) covered with paper,
was used, and on June 7 this was replaced by a long, diamond-shaped
rudder, having a spruce frame covered with silk, very light and seemingly
more effective than any hitherto used.
I had in the meantime designed a “tail-rudder,” consisting of a horizontal
tail and vertical rudder combined, each having an area of about 0.6 square
metres (6.5 sq. ft.) which, however, was not used until 1896.
In August was begun the construction of a deeply curved and arched pair
of wings for No. 4, which consisted of a light framing of spruce elaborately
guyed and covered with gold-beater’s skin drawn tight as a drum-head with
pyroxelene varnish. In their construction a new feature, foreshadowed in the
method of guying the separate wings used in the field-trials of May and
June, was introduced, which was adopted in all subsequent constructions—
the guy-stick, previously described as stretching lengthwise across the wing
being now made a part of the wing itself, which was thus provided with two
longitudinal ribs instead of one. The additional rib occupied a central
position, and like the front rib was attached to the midrod by means of a
strong wing clamp. Its outer end was united to the front rib, which was here
bent into a quadrant of a circle. This pair of wings had an expanse of 435
cm. (14.3 feet), an area of 2.5 square metres (26.8 sq. ft.), a weight of 660
grammes (1.45 pounds), and a depth of curvature equal to one-tenth their
width.
This construction offered a two-fold advantage in its resistance to both
torsion and bagging, for as the pressures upon the wing were nearly
balanced about the middle rib, the tendency to twist was reduced to a
minimum, while the bagging, which results from the bending of the
framework, as distinct from [p087] its twisting, was greatly reduced by the
Page 151
manner in which the frame was put together, the whole construction
permitting a return to the system of wire guying at first adopted, which had
been found inapplicable to a wing having but a single longitudinal rib
forming its front margin. When completed, the wings were strongly guyed
with piano wire, both above and below, to guy-posts attached to the midrod,
and each cross-rib was separately guyed with wire chords. Although these
wings had cost much in time and labor, and contained many points of
improvement, they were eventually found to be too weak to support the
aerodrome, and were therefore abandoned without a trial in the field.
For the plane horizontal tail hitherto used a pair of curved wings was
substituted, similar in all respects to those just described, but having only
half their area, and these were later replaced by a pair equal in size and in
every way the counterpart of the front wings. The tail as hitherto used
accordingly disappeared, and gave place to another having a wholly
different function to perform; for while the old tail, like the rear pair of
wings which superseded it, was intended to bear a definite part of the
weight of the aerodrome, the new tail which was now added behind the rear
pair of wings was not supposed to bear any part whatever of the weight, but
to act solely as a guide, and this new feature, first introduced in October,
1895, was continued to the end.
This arrangement of the surfaces is quite different from that adopted by
Pénaud in 1872, in which the tail became automatic in its action through its
small angle of elevation as compared with that of the wings, while still
acting as a supporting surface, whereas in the present arrangement the
function of the tail was solely one of guidance. This, I believe, was one of
the important changes which perhaps as much as any other led to final
success.
During the fall of 1895 a large number of experiments were made both in
free flight with gliding models, and in constrained flight with the whirling-
table, to determine the relative lifting power of the front and rear wings per
unit of area, and from these the following new rules were deduced for
finding the center of pressure:
permitting a return to the system of wire guying at first adopted, which had
been found inapplicable to a wing having but a single longitudinal rib
forming its front margin. When completed, the wings were strongly guyed
with piano wire, both above and below, to guy-posts attached to the midrod,
and each cross-rib was separately guyed with wire chords. Although these
wings had cost much in time and labor, and contained many points of
improvement, they were eventually found to be too weak to support the
aerodrome, and were therefore abandoned without a trial in the field.
For the plane horizontal tail hitherto used a pair of curved wings was
substituted, similar in all respects to those just described, but having only
half their area, and these were later replaced by a pair equal in size and in
every way the counterpart of the front wings. The tail as hitherto used
accordingly disappeared, and gave place to another having a wholly
different function to perform; for while the old tail, like the rear pair of
wings which superseded it, was intended to bear a definite part of the
weight of the aerodrome, the new tail which was now added behind the rear
pair of wings was not supposed to bear any part whatever of the weight, but
to act solely as a guide, and this new feature, first introduced in October,
1895, was continued to the end.
This arrangement of the surfaces is quite different from that adopted by
Pénaud in 1872, in which the tail became automatic in its action through its
small angle of elevation as compared with that of the wings, while still
acting as a supporting surface, whereas in the present arrangement the
function of the tail was solely one of guidance. This, I believe, was one of
the important changes which perhaps as much as any other led to final
success.
During the fall of 1895 a large number of experiments were made both in
free flight with gliding models, and in constrained flight with the whirling-
table, to determine the relative lifting power of the front and rear wings per
unit of area, and from these the following new rules were deduced for
finding the center of pressure:
Page 152
If a following wing is the size of the leader, assume that its efficiency is
66 per cent per unit of surface.
If it is half the size of the leader, assume that its efficiency is 50 per cent
per unit of surface.
If it is half as large again as the leader, assume that its efficiency is 80 per
cent per unit of surface.
For intermediate sizes of surface, proportionate values per unit of surface
may be assumed.
If we consider the area of the front wing to be unity, and that of the rear
wing to be n, and if m be the efficiency of the rear wing per unit of surface,
[p088] the above is expressed in the following formulæ, which it will be
remembered take account only of wings following each other in the same or
nearly the same plane, and are not applicable where one wing is either
above or below the plane of the other. In the formulæ, CP is the resultant
center of pressure upon both wings expressed in the notation described in
Chapter II ◊, CPfw is the center of pressure of the front wings, and CPrw the
center of pressure of the rear wings.
If the value of n lie between one-half and unity,
m = n +3 1 ;
while if the value of n lie between unity and 1 12 ,
m = 6 +154n .
In either case
CPfw + mnCPrw
CP = ;
1 + mn
where the leading and following wings are equal
3CPfw + 2CPrw
n = 1, m = 23 and CP = .
5
The steady flight of one of the gliding models referred to led to the
construction of a new set of wings for No. 5, patterned after those used on
66 per cent per unit of surface.
If it is half the size of the leader, assume that its efficiency is 50 per cent
per unit of surface.
If it is half as large again as the leader, assume that its efficiency is 80 per
cent per unit of surface.
For intermediate sizes of surface, proportionate values per unit of surface
may be assumed.
If we consider the area of the front wing to be unity, and that of the rear
wing to be n, and if m be the efficiency of the rear wing per unit of surface,
[p088] the above is expressed in the following formulæ, which it will be
remembered take account only of wings following each other in the same or
nearly the same plane, and are not applicable where one wing is either
above or below the plane of the other. In the formulæ, CP is the resultant
center of pressure upon both wings expressed in the notation described in
Chapter II ◊, CPfw is the center of pressure of the front wings, and CPrw the
center of pressure of the rear wings.
If the value of n lie between one-half and unity,
m = n +3 1 ;
while if the value of n lie between unity and 1 12 ,
m = 6 +154n .
In either case
CPfw + mnCPrw
CP = ;
1 + mn
where the leading and following wings are equal
3CPfw + 2CPrw
n = 1, m = 23 and CP = .
5
The steady flight of one of the gliding models referred to led to the
construction of a new set of wings for No. 5, patterned after those used on
Page 153
the gliding model. These wings, shown in Plate 17, were rectangular in
outline, 200 cm. × 80 cm. (6.56 ft. × 2.62 ft.), each wing having an area of
1.6 square metres (17.1 sq. ft.) They were constructed with spruce framing
covered with China silk, and were strongly guyed with piano wire in much
the same manner as the light, skin-covered wings already described, which
had preceded them. The combined weight of the two pair was 1950
grammes (4.3 pounds).
The long central rib was now much the larger of the two which, as in the
preceding wing, formed the foundation of the structure. It occupied a
position two-fifths the distance from front to rear, and presumably
coincided at all points with the center of pressure of fore and aft sections of
the wings, so that the pressure in front of the rib was at all points balanced
by the pressure in the rear, and there was consequently little tendency in the
wing to twist under pressure of the wind. The two main ribs were rigidly
connected by cross-ribs of spruce, 20 cm. (8 inches) apart, steamed and bent
to the desired form. The curvature of these ribs was the same for all, and in
depth was one-twelfth the width of the wing, while the highest point of
curvature was one-sixth of the distance from front to rear, these ratios
having been chosen as approximating those found in the wing of the soaring
bird. These wings were subsequently used in the first successful flights of
the following year.
outline, 200 cm. × 80 cm. (6.56 ft. × 2.62 ft.), each wing having an area of
1.6 square metres (17.1 sq. ft.) They were constructed with spruce framing
covered with China silk, and were strongly guyed with piano wire in much
the same manner as the light, skin-covered wings already described, which
had preceded them. The combined weight of the two pair was 1950
grammes (4.3 pounds).
The long central rib was now much the larger of the two which, as in the
preceding wing, formed the foundation of the structure. It occupied a
position two-fifths the distance from front to rear, and presumably
coincided at all points with the center of pressure of fore and aft sections of
the wings, so that the pressure in front of the rib was at all points balanced
by the pressure in the rear, and there was consequently little tendency in the
wing to twist under pressure of the wind. The two main ribs were rigidly
connected by cross-ribs of spruce, 20 cm. (8 inches) apart, steamed and bent
to the desired form. The curvature of these ribs was the same for all, and in
depth was one-twelfth the width of the wing, while the highest point of
curvature was one-sixth of the distance from front to rear, these ratios
having been chosen as approximating those found in the wing of the soaring
bird. These wings were subsequently used in the first successful flights of
the following year.
Page 154
PL. 17. AERODROME NO. 5. PLAN OF WINGS AND SYSTEM OF GUYING ◊
[p089]
[p089]
Page 155
During the year 1895 but two field-trials were made with the steam
aerodromes, and neither of these was successful; but a great step forward
had been taken in the construction, guying and arrangement of the
sustaining surfaces. The wings had been made stronger with no increase in
weight per unit of area. On the contrary, the ratio of weight of sustaining
surfaces to area had been actually reduced from 43 to 28 grammes per
square foot, so that the surfaces were both lighter and stronger.
Two longitudinal ribs had taken the place of the single one before used, a
second wing clamp had been added to correspond to the midrib, the difficult
problem of torsion had been effectually solved, the system of guying greatly
improved, and it appeared that in the next trial the wings might be expected
to bear the weight of the aerodrome without serious distortion.
189 6
In January, 1896, two new pairs of wings were designed for No. 6, and in
order to give a greater efficiency to the rear wings, they were made larger
than the front ones, the area of the latter being 22 square feet, and of the
former 27 square feet, and whereas the width of each wing had formerly
been one-third of its length, it was now increased to two-fifths to
correspond to those of No. 5.
The progress made in construction and guying is shown by the fact that
when on January 28 one pair of the wings of No. 5 was inverted and
sanded, the yielding at the tip was less than 5° greater than at the root,
whereas at one time it had been 65°. A similar test applied to a pair of wings
of No. 6 on March 4 gave even better results, as the yield at the root was but
1° 45′, and at the tip 2° 30′.
The successive stages of the development of the wing clamps are shown
in Fig. 16. In its final form the front wing clamp, or that which held the
main front rib, shown at AB (1896), had adjustable sliding pieces, by means
of which the wings could be set at any desired angle of elevation, the wing
as a whole revolving about the rear wing clamp, shown at CD (1896).
The general system of guying the wings, as shown in Plate 17, had been
greatly improved. In the present form a bowsprit and guy-posts firmly
aerodromes, and neither of these was successful; but a great step forward
had been taken in the construction, guying and arrangement of the
sustaining surfaces. The wings had been made stronger with no increase in
weight per unit of area. On the contrary, the ratio of weight of sustaining
surfaces to area had been actually reduced from 43 to 28 grammes per
square foot, so that the surfaces were both lighter and stronger.
Two longitudinal ribs had taken the place of the single one before used, a
second wing clamp had been added to correspond to the midrib, the difficult
problem of torsion had been effectually solved, the system of guying greatly
improved, and it appeared that in the next trial the wings might be expected
to bear the weight of the aerodrome without serious distortion.
189 6
In January, 1896, two new pairs of wings were designed for No. 6, and in
order to give a greater efficiency to the rear wings, they were made larger
than the front ones, the area of the latter being 22 square feet, and of the
former 27 square feet, and whereas the width of each wing had formerly
been one-third of its length, it was now increased to two-fifths to
correspond to those of No. 5.
The progress made in construction and guying is shown by the fact that
when on January 28 one pair of the wings of No. 5 was inverted and
sanded, the yielding at the tip was less than 5° greater than at the root,
whereas at one time it had been 65°. A similar test applied to a pair of wings
of No. 6 on March 4 gave even better results, as the yield at the root was but
1° 45′, and at the tip 2° 30′.
The successive stages of the development of the wing clamps are shown
in Fig. 16. In its final form the front wing clamp, or that which held the
main front rib, shown at AB (1896), had adjustable sliding pieces, by means
of which the wings could be set at any desired angle of elevation, the wing
as a whole revolving about the rear wing clamp, shown at CD (1896).
The general system of guying the wings, as shown in Plate 17, had been
greatly improved. In the present form a bowsprit and guy-posts firmly
Page 156
attached to the midrod furnished points of attachment for the piano wires
with which the wings were guyed and held rigidly in place, other wires
being stretched across from wing to wing so as to maintain them at a
constant diedral angle of about 150°. The clamps by which the guy-posts
were attached to the midrod, are shown at EF (Fig. 16).
In the successful flights of No. 5 on May 6, the completed wings already
described weighed together 1950 grammes (4.29 pounds), and had a total
sustaining area of 6.4 square metres (68.8 square feet), the flying weight of
the [p090] aerodrome was 11,775 grammes (26 pounds), and the sustaining
surfaces therefore amounted to 2.6 square feet to the pound, which, as the
event proved, was amply sufficient.
The “tail-rudder,” shown in Plate 17, comprised a vertical and horizontal
surface of silk intersecting in a central rod or axis, having a length of 115
cm. (3.8 feet). The framing was of spruce and consisted of two sets of four
arms, each radiating from the central rod, the hexagonal outline of the
surfaces being formed of piano wire, over which the silk was drawn and
sewed. The area of each surface was about 0.6 square metres (6.45 square
feet), and the total weight was 371 grammes (0.8 pounds).
A flat steel spring inserted in the forward end between the rudder and the
midrod gave it a certain desirable degree of elasticity in a vertical direction.
The rudder was held in place by a pin passing through the midrod, and was
so set as to coincide with the line of direct flight, its purpose, as already
explained, being to guide the aerodrome, but to take no part in its
sustention.
In balancing Aerodrome No. 5 on May 6, the wings were so adjusted that
in accordance with the notation given above, p. 15:
CPfw = 1575
CPrw = 1415.5;
and as the wings were of equal size, from what has preceded in the present
3CPfw + 2CPrw
CP1 = = 1501.2.
5
with which the wings were guyed and held rigidly in place, other wires
being stretched across from wing to wing so as to maintain them at a
constant diedral angle of about 150°. The clamps by which the guy-posts
were attached to the midrod, are shown at EF (Fig. 16).
In the successful flights of No. 5 on May 6, the completed wings already
described weighed together 1950 grammes (4.29 pounds), and had a total
sustaining area of 6.4 square metres (68.8 square feet), the flying weight of
the [p090] aerodrome was 11,775 grammes (26 pounds), and the sustaining
surfaces therefore amounted to 2.6 square feet to the pound, which, as the
event proved, was amply sufficient.
The “tail-rudder,” shown in Plate 17, comprised a vertical and horizontal
surface of silk intersecting in a central rod or axis, having a length of 115
cm. (3.8 feet). The framing was of spruce and consisted of two sets of four
arms, each radiating from the central rod, the hexagonal outline of the
surfaces being formed of piano wire, over which the silk was drawn and
sewed. The area of each surface was about 0.6 square metres (6.45 square
feet), and the total weight was 371 grammes (0.8 pounds).
A flat steel spring inserted in the forward end between the rudder and the
midrod gave it a certain desirable degree of elasticity in a vertical direction.
The rudder was held in place by a pin passing through the midrod, and was
so set as to coincide with the line of direct flight, its purpose, as already
explained, being to guide the aerodrome, but to take no part in its
sustention.
In balancing Aerodrome No. 5 on May 6, the wings were so adjusted that
in accordance with the notation given above, p. 15:
CPfw = 1575
CPrw = 1415.5;
and as the wings were of equal size, from what has preceded in the present
3CPfw + 2CPrw
CP1 = = 1501.2.
5
Page 157
The center of gravity was located at 1497, so that there should have been a
very slight tendency on the part of the aerodrome to rise, as was actually the
case. The formula was perhaps not quite so accurate as the prolonged flight
of the aerodrome would seem to indicate, as it takes no account of the thrust
of the propellers, which in action tended to elevate the aerodrome in front
while their resistance would tend to depress it when they had ceased to
revolve, which consideration accounts for the action of the aerodrome on
May 6, as described in Chapter IX ◊. The formula may, however, be
regarded as approximately correct.
In the final successful trial with No. 6 on November 28, 1896, the wings
used were similar in general construction and manner of guying to those of
No. 5 on May 6, but, as shown in the photograph (Plate 29A, Chapter X),
the front rib at its outer extremity was bent to a quadrant to connect with the
midrib, this construction being somewhat stronger than that adopted in the
wings of No. 5. The curvature was but one-eighteenth of the width of the
wing instead of one-twelfth as in No. 5. The front and rear pairs were
similar and equal and had a combined area of 5 square metres (54 sq. ft.),
and a weight of 2154 grammes [p091] (4.74 lbs.). The flying weight of the
aerodrome was 12,120 grammes (26.7 lbs.), the sustaining surface thus
amounting to slightly more than 2 square feet to the pound.
The position of the wings, in accordance with the notation adopted, was
CPfw = 1563.2,
CPrw = 1374.
Since the wings were equal in size,
3CPfw + 2CPrw
CP1 = = 1487.5.
5
The center of gravity was located at 1484, which was 3.5 cm. in the rear of
the center of pressure. The flight was approximately horizontal, and the
setting seems to have been as accurate as could be desired. The angle of
elevation of the wings at the root was 10° 30′, and so well were they guyed
that there was no visible yielding at any point during the flight. As the
very slight tendency on the part of the aerodrome to rise, as was actually the
case. The formula was perhaps not quite so accurate as the prolonged flight
of the aerodrome would seem to indicate, as it takes no account of the thrust
of the propellers, which in action tended to elevate the aerodrome in front
while their resistance would tend to depress it when they had ceased to
revolve, which consideration accounts for the action of the aerodrome on
May 6, as described in Chapter IX ◊. The formula may, however, be
regarded as approximately correct.
In the final successful trial with No. 6 on November 28, 1896, the wings
used were similar in general construction and manner of guying to those of
No. 5 on May 6, but, as shown in the photograph (Plate 29A, Chapter X),
the front rib at its outer extremity was bent to a quadrant to connect with the
midrib, this construction being somewhat stronger than that adopted in the
wings of No. 5. The curvature was but one-eighteenth of the width of the
wing instead of one-twelfth as in No. 5. The front and rear pairs were
similar and equal and had a combined area of 5 square metres (54 sq. ft.),
and a weight of 2154 grammes [p091] (4.74 lbs.). The flying weight of the
aerodrome was 12,120 grammes (26.7 lbs.), the sustaining surface thus
amounting to slightly more than 2 square feet to the pound.
The position of the wings, in accordance with the notation adopted, was
CPfw = 1563.2,
CPrw = 1374.
Since the wings were equal in size,
3CPfw + 2CPrw
CP1 = = 1487.5.
5
The center of gravity was located at 1484, which was 3.5 cm. in the rear of
the center of pressure. The flight was approximately horizontal, and the
setting seems to have been as accurate as could be desired. The angle of
elevation of the wings at the root was 10° 30′, and so well were they guyed
that there was no visible yielding at any point during the flight. As the
Page 158
midrod during flight was approximately horizontal the angle of elevation of
the wings may be taken as 10° 30′; the efficiency of the rear wings was two-
thirds that of the front wings, and the effective area was therefore 27+27× 23
= 45 square feet.
The wings being very nearly plane we have therefore the data for
determining the soaring speed from the formula of “Aerodynamics”
(Chapter VI, p. 60).
W = Pα cos α = kAV 2F (α) cos α,
in which W = 26.7 pounds; A = 45 sq. ft.; k = 0.00166; α = 10° 30′; F (α)
cos α = 0.353. By substituting these values in the formula we obtain V = 32
feet per second.
The speed actually attained, however, was about 30 miles an hour, or 44
feet per second, which seems to indicate that the angle of elevation under
pressure was reduced to much less than 10° 30′. For a velocity of 44 feet
per second, the theoretical value of α would be but 6°. In this calculation,
however, the hull resistance and that of the system of guy-wires, which
must have been comparatively large, has been omitted. It would appear,
therefore, that the actual results obtainable in flight are much more
favorable than calculations based on experimental data would presuppose.
the wings may be taken as 10° 30′; the efficiency of the rear wings was two-
thirds that of the front wings, and the effective area was therefore 27+27× 23
= 45 square feet.
The wings being very nearly plane we have therefore the data for
determining the soaring speed from the formula of “Aerodynamics”
(Chapter VI, p. 60).
W = Pα cos α = kAV 2F (α) cos α,
in which W = 26.7 pounds; A = 45 sq. ft.; k = 0.00166; α = 10° 30′; F (α)
cos α = 0.353. By substituting these values in the formula we obtain V = 32
feet per second.
The speed actually attained, however, was about 30 miles an hour, or 44
feet per second, which seems to indicate that the angle of elevation under
pressure was reduced to much less than 10° 30′. For a velocity of 44 feet
per second, the theoretical value of α would be but 6°. In this calculation,
however, the hull resistance and that of the system of guy-wires, which
must have been comparatively large, has been omitted. It would appear,
therefore, that the actual results obtainable in flight are much more
favorable than calculations based on experimental data would presuppose.
Page 159
[p092] ◊
CHAPTER IX
HISTORY OF LAUNCHING APPARATUS AND FIELD-TRIALS
OF AERODROMES 4, 5 AND 6
L AUNCHING A PPARATUS
I have elsewhere mentioned that the difficulties of launching even a very
small model aerodrome are considerable. Early experiments were tried with
an apparatus something like a gigantic cross-bow, and in later years with
various forms of pendulum, all of which latter brought out the inherent
theoretical defect of the movement of rotation of the aerodrome, and were
otherwise practically inefficient.
A device, consisting of two pendulums, one behind the other, connected
by a rigid rod, from which the aerodrome could be suspended and cast off
without rotation, was at one time considered, but abandoned. Experiments
were also made with several forms of railroad, upon which the aerodrome
was to run up to the moment of release, before the form of launching
apparatus, which finally proved successful, was adopted.
All these had failed chiefly for two reasons; first, it was difficult to cause
the aerodrome to be released just at the moment it attained sufficient speed
to soar; second, the extensive surface presented to the wind by the wings of
the aerodrome, made it necessary to provide means for holding the machine
securely at several points up to the moment of release without danger of
interfering in any way with the aerodrome when it was cast into the air. This
proved a serious problem, which can be appreciated only by one who has
seen such a machine in the open air, where its wings are subject to
movement and distortion by the slightest breeze. The steps by which these
difficulties were removed and the final type of launching apparatus
perfected are recorded in the following pages in connection with the field-
trials of the model aerodromes.
189 2
CHAPTER IX
HISTORY OF LAUNCHING APPARATUS AND FIELD-TRIALS
OF AERODROMES 4, 5 AND 6
L AUNCHING A PPARATUS
I have elsewhere mentioned that the difficulties of launching even a very
small model aerodrome are considerable. Early experiments were tried with
an apparatus something like a gigantic cross-bow, and in later years with
various forms of pendulum, all of which latter brought out the inherent
theoretical defect of the movement of rotation of the aerodrome, and were
otherwise practically inefficient.
A device, consisting of two pendulums, one behind the other, connected
by a rigid rod, from which the aerodrome could be suspended and cast off
without rotation, was at one time considered, but abandoned. Experiments
were also made with several forms of railroad, upon which the aerodrome
was to run up to the moment of release, before the form of launching
apparatus, which finally proved successful, was adopted.
All these had failed chiefly for two reasons; first, it was difficult to cause
the aerodrome to be released just at the moment it attained sufficient speed
to soar; second, the extensive surface presented to the wind by the wings of
the aerodrome, made it necessary to provide means for holding the machine
securely at several points up to the moment of release without danger of
interfering in any way with the aerodrome when it was cast into the air. This
proved a serious problem, which can be appreciated only by one who has
seen such a machine in the open air, where its wings are subject to
movement and distortion by the slightest breeze. The steps by which these
difficulties were removed and the final type of launching apparatus
perfected are recorded in the following pages in connection with the field-
trials of the model aerodromes.
189 2
Page 160
As the end of the year 1892 approached and with it the completion of an
aerodrome of large size which had to be started upon its flight in some way,
the method and place of launching it pressed for decision. One thing at least
seemed clear. In the present stage of experiment, it was desirable that the
aerodrome should-—if it must fall-—fall into water where it would suffer
little injury and be readily recovered, rather than anywhere on land, where it
would almost certainly be badly damaged. [p093]
The shores of the Potomac on both banks were scrutinized for this
purpose, from a point about two miles above Washington to below
Chopawamsic Island, some thirty miles below the city. Several lofty and
secluded positions were found, but in all these there was the danger that the
aerodrome might be wrecked before reaching the water, or, turning in its
course, fly inland; but more than this, it could be launched only on the rare
occasions when the exact wind was blowing which the local conditions
demanded.
Finally, the idea, which seems obvious enough when stated, presented
itself of building a kind of house-boat, not to get up initial motion by the
boat’s own velocity, but to furnish an elevated platform, which could be
placed in the midst of a considerable expanse of water, if desired, under
conditions which admitted of turning in the direction of the wind, as it need
hardly be repeated that it was indispensable to the machine, as it is to the
bird, to rise in the face of a wind, if there be any wind at all.
The house-boat in question was nothing more than a scow about 30 feet
long by 12 feet wide, upon which a small house was erected, to be used for
the occasional storing of the aerodromes. On account of the accidents which
were certain to occur in the first attempts, it was fitted up with the means of
making small repairs. On the roof of the house there was a platform upon
which the operator stood when making a launch, and upon which were
mounted the launching devices hereafter described.
This boat, shown in Plate 18, was completed in November, 1892.
189 3
aerodrome of large size which had to be started upon its flight in some way,
the method and place of launching it pressed for decision. One thing at least
seemed clear. In the present stage of experiment, it was desirable that the
aerodrome should-—if it must fall-—fall into water where it would suffer
little injury and be readily recovered, rather than anywhere on land, where it
would almost certainly be badly damaged. [p093]
The shores of the Potomac on both banks were scrutinized for this
purpose, from a point about two miles above Washington to below
Chopawamsic Island, some thirty miles below the city. Several lofty and
secluded positions were found, but in all these there was the danger that the
aerodrome might be wrecked before reaching the water, or, turning in its
course, fly inland; but more than this, it could be launched only on the rare
occasions when the exact wind was blowing which the local conditions
demanded.
Finally, the idea, which seems obvious enough when stated, presented
itself of building a kind of house-boat, not to get up initial motion by the
boat’s own velocity, but to furnish an elevated platform, which could be
placed in the midst of a considerable expanse of water, if desired, under
conditions which admitted of turning in the direction of the wind, as it need
hardly be repeated that it was indispensable to the machine, as it is to the
bird, to rise in the face of a wind, if there be any wind at all.
The house-boat in question was nothing more than a scow about 30 feet
long by 12 feet wide, upon which a small house was erected, to be used for
the occasional storing of the aerodromes. On account of the accidents which
were certain to occur in the first attempts, it was fitted up with the means of
making small repairs. On the roof of the house there was a platform upon
which the operator stood when making a launch, and upon which were
mounted the launching devices hereafter described.
This boat, shown in Plate 18, was completed in November, 1892.
189 3
Page 161
By the kindness of the Superintendent of the Coast Survey, the house-
boat was towed in May, 1893, down to Chopawamsic Island, a small island
near the western bank of the Potomac River, not far from the Quantico
station of the Washington and Richmond Railroad Company. A map of the
island and the adjacent land and water is shown in Plate 19.
The house-boat was at all times moored somewhere on the west side of
the island, in the stretch of quiet water between that and the west shore of
the river. The waters shown here are, with the exception of a narrow
channel, very shallow, and, indeed, partly dry at low tide, so that there was
no danger of an aerodrome being lost, unless its flight carried it a long
distance away and over the land.
F IELD T RIALS 2 9
Aerodrome No. 4, as shown in Plate 11, had a single midrod, a flying
weight of 9 pounds,30 and supporting surface, consisting of wings and tail,
of 18 square feet. [p094] Its engines, with about 100 pounds pressure,
developed an aggregate of 0.4 H. P., and lifted 50 per cent of the flying
weight. The propellers were 60 cm. (2 feet) in diameter and 1 14 pitch ratio.
The aerodrome was intended to be launched by a contrivance called the
“starter,” which was an inclined rod, hinged at the bottom, on the top of
which the aerodrome was supported on a rod which was thrown down at the
instant of flight, giving the aerodrome a slight forward impulse, with the
expectation that it would get up sufficient initial speed to soar from the
action of its propellers.
On November 18 the writer (L), with Dr. Barus (B) and the two
mechanics (R and M), went to Quantico by an early train, and
superintended with interested expectation the arrangements for this first
trial in the open air of the mechanism which had now been over two years
in preparation.
We met with an unexpected difficulty—that of launching the aerodrome
at all, for though the wind was only a very gentle breeze, it was only by
holding it down with the hands that it was possible to keep the aerodrome in
boat was towed in May, 1893, down to Chopawamsic Island, a small island
near the western bank of the Potomac River, not far from the Quantico
station of the Washington and Richmond Railroad Company. A map of the
island and the adjacent land and water is shown in Plate 19.
The house-boat was at all times moored somewhere on the west side of
the island, in the stretch of quiet water between that and the west shore of
the river. The waters shown here are, with the exception of a narrow
channel, very shallow, and, indeed, partly dry at low tide, so that there was
no danger of an aerodrome being lost, unless its flight carried it a long
distance away and over the land.
F IELD T RIALS 2 9
Aerodrome No. 4, as shown in Plate 11, had a single midrod, a flying
weight of 9 pounds,30 and supporting surface, consisting of wings and tail,
of 18 square feet. [p094] Its engines, with about 100 pounds pressure,
developed an aggregate of 0.4 H. P., and lifted 50 per cent of the flying
weight. The propellers were 60 cm. (2 feet) in diameter and 1 14 pitch ratio.
The aerodrome was intended to be launched by a contrivance called the
“starter,” which was an inclined rod, hinged at the bottom, on the top of
which the aerodrome was supported on a rod which was thrown down at the
instant of flight, giving the aerodrome a slight forward impulse, with the
expectation that it would get up sufficient initial speed to soar from the
action of its propellers.
On November 18 the writer (L), with Dr. Barus (B) and the two
mechanics (R and M), went to Quantico by an early train, and
superintended with interested expectation the arrangements for this first
trial in the open air of the mechanism which had now been over two years
in preparation.
We met with an unexpected difficulty—that of launching the aerodrome
at all, for though the wind was only a very gentle breeze, it was only by
holding it down with the hands that it was possible to keep the aerodrome in
Page 162
position for the launch, during the few minutes which passed from the time
it was placed upon the apparatus to the time of releasing it. Whether the
launching device itself might be effective or not could not be ascertained,
since it was found that nothing which could even be called an attempt to
launch could be made except in an absolute calm; a condition of things very
difficult for any one to understand who has not passed through the
experience. The writer returned to Washington at the close of the day
without having done anything, but having learned a great deal.
November 20. L, with B and M, came down again, and waited until 4.20,
when, the breeze having fallen to almost a calm, the aerodrome was
maintained in place on the launching apparatus with great difficulty, while it
was repeatedly set on fire by the scattering liquid fuel. Finally it was let go,
and fell close to the house-boat, the tail striking the edge of the platform.
The immediate cause of failure was the defective launching apparatus, for
the design of which the writer felt himself responsible.
November 24. L, with B, M, and R came down again to Quantico, but the
very moderate wind proved completely prohibitory to any attempt at
launching, and all returned again to Washington.
November 27. L, with B and M, came down to try a new launching
apparatus, not different in principle from the preceding one, but of better
construction. The morning was exceptionally calm, but the engines were
found to be out of order, and precious time was spent in slight repairs which
should have been made in the shop. At 3.30 p. m., when the engines were at
last ready, the exceptional calm gave place to a very gentle and almost
imperceptible breeze, [p095] which, nevertheless, again proved prohibitory to
the launching, and with extreme disappointment the party returned to
Washington, it being at last fully recognized that unless some ways were
found of holding down all the extended supporting surfaces upon the
launching piece, and at the same time of firmly clamping the body of the
aerodrome until it could be dropped, as well as of releasing all this
simultaneously at the critical instant, no attempt at launching was likely to
succeed except in such an entire and perfect calm as rarely occurs.
Independent of this launching difficulty, some way of protecting the fires
it was placed upon the apparatus to the time of releasing it. Whether the
launching device itself might be effective or not could not be ascertained,
since it was found that nothing which could even be called an attempt to
launch could be made except in an absolute calm; a condition of things very
difficult for any one to understand who has not passed through the
experience. The writer returned to Washington at the close of the day
without having done anything, but having learned a great deal.
November 20. L, with B and M, came down again, and waited until 4.20,
when, the breeze having fallen to almost a calm, the aerodrome was
maintained in place on the launching apparatus with great difficulty, while it
was repeatedly set on fire by the scattering liquid fuel. Finally it was let go,
and fell close to the house-boat, the tail striking the edge of the platform.
The immediate cause of failure was the defective launching apparatus, for
the design of which the writer felt himself responsible.
November 24. L, with B, M, and R came down again to Quantico, but the
very moderate wind proved completely prohibitory to any attempt at
launching, and all returned again to Washington.
November 27. L, with B and M, came down to try a new launching
apparatus, not different in principle from the preceding one, but of better
construction. The morning was exceptionally calm, but the engines were
found to be out of order, and precious time was spent in slight repairs which
should have been made in the shop. At 3.30 p. m., when the engines were at
last ready, the exceptional calm gave place to a very gentle and almost
imperceptible breeze, [p095] which, nevertheless, again proved prohibitory to
the launching, and with extreme disappointment the party returned to
Washington, it being at last fully recognized that unless some ways were
found of holding down all the extended supporting surfaces upon the
launching piece, and at the same time of firmly clamping the body of the
aerodrome until it could be dropped, as well as of releasing all this
simultaneously at the critical instant, no attempt at launching was likely to
succeed except in such an entire and perfect calm as rarely occurs.
Independent of this launching difficulty, some way of protecting the fires
Page 163
from the wind had to be found, which was by no means easy, since an
efficient protection meant an enclosure of them and a diminished influx of
air, of which it was essential that there should be an unlimited supply.
December 1. L, with B, R, and M proceeded to Quantico. The same
conditions presented themselves and the party returned, without effecting
anything.
December 7. L, B, R, and M present; day overcast but perfectly calm.
Taught by experience, we had everything ready, and a little after one
o’clock the launch was made. The aerodrome fell directly into the boat, the
rod of the starter having broken. It was little damaged, but in view of the
injury and the rising wind, all other attempts were abandoned for the day.
December 11. Present, L, with B, R, and M. A new “starter” had been
devised and brought down, but was not yet quite ready for use, and an
attempt was made to employ the old one with the improvements suggested
by experience, but, after two attempts to launch, the work was abandoned
for the day, owing this time not to the launching apparatus, but to troubles
in the engines and pumps, due probably to injuries received in the fall of the
7th, which were not detected until the time of the actual trial.
December 20. L, with B, M, and G, present; engine and aerodrome in
order and everything apparently favorable. What seemed to be an almost
entire calm came toward evening, yet once more the all but imperceptible
breeze which prevailed was found to defeat all arrangements for holding the
aerodrome to the launching ways before it was let go.
Trips to Quantico were also made on November 24, and December 1 and
21, of which no account is given as the very moderate wind which prevailed
in each case precluded any attempt at launching the aerodrome.
It will be seen that eight trips were made to Quantico, and that, far from
any flight having been made, not once even was the aerodrome launched at
all. The principal cause for this lay in the unrecognized amount of difficulty
introduced by the very smallest wind, irrespective of the unfitness of the
launching apparatus to give the desired initial speed and direction.
In all these trials, the aerodrome rested on the launching apparatus, by
which it was projected forward by means of a spring in such a way as not to
efficient protection meant an enclosure of them and a diminished influx of
air, of which it was essential that there should be an unlimited supply.
December 1. L, with B, R, and M proceeded to Quantico. The same
conditions presented themselves and the party returned, without effecting
anything.
December 7. L, B, R, and M present; day overcast but perfectly calm.
Taught by experience, we had everything ready, and a little after one
o’clock the launch was made. The aerodrome fell directly into the boat, the
rod of the starter having broken. It was little damaged, but in view of the
injury and the rising wind, all other attempts were abandoned for the day.
December 11. Present, L, with B, R, and M. A new “starter” had been
devised and brought down, but was not yet quite ready for use, and an
attempt was made to employ the old one with the improvements suggested
by experience, but, after two attempts to launch, the work was abandoned
for the day, owing this time not to the launching apparatus, but to troubles
in the engines and pumps, due probably to injuries received in the fall of the
7th, which were not detected until the time of the actual trial.
December 20. L, with B, M, and G, present; engine and aerodrome in
order and everything apparently favorable. What seemed to be an almost
entire calm came toward evening, yet once more the all but imperceptible
breeze which prevailed was found to defeat all arrangements for holding the
aerodrome to the launching ways before it was let go.
Trips to Quantico were also made on November 24, and December 1 and
21, of which no account is given as the very moderate wind which prevailed
in each case precluded any attempt at launching the aerodrome.
It will be seen that eight trips were made to Quantico, and that, far from
any flight having been made, not once even was the aerodrome launched at
all. The principal cause for this lay in the unrecognized amount of difficulty
introduced by the very smallest wind, irrespective of the unfitness of the
launching apparatus to give the desired initial speed and direction.
In all these trials, the aerodrome rested on the launching apparatus, by
which it was projected forward by means of a spring in such a way as not to
Page 164
interfere with the propellers. [p096]
Previous tests with the rubber-driven models had demonstrated the
futility of all simple pendulum types of “cast off,” and likewise all the trials
hitherto of a railroad form of launching apparatus, in which the aerodrome
was mounted on a car, which had itself to get out of the way, were equally
failures, so that when the device referred to above proved to be worthless, it
seemed that almost every plan had been exhausted. There were, moreover,
other difficulties, some of which have been indicated above, such as that of
making the burners work properly in even a moderate wind during the very
short time required for attaching the wings and so adjusting the aerodrome
on the launching apparatus.
These difficulties, which, now that they have been overcome, seem
difficulties no longer, but which then seemed insuperable, were all
connected with the ever-present problem of weight. It would have been easy
to make rigid sustaining surfaces which would not bend in the wind; to
make fires which would not go out; and easy to overcome all the
impediments which seem so trivial in description and were so formidable in
practice, were it not that the mandate of absolute necessity forbade this
being done by any contrivance which would add to the weight of an already
phenomenally light construction. The difficulties of the flight as they were
seen in the workshop were multiplied, then, beyond measure by the actual
experiments in the field, and the year closed with a most discouraging
outlook.
189 4
The new year began without any essential improvement in the means
already described, though a new launching apparatus had been devised by
the writer, which was scarcely so much an apparatus for launching, in the
ordinary sense of the word, as one of holding the aerodrome out over the
water, and simply letting it drop from a height of about 25 feet, during
which fall it was hoped (exact data being unobtainable in advance of
experiment) that there would be time for the propellers to give the
aerodrome the necessary soaring speed before reaching the water. This
Previous tests with the rubber-driven models had demonstrated the
futility of all simple pendulum types of “cast off,” and likewise all the trials
hitherto of a railroad form of launching apparatus, in which the aerodrome
was mounted on a car, which had itself to get out of the way, were equally
failures, so that when the device referred to above proved to be worthless, it
seemed that almost every plan had been exhausted. There were, moreover,
other difficulties, some of which have been indicated above, such as that of
making the burners work properly in even a moderate wind during the very
short time required for attaching the wings and so adjusting the aerodrome
on the launching apparatus.
These difficulties, which, now that they have been overcome, seem
difficulties no longer, but which then seemed insuperable, were all
connected with the ever-present problem of weight. It would have been easy
to make rigid sustaining surfaces which would not bend in the wind; to
make fires which would not go out; and easy to overcome all the
impediments which seem so trivial in description and were so formidable in
practice, were it not that the mandate of absolute necessity forbade this
being done by any contrivance which would add to the weight of an already
phenomenally light construction. The difficulties of the flight as they were
seen in the workshop were multiplied, then, beyond measure by the actual
experiments in the field, and the year closed with a most discouraging
outlook.
189 4
The new year began without any essential improvement in the means
already described, though a new launching apparatus had been devised by
the writer, which was scarcely so much an apparatus for launching, in the
ordinary sense of the word, as one of holding the aerodrome out over the
water, and simply letting it drop from a height of about 25 feet, during
which fall it was hoped (exact data being unobtainable in advance of
experiment) that there would be time for the propellers to give the
aerodrome the necessary soaring speed before reaching the water. This
Page 165
device consisted of an inverted tripod, which held the aerodrome
comparatively steady by three bearing points, while a cross-bar of wood
was added to prevent the wings from swaying before the launch. Previously,
the supporting surfaces, wings and tail, had been put on only at the last
minute. Now it became possible to keep them on in a gentle breeze for an
indefinite time before launching.
January 9. The previous day having been spent in practicing the steps
preliminary to launching, so as to avoid delay in assembling and mounting
the aerodrome, the writer, with Dr. Graham Bell, went to Quantico. The day
was calm, and every condition seemed favorable. The aerodrome was
dropped fairly, under full steam, and it fell in a nearly horizontal position,
but touched the water at a distance of only 50 or 60 feet, evidently before
the necessary initial speed [p097] could be impressed on it by its engines. The
conclusion should have been that by this method nothing but a practically
unsuitable height would suffice to start the aerodrome in a calm, though it
might perhaps be done in the face of a considerable breeze.
May 25. After a considerable interval of delay, due to the river being
closed by ice and other causes, Aerodrome No. 4 was again dropped from
the starter under nearly the same conditions as in the trial of January 9, and
with a quite similar result, the final conclusion being that this method must
be abandoned. It may be added that a vertical rudder was tried on this day.
June 12. No. 4, with an improved blast, was tried at Quantico, Mr. Goode
being present. The day ended in failure from another cause, the improved
blast, which worked well in the shelter of the shop, but proved useless in
the field, being extinguished by the feeblest wind. At this time (in June and
July) I designed a horizontal railroad with launching springs and track,
underneath which ran a car which held the aerodrome firmly until the
moment of automatic release. This apparatus finally proved to be the
successful solution of the launching problem. The description given later,
with the drawing in Plate 18, shows the after-improvements, but no specific
change from that in use from the first.
About this time I also arranged for certain changes in the boilers and
burners, having decided that I would not go into the field without some
comparatively steady by three bearing points, while a cross-bar of wood
was added to prevent the wings from swaying before the launch. Previously,
the supporting surfaces, wings and tail, had been put on only at the last
minute. Now it became possible to keep them on in a gentle breeze for an
indefinite time before launching.
January 9. The previous day having been spent in practicing the steps
preliminary to launching, so as to avoid delay in assembling and mounting
the aerodrome, the writer, with Dr. Graham Bell, went to Quantico. The day
was calm, and every condition seemed favorable. The aerodrome was
dropped fairly, under full steam, and it fell in a nearly horizontal position,
but touched the water at a distance of only 50 or 60 feet, evidently before
the necessary initial speed [p097] could be impressed on it by its engines. The
conclusion should have been that by this method nothing but a practically
unsuitable height would suffice to start the aerodrome in a calm, though it
might perhaps be done in the face of a considerable breeze.
May 25. After a considerable interval of delay, due to the river being
closed by ice and other causes, Aerodrome No. 4 was again dropped from
the starter under nearly the same conditions as in the trial of January 9, and
with a quite similar result, the final conclusion being that this method must
be abandoned. It may be added that a vertical rudder was tried on this day.
June 12. No. 4, with an improved blast, was tried at Quantico, Mr. Goode
being present. The day ended in failure from another cause, the improved
blast, which worked well in the shelter of the shop, but proved useless in
the field, being extinguished by the feeblest wind. At this time (in June and
July) I designed a horizontal railroad with launching springs and track,
underneath which ran a car which held the aerodrome firmly until the
moment of automatic release. This apparatus finally proved to be the
successful solution of the launching problem. The description given later,
with the drawing in Plate 18, shows the after-improvements, but no specific
change from that in use from the first.
About this time I also arranged for certain changes in the boilers and
burners, having decided that I would not go into the field without some
Page 166
ground for confidence not only that the aerodrome could be launched
successfully, but that a steady flame could be maintained under the boilers.
October 6. No. 4, as remodelled, having a flying weight of about 14.5
pounds, a supporting surface of about 28 square feet, with a total engine
power of about 0.5 H. P., and having lifted 40 per cent of its weight on the
pendulum, was taken down the river for trial with the new railroad
launching apparatus, and several days were spent in erecting the launching
apparatus on the house-boat, and in launching “dummy” aerodromes from it
for practice.
Aerodrome No. 4 then being fitted under conditions which apparently
insured a good start (the center of pressure being nearly over the center of
gravity, the root angle of the wing being zero, the midrod nearly horizontal,
the engine working well, and with apparently ample sustaining surface) was
finally successfully launched, but the hopes which were reasonably
entertained proved to be unfounded. The result of this first actual trial of a
“flying machine” in free air was most disconcerting, for the aerodrome,
which had in theory many times the power required for horizontal flight,
plunged into the water with its engines working at full speed, after a course
hardly longer than that performed by the dummy. This result was at first
inexplicable.
No. 4, then, did not fly at all, from some at first inscrutable cause, and it
was decided to make a trial of No. 5, though it was hard to put the result of
so much [p098] time, painstaking and cost to the hazard of destruction. With
the experience just acquired from the trial of No. 4, the wing of No. 5 was
set at an angle of about 20° with the midrod, and the tip was secured by a
light cross-piece, so guyed that the wing as a whole, while set at this
considerably greater angle with the rod, was stiffer than before. In addition
to this, the air chamber was moved back so that the center of gravity was
from 6 to 10 cm. behind the (calculated) center of pressure. These changes
were made in order to insure that the front should at any rate keep up, and it
did.
The aerodrome was launched successfully with the engines working
under a pressure of 110 pounds of steam. The head rose continually until
successfully, but that a steady flame could be maintained under the boilers.
October 6. No. 4, as remodelled, having a flying weight of about 14.5
pounds, a supporting surface of about 28 square feet, with a total engine
power of about 0.5 H. P., and having lifted 40 per cent of its weight on the
pendulum, was taken down the river for trial with the new railroad
launching apparatus, and several days were spent in erecting the launching
apparatus on the house-boat, and in launching “dummy” aerodromes from it
for practice.
Aerodrome No. 4 then being fitted under conditions which apparently
insured a good start (the center of pressure being nearly over the center of
gravity, the root angle of the wing being zero, the midrod nearly horizontal,
the engine working well, and with apparently ample sustaining surface) was
finally successfully launched, but the hopes which were reasonably
entertained proved to be unfounded. The result of this first actual trial of a
“flying machine” in free air was most disconcerting, for the aerodrome,
which had in theory many times the power required for horizontal flight,
plunged into the water with its engines working at full speed, after a course
hardly longer than that performed by the dummy. This result was at first
inexplicable.
No. 4, then, did not fly at all, from some at first inscrutable cause, and it
was decided to make a trial of No. 5, though it was hard to put the result of
so much [p098] time, painstaking and cost to the hazard of destruction. With
the experience just acquired from the trial of No. 4, the wing of No. 5 was
set at an angle of about 20° with the midrod, and the tip was secured by a
light cross-piece, so guyed that the wing as a whole, while set at this
considerably greater angle with the rod, was stiffer than before. In addition
to this, the air chamber was moved back so that the center of gravity was
from 6 to 10 cm. behind the (calculated) center of pressure. These changes
were made in order to insure that the front should at any rate keep up, and it
did.
The aerodrome was launched successfully with the engines working
under a pressure of 110 pounds of steam. The head rose continually until
Page 167
the mid-rod stood up at an angle of about 60°, checking all further advance.
It remained in the air in a stationary position for nearly a second, and then
slid backward into the water, striking on the end of the rudder and bending
it. The distance flown was about 12 metres, and the time of flight 3 seconds.
One of the propellers was broken short off, and the shaft was bent.
It thus became clearly evident that some cause prevented the proper
balancing of the machine, which was necessary to secure even
approximately the theoretically simple condition of horizontal flight. It was
all-important that the angle of the front wing should be correct, but its
position could not be accurately known in advance of experiment, and this
experiment could only be made with the machine itself, and involved the
risk of wrecking it.
These trials gave a very vivid object lesson of what had already been
anticipated,31 that the difficulties of actual flight would probably lie even
more in obtaining exact balance than in the first and more obvious difficulty
of obtaining the mere engine power to sustain a machine in the air. The
immediate problem was to account for the totally different behavior of the
two aerodromes in the two flights, under not very different conditions.
Observations of the movement of the two aerodromes through the air, as
seen by the writer from the shore, seemed to show, however, that the wings
did not remain in their original form, but that at the moment of launching
there was a sudden flexure and distortion due to the upward pressure of the
air. The time of flight was too short, and the speed too great, to be sure of
just what did occur, but it seemed probable that the wings flexed under the
initial pressure of the weight which came upon them at the moment of
launching, and that they were in fact, while in the air, a wholly different
thing from what they were an instant before, so that a very slight initial
difference in the angle at which they first met the air might cause the air to
strike in the one case on the top of the wings and throw the head down, and
in the other case so as to throw the head up. To ascertain the extent and
character of this flexure, caused, it will be observed, by [p099] the weight of
the aerodrome suddenly thrown on the wings, I inverted the aerodrome and
distributed a weight of dry sand equal to that of the whole machine evenly
It remained in the air in a stationary position for nearly a second, and then
slid backward into the water, striking on the end of the rudder and bending
it. The distance flown was about 12 metres, and the time of flight 3 seconds.
One of the propellers was broken short off, and the shaft was bent.
It thus became clearly evident that some cause prevented the proper
balancing of the machine, which was necessary to secure even
approximately the theoretically simple condition of horizontal flight. It was
all-important that the angle of the front wing should be correct, but its
position could not be accurately known in advance of experiment, and this
experiment could only be made with the machine itself, and involved the
risk of wrecking it.
These trials gave a very vivid object lesson of what had already been
anticipated,31 that the difficulties of actual flight would probably lie even
more in obtaining exact balance than in the first and more obvious difficulty
of obtaining the mere engine power to sustain a machine in the air. The
immediate problem was to account for the totally different behavior of the
two aerodromes in the two flights, under not very different conditions.
Observations of the movement of the two aerodromes through the air, as
seen by the writer from the shore, seemed to show, however, that the wings
did not remain in their original form, but that at the moment of launching
there was a sudden flexure and distortion due to the upward pressure of the
air. The time of flight was too short, and the speed too great, to be sure of
just what did occur, but it seemed probable that the wings flexed under the
initial pressure of the weight which came upon them at the moment of
launching, and that they were in fact, while in the air, a wholly different
thing from what they were an instant before, so that a very slight initial
difference in the angle at which they first met the air might cause the air to
strike in the one case on the top of the wings and throw the head down, and
in the other case so as to throw the head up. To ascertain the extent and
character of this flexure, caused, it will be observed, by [p099] the weight of
the aerodrome suddenly thrown on the wings, I inverted the aerodrome and
distributed a weight of dry sand equal to that of the whole machine evenly
Page 168
over the supporting surfaces. It was found that under the weight of the sand
the extremity of the wings bent to an angle of 45° downwards (and
consequently must have bent to an angle of 45° upwards in the air), a
condition of affairs worse than anything that had been suspected, and
seeming to demand the entire reconstruction of the wings with a strength
and consequent weight for which there was no means of providing.
There had been some injuries to the machines in the trials of the 5th and
6th, and these were repaired. A new float had been made for No. 4, and a
new set of larger wings for No. 5. Each of these wings had a length of 76
inches and a breadth of 25 inches, making the total surface of the two 26.4
sq. ft., while that of the tail was 13.2 sq. ft., or about 40 sq. ft. in all.
October 22. When No. 5 was finally prepared for another trial, its
condition was as follows:
Flying weight 22 pounds
Area of supporting surfaces (wings and tail) 40 sq. ft.
Sq. ft. of surface per pound of weight 1.832
Engine power with 115 lbs. steam pressure 1.0 H. P.33
Power necessary to soar 0.35 H. P.
Theoretical soaring speed (plane wings at 20°) 24 ft. per sec.
Previous lift on pendulum 40 per cent of flying weight
October 25. The aerodromes having been taken to Quantico on October
23, and satisfactory experiments made with dummies in order to test the
launching apparatus, the house-boat was carried out into midstream and
moored.
Aerodrome No. 4 was launched in the face of a wind of about 1100 feet
per minute. The midrod was at a very small inclination with the horizontal,
about 3°. The angle (α) of the chord of the curved wing measured at the rod,
where it was rigidly held, was 15°. The adjustment was such as to bring the
CG immediately under the CP, without any allowance for the fact that the
line of propeller thrust was below the CP.34 The aerodrome under these
conditions was launched with the head high. It made a real, though brief,
flight of about 130 feet in 4 12 seconds, when it swung abruptly round
the extremity of the wings bent to an angle of 45° downwards (and
consequently must have bent to an angle of 45° upwards in the air), a
condition of affairs worse than anything that had been suspected, and
seeming to demand the entire reconstruction of the wings with a strength
and consequent weight for which there was no means of providing.
There had been some injuries to the machines in the trials of the 5th and
6th, and these were repaired. A new float had been made for No. 4, and a
new set of larger wings for No. 5. Each of these wings had a length of 76
inches and a breadth of 25 inches, making the total surface of the two 26.4
sq. ft., while that of the tail was 13.2 sq. ft., or about 40 sq. ft. in all.
October 22. When No. 5 was finally prepared for another trial, its
condition was as follows:
Flying weight 22 pounds
Area of supporting surfaces (wings and tail) 40 sq. ft.
Sq. ft. of surface per pound of weight 1.832
Engine power with 115 lbs. steam pressure 1.0 H. P.33
Power necessary to soar 0.35 H. P.
Theoretical soaring speed (plane wings at 20°) 24 ft. per sec.
Previous lift on pendulum 40 per cent of flying weight
October 25. The aerodromes having been taken to Quantico on October
23, and satisfactory experiments made with dummies in order to test the
launching apparatus, the house-boat was carried out into midstream and
moored.
Aerodrome No. 4 was launched in the face of a wind of about 1100 feet
per minute. The midrod was at a very small inclination with the horizontal,
about 3°. The angle (α) of the chord of the curved wing measured at the rod,
where it was rigidly held, was 15°. The adjustment was such as to bring the
CG immediately under the CP, without any allowance for the fact that the
line of propeller thrust was below the CP.34 The aerodrome under these
conditions was launched with the head high. It made a real, though brief,
flight of about 130 feet in 4 12 seconds, when it swung abruptly round
Page 169
through 90°, and, losing headway, sank continuously, finally falling
backward into the water.
October 27. Aerodrome No. 4, having been repaired and guyed with
wires from the wings to vertical guy-posts beneath, was launched again, but
one of the [p100] guy-wires caught on the launching car, and threw the
aerodrome immediately into the water with but little damage.
On the same day No. 5 was launched. The theoretical CP−CG was
nominally 0, but, for the reasons stated in the footnote on p. 99, was really
something positive, that is to say, the CP was really somewhat in advance
of the CG ; inclination of midrod less than α (=20°). The aerodrome under
these circumstances, while keeping its head up, at first fell rapidly, yet
seemed about to rise just as it struck the water, conveying the idea that if the
launching had been made with a greater initial velocity it would have risen
and cleared the water. The wings visibly pocketed, however, and it was
clear that some better disposition must still be made for them. The flight
was 3 12 seconds.
No. 5 was tried again on the same day with larger wings, whose area was
40 square feet. These wings, though stiffer, pocketed a little, α=20° as
before. It flew rapidly, and at first horizontally, to a distance of 100 feet or
more against a five-mile breeze. It then turned abruptly round through 180°,
at first falling (from loss of headway), then distinctly rising, and at the same
time throwing its head up until it reached an angle of nearly 60° with the
vertical, when it fell backward after a flight of between 6 and 7 seconds.
The wings were evidently not yet strong enough to resist flexure.
November 21. No. 5, in nearly the same condition as before. Two extra
springs had been placed on the launching car, in order to give the
aerodrome a greater initial velocity than before. Everything appeared
favorable, but as it left the launching track a piece flew out of the port
propeller, in spite of which the aerodrome, after dropping 5 feet, rose bodily
at an angle of 45° and fell backward into the water (time, 5 seconds).
Another trial was made the same day with the same aerodrome, under
similar conditions, except that the angle of inclination (α) was reduced to
backward into the water.
October 27. Aerodrome No. 4, having been repaired and guyed with
wires from the wings to vertical guy-posts beneath, was launched again, but
one of the [p100] guy-wires caught on the launching car, and threw the
aerodrome immediately into the water with but little damage.
On the same day No. 5 was launched. The theoretical CP−CG was
nominally 0, but, for the reasons stated in the footnote on p. 99, was really
something positive, that is to say, the CP was really somewhat in advance
of the CG ; inclination of midrod less than α (=20°). The aerodrome under
these circumstances, while keeping its head up, at first fell rapidly, yet
seemed about to rise just as it struck the water, conveying the idea that if the
launching had been made with a greater initial velocity it would have risen
and cleared the water. The wings visibly pocketed, however, and it was
clear that some better disposition must still be made for them. The flight
was 3 12 seconds.
No. 5 was tried again on the same day with larger wings, whose area was
40 square feet. These wings, though stiffer, pocketed a little, α=20° as
before. It flew rapidly, and at first horizontally, to a distance of 100 feet or
more against a five-mile breeze. It then turned abruptly round through 180°,
at first falling (from loss of headway), then distinctly rising, and at the same
time throwing its head up until it reached an angle of nearly 60° with the
vertical, when it fell backward after a flight of between 6 and 7 seconds.
The wings were evidently not yet strong enough to resist flexure.
November 21. No. 5, in nearly the same condition as before. Two extra
springs had been placed on the launching car, in order to give the
aerodrome a greater initial velocity than before. Everything appeared
favorable, but as it left the launching track a piece flew out of the port
propeller, in spite of which the aerodrome, after dropping 5 feet, rose bodily
at an angle of 45° and fell backward into the water (time, 5 seconds).
Another trial was made the same day with the same aerodrome, under
similar conditions, except that the angle of inclination (α) was reduced to
Page 170
7°. It now, with all the other circumstances of launching like those
immediately before, behaved entirely differently, plunging head downward
into the water at a distance of 30 feet. Once more it was shown beyond
dispute that the wings must somehow be made even stiffer.
December 8. Another trial was undertaken with No. 5, the CG being 10
cm. in front of the CP at rest. The root angle of the wings was 18°, tip angle
27°, elevation of midrod 1 in 24. The other changes made since the previous
trial consisted chiefly in the increased weight due to the longer and stronger
frames and shafts that were made to carry 100 cm. propellers. The flight
obtained was so short that it was as unsatisfactory as before.
The aerodrome rose in the air after leaving the launching apparatus, and
then slid back into the water in the plane of its own wings. On the first trial,
it struck the boat, and was slightly injured; on the second, with root angle of
[p101] wings 10°, tip angle 20°, the flight partook of the same character, but
the machine struck the water clear of the boat.
The fact that with the CG 10 cm. in advance of the calculated CP the
aerodrome steadily rose in front, seems to indicate that the rule used at that
time for calculating the CP (see Chapter II ◊) was not very accurate. This
rule was based upon the assumption that the tail, having an area equal to
one-third the entire sustaining surface, supported one-third the total weight
2CPwm + CPtm
(expressed by the formula CP = , where CPwm and CPtm
3
represent respectively the CP of the wings and tail in motion), and that the
CP of each surface was one-fifth its width in front of the center of figure.
December 12. Four days later, the tail had been moved back 21 cm., thus
carrying the CG back 7 cm., but the vertical rudder (weighing 105
grammes), for which there was now no room, was taken off, which in a
measure counteracted this change.
A trial was then made with the wings set at an initial angle of 8° at the
root and 20° at the tip. The aerodrome was released with the engines
working under a steam pressure of 90 pounds, and soared off horizontally
for some distance, when suddenly it swerved to the right as though
something on that side had given out, and turning quite through 180°
immediately before, behaved entirely differently, plunging head downward
into the water at a distance of 30 feet. Once more it was shown beyond
dispute that the wings must somehow be made even stiffer.
December 8. Another trial was undertaken with No. 5, the CG being 10
cm. in front of the CP at rest. The root angle of the wings was 18°, tip angle
27°, elevation of midrod 1 in 24. The other changes made since the previous
trial consisted chiefly in the increased weight due to the longer and stronger
frames and shafts that were made to carry 100 cm. propellers. The flight
obtained was so short that it was as unsatisfactory as before.
The aerodrome rose in the air after leaving the launching apparatus, and
then slid back into the water in the plane of its own wings. On the first trial,
it struck the boat, and was slightly injured; on the second, with root angle of
[p101] wings 10°, tip angle 20°, the flight partook of the same character, but
the machine struck the water clear of the boat.
The fact that with the CG 10 cm. in advance of the calculated CP the
aerodrome steadily rose in front, seems to indicate that the rule used at that
time for calculating the CP (see Chapter II ◊) was not very accurate. This
rule was based upon the assumption that the tail, having an area equal to
one-third the entire sustaining surface, supported one-third the total weight
2CPwm + CPtm
(expressed by the formula CP = , where CPwm and CPtm
3
represent respectively the CP of the wings and tail in motion), and that the
CP of each surface was one-fifth its width in front of the center of figure.
December 12. Four days later, the tail had been moved back 21 cm., thus
carrying the CG back 7 cm., but the vertical rudder (weighing 105
grammes), for which there was now no room, was taken off, which in a
measure counteracted this change.
A trial was then made with the wings set at an initial angle of 8° at the
root and 20° at the tip. The aerodrome was released with the engines
working under a steam pressure of 90 pounds, and soared off horizontally
for some distance, when suddenly it swerved to the right as though
something on that side had given out, and turning quite through 180°
Page 171
headed toward the boat, striking the water about 76 feet away. The time of
the flight was 4 seconds.
It was found upon the recovery of the machine that one of the propellers
had been twisted through 90°, so that the two were no longer symmetrical.
The turning may have been due to this twist or to unequal influence of the
wind upon the two wings; for when I applied the sand test to the wings after
returning them to Washington, it was found that they deflected so much that
the grains would not lie upon them, which, to a great extent, explains the
failure to secure a better flight.
Thus the end of another year had been reached, and what might be called
a real flight had not yet been secured. The only progress that seemed to
have been made was that the aerodromes were not quite so unmanageable
and erratic in their flights as at the beginning of the year, and that it had
been demonstrated, at least to the writer’s satisfaction, that the power was
sufficient for the work to be done. The launching device had been so
perfected that it worked satisfactorily, but the problem of balancing seemed
as far from solution as before.
189 5
While, for convenience in narrating the progress of the work with the
aerodromes, each year has been treated as a unit, it is, of course, understood
that the work itself shows no especial difference between the closing of one
year and the beginning of another. Changes which had important effects
were introduced [p102] at various times, but were, of course, made as they
suggested themselves without any reference to time or season. But while it
was customary to make, from time to time, a résumé of the progress of the
work, yet at the closing of the calendar year it was the custom to make a
more complete digest of just what had been accomplished during the year.
Upon thus reviewing the progress of the work during 1894, it was felt
that the results which had been accomplished for such a large expenditure
of time seemed small, since no real flight had been made by any of the
aerodromes, and no definite assurance that a successful flight would be
obtained within the immediate future seemed warranted by what had
the flight was 4 seconds.
It was found upon the recovery of the machine that one of the propellers
had been twisted through 90°, so that the two were no longer symmetrical.
The turning may have been due to this twist or to unequal influence of the
wind upon the two wings; for when I applied the sand test to the wings after
returning them to Washington, it was found that they deflected so much that
the grains would not lie upon them, which, to a great extent, explains the
failure to secure a better flight.
Thus the end of another year had been reached, and what might be called
a real flight had not yet been secured. The only progress that seemed to
have been made was that the aerodromes were not quite so unmanageable
and erratic in their flights as at the beginning of the year, and that it had
been demonstrated, at least to the writer’s satisfaction, that the power was
sufficient for the work to be done. The launching device had been so
perfected that it worked satisfactorily, but the problem of balancing seemed
as far from solution as before.
189 5
While, for convenience in narrating the progress of the work with the
aerodromes, each year has been treated as a unit, it is, of course, understood
that the work itself shows no especial difference between the closing of one
year and the beginning of another. Changes which had important effects
were introduced [p102] at various times, but were, of course, made as they
suggested themselves without any reference to time or season. But while it
was customary to make, from time to time, a résumé of the progress of the
work, yet at the closing of the calendar year it was the custom to make a
more complete digest of just what had been accomplished during the year.
Upon thus reviewing the progress of the work during 1894, it was felt
that the results which had been accomplished for such a large expenditure
of time seemed small, since no real flight had been made by any of the
aerodromes, and no definite assurance that a successful flight would be
obtained within the immediate future seemed warranted by what had
Page 172
already been accomplished. But now that the principal difficulties
connected with the launching apparatus had been overcome, thus permitting
the aerodromes themselves to be given a fair trial, the belief was
encouraged that the continuance of the actual tests of the machines, with
slight changes which previous tests had shown advisable, would finally
result in a successful flight.
The early weeks of 1895 were spent in a series of pendulum tests on No.
5, and in making such slight changes as these tests indicated would be
advisable. As a result of small improvements introduced in the boilers, No.
5 had by the middle of March shown a repeated lift of considerably over 50
per cent, and in some tests as much as 62 per cent of its flying weight.
Certain radical changes previously described in Chapter VII ◊ were also
made in Aerodrome No. 4, and in the pendulum tests of it a lift of 44 per
cent of its flying weight had been obtained.
Encouraged by the better results which the aerodromes had shown in the
above tests, it was decided to test them again in free flight, and they were
accordingly sent down to Quantico in charge of the two mechanics, R and
M, Mr. Langley, accompanied by Dr. Graham Bell, whom he had invited to
witness the tests, following on May 8. On the evening of May 8 No. 5 was
mounted on the launching apparatus in order to drill the mechanics so that
when favorable weather presented itself the aerodrome could be got ready
for launching with the minimum delay.
On May 9 Mr. Langley and Dr. Bell reached the house-boat at 5 a. m.,
but even with the drill of the previous evening the mechanics were not able
to have No. 5 ready for trial until 6.15 a. m. The principal conditions of No.
5 at this time were:
Total weight 11,200 grammes (24.6 pounds), including 800 grammes of fuel and water. Previous
lift on the pendulum 54 per cent, with a steam pressure of 150 pounds. With this steam pressure the
engine made about 600 R. P. M. when driving the 95 cm. propellers, which through their reduction
gearing made about 500 R. P. M. [p103]
When the aerodrome was balanced for flight so as to bring the theoretical
“center of pressure in motion” over the center of gravity, it was found that it
was not possible to carry the center of gravity in front of this point,
connected with the launching apparatus had been overcome, thus permitting
the aerodromes themselves to be given a fair trial, the belief was
encouraged that the continuance of the actual tests of the machines, with
slight changes which previous tests had shown advisable, would finally
result in a successful flight.
The early weeks of 1895 were spent in a series of pendulum tests on No.
5, and in making such slight changes as these tests indicated would be
advisable. As a result of small improvements introduced in the boilers, No.
5 had by the middle of March shown a repeated lift of considerably over 50
per cent, and in some tests as much as 62 per cent of its flying weight.
Certain radical changes previously described in Chapter VII ◊ were also
made in Aerodrome No. 4, and in the pendulum tests of it a lift of 44 per
cent of its flying weight had been obtained.
Encouraged by the better results which the aerodromes had shown in the
above tests, it was decided to test them again in free flight, and they were
accordingly sent down to Quantico in charge of the two mechanics, R and
M, Mr. Langley, accompanied by Dr. Graham Bell, whom he had invited to
witness the tests, following on May 8. On the evening of May 8 No. 5 was
mounted on the launching apparatus in order to drill the mechanics so that
when favorable weather presented itself the aerodrome could be got ready
for launching with the minimum delay.
On May 9 Mr. Langley and Dr. Bell reached the house-boat at 5 a. m.,
but even with the drill of the previous evening the mechanics were not able
to have No. 5 ready for trial until 6.15 a. m. The principal conditions of No.
5 at this time were:
Total weight 11,200 grammes (24.6 pounds), including 800 grammes of fuel and water. Previous
lift on the pendulum 54 per cent, with a steam pressure of 150 pounds. With this steam pressure the
engine made about 600 R. P. M. when driving the 95 cm. propellers, which through their reduction
gearing made about 500 R. P. M. [p103]
When the aerodrome was balanced for flight so as to bring the theoretical
“center of pressure in motion” over the center of gravity, it was found that it
was not possible to carry the center of gravity in front of this point,
Page 173
although it was known by experience to be necessary. Accordingly in the
first trial the outer ends of the tail were pressed down by the guys so that
the wind of advance tended to lift the tail and throw the head down more
than if the tail had been flat. Furthermore, the float, weighing 200 grammes,
instead of being placed in its normal position near the base of the bowsprit,
was carried out to its extremity, this change in the position of the float alone
being sufficient to carry the center of gravity forward three or four
centimetres. The curved wings were set at an angle of nine degrees at the
root and eleven degrees at the tip. They were well guyed, and in flight
appeared to be not materially twisted or altered.
It was anticipated that the pressing down of the outer ends of the tail and
the shifting of the center of gravity would cause the aerodrome to point
downward in flight, and this anticipation was verified in the test. At 6.15 a.
m. the aerodrome was launched at a steam pressure of 120 pounds. A
perfect calm prevailed at the time and the machine started straight ahead.
There was no perceptible drop at the moment it was released from the
launching car, but a smooth and steady descent until it struck the water,
nose down, at a point approximately 200 feet from the boat. Dr. Bell noted
that the length of time the aerodrome was in the air was 2.8 seconds. One of
the propellers was broken and the other one was found to have twisted its
shaft one-fourth of a turn.
At 9.45 a. m., the wings having been dried, No. 5 was again tried. The
float was moved back to its normal position at the base of the bowsprit, and
the guys, by which the outer ends of the tail had been depressed in the
previous trial, were so adjusted that the tail was flat. The machine was,
therefore, in the condition of theoretical equilibrium for rapid motion with a
plane wing. All the other conditions were precisely as in the previous trial,
except that the round-end 100-centimetre propellers were substituted for the
95-centimetre ones which had been broken, and a new paper-covered tail
was used. The mechanic in charge was directed to let the steam reach its
highest pressure consistent with a flight of one-half a minute, before
launching the machine, but he seemed to have lost all sense of the length of
time the fuel and water would last, as he let the engines run until almost the
first trial the outer ends of the tail were pressed down by the guys so that
the wind of advance tended to lift the tail and throw the head down more
than if the tail had been flat. Furthermore, the float, weighing 200 grammes,
instead of being placed in its normal position near the base of the bowsprit,
was carried out to its extremity, this change in the position of the float alone
being sufficient to carry the center of gravity forward three or four
centimetres. The curved wings were set at an angle of nine degrees at the
root and eleven degrees at the tip. They were well guyed, and in flight
appeared to be not materially twisted or altered.
It was anticipated that the pressing down of the outer ends of the tail and
the shifting of the center of gravity would cause the aerodrome to point
downward in flight, and this anticipation was verified in the test. At 6.15 a.
m. the aerodrome was launched at a steam pressure of 120 pounds. A
perfect calm prevailed at the time and the machine started straight ahead.
There was no perceptible drop at the moment it was released from the
launching car, but a smooth and steady descent until it struck the water,
nose down, at a point approximately 200 feet from the boat. Dr. Bell noted
that the length of time the aerodrome was in the air was 2.8 seconds. One of
the propellers was broken and the other one was found to have twisted its
shaft one-fourth of a turn.
At 9.45 a. m., the wings having been dried, No. 5 was again tried. The
float was moved back to its normal position at the base of the bowsprit, and
the guys, by which the outer ends of the tail had been depressed in the
previous trial, were so adjusted that the tail was flat. The machine was,
therefore, in the condition of theoretical equilibrium for rapid motion with a
plane wing. All the other conditions were precisely as in the previous trial,
except that the round-end 100-centimetre propellers were substituted for the
95-centimetre ones which had been broken, and a new paper-covered tail
was used. The mechanic in charge was directed to let the steam reach its
highest pressure consistent with a flight of one-half a minute, before
launching the machine, but he seemed to have lost all sense of the length of
time the fuel and water would last, as he let the engines run until almost the
Page 174
whole charge was exhausted before launching it. The aerodrome went off
almost horizontally, then turned up into the wind and rose to an angle of
about twenty degrees; then (while moving forward) slowly sank as though
the engine power had given out, as in fact it doubtless had. The actual
distance travelled was 123 feet and the length of time 7.2 seconds. While
the exhaustion of the fuel and water prior to launching the machine had
prevented what apparently would otherwise have been an [p104] exceedingly
good flight, yet the fact that the aerodrome rose immediately after being
launched, and continued to do so until the power gave out, was in itself very
encouraging.
At 1.40 p. m. No. 5 was again ready for trial (the third one for the day),
and this time Mr. Langley and Dr. Bell witnessed it from a greater distance
in hopes of being able more clearly to study its behavior when actually in
the air.
The previous trial having missed success through the fuel and water
having been consumed before the machine was launched, special
instructions were given to avoid the recurrence of this mistake. But the
machine was held for probably two minutes after the burners were lighted,
with very much the same result as before. The conditions of the aerodrome
were the same as in the previous trial, except that the tail was a little flatter,
so as to tend to make the head slightly lower in flight. It was launched at an
angle of about thirty degrees with the very gentle wind that was blowing,
and, apparently under the direction of the rudder, turned into the wind, the
midrod rising to an angle of about twenty degrees and (as noted in Mr.
Langley’s record book) “The whole machine absolutely rising during five
or six seconds—a fine spectacle! Then the power visibly gave out, the
propellers revolving slower. It settled forward and lost nearly all of its
forward motion at the end of about seven seconds, but did not finally touch
the water until ten and a quarter seconds.”
While the length of time that the aerodrome had been sustained in the air
was so short that no actual flight had really been achieved, yet the results
encouraged the belief that with the aerodrome more accurately balanced, it
could reasonably be hoped that a somewhat longer flight would be
almost horizontally, then turned up into the wind and rose to an angle of
about twenty degrees; then (while moving forward) slowly sank as though
the engine power had given out, as in fact it doubtless had. The actual
distance travelled was 123 feet and the length of time 7.2 seconds. While
the exhaustion of the fuel and water prior to launching the machine had
prevented what apparently would otherwise have been an [p104] exceedingly
good flight, yet the fact that the aerodrome rose immediately after being
launched, and continued to do so until the power gave out, was in itself very
encouraging.
At 1.40 p. m. No. 5 was again ready for trial (the third one for the day),
and this time Mr. Langley and Dr. Bell witnessed it from a greater distance
in hopes of being able more clearly to study its behavior when actually in
the air.
The previous trial having missed success through the fuel and water
having been consumed before the machine was launched, special
instructions were given to avoid the recurrence of this mistake. But the
machine was held for probably two minutes after the burners were lighted,
with very much the same result as before. The conditions of the aerodrome
were the same as in the previous trial, except that the tail was a little flatter,
so as to tend to make the head slightly lower in flight. It was launched at an
angle of about thirty degrees with the very gentle wind that was blowing,
and, apparently under the direction of the rudder, turned into the wind, the
midrod rising to an angle of about twenty degrees and (as noted in Mr.
Langley’s record book) “The whole machine absolutely rising during five
or six seconds—a fine spectacle! Then the power visibly gave out, the
propellers revolving slower. It settled forward and lost nearly all of its
forward motion at the end of about seven seconds, but did not finally touch
the water until ten and a quarter seconds.”
While the length of time that the aerodrome had been sustained in the air
was so short that no actual flight had really been achieved, yet the results
encouraged the belief that with the aerodrome more accurately balanced, it
could reasonably be hoped that a somewhat longer flight would be
Page 175
obtained. It was, however, very evident that, although the correct balancing
which would insure equilibrium for a few minutes might soon be attained,
the machine, lacking a human intelligence to control it, must be provided
with some mechanism which would tend to restore the equilibrium, the
conditions of which must necessarily change in a machine depending on the
air for its support. In order to see what could be done in this direction, it
was, therefore, decided to return immediately to Washington with the
machines and make some minor changes in them before attempting further
flights.
By the end of May, Nos. 4 and 5 were again in readiness for a trial, and
the mechanics were accordingly sent to Quantico to complete preparations
for the tests. During May Mr. A. M. Herring, who had been experimenting
with model machines for several years, was engaged for a few months as an
assistant, and he was immediately put in charge of the field trials of Nos. 4
and 5, which were now about to be made. On June 6 Mr. Langley,
accompanied by Mr. Herring, went to Quantico, and on June 7, at 5 a. m.,
Aerodrome No. 5 was ready for trial, but the wind was so high that nothing
could be done. The wind later diminished in intensity, but the house-boat
had become stuck on the beach [p105] and it was impossible to make the
launching apparatus point directly into the wind, which was blowing from
the rear of the boat. An attempt was made to launch the aerodrome even
with the wind blowing at its rear, but it was found impossible to make the
fires burn and the test was accordingly postponed. Later in the afternoon the
house-boat was floated and the preparations for a test were immediately
completed. At 5.42 p. m. the fires were lighted, but the burners did not work
properly and the proper steam pressure could not be obtained. At 6.20 p. m.
the fires were again lighted, and at 6.22 the aerodrome was launched, its
midrod having an upward angle of 25 degrees, or more, with the launching
track. The aerodrome moved off nearly horizontally, but seemed to be very
sluggish in its movement and fell in the water about seventy feet from the
boat, after having been in the air only 4.8 seconds. The damage consisted of
a broken propeller and a slight strain in the main frame, the extent of which,
however, was not immediately seen.
which would insure equilibrium for a few minutes might soon be attained,
the machine, lacking a human intelligence to control it, must be provided
with some mechanism which would tend to restore the equilibrium, the
conditions of which must necessarily change in a machine depending on the
air for its support. In order to see what could be done in this direction, it
was, therefore, decided to return immediately to Washington with the
machines and make some minor changes in them before attempting further
flights.
By the end of May, Nos. 4 and 5 were again in readiness for a trial, and
the mechanics were accordingly sent to Quantico to complete preparations
for the tests. During May Mr. A. M. Herring, who had been experimenting
with model machines for several years, was engaged for a few months as an
assistant, and he was immediately put in charge of the field trials of Nos. 4
and 5, which were now about to be made. On June 6 Mr. Langley,
accompanied by Mr. Herring, went to Quantico, and on June 7, at 5 a. m.,
Aerodrome No. 5 was ready for trial, but the wind was so high that nothing
could be done. The wind later diminished in intensity, but the house-boat
had become stuck on the beach [p105] and it was impossible to make the
launching apparatus point directly into the wind, which was blowing from
the rear of the boat. An attempt was made to launch the aerodrome even
with the wind blowing at its rear, but it was found impossible to make the
fires burn and the test was accordingly postponed. Later in the afternoon the
house-boat was floated and the preparations for a test were immediately
completed. At 5.42 p. m. the fires were lighted, but the burners did not work
properly and the proper steam pressure could not be obtained. At 6.20 p. m.
the fires were again lighted, and at 6.22 the aerodrome was launched, its
midrod having an upward angle of 25 degrees, or more, with the launching
track. The aerodrome moved off nearly horizontally, but seemed to be very
sluggish in its movement and fell in the water about seventy feet from the
boat, after having been in the air only 4.8 seconds. The damage consisted of
a broken propeller and a slight strain in the main frame, the extent of which,
however, was not immediately seen.
Page 176
The steam pressure at the time of launching was 110 pounds, which was
obviously insufficient. The aerodrome had lifted fifty per cent of its weight
on the pendulum, and its sluggishness of movement seemed, therefore,
unaccountable even for this pressure. It seemed probable, however, that the
pressure ran down immediately after the machine was launched, on account
either of the use of the light-weight burners in place of the larger and
heavier ones, or of the diminution of the air pressure in the gas tank.
At 7.55 the aerodrome was again launched, and this time made a still
shorter flight than before, being in the air only three seconds. A serious leak
in the engine cylinder was, however, discovered just as the machine was
launched, and this probably accounted for the lack of power.
Not only had the tests which have just been described indicated that there
was a lack of power during flight, although previous pendulum tests had
repeatedly shown lifts greater than fifty per cent, but, furthermore, the
wings themselves, while appearing perfectly capable of supporting the
aerodrome when viewed with the machine stationary, were seen to flex to
such an extent in flight that it seemed probable that much of the power was
consumed in merely overcoming the head resistance of a large portion of
the wings which had lost all lifting effect.
During the fall and winter, as recorded in Chapters VII and VIII ◊,
Aerodrome “New No. 4,” which had been reconstructed during the summer,
and which upon test was found radically weak, was almost entirely rebuilt
and afterwards known as No. 6. Important changes were also made in No.
5, which greatly increased its strength and power. The improvements,
however, which contributed more than anything else to the marked success
achieved in the next trial of the aerodromes, were those which had to do
with the nature and disposition of the sustaining surfaces and the means for
securing equilibrium. [p106]
It will be recalled that in the more recent trials the apparent causes of
failure had been the inability to provide sufficiently rigid wings, the great
difficulty of properly adjusting the relative positions of the centers of
pressure and gravity, and the lack of any means of regaining equilibrium
when the balance of the aerodrome had in any way been disturbed. In the
obviously insufficient. The aerodrome had lifted fifty per cent of its weight
on the pendulum, and its sluggishness of movement seemed, therefore,
unaccountable even for this pressure. It seemed probable, however, that the
pressure ran down immediately after the machine was launched, on account
either of the use of the light-weight burners in place of the larger and
heavier ones, or of the diminution of the air pressure in the gas tank.
At 7.55 the aerodrome was again launched, and this time made a still
shorter flight than before, being in the air only three seconds. A serious leak
in the engine cylinder was, however, discovered just as the machine was
launched, and this probably accounted for the lack of power.
Not only had the tests which have just been described indicated that there
was a lack of power during flight, although previous pendulum tests had
repeatedly shown lifts greater than fifty per cent, but, furthermore, the
wings themselves, while appearing perfectly capable of supporting the
aerodrome when viewed with the machine stationary, were seen to flex to
such an extent in flight that it seemed probable that much of the power was
consumed in merely overcoming the head resistance of a large portion of
the wings which had lost all lifting effect.
During the fall and winter, as recorded in Chapters VII and VIII ◊,
Aerodrome “New No. 4,” which had been reconstructed during the summer,
and which upon test was found radically weak, was almost entirely rebuilt
and afterwards known as No. 6. Important changes were also made in No.
5, which greatly increased its strength and power. The improvements,
however, which contributed more than anything else to the marked success
achieved in the next trial of the aerodromes, were those which had to do
with the nature and disposition of the sustaining surfaces and the means for
securing equilibrium. [p106]
It will be recalled that in the more recent trials the apparent causes of
failure had been the inability to provide sufficiently rigid wings, the great
difficulty of properly adjusting the relative positions of the centers of
pressure and gravity, and the lack of any means of regaining equilibrium
when the balance of the aerodrome had in any way been disturbed. In the
Page 177
fall of 1895, accordingly, it was finally decided to employ a second pair of
wings equal in size to the first or leading pair. This not only added greatly to
the stability of the aerodrome, but also made it possible, without any
alteration in the plan of the frame, to bring the center of pressure into the
proper position relative to the center of gravity. In addition the plan of
constructing the wings was modified by the introduction of a second main
rib, which, placed at approximately the center of pressure of the wings,
made them much stiffer, both against bending and torsion. The two pairs of
wings now became the sole means of support, and the tail which had
hitherto been made to bear part of the weight of the aerodrome, as well as
assist in preserving the longitudinal equilibrium, was now intended to
perform only the latter function. It was placed in the rear of the wings and
was combined with the vertical rudder. Further, in adjusting it on the
aerodrome, it was set at a small negative angle and given a certain degree of
elasticity, as described above. This device proved to be a most efficient
means of maintaining and restoring the equilibrium, when it was disturbed,
and its value was apparent in all future tests of the models.
189 6
The important changes in the steam-driven models which had been begun
in the previous fall, and which in the case of No. 4 had been so extensive as
to convert it into a new aerodrome, No. 6, were continued during the early
spring, and it was not until the last of April that the models Nos. 5 and 6
were ready for actual test in free flight.
wings equal in size to the first or leading pair. This not only added greatly to
the stability of the aerodrome, but also made it possible, without any
alteration in the plan of the frame, to bring the center of pressure into the
proper position relative to the center of gravity. In addition the plan of
constructing the wings was modified by the introduction of a second main
rib, which, placed at approximately the center of pressure of the wings,
made them much stiffer, both against bending and torsion. The two pairs of
wings now became the sole means of support, and the tail which had
hitherto been made to bear part of the weight of the aerodrome, as well as
assist in preserving the longitudinal equilibrium, was now intended to
perform only the latter function. It was placed in the rear of the wings and
was combined with the vertical rudder. Further, in adjusting it on the
aerodrome, it was set at a small negative angle and given a certain degree of
elasticity, as described above. This device proved to be a most efficient
means of maintaining and restoring the equilibrium, when it was disturbed,
and its value was apparent in all future tests of the models.
189 6
The important changes in the steam-driven models which had been begun
in the previous fall, and which in the case of No. 4 had been so extensive as
to convert it into a new aerodrome, No. 6, were continued during the early
spring, and it was not until the last of April that the models Nos. 5 and 6
were ready for actual test in free flight.
Page 178
PL. 18. HOUSE-BOAT WITH OVERHEAD LAUNCHING APPARATUS, 1896 ◊
Page 179
The condition of No. 5, which made the first successful flight, is given in
the data sheet for May 6, 1896, and its general form at this time may be
seen in the photograph of May 11, Plate 27A. Although the changes
described above, as well as the modifications in the boilers and burners of
both aerodromes had undoubtedly effected a great improvement in every
detail of the machines, the disappointments experienced in the preceding
years prevented any great feeling of confidence that the trials which were
now to be made would be entirely successful. On May 4, however, the two
mechanics, Mr. Reed and Mr. Maltby, were sent down to Quantico with
Aerodromes Nos. 5 and 6, and Mr. Langley, accompanied by Dr. Graham
Bell, who had been invited to witness the tests, followed on the afternoon of
the 5th. On May 6 the wind was so very high all the morning that a test was
found impracticable. During the forenoon, however, the wind gradually
died down, and by 1 p. m. was blowing from six to ten miles an hour [p107]
from the northeast. At 1.10 p. m. Aerodrome No. 6 was launched, but the
guy-wire uniting the wings having apparently caught on one of the fixed
wooden strips which held the wings down, the left wing was broken before
the aerodrome was really launched, and the result was that the machine
slowly settled down in the water by the boat, breaking the propellers and
slightly injuring the Pénaud tail.
After removing No. 6 from the water, No. 5 was placed on the launching
car and immediately prepared for a test. At 3.05 p. m. it was launched at a
steam pressure of 150 pounds and started directly ahead into the gentle
breeze which was then blowing. The height of the launching track above the
water was about twenty feet. Immediately after leaving the launching track,
the aerodrome slowly descended three or four feet, but immediately began
to rise, its midrod pointing upward at an increasing angle until it made
about ten degrees with the horizon and then remained remarkably constant
at this angle through the flight. Shortly after leaving the launching track the
aerodrome began to circle to the right and moved around with great
steadiness, traversing a spiral path, as shown in the diagram (Plate 19).
From an inspection of the diagram it will be noticed that the aerodrome
made two complete turns and started on the third one. During the first two
the data sheet for May 6, 1896, and its general form at this time may be
seen in the photograph of May 11, Plate 27A. Although the changes
described above, as well as the modifications in the boilers and burners of
both aerodromes had undoubtedly effected a great improvement in every
detail of the machines, the disappointments experienced in the preceding
years prevented any great feeling of confidence that the trials which were
now to be made would be entirely successful. On May 4, however, the two
mechanics, Mr. Reed and Mr. Maltby, were sent down to Quantico with
Aerodromes Nos. 5 and 6, and Mr. Langley, accompanied by Dr. Graham
Bell, who had been invited to witness the tests, followed on the afternoon of
the 5th. On May 6 the wind was so very high all the morning that a test was
found impracticable. During the forenoon, however, the wind gradually
died down, and by 1 p. m. was blowing from six to ten miles an hour [p107]
from the northeast. At 1.10 p. m. Aerodrome No. 6 was launched, but the
guy-wire uniting the wings having apparently caught on one of the fixed
wooden strips which held the wings down, the left wing was broken before
the aerodrome was really launched, and the result was that the machine
slowly settled down in the water by the boat, breaking the propellers and
slightly injuring the Pénaud tail.
After removing No. 6 from the water, No. 5 was placed on the launching
car and immediately prepared for a test. At 3.05 p. m. it was launched at a
steam pressure of 150 pounds and started directly ahead into the gentle
breeze which was then blowing. The height of the launching track above the
water was about twenty feet. Immediately after leaving the launching track,
the aerodrome slowly descended three or four feet, but immediately began
to rise, its midrod pointing upward at an increasing angle until it made
about ten degrees with the horizon and then remained remarkably constant
at this angle through the flight. Shortly after leaving the launching track the
aerodrome began to circle to the right and moved around with great
steadiness, traversing a spiral path, as shown in the diagram (Plate 19).
From an inspection of the diagram it will be noticed that the aerodrome
made two complete turns and started on the third one. During the first two
Page 180
turns the machine was constantly and steadily ascending, and at the end of
the second turn it had reached a height variously estimated by the different
observers at from 70 to 100 feet. When at this height, and after the lapse of
one minute and twenty seconds, the propellers were seen to be moving
perceptibly slower and the machine began to descend slowly, at the same
time moving forward and changing the angle of inclination of the midrod
until the bow pointed slightly downward. It finally touched the water to the
south of the house-boat at the position shown, the time the machine was in
the air having been one minute and thirty seconds from the moment of
launching. The distance actually traversed, as estimated by plotting its
curved path on the coast-survey chart and then measuring this path, was
approximately 3300 feet, which is the mean of three independent estimates.
This estimate of the distance was checked by noting the number of
revolutions of the propellers as recorded by the revolution counter, which
was set in motion at the moment the machine was launched. On the
assumption that the slip of the propellers was not greater than fifty per cent,
the 1166 revolutions as shown by the counter would indicate a distance
travelled of 2430 feet. As it was felt very certain that the slip of the
propellers could not have amounted to as much as fifty per cent, it seemed a
conservative estimate to place the length of flight at 3000 feet, which would
mean a rate of travel of between 20 and 25 miles an hour. The circular path
traversed by the aerodrome was accounted for by the fact that the guy-wires
on one of the wings had not been tightened up properly, thus causing a
difference in the lifting effect of the two sides. [p108]
The aerodrome was immediately recovered from the water and
preparations made for a second test, the machine being launched again at
5.10 p. m. at a steam pressure of 160 pounds. The conditions were the same
as at the first trial, except that the wind had changed from north to south
and was perhaps of less velocity than before. The path traversed by the
aerodrome in this second trial was almost a duplicate of the previous one,
except that on account of the change in the direction of the wind the
machine was launched in the opposite direction. In tightening up the guy-
wires, which had not been properly adjusted in the previous test, they were
the second turn it had reached a height variously estimated by the different
observers at from 70 to 100 feet. When at this height, and after the lapse of
one minute and twenty seconds, the propellers were seen to be moving
perceptibly slower and the machine began to descend slowly, at the same
time moving forward and changing the angle of inclination of the midrod
until the bow pointed slightly downward. It finally touched the water to the
south of the house-boat at the position shown, the time the machine was in
the air having been one minute and thirty seconds from the moment of
launching. The distance actually traversed, as estimated by plotting its
curved path on the coast-survey chart and then measuring this path, was
approximately 3300 feet, which is the mean of three independent estimates.
This estimate of the distance was checked by noting the number of
revolutions of the propellers as recorded by the revolution counter, which
was set in motion at the moment the machine was launched. On the
assumption that the slip of the propellers was not greater than fifty per cent,
the 1166 revolutions as shown by the counter would indicate a distance
travelled of 2430 feet. As it was felt very certain that the slip of the
propellers could not have amounted to as much as fifty per cent, it seemed a
conservative estimate to place the length of flight at 3000 feet, which would
mean a rate of travel of between 20 and 25 miles an hour. The circular path
traversed by the aerodrome was accounted for by the fact that the guy-wires
on one of the wings had not been tightened up properly, thus causing a
difference in the lifting effect of the two sides. [p108]
The aerodrome was immediately recovered from the water and
preparations made for a second test, the machine being launched again at
5.10 p. m. at a steam pressure of 160 pounds. The conditions were the same
as at the first trial, except that the wind had changed from north to south
and was perhaps of less velocity than before. The path traversed by the
aerodrome in this second trial was almost a duplicate of the previous one,
except that on account of the change in the direction of the wind the
machine was launched in the opposite direction. In tightening up the guy-
wires, which had not been properly adjusted in the previous test, they were
Page 181
probably tightened somewhat too much, since in this second test the
aerodrome circled towards the left, whereas in the first flight it had circled
towards the right. The aerodrome made three complete turns, rising to a
height of approximately sixty feet with its midrod inclined to the horizon at
a slightly greater angle than before. The propellers again ceased turning
while the machine was high in the air and it glided forward and downward
and finally settled on the water after having been in the air one minute and
thirty-one seconds. The distance travelled was estimated as before, by
plotting the path on the coast-survey chart, and was found to be 2300 feet.
During these flights several photographs were secured of the machine
while it was actually in the air, some of the pictures being taken by Dr. Bell
and others by Mr. F. E. Fowle. The clearest of these are shown in Plates 20,
21, and 22.
Just what these flights meant to Mr. Langley can be readily understood.
They meant success! For the first time in the history of the world a device
produced by man had actually flown through the air, and had preserved its
equilibrium without the aid of a guiding human intelligence. Not only had
this device flown, but it had been given a second trial and had again flown
and had demonstrated that the result obtained in the first test was no mere
accident.
Shortly after returning to Washington, Mr. Langley left for Europe, but
before doing so he gave instructions to the workmen to remedy the small
weaknesses and defects which had been found in Aerodrome No. 6, and to
have both aerodromes ready for trial before his return in the fall.
aerodrome circled towards the left, whereas in the first flight it had circled
towards the right. The aerodrome made three complete turns, rising to a
height of approximately sixty feet with its midrod inclined to the horizon at
a slightly greater angle than before. The propellers again ceased turning
while the machine was high in the air and it glided forward and downward
and finally settled on the water after having been in the air one minute and
thirty-one seconds. The distance travelled was estimated as before, by
plotting the path on the coast-survey chart, and was found to be 2300 feet.
During these flights several photographs were secured of the machine
while it was actually in the air, some of the pictures being taken by Dr. Bell
and others by Mr. F. E. Fowle. The clearest of these are shown in Plates 20,
21, and 22.
Just what these flights meant to Mr. Langley can be readily understood.
They meant success! For the first time in the history of the world a device
produced by man had actually flown through the air, and had preserved its
equilibrium without the aid of a guiding human intelligence. Not only had
this device flown, but it had been given a second trial and had again flown
and had demonstrated that the result obtained in the first test was no mere
accident.
Shortly after returning to Washington, Mr. Langley left for Europe, but
before doing so he gave instructions to the workmen to remedy the small
weaknesses and defects which had been found in Aerodrome No. 6, and to
have both aerodromes ready for trial before his return in the fall.
Page 182
PL. 19. PATH OF AERODROME FLIGHTS, MAY 6 AND NOVEMBER 28, 1896,
NEAR QUANTICO, VA., ON THE POTOMAC RIVER ◊ lgr
NEAR QUANTICO, VA., ON THE POTOMAC RIVER ◊ lgr
Page 183
PL. 20. INSTANTANEOUS PHOTOGRAPH OF THE AERODROME AT THE
MOMENT AFTER LAUNCHING IN ITS FLIGHT AT QUANTICO ON THE
POTOMAC RIVER, MAY 6, 1896. ENLARGED TEN TIMES ◊
MOMENT AFTER LAUNCHING IN ITS FLIGHT AT QUANTICO ON THE
POTOMAC RIVER, MAY 6, 1896. ENLARGED TEN TIMES ◊
Page 184
PL. 21. INSTANTANEOUS PHOTOGRAPH OF THE AERODROME AT A
DISTANCE IN THE AIR DURING ITS FLIGHT AT QUANTICO ON THE
POTOMAC RIVER, MAY 6, 1896. ENLARGED TEN TIMES ◊
DISTANCE IN THE AIR DURING ITS FLIGHT AT QUANTICO ON THE
POTOMAC RIVER, MAY 6, 1896. ENLARGED TEN TIMES ◊
Page 185
PL. 22. INSTANTANEOUS PHOTOGRAPH OF THE AERODROME AT A
DISTANCE IN THE AIR DURING ITS FLIGHT AT QUANTICO ON THE
POTOMAC RIVER, MAY 6, 1896. ENLARGED TEN TIMES ◊
DISTANCE IN THE AIR DURING ITS FLIGHT AT QUANTICO ON THE
POTOMAC RIVER, MAY 6, 1896. ENLARGED TEN TIMES ◊
Page 186
PL. 23. OVERHEAD LAUNCHING APPARATUS ◊ lgr
Page 187
PL. 24. OVERHEAD LAUNCHING
APPARATUS ◊ lgr
APPARATUS ◊ lgr
Page 188
After returning in the fall, Mr. Langley again had Aerodromes Nos. 5 and
6 taken down to Quantico for trial, and this time had as his invited guest Mr.
Frank G. Carpenter. On November 27 a test was made of Aerodrome No. 6,
the general disposition of which at this time may be learned from the
description in Chapter X ◊, and the photographs in Plates 29A, 29B. The
model was launched at 4.25 p. m. with a steam pressure of 125 pounds. The
aerodrome went nearly horizontally against the wind, and descended into
the water in six and a quarter seconds at a distance of perhaps 100 yards.
After the machine had been recovered from the water, it was found that a
pin had broken in the synchronizing rod which connects the two propeller
shafts together, and that the counter, which showed 495 revolutions of the
propellers, had been caused to register [p109] inaccurately on this account.
The balancing of Aerodrome No. 6 had been made the same as that of No.
5, but in No. 6 the line of thrust was twelve centimetres higher, and this
fact, which had not been taken into account in determining the proper
balancing for No. 6, seemed to be sufficient cause for the aerodrome
coming down into the water so soon after being launched. Darkness had
descended before the aerodrome could be recovered and prepared for a
second trial. On the next day, November 28, a high wind prevailed in the
morning, but in the afternoon it became comparatively calm, and No. 6 was
launched at 4.20 p. m. under the same conditions as on the preceding day,
except that the float, which weighed 275 grammes, was moved back from
the bowsprit eighty centimetres in order to make the machine lighter in
front. The aerodrome was launched at a steam pressure of not much over
100 pounds, the air draft for the burners being temporarily bad. The midrod
made an angle of approximately three degrees with the horizontal. On
account of a slight rain, which had occurred just before the machine was
launched, the wings were wet and the weight of the entire aerodrome was
doubtless as much as twelve kilos. Immediately on being launched the
aerodrome started directly ahead in a gentle south wind, moving
horizontally and slowly turning to the right and appearing to approach
dangerously near to some thick woods on the west shore. However, it
fortunately continued turning until it pointed directly up the beach with the
6 taken down to Quantico for trial, and this time had as his invited guest Mr.
Frank G. Carpenter. On November 27 a test was made of Aerodrome No. 6,
the general disposition of which at this time may be learned from the
description in Chapter X ◊, and the photographs in Plates 29A, 29B. The
model was launched at 4.25 p. m. with a steam pressure of 125 pounds. The
aerodrome went nearly horizontally against the wind, and descended into
the water in six and a quarter seconds at a distance of perhaps 100 yards.
After the machine had been recovered from the water, it was found that a
pin had broken in the synchronizing rod which connects the two propeller
shafts together, and that the counter, which showed 495 revolutions of the
propellers, had been caused to register [p109] inaccurately on this account.
The balancing of Aerodrome No. 6 had been made the same as that of No.
5, but in No. 6 the line of thrust was twelve centimetres higher, and this
fact, which had not been taken into account in determining the proper
balancing for No. 6, seemed to be sufficient cause for the aerodrome
coming down into the water so soon after being launched. Darkness had
descended before the aerodrome could be recovered and prepared for a
second trial. On the next day, November 28, a high wind prevailed in the
morning, but in the afternoon it became comparatively calm, and No. 6 was
launched at 4.20 p. m. under the same conditions as on the preceding day,
except that the float, which weighed 275 grammes, was moved back from
the bowsprit eighty centimetres in order to make the machine lighter in
front. The aerodrome was launched at a steam pressure of not much over
100 pounds, the air draft for the burners being temporarily bad. The midrod
made an angle of approximately three degrees with the horizontal. On
account of a slight rain, which had occurred just before the machine was
launched, the wings were wet and the weight of the entire aerodrome was
doubtless as much as twelve kilos. Immediately on being launched the
aerodrome started directly ahead in a gentle south wind, moving
horizontally and slowly turning to the right and appearing to approach
dangerously near to some thick woods on the west shore. However, it
fortunately continued turning until it pointed directly up the beach with the
Page 189
wind in the rear. It then moved more rapidly forward, dipped and rose but
once, and this very slightly, and continued its remarkable horizontal flight,
varying not more than two yards out of a horizontal course, and this only
for a moment, until it finally descended into the bay at a point nearly in a
line between the house-boat and the railroad station at Quantico. Upon
being recovered, it was found to be absolutely uninjured, and another flight
would have been made with it immediately but darkness had descended.
The time of flight, as determined independently by two stop-watches, was
one minute and forty-five seconds. The number of revolutions of the
propellers was 2801, or at the rate of 1600 R. P. M., which, with an
allowance of fifty per cent slip, should have carried the aerodrome a
distance of 4600 feet in one and three-quarter minutes. While the distance
from the house-boat in a straight line to the point at which the aerodrome
descended was only about 1600 feet, yet it was estimated by those present
that this straight-line distance was certainly not greater than one-third the
total length of the path traversed, which would mean a distance of
something like 4800 feet. The length of the course, as plotted on the coast-
survey map and afterwards measured, was 4200 feet, and it, therefore,
seemed safe to say that the total distance travelled was about three-quarters
of a mile, and the speed was, therefore, about thirty miles an hour.
once, and this very slightly, and continued its remarkable horizontal flight,
varying not more than two yards out of a horizontal course, and this only
for a moment, until it finally descended into the bay at a point nearly in a
line between the house-boat and the railroad station at Quantico. Upon
being recovered, it was found to be absolutely uninjured, and another flight
would have been made with it immediately but darkness had descended.
The time of flight, as determined independently by two stop-watches, was
one minute and forty-five seconds. The number of revolutions of the
propellers was 2801, or at the rate of 1600 R. P. M., which, with an
allowance of fifty per cent slip, should have carried the aerodrome a
distance of 4600 feet in one and three-quarter minutes. While the distance
from the house-boat in a straight line to the point at which the aerodrome
descended was only about 1600 feet, yet it was estimated by those present
that this straight-line distance was certainly not greater than one-third the
total length of the path traversed, which would mean a distance of
something like 4800 feet. The length of the course, as plotted on the coast-
survey map and afterwards measured, was 4200 feet, and it, therefore,
seemed safe to say that the total distance travelled was about three-quarters
of a mile, and the speed was, therefore, about thirty miles an hour.
Page 190
[p110] ◊
CHAPTER X
DESCRIPTION OF THE LAUNCHING APPARATUS AND OF
AERODROMES Nos. 5 AND 6
Reference has already been made to the development of the “cast-off”
apparatus that was used at Quantico for launching the aerodrome. An initial
velocity is indispensable, and after long experiment with other forms which
proved failures, an apparatus was designed by me, which gave a sufficient
linear velocity in any direction. It had, moreover, been found that, when the
aerodrome was attached to any apparatus upon the roof of the house-boat,
such slight changes in the direction and intensity of the wind as would
ordinarily pass unperceived, would tend to distort or loosen it from its
support, so that only the most rigid of fastenings at three independent
bearing points were of any use in holding it, while the wings must be
separately fastened down, lest they should be torn from their sockets. It
was, then, necessary to be able to fasten the aerodrome very firmly to the
cast-off apparatus, to start it upon its journey in any direction with an initial
linear velocity that should equal its soaring speed, and to release it
simultaneously at all points at the very same instant, while at the same time
the points of contact of the launching device, to which it had just been
fastened, were themselves drawn up out of the way of the passing propellers
and guys.
All these requirements and others were met by the apparatus finally
adopted, which is shown in Plates 23 and 24. It consists of a strong timber
frame-work, carrying a track, consisting of two flat iron rails set on edge,
upon which runs the launching car, suspended from two small wheels on
each side. At the front end of the frame there are two cylindrical air buffers
to receive the buffing pistons and thus stop the car after the aerodrome has
been released. The car is drawn to the rear end of the track and held by the
bell-crank lever A (Plate 23). The contact points BB and C are turned down
and the clutch-hook D set over the clutch-post K. The aerodrome is thus
CHAPTER X
DESCRIPTION OF THE LAUNCHING APPARATUS AND OF
AERODROMES Nos. 5 AND 6
Reference has already been made to the development of the “cast-off”
apparatus that was used at Quantico for launching the aerodrome. An initial
velocity is indispensable, and after long experiment with other forms which
proved failures, an apparatus was designed by me, which gave a sufficient
linear velocity in any direction. It had, moreover, been found that, when the
aerodrome was attached to any apparatus upon the roof of the house-boat,
such slight changes in the direction and intensity of the wind as would
ordinarily pass unperceived, would tend to distort or loosen it from its
support, so that only the most rigid of fastenings at three independent
bearing points were of any use in holding it, while the wings must be
separately fastened down, lest they should be torn from their sockets. It
was, then, necessary to be able to fasten the aerodrome very firmly to the
cast-off apparatus, to start it upon its journey in any direction with an initial
linear velocity that should equal its soaring speed, and to release it
simultaneously at all points at the very same instant, while at the same time
the points of contact of the launching device, to which it had just been
fastened, were themselves drawn up out of the way of the passing propellers
and guys.
All these requirements and others were met by the apparatus finally
adopted, which is shown in Plates 23 and 24. It consists of a strong timber
frame-work, carrying a track, consisting of two flat iron rails set on edge,
upon which runs the launching car, suspended from two small wheels on
each side. At the front end of the frame there are two cylindrical air buffers
to receive the buffing pistons and thus stop the car after the aerodrome has
been released. The car is drawn to the rear end of the track and held by the
bell-crank lever A (Plate 23). The contact points BB and C are turned down
and the clutch-hook D set over the clutch-post K. The aerodrome is thus
Page 191
held firmly up against the three points BB and C by the clutch D, and a
distortion from its proper position rendered impossible. All these points are
thrown up out of the way of the projecting portions of the aerodrome at the
instant of release. This result is accomplished as follows: when the car has
reached the proper point in its forward course, the cam E, which is hinged
at 1, is depressed by a roller fixed to the framework of the device. In this
motion it pushes down the adjustable connections FF, which are attached at
their lower ends to the bell-crank arms GG, which turn about a central pivot
at 2. Thus the downward movement of the connections FF opens the jaws
of the [p111] clutch D. While the clutch D is rigidly attached to G to prevent
transverse movement, it is hinged to the latter at 3 so that it can fold in a
longitudinal direction. Screwed to the clutch D is a narrow plate 4, which,
when the clutch is closed, is behind the lug 5, thus preventing any turning
about the hinge 3.
But when the arms of G and the jaws of the clamp are thrown out by the
depression of F, the plate 4 is moved out from behind the lug 5 and the
clamp is free to fold to the front. The strut, hinged at 6, is under a constant
tension from the spring 7 to fold up, and is prevented from doing so only by
the connections 8, by which it is held down until the release of the plate 4
from behind the lug 5, when the spring snaps them instantly up and out of
the way.
As the struts BB have no fixed connection with the aerodrome, they are
released by the relaxation in the rigidity of the other connections and are
thrown up by their spring 9 and held in that position by the clip 10 catching
beneath the upper cross-piece.
The power for the propulsion of the car is obtained by means of from one
to nine helical springs working under tension, and multiplying their own
motion four times by means of a movable two-sheave pulley, as shown in
the drawing.
D ESCRIPTION OF A ERODROME N O. 5
When the details of the aerodrome, whose description is to follow, are
considered from the standpoint of the engineer accustomed to make every
distortion from its proper position rendered impossible. All these points are
thrown up out of the way of the projecting portions of the aerodrome at the
instant of release. This result is accomplished as follows: when the car has
reached the proper point in its forward course, the cam E, which is hinged
at 1, is depressed by a roller fixed to the framework of the device. In this
motion it pushes down the adjustable connections FF, which are attached at
their lower ends to the bell-crank arms GG, which turn about a central pivot
at 2. Thus the downward movement of the connections FF opens the jaws
of the [p111] clutch D. While the clutch D is rigidly attached to G to prevent
transverse movement, it is hinged to the latter at 3 so that it can fold in a
longitudinal direction. Screwed to the clutch D is a narrow plate 4, which,
when the clutch is closed, is behind the lug 5, thus preventing any turning
about the hinge 3.
But when the arms of G and the jaws of the clamp are thrown out by the
depression of F, the plate 4 is moved out from behind the lug 5 and the
clamp is free to fold to the front. The strut, hinged at 6, is under a constant
tension from the spring 7 to fold up, and is prevented from doing so only by
the connections 8, by which it is held down until the release of the plate 4
from behind the lug 5, when the spring snaps them instantly up and out of
the way.
As the struts BB have no fixed connection with the aerodrome, they are
released by the relaxation in the rigidity of the other connections and are
thrown up by their spring 9 and held in that position by the clip 10 catching
beneath the upper cross-piece.
The power for the propulsion of the car is obtained by means of from one
to nine helical springs working under tension, and multiplying their own
motion four times by means of a movable two-sheave pulley, as shown in
the drawing.
D ESCRIPTION OF A ERODROME N O. 5
When the details of the aerodrome, whose description is to follow, are
considered from the standpoint of the engineer accustomed to make every
Page 192
provision against breakage and accident and to allow an ample factor of
safety in every part, they will be found far too weak to stand the stresses
that were put upon them. But it must be remembered that in designing this
machine, all precedent had to be laid aside and new rules, adapted to the
new conditions, applied. It was absolutely necessary, in order to insure
success, that the weight should be cut down to the lowest possible point,
and when this was reached it was found that the factor of safety had been
almost entirely done away with, and that the stresses applied and the
strength of material were almost equal.
The same observation holds true of the boilers, aeolipile, and engines,
when regarded from the point of view of the economical generation and use
of steam. It was fully recognized that the waste of heat in the coil boilers
was excessive, but as it was necessary that there should be an exceedingly
rapid generation of steam with a small heating surface, this was regarded as
inevitable.
In the engine the three points aimed at in the design were lightness,
strength and power, but lightness above all, and necessarily in a degree
which long seemed incompatible with strength. No attempt was made to
secure the requirements of modern steam-engine construction, either in the
distribution of the steam or the protection of the cylinder against the
radiation of heat by a suitable jacketing. The very narrow limits of weight
permissible required that the [p112] barrel of the cylinder should be as thin as
possible, that no protective jacketing should be used, and that the valve
motion should be of the simplest description. To obtaining the greatest
lightness consistent with indispensable power, everything else was
subordinated; and hence, all expectation of ordinary economical efficiency
had to be abandoned at the outset.
It was only after long trials in other directions that Mr. Langley
introduced the aeolipile device, which for the first time provided sufficient
heat. Even in the aeolipile, however, is was apparent that nothing short of
the most complete combustion accompanied by the highest possible
temperature of the flame would be sufficient for the extreme demand. To
secure this result under all conditions of wind and weather, with the
safety in every part, they will be found far too weak to stand the stresses
that were put upon them. But it must be remembered that in designing this
machine, all precedent had to be laid aside and new rules, adapted to the
new conditions, applied. It was absolutely necessary, in order to insure
success, that the weight should be cut down to the lowest possible point,
and when this was reached it was found that the factor of safety had been
almost entirely done away with, and that the stresses applied and the
strength of material were almost equal.
The same observation holds true of the boilers, aeolipile, and engines,
when regarded from the point of view of the economical generation and use
of steam. It was fully recognized that the waste of heat in the coil boilers
was excessive, but as it was necessary that there should be an exceedingly
rapid generation of steam with a small heating surface, this was regarded as
inevitable.
In the engine the three points aimed at in the design were lightness,
strength and power, but lightness above all, and necessarily in a degree
which long seemed incompatible with strength. No attempt was made to
secure the requirements of modern steam-engine construction, either in the
distribution of the steam or the protection of the cylinder against the
radiation of heat by a suitable jacketing. The very narrow limits of weight
permissible required that the [p112] barrel of the cylinder should be as thin as
possible, that no protective jacketing should be used, and that the valve
motion should be of the simplest description. To obtaining the greatest
lightness consistent with indispensable power, everything else was
subordinated; and hence, all expectation of ordinary economical efficiency
had to be abandoned at the outset.
It was only after long trials in other directions that Mr. Langley
introduced the aeolipile device, which for the first time provided sufficient
heat. Even in the aeolipile, however, is was apparent that nothing short of
the most complete combustion accompanied by the highest possible
temperature of the flame would be sufficient for the extreme demand. To
secure this result under all conditions of wind and weather, with the
Page 193
aerodrome at rest and in motion, required the long series of experiments
that are given in another chapter. In respect to the generation of heat, then, it
is probable that it would be difficult to exceed the performance of the final
type of burner in practical work, but in the utilization of this heat in the
boiler, as well as in the utilization of the steam there generated, the waste
was so great as to be prohibitive under ordinary conditions. But this was not
ordinary work, and the simplest protection against radiation from boiler,
separator, and engine could not well be used.
The framework of the aerodrome is made of thin steel tubes, the main or
midrod extending the whole length of the machine and carrying the
attachments to which the wings are fastened. Suspended from this midrod
by rigid connections is a skeleton hull of steel tubing, shaped somewhat like
the framework of a boat, from which, directly abeam of the engines, arms
are run out like the outriggers of a rowboat for carrying the propellers.
Within this central hull are placed the aeolipile, the boiler, and the engine,
which with their auxiliary parts, the pump and the separator, constitute the
entire power-generating apparatus.
The aeolipile consists of four essential parts: the spherical air chamber
containing the supply of compressed air by which the gasoline in the
reservoir tank is forced into the burner; the reservoir tank containing the
gasoline that is to be used as a fuel; the gas generator wherein the liquid
gasoline is heated and converted into gas; and the burners where it is finally
utilized to heat the boilers.
The air chamber D, Plate 25, is a spherical vessel 120 mm. in diameter,
located at the extreme front end of the hull. It is made of copper 0.25 mm.
thick and has two openings. The front opening has a copper pipe 1 cm.
outside diameter, to which the air pump for charging the chamber is
connected. From the back a copper pipe 5 mm. outside diameter extends to
the top of the gasoline reservoir.
that are given in another chapter. In respect to the generation of heat, then, it
is probable that it would be difficult to exceed the performance of the final
type of burner in practical work, but in the utilization of this heat in the
boiler, as well as in the utilization of the steam there generated, the waste
was so great as to be prohibitive under ordinary conditions. But this was not
ordinary work, and the simplest protection against radiation from boiler,
separator, and engine could not well be used.
The framework of the aerodrome is made of thin steel tubes, the main or
midrod extending the whole length of the machine and carrying the
attachments to which the wings are fastened. Suspended from this midrod
by rigid connections is a skeleton hull of steel tubing, shaped somewhat like
the framework of a boat, from which, directly abeam of the engines, arms
are run out like the outriggers of a rowboat for carrying the propellers.
Within this central hull are placed the aeolipile, the boiler, and the engine,
which with their auxiliary parts, the pump and the separator, constitute the
entire power-generating apparatus.
The aeolipile consists of four essential parts: the spherical air chamber
containing the supply of compressed air by which the gasoline in the
reservoir tank is forced into the burner; the reservoir tank containing the
gasoline that is to be used as a fuel; the gas generator wherein the liquid
gasoline is heated and converted into gas; and the burners where it is finally
utilized to heat the boilers.
The air chamber D, Plate 25, is a spherical vessel 120 mm. in diameter,
located at the extreme front end of the hull. It is made of copper 0.25 mm.
thick and has two openings. The front opening has a copper pipe 1 cm.
outside diameter, to which the air pump for charging the chamber is
connected. From the back a copper pipe 5 mm. outside diameter extends to
the top of the gasoline reservoir.
Page 194
PL. 25. SIDEVIEW OF STEEL FRAME OF AERODROME NO.
5 SUSPENDED FROM LAUNCHING-CAR, OCTOBER 24,
1896 ◊ lgr
5 SUSPENDED FROM LAUNCHING-CAR, OCTOBER 24,
1896 ◊ lgr
Page 195
This reservoir, shown at I, Plate 25, is also a light, hollow sphere 120
mm. in diameter; both this and the air chamber being made by soldering
hemispheres [p113] of copper together at their circumferences. There are
three openings in the reservoir tank; two at the top and one at the bottom.
One of those at the top serves for the admission of the 5-mm. pipe bringing
compressed air from the air chamber; the other is connected with a pipe 1
cm. in diameter, through which gasoline is supplied to the tank, and which
is closed by a simple plug at the top. The hole in the bottom serves as the
outlet for the gasoline to the burners. Close to the bottom of the tank there
is placed a small needle valve, which serves to regulate the flow of oil, for,
were the pipe left open, the compressed air would force the oil out with
such rapidity that the burners would be flooded and the intensity of the
flame impaired. The construction of this valve is clearly shown in Plate
26A. It consists of a brass shell having one end (a ) soldered to the bottom
of the tank. The needle enters through a stuffing box whose gland is held by
two small screws. The stem of the needle is threaded and engages in a
thread cut in the body of the casting and is operated by a fine wire on the
outside. It will readily be seen that this device affords a means of making a
very accurate adjustment of the flow of the liquid to the burners.
After leaving the needle valve the gasoline flows along the pipe S, Plate
25, until it reaches the evaporating coil, N. In order to subject the oil to as
large a heating surface as possible, in comparison with the sectional area
through which it is flowing, the pipe, which left the needle valve with a
diameter of 6 mm. soon contracted to 5 mm., is here flattened to a width of
7 mm. and a thickness of 2 mm. There are seven complete turns of this
flattened tubing coiled to an outside diameter of 30 mm. At the end of the
seventh coil the pipe is enlarged to a diameter of 1 cm. and two coils of this
size are added, the inside diameter being the same as that of the flattened
coil. This enlarged portion serves as a sort of expansion chamber for the
complete gasification of the gasoline, which is then led back through a turn
of the enlarged pipe, beneath the coils and to the front. At the front end of
the coil a small branch is led off, forming a “bleeder,” which takes
sufficient gas to supply the burner by which the coil is heated, the products
mm. in diameter; both this and the air chamber being made by soldering
hemispheres [p113] of copper together at their circumferences. There are
three openings in the reservoir tank; two at the top and one at the bottom.
One of those at the top serves for the admission of the 5-mm. pipe bringing
compressed air from the air chamber; the other is connected with a pipe 1
cm. in diameter, through which gasoline is supplied to the tank, and which
is closed by a simple plug at the top. The hole in the bottom serves as the
outlet for the gasoline to the burners. Close to the bottom of the tank there
is placed a small needle valve, which serves to regulate the flow of oil, for,
were the pipe left open, the compressed air would force the oil out with
such rapidity that the burners would be flooded and the intensity of the
flame impaired. The construction of this valve is clearly shown in Plate
26A. It consists of a brass shell having one end (a ) soldered to the bottom
of the tank. The needle enters through a stuffing box whose gland is held by
two small screws. The stem of the needle is threaded and engages in a
thread cut in the body of the casting and is operated by a fine wire on the
outside. It will readily be seen that this device affords a means of making a
very accurate adjustment of the flow of the liquid to the burners.
After leaving the needle valve the gasoline flows along the pipe S, Plate
25, until it reaches the evaporating coil, N. In order to subject the oil to as
large a heating surface as possible, in comparison with the sectional area
through which it is flowing, the pipe, which left the needle valve with a
diameter of 6 mm. soon contracted to 5 mm., is here flattened to a width of
7 mm. and a thickness of 2 mm. There are seven complete turns of this
flattened tubing coiled to an outside diameter of 30 mm. At the end of the
seventh coil the pipe is enlarged to a diameter of 1 cm. and two coils of this
size are added, the inside diameter being the same as that of the flattened
coil. This enlarged portion serves as a sort of expansion chamber for the
complete gasification of the gasoline, which is then led back through a turn
of the enlarged pipe, beneath the coils and to the front. At the front end of
the coil a small branch is led off, forming a “bleeder,” which takes
sufficient gas to supply the burner by which the coil is heated, the products
Page 196
of whose combustion pass into and between the coils of the boiler like those
of the regular heating burners. The gas pipe rises in front of the coil and by
a T connection branches to the two burners that are placed in front of the
coils of the boiler. These burner pipes are 5 mm. in diameter and enter
sheet-iron hoods forming regular burners of the Bunsen type, which are
fully shown in all their details in the accompanying engraving, Plate 26.
The pipe is plugged at the end, and a hole 0.9 mm. in diameter drilled for
the nipple of the burner in front of the coil where the water first enters from
the separator, and 0.85 mm. for the one in front of the return coil. The face
of the burner shell stands exactly central with and 41 mm. in front of the
coils.35 [p114]
This constitutes the heat-generating portion of the machine, and with it it
is probable that a flame of as high a temperature is produced as can be
reached, with the fuel used, by any practical device.
The boiler or steam-generating apparatus may be said to consist of three
parts: the separator, the circulating pumps, and the generating coils.
The separator (M in Plate 25) is a device which has attained its present
form after a long course of development. As at present constructed, it is
formed of a hollow sphere 190 mm. in diameter and is located as nearly as
possible over the center of gravity of the whole apparatus. It serves the
double purpose of water reservoir and steam drum, and is called a
“separator” on account of the function which it performs of separating the
water from the steam as it enters from the coils. There is a straight vertical
pipe 10 mm. in diameter rising from the top of the sphere and fastened to
the right-hand side of the midrod. This is used for filling the separator with
water. Upon the other side of the midrod there is a small steam dome 42
mm. in diameter with a semi-spherical top rising to a height of 70 mm.
above the top of the sphere. From this dome two steam pipes are led off,
one to the engine and the other to the steam gauge.
As already stated elsewhere, it was found in the experiments with the coil
boiler that an artificial forcing of the circulation of the water was a
necessity, as the natural circulation was too slow to be of any service.
Accordingly, but only after numerous devices involving less weight had
of the regular heating burners. The gas pipe rises in front of the coil and by
a T connection branches to the two burners that are placed in front of the
coils of the boiler. These burner pipes are 5 mm. in diameter and enter
sheet-iron hoods forming regular burners of the Bunsen type, which are
fully shown in all their details in the accompanying engraving, Plate 26.
The pipe is plugged at the end, and a hole 0.9 mm. in diameter drilled for
the nipple of the burner in front of the coil where the water first enters from
the separator, and 0.85 mm. for the one in front of the return coil. The face
of the burner shell stands exactly central with and 41 mm. in front of the
coils.35 [p114]
This constitutes the heat-generating portion of the machine, and with it it
is probable that a flame of as high a temperature is produced as can be
reached, with the fuel used, by any practical device.
The boiler or steam-generating apparatus may be said to consist of three
parts: the separator, the circulating pumps, and the generating coils.
The separator (M in Plate 25) is a device which has attained its present
form after a long course of development. As at present constructed, it is
formed of a hollow sphere 190 mm. in diameter and is located as nearly as
possible over the center of gravity of the whole apparatus. It serves the
double purpose of water reservoir and steam drum, and is called a
“separator” on account of the function which it performs of separating the
water from the steam as it enters from the coils. There is a straight vertical
pipe 10 mm. in diameter rising from the top of the sphere and fastened to
the right-hand side of the midrod. This is used for filling the separator with
water. Upon the other side of the midrod there is a small steam dome 42
mm. in diameter with a semi-spherical top rising to a height of 70 mm.
above the top of the sphere. From this dome two steam pipes are led off,
one to the engine and the other to the steam gauge.
As already stated elsewhere, it was found in the experiments with the coil
boiler that an artificial forcing of the circulation of the water was a
necessity, as the natural circulation was too slow to be of any service.
Accordingly, but only after numerous devices involving less weight had
Page 197
failed, a pump driven from the engine shaft was designed and used. In the
early experiments various types of pumps were tried in which the valves
were opened and closed automatically by the pressure of the water. It was
found, however, that with the mixture of steam and water to be handled, the
valves could not be depended upon to open and close properly at the high
speeds at which is was necessary to run the engine. In Aerodrome No. 5,
therefore, a double-acting pump with a mechanically operated valve was
used. The pump, shown in detail in Plate 26A, is driven from a shaft
connected with the main engine shaft by a spur gear and pinion, which
rotates at half the speed of the engine shaft. The pump itself consists of two
barrels, the main barrel having a diameter of 23 mm. with a piston stroke of
20 mm. The outer shell of the barrel is made of aluminum bronze and is
lined with a cast-iron bushing 1.25 mm. in thickness. The piston has a
length of 14 mm. and is formed of an aluminum disc and center, having a
follower plate of the same material with two cast-iron split rings sprung in.
The water is received into and delivered from the valve cylinder, which is
18 mm. in diameter and also lined with a cast-iron bushing 1.25 mm. thick.
The aluminum bronze shells of both cylinders are 0.75 mm. in thickness.
The valve is a simple piston valve 35 mm. long with bearing faces 4 mm.
long at each end. The water is taken from the bottom of the separator and
led to the center of the valve chest of the pump by a copper pipe 1 cm.
outside diameter. The ports [p115] leading from the valve to the main
cylinder are 3 mm. wide and 34 mm. apart over their openings. It will thus
be seen that when the valve is in its central position, as it should be at the
beginning of the piston stroke, both ports are covered with a lap of 0.5 mm.
inside and out, so that the valve has to move 0.5 mm. before suction or
discharge can take place. As the valve is moving most rapidly at this point,
it opens and both functions begin before the piston has advanced
perceptibly. The delivery is made at the ends of the valve cylinder through
two copper pipes of 1 cm. diameter that unite into a single pipe before
reaching the boiler. The throw of the valve is 14 mm. so that the ports are
uncovered and held wide open for the greater portion of the stroke of the
piston, and begin to close only when the latter approaches the end of its
early experiments various types of pumps were tried in which the valves
were opened and closed automatically by the pressure of the water. It was
found, however, that with the mixture of steam and water to be handled, the
valves could not be depended upon to open and close properly at the high
speeds at which is was necessary to run the engine. In Aerodrome No. 5,
therefore, a double-acting pump with a mechanically operated valve was
used. The pump, shown in detail in Plate 26A, is driven from a shaft
connected with the main engine shaft by a spur gear and pinion, which
rotates at half the speed of the engine shaft. The pump itself consists of two
barrels, the main barrel having a diameter of 23 mm. with a piston stroke of
20 mm. The outer shell of the barrel is made of aluminum bronze and is
lined with a cast-iron bushing 1.25 mm. in thickness. The piston has a
length of 14 mm. and is formed of an aluminum disc and center, having a
follower plate of the same material with two cast-iron split rings sprung in.
The water is received into and delivered from the valve cylinder, which is
18 mm. in diameter and also lined with a cast-iron bushing 1.25 mm. thick.
The aluminum bronze shells of both cylinders are 0.75 mm. in thickness.
The valve is a simple piston valve 35 mm. long with bearing faces 4 mm.
long at each end. The water is taken from the bottom of the separator and
led to the center of the valve chest of the pump by a copper pipe 1 cm.
outside diameter. The ports [p115] leading from the valve to the main
cylinder are 3 mm. wide and 34 mm. apart over their openings. It will thus
be seen that when the valve is in its central position, as it should be at the
beginning of the piston stroke, both ports are covered with a lap of 0.5 mm.
inside and out, so that the valve has to move 0.5 mm. before suction or
discharge can take place. As the valve is moving most rapidly at this point,
it opens and both functions begin before the piston has advanced
perceptibly. The delivery is made at the ends of the valve cylinder through
two copper pipes of 1 cm. diameter that unite into a single pipe before
reaching the boiler. The throw of the valve is 14 mm. so that the ports are
uncovered and held wide open for the greater portion of the stroke of the
piston, and begin to close only when the latter approaches the end of its
Page 198
stroke. In this way perfect freedom is given to the flow of the water and all
choking is avoided. As the engine has been run at a speed of more than 688
revolutions per minute, the pump must have made at least 344 strokes in the
same time, thus displacing 166.2 cc. of water. The diameter of the piston
rod and valve stem is 3 mm. and they pass through stuffing boxes with
glands of the ordinary type for packing. This pump served its purpose
admirably, and with it it was possible to maintain a continuous circulation
of water through the two coils of the boiler.
The third element in the steam-generating system is the boiler proper36
(Plates 25 and 26A), which consists of two coils of copper pipe, having an
outside diameter of 10 mm., each coil being formed of 21 turns each 75
mm. in diameter upon the outside and spaced 7.5 mm. apart, so that the
total axial length of each coil is 36 cm.
The water is delivered to the front end of the right-hand coil, and, first
passing through this, crosses over at the rear of the boiler to the left-hand
coil, returning through it to the front whence it is led to and delivered into
the top of the separator. Here the steam and water are separated, the former
going through the separator and thence to the engine, while the
unevaporated water falls to the bottom to be again taken into the pumps and
sent through the coils.
In order that the draft of the burner and the gases of combustion might
not be dissipated, it was necessary to sheathe the boiler. The method of
doing this is shown in Plate 25. It will be seen that the front half of the
boiler is wrapped in a sheet of mica through which the coils can be faintly
seen. This, in turn, is held at the extreme front end by a strip of thin sheet-
iron, O. Over the back end the stack Q, made of very thin sheet-iron, is
slipped. This has an oblong cross-section at the lower end where it goes
over the boiler; it is provided with a hole through which the midrod passes,
and terminates in a circular opening of about 10 cm. diameter. [p116]
The engine, which is clearly shown in the dimensional drawing, Plate
26B, is of the plain slide-valve type, using a piston valve and solid piston,
without packing rings. The cylinder is formed of a piece of steel tubing 35
mm. outside diameter, with flanges 47 mm. in diameter and 2.25 mm. thick
choking is avoided. As the engine has been run at a speed of more than 688
revolutions per minute, the pump must have made at least 344 strokes in the
same time, thus displacing 166.2 cc. of water. The diameter of the piston
rod and valve stem is 3 mm. and they pass through stuffing boxes with
glands of the ordinary type for packing. This pump served its purpose
admirably, and with it it was possible to maintain a continuous circulation
of water through the two coils of the boiler.
The third element in the steam-generating system is the boiler proper36
(Plates 25 and 26A), which consists of two coils of copper pipe, having an
outside diameter of 10 mm., each coil being formed of 21 turns each 75
mm. in diameter upon the outside and spaced 7.5 mm. apart, so that the
total axial length of each coil is 36 cm.
The water is delivered to the front end of the right-hand coil, and, first
passing through this, crosses over at the rear of the boiler to the left-hand
coil, returning through it to the front whence it is led to and delivered into
the top of the separator. Here the steam and water are separated, the former
going through the separator and thence to the engine, while the
unevaporated water falls to the bottom to be again taken into the pumps and
sent through the coils.
In order that the draft of the burner and the gases of combustion might
not be dissipated, it was necessary to sheathe the boiler. The method of
doing this is shown in Plate 25. It will be seen that the front half of the
boiler is wrapped in a sheet of mica through which the coils can be faintly
seen. This, in turn, is held at the extreme front end by a strip of thin sheet-
iron, O. Over the back end the stack Q, made of very thin sheet-iron, is
slipped. This has an oblong cross-section at the lower end where it goes
over the boiler; it is provided with a hole through which the midrod passes,
and terminates in a circular opening of about 10 cm. diameter. [p116]
The engine, which is clearly shown in the dimensional drawing, Plate
26B, is of the plain slide-valve type, using a piston valve and solid piston,
without packing rings. The cylinder is formed of a piece of steel tubing 35
mm. outside diameter, with flanges 47 mm. in diameter and 2.25 mm. thick
Page 199
brazed to each end, to which the cylinder heads are attached by small
machine screws. Inside this cylinder is a thin cast-iron bushing in order to
obtain a better rubbing surface for the piston. The cross-head is a small
piece of aluminum bronze, running on round guides that also serve as
cylinder braces. There are also four hollow braces, 5 mm. in diameter,
running from the back cylinder head to a corrugated steel bed-plate, that
stands vertically and reaches from one side rod of the frame of the hull to
the other, and to which are bolted the bearings of the main shaft. The
connecting rod has the cross-section of a four-rayed star and drives a crank
in the center of the shaft. The following are some of the principal
dimensions of the engine:
millimetres.
Inside diameter of cylinder 33
Stroke of piston 70
Length of cylinder inside 88
Length of piston 11
Clearance at each end 0.5
Diameter of piston rod 5
Length of cross-head 17.5
Diameter of guides 4.5
Distance from center to center of guides 26
Length of guides 110
Length of wrist-pin bearing 8.5
Length of connecting rod 150
Ratio of connecting rod to stroke 2 1/7 to 1
Length of crank pin 10
Diameter of main shaft 8
Length of main bearings 25
Distance from center of cylinder to center of valve stem 35
Length of valve 72
Width of ports 2
Outside lap of valve 4
Inside lap of valve 3
Lead of valve 0
Travel of valve 13
Cut-off from beginning of stroke 57
Exhaust opens End of stroke
Exhaust closes on return stroke 48
Diameter of valve stem 4.5
Diameter of eccentric 36
Width of eccentric 4
Width of crank arm 4
machine screws. Inside this cylinder is a thin cast-iron bushing in order to
obtain a better rubbing surface for the piston. The cross-head is a small
piece of aluminum bronze, running on round guides that also serve as
cylinder braces. There are also four hollow braces, 5 mm. in diameter,
running from the back cylinder head to a corrugated steel bed-plate, that
stands vertically and reaches from one side rod of the frame of the hull to
the other, and to which are bolted the bearings of the main shaft. The
connecting rod has the cross-section of a four-rayed star and drives a crank
in the center of the shaft. The following are some of the principal
dimensions of the engine:
millimetres.
Inside diameter of cylinder 33
Stroke of piston 70
Length of cylinder inside 88
Length of piston 11
Clearance at each end 0.5
Diameter of piston rod 5
Length of cross-head 17.5
Diameter of guides 4.5
Distance from center to center of guides 26
Length of guides 110
Length of wrist-pin bearing 8.5
Length of connecting rod 150
Ratio of connecting rod to stroke 2 1/7 to 1
Length of crank pin 10
Diameter of main shaft 8
Length of main bearings 25
Distance from center of cylinder to center of valve stem 35
Length of valve 72
Width of ports 2
Outside lap of valve 4
Inside lap of valve 3
Lead of valve 0
Travel of valve 13
Cut-off from beginning of stroke 57
Exhaust opens End of stroke
Exhaust closes on return stroke 48
Diameter of valve stem 4.5
Diameter of eccentric 36
Width of eccentric 4
Width of crank arm 4
Page 200
The weights were nearly as follows:
grammes.
Engine 464
Pump and pump shafts 231
Gasoline tank and valves 178
Burners 360
Boilers, frames holding boilers, and mica covers over boilers 651
Separator, steam gauge and pipe for engine 540
Exhaust pipe 143
Smoke stack 342
In all, 2909 grammes, or 6.4 pounds.
grammes.
Engine 464
Pump and pump shafts 231
Gasoline tank and valves 178
Burners 360
Boilers, frames holding boilers, and mica covers over boilers 651
Separator, steam gauge and pipe for engine 540
Exhaust pipe 143
Smoke stack 342
In all, 2909 grammes, or 6.4 pounds.
Page 201
PL. 26A. DIMENSIONED DRAWING OF BOILER COILS, BURNERS, PUMP,
NEEDLE VALVE AND THRUST BEARING ◊ lgr
NEEDLE VALVE AND THRUST BEARING ◊ lgr
Page 202
PL. 26B. DIMENSIONED DRAWING OF ENGINE NO. 5 ◊ lgr
Page 203
PL. 27A. SIDE AND END ELEVATIONS OF AERODROME NO. 5, MAY 11, 1896 ◊
Page 204
PL. 27B. AERODROME NO. 5 PLAN VIEW. OCTOBER 24, 1896 ◊
[p117]
[p117]
Page 205
These weights are those determined in December, 1896, when some
slight changes had been made from the conditions existing at the time of the
flight by this aerodrome on May 6. Previous to that time, with a pressure of
130 pounds, between 1.1 and 1.25 horse-power was given on the Prony
brake. At the actual time of flight the pressure was about 115 pounds, and
the actual power very near 1 horse-power.
The valve stem was pivoted to the center of the valve partly because this
was the lightest connection that could be made, and partly to allow the
valve perfect freedom of adjustment upon the seat. Many parts, such as
guides, braces, crank-pins, wrist-pin and shafts are hollow. The steam is
taken in at the front end of the steam chest, and the exhaust taken out of the
center, whence it is led back to the stack and by means of a forked exhaust
pipe discharged in such a way as to assist the draught of each coil of the
boilers. Like the cylinder the steam chest is made of a piece of steel tubing,
20 mm. diameter on the outside, with an inside diameter of 19 mm., and is
fitted with a cast-iron bushing 0.5 mm. thick, making the inside diameter of
the steam chest 18 mm. It, too, has flanges brazed to the ends, to which the
heads are held by small machine screws.
The shaft for conveying the power to the propeller shafts extends across
the machine from side to side; it is hollow, being 8 mm. outside diameter,
with a hole 5 mm. diameter through the center.
It is formed of five sections: the middle section, containing the crank, has
a length of 110 mm. and is connected at either end, by flanged couplings, to
lengths 320 mm. long, which are in turn extended by the end sections
having a length of 230 mm. In addition to the four main bearings that are
bolted to the pressed-steel bed-plate already mentioned, there are two
bearings on the outer framework on each side. At the outer end of each shaft
there is keyed thereto a bevel gear with an outside diameter of 27 mm. and
having 28 teeth. This gear meshes with one of 35 teeth upon a shaft at right
angles to the main shaft and parallel to the axis of the aerodrome. These two
shafts, one on either arm, serve to carry and transmit the power to the
propellers. They are 192 mm. long, 8 mm. in diameter, and are provided
with three bearings that are brazed to a corrugated steel plate forming the
slight changes had been made from the conditions existing at the time of the
flight by this aerodrome on May 6. Previous to that time, with a pressure of
130 pounds, between 1.1 and 1.25 horse-power was given on the Prony
brake. At the actual time of flight the pressure was about 115 pounds, and
the actual power very near 1 horse-power.
The valve stem was pivoted to the center of the valve partly because this
was the lightest connection that could be made, and partly to allow the
valve perfect freedom of adjustment upon the seat. Many parts, such as
guides, braces, crank-pins, wrist-pin and shafts are hollow. The steam is
taken in at the front end of the steam chest, and the exhaust taken out of the
center, whence it is led back to the stack and by means of a forked exhaust
pipe discharged in such a way as to assist the draught of each coil of the
boilers. Like the cylinder the steam chest is made of a piece of steel tubing,
20 mm. diameter on the outside, with an inside diameter of 19 mm., and is
fitted with a cast-iron bushing 0.5 mm. thick, making the inside diameter of
the steam chest 18 mm. It, too, has flanges brazed to the ends, to which the
heads are held by small machine screws.
The shaft for conveying the power to the propeller shafts extends across
the machine from side to side; it is hollow, being 8 mm. outside diameter,
with a hole 5 mm. diameter through the center.
It is formed of five sections: the middle section, containing the crank, has
a length of 110 mm. and is connected at either end, by flanged couplings, to
lengths 320 mm. long, which are in turn extended by the end sections
having a length of 230 mm. In addition to the four main bearings that are
bolted to the pressed-steel bed-plate already mentioned, there are two
bearings on the outer framework on each side. At the outer end of each shaft
there is keyed thereto a bevel gear with an outside diameter of 27 mm. and
having 28 teeth. This gear meshes with one of 35 teeth upon a shaft at right
angles to the main shaft and parallel to the axis of the aerodrome. These two
shafts, one on either arm, serve to carry and transmit the power to the
propellers. They are 192 mm. long, 8 mm. in diameter, and are provided
with three bearings that are brazed to a corrugated steel plate forming the
Page 206
end of the outrigger portion of the frame. These shafts are also hollow,
having an axial hole 4 mm. in diameter drilled through them. The propeller
seat has a length of 43 mm. and the propeller is held in position by a collar
25 mm. in diameter at the front end, from which there project two dowel-
pins that fit into corresponding holes in the hubs of the propellers, which
are held up against the collar by a smaller one screwed into the back end of
the shaft. The thrust of the collar is taken up by a pin screwed into the end
of the forward box and acting as a step against which the shaft bears, the
arrangement being clearly shown by the accompanying drawing, Plate 26A.
[p118]
This, then, comprises the motive power equipment of the aerodrome,
and, to recapitulate, it includes the storage, automatic feeding and
regulation of the fuel; the storage, circulation and evaporation of the water;
the engine to convert the expansive power of the steam into mechanical
work; and the shafting for the transmission of the energy developed by the
engine to the propellers.
The propellers were made with the greatest care. Those used in the
successful trials were 1 metre in diameter, with an actual axial pitch of 1.25
metres. They were made of white pine, glued together in strips 7 mm. thick.
The hub had a length of 45 mm. and a thickness or diameter of 25 mm. At
the outer edge the blade had a width of 315 mm. and a thickness of 2 mm.
These propellers were most accurately balanced and tested in every
particular; each propeller blade was balanced in weight with its mate and
the pitch measured at every point along the radius to insure its constancy;
finally the two propellers of the pair to be used together were balanced with
each other so that there would be no disturbance in the equilibrium of the
machine. As will be noted from the foregoing description of the machinery,
the propellers ran in opposite directions, as they were made right- and left-
hand screws. The weight of each propeller was 362 grammes.
We now turn again to take up the details of the construction of the
framework by which this propelling machinery is carried. The whole
aerodrome, as clearly shown in the photographs, Plates 27A and 27B, is
built about and dependent from one main backbone or midrod, which
having an axial hole 4 mm. in diameter drilled through them. The propeller
seat has a length of 43 mm. and the propeller is held in position by a collar
25 mm. in diameter at the front end, from which there project two dowel-
pins that fit into corresponding holes in the hubs of the propellers, which
are held up against the collar by a smaller one screwed into the back end of
the shaft. The thrust of the collar is taken up by a pin screwed into the end
of the forward box and acting as a step against which the shaft bears, the
arrangement being clearly shown by the accompanying drawing, Plate 26A.
[p118]
This, then, comprises the motive power equipment of the aerodrome,
and, to recapitulate, it includes the storage, automatic feeding and
regulation of the fuel; the storage, circulation and evaporation of the water;
the engine to convert the expansive power of the steam into mechanical
work; and the shafting for the transmission of the energy developed by the
engine to the propellers.
The propellers were made with the greatest care. Those used in the
successful trials were 1 metre in diameter, with an actual axial pitch of 1.25
metres. They were made of white pine, glued together in strips 7 mm. thick.
The hub had a length of 45 mm. and a thickness or diameter of 25 mm. At
the outer edge the blade had a width of 315 mm. and a thickness of 2 mm.
These propellers were most accurately balanced and tested in every
particular; each propeller blade was balanced in weight with its mate and
the pitch measured at every point along the radius to insure its constancy;
finally the two propellers of the pair to be used together were balanced with
each other so that there would be no disturbance in the equilibrium of the
machine. As will be noted from the foregoing description of the machinery,
the propellers ran in opposite directions, as they were made right- and left-
hand screws. The weight of each propeller was 362 grammes.
We now turn again to take up the details of the construction of the
framework by which this propelling machinery is carried. The whole
aerodrome, as clearly shown in the photographs, Plates 27A and 27B, is
built about and dependent from one main backbone or midrod, which
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extends well forward of all of the machinery and aft beyond all other parts.
This rod, as well as all other portions of the framework, is of steel tubing.
The midrod, being largest, is 20 mm outside diameter, with a thickness of
0.5 mm. It is to this midrod that the wings are directly attached, and from it
the hull containing the machinery is suspended.
The plan outline of the hull skeleton is similar to that of the deck of a
vessel. The steel tubing, 0.5 mm. thick, of which it is formed, has an outside
diameter of 15 mm. from the front end to the cross-framing used to carry
the propellers, back of which the diameter is decreased to 10 mm.
The midrod makes a slight angle with this frame, the vertical distance
between the centers of the tubing being 73 mm. at the front and 67 mm. at
the back. The tube, corresponding to the keel of a vessel, is braced to the
upper tubes by light U-shaped ribs and by two 8-mm. tubes forming a V
brace on a line with the back end of the guides of the engine. At the extreme
front and back there is a direct vertical connection to the midrod.
The propeller shafts are 1.23 m. from center to center, and are carried on
a special cross-framing, partaking, as already stated, of the character of an
outrigger on a row-boat. (See Plate 27B.) The rear rods, which are of 10
mm. steel tubing, start from the front end of the rear bearings of the
propeller shaft and [p119] extend across from side to side. The top rod is
brazed to the side pieces of the hull and the bottom rod to the keel. They are
connected by a vertical strut of 8-mm. tubing at a distance of 265 mm.
inside of each propeller shaft. At the front end of the propeller shaft two
more rods run across the frame. The lower is similar and parallel to the back
rod already described, while the upper is bowed to the front, as shown in
the plan view of the frame (Plate 30). In order to take the forward thrust of
the propeller a second cross-brace is inserted, which runs from the rear
bearing of the propeller shaft to a point just in advance of the front head of
the cylinder, and is brazed to the two upper tubes of the cross-frame as well
as to the upper tubes of the main framing of the hull. The outer ends of the
tubes of the cross-framing are brazed to a thin, stamped steel plate which
firmly binds them together, while at the same time it forms a base for
This rod, as well as all other portions of the framework, is of steel tubing.
The midrod, being largest, is 20 mm outside diameter, with a thickness of
0.5 mm. It is to this midrod that the wings are directly attached, and from it
the hull containing the machinery is suspended.
The plan outline of the hull skeleton is similar to that of the deck of a
vessel. The steel tubing, 0.5 mm. thick, of which it is formed, has an outside
diameter of 15 mm. from the front end to the cross-framing used to carry
the propellers, back of which the diameter is decreased to 10 mm.
The midrod makes a slight angle with this frame, the vertical distance
between the centers of the tubing being 73 mm. at the front and 67 mm. at
the back. The tube, corresponding to the keel of a vessel, is braced to the
upper tubes by light U-shaped ribs and by two 8-mm. tubes forming a V
brace on a line with the back end of the guides of the engine. At the extreme
front and back there is a direct vertical connection to the midrod.
The propeller shafts are 1.23 m. from center to center, and are carried on
a special cross-framing, partaking, as already stated, of the character of an
outrigger on a row-boat. (See Plate 27B.) The rear rods, which are of 10
mm. steel tubing, start from the front end of the rear bearings of the
propeller shaft and [p119] extend across from side to side. The top rod is
brazed to the side pieces of the hull and the bottom rod to the keel. They are
connected by a vertical strut of 8-mm. tubing at a distance of 265 mm.
inside of each propeller shaft. At the front end of the propeller shaft two
more rods run across the frame. The lower is similar and parallel to the back
rod already described, while the upper is bowed to the front, as shown in
the plan view of the frame (Plate 30). In order to take the forward thrust of
the propeller a second cross-brace is inserted, which runs from the rear
bearing of the propeller shaft to a point just in advance of the front head of
the cylinder, and is brazed to the two upper tubes of the cross-frame as well
as to the upper tubes of the main framing of the hull. The outer ends of the
tubes of the cross-framing are brazed to a thin, stamped steel plate which
firmly binds them together, while at the same time it forms a base for
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attaching the bearings of the propeller shaft. This end plate has a thickness
of one millimetre.
In addition to the framing proper there are two guy-posts which fit into
the sockets CC, and over which truss wires are drawn, as shown in the side
view in Plate 27A. These posts have a length of 730 mm. from the lower
edge of the socket, and are capped at their lower extremity by a light steel
ferrule whose outside diameter is 10 mm.
From the drawing of the wings of No. 5, shown in Plate 17, it will be
seen that they are formed of two pine rods 15 mm. in diameter at the inner
ends, tapering to a half circle of the same diameter at the tips. These rods
are connected by eleven spruce ribs measuring 8 mm. × 3 mm., and curved,
as shown in the side elevation, these, in turn, being covered by a light white
silk drawn so tightly as to present a smooth, even surface. The total length
of the wing is 2 metres, and the width over all is 805 mm. Vertical stiffness
is obtained in the wings by a series of guy-wires, which pass over light
struts resting upon the main rods. These main rods are inserted and held in
the wing clamps A and B, Fig. 16, and make an angle of 150° with each
other. As is the case with all other essential details of the aerodrome, a great
deal of time and attention was given to the designing of the wing clamps
before a satisfactory arrangement was secured.
To enable it to control the aerodrome in both directions, the tail-rudder,
Plate 27A, has both a horizontal and a vertical surface, the approximate
dimensions of which are, length 115 cm. (3.8 feet), maximum width 64 cm.
(2.1 feet), giving each quarter section an area of about 0.64 sq. m. (6.9 sq.
ft.). It is given the proper angle and degree of elasticity in a vertical
direction by the flat hickory spring, which fits into the clamp N, and
attaches the rudder to the frame.
The only other attachments of the aerodrome are the reel, float, and
counter. They have nothing whatever to do with the flying of the machine,
and are [p120] merely safety appliances to insure its recovery from the water.
The reel consists of a light spool on which a fine cord is wound, one end of
which is attached to a light float that detaches itself and lies upon the
surface of the water when the machine sinks, while the other end is fastened
of one millimetre.
In addition to the framing proper there are two guy-posts which fit into
the sockets CC, and over which truss wires are drawn, as shown in the side
view in Plate 27A. These posts have a length of 730 mm. from the lower
edge of the socket, and are capped at their lower extremity by a light steel
ferrule whose outside diameter is 10 mm.
From the drawing of the wings of No. 5, shown in Plate 17, it will be
seen that they are formed of two pine rods 15 mm. in diameter at the inner
ends, tapering to a half circle of the same diameter at the tips. These rods
are connected by eleven spruce ribs measuring 8 mm. × 3 mm., and curved,
as shown in the side elevation, these, in turn, being covered by a light white
silk drawn so tightly as to present a smooth, even surface. The total length
of the wing is 2 metres, and the width over all is 805 mm. Vertical stiffness
is obtained in the wings by a series of guy-wires, which pass over light
struts resting upon the main rods. These main rods are inserted and held in
the wing clamps A and B, Fig. 16, and make an angle of 150° with each
other. As is the case with all other essential details of the aerodrome, a great
deal of time and attention was given to the designing of the wing clamps
before a satisfactory arrangement was secured.
To enable it to control the aerodrome in both directions, the tail-rudder,
Plate 27A, has both a horizontal and a vertical surface, the approximate
dimensions of which are, length 115 cm. (3.8 feet), maximum width 64 cm.
(2.1 feet), giving each quarter section an area of about 0.64 sq. m. (6.9 sq.
ft.). It is given the proper angle and degree of elasticity in a vertical
direction by the flat hickory spring, which fits into the clamp N, and
attaches the rudder to the frame.
The only other attachments of the aerodrome are the reel, float, and
counter. They have nothing whatever to do with the flying of the machine,
and are [p120] merely safety appliances to insure its recovery from the water.
The reel consists of a light spool on which a fine cord is wound, one end of
which is attached to a light float that detaches itself and lies upon the
surface of the water when the machine sinks, while the other end is fastened
Page 209
to the spool that goes down with the aerodrome. The “float” is a light
copper vessel with conical ends which is firmly fastened to the midrod, and
which is intended to so lower the specific gravity of the whole machine that
it will not sink. The cylindrical portion of this float has a length of 250 mm.
and a diameter of 170 mm., one cone having a length of 65 mm. and the
other and front one a length of 140 mm., which makes the total length of the
float 375 mm. It is made of very thin copper, and served in the successful
trials not only as a float to sustain the machine on the surface of the water,
but also as a weight by which the center of gravity was so adjusted that
flight was possible.
The counter records the number of revolutions of the propellers after
launching. It is a small dial counter, reading to 10,000, with a special
attachment which prevents any record being made of the revolutions of the
propellers, until the actual moment of launching, when a piece on the
launching apparatus throws the counter in gear at the instant that the
aerodrome leaps into the air.
D ESCRIPTION OF A ERODROME N O. 6
Aerodrome No. 6, it will be remembered, was the outgrowth of a number
of changes made in No. 4 during the fall of 1895 and the early part of 1896.
In this reconstruction the aim was to lighten the whole machine on account
of the smaller engines in either No. 4 or No. 5. The modifications from No.
4 were so radical and the differences that exist between Nos. 5 and 6 are so
considerable as to demand careful attention.
As regards general appearance the frame of Aerodrome No. 6 resembles
that of No. 5 in consisting of a single continuous midrod of steel tubing, 20
mm. in diameter, 0.5 mm. thick, immediately beneath which the hull
containing the machinery is situated. In reconstructing the framework after
the tests in January, 1896, had shown it to be dangerously weak, especially
against torsion, it was decided to make the hull only strong enough to carry
its contents and to attach it to the stronger midrod in such a way that all
torsional strains would be taken up by it, whereas in No. 5 the hull structure
must bear a large proportion of such strains. It was therefore built
copper vessel with conical ends which is firmly fastened to the midrod, and
which is intended to so lower the specific gravity of the whole machine that
it will not sink. The cylindrical portion of this float has a length of 250 mm.
and a diameter of 170 mm., one cone having a length of 65 mm. and the
other and front one a length of 140 mm., which makes the total length of the
float 375 mm. It is made of very thin copper, and served in the successful
trials not only as a float to sustain the machine on the surface of the water,
but also as a weight by which the center of gravity was so adjusted that
flight was possible.
The counter records the number of revolutions of the propellers after
launching. It is a small dial counter, reading to 10,000, with a special
attachment which prevents any record being made of the revolutions of the
propellers, until the actual moment of launching, when a piece on the
launching apparatus throws the counter in gear at the instant that the
aerodrome leaps into the air.
D ESCRIPTION OF A ERODROME N O. 6
Aerodrome No. 6, it will be remembered, was the outgrowth of a number
of changes made in No. 4 during the fall of 1895 and the early part of 1896.
In this reconstruction the aim was to lighten the whole machine on account
of the smaller engines in either No. 4 or No. 5. The modifications from No.
4 were so radical and the differences that exist between Nos. 5 and 6 are so
considerable as to demand careful attention.
As regards general appearance the frame of Aerodrome No. 6 resembles
that of No. 5 in consisting of a single continuous midrod of steel tubing, 20
mm. in diameter, 0.5 mm. thick, immediately beneath which the hull
containing the machinery is situated. In reconstructing the framework after
the tests in January, 1896, had shown it to be dangerously weak, especially
against torsion, it was decided to make the hull only strong enough to carry
its contents and to attach it to the stronger midrod in such a way that all
torsional strains would be taken up by it, whereas in No. 5 the hull structure
must bear a large proportion of such strains. It was therefore built
Page 210
throughout of 8-mm. tubing, 0.3 mm. thick, and was rigidly attached to the
midrod by braces at the front and rear, and also at the cross-frame. The hull
was also made narrower (except at the rear, where it was widened to contain
the boiler) and shorter than the hull of No. 5—an advantageous change
made possible by the fact that the engines were not contained in the hull,
but mounted on the transverse frame.
midrod by braces at the front and rear, and also at the cross-frame. The hull
was also made narrower (except at the rear, where it was widened to contain
the boiler) and shorter than the hull of No. 5—an advantageous change
made possible by the fact that the engines were not contained in the hull,
but mounted on the transverse frame.
Page 211
PL. 28. STEEL FRAME OF AERODROME NO. 6, ON
LAUNCHING CAR ◊ lgr
LAUNCHING CAR ◊ lgr
Page 212
[p121]
In No. 5, as described above, a single engine mounted at the front end of
the hull communicated its power through transmission shafts and gearing to
the propellers, which were necessarily in the same plane. This brought the
line of thrust very nearly in the same plane as the center of gravity of the
aerodrome, a condition tending to promote instability of longitudinal
equilibrium. In No. 6, however, the use of two engines situated on the
transverse frame and communicating their power directly to the propellers,
made it possible to raise the transverse frame 12 cm. above the hull, and
thus raise the line of thrust to a position intermediate between the center of
pressure and the center of gravity, without materially affecting the latter. As
a result of this change Aerodrome No. 6 was rendered much more stable
and made steadier flights with fewer undulations than No. 5.
The engines in use on No. 6 were the small engines described above in
connection with No. 4. The cylinders were of steel tubing 2.8 cm. in
diameter, with a 5-cm. stroke, each cylinder thus having a capacity of 30.8
cc. They were lined with a thin cast-iron bushing and cast-iron rings were
sprung in the piston head so as to give as smooth a rubbing surface and as
perfect action as possible. As in the engine of No. 5 a plain sliding valve of
the piston type was used, cut-off being approximately at one-half, though
the ports were so small that it was difficult to determine it with any great
accuracy. No packing was used, but the parts were carefully ground so as to
give a perfect fit.
These engines, as is most clearly shown in Plate 30, were mounted
symmetrically on either side of the cross-frame and were connected directly
to the propeller shafts. In order to insure that the propellers would run at the
same rate, there was provided a synchronizing shaft, T, in Plate 30, having
on each end a bevel gear, which intermeshed with similar gears on the
propeller shafts. Steam for the cylinders was conveyed from the separator
through the pipes LL.
The steam-generating apparatus for No. 6 was exactly like that already
described in connection with No. 5, the only difference being in the more
compact arrangement in the case of No. 6. The relative location of the
In No. 5, as described above, a single engine mounted at the front end of
the hull communicated its power through transmission shafts and gearing to
the propellers, which were necessarily in the same plane. This brought the
line of thrust very nearly in the same plane as the center of gravity of the
aerodrome, a condition tending to promote instability of longitudinal
equilibrium. In No. 6, however, the use of two engines situated on the
transverse frame and communicating their power directly to the propellers,
made it possible to raise the transverse frame 12 cm. above the hull, and
thus raise the line of thrust to a position intermediate between the center of
pressure and the center of gravity, without materially affecting the latter. As
a result of this change Aerodrome No. 6 was rendered much more stable
and made steadier flights with fewer undulations than No. 5.
The engines in use on No. 6 were the small engines described above in
connection with No. 4. The cylinders were of steel tubing 2.8 cm. in
diameter, with a 5-cm. stroke, each cylinder thus having a capacity of 30.8
cc. They were lined with a thin cast-iron bushing and cast-iron rings were
sprung in the piston head so as to give as smooth a rubbing surface and as
perfect action as possible. As in the engine of No. 5 a plain sliding valve of
the piston type was used, cut-off being approximately at one-half, though
the ports were so small that it was difficult to determine it with any great
accuracy. No packing was used, but the parts were carefully ground so as to
give a perfect fit.
These engines, as is most clearly shown in Plate 30, were mounted
symmetrically on either side of the cross-frame and were connected directly
to the propeller shafts. In order to insure that the propellers would run at the
same rate, there was provided a synchronizing shaft, T, in Plate 30, having
on each end a bevel gear, which intermeshed with similar gears on the
propeller shafts. Steam for the cylinders was conveyed from the separator
through the pipes LL.
The steam-generating apparatus for No. 6 was exactly like that already
described in connection with No. 5, the only difference being in the more
compact arrangement in the case of No. 6. The relative location of the
Page 213
apparatus in the two models is clearly shown in Plates 28, 29B, and 30, the
corresponding parts being similarly labeled, so that a separate description
for No. 6 is superfluous.
The wings used on No. 6 were somewhat smaller than those of No. 5, and
differed from them in having the front mainrib bent to a quadrant at its outer
extremity and continued as the outer rib of the wing. The degree of
curvature of the wings was also somewhat less, being one-eighteenth for
No. 6 and one-twelfth for No. 5. The four wings were of the same size and
had a total area of 54 sq. ft. On account of the shortened hull of No. 6 they
were allowed a much greater range of adjustment, which rendered it much
easier to bring the CP into the proper relative position to the CG than was
the ease with No. 5. [p122]
The Pénaud rudder for No. 6 was similar to that for No. 5, the two in fact
being interchangeable, and was similarly attached to the frame. The reel,
float, counter, and all other accessories were identical for the two machines.
To sum up the comparative features of these two successful steam-driven
models: Aerodrome No. 6 was both lighter and frailer than No. 5, and
required much more delicate adjustment, but when the correct adjustments
had been made its flying qualities were superior, as regards both speed and
stability.
corresponding parts being similarly labeled, so that a separate description
for No. 6 is superfluous.
The wings used on No. 6 were somewhat smaller than those of No. 5, and
differed from them in having the front mainrib bent to a quadrant at its outer
extremity and continued as the outer rib of the wing. The degree of
curvature of the wings was also somewhat less, being one-eighteenth for
No. 6 and one-twelfth for No. 5. The four wings were of the same size and
had a total area of 54 sq. ft. On account of the shortened hull of No. 6 they
were allowed a much greater range of adjustment, which rendered it much
easier to bring the CP into the proper relative position to the CG than was
the ease with No. 5. [p122]
The Pénaud rudder for No. 6 was similar to that for No. 5, the two in fact
being interchangeable, and was similarly attached to the frame. The reel,
float, counter, and all other accessories were identical for the two machines.
To sum up the comparative features of these two successful steam-driven
models: Aerodrome No. 6 was both lighter and frailer than No. 5, and
required much more delicate adjustment, but when the correct adjustments
had been made its flying qualities were superior, as regards both speed and
stability.
Page 214
PL. 29A. PLAN VIEW OF AERODROME NO. 6. OCTOBER 23, 1896 ◊
Page 215
PL. 29B. SIDE ELEVATION OF AERODROME NO. 6.
OCTOBER 23, 1896. ◊
OCTOBER 23, 1896. ◊
Page 216
PL. 30. PLAN VIEW OF STEEL FRAMES AND POWER PLANTS OF
AERODROMES NOS. 5, 6 ◊ lgr
AERODROMES NOS. 5, 6 ◊ lgr
Page 217
PL. 31. DETAILS OF AERODROME NO. 5 ◊ lgr
Page 218
FOOTNOTES.
[2] “Experiments in Aerodynamics,” Smithsonian Contributions to Knowledge, Vol. 27,
1891.
[3] This chapter was written almost entirely by Mr. Langley in 1897.
[4] 1897.
[5] In this statement, of course, no account is taken of the “internal work of the wind.”
[6] Ten years prior to 1897.
[7] Communication to the French Academy. Extract from the Comptes Rendus of the
Sessions of the Academy of Sciences, Vol. 122, Session of May 26, 1896.
(Translation.)
A Description of Mechanical Flight. By S. P. Langley.
In a communication which I addressed to the Academy in July, 1891, I remarked that the results
of experimental investigation had shown the possibility of constructing machines which could give
such a horizontal velocity to bodies resembling in shape inclined planes, and more than a thousand
times heavier than air, that these could be sustained on this element.
While I have elsewhere remarked that surfaces other than planes might give better results, and
that absolutely horizontal flight, which is so desirable in theory, is hardly realizable in practice, so
far as I know there has never been constructed, up to the present time, any heavy aerodrome, or so-
called flying-machine, which can keep itself freely in the air by its own force more than a few
seconds, the difficulties encountered in absolutely free flight being, for many reasons,
immeasurably greater than those experienced when the flight is controlled by the body’s pressing
upward against a horizontal track, or whirling-arm. No one is unaware that many experimenters
have been engaged in trying to execute free mechanical flight, and although the demonstration
which I furnished in 1891 [“Experiments in Aerodynamics,” 1891] of its theoretical possibility
with means then at our disposition, seemed conclusive, so long a time has elapsed without
practical results, that it might be doubted whether these theoretical conditions are to be realized. I
have thought it well, then, to occupy myself with the construction of an aerodrome with which I
might put my previous conclusions to the test of experiment.
The Academy will, perhaps, find it interesting to read the narrative given here by an eye-
witness, who is well known to it. I am led to present it not only by the request with which he
honors me, but by the apprehension that my administrative duties may put a stop to these
researches, so that it seems to me advisable to announce the degree in which I have already
succeeded, although this success be not as complete as I should like to make it.
The experiments took place on a bay of the Potomac River, some distance below Washington.
The aerodrome was built chiefly of steel, though lighter material entered into the construction, so
that its density as a whole was a little below unity. No gas whatever entered into the construction
of the machine, and the absolute weight, independent of fuel and water, was about 11 kilos (24
pounds). The width of the supporting surfaces was about 4 metres (13 feet), and the power was
furnished by an extremely light engine of approximately one horse-power. There was no one to
direct it on board, and the means for keeping it automatically in horizontal flight were not
complete. It is important to remark that the small dimensions of the machine did not allow it to
[2] “Experiments in Aerodynamics,” Smithsonian Contributions to Knowledge, Vol. 27,
1891.
[3] This chapter was written almost entirely by Mr. Langley in 1897.
[4] 1897.
[5] In this statement, of course, no account is taken of the “internal work of the wind.”
[6] Ten years prior to 1897.
[7] Communication to the French Academy. Extract from the Comptes Rendus of the
Sessions of the Academy of Sciences, Vol. 122, Session of May 26, 1896.
(Translation.)
A Description of Mechanical Flight. By S. P. Langley.
In a communication which I addressed to the Academy in July, 1891, I remarked that the results
of experimental investigation had shown the possibility of constructing machines which could give
such a horizontal velocity to bodies resembling in shape inclined planes, and more than a thousand
times heavier than air, that these could be sustained on this element.
While I have elsewhere remarked that surfaces other than planes might give better results, and
that absolutely horizontal flight, which is so desirable in theory, is hardly realizable in practice, so
far as I know there has never been constructed, up to the present time, any heavy aerodrome, or so-
called flying-machine, which can keep itself freely in the air by its own force more than a few
seconds, the difficulties encountered in absolutely free flight being, for many reasons,
immeasurably greater than those experienced when the flight is controlled by the body’s pressing
upward against a horizontal track, or whirling-arm. No one is unaware that many experimenters
have been engaged in trying to execute free mechanical flight, and although the demonstration
which I furnished in 1891 [“Experiments in Aerodynamics,” 1891] of its theoretical possibility
with means then at our disposition, seemed conclusive, so long a time has elapsed without
practical results, that it might be doubted whether these theoretical conditions are to be realized. I
have thought it well, then, to occupy myself with the construction of an aerodrome with which I
might put my previous conclusions to the test of experiment.
The Academy will, perhaps, find it interesting to read the narrative given here by an eye-
witness, who is well known to it. I am led to present it not only by the request with which he
honors me, but by the apprehension that my administrative duties may put a stop to these
researches, so that it seems to me advisable to announce the degree in which I have already
succeeded, although this success be not as complete as I should like to make it.
The experiments took place on a bay of the Potomac River, some distance below Washington.
The aerodrome was built chiefly of steel, though lighter material entered into the construction, so
that its density as a whole was a little below unity. No gas whatever entered into the construction
of the machine, and the absolute weight, independent of fuel and water, was about 11 kilos (24
pounds). The width of the supporting surfaces was about 4 metres (13 feet), and the power was
furnished by an extremely light engine of approximately one horse-power. There was no one to
direct it on board, and the means for keeping it automatically in horizontal flight were not
complete. It is important to remark that the small dimensions of the machine did not allow it to
Page 219
include any apparatus for condensing the steam, so that it could only carry water enough for a very
brief course—a drawback which would not be encountered in one of a larger construction.
It is also to be noted that the speed estimated by Mr. Bell was that obtained in a continuous
ascending flight, and much less than would have been attained in a horizontal course.
On Mechanical Flight. Letter of Mr. Alexander Graham Bell to Mr. Langley.
Washington, May 6, 1896.
I am quite aware that you are not desirous of publication until you have attained more complete
success in obtaining horizontal flight under an automatic direction, but it seems that what I have
been privileged to see to-day marks such a great progress on everything ever before done in this
way, that the news of it should be made public, and I am happy to give my own testimony on the
results of two trials which I have witnessed to-day by your invitation, hoping that you will kindly
consent to making it known.
For the first trial, the apparatus, chiefly constructed of steel and driven by a steam engine, was
launched from a boat at a height of about 20 feet from the water. Under the impulse of its engines
alone, it advanced against the wind and while drifting little, and slowly ascending with a
remarkably uniform motion, it described curves of about 100 metres in diameter; till at a height in
the air which I estimate at about 25 metres (82 feet), the revolutions of the screws ceased for want
of steam, as I understood, and the apparatus descended gently and sank into the water, which it
reached in a minute and a half from the start. It was not damaged, and was immediately ready for
another flight.
In the second trial it repeated in nearly every respect the action of the first, and with an identical
result. It rose smoothly in great curves until it approached a prominent wooded promontory, which
it crossed at a height of 8 to 10 metres above the tops of the highest trees, upon the exhaustion of
the steam descending slowly into the bay, where it settled in a minute and thirty-one seconds from
the start. You have an instantaneous photograph of it, which I took just after the launch. [See plates
20, 21, and 22 of present work.]
From the extent of the curves which it described, which I estimated with other persons, from
measurements which I took, and from the number of revolutions of the propellers, as recorded by
the automatic counter which I consulted, I estimate the absolute length of each course to be over
half an English mile, or, more exactly a little over 900 metres (2953 feet).
The duration of flight during the second trial was one minute and thirty-one seconds, and the
average velocity between twenty and twenty-five miles an hour, or, let us say 10 metres a second,
in a course which was constantly ascending. I was extremely impressed by the easy regular course
of each trial, and by the fact that the apparatus descended each time with such smoothness and
gentleness as to render any jar or danger out of the question.
It seemed to me that no one could have witnessed these experiments without being convinced
that the possibility of mechanical flight had been demonstrated.
[8] It is desirable that the reader should be acquainted with the contents of this treatise, and
of another by me, entitled “The Internal Work of the Wind,” both published by the Smithsonian
Institution. A knowledge of these works is not absolutely necessary, but of advantage in connection
with what follows.
[9] “Experiments in Aerodynamics,” p. 107.
[10] Chapter VIII ◊.
[11] His device for obtaining automatic equilibrium is found in connection with the
description of his “Aeroplane Auto Moteur,” in “L’Aeronaute” for January, 1872.
brief course—a drawback which would not be encountered in one of a larger construction.
It is also to be noted that the speed estimated by Mr. Bell was that obtained in a continuous
ascending flight, and much less than would have been attained in a horizontal course.
On Mechanical Flight. Letter of Mr. Alexander Graham Bell to Mr. Langley.
Washington, May 6, 1896.
I am quite aware that you are not desirous of publication until you have attained more complete
success in obtaining horizontal flight under an automatic direction, but it seems that what I have
been privileged to see to-day marks such a great progress on everything ever before done in this
way, that the news of it should be made public, and I am happy to give my own testimony on the
results of two trials which I have witnessed to-day by your invitation, hoping that you will kindly
consent to making it known.
For the first trial, the apparatus, chiefly constructed of steel and driven by a steam engine, was
launched from a boat at a height of about 20 feet from the water. Under the impulse of its engines
alone, it advanced against the wind and while drifting little, and slowly ascending with a
remarkably uniform motion, it described curves of about 100 metres in diameter; till at a height in
the air which I estimate at about 25 metres (82 feet), the revolutions of the screws ceased for want
of steam, as I understood, and the apparatus descended gently and sank into the water, which it
reached in a minute and a half from the start. It was not damaged, and was immediately ready for
another flight.
In the second trial it repeated in nearly every respect the action of the first, and with an identical
result. It rose smoothly in great curves until it approached a prominent wooded promontory, which
it crossed at a height of 8 to 10 metres above the tops of the highest trees, upon the exhaustion of
the steam descending slowly into the bay, where it settled in a minute and thirty-one seconds from
the start. You have an instantaneous photograph of it, which I took just after the launch. [See plates
20, 21, and 22 of present work.]
From the extent of the curves which it described, which I estimated with other persons, from
measurements which I took, and from the number of revolutions of the propellers, as recorded by
the automatic counter which I consulted, I estimate the absolute length of each course to be over
half an English mile, or, more exactly a little over 900 metres (2953 feet).
The duration of flight during the second trial was one minute and thirty-one seconds, and the
average velocity between twenty and twenty-five miles an hour, or, let us say 10 metres a second,
in a course which was constantly ascending. I was extremely impressed by the easy regular course
of each trial, and by the fact that the apparatus descended each time with such smoothness and
gentleness as to render any jar or danger out of the question.
It seemed to me that no one could have witnessed these experiments without being convinced
that the possibility of mechanical flight had been demonstrated.
[8] It is desirable that the reader should be acquainted with the contents of this treatise, and
of another by me, entitled “The Internal Work of the Wind,” both published by the Smithsonian
Institution. A knowledge of these works is not absolutely necessary, but of advantage in connection
with what follows.
[9] “Experiments in Aerodynamics,” p. 107.
[10] Chapter VIII ◊.
[11] His device for obtaining automatic equilibrium is found in connection with the
description of his “Aeroplane Auto Moteur,” in “L’Aeronaute” for January, 1872.
Page 220
[12] I have never obtained so good a result as this with any rubber motor. S. P. Langley.
[13] One pound of twisted rubber appears, from my experiments, to be capable of
momentarily yielding nearly 600 foot-pounds of energy, but this effect is attained only by twisting
it too far. It will be safer to take at most 300 foot-pounds, and as the strain must be taken up by a
tube or frame weighing at least as much as the rubber, we have approximately 0.0091 as the horse-
power for one minute, or 0.091 horse-power for six seconds as the maximum effect, in continuous
work, of a pound of twisted rubber strands. The longitudinal pull of the rubber is much greater, but
it is difficult to employ it in this way for models, owing to the great relative weight of the tube or
frame needed to bear the bending strain. In either form, rubber is far more effective for the weight
than any steel spring (see later chapter on Available Motors).
[14] The aerodrome is sustained by the upward pressure of the air, which must be replaceable
by the resultant pressure at some particular point, designated by CP.
[15] See Century Magazine, October, 1891.
[16] Subsequent observations indicate that the maximum velocity of horizontal flight must
have been about 10 metres per second.
[17] Observers following de Lucy have long since called attention to the fact that as the scale
of Nature’s flying things increases, the size of the sustaining surfaces diminishes relatively to the
weight sustained. M. Harting (Aeronautical Society, 1870) has shown that the relation
√area/ weight is surprisingly constant when bats varying in weight as much as 250 times are the
subject of the experiment, and later observations by Marey have not materially affected the
statement. As to the muscular power which Nature has imparted with the greater or lesser weight,
this varies, decreasing very rapidly as the weight increases. The same remark may be made
apparently with at least approximate truth, with regard to the soaring bird, and the important
inference is that if there be any analogy between the bird and the aerodrome, as the scale of the
construction of the latter increases, it may be reasonably anticipated that the size of the sustaining
surfaces will relatively diminish rather than increase. We may conveniently use M. Harting’s
l2
formula in the form a = n 2w (2/3) = 2 where a = area in sq. cm., w the weight in grammes, l the
m
length of the wing in cm., n and m constants derived from observation.
[18] A singular fact connected with the stretching of rubber is that the extension is not only not
directly proportional to the power producing it, but that up to a certain limit it increases more
rapidly than the power, and after this the relation becomes for a time more nearly constant, and
after this again the extension becomes less and less in proportion.
In other words, if a curve be constructed whose abscissae represent extensions, and ordinates the
corresponding weights, it will show a reverse curvature, one portion being concave toward the axis
of abscissae, the other convex.
[19] The following table taken from “Experiments in Aerodynamics,” p. 107, gives the data
for soaring of 30 × 4.8 inch planes, weight 500 grammes.
[13] One pound of twisted rubber appears, from my experiments, to be capable of
momentarily yielding nearly 600 foot-pounds of energy, but this effect is attained only by twisting
it too far. It will be safer to take at most 300 foot-pounds, and as the strain must be taken up by a
tube or frame weighing at least as much as the rubber, we have approximately 0.0091 as the horse-
power for one minute, or 0.091 horse-power for six seconds as the maximum effect, in continuous
work, of a pound of twisted rubber strands. The longitudinal pull of the rubber is much greater, but
it is difficult to employ it in this way for models, owing to the great relative weight of the tube or
frame needed to bear the bending strain. In either form, rubber is far more effective for the weight
than any steel spring (see later chapter on Available Motors).
[14] The aerodrome is sustained by the upward pressure of the air, which must be replaceable
by the resultant pressure at some particular point, designated by CP.
[15] See Century Magazine, October, 1891.
[16] Subsequent observations indicate that the maximum velocity of horizontal flight must
have been about 10 metres per second.
[17] Observers following de Lucy have long since called attention to the fact that as the scale
of Nature’s flying things increases, the size of the sustaining surfaces diminishes relatively to the
weight sustained. M. Harting (Aeronautical Society, 1870) has shown that the relation
√area/ weight is surprisingly constant when bats varying in weight as much as 250 times are the
subject of the experiment, and later observations by Marey have not materially affected the
statement. As to the muscular power which Nature has imparted with the greater or lesser weight,
this varies, decreasing very rapidly as the weight increases. The same remark may be made
apparently with at least approximate truth, with regard to the soaring bird, and the important
inference is that if there be any analogy between the bird and the aerodrome, as the scale of the
construction of the latter increases, it may be reasonably anticipated that the size of the sustaining
surfaces will relatively diminish rather than increase. We may conveniently use M. Harting’s
l2
formula in the form a = n 2w (2/3) = 2 where a = area in sq. cm., w the weight in grammes, l the
m
length of the wing in cm., n and m constants derived from observation.
[18] A singular fact connected with the stretching of rubber is that the extension is not only not
directly proportional to the power producing it, but that up to a certain limit it increases more
rapidly than the power, and after this the relation becomes for a time more nearly constant, and
after this again the extension becomes less and less in proportion.
In other words, if a curve be constructed whose abscissae represent extensions, and ordinates the
corresponding weights, it will show a reverse curvature, one portion being concave toward the axis
of abscissae, the other convex.
[19] The following table taken from “Experiments in Aerodynamics,” p. 107, gives the data
for soaring of 30 × 4.8 inch planes, weight 500 grammes.
Page 221
Weight with planes of like form that 1
Work expended per
Soaring speed V. horse-power will drive through the air
minute.
Angle with at velocity V.
horizon α. Metres
Feet per Kilogram- Foot-
per Kilogrammes. Pounds.
second. metres. pounds.
second.
45° 11.2 36.7 336 2,434 6.8 15
30 10.6 34.8 175 1,268 13.0 29
15 11.2 36.7 86 623 26.5 58
10 12.4 40.7 65 474 34.8 77
5 15.2 49.8 41 297 55.5 122
2 20.0 65.6 24 174 95.0 209
The relations shown in the above table hold true only in case of planes supporting about 1.1
pounds to each square foot of sustaining area. For a different proportion of area to weight, other
conditions would obtain.
[20] This pressure per unit of area varies with the area itself, but in a degree which is
negligible for our immediate purpose.
[21] See “Internal Work of the Wind”; also Revue de L’Aeronautique, 3e Livraison, 1893.
[22] More recent experiments under my direction by Mr. Huffaker give similar results, but
confirm my earlier and cruder observations that the curve, used alone, for small angles, is much
more unstable than the plane.
[23] As stated in the Preface, Part III has not yet been prepared for publication.
[24] According to Wellner (“Zeitschrift für Luftschiffahrt,” Beilage, 1893), in a curved surface
with 1/12 rise, if the angle of inclination of the chord of the surface be α, and the angle between
the direction of resultant air pressure and the normal to the direction of motion be β, then β<α and
the soaring speed is
P 1
V = √( × )
K F (α)×cos β
while the efficiency is
W Weight
= = tan β
R Resistance
The following were derived from experiments in the wind:
α = −3° 0° +3° 6° 9° 12°
F (α) = 0.20 0.80 0.75 0.90 1.00 1.05
Tan β = 0.01 0.02 0.03 0.04 0.10 0.17
so that according to him, a curved surface shows finite soaring speeds when the angle of
inclination is 0° or even slightly negative.
[25] The following formulæ proposed by Mr. Chas. M. Manly show how the center of pressure
may be moved any desired distance either forward or backward without in any way affecting the
center of gravity, and by merely moving the front and rear wings the same amounts but in opposite
directions, the total movement of each wing being in either case five times the amount that is
Work expended per
Soaring speed V. horse-power will drive through the air
minute.
Angle with at velocity V.
horizon α. Metres
Feet per Kilogram- Foot-
per Kilogrammes. Pounds.
second. metres. pounds.
second.
45° 11.2 36.7 336 2,434 6.8 15
30 10.6 34.8 175 1,268 13.0 29
15 11.2 36.7 86 623 26.5 58
10 12.4 40.7 65 474 34.8 77
5 15.2 49.8 41 297 55.5 122
2 20.0 65.6 24 174 95.0 209
The relations shown in the above table hold true only in case of planes supporting about 1.1
pounds to each square foot of sustaining area. For a different proportion of area to weight, other
conditions would obtain.
[20] This pressure per unit of area varies with the area itself, but in a degree which is
negligible for our immediate purpose.
[21] See “Internal Work of the Wind”; also Revue de L’Aeronautique, 3e Livraison, 1893.
[22] More recent experiments under my direction by Mr. Huffaker give similar results, but
confirm my earlier and cruder observations that the curve, used alone, for small angles, is much
more unstable than the plane.
[23] As stated in the Preface, Part III has not yet been prepared for publication.
[24] According to Wellner (“Zeitschrift für Luftschiffahrt,” Beilage, 1893), in a curved surface
with 1/12 rise, if the angle of inclination of the chord of the surface be α, and the angle between
the direction of resultant air pressure and the normal to the direction of motion be β, then β<α and
the soaring speed is
P 1
V = √( × )
K F (α)×cos β
while the efficiency is
W Weight
= = tan β
R Resistance
The following were derived from experiments in the wind:
α = −3° 0° +3° 6° 9° 12°
F (α) = 0.20 0.80 0.75 0.90 1.00 1.05
Tan β = 0.01 0.02 0.03 0.04 0.10 0.17
so that according to him, a curved surface shows finite soaring speeds when the angle of
inclination is 0° or even slightly negative.
[25] The following formulæ proposed by Mr. Chas. M. Manly show how the center of pressure
may be moved any desired distance either forward or backward without in any way affecting the
center of gravity, and by merely moving the front and rear wings the same amounts but in opposite
directions, the total movement of each wing being in either case five times the amount that is
Page 222
desired to move the mean CP1, and the direction of movement of the front wing determining the
direction of movement of CP1.
In Figure 7, CPfw and CPrw are the centers of pressure of the front and rear wings respectively;
the weights of the wings, which are assumed to be equal and concentrated at their centers of figure,
are represented by w, w, and a is the distance of the center of pressure in either wing from its
center of figure. The original mean center of pressure of the aerodrome is CP1, W is the weight of
the aerodrome, supposed to be concentrated at CG1, while m is the distance from CPrw to CG1.
Now, if we have assumed that the rear wing, being of the same size as the front one, has a lifting
effect of only 0.66, and on this assumption is calculated the proper relative positions of the front
and rear wings to cause the CP1 to come directly over the CG1, and upon testing the aerodrome
find that it is too heavy in front and, therefore, wish to move the center of pressure forward an
amount, say b, without affecting the center of gravity, we can calculate the proper relative
positions of the front and rear wings in the following manner. While the aerodrome as a whole is
balanced at the point CG1, the weight of the wings is not balanced around this point, for the rear
wing, owing to its decreased lifting effect, is proportionately farther from CP1 than the front wing.
In order, therefore, to avoid moving the center of gravity of the machine as a whole, any
movement of the wings must be made in such a way as to cause the difference between the weight
of the rear wing multiplied by its distance from CG1 and the weight of the front multiplied by its
distance from CG1 to equal a constant: that is,
w (m + a )−w(0.66m−a ) = constant,
and
0.33wm + 2wa = constant.
F IG. 7.
F IG. 8. F IG. 9.
F IGS. 7–9. Diagrams Illustrating formulæ for moving C. P. without disturbing C. G.
direction of movement of CP1.
In Figure 7, CPfw and CPrw are the centers of pressure of the front and rear wings respectively;
the weights of the wings, which are assumed to be equal and concentrated at their centers of figure,
are represented by w, w, and a is the distance of the center of pressure in either wing from its
center of figure. The original mean center of pressure of the aerodrome is CP1, W is the weight of
the aerodrome, supposed to be concentrated at CG1, while m is the distance from CPrw to CG1.
Now, if we have assumed that the rear wing, being of the same size as the front one, has a lifting
effect of only 0.66, and on this assumption is calculated the proper relative positions of the front
and rear wings to cause the CP1 to come directly over the CG1, and upon testing the aerodrome
find that it is too heavy in front and, therefore, wish to move the center of pressure forward an
amount, say b, without affecting the center of gravity, we can calculate the proper relative
positions of the front and rear wings in the following manner. While the aerodrome as a whole is
balanced at the point CG1, the weight of the wings is not balanced around this point, for the rear
wing, owing to its decreased lifting effect, is proportionately farther from CP1 than the front wing.
In order, therefore, to avoid moving the center of gravity of the machine as a whole, any
movement of the wings must be made in such a way as to cause the difference between the weight
of the rear wing multiplied by its distance from CG1 and the weight of the front multiplied by its
distance from CG1 to equal a constant: that is,
w (m + a )−w(0.66m−a ) = constant,
and
0.33wm + 2wa = constant.
F IG. 7.
F IG. 8. F IG. 9.
F IGS. 7–9. Diagrams Illustrating formulæ for moving C. P. without disturbing C. G.
Page 223
If now the wings be moved so that CP1 is moved forward a distance b, we may indicate the
distance from CG1 to the new CPrw by z, and equating the difference between the weight of the
rear wing multiplied by its new distance from CG1 and the weight of the front wing multiplied by
its new distance from CG1 and making this difference equal to the constant difference, we can
calculate z in terms of m and b, as follows:
Fig. 8,
w (a + z )−w(0.66(z + b ) + b−a ) = 0.33wm + 2wa,
∴ z = m + 5b.
Knowing z, we readily find that the new distance from CPfw to CG1 equals:
0.66(z + b ) + b = 0.66m + 5b.
In a similar manner we may calculate the proper relative positions of the front and rear wings
when we wish to move the center of pressure backward a distance, b, from the original CP1
without changing the position of CG1. From Fig. 7, we have as before:
w (m + a )−w(0.66m−a ) = constant,
0.33wm + 2wa = constant.
Fig. 9,
w (z1 + a )−w(0.66(z1−b )−b−a ) = 0.33wm + 2wa.
∴ z1 = m−5b.
Similarly we have for the new distance from CPfw to CG1:
0.66(z1−b )−b = 0.66m−5b.
[26] It is to be remembered that these aerodromes were under incessant modifications, No. 4
for instance, presenting successive changes which made of it in reality a number of different
machines, one merging by constant alterations into the other, though it still went under the same
name. After 1895 the type of the models remained relatively constant, but during the first five
years of the work, constructions equal to the original building of at least eight or ten independent
aerodromes were made.
[27] Chapter V ◊.
[28] “Pocketing” is a form of distortion in which the canvas or silk bags locally in numerous
places between the cross-ribs.
[29] The site of these experiments, which was 30 miles below Washington, has been
described. The writer is designated by the initial “L”; Dr. Barus, who several times assisted, by the
letter “B”; Mr Reed, carpenter, by “R”; Mr Maltby, machinist, by “M”; and Mr. Gaertner,
instrument maker, by “G.”
[30] Weights and dimensions are here given in approximate pounds and feet.
[31] “Experiments in Aerodynamics.”
[32] On the data of “Aerodynamics,” a plane having 1.8 sq. ft. of surface per pound, and
advancing at an angle of 20°, would soar at a speed of 24.1 ft. per second.
distance from CG1 to the new CPrw by z, and equating the difference between the weight of the
rear wing multiplied by its new distance from CG1 and the weight of the front wing multiplied by
its new distance from CG1 and making this difference equal to the constant difference, we can
calculate z in terms of m and b, as follows:
Fig. 8,
w (a + z )−w(0.66(z + b ) + b−a ) = 0.33wm + 2wa,
∴ z = m + 5b.
Knowing z, we readily find that the new distance from CPfw to CG1 equals:
0.66(z + b ) + b = 0.66m + 5b.
In a similar manner we may calculate the proper relative positions of the front and rear wings
when we wish to move the center of pressure backward a distance, b, from the original CP1
without changing the position of CG1. From Fig. 7, we have as before:
w (m + a )−w(0.66m−a ) = constant,
0.33wm + 2wa = constant.
Fig. 9,
w (z1 + a )−w(0.66(z1−b )−b−a ) = 0.33wm + 2wa.
∴ z1 = m−5b.
Similarly we have for the new distance from CPfw to CG1:
0.66(z1−b )−b = 0.66m−5b.
[26] It is to be remembered that these aerodromes were under incessant modifications, No. 4
for instance, presenting successive changes which made of it in reality a number of different
machines, one merging by constant alterations into the other, though it still went under the same
name. After 1895 the type of the models remained relatively constant, but during the first five
years of the work, constructions equal to the original building of at least eight or ten independent
aerodromes were made.
[27] Chapter V ◊.
[28] “Pocketing” is a form of distortion in which the canvas or silk bags locally in numerous
places between the cross-ribs.
[29] The site of these experiments, which was 30 miles below Washington, has been
described. The writer is designated by the initial “L”; Dr. Barus, who several times assisted, by the
letter “B”; Mr Reed, carpenter, by “R”; Mr Maltby, machinist, by “M”; and Mr. Gaertner,
instrument maker, by “G.”
[30] Weights and dimensions are here given in approximate pounds and feet.
[31] “Experiments in Aerodynamics.”
[32] On the data of “Aerodynamics,” a plane having 1.8 sq. ft. of surface per pound, and
advancing at an angle of 20°, would soar at a speed of 24.1 ft. per second.
Page 224
[33] It will be remembered that the purely theoretical conclusions just cited apply to the power
delivered in direct thrust, but that of the above actual H. P. an indefinite amount was lost in friction
and slip of propellers.
[34] It may be observed that at this time the position of the CP was calculated on the
assumption that the pressure for flight surfaces was proportional to the areas, without also allowing
for the fact that the following surfaces, like the tail, were under the “lee” of the wind and so far
less efficient. It follows, then, that the value CP−CG was not really 0, as was assumed, but
something considerable.
[35] Very exact accuracy in these minute details is indispensable to the efficient working of the
engines.
[36] The reader who may care to note the evolution of this boiler, by trial and error, will find a
portion of the many discarded types shown in Plate 13.
delivered in direct thrust, but that of the above actual H. P. an indefinite amount was lost in friction
and slip of propellers.
[34] It may be observed that at this time the position of the CP was calculated on the
assumption that the pressure for flight surfaces was proportional to the areas, without also allowing
for the fact that the following surfaces, like the tail, were under the “lee” of the wind and so far
less efficient. It follows, then, that the value CP−CG was not really 0, as was assumed, but
something considerable.
[35] Very exact accuracy in these minute details is indispensable to the efficient working of the
engines.
[36] The reader who may care to note the evolution of this boiler, by trial and error, will find a
portion of the many discarded types shown in Plate 13.
Page 225
◊
P ART II. 1897 TO 1903
B Y CHARLES M. MANLY
Assistant in Charge of Experiments
CHAPTER I
INTRODUCTORY
Although in 1896 Mr. Langley had made the firm resolution not to
undertake the construction of a large man-carrying machine, as he realized
that his multitudinous administrative duties left him practically no time
available for original research, yet the longing to take the final great step of
actually transporting a human being through the air, which the successful
flights of the models had now for the first time in the history of the world
actually proved to be possible, soon became irresistible.
Ten years of almost disheartening difficulties, a full appreciation of
which can hardly be gained from the preceding description, had already
been spent in demonstrating that mechanical flight was practicable, and Mr.
Langley thoroughly realized that the construction of a large aerodrome
would involve as great, if not even greater difficulties. Nevertheless, his
indomitable will, which balked at no obstacle, however great it might seem,
prevailed against the advice of his close friends and associates, and even
that of his physician, who had counselled him that a resumption of
concentrated thought and vigorous endeavor would materially shorten his
life, which had already passed three score years. Only a few were privileged
to come into close contact with him in his daily work, and thereby catch the
inspiration of his unwavering persistence, his ceaseless perseverance, his
plain inability to submit to defeat; but no one who has read the record of his
astronomical expedition to Mt. Whitney, or the story of his development of
P ART II. 1897 TO 1903
B Y CHARLES M. MANLY
Assistant in Charge of Experiments
CHAPTER I
INTRODUCTORY
Although in 1896 Mr. Langley had made the firm resolution not to
undertake the construction of a large man-carrying machine, as he realized
that his multitudinous administrative duties left him practically no time
available for original research, yet the longing to take the final great step of
actually transporting a human being through the air, which the successful
flights of the models had now for the first time in the history of the world
actually proved to be possible, soon became irresistible.
Ten years of almost disheartening difficulties, a full appreciation of
which can hardly be gained from the preceding description, had already
been spent in demonstrating that mechanical flight was practicable, and Mr.
Langley thoroughly realized that the construction of a large aerodrome
would involve as great, if not even greater difficulties. Nevertheless, his
indomitable will, which balked at no obstacle, however great it might seem,
prevailed against the advice of his close friends and associates, and even
that of his physician, who had counselled him that a resumption of
concentrated thought and vigorous endeavor would materially shorten his
life, which had already passed three score years. Only a few were privileged
to come into close contact with him in his daily work, and thereby catch the
inspiration of his unwavering persistence, his ceaseless perseverance, his
plain inability to submit to defeat; but no one who has read the record of his
astronomical expedition to Mt. Whitney, or the story of his development of
Page 226
the Bolometer, or the preceding chapters of this history of his years of
patient work in the development of the flying machine, can have failed to
obtain some appreciation of this most striking feature of his character.
Having once determined on the accomplishment of a definite object, no
amount of difficulty that might arise deterred him from pushing on until in
some way and by some means he had succeeded; and no one appreciated
better than he that if the thin edge of the right wedge can be inserted under
an obstacle, that obstacle can be removed, no matter how formidable it may
seem.
The undertaking of the construction of a large aerodrome was very
largely influenced by President McKinley, who had become impressed with
the great [p124] possibilities of a flying machine as an engine of war. When
he found that Mr. Langley was willing to devote his own time to the
development of a machine, provided the Government would furnish the
funds for the actual construction and tests of it, he appointed a joint board,
consisting of Army and Navy officers, to investigate and report on the plans
with which Mr. Langley had achieved success with the models. The report
of this joint board of Army and Navy officers being favorable, the Board of
Ordnance and Fortification of the War Department, at the direction of
President McKinley, requested Mr. Langley to undertake the construction
and test of a machine, which, while not expected to be a practical war
machine, might finally lead to the development of such an engine of war. In
this connection it is interesting to read a letter which Mr. Langley addressed
to the Board of Ordnance and Fortification at the time he undertook this
work.
SMITHSONIAN INSTITUTION, December 12, 1898.
The Board of Ordnance and Fortification, War Department.
GENTLEMEN: In response to your invitation, I repeat what I had the honor to say to the Board
—that I am willing, with the consent of the Regents of this Institution, to undertake for the
Government the further investigation of the subject of the construction of a flying machine on a
scale capable of carrying a man, the investigation to include the construction, development and test
of such a machine under conditions left as far as practicable in my discretion, it being understood
that my services are given to the Government in such time as may not be occupied by the business
of the Institution, and without charge.
patient work in the development of the flying machine, can have failed to
obtain some appreciation of this most striking feature of his character.
Having once determined on the accomplishment of a definite object, no
amount of difficulty that might arise deterred him from pushing on until in
some way and by some means he had succeeded; and no one appreciated
better than he that if the thin edge of the right wedge can be inserted under
an obstacle, that obstacle can be removed, no matter how formidable it may
seem.
The undertaking of the construction of a large aerodrome was very
largely influenced by President McKinley, who had become impressed with
the great [p124] possibilities of a flying machine as an engine of war. When
he found that Mr. Langley was willing to devote his own time to the
development of a machine, provided the Government would furnish the
funds for the actual construction and tests of it, he appointed a joint board,
consisting of Army and Navy officers, to investigate and report on the plans
with which Mr. Langley had achieved success with the models. The report
of this joint board of Army and Navy officers being favorable, the Board of
Ordnance and Fortification of the War Department, at the direction of
President McKinley, requested Mr. Langley to undertake the construction
and test of a machine, which, while not expected to be a practical war
machine, might finally lead to the development of such an engine of war. In
this connection it is interesting to read a letter which Mr. Langley addressed
to the Board of Ordnance and Fortification at the time he undertook this
work.
SMITHSONIAN INSTITUTION, December 12, 1898.
The Board of Ordnance and Fortification, War Department.
GENTLEMEN: In response to your invitation, I repeat what I had the honor to say to the Board
—that I am willing, with the consent of the Regents of this Institution, to undertake for the
Government the further investigation of the subject of the construction of a flying machine on a
scale capable of carrying a man, the investigation to include the construction, development and test
of such a machine under conditions left as far as practicable in my discretion, it being understood
that my services are given to the Government in such time as may not be occupied by the business
of the Institution, and without charge.
Page 227
I have reason to believe that the cost of the construction will come within the sum of
$50,000.00, and that not more than one-half of that will be called for in the coming year.
I entirely agree with what I understand to be the wish of the Board that privacy be observed with
regard to the work, and only when it reaches a successful completion shall I wish to make public
the fact of its success.
I attach to this a memorandum of my understanding of some points of detail in order to be sure
that it is also the understanding of the Board, and I am, gentlemen,
With much respect,
Your obedient servant,
S. P. LANGLEY.
MEMORANDUM
ATTACHED TO MY LETTER OF THIS DATE TO THE BOARD OF ORDNANCE AND
FORTIFICATION
While stating that I have, so far as I know, an exclusive right of property in the results of the
experiments in aerodromics which I have conducted heretofore and am now conducting, and while
understanding that this property and all rights connected with it, whether patentable or otherwise,
will remain mine unqualifiedly, I am glad to place these results, without charge, at the service of
the Board of Ordnance and Fortification for the special construction at present proposed, which
seems to me to be of National utility. [p125]
I assume that no public statement will be made by the permission of the Board until the work is
terminated, but that I may publish ultimately at my discretion a statement of any scientific work
done in this connection.
I understand that the exercise of this discretion includes the ordering and purchase of all
material by contract or in open market, and the employment of any necessary help, without
restriction, and that, while I desire that no money shall pass through my hands, itemized bills for
each expenditure, made in proper form and approved by me, will be paid by the Chief Signal
Officer.
Much has already been spent at the Smithsonian Institution for the purpose in question, in
special apparatus, tools and experiments, and in recent constructions now actually going on, which
have involved still more time than money, and which are essential for experimental use in building
the proposed machine; and since to re-create all this independently would greatly defer progress, I
assume that my discretion includes the decision as to how far this shall be used and paid for at the
cost of this allotment (it being understood that I have no personal property in any of the material
which might be transferred for the purpose of the work); and I also assume that my discretion
includes the decision as to where the work shall be conducted—that is, whether in shops already
constructed, or in others to be elsewhere erected or rented, with the necessary adjuncts, whether on
land or water, and generally whatever is necessary to the earliest attainment of the object desired
by the Board.
S. P. LANGLEY.
SMITHSONIAN INSTITUTION, WASHINGTON, D. C.,
December 12, 1898.
As is always the case in experimental work, especially in a field so very
new as was the field of aerodromics at the time that this larger construction
was undertaken, the “plant,” or shops and laboratories required for the
$50,000.00, and that not more than one-half of that will be called for in the coming year.
I entirely agree with what I understand to be the wish of the Board that privacy be observed with
regard to the work, and only when it reaches a successful completion shall I wish to make public
the fact of its success.
I attach to this a memorandum of my understanding of some points of detail in order to be sure
that it is also the understanding of the Board, and I am, gentlemen,
With much respect,
Your obedient servant,
S. P. LANGLEY.
MEMORANDUM
ATTACHED TO MY LETTER OF THIS DATE TO THE BOARD OF ORDNANCE AND
FORTIFICATION
While stating that I have, so far as I know, an exclusive right of property in the results of the
experiments in aerodromics which I have conducted heretofore and am now conducting, and while
understanding that this property and all rights connected with it, whether patentable or otherwise,
will remain mine unqualifiedly, I am glad to place these results, without charge, at the service of
the Board of Ordnance and Fortification for the special construction at present proposed, which
seems to me to be of National utility. [p125]
I assume that no public statement will be made by the permission of the Board until the work is
terminated, but that I may publish ultimately at my discretion a statement of any scientific work
done in this connection.
I understand that the exercise of this discretion includes the ordering and purchase of all
material by contract or in open market, and the employment of any necessary help, without
restriction, and that, while I desire that no money shall pass through my hands, itemized bills for
each expenditure, made in proper form and approved by me, will be paid by the Chief Signal
Officer.
Much has already been spent at the Smithsonian Institution for the purpose in question, in
special apparatus, tools and experiments, and in recent constructions now actually going on, which
have involved still more time than money, and which are essential for experimental use in building
the proposed machine; and since to re-create all this independently would greatly defer progress, I
assume that my discretion includes the decision as to how far this shall be used and paid for at the
cost of this allotment (it being understood that I have no personal property in any of the material
which might be transferred for the purpose of the work); and I also assume that my discretion
includes the decision as to where the work shall be conducted—that is, whether in shops already
constructed, or in others to be elsewhere erected or rented, with the necessary adjuncts, whether on
land or water, and generally whatever is necessary to the earliest attainment of the object desired
by the Board.
S. P. LANGLEY.
SMITHSONIAN INSTITUTION, WASHINGTON, D. C.,
December 12, 1898.
As is always the case in experimental work, especially in a field so very
new as was the field of aerodromics at the time that this larger construction
was undertaken, the “plant,” or shops and laboratories required for the
Page 228
constructional and testing work, grew to a size far beyond what seemed
even remotely possible at the beginning of the work; and even the mere
administration involved in the carrying on of this work proved to be no
inconsiderable matter before it had progressed very far.
The years of experiment with the models had demonstrated clearly that
the greatest difficulty in the development of the aerodrome was the
construction of a suitable power generator, which should combine the
elements of extreme lightness and unusual power with a fair degree of
durability. Although remarkably good results had been secured in the case
of the models through the use of steam, it was realized from the first that
not only would the development of a steam-power plant for a large man-
carrying aerodrome present difficulties of a constructional nature, but that
such a steam plant would necessarily be so fragile and delicate as to make it
a constant menace to the machine which it was to propel. The solution of
the difficulty, it was believed, was to be found in the use of an internal
combustion engine; but Mr. Langley had had very little experience with
such engines, and was averse therefore to undertaking the construction of a
large aerodrome until he had assurance that a suitable gasoline engine could
be secured. Before making an agreement to attempt the work for the War
[p126] Department, he had, therefore, made a search for a reliable builder
who would undertake to construct a gasoline engine of not less than 12
horse-power to weigh not exceeding 100 pounds, and what then seemed a
safe contract had been entered into with such a builder to supply one engine
which would meet these requirements.
Almost immediately before the Board of Ordnance and Fortification had
officially placed the work in Mr. Langley’s hands and had made an
allotment of fifty thousand dollars to meet the expenses thereof, it was
found that the engine builder could not be depended on, and that it would,
therefore, be necessary to find one who was more reliable and more
experienced in the construction of light engines. After a most extended
search for the best builder to undertake this work, a contract was entered
into on December 12, 1898, with Mr. S. M. Balzer, an engine builder in
New York City. He was to furnish a twelve-horse-power engine to weigh
even remotely possible at the beginning of the work; and even the mere
administration involved in the carrying on of this work proved to be no
inconsiderable matter before it had progressed very far.
The years of experiment with the models had demonstrated clearly that
the greatest difficulty in the development of the aerodrome was the
construction of a suitable power generator, which should combine the
elements of extreme lightness and unusual power with a fair degree of
durability. Although remarkably good results had been secured in the case
of the models through the use of steam, it was realized from the first that
not only would the development of a steam-power plant for a large man-
carrying aerodrome present difficulties of a constructional nature, but that
such a steam plant would necessarily be so fragile and delicate as to make it
a constant menace to the machine which it was to propel. The solution of
the difficulty, it was believed, was to be found in the use of an internal
combustion engine; but Mr. Langley had had very little experience with
such engines, and was averse therefore to undertaking the construction of a
large aerodrome until he had assurance that a suitable gasoline engine could
be secured. Before making an agreement to attempt the work for the War
[p126] Department, he had, therefore, made a search for a reliable builder
who would undertake to construct a gasoline engine of not less than 12
horse-power to weigh not exceeding 100 pounds, and what then seemed a
safe contract had been entered into with such a builder to supply one engine
which would meet these requirements.
Almost immediately before the Board of Ordnance and Fortification had
officially placed the work in Mr. Langley’s hands and had made an
allotment of fifty thousand dollars to meet the expenses thereof, it was
found that the engine builder could not be depended on, and that it would,
therefore, be necessary to find one who was more reliable and more
experienced in the construction of light engines. After a most extended
search for the best builder to undertake this work, a contract was entered
into on December 12, 1898, with Mr. S. M. Balzer, an engine builder in
New York City. He was to furnish a twelve-horse-power engine to weigh
Page 229
not more then 100 pounds, and delivery of it was to be made on or before
February 28, 1899. With this great problem of the engine apparently
provided for, every facility of the Institution shops was pressed to the
utmost limit in order to have the frame, supporting surfaces, launching
apparatus, and other accessories ready as soon as possible after the delivery
of the engine. It was expected from the first that more power would be
necessary than this one engine would furnish, and provision had been made
in the contract that a duplicate engine should be constructed immediately
after the completion of this first one. From past experience, however, it was
not likely that the correct balancing of the aerodrome could be determined
from a priori calculation based on the results obtained with the models, and
it was, therefore, expected that the aerodrome would have to be launched
several times before a successful flight could be obtained. In view of this it
was planned to make a test of the machine as soon as the first engine was
ready, with the expectation that, while the aerodrome would not have
sufficient power to fly, yet the test would furnish definite data on the all-
important question of balancing, and also determine whether or not the
launching apparatus would require modification. In fact, Mr. Langley felt so
apprehensive that the first, and possibly the second test, would be
unsuccessful that, in order to avoid the possibility of a fatal accident, it was
planned that a dummy should be used to represent the weight of the man in
these preliminary tests.
This plan, however, was not carried out. In 1903, when the large
aerodrome was finally completed, so much time had been lost that the
writer proposed to assume the risks of such an accident and to guide the
machine in its first test, in the hope of avoiding a disaster, with the
consequent delay of months for repairs, which the presence of a controlling
hand capable of correcting any inaccuracies of balancing rendered far less
likely to occur. To this proposal Mr. Langley assented with great reluctance,
as he fully realized the danger involved. [p127]
Particular attention is called to the above facts, which clearly show that
while a certain degree of success in the initial tests was later hoped for, yet
February 28, 1899. With this great problem of the engine apparently
provided for, every facility of the Institution shops was pressed to the
utmost limit in order to have the frame, supporting surfaces, launching
apparatus, and other accessories ready as soon as possible after the delivery
of the engine. It was expected from the first that more power would be
necessary than this one engine would furnish, and provision had been made
in the contract that a duplicate engine should be constructed immediately
after the completion of this first one. From past experience, however, it was
not likely that the correct balancing of the aerodrome could be determined
from a priori calculation based on the results obtained with the models, and
it was, therefore, expected that the aerodrome would have to be launched
several times before a successful flight could be obtained. In view of this it
was planned to make a test of the machine as soon as the first engine was
ready, with the expectation that, while the aerodrome would not have
sufficient power to fly, yet the test would furnish definite data on the all-
important question of balancing, and also determine whether or not the
launching apparatus would require modification. In fact, Mr. Langley felt so
apprehensive that the first, and possibly the second test, would be
unsuccessful that, in order to avoid the possibility of a fatal accident, it was
planned that a dummy should be used to represent the weight of the man in
these preliminary tests.
This plan, however, was not carried out. In 1903, when the large
aerodrome was finally completed, so much time had been lost that the
writer proposed to assume the risks of such an accident and to guide the
machine in its first test, in the hope of avoiding a disaster, with the
consequent delay of months for repairs, which the presence of a controlling
hand capable of correcting any inaccuracies of balancing rendered far less
likely to occur. To this proposal Mr. Langley assented with great reluctance,
as he fully realized the danger involved. [p127]
Particular attention is called to the above facts, which clearly show that
while a certain degree of success in the initial tests was later hoped for, yet
Page 230
from the beginning it had been felt rather certain that several tests would
have to be made before final success would be achieved.
To those experienced in scientific experiments this realization of the
probability of several tests being necessary before success could reasonably
be expected does not seem strange, for the record of past experience
contains very few examples of epoch-making inventions springing full
fledged from the hand of their maker and proving a success on the first test.
The two experiments made in the fall of 1903, in which the aerodrome
was each time so damaged in the process of launching that its ability to fly
was never really tested, should therefore be considered merely as the first of
a series which it had been expected would need to be made before success
would be achieved. Further tests were made impossible at the time on
account of the lack of funds, the expense of such work being unusually
heavy.
While the lack of funds, therefore, was the real cause of the temporary
suspension of the work, yet an influence which does not often enter into
scientific work—the unjust criticism of a hostile press—was directly
responsible for the lack of funds. It seems very certain that had it not been
for this criticism of the press the funds would have been readily
forthcoming for continuing the work to the point of success.
have to be made before final success would be achieved.
To those experienced in scientific experiments this realization of the
probability of several tests being necessary before success could reasonably
be expected does not seem strange, for the record of past experience
contains very few examples of epoch-making inventions springing full
fledged from the hand of their maker and proving a success on the first test.
The two experiments made in the fall of 1903, in which the aerodrome
was each time so damaged in the process of launching that its ability to fly
was never really tested, should therefore be considered merely as the first of
a series which it had been expected would need to be made before success
would be achieved. Further tests were made impossible at the time on
account of the lack of funds, the expense of such work being unusually
heavy.
While the lack of funds, therefore, was the real cause of the temporary
suspension of the work, yet an influence which does not often enter into
scientific work—the unjust criticism of a hostile press—was directly
responsible for the lack of funds. It seems very certain that had it not been
for this criticism of the press the funds would have been readily
forthcoming for continuing the work to the point of success.
Page 231
[p128] ◊
CHAPTER II
GENERAL CONSIDERATIONS
In the development of man-carrying flying machines two well-defined
paths are open. First: Starting with gliding machines, in which gravity
furnishes the motive power, the operator may by practice acquire sufficient
skill in controlling them to warrant the addition of propelling mechanism,
and individual skill in control may be gradually replaced by automatic
controlling mechanism. Second: From self-propelled models, possessing
automatic-equilibrium controlling mechanism, and of a sufficient size to
furnish determinative data, one may, by proper modification in size and
construction, progress to an automatically controlled man-carrying machine
in which, for ideal conditions, no especial skill on the part of the operator is
required. Each method has its advantages.
After concluding his earlier and purely physical researches, the results of
which were embodied in “Experiments in Aerodynamics,” Mr. Langley was
so firmly convinced of the practicability of mechanical flight that he
undertook the construction of the model aerodromes in order to demonstrate
it. It is very doubtful if at any time, prior to the successful flights of the
models in 1896, he seriously contemplated the construction of man-carrying
machines. His object in developing the models was not, therefore, to furnish
a prototype for a large machine, but merely to demonstrate the feasibility of
mechanical flight; and this he did. This is shown very clearly by the closing
remark of the article he published in 1897, describing the flights of the
models. “I have now brought to a close the portion of the work which
seemed to be specially mine—the demonstration of the practicability of
mechanical flight-—and for the next stage, which is the commercial and
practical development of the idea, it is probable that the world may look to
others.”37 When he later undertook the construction of the large machine
for the War Department it was natural that, with the inspiring sight of the
models in flight still fresh in his mind, he determined to use as a prototype
CHAPTER II
GENERAL CONSIDERATIONS
In the development of man-carrying flying machines two well-defined
paths are open. First: Starting with gliding machines, in which gravity
furnishes the motive power, the operator may by practice acquire sufficient
skill in controlling them to warrant the addition of propelling mechanism,
and individual skill in control may be gradually replaced by automatic
controlling mechanism. Second: From self-propelled models, possessing
automatic-equilibrium controlling mechanism, and of a sufficient size to
furnish determinative data, one may, by proper modification in size and
construction, progress to an automatically controlled man-carrying machine
in which, for ideal conditions, no especial skill on the part of the operator is
required. Each method has its advantages.
After concluding his earlier and purely physical researches, the results of
which were embodied in “Experiments in Aerodynamics,” Mr. Langley was
so firmly convinced of the practicability of mechanical flight that he
undertook the construction of the model aerodromes in order to demonstrate
it. It is very doubtful if at any time, prior to the successful flights of the
models in 1896, he seriously contemplated the construction of man-carrying
machines. His object in developing the models was not, therefore, to furnish
a prototype for a large machine, but merely to demonstrate the feasibility of
mechanical flight; and this he did. This is shown very clearly by the closing
remark of the article he published in 1897, describing the flights of the
models. “I have now brought to a close the portion of the work which
seemed to be specially mine—the demonstration of the practicability of
mechanical flight-—and for the next stage, which is the commercial and
practical development of the idea, it is probable that the world may look to
others.”37 When he later undertook the construction of the large machine
for the War Department it was natural that, with the inspiring sight of the
models in flight still fresh in his mind, he determined to use as a prototype
Page 232
these successful machines, which were the only things of human
construction that had ever really flown for any considerable distance.
Not being an engineer, and realizing that to pass from the construction of
models to that of man-carrying machines involved the solution of many
engineering problems, Mr. Langley, in the spring of 1898, sought the advice
of Dr. R. H. Thurston, who had from the first manifested the deepest
interest in his [p129] work in aerodromics. On the recommendation of Dr.
Thurston he engaged the services of the writer, who assumed charge of the
work in June, 1898.
While the method of “cut and try” had brought success in the models,
and was perhaps the only method by which they could have been
successfully developed, it was thought that, with these models as a basis of
design, much time would be saved by making an analytical study of them as
engineering structures, and from the data thus obtained the proper
proportions for the parts of the larger machine could be calculated.
Such an analytical study, however, revealed very little from which to
make calculations as to the strength necessary for the various parts of the
large machine, but it did show very clearly that most of the parts were
working under stresses generally far above the elastic limit of the materials,
and in many cases the ultimate breaking strength was closely approached.
Such a condition was the natural outcome of the method by which these
models had been developed—all the various parts having been built at first
of the least possible weight and, when they proved too weak, strengthened
until they would withstand the stresses imposed on them. It is extremely
doubtful if previous calculations as to the strength necessary would have
been of any assistance, in fact it is probable that it would have been a
distinct disadvantage and would have resulted in the machines being
entirely too heavy for flight.
The exact strength which had been incorporated in the frames of the
models was as unknown as was the exact amount of the stresses which they
has been made to withstand. Their static strength was easily determined by
calculation, but the stresses due to the live loads were incapable of exact
determination from the available data, for stresses produce strains, which in
construction that had ever really flown for any considerable distance.
Not being an engineer, and realizing that to pass from the construction of
models to that of man-carrying machines involved the solution of many
engineering problems, Mr. Langley, in the spring of 1898, sought the advice
of Dr. R. H. Thurston, who had from the first manifested the deepest
interest in his [p129] work in aerodromics. On the recommendation of Dr.
Thurston he engaged the services of the writer, who assumed charge of the
work in June, 1898.
While the method of “cut and try” had brought success in the models,
and was perhaps the only method by which they could have been
successfully developed, it was thought that, with these models as a basis of
design, much time would be saved by making an analytical study of them as
engineering structures, and from the data thus obtained the proper
proportions for the parts of the larger machine could be calculated.
Such an analytical study, however, revealed very little from which to
make calculations as to the strength necessary for the various parts of the
large machine, but it did show very clearly that most of the parts were
working under stresses generally far above the elastic limit of the materials,
and in many cases the ultimate breaking strength was closely approached.
Such a condition was the natural outcome of the method by which these
models had been developed—all the various parts having been built at first
of the least possible weight and, when they proved too weak, strengthened
until they would withstand the stresses imposed on them. It is extremely
doubtful if previous calculations as to the strength necessary would have
been of any assistance, in fact it is probable that it would have been a
distinct disadvantage and would have resulted in the machines being
entirely too heavy for flight.
The exact strength which had been incorporated in the frames of the
models was as unknown as was the exact amount of the stresses which they
has been made to withstand. Their static strength was easily determined by
calculation, but the stresses due to the live loads were incapable of exact
determination from the available data, for stresses produce strains, which in
Page 233
turn generally cause distortions accompanied by greatly increased stresses.
While exact data were, therefore, lacking as to stresses and strengths in
many of the important parts, yet the models furnished most important
illustrations of unusual strength for minimum weight, and a careful study of
them showed many ways in which increased strength could be obtained
with decreased weight which could hardly have been devised without these
concrete examples.
It was, however, by no means possible to build the large aerodrome
within the permissible limits of weight by simply increasing the various
parts of the models according to some predetermined function of the size of
the whole.
The fundamental difficulty is that inevitably, by the laws of geometry,
which are mere expressions of the properties of space, if a solid of any form
is magnified, the weight increases as the cube, while the surface increases
only as the square, of the linear dimensions. Successive generations of
physicists and mathematicians pointed out that while this “law of the cube”
is of advantage in the construction of balloons, yet it is a stumbling block
that will prevent man [p130] from ever building a dynamic flying machine
sufficiently large to carry even one human being.38
However, since strength is a function of material and form rather than
weight, it is possible by selecting proper materials and adopting suitable
structural forms to evade to a certain extent this “law of the cube.” The
whole history of structural science has therefore been a series of attempts to
find stronger and lighter material and to discover methods of so modifying
form as to dispense with all parts of a structure that do not contribute to its
strength. So in aerodromics the structural problem has been that of finding
materials and forms best suited to the purpose for which they are required,
for it does not always follow that either the form or the material best suited
for one scale of construction is the most advantageous to employ on a
different scale. Nor is even the form or material which gives the greatest
strength for the least weight necessarily the best to employ. For the
structural problem must necessarily be co-ordinated with those of
While exact data were, therefore, lacking as to stresses and strengths in
many of the important parts, yet the models furnished most important
illustrations of unusual strength for minimum weight, and a careful study of
them showed many ways in which increased strength could be obtained
with decreased weight which could hardly have been devised without these
concrete examples.
It was, however, by no means possible to build the large aerodrome
within the permissible limits of weight by simply increasing the various
parts of the models according to some predetermined function of the size of
the whole.
The fundamental difficulty is that inevitably, by the laws of geometry,
which are mere expressions of the properties of space, if a solid of any form
is magnified, the weight increases as the cube, while the surface increases
only as the square, of the linear dimensions. Successive generations of
physicists and mathematicians pointed out that while this “law of the cube”
is of advantage in the construction of balloons, yet it is a stumbling block
that will prevent man [p130] from ever building a dynamic flying machine
sufficiently large to carry even one human being.38
However, since strength is a function of material and form rather than
weight, it is possible by selecting proper materials and adopting suitable
structural forms to evade to a certain extent this “law of the cube.” The
whole history of structural science has therefore been a series of attempts to
find stronger and lighter material and to discover methods of so modifying
form as to dispense with all parts of a structure that do not contribute to its
strength. So in aerodromics the structural problem has been that of finding
materials and forms best suited to the purpose for which they are required,
for it does not always follow that either the form or the material best suited
for one scale of construction is the most advantageous to employ on a
different scale. Nor is even the form or material which gives the greatest
strength for the least weight necessarily the best to employ. For the
structural problem must necessarily be co-ordinated with those of
Page 234
balancing, propelling, and transporting, and each must, therefore, have its
proper attention in the design of the whole machine.
Many of the general considerations of the design of an aerodrome
sufficiently large to transport a man were determined during the spring and
summer of 1898, when the first actual drawings (Plate 32, Figs. 1, 2 and 3)
of the proposed machine were made. Starting with the assumption that the
Models Nos. 5 and 6 were capable of transporting a load of approximately
ten pounds more than their weight, it was seen that, since the supporting
surface of any aerodrome would increase approximately as the square of the
linear dimensions, in order to carry a man the aerodrome would need to be
approximately four times the linear dimensions of these models.
Calculations based on the results accomplished in the construction of the
models indicated that such an aerodrome would need to be equipped with
engines developing 24 horse-power. The best that could reasonably be
hoped for was that these engines would not weigh over 200 pounds, and,
therefore, allowing 40 pounds for fuel and fuel tanks, it became necessary
to bring the weight of frame, supporting surfaces, tail, rudder, propellers
and every other accessory within 250 pounds, if the total weight of the
machine, including 150 pounds for the aeronaut, was not to exceed 640
pounds, or 16 times the combined weight of the model and its load of 10
pounds. Although the problem of constructing the frame, wings and all
other parts within the limit of 250 pounds seemed indeed formidable, it was
believed that the greatest obstacle in the production of such a machine
would be that of securing a sufficiently light and powerful engine to propel
it.
proper attention in the design of the whole machine.
Many of the general considerations of the design of an aerodrome
sufficiently large to transport a man were determined during the spring and
summer of 1898, when the first actual drawings (Plate 32, Figs. 1, 2 and 3)
of the proposed machine were made. Starting with the assumption that the
Models Nos. 5 and 6 were capable of transporting a load of approximately
ten pounds more than their weight, it was seen that, since the supporting
surface of any aerodrome would increase approximately as the square of the
linear dimensions, in order to carry a man the aerodrome would need to be
approximately four times the linear dimensions of these models.
Calculations based on the results accomplished in the construction of the
models indicated that such an aerodrome would need to be equipped with
engines developing 24 horse-power. The best that could reasonably be
hoped for was that these engines would not weigh over 200 pounds, and,
therefore, allowing 40 pounds for fuel and fuel tanks, it became necessary
to bring the weight of frame, supporting surfaces, tail, rudder, propellers
and every other accessory within 250 pounds, if the total weight of the
machine, including 150 pounds for the aeronaut, was not to exceed 640
pounds, or 16 times the combined weight of the model and its load of 10
pounds. Although the problem of constructing the frame, wings and all
other parts within the limit of 250 pounds seemed indeed formidable, it was
believed that the greatest obstacle in the production of such a machine
would be that of securing a sufficiently light and powerful engine to propel
it.
Page 235
PL. 32. DRAWINGS OF PROPOSED MAN-CARRYING AERODROME, 1898 ◊ lgr
[p131]
[p131]
Page 236
A brief account has already been given of the attempts made by Mr.
Langley to secure a suitable gasoline engine for the large aerodrome, but
the difficulties encountered in the search have not perhaps been sufficiently
emphasized. At this time (1898) the automobile industry, through which has
come the development of the gasoline engine, was in its infancy, and there
were few builders either in the United States or Europe who were
attempting anything but rough and heavy construction. Many of them were
enthusiastic over the possibilities of the internal combustion engine, and
were ready to talk of devising such an engine as the aerodrome would
require, but few were willing to guarantee any such definite results as were
demanded. However, the prospects of securing a suitable gasoline engine
from a reliable builder within a reasonable time seemed so strong that it was
decided early in 1898 to begin the construction of the frame on the general
plan which would probably be best adapted for use with a gasoline engine,
and in case it finally proved impossible to secure such an engine, to
construct later a steam plant which could be adapted to this particular
frame.
Some tentative work on the construction of the frame was accordingly
begun in the summer of 1898, some months before an engine builder was
found who seemed likely to be successful in furnishing the engines. An
extensive series of tests on propellers was also made at this time for the
immediate purpose of determining what form and size would be best, since
the dimensions of the transverse frame could not be definitely settled until it
was known how large the propellers would need to be.
Preliminary designs were also begun for the wings, rudders, and
launching apparatus, but when the point was reached of actually making the
working drawings for these, it was seen that the change in the scale of the
work required many important modifications in constructional details. As
the models had flown successfully only three times, and in each case under
practically the same conditions, it was felt that it would be unwise to make
changes in important details without first making a series of tests of the
models in flight to determine the effect of such changes. It was therefore
decided to completely overhaul Models Nos. 5 and 6, strengthening them in
Langley to secure a suitable gasoline engine for the large aerodrome, but
the difficulties encountered in the search have not perhaps been sufficiently
emphasized. At this time (1898) the automobile industry, through which has
come the development of the gasoline engine, was in its infancy, and there
were few builders either in the United States or Europe who were
attempting anything but rough and heavy construction. Many of them were
enthusiastic over the possibilities of the internal combustion engine, and
were ready to talk of devising such an engine as the aerodrome would
require, but few were willing to guarantee any such definite results as were
demanded. However, the prospects of securing a suitable gasoline engine
from a reliable builder within a reasonable time seemed so strong that it was
decided early in 1898 to begin the construction of the frame on the general
plan which would probably be best adapted for use with a gasoline engine,
and in case it finally proved impossible to secure such an engine, to
construct later a steam plant which could be adapted to this particular
frame.
Some tentative work on the construction of the frame was accordingly
begun in the summer of 1898, some months before an engine builder was
found who seemed likely to be successful in furnishing the engines. An
extensive series of tests on propellers was also made at this time for the
immediate purpose of determining what form and size would be best, since
the dimensions of the transverse frame could not be definitely settled until it
was known how large the propellers would need to be.
Preliminary designs were also begun for the wings, rudders, and
launching apparatus, but when the point was reached of actually making the
working drawings for these, it was seen that the change in the scale of the
work required many important modifications in constructional details. As
the models had flown successfully only three times, and in each case under
practically the same conditions, it was felt that it would be unwise to make
changes in important details without first making a series of tests of the
models in flight to determine the effect of such changes. It was therefore
decided to completely overhaul Models Nos. 5 and 6, strengthening them in
Page 237
many important parts and “tuning up” their power plants, which had
slightly deteriorated since they were last used in November, 1896. When the
work of preparing these models for further experiments was begun it was
thought that it would require at most only a few weeks, but as it progressed
it was found that certain parts of the mechanical work on the engines had
been so poorly executed originally that it would be necessary to practically
rebuild the engines. The final result was that the power plants of both
aerodromes were entirely rebuilt, and they were not ready for actual test in
flight until the spring of 1899. [p132]
Much of the preliminary work necessary for the determination of actual
working plans was therefore completed in the summer and fall of 1898, and
when on December 12 a seemingly satisfactory contract for the engines for
the large aerodrome had been made it was thought that rapid progress could
be made on the constructional work after January 1, 1899, when the
allotment from the War Department would become available.
slightly deteriorated since they were last used in November, 1896. When the
work of preparing these models for further experiments was begun it was
thought that it would require at most only a few weeks, but as it progressed
it was found that certain parts of the mechanical work on the engines had
been so poorly executed originally that it would be necessary to practically
rebuild the engines. The final result was that the power plants of both
aerodromes were entirely rebuilt, and they were not ready for actual test in
flight until the spring of 1899. [p132]
Much of the preliminary work necessary for the determination of actual
working plans was therefore completed in the summer and fall of 1898, and
when on December 12 a seemingly satisfactory contract for the engines for
the large aerodrome had been made it was thought that rapid progress could
be made on the constructional work after January 1, 1899, when the
allotment from the War Department would become available.
Page 238
[p133] ◊
CHAPTER III
EXPERIMENTS WITH MODELS
Immediately after the contract for the engine had been placed and the
actual work had been begun, attention was given to the problem of
providing means for properly launching the aerodrome. On the theory that
the plan of launching the small aerodromes, which had finally been adopted
after many years of painstaking experiment, would be the best to employ
for the large aerodrome, Mr. Langley decided to have constructed a large
house-boat with the launching track arranged on it in a way similar to that
used for the small machines. While the general plans for this boat had been
under consideration for some time, the actual working drawings were
completed in January, 1899, and so great seemed the need for expediting its
construction, in order to have it ready at the time when the engine was
expected, that the contract which was made for its construction specifically
provided for its being completed promptly, there being a large forfeit to
cover any delay on the part of the contractor.
While the boat itself was being constructed, the working drawings were
completed for the house to be built on it, and a contract was made for the
construction of this house within a given period, there being also a time
forfeit in this contract.
When the end of February arrived, it was found that, although the engine
builder had succeeded in constructing an engine which weighed one
hundred pounds, and which theoretically should have given something over
twelve horse-power, yet he was unable to make it work properly. And then
began a protracted period of most exasperating delays, the engine builder
promising from week to week that certainly within the succeeding ten days
he would be able to make delivery of the engine developing the full horse-
power for which the contract called. After this delay on the engine had
continued for some months—a delay which necessitated the cessation of the
work on the main steel frame of the aerodrome, as it was deemed best to
CHAPTER III
EXPERIMENTS WITH MODELS
Immediately after the contract for the engine had been placed and the
actual work had been begun, attention was given to the problem of
providing means for properly launching the aerodrome. On the theory that
the plan of launching the small aerodromes, which had finally been adopted
after many years of painstaking experiment, would be the best to employ
for the large aerodrome, Mr. Langley decided to have constructed a large
house-boat with the launching track arranged on it in a way similar to that
used for the small machines. While the general plans for this boat had been
under consideration for some time, the actual working drawings were
completed in January, 1899, and so great seemed the need for expediting its
construction, in order to have it ready at the time when the engine was
expected, that the contract which was made for its construction specifically
provided for its being completed promptly, there being a large forfeit to
cover any delay on the part of the contractor.
While the boat itself was being constructed, the working drawings were
completed for the house to be built on it, and a contract was made for the
construction of this house within a given period, there being also a time
forfeit in this contract.
When the end of February arrived, it was found that, although the engine
builder had succeeded in constructing an engine which weighed one
hundred pounds, and which theoretically should have given something over
twelve horse-power, yet he was unable to make it work properly. And then
began a protracted period of most exasperating delays, the engine builder
promising from week to week that certainly within the succeeding ten days
he would be able to make delivery of the engine developing the full horse-
power for which the contract called. After this delay on the engine had
continued for some months—a delay which necessitated the cessation of the
work on the main steel frame of the aerodrome, as it was deemed best to
Page 239
make certain tests of the engine running while supported by a portion of the
frame to determine whether or not it was strong enough before completing
the rest of it-—Mr. Langley decided to employ part of the time in the
construction of a model of one-eighth the linear dimensions of the large
aerodrome, which was to be used in testing a model of the newly designed
launching apparatus described later, and which might also be flown as a kite
in making check measurements on the proper balancing which should be
employed for the large aerodrome. [p134]
The perfected launching apparatus which had been used for the steam-
driven models Nos. 5 and 6 (described in Part I, Chapter X ◊) had proved
most satisfactory and reliable, but when the designs were made for a
launching apparatus for the large machine it was found that an exact
duplication of the plan of the small one involved serious difficulties in
connection with the construction of the house-boat, owing to the very
considerable weight and size of the turn-table necessary to permit the
aerodrome to be launched in any desired direction, regardless of the
direction in which the houseboat might be pointing under the influence of
the wind and tide. A new design was accordingly made for a launching
apparatus in which the launching car was to run on a track mounted directly
on the turn-table, the launching car supporting the aerodrome from
underneath, instead of being mounted in an inverted position on an
overhead track with the aerodrome depending from it.
From the previous description of the launching apparatus, it will be
recalled that, in order to provide that the aerodrome should drop slightly at
the moment of its release from the car, and thereby avoid all danger of
entanglement, the speed of the launching car at the point at which the
aerodrome was released was purposely made less than the “soaring speed”
of the aerodrome. Having this feature in mind, when designing the
“underneath” launching apparatus, it was recognized that the danger of the
aerodrome becoming entangled with this form of apparatus could be
avoided by making the launching speed greater than the velocity which it
would be necessary for the aerodrome to have in order to soar, provided the
balancing was correct and the aerodrome did soar. Nevertheless, it was
frame to determine whether or not it was strong enough before completing
the rest of it-—Mr. Langley decided to employ part of the time in the
construction of a model of one-eighth the linear dimensions of the large
aerodrome, which was to be used in testing a model of the newly designed
launching apparatus described later, and which might also be flown as a kite
in making check measurements on the proper balancing which should be
employed for the large aerodrome. [p134]
The perfected launching apparatus which had been used for the steam-
driven models Nos. 5 and 6 (described in Part I, Chapter X ◊) had proved
most satisfactory and reliable, but when the designs were made for a
launching apparatus for the large machine it was found that an exact
duplication of the plan of the small one involved serious difficulties in
connection with the construction of the house-boat, owing to the very
considerable weight and size of the turn-table necessary to permit the
aerodrome to be launched in any desired direction, regardless of the
direction in which the houseboat might be pointing under the influence of
the wind and tide. A new design was accordingly made for a launching
apparatus in which the launching car was to run on a track mounted directly
on the turn-table, the launching car supporting the aerodrome from
underneath, instead of being mounted in an inverted position on an
overhead track with the aerodrome depending from it.
From the previous description of the launching apparatus, it will be
recalled that, in order to provide that the aerodrome should drop slightly at
the moment of its release from the car, and thereby avoid all danger of
entanglement, the speed of the launching car at the point at which the
aerodrome was released was purposely made less than the “soaring speed”
of the aerodrome. Having this feature in mind, when designing the
“underneath” launching apparatus, it was recognized that the danger of the
aerodrome becoming entangled with this form of apparatus could be
avoided by making the launching speed greater than the velocity which it
would be necessary for the aerodrome to have in order to soar, provided the
balancing was correct and the aerodrome did soar. Nevertheless, it was
Page 240
deemed unwise to put too much dependence on the empirical calculations
from which the balancing of the large aerodrome would necessarily be
determined, and, therefore, some means seemed necessary for causing the
launching car to drop out of the way immediately upon releasing the
aerodrome. In the new design, more completely described below, in Chapter
IV ◊, this was accomplished by so arranging a portion of the front end of
the track that, at the moment the launching car released the aerodrome, it
dropped like a disappearing gun carriage, leaving the aerodrome free in the
air with no possibility of becoming entangled, provided the aerodrome itself
did not drop more rapidly than an angle of 15 degrees.
A small working model of this launching apparatus, one-eighth the linear
dimensions of that which would be necessary for the large aerodrome, was
first designed and constructed in the shop, the small one-eighth-size model
of the large aerodrome being launched from it into a sheet stretched in front
of it to act as a buffer. When it was found to work very satisfactorily, a large
one, twice this size, was immediately built for use with the steam-driven
models Nos. 5 and 6. [p135]
These models, Nos. 5 and 6, which had flown so successfully in 1896,
had, during the preceding twelve months, been completely overhauled and
thoroughly tested in preparing them for trials in actual flight. Many
pendulum tests were made on both aerodromes, and it was found after
repeated trial that each could be depended on to show a lift of sixty per cent
of its flying weight.
This was more than sufficient for flight, but in order to insure successful
trials and avoid delay no aerodrome was launched until it had shown
previously its ability to generate enough power to maintain for at least two
minutes a lift of at least fifty per cent of the total flying weight.
Models Nos. 5 and 6, having thus proved their readiness for trial in flight,
were accordingly, in April, 1899, taken to Chopawamsic Island, together
with the old “overhead” launching apparatus and the new one above
described, and placed on a small house-boat similar to the one which had
been used in 1896. Two men were detailed for this special work, and were
first employed in mounting the old launching apparatus for a few
from which the balancing of the large aerodrome would necessarily be
determined, and, therefore, some means seemed necessary for causing the
launching car to drop out of the way immediately upon releasing the
aerodrome. In the new design, more completely described below, in Chapter
IV ◊, this was accomplished by so arranging a portion of the front end of
the track that, at the moment the launching car released the aerodrome, it
dropped like a disappearing gun carriage, leaving the aerodrome free in the
air with no possibility of becoming entangled, provided the aerodrome itself
did not drop more rapidly than an angle of 15 degrees.
A small working model of this launching apparatus, one-eighth the linear
dimensions of that which would be necessary for the large aerodrome, was
first designed and constructed in the shop, the small one-eighth-size model
of the large aerodrome being launched from it into a sheet stretched in front
of it to act as a buffer. When it was found to work very satisfactorily, a large
one, twice this size, was immediately built for use with the steam-driven
models Nos. 5 and 6. [p135]
These models, Nos. 5 and 6, which had flown so successfully in 1896,
had, during the preceding twelve months, been completely overhauled and
thoroughly tested in preparing them for trials in actual flight. Many
pendulum tests were made on both aerodromes, and it was found after
repeated trial that each could be depended on to show a lift of sixty per cent
of its flying weight.
This was more than sufficient for flight, but in order to insure successful
trials and avoid delay no aerodrome was launched until it had shown
previously its ability to generate enough power to maintain for at least two
minutes a lift of at least fifty per cent of the total flying weight.
Models Nos. 5 and 6, having thus proved their readiness for trial in flight,
were accordingly, in April, 1899, taken to Chopawamsic Island, together
with the old “overhead” launching apparatus and the new one above
described, and placed on a small house-boat similar to the one which had
been used in 1896. Two men were detailed for this special work, and were
first employed in mounting the old launching apparatus for a few
Page 241
preliminary tests with it, in order to make sure that the aerodromes were in
proper working order before trying them on the new “underneath” one.
After considerable delay, due to various causes, this apparatus and the
aerodromes were got into proper working condition, and during June, July
and August the following flights were made with these machines, the record
being condensed from the reports made by the writer to Mr. Langley while
he was abroad.
C ONDENSED R ECORD OF F LIGHTS OF A ERODROMES N OS. 5 AND 6
FROM J UNE 7 TO A UGUST 3, 189 9
J UNE 7— AERODROME NO. 6
After making a preliminary test of the engines and boiler, with the
aerodrome mounted on benches inside the house-boat, to insure that
everything connected with the power plant was in proper working order, the
aerodrome was mounted on the launching apparatus on top of the house, the
various parts were assembled and everything made ready for a flight. As it
was calculated that this aerodrome would require a soaring speed of
something like twenty-five feet a second, the springs which furnished the
motive power for the initial acceleration of the car were adjusted to the
proper tension to cause it to reach a speed of approximately twenty-three
feet a second at the moment of launching. Everything being in readiness the
burners were lighted but worked somewhat sluggishly at first, so that two
minutes were consumed in raising a steam pressure of 110 pounds.
Although this pressure should have been reached within one minute after
lighting the burners, and the extra minute which had been consumed had
made a drain on the supply of fuel and water which should have [p136] been
left for consumption during flight, yet it was thought best to launch the
aerodrome, so at 12.37 p. m. the car was released and the aerodrome
launched. The launching apparatus worked perfectly; the aerodrome started
off smoothly, and immediately after being released from the car it dropped
slightly and began to turn to the right. It had been impossible to move the
house-boat out into the stream so as to point the launching apparatus
proper working order before trying them on the new “underneath” one.
After considerable delay, due to various causes, this apparatus and the
aerodromes were got into proper working condition, and during June, July
and August the following flights were made with these machines, the record
being condensed from the reports made by the writer to Mr. Langley while
he was abroad.
C ONDENSED R ECORD OF F LIGHTS OF A ERODROMES N OS. 5 AND 6
FROM J UNE 7 TO A UGUST 3, 189 9
J UNE 7— AERODROME NO. 6
After making a preliminary test of the engines and boiler, with the
aerodrome mounted on benches inside the house-boat, to insure that
everything connected with the power plant was in proper working order, the
aerodrome was mounted on the launching apparatus on top of the house, the
various parts were assembled and everything made ready for a flight. As it
was calculated that this aerodrome would require a soaring speed of
something like twenty-five feet a second, the springs which furnished the
motive power for the initial acceleration of the car were adjusted to the
proper tension to cause it to reach a speed of approximately twenty-three
feet a second at the moment of launching. Everything being in readiness the
burners were lighted but worked somewhat sluggishly at first, so that two
minutes were consumed in raising a steam pressure of 110 pounds.
Although this pressure should have been reached within one minute after
lighting the burners, and the extra minute which had been consumed had
made a drain on the supply of fuel and water which should have [p136] been
left for consumption during flight, yet it was thought best to launch the
aerodrome, so at 12.37 p. m. the car was released and the aerodrome
launched. The launching apparatus worked perfectly; the aerodrome started
off smoothly, and immediately after being released from the car it dropped
slightly and began to turn to the right. It had been impossible to move the
house-boat out into the stream so as to point the launching apparatus
Page 242
directly into the wind, as one end had settled slightly on the muddy beach in
consequence of the existing low tide. For this reason it was necessary to
launch the aerodrome due south, while the wind, which was very light, was
from the north-northeast, and, therefore, blowing on its port quarter. The
effect of the aerodrome turning to the right immediately after being
launched was that it caused the wind to strike it to an increasing extent on
the port side until, finally, it was going directly with the wind. It did not,
however, continue in this direction, but kept turning to the right in a circle
until it headed directly into the wind, which, now striking the under instead
of the upper surface of the wings, immediately caused the aerodrome to
rise. It continued circling, making three complete circles of approximately
200 feet diameter, dropping slightly when moving with the wind, but rising
when moving against it, until, at the completion of the third circle, it had
altered its path to such an extent that the left front wing touched a tree and
caused the front of the machine to dip a little. It, however, kept up its flight,
but the contact with the tree had so lowered its bow, and apparently also
caused the wings to be twisted to such an extent, that it seemed unable to
rise again, and after making another quarter circle it descended. Although
the propellers were still turning when it struck the water, they had very
greatly decreased their speed, making it apparent that the power had been
very greatly reduced through the exhaustion of the fuel and water supply.
The aerodrome did not sink, but slowly drifted with the current of the creek
and was recovered in about five minutes and brought to the house-boat,
where the wings were dismounted and dried, and the metal parts were
carefully wiped off to prevent them from rusting. The path of this flight is
plotted on a portion of a coast-survey chart and is shown in Plate 33.
consequence of the existing low tide. For this reason it was necessary to
launch the aerodrome due south, while the wind, which was very light, was
from the north-northeast, and, therefore, blowing on its port quarter. The
effect of the aerodrome turning to the right immediately after being
launched was that it caused the wind to strike it to an increasing extent on
the port side until, finally, it was going directly with the wind. It did not,
however, continue in this direction, but kept turning to the right in a circle
until it headed directly into the wind, which, now striking the under instead
of the upper surface of the wings, immediately caused the aerodrome to
rise. It continued circling, making three complete circles of approximately
200 feet diameter, dropping slightly when moving with the wind, but rising
when moving against it, until, at the completion of the third circle, it had
altered its path to such an extent that the left front wing touched a tree and
caused the front of the machine to dip a little. It, however, kept up its flight,
but the contact with the tree had so lowered its bow, and apparently also
caused the wings to be twisted to such an extent, that it seemed unable to
rise again, and after making another quarter circle it descended. Although
the propellers were still turning when it struck the water, they had very
greatly decreased their speed, making it apparent that the power had been
very greatly reduced through the exhaustion of the fuel and water supply.
The aerodrome did not sink, but slowly drifted with the current of the creek
and was recovered in about five minutes and brought to the house-boat,
where the wings were dismounted and dried, and the metal parts were
carefully wiped off to prevent them from rusting. The path of this flight is
plotted on a portion of a coast-survey chart and is shown in Plate 33.
Page 243
PL. 33. PATHS OF FLIGHT OF AERODROME NO. 6, JUNE 7, 1899 ◊
This erratic circling at first seemed unaccountable, but on closer
examination, after the aerodrome had been brought into the house-boat, it
This erratic circling at first seemed unaccountable, but on closer
examination, after the aerodrome had been brought into the house-boat, it
Page 244
was found that the pin which connects the synchronizing gear to the port
propeller shaft had been sheared off. This had evidently happened while the
aerodrome was still on the launching apparatus. The effect of this was to
throw the total work of the water-circulating pump on the starboard engine,
thus giving the port engine less work to do, and consequently making the
port propeller run much faster than the starboard one, and thereby causing
the peculiar and erratic circling of the aerodrome. It is evident that the
undulatory motion of the [p137] aerodrome was due to the fact that, when it
was moving against the wind, the speed relative to the air was greater than
when it circled so as to go with the wind, and that this greater relative
velocity increased the lifting power of the aerodrome.
The total time of the flight was 57 seconds, and the distance covered was
between 2000 and 2500 feet, thus giving a speed of a little less than 30
miles an hour. Comparing this flight with that of November 28, 1896, made
by the same machine, it will be noted that in the earlier flight the velocity
was practically the same, but that the time of flight and the distance
traversed then were nearly twice as great as in the present case.
A complete record of the details, not only of weight, but also of the
position of the wings, the center of gravity, etc., which show the exact
condition of the aerodrome when it made this flight, will be found in the
appendix (Data Sheet, No. 3).
J UNE 13— AERODROME NO. 6
In the flight of June 7 there was a slight trembling of the aerodrome
while it was in the air, and although this was probably due to the fact that
the synchronizing gear was out of operation on account of the shearing off
of one of the pins which held it, allowing the port engine to run faster than
the starboard one, it was thought possible that some of the trembling might
be due to the “wind-vane” rudder, which had been added to represent the
equivalent of a steering device by which the operator would control the
direction of the large machine. It was decided, therefore, to omit the “wind-
vane” rudder in the present test, but to test the aerodrome with the same
equipment of single-tier wings and Pénaud tail that had been used in the
propeller shaft had been sheared off. This had evidently happened while the
aerodrome was still on the launching apparatus. The effect of this was to
throw the total work of the water-circulating pump on the starboard engine,
thus giving the port engine less work to do, and consequently making the
port propeller run much faster than the starboard one, and thereby causing
the peculiar and erratic circling of the aerodrome. It is evident that the
undulatory motion of the [p137] aerodrome was due to the fact that, when it
was moving against the wind, the speed relative to the air was greater than
when it circled so as to go with the wind, and that this greater relative
velocity increased the lifting power of the aerodrome.
The total time of the flight was 57 seconds, and the distance covered was
between 2000 and 2500 feet, thus giving a speed of a little less than 30
miles an hour. Comparing this flight with that of November 28, 1896, made
by the same machine, it will be noted that in the earlier flight the velocity
was practically the same, but that the time of flight and the distance
traversed then were nearly twice as great as in the present case.
A complete record of the details, not only of weight, but also of the
position of the wings, the center of gravity, etc., which show the exact
condition of the aerodrome when it made this flight, will be found in the
appendix (Data Sheet, No. 3).
J UNE 13— AERODROME NO. 6
In the flight of June 7 there was a slight trembling of the aerodrome
while it was in the air, and although this was probably due to the fact that
the synchronizing gear was out of operation on account of the shearing off
of one of the pins which held it, allowing the port engine to run faster than
the starboard one, it was thought possible that some of the trembling might
be due to the “wind-vane” rudder, which had been added to represent the
equivalent of a steering device by which the operator would control the
direction of the large machine. It was decided, therefore, to omit the “wind-
vane” rudder in the present test, but to test the aerodrome with the same
equipment of single-tier wings and Pénaud tail that had been used in the
Page 245
previous flight, the reel and float being moved to bring the CG the same as
on June 7.
Everything being in readiness, with the launching track pointed south,
and the wind blowing only about 5 12 miles an hour from the southwest, the
burners were lighted and 63 seconds were consumed before the steam
pressure rose to 100 pounds. Although the valve which controlled the
burner was open to its full extent the pressure showed no tendency to rise
above 100 pounds, which was not considered quite high enough to furnish
sufficient power for a successful flight, but as it was desired to determine at
once at how low a steam pressure the aerodrome would fly successfully, it
was decided to launch it even at this pressure. The launching apparatus was
accordingly released and the aerodrome started off, gliding down about
three feet immediately after being released, and then rising again, turning
slightly to the right and then heading directly for the Virginia shore, where
it seemed that it would smash itself in the heavy growth of timber, but when
it was about 250 feet from the shore it turned towards the right and started
back towards the island. The wind, however, which was blowing from its
rear, evidently got down the smoke-stack and put out the fire, [p138] for the
aerodrome commenced to descend as soon as it turned its back to the wind,
and came down in the channel of the creek. The path of this flight is shown
by the solid line in Plate 34.
The total distance covered, as measured by plotting the course of its
flight on the coast-survey chart, was about 1800 feet, and the length of time
of flight was 40 seconds. The aerodrome was immediately recovered and
brought into the house-boat, where it was found that there were still about
1000 grammes of water and 100 grammes of fuel unused in it, showing
conclusively that the fire had been put out by the wind.
Upon inspection it was found that the aerodrome was uninjured, and
although the burner had not worked at all satisfactorily, yet as the weather
was exceedingly favorable it was decided to make another trial with it
immediately, using the superposed wings.39
on June 7.
Everything being in readiness, with the launching track pointed south,
and the wind blowing only about 5 12 miles an hour from the southwest, the
burners were lighted and 63 seconds were consumed before the steam
pressure rose to 100 pounds. Although the valve which controlled the
burner was open to its full extent the pressure showed no tendency to rise
above 100 pounds, which was not considered quite high enough to furnish
sufficient power for a successful flight, but as it was desired to determine at
once at how low a steam pressure the aerodrome would fly successfully, it
was decided to launch it even at this pressure. The launching apparatus was
accordingly released and the aerodrome started off, gliding down about
three feet immediately after being released, and then rising again, turning
slightly to the right and then heading directly for the Virginia shore, where
it seemed that it would smash itself in the heavy growth of timber, but when
it was about 250 feet from the shore it turned towards the right and started
back towards the island. The wind, however, which was blowing from its
rear, evidently got down the smoke-stack and put out the fire, [p138] for the
aerodrome commenced to descend as soon as it turned its back to the wind,
and came down in the channel of the creek. The path of this flight is shown
by the solid line in Plate 34.
The total distance covered, as measured by plotting the course of its
flight on the coast-survey chart, was about 1800 feet, and the length of time
of flight was 40 seconds. The aerodrome was immediately recovered and
brought into the house-boat, where it was found that there were still about
1000 grammes of water and 100 grammes of fuel unused in it, showing
conclusively that the fire had been put out by the wind.
Upon inspection it was found that the aerodrome was uninjured, and
although the burner had not worked at all satisfactorily, yet as the weather
was exceedingly favorable it was decided to make another trial with it
immediately, using the superposed wings.39
Page 246
Everything being in readiness the burners were lighted, and 70 seconds
were consumed before the pressure rose to 90 pounds, beyond which it was
impossible to make it rise. Although it was felt certain that 90 pounds was
not sufficient pressure to furnish the power necessary, yet as a storm was
approaching in the distance, it was decided to launch the aerodrome, as it
could at least be determined whether it was properly balanced for the
superposed wings. When a total of 75 seconds had been consumed the car
was released and the aerodrome was launched. The wooden arrangement
for pressing down on the top of the wings to keep the aerodrome from being
injured by the wind while it was on the car had been raised to the proper
height for the superposed wings, but it had not been noticed that the sticks
which support this arrangement had been elevated so much that they would
come in contact with the beam extending across the boat, and from which
the launching track was supported. Just as these sticks reached the cross-
beam, however, it was noticed that they projected about three inches above
the lower side of it; but the next moment they struck it, and although the
force with which the car was running broke all four of them, the blow was
sufficient to slow down the car, and thereby cause the aerodrome to be
launched at a very greatly reduced speed; not over one-fifth of what it
should have been. The shock of breaking these sticks evidently jarred the
burners so that the fire was extinguished, for the aerodrome shot forward
for about 25 feet and settled with everything intact, and with its midrod
perfectly horizontal. The aerodrome itself sustained absolutely no injury,
coming down as easily as though it had been lowered by a rope, and would
have been given another trial immediately but for the fact that it was very
late in the afternoon and darkness was rapidly approaching. The data on
setting of wings, tail, etc., are shown on Data Sheet No. 4 (Appendix). [p139]
J UNE 22— AERODROME NO. 6
After several days’ delay, due to numerous small but exceedingly
annoying troubles,—such as the leaking of boilers because of defects in the
copper tubing, and the bursting of the air tank, due to its being pumped up
to an excessive pressure, which a defective pressure gauge had failed to
were consumed before the pressure rose to 90 pounds, beyond which it was
impossible to make it rise. Although it was felt certain that 90 pounds was
not sufficient pressure to furnish the power necessary, yet as a storm was
approaching in the distance, it was decided to launch the aerodrome, as it
could at least be determined whether it was properly balanced for the
superposed wings. When a total of 75 seconds had been consumed the car
was released and the aerodrome was launched. The wooden arrangement
for pressing down on the top of the wings to keep the aerodrome from being
injured by the wind while it was on the car had been raised to the proper
height for the superposed wings, but it had not been noticed that the sticks
which support this arrangement had been elevated so much that they would
come in contact with the beam extending across the boat, and from which
the launching track was supported. Just as these sticks reached the cross-
beam, however, it was noticed that they projected about three inches above
the lower side of it; but the next moment they struck it, and although the
force with which the car was running broke all four of them, the blow was
sufficient to slow down the car, and thereby cause the aerodrome to be
launched at a very greatly reduced speed; not over one-fifth of what it
should have been. The shock of breaking these sticks evidently jarred the
burners so that the fire was extinguished, for the aerodrome shot forward
for about 25 feet and settled with everything intact, and with its midrod
perfectly horizontal. The aerodrome itself sustained absolutely no injury,
coming down as easily as though it had been lowered by a rope, and would
have been given another trial immediately but for the fact that it was very
late in the afternoon and darkness was rapidly approaching. The data on
setting of wings, tail, etc., are shown on Data Sheet No. 4 (Appendix). [p139]
J UNE 22— AERODROME NO. 6
After several days’ delay, due to numerous small but exceedingly
annoying troubles,—such as the leaking of boilers because of defects in the
copper tubing, and the bursting of the air tank, due to its being pumped up
to an excessive pressure, which a defective pressure gauge had failed to
Page 247
indicate,-—Aerodrome No. 6 was made ready for another trial, and it was
decided to test it again with the superposed wings which had been used in
the second experiment of June 13. The aerodrome was mounted on the
“overhead” launching apparatus, which it will be remembered had been
used in all the previous tests, and after 90 seconds had been consumed in
raising a steam pressure of 110 pounds, it was launched directly into the
wind, which was due south. After leaving the launching car, the aerodrome
flew straight ahead for about 75 feet, when it suddenly turned its bow up
into the air at an angle of about 15 degrees, and it seemed that the machine
would be blown back onto the house-boat. However, when the rear end of
the tail was within about 10 feet of the boat, and only about 10 feet above
the water, it suddenly regained its equilibrium and went straight ahead again
in the face of the wind with the guy-posts only about 4 feet above the
surface of the water, flying almost exactly horizontally for a distance of
about 100 feet, when the bow again suddenly became elevated. As the
aerodrome was so close to the water, the wind forced it down until the
burners were extinguished by coming in contact with the water. This
brought the aerodrome to a standstill absolutely uninjured, the propellers
being several inches above the water when they quit turning. The
aerodrome was brought into the house-boat and thoroughly dried out, and
another trial would have been made with it immediately but the wind which
had been steadily increasing was now blowing something more than 12
miles an hour, and it was considered best not to attempt experiments in so
strong and gusty a wind, for fear of the wings being broken by the wind
suddenly veering and striking them on the side or rear while the aerodrome
was still on the launching apparatus. The peculiar action of the aerodrome
in the air appeared to be due to the fact that the propellers interfered more
with the lifting power of the rear superposed wings, as they were then
constructed, than they did with the “single-tier” ones. The data on the
setting of the wings, tail, etc., are shown on Data Sheet No. 5 (Appendix).
It was also found after the experiment that one of the workmen, in
assembling the machine on the launching car, had secretly increased the
stiffness of the spring which controls the elasticity of the Pénaud tail. The
decided to test it again with the superposed wings which had been used in
the second experiment of June 13. The aerodrome was mounted on the
“overhead” launching apparatus, which it will be remembered had been
used in all the previous tests, and after 90 seconds had been consumed in
raising a steam pressure of 110 pounds, it was launched directly into the
wind, which was due south. After leaving the launching car, the aerodrome
flew straight ahead for about 75 feet, when it suddenly turned its bow up
into the air at an angle of about 15 degrees, and it seemed that the machine
would be blown back onto the house-boat. However, when the rear end of
the tail was within about 10 feet of the boat, and only about 10 feet above
the water, it suddenly regained its equilibrium and went straight ahead again
in the face of the wind with the guy-posts only about 4 feet above the
surface of the water, flying almost exactly horizontally for a distance of
about 100 feet, when the bow again suddenly became elevated. As the
aerodrome was so close to the water, the wind forced it down until the
burners were extinguished by coming in contact with the water. This
brought the aerodrome to a standstill absolutely uninjured, the propellers
being several inches above the water when they quit turning. The
aerodrome was brought into the house-boat and thoroughly dried out, and
another trial would have been made with it immediately but the wind which
had been steadily increasing was now blowing something more than 12
miles an hour, and it was considered best not to attempt experiments in so
strong and gusty a wind, for fear of the wings being broken by the wind
suddenly veering and striking them on the side or rear while the aerodrome
was still on the launching apparatus. The peculiar action of the aerodrome
in the air appeared to be due to the fact that the propellers interfered more
with the lifting power of the rear superposed wings, as they were then
constructed, than they did with the “single-tier” ones. The data on the
setting of the wings, tail, etc., are shown on Data Sheet No. 5 (Appendix).
It was also found after the experiment that one of the workmen, in
assembling the machine on the launching car, had secretly increased the
stiffness of the spring which controls the elasticity of the Pénaud tail. The
Page 248
effect of this increase in the stiffness of the Pénaud tail might at first
thought appear to be similar to that of moving the center of pressure
forward. Upon a closer analysis, however, it will be seen that the effect is
very much greater, as excessive stiffness of the Pénaud tail not only causes
the aerodrome to elevate its bow, [p140] but requires the overcoming of a
strong downward force at the rear, even more serious than would be caused
by placing an extra load at the rear of the machine without regard to its
effect on the balancing. In experiments of this kind, however, the workmen
get certain ideas of their own as to how the work should be conducted, and
it is almost impossible in assembling the aerodrome to prevent them from
making adjustments which are quite different from those which they have
been directed to make, and which have been definitely planned with a view
to determining the effect of slight changes which it is desired shall not be
masked by changes of any kind in other details.
J UNE 23— AERODROME NO. 6
The wind, which had been blowing half a gale all day, gradually quieted
down towards sunset and at five o’clock was very light, blowing only two
miles an hour from the east-southeast. As one of the rear superposed wings
had been injured on the previous day in carrying the aerodrome into the
house-boat after its short and erratic flight, it was decided to use the
“single-tier” wings in this experiment, and also to continue using the
“overhead” launching apparatus for a few more flights. Everything being in
readiness, the burners were lighted and 70 seconds were consumed in
raising a steam pressure of 120 pounds, at which pressure the aerodrome
was launched. It started straight ahead, dropping not more than a foot, and
flying on an absolutely even keel for about 800 feet, when it suddenly
turned to the left and made a short half circle of about 100 feet diameter,
heading for a point about 150 feet east of the house-boat. When it was about
200 feet from the shore, a sudden gust of wind caught under the Pénaud tail,
raising the rear portion of the aerodrome and causing the bow to point down
at an angle of about 30 degrees. The aerodrome kept this angle and struck
the shallow water only about 20 feet from the shore. The aerodrome was
thought appear to be similar to that of moving the center of pressure
forward. Upon a closer analysis, however, it will be seen that the effect is
very much greater, as excessive stiffness of the Pénaud tail not only causes
the aerodrome to elevate its bow, [p140] but requires the overcoming of a
strong downward force at the rear, even more serious than would be caused
by placing an extra load at the rear of the machine without regard to its
effect on the balancing. In experiments of this kind, however, the workmen
get certain ideas of their own as to how the work should be conducted, and
it is almost impossible in assembling the aerodrome to prevent them from
making adjustments which are quite different from those which they have
been directed to make, and which have been definitely planned with a view
to determining the effect of slight changes which it is desired shall not be
masked by changes of any kind in other details.
J UNE 23— AERODROME NO. 6
The wind, which had been blowing half a gale all day, gradually quieted
down towards sunset and at five o’clock was very light, blowing only two
miles an hour from the east-southeast. As one of the rear superposed wings
had been injured on the previous day in carrying the aerodrome into the
house-boat after its short and erratic flight, it was decided to use the
“single-tier” wings in this experiment, and also to continue using the
“overhead” launching apparatus for a few more flights. Everything being in
readiness, the burners were lighted and 70 seconds were consumed in
raising a steam pressure of 120 pounds, at which pressure the aerodrome
was launched. It started straight ahead, dropping not more than a foot, and
flying on an absolutely even keel for about 800 feet, when it suddenly
turned to the left and made a short half circle of about 100 feet diameter,
heading for a point about 150 feet east of the house-boat. When it was about
200 feet from the shore, a sudden gust of wind caught under the Pénaud tail,
raising the rear portion of the aerodrome and causing the bow to point down
at an angle of about 30 degrees. The aerodrome kept this angle and struck
the shallow water only about 20 feet from the shore. The aerodrome was
Page 249
comparatively uninjured, and another flight would have been made
immediately but for the fact that by the time the aerodrome had been
properly inspected it was quite late, and entirely too dark, and there would
have been danger of losing it in the adjacent marshes, which are difficult to
traverse even under the best conditions of tide and light. The path of this
flight is shown by the dotted line in Plate 34.
J UNE 27— AERODROME NO. 5
While the preceding tests had been going on with Aerodrome No. 6, such
time as could be spared for it was spent in getting Aerodrome No. 5 into
proper condition. The copper tubing from which the boilers for both
aerodromes were made was greatly inferior to that which had been used in
previous years, and as this tubing could be procured only by having it
specially drawn to order in France, and as it required several months after
placing an order before the [p141] tubing could be delivered, it was necessary
to make the best of what was already on hand. The copper tubing for the
boilers which had been used in 1896, after being carefully annealed and
filled with fine sand, could be wound into a perfectly smooth helix, free
from all wrinkles, indentations, and so forth, on the inner side of the coil.
But no amount of care, both in annealing and in winding this present lot of
tubing, would produce a smooth helix, the tubing being badly wrinkled on
the inner side of the coil in spite of every precaution. These wrinkles,
however, were not so much the cause of serious trouble as was the fact that
the tubing was not uniform in quality, each length of it having numerous
rotten spots which did not always show up in the winding, but which gave
way after the boiler had been completed and one or two preliminary runs in
the shop had been made with it. While the effect of such small things
cannot be appreciated from merely reading about them, yet they were the
cause of the most exasperating annoyance and delay, as no sooner had the
aerodrome been gotten into what appeared to be perfect working order than
the boiler would break at one or more points, thus causing a delay which at
the moment would seem to involve not more than a few hours, but before
everything was again in working order would amount to several days.
immediately but for the fact that by the time the aerodrome had been
properly inspected it was quite late, and entirely too dark, and there would
have been danger of losing it in the adjacent marshes, which are difficult to
traverse even under the best conditions of tide and light. The path of this
flight is shown by the dotted line in Plate 34.
J UNE 27— AERODROME NO. 5
While the preceding tests had been going on with Aerodrome No. 6, such
time as could be spared for it was spent in getting Aerodrome No. 5 into
proper condition. The copper tubing from which the boilers for both
aerodromes were made was greatly inferior to that which had been used in
previous years, and as this tubing could be procured only by having it
specially drawn to order in France, and as it required several months after
placing an order before the [p141] tubing could be delivered, it was necessary
to make the best of what was already on hand. The copper tubing for the
boilers which had been used in 1896, after being carefully annealed and
filled with fine sand, could be wound into a perfectly smooth helix, free
from all wrinkles, indentations, and so forth, on the inner side of the coil.
But no amount of care, both in annealing and in winding this present lot of
tubing, would produce a smooth helix, the tubing being badly wrinkled on
the inner side of the coil in spite of every precaution. These wrinkles,
however, were not so much the cause of serious trouble as was the fact that
the tubing was not uniform in quality, each length of it having numerous
rotten spots which did not always show up in the winding, but which gave
way after the boiler had been completed and one or two preliminary runs in
the shop had been made with it. While the effect of such small things
cannot be appreciated from merely reading about them, yet they were the
cause of the most exasperating annoyance and delay, as no sooner had the
aerodrome been gotten into what appeared to be perfect working order than
the boiler would break at one or more points, thus causing a delay which at
the moment would seem to involve not more than a few hours, but before
everything was again in working order would amount to several days.
Page 250
PL. 34. PATHS OF FLIGHT OF AERODROME NO. 6, JUNE 13 AND 23, 1899 ◊
However, after much perseverance, Aerodrome No. 5 was put in
satisfactory working condition, and on June 27 was launched with its
However, after much perseverance, Aerodrome No. 5 was put in
satisfactory working condition, and on June 27 was launched with its
Page 251
“single-tier” wings and Pénaud tail. The data on settings of wings, tail, etc.,
are given on Data Sheet No. 6. After lighting the burners, 70 seconds were
consumed in raising a steam pressure of 120 pounds. Immediately upon
leaving the launching car the aerodrome started to rise with its bow elevated
to an angle of about 15 degrees. It flew straight ahead about 80 feet, when it
came backward and downward and touched the water about 40 feet from
the boat. The failure of the aerodrome to fly properly was evidently due to
its not being in proper balance. The cause of this lack of proper balance was
not immediately apparent, but was very soon detected and will be discussed
later on.
J UNE 30— AERODROME NO. 5
After several days of incessant rain and strong winds, which prevented an
experiment, the weather became brighter and the wind quieted down and
the afternoon of June 30 was almost ideal for an experiment. At five o’clock
Aerodrome No. 5, with “single-tier” wings and Pénaud tail, was placed on
the launching apparatus, a few minutes later the burners were lighted, and
just as the propellers started to turn a racking noise was heard. Upon
investigation it was found that the circulating pump had broken. The break
was a very small matter and could have been repaired in an hour, but it was
then too late to repair the damage and get a flight before dark, so the
aerodrome was reluctantly dismounted and the men put to work repairing
the broken pump. [p142]
J ULY 1 TO J ULY 8
The great disadvantage of conducting the experiments at a point forty
miles from the city and the shops was felt at all times. Workmen, even of
the very best class, cannot be kept contentedly at work at a point so far
removed from their homes, even by bringing them to the city on Saturday
afternoon and carrying them back to the experimental grounds the
following Monday. Moreover, it is worse than useless to try to get even as
much as one-third the ordinary amount of work done if there is the slightest
are given on Data Sheet No. 6. After lighting the burners, 70 seconds were
consumed in raising a steam pressure of 120 pounds. Immediately upon
leaving the launching car the aerodrome started to rise with its bow elevated
to an angle of about 15 degrees. It flew straight ahead about 80 feet, when it
came backward and downward and touched the water about 40 feet from
the boat. The failure of the aerodrome to fly properly was evidently due to
its not being in proper balance. The cause of this lack of proper balance was
not immediately apparent, but was very soon detected and will be discussed
later on.
J UNE 30— AERODROME NO. 5
After several days of incessant rain and strong winds, which prevented an
experiment, the weather became brighter and the wind quieted down and
the afternoon of June 30 was almost ideal for an experiment. At five o’clock
Aerodrome No. 5, with “single-tier” wings and Pénaud tail, was placed on
the launching apparatus, a few minutes later the burners were lighted, and
just as the propellers started to turn a racking noise was heard. Upon
investigation it was found that the circulating pump had broken. The break
was a very small matter and could have been repaired in an hour, but it was
then too late to repair the damage and get a flight before dark, so the
aerodrome was reluctantly dismounted and the men put to work repairing
the broken pump. [p142]
J ULY 1 TO J ULY 8
The great disadvantage of conducting the experiments at a point forty
miles from the city and the shops was felt at all times. Workmen, even of
the very best class, cannot be kept contentedly at work at a point so far
removed from their homes, even by bringing them to the city on Saturday
afternoon and carrying them back to the experimental grounds the
following Monday. Moreover, it is worse than useless to try to get even as
much as one-third the ordinary amount of work done if there is the slightest
Page 252
excuse for tightening anchor ropes, watching passing boats, or wasting time
on any of the multitudinous small variations from their usual routine of life.
On July 7, Aerodrome No. 5, equipped with “single-tier” wings and
Pénaud tail, was made ready for a flight in the afternoon. The settings of the
wings, tail, etc., are given on Data Sheet 6. Using the “overhead” launching
apparatus, the aerodrome was launched with a steam pressure of 115
pounds. Immediately upon being launched its bow rose to an angle of about
fifteen degrees or more, and the aerodrome came backward and downward
and touched the water about three or four feet from the house-boat.
It may be well to recall from what has been said in Part I, Chapter IX ◊,
that Aerodrome No. 5 is the one with the very low thrust line, and in 1896
had its “separator” several centimetres in front of its center of gravity.
When this aerodrome was overhauled just previous to these experiments,
the separator was moved back to the same relative position as that in
Aerodrome No. 6, so that the gradual depletion of the water supply during
flight would not cause it to become light in front of the center of gravity.
In the launching of Aerodrome No. 5, above described, it showed no
tendency to drop immediately upon leaving the launching ways, but on the
contrary its bow in every case rose almost immediately until it was at an
angle of about fifteen degrees or more. From the photograph (Plate 35) it
will be noticed that the wings of the aerodrome are held down by the
longitudinal strips, A, fastened to cross-beams attached to the launching car.
If, now, the launching speed is too great and the aerodrome tries to rise
immediately upon being released, the front end, which passes from under
the launching car before the rear does, and is thus free to rise, will
immediately rise, while the rear cannot rise until it has passed entirely in
front of the car, which being a distance of several feet requires an
appreciable fraction of a second, during which time the bow of the machine
has been able to rise to quite a steep angle. This has the effect of slowing
down the aerodrome so that it does not get quite the proper chance to start
on its flight with a minimum head resistance.
In view of the above facts, it was decided to decrease the speed of the
launching car slightly when using Aerodrome No. 5, so that this matter
on any of the multitudinous small variations from their usual routine of life.
On July 7, Aerodrome No. 5, equipped with “single-tier” wings and
Pénaud tail, was made ready for a flight in the afternoon. The settings of the
wings, tail, etc., are given on Data Sheet 6. Using the “overhead” launching
apparatus, the aerodrome was launched with a steam pressure of 115
pounds. Immediately upon being launched its bow rose to an angle of about
fifteen degrees or more, and the aerodrome came backward and downward
and touched the water about three or four feet from the house-boat.
It may be well to recall from what has been said in Part I, Chapter IX ◊,
that Aerodrome No. 5 is the one with the very low thrust line, and in 1896
had its “separator” several centimetres in front of its center of gravity.
When this aerodrome was overhauled just previous to these experiments,
the separator was moved back to the same relative position as that in
Aerodrome No. 6, so that the gradual depletion of the water supply during
flight would not cause it to become light in front of the center of gravity.
In the launching of Aerodrome No. 5, above described, it showed no
tendency to drop immediately upon leaving the launching ways, but on the
contrary its bow in every case rose almost immediately until it was at an
angle of about fifteen degrees or more. From the photograph (Plate 35) it
will be noticed that the wings of the aerodrome are held down by the
longitudinal strips, A, fastened to cross-beams attached to the launching car.
If, now, the launching speed is too great and the aerodrome tries to rise
immediately upon being released, the front end, which passes from under
the launching car before the rear does, and is thus free to rise, will
immediately rise, while the rear cannot rise until it has passed entirely in
front of the car, which being a distance of several feet requires an
appreciable fraction of a second, during which time the bow of the machine
has been able to rise to quite a steep angle. This has the effect of slowing
down the aerodrome so that it does not get quite the proper chance to start
on its flight with a minimum head resistance.
In view of the above facts, it was decided to decrease the speed of the
launching car slightly when using Aerodrome No. 5, so that this matter
Page 253
could be thoroughly tested out.
Page 254
PL. 35. AERODROME NO. 5 ON
LAUNCHING-WAYS ◊
LAUNCHING-WAYS ◊
Page 255
[p143]
J ULY 11 TO J ULY 14— AERODROME NO. 5
The very early morning preceding actual sunrise on July 11 was
undoubtedly as calm as it is possible to find; there was absolutely no breeze
stirring and the water in the river was as smooth as glass as far as one could
see. The anemometer cups were stationary, the wind vane stood absolutely
parallel to the launching apparatus and everything promised a most
successful experiment. After mounting the aerodrome on the “overhead”
launching apparatus the burner was lighted, and while the steam pressure
was still rising and the propellers were revolving faster and faster all the
time, there was a snap and they ceased to turn. The fire, which was burning
fiercely, ran the pressure immediately to 150 pounds. An attempt was at
once made to start the propellers again by giving them an initial turn by
hand, it being thought possible that a sudden gush of water had taken place
and, accumulating in one end of the engine cylinder, had blocked the
engine. However, as the engine refused to keep the propellers going after
they were started, and as the pressure was still rising very rapidly, the
burner was shut off and an investigation made. Upon removing the hull
covering, it was found that the connecting rod bearing had broken off short
near the crank pin of the engine, and that it would be necessary to take the
part to Washington in order to repair it, as there were no machine tools on
the house-boat.
After several days of exceedingly bad weather, the conditions grew more
favorable. Late in the afternoon of July 14, Aerodrome No. 5 was again
placed on the “overhead” launching apparatus and prepared for a trial. After
lighting the burners, 95 seconds were required to raise a steam pressure of
120 pounds. Upon leaving the launching apparatus the aerodrome went
directly ahead for a few feet, but immediately commenced to rise, elevating
its bow to an angle of 20 degrees by the time it had travelled 40 feet. With
its bow in this position, it was blown back towards the house-boat and a
little to the right of it, and, when within about 5 feet of the water, suddenly
righted itself and started ahead again, rising all the time and reaching a
J ULY 11 TO J ULY 14— AERODROME NO. 5
The very early morning preceding actual sunrise on July 11 was
undoubtedly as calm as it is possible to find; there was absolutely no breeze
stirring and the water in the river was as smooth as glass as far as one could
see. The anemometer cups were stationary, the wind vane stood absolutely
parallel to the launching apparatus and everything promised a most
successful experiment. After mounting the aerodrome on the “overhead”
launching apparatus the burner was lighted, and while the steam pressure
was still rising and the propellers were revolving faster and faster all the
time, there was a snap and they ceased to turn. The fire, which was burning
fiercely, ran the pressure immediately to 150 pounds. An attempt was at
once made to start the propellers again by giving them an initial turn by
hand, it being thought possible that a sudden gush of water had taken place
and, accumulating in one end of the engine cylinder, had blocked the
engine. However, as the engine refused to keep the propellers going after
they were started, and as the pressure was still rising very rapidly, the
burner was shut off and an investigation made. Upon removing the hull
covering, it was found that the connecting rod bearing had broken off short
near the crank pin of the engine, and that it would be necessary to take the
part to Washington in order to repair it, as there were no machine tools on
the house-boat.
After several days of exceedingly bad weather, the conditions grew more
favorable. Late in the afternoon of July 14, Aerodrome No. 5 was again
placed on the “overhead” launching apparatus and prepared for a trial. After
lighting the burners, 95 seconds were required to raise a steam pressure of
120 pounds. Upon leaving the launching apparatus the aerodrome went
directly ahead for a few feet, but immediately commenced to rise, elevating
its bow to an angle of 20 degrees by the time it had travelled 40 feet. With
its bow in this position, it was blown back towards the house-boat and a
little to the right of it, and, when within about 5 feet of the water, suddenly
righted itself and started ahead again, rising all the time and reaching a
Page 256
height of about 20 feet by the time it had travelled 100 feet. In the
meantime the bow had again become elevated to an angle of about 15
degrees and the aerodrome was blown backwards and downwards again.
Just before reaching the water it started to right itself, but it had descended
so that the front guy-post was in the water, thus destroying its equilibrium
and causing it to settle into the water. The path of this flight is shown by the
peculiar S-shaped line in Plate 34.
In the adjustments preliminary to the above trial the Pénaud tail was
elevated to an angle of 7 12 degrees when the aerodrome was stationary in the
shop. This excessive elevation, coupled with the fact that the center of
gravity was also probably a little too far forward, no doubt accounts for the
erratic flight. The data on setting of wings, tail, etc., are given on Data
Sheet No. 7 (Appendix). [p144]
J ULY 19— AERODROME NO. 5
After several days of exceedingly bad weather the conditions were more
favorable on July 19. Since the last experiment on July 14 the coefficient of
elasticity of the Pénaud tail had been decreased, the rear wings moved back
5 centimetres, and the “float” so placed that the center of gravity of the
machine was brought to the same position it had had on that day, that is, 2
centimetres back of the line of thrust. With this arrangement, assuming that
the CP is over the CG, we should have an apparent efficiency of the rear
wings of 63.6 per cent, since the distance between CPfw, and CG is 79.7
centimetres, and the distance between CPrw and CG is 125.3 centimetres.
With the adjustment of July 14, the distance between CPfw and CG was
79.7 centimetres, and the distance between CPrw and CG was 118.3
centimetres, thus allowing for an apparent efficiency of 67.37 per cent for
the rear wings. It will be recalled that in the unsuccessful flight of July 14
the midrod of the aerodrome was inclined at an angle of about 20 degrees
during most of the time that it was in the air, thus indicating that the front
wings were lifting proportionately more than they should. On July 14 the
Pénaud tail had a negative elevation of 7° 30′, and it required 1240
meantime the bow had again become elevated to an angle of about 15
degrees and the aerodrome was blown backwards and downwards again.
Just before reaching the water it started to right itself, but it had descended
so that the front guy-post was in the water, thus destroying its equilibrium
and causing it to settle into the water. The path of this flight is shown by the
peculiar S-shaped line in Plate 34.
In the adjustments preliminary to the above trial the Pénaud tail was
elevated to an angle of 7 12 degrees when the aerodrome was stationary in the
shop. This excessive elevation, coupled with the fact that the center of
gravity was also probably a little too far forward, no doubt accounts for the
erratic flight. The data on setting of wings, tail, etc., are given on Data
Sheet No. 7 (Appendix). [p144]
J ULY 19— AERODROME NO. 5
After several days of exceedingly bad weather the conditions were more
favorable on July 19. Since the last experiment on July 14 the coefficient of
elasticity of the Pénaud tail had been decreased, the rear wings moved back
5 centimetres, and the “float” so placed that the center of gravity of the
machine was brought to the same position it had had on that day, that is, 2
centimetres back of the line of thrust. With this arrangement, assuming that
the CP is over the CG, we should have an apparent efficiency of the rear
wings of 63.6 per cent, since the distance between CPfw, and CG is 79.7
centimetres, and the distance between CPrw and CG is 125.3 centimetres.
With the adjustment of July 14, the distance between CPfw and CG was
79.7 centimetres, and the distance between CPrw and CG was 118.3
centimetres, thus allowing for an apparent efficiency of 67.37 per cent for
the rear wings. It will be recalled that in the unsuccessful flight of July 14
the midrod of the aerodrome was inclined at an angle of about 20 degrees
during most of the time that it was in the air, thus indicating that the front
wings were lifting proportionately more than they should. On July 14 the
Pénaud tail had a negative elevation of 7° 30′, and it required 1240
Page 257
grammes placed at its center to bring it to the horizontal. On July 19 the
elevation of the tail was changed to 5° and a weaker spring for controlling
the elasticity was substituted, so that it required only 200 grammes placed at
the center of the tail to bring it to the horizontal. A rubber band, of about
one-half the strength of the upper spring, was attached by means of a cord
to the lower guy-post and the lower vertical ribs of the tail, so that the tail
would be elastic both ways. This rubber band was in place and acting to
help draw the tail down when the above measurement of the coefficient of
elasticity was made. A rubber band connected to the lower side of the tail
was also used in the flight of July 14, but it was so very weak, compared to
the upper spring, that its effect was negligible.
The effect of this change in the balancing of the aerodrome, and also the
more considerable effect which the coefficient of elasticity of the tail has on
the balancing, will be immediately noticed from the description of the next
flight. The data on setting of wings, tail, etc. are given on Data Sheet No. 8.
At 3 p. m., the wind having died down, Aerodrome No. 5, equipped with
its “single-tier” wings and Pénaud tail adjusted as above, was placed on the
“overhead” launching apparatus. After lighting the burners, one minute and
thirty seconds were required to raise a steam pressure of 120 pounds.
Immediately upon leaving the launching apparatus, the aerodrome started
straight ahead, dropping about 3 feet by the time it had gone 100 feet; it
then rose with its midrod at an angle of about 6 or 8 degrees, regaining its
level very quickly, however, and making three of these undulations by the
time it had gone [p145] 300 feet. It continued straight ahead for another 300
feet and began to circle to the left, the diameter of the first circle being
about 200 feet. As soon as it started to circle, it rose with its midrod at an
angle of about 15 degrees, and by the time it had made its first half turn it
started to descend, coming down to within 15 feet of the water. As soon,
however, as it had completed this first turn, it again rose, making another
half circle, then, upon the completion of this half turn of the second circle,
descended, this time to within 10 feet of the water, rising again for the third
half turn, but again descending to within 2 feet of the water at the
completion of this third circle, and then rising and completing the first half
elevation of the tail was changed to 5° and a weaker spring for controlling
the elasticity was substituted, so that it required only 200 grammes placed at
the center of the tail to bring it to the horizontal. A rubber band, of about
one-half the strength of the upper spring, was attached by means of a cord
to the lower guy-post and the lower vertical ribs of the tail, so that the tail
would be elastic both ways. This rubber band was in place and acting to
help draw the tail down when the above measurement of the coefficient of
elasticity was made. A rubber band connected to the lower side of the tail
was also used in the flight of July 14, but it was so very weak, compared to
the upper spring, that its effect was negligible.
The effect of this change in the balancing of the aerodrome, and also the
more considerable effect which the coefficient of elasticity of the tail has on
the balancing, will be immediately noticed from the description of the next
flight. The data on setting of wings, tail, etc. are given on Data Sheet No. 8.
At 3 p. m., the wind having died down, Aerodrome No. 5, equipped with
its “single-tier” wings and Pénaud tail adjusted as above, was placed on the
“overhead” launching apparatus. After lighting the burners, one minute and
thirty seconds were required to raise a steam pressure of 120 pounds.
Immediately upon leaving the launching apparatus, the aerodrome started
straight ahead, dropping about 3 feet by the time it had gone 100 feet; it
then rose with its midrod at an angle of about 6 or 8 degrees, regaining its
level very quickly, however, and making three of these undulations by the
time it had gone [p145] 300 feet. It continued straight ahead for another 300
feet and began to circle to the left, the diameter of the first circle being
about 200 feet. As soon as it started to circle, it rose with its midrod at an
angle of about 15 degrees, and by the time it had made its first half turn it
started to descend, coming down to within 15 feet of the water. As soon,
however, as it had completed this first turn, it again rose, making another
half circle, then, upon the completion of this half turn of the second circle,
descended, this time to within 10 feet of the water, rising again for the third
half turn, but again descending to within 2 feet of the water at the
completion of this third circle, and then rising and completing the first half
Page 258
turn of the fourth circle. By this time, however, it had sunk so near to the
water that the guy-posts caught in the tall grass while it was descending just
before the completion of the fourth circle, thus pulling the aerodrome down
into the water with the propellers still running. The total time the aerodrome
was in the air was 46 seconds. The total number of revolutions of the
propellers was 488, or at the mean rate of 637 R. P. M. Upon examining the
aerodrome, after it was recovered, it was found that there were 925
grammes of water left in the separator, the fire having been put out by the
aerodrome coming down into the water.
When the aerodrome first commenced to circle during its flight, it was
noticed that the front wing clamps had twisted on the midrod, the left wing
being dipped downwards, and the right one, of course, being elevated, and
the peculiar circling of the aerodrome was undoubtedly due to this fact. The
cause of the wing clamp twisting on the midrod was that one of the
workmen forgot to tighten one of the screws of the wing clamp when the
wings were being adjusted on the aerodrome. But for this unfortunate
twisting of the wings, it is probable that the flight would have been
perfectly straight and the distance covered would have been considerably
greater than it was, the total path traversed being about 2600 to 2800 feet,
found by plotting the path on the coast-survey chart and measuring it.
J ULY 27— AERODROME NO. 6
As the proper balancing of both Aerodrome No. 5 and No. 6 had now
been determined with reasonable accuracy, and as much more time had
already been given to the experiments than had been intended, it was
decided to dismount the “overhead” launching apparatus at once and
substitute the “underneath” one, so that it could be immediately determined
whether this newer plan for launching the aerodrome by a car supporting it
from underneath would be suitable for use with the large machine. After a
considerable period of exceedingly bad weather, during which time the
change was made in the launching apparatus, the weather conditions
became more favorable on July 27. Aerodrome No. 6, equipped with
“single-tier” wings and Pénaud tail, was mounted on the [p146] “underneath”
water that the guy-posts caught in the tall grass while it was descending just
before the completion of the fourth circle, thus pulling the aerodrome down
into the water with the propellers still running. The total time the aerodrome
was in the air was 46 seconds. The total number of revolutions of the
propellers was 488, or at the mean rate of 637 R. P. M. Upon examining the
aerodrome, after it was recovered, it was found that there were 925
grammes of water left in the separator, the fire having been put out by the
aerodrome coming down into the water.
When the aerodrome first commenced to circle during its flight, it was
noticed that the front wing clamps had twisted on the midrod, the left wing
being dipped downwards, and the right one, of course, being elevated, and
the peculiar circling of the aerodrome was undoubtedly due to this fact. The
cause of the wing clamp twisting on the midrod was that one of the
workmen forgot to tighten one of the screws of the wing clamp when the
wings were being adjusted on the aerodrome. But for this unfortunate
twisting of the wings, it is probable that the flight would have been
perfectly straight and the distance covered would have been considerably
greater than it was, the total path traversed being about 2600 to 2800 feet,
found by plotting the path on the coast-survey chart and measuring it.
J ULY 27— AERODROME NO. 6
As the proper balancing of both Aerodrome No. 5 and No. 6 had now
been determined with reasonable accuracy, and as much more time had
already been given to the experiments than had been intended, it was
decided to dismount the “overhead” launching apparatus at once and
substitute the “underneath” one, so that it could be immediately determined
whether this newer plan for launching the aerodrome by a car supporting it
from underneath would be suitable for use with the large machine. After a
considerable period of exceedingly bad weather, during which time the
change was made in the launching apparatus, the weather conditions
became more favorable on July 27. Aerodrome No. 6, equipped with
“single-tier” wings and Pénaud tail, was mounted on the [p146] “underneath”
Page 259
launching apparatus, and everything was got ready for a flight. On lighting
the burners, they failed to work properly, and, upon investigation, it was
found that the air valve controlling the air pressure on the gasoline tank,
was out of order. While this was being repaired, the wind rapidly increased
in velocity and became very gusty, thus endangering the aerodrome, as the
wings were very liable to be broken by the wind suddenly veering more
rapidly than the house-boat could turn or the turn-table could be moved, and
thus striking the wings from the side and putting an enormous upward
pressure on them, owing to the fact that the diedral angle between them
gave to each wing an elevation of 7 12 degrees from the horizontal. The
aerodrome was accordingly dismounted and everything kept in readiness
for a trial, with the hope that the wind would die down, or at least become
steady, but it did not do so until after dark.
J ULY 28— AERODROME NO. 6
Aerodrome No. 6, equipped with “single-tier” wings and Pénaud tail, was
launched from the “underneath” launching apparatus. There was a dead
calm, the river not showing a ripple; the wind vane pointed to the northeast,
but as the tide was low and the boat was aground, the launching track was
pointing due south. At 7 a. m. the burners were lighted, and 80 seconds
were consumed in raising a steam pressure of 120 pounds. Everything
worked perfectly; the uprights on the car, which initially support the
aerodrome and upon its being released are instantaneously pulled down by
rubber springs, as well as the disappearing part of the track, acted without
the slightest hitch. Immediately upon leaving the launching apparatus, the
aerodrome depressed its bow to an angle of between 3 and 4 degrees and
made a direct line for the water. At this angle it struck just on the opposite
side of the channel, about 300 feet from the house-boat, and while several
minor parts, such as guy-posts, were injured no damage of importance was
done. Owing to the difficulty of getting through the marsh and recovering
Aerodrome No. 6, it was found impossible to make another trial with No. 5
before the wind had increased to a prohibitive velocity. The path of this
the burners, they failed to work properly, and, upon investigation, it was
found that the air valve controlling the air pressure on the gasoline tank,
was out of order. While this was being repaired, the wind rapidly increased
in velocity and became very gusty, thus endangering the aerodrome, as the
wings were very liable to be broken by the wind suddenly veering more
rapidly than the house-boat could turn or the turn-table could be moved, and
thus striking the wings from the side and putting an enormous upward
pressure on them, owing to the fact that the diedral angle between them
gave to each wing an elevation of 7 12 degrees from the horizontal. The
aerodrome was accordingly dismounted and everything kept in readiness
for a trial, with the hope that the wind would die down, or at least become
steady, but it did not do so until after dark.
J ULY 28— AERODROME NO. 6
Aerodrome No. 6, equipped with “single-tier” wings and Pénaud tail, was
launched from the “underneath” launching apparatus. There was a dead
calm, the river not showing a ripple; the wind vane pointed to the northeast,
but as the tide was low and the boat was aground, the launching track was
pointing due south. At 7 a. m. the burners were lighted, and 80 seconds
were consumed in raising a steam pressure of 120 pounds. Everything
worked perfectly; the uprights on the car, which initially support the
aerodrome and upon its being released are instantaneously pulled down by
rubber springs, as well as the disappearing part of the track, acted without
the slightest hitch. Immediately upon leaving the launching apparatus, the
aerodrome depressed its bow to an angle of between 3 and 4 degrees and
made a direct line for the water. At this angle it struck just on the opposite
side of the channel, about 300 feet from the house-boat, and while several
minor parts, such as guy-posts, were injured no damage of importance was
done. Owing to the difficulty of getting through the marsh and recovering
Aerodrome No. 6, it was found impossible to make another trial with No. 5
before the wind had increased to a prohibitive velocity. The path of this
Page 260
flight is shown by the dotted line in Plate 36. The data on setting of wings,
tail, etc., are given on Data Sheet No. 9.
The last previous trial of Aerodrome No. 6 was made on June 23, and the
balancing at that time was evidently correct for the settings of the tail which
were then used. The Pénaud tail then had an elevation of 7 12 degrees, and
the coefficient of elasticity was such that 1240 grammes were required at
the center of the tail to deflect it to the horizontal. In the trial above
recorded, on July 28, the adjustments of the wings were practically what
they were on June 23, the CG being moved forward 1 centimetre, but the
Pénaud tail had an elevation of something less than 5 degrees, and the
coefficient of elasticity was such that [p147] 200 grammes placed at the
center were required to deflect the tail to a horizontal. It was not intended
that the angle of the tail should have been less than 5 degrees, but it was
found that one of the workmen had improperly attached the fastening wire,
and had considerably decreased the angle. This last adjustment of the
Pénaud tail should have been the same as that used on Aerodrome No. 5 in
its flight of July 19. The CG had purposely been moved forward slightly,
but the effect of moving the CG forward and at the same time decreasing
the stiffness and angle of the tail was shown by this flight.
The above trial not only very clearly emphasizes the importance of
carefully determining what the elasticity of the Pénaud tail should be, but
also emphasizes the fact that even the best workmen, who have had several
years of experience, cannot be relied on in anything which requires that
everything be done exactly right and not nearly right.
J ULY 29— AERODROME NO. 5
The aerodrome equipped with “single-tier” wings and Pénaud tail was
launched from the “underneath” launching apparatus at 9 a. m., 1 minute
and 30 seconds having been required to raise 120 pounds steam pressure.
The wind was from the southeast, with a velocity of 3 miles an hour, and
the launching track was pointed directly into it.
The launching apparatus, with the disappearing track, worked perfectly,
and the aerodrome started straight ahead, dropping slightly at first, but
tail, etc., are given on Data Sheet No. 9.
The last previous trial of Aerodrome No. 6 was made on June 23, and the
balancing at that time was evidently correct for the settings of the tail which
were then used. The Pénaud tail then had an elevation of 7 12 degrees, and
the coefficient of elasticity was such that 1240 grammes were required at
the center of the tail to deflect it to the horizontal. In the trial above
recorded, on July 28, the adjustments of the wings were practically what
they were on June 23, the CG being moved forward 1 centimetre, but the
Pénaud tail had an elevation of something less than 5 degrees, and the
coefficient of elasticity was such that [p147] 200 grammes placed at the
center were required to deflect the tail to a horizontal. It was not intended
that the angle of the tail should have been less than 5 degrees, but it was
found that one of the workmen had improperly attached the fastening wire,
and had considerably decreased the angle. This last adjustment of the
Pénaud tail should have been the same as that used on Aerodrome No. 5 in
its flight of July 19. The CG had purposely been moved forward slightly,
but the effect of moving the CG forward and at the same time decreasing
the stiffness and angle of the tail was shown by this flight.
The above trial not only very clearly emphasizes the importance of
carefully determining what the elasticity of the Pénaud tail should be, but
also emphasizes the fact that even the best workmen, who have had several
years of experience, cannot be relied on in anything which requires that
everything be done exactly right and not nearly right.
J ULY 29— AERODROME NO. 5
The aerodrome equipped with “single-tier” wings and Pénaud tail was
launched from the “underneath” launching apparatus at 9 a. m., 1 minute
and 30 seconds having been required to raise 120 pounds steam pressure.
The wind was from the southeast, with a velocity of 3 miles an hour, and
the launching track was pointed directly into it.
The launching apparatus, with the disappearing track, worked perfectly,
and the aerodrome started straight ahead, dropping slightly at first, but
Page 261
immediately regaining its level and going ahead, gradually raising its bow
to an angle of about 8 or 10 degrees, and slightly slacking up its speed by
the time it had gone about 300 feet. It then made a circle to the left of a
radius of about 75 feet and started back. As soon as it had made this turn it
regained its level and directly regained its speed. But as soon as it had
speeded up again it elevated its bow, which slackened its speed as before. It
then again righted itself, still going in the same direction and crossing the
sand-bar on the point of the island at a height of about 40 feet. As soon as it
had crossed the sand-bar, it again made a circle to the left with a radius of
about 75 feet, heading directly for the house-boat, but when it had got back
above the sand-bar it again circled to the left, passing directly between two
tall trees, and barely missing them, and still circling to the left, when it
again reached the opposite side of the sand-bar. It, however, kept on circling
to the left and once more started back towards the house-boat, this time
passing to the left of the trees and again barely missing them, and
completing this, its second, circle over the sand-bar. It then started due
north, heading directly for Quantico, but by this time something had
evidently happened to the burners as the fire went out, and the propellers
gradually slowed up. However, it kept on towards Quantico, gradually
descending on an even keel, and came down in the water at a point about
500 feet [p148] from the sand-bar and about 1000 feet from the house-boat.
The propellers had almost ceased turning when the aerodrome came down
into the water, and it settled almost as quietly as though it had been picked
up and placed there, so that no damage was done to it.
The total time that the aerodrome was in the air was 63 seconds, and the
total length of flight was about 2500 feet. The path of this flight is shown by
the dotted line with the double circle in Plate 36. The data on settings of
wings, tail, etc., are given on Data Sheet No. 10.
As soon as the workmen had had their breakfast, Aerodrome No. 5 was
again placed on the launching apparatus, equipped this time with the
superposed wings and Pénaud tail. Upon lighting the burners, it was found
that they did not work properly, a small piece of soot having clogged up the
tip of the vaporizing coil. While this trouble with the burners was being
to an angle of about 8 or 10 degrees, and slightly slacking up its speed by
the time it had gone about 300 feet. It then made a circle to the left of a
radius of about 75 feet and started back. As soon as it had made this turn it
regained its level and directly regained its speed. But as soon as it had
speeded up again it elevated its bow, which slackened its speed as before. It
then again righted itself, still going in the same direction and crossing the
sand-bar on the point of the island at a height of about 40 feet. As soon as it
had crossed the sand-bar, it again made a circle to the left with a radius of
about 75 feet, heading directly for the house-boat, but when it had got back
above the sand-bar it again circled to the left, passing directly between two
tall trees, and barely missing them, and still circling to the left, when it
again reached the opposite side of the sand-bar. It, however, kept on circling
to the left and once more started back towards the house-boat, this time
passing to the left of the trees and again barely missing them, and
completing this, its second, circle over the sand-bar. It then started due
north, heading directly for Quantico, but by this time something had
evidently happened to the burners as the fire went out, and the propellers
gradually slowed up. However, it kept on towards Quantico, gradually
descending on an even keel, and came down in the water at a point about
500 feet [p148] from the sand-bar and about 1000 feet from the house-boat.
The propellers had almost ceased turning when the aerodrome came down
into the water, and it settled almost as quietly as though it had been picked
up and placed there, so that no damage was done to it.
The total time that the aerodrome was in the air was 63 seconds, and the
total length of flight was about 2500 feet. The path of this flight is shown by
the dotted line with the double circle in Plate 36. The data on settings of
wings, tail, etc., are given on Data Sheet No. 10.
As soon as the workmen had had their breakfast, Aerodrome No. 5 was
again placed on the launching apparatus, equipped this time with the
superposed wings and Pénaud tail. Upon lighting the burners, it was found
that they did not work properly, a small piece of soot having clogged up the
tip of the vaporizing coil. While this trouble with the burners was being
Page 262
remedied, the wind increased to such an extent that it was found necessary
to remove the aerodrome from the launching apparatus to prevent its being
injured by side gusts. As it was Saturday and the wind showed no signs of
quieting down, the experiments were discontinued until the next week.
A UGUST 1— AERODROME NO. 5
After placing the aerodrome on the launching apparatus and getting
everything in readiness for a flight, upon lighting the burners a sudden sheet
of flame shot out of the smoke-stack and so seriously charred three panels
of each of the rear wings that they had to be removed for repairs. The silk
covering of the wings had been coated with a special fire-proofing
preparation, but the intensely hot flame, of course, charred all the silk that it
came in contact with.
By the time that the wings had been repaired, and the defect in the burner
which caused the accident had been remedied, a severe storm had arisen,
making it necessary to remove everything to the interior of the boat. While
waiting for the weather to become more suitable, a test of the engine of
Aerodrome No. 5 was made inside of the house-boat. In this test a steam
pressure of 140 pounds was obtained, giving 650 R. P. M. of the round-end,
100-centimetre propellers, which previous tests had shown to mean a thrust
of 7480 grammes. As the flying weight of the aerodrome was now 14,104
grammes, the thrust obtained would correspond to a lift of 53 per cent of the
flying weight, which was maintained in this test for 90 seconds.
As the CG of Aerodrome No. 5 seemed to be a little too far forward in
the flight of July 28, it was decided to change it slightly, and it was moved
back 4 millimetres.
to remove the aerodrome from the launching apparatus to prevent its being
injured by side gusts. As it was Saturday and the wind showed no signs of
quieting down, the experiments were discontinued until the next week.
A UGUST 1— AERODROME NO. 5
After placing the aerodrome on the launching apparatus and getting
everything in readiness for a flight, upon lighting the burners a sudden sheet
of flame shot out of the smoke-stack and so seriously charred three panels
of each of the rear wings that they had to be removed for repairs. The silk
covering of the wings had been coated with a special fire-proofing
preparation, but the intensely hot flame, of course, charred all the silk that it
came in contact with.
By the time that the wings had been repaired, and the defect in the burner
which caused the accident had been remedied, a severe storm had arisen,
making it necessary to remove everything to the interior of the boat. While
waiting for the weather to become more suitable, a test of the engine of
Aerodrome No. 5 was made inside of the house-boat. In this test a steam
pressure of 140 pounds was obtained, giving 650 R. P. M. of the round-end,
100-centimetre propellers, which previous tests had shown to mean a thrust
of 7480 grammes. As the flying weight of the aerodrome was now 14,104
grammes, the thrust obtained would correspond to a lift of 53 per cent of the
flying weight, which was maintained in this test for 90 seconds.
As the CG of Aerodrome No. 5 seemed to be a little too far forward in
the flight of July 28, it was decided to change it slightly, and it was moved
back 4 millimetres.
Page 263
PL. 36. PATHS OF FLIGHT OF AERODROME NO. 5, JULY 29, 1899 ◊
A trial run in the house-boat was also made on Aerodrome No. 6, while
waiting for the weather to become more suitable, but, unfortunately, the
A trial run in the house-boat was also made on Aerodrome No. 6, while
waiting for the weather to become more suitable, but, unfortunately, the
Page 264
result of this test was disastrous. The aerodrome had been placed on trestles
and [p149] held down to the floor by wires fastened to the cross-frame. In the
midst of the test one of the wires slipped, allowing the aerodrome to push
forward and thus permitting the propellers to come in contact with the wires
which held it to the floor. Both propellers were entirely demolished and the
cross-frame was broken off short just at the right-hand engine. The disaster
was entirely due to the carelessness of one of the workmen in tightening
one of these wires, a further example of the extreme heedlessness of
workmen, even in the most important details, which concern the very
existence of the machine.
A UGUST 3— AERODROME NO. 5
After the very satisfactory trial of Aerodrome No. 5 in the shop two days
previous, it was hoped, now that the weather had become suitable, that a
good flight with the superposed wings would be obtained. The aerodrome,
equipped with these wings, was accordingly placed on the launching
apparatus and the burners were lighted, but they refused to work properly, a
steam pressure of only 80 pounds being obtained. After much delay the
burners were finally got to work properly, but the wind had increased in
velocity to such an extent that it was necessary to remove the aerodrome to
the interior of the house-boat. As the wind continued to increase in velocity
it was decided to make another trial of the aerodrome inside of the house-
boat. Upon doing this it was very soon found that there was a small leak in
the front turn of one of the coils of the boiler, and the steam from this
played directly against the burner, causing it to work intermittently. A new
coil was substituted, and after some adjustment a very excellent run was
obtained, the steam pressure reaching 130 pounds and the propellers
making 654 R. P. M.
In the afternoon the wind quieted down and the aerodrome, equipped
with superposed wings, was again placed on the launching apparatus. The
burners were lighted but again refused to work properly, the vaporizing tip
being stopped up with soot. This caused the burner to “flood,” which sent a
sheet of flame through the stack and burned the rear right wing.
and [p149] held down to the floor by wires fastened to the cross-frame. In the
midst of the test one of the wires slipped, allowing the aerodrome to push
forward and thus permitting the propellers to come in contact with the wires
which held it to the floor. Both propellers were entirely demolished and the
cross-frame was broken off short just at the right-hand engine. The disaster
was entirely due to the carelessness of one of the workmen in tightening
one of these wires, a further example of the extreme heedlessness of
workmen, even in the most important details, which concern the very
existence of the machine.
A UGUST 3— AERODROME NO. 5
After the very satisfactory trial of Aerodrome No. 5 in the shop two days
previous, it was hoped, now that the weather had become suitable, that a
good flight with the superposed wings would be obtained. The aerodrome,
equipped with these wings, was accordingly placed on the launching
apparatus and the burners were lighted, but they refused to work properly, a
steam pressure of only 80 pounds being obtained. After much delay the
burners were finally got to work properly, but the wind had increased in
velocity to such an extent that it was necessary to remove the aerodrome to
the interior of the house-boat. As the wind continued to increase in velocity
it was decided to make another trial of the aerodrome inside of the house-
boat. Upon doing this it was very soon found that there was a small leak in
the front turn of one of the coils of the boiler, and the steam from this
played directly against the burner, causing it to work intermittently. A new
coil was substituted, and after some adjustment a very excellent run was
obtained, the steam pressure reaching 130 pounds and the propellers
making 654 R. P. M.
In the afternoon the wind quieted down and the aerodrome, equipped
with superposed wings, was again placed on the launching apparatus. The
burners were lighted but again refused to work properly, the vaporizing tip
being stopped up with soot. This caused the burner to “flood,” which sent a
sheet of flame through the stack and burned the rear right wing.
Page 265
A new wing was substituted, the burner tip was cleaned out and
everything was again put in readiness for a flight. Upon lighting the
burners, 1 minute and 58 seconds were required to raise 120 pounds steam
pressure. The underneath launching apparatus, with the disappearing track,
worked perfectly, the aerodrome dropping slightly, but going straight ahead.
It, however, continued to descend for a distance of about 100 feet, the bow
being elevated about 5 degrees. The bow then became horizontal, the
aerodrome rising slightly at the same time, but going only about 50 feet
farther, when it again started to descend slightly, and finally settled gently
on the water between 300 and 500 feet from the house-boat, with its bow
elevated about 3 degrees. There was a hiss as the hull touched the water,
showing that the fire was still burning and making it [p150] improbable that
the failure of the flight was due to lack of power. The data on settings of
wings, tail, etc., are given on Data Sheet No. 11.
The speed of the launching car, one foot in front of the point at which the
aerodrome was released, was twenty feet a second, as shown by the carbon
record sheet carried by the launching car and moved in front of a tuning
fork which had been set in vibration.
The aerodrome, being uninjured in the previous flight, was again placed
on the “underneath” launching apparatus, and before attaching the wings a
short run was made in order to see that everything was in proper working
condition. As everything seemed to be all right, the wings and tail were
immediately adjusted for another trial. As the bow was slightly elevated in
the previous trial, it was thought best to bring the CG a little farther
forward, and this was accordingly done. As the aerodrome also seemed to
drop slightly in leaving the launching car in the above trial, the tension of
the launching springs was slightly increased so as to increase the velocity at
the moment of release.
Just as the sun was setting the aerodrome was again launched, 1 minute
and 30 seconds having been required to raise 120 pounds steam pressure,
but the pressure was rising very rapidly at the moment of launching. There
was an absolutely dead calm prevailing, the river being as smooth as glass.
The launching apparatus, with the disappearing track, worked perfectly.
everything was again put in readiness for a flight. Upon lighting the
burners, 1 minute and 58 seconds were required to raise 120 pounds steam
pressure. The underneath launching apparatus, with the disappearing track,
worked perfectly, the aerodrome dropping slightly, but going straight ahead.
It, however, continued to descend for a distance of about 100 feet, the bow
being elevated about 5 degrees. The bow then became horizontal, the
aerodrome rising slightly at the same time, but going only about 50 feet
farther, when it again started to descend slightly, and finally settled gently
on the water between 300 and 500 feet from the house-boat, with its bow
elevated about 3 degrees. There was a hiss as the hull touched the water,
showing that the fire was still burning and making it [p150] improbable that
the failure of the flight was due to lack of power. The data on settings of
wings, tail, etc., are given on Data Sheet No. 11.
The speed of the launching car, one foot in front of the point at which the
aerodrome was released, was twenty feet a second, as shown by the carbon
record sheet carried by the launching car and moved in front of a tuning
fork which had been set in vibration.
The aerodrome, being uninjured in the previous flight, was again placed
on the “underneath” launching apparatus, and before attaching the wings a
short run was made in order to see that everything was in proper working
condition. As everything seemed to be all right, the wings and tail were
immediately adjusted for another trial. As the bow was slightly elevated in
the previous trial, it was thought best to bring the CG a little farther
forward, and this was accordingly done. As the aerodrome also seemed to
drop slightly in leaving the launching car in the above trial, the tension of
the launching springs was slightly increased so as to increase the velocity at
the moment of release.
Just as the sun was setting the aerodrome was again launched, 1 minute
and 30 seconds having been required to raise 120 pounds steam pressure,
but the pressure was rising very rapidly at the moment of launching. There
was an absolutely dead calm prevailing, the river being as smooth as glass.
The launching apparatus, with the disappearing track, worked perfectly.
Page 266
Immediately upon being released the aerodrome went straight ahead, with
its midrod horizontal, but gradually glided downward as though the wings
had very little lifting power, and settled in the water about 200 feet from the
house-boat. The velocity of the launching car, 1 foot before the aerodrome
was released, was 22 feet a second, as shown by the carbon record sheet.
In the above trials of the superposed wings, the conditions of the wind
and of the aerodrome were certainly as favorable as could be expected.
There was as much power being furnished by the engine as had been
furnished in the previous flights with the “single-tier” wings, and the
balancing of the aerodrome was exceedingly good. The superposed wings,
unquestionably, had a fair trial and proved inferior to the “single-tier” ones,
for they had a supporting surface of 2.75 square feet to the pound, whereas
with the “single-tier” wings there was approximately 2 square feet to the
pound. The decreased lifting power of the superposed wings seems to be
another confirmation of the results of the Allegheny experiments with the
“plane-dropper.”40
As more time had already been given to these tests than it seemed well to
[p151] spend on them at that time, owing to the pressure of the work of
construction for the large machine, it was deemed best to discontinue them
for the time being, and as soon as time could be found for it, to construct a
set of wings with superposed surfaces, using only two surfaces and making
their distance apart at least equal to or greater than their width.
It will be remembered that the prime object in making these tests was to
obtain data for use in the balancing of the large aerodrome and in
constructing a launching apparatus for it. The chief deductions drawn from
them were: First: That it would be best to construct the first set of wings for
the large machine on the “single-tier” plan, and later to make a set of
superposed ones, should further experiments with new designs develop a
type of superposed surfaces which gave as good lifting power as the
“single-tier” ones. Second: That the proportioning of the coefficient of
elasticity of the Pénaud tail should be given as careful attention as the
setting of the wings. Third: That the “underneath” launching apparatus was
equally as good as the “overhead” one, and that both worked as well as
its midrod horizontal, but gradually glided downward as though the wings
had very little lifting power, and settled in the water about 200 feet from the
house-boat. The velocity of the launching car, 1 foot before the aerodrome
was released, was 22 feet a second, as shown by the carbon record sheet.
In the above trials of the superposed wings, the conditions of the wind
and of the aerodrome were certainly as favorable as could be expected.
There was as much power being furnished by the engine as had been
furnished in the previous flights with the “single-tier” wings, and the
balancing of the aerodrome was exceedingly good. The superposed wings,
unquestionably, had a fair trial and proved inferior to the “single-tier” ones,
for they had a supporting surface of 2.75 square feet to the pound, whereas
with the “single-tier” wings there was approximately 2 square feet to the
pound. The decreased lifting power of the superposed wings seems to be
another confirmation of the results of the Allegheny experiments with the
“plane-dropper.”40
As more time had already been given to these tests than it seemed well to
[p151] spend on them at that time, owing to the pressure of the work of
construction for the large machine, it was deemed best to discontinue them
for the time being, and as soon as time could be found for it, to construct a
set of wings with superposed surfaces, using only two surfaces and making
their distance apart at least equal to or greater than their width.
It will be remembered that the prime object in making these tests was to
obtain data for use in the balancing of the large aerodrome and in
constructing a launching apparatus for it. The chief deductions drawn from
them were: First: That it would be best to construct the first set of wings for
the large machine on the “single-tier” plan, and later to make a set of
superposed ones, should further experiments with new designs develop a
type of superposed surfaces which gave as good lifting power as the
“single-tier” ones. Second: That the proportioning of the coefficient of
elasticity of the Pénaud tail should be given as careful attention as the
setting of the wings. Third: That the “underneath” launching apparatus was
equally as good as the “overhead” one, and that both worked as well as
Page 267
could be desired; and, fourth, that while short periods of calm weather
might be expected during some part of the day on a portion of the days of
each month, yet the most favorable conditions were more apt to be met with
between the first break of day and the actual rising of the sun, or from an
hour preceding sunset until darkness actually came.
It will be noted that while considerable delay was experienced in making
these tests, nearly all of it was due to the very delicate adjustments required
in the power-generating apparatus of the aerodrome, but it should also be
noted that when these adjustments were accurately made the models
operated exceedingly well, and could be depended upon to give good flights
of sufficient duration to permit a careful study of their action while in the
air.
In the experiments of June 27 and July 7, above described, the aerodrome
immediately after leaving the launching apparatus began to rise with its
midrod pointed upward at an angle of about 15 degrees. From Data Sheet
No. 6, which gives in detail the important data as to the settings of the
wings, the elasticity of the Pénaud tail,41 etc., we note that the tail had a
negative angle of 7 12 degrees, and that the spring which held it at this angle
was of such a stiffness that it required 1240 grammes placed at its center of
figure to depress it to the horizontal. It will also be noticed that the position
of the front and rear [p152] wings relative to the center of gravity of the
machine was not the same as that which existed at the time of the very
successful flights of 1896, as shown by Data Sheet No. 1 of No. 5, May 6,
1896. When the elasticity of the tail was adjusted before making this test it
was thought that it was made the same as in the experiments of 1896,
though accurate data as to the exact amount of this elasticity had,
unfortunately, not been kept.
A slight change had also been made in the method employed of attaching
the Pénaud tail to the machine. In 1896 the tail was attached to the machine
by means of a flat piece of wood (hickory) which had been steamed and
bent to the proper extent to cause the rudder to have a negative angle of
about 5 degrees, but no accurate note was made of its angle or stiffness, so
might be expected during some part of the day on a portion of the days of
each month, yet the most favorable conditions were more apt to be met with
between the first break of day and the actual rising of the sun, or from an
hour preceding sunset until darkness actually came.
It will be noted that while considerable delay was experienced in making
these tests, nearly all of it was due to the very delicate adjustments required
in the power-generating apparatus of the aerodrome, but it should also be
noted that when these adjustments were accurately made the models
operated exceedingly well, and could be depended upon to give good flights
of sufficient duration to permit a careful study of their action while in the
air.
In the experiments of June 27 and July 7, above described, the aerodrome
immediately after leaving the launching apparatus began to rise with its
midrod pointed upward at an angle of about 15 degrees. From Data Sheet
No. 6, which gives in detail the important data as to the settings of the
wings, the elasticity of the Pénaud tail,41 etc., we note that the tail had a
negative angle of 7 12 degrees, and that the spring which held it at this angle
was of such a stiffness that it required 1240 grammes placed at its center of
figure to depress it to the horizontal. It will also be noticed that the position
of the front and rear [p152] wings relative to the center of gravity of the
machine was not the same as that which existed at the time of the very
successful flights of 1896, as shown by Data Sheet No. 1 of No. 5, May 6,
1896. When the elasticity of the tail was adjusted before making this test it
was thought that it was made the same as in the experiments of 1896,
though accurate data as to the exact amount of this elasticity had,
unfortunately, not been kept.
A slight change had also been made in the method employed of attaching
the Pénaud tail to the machine. In 1896 the tail was attached to the machine
by means of a flat piece of wood (hickory) which had been steamed and
bent to the proper extent to cause the rudder to have a negative angle of
about 5 degrees, but no accurate note was made of its angle or stiffness, so
Page 268
that in 1899 no data were available as to exactly what the angle had been or
how stiff the spring was. Owing to the fact that wood not only warps and
twists, but also that any piece which has been steamed and bent gradually
loses a certain amount of its curvature, it was decided in 1898 to change this
method of attaching the tail, the wooden spring being replaced by a coiled
steel spring attached to an upper guy-post and connected to the tail by a
bridle wire fastened to the center of figure of the tail.
After the experiment of July 7, 1899, a lower spring, consisting of small
rubber bands, was connected by a wire to the lower part of the rudder and
fastened to the guy-post, thereby more nearly reproducing the conditions
obtained when using a wooden spring, which, of course, tends to return the
rudder to its normal position when it is displaced in either direction. After
attaching this lower spring to the rudder, the experiment of July 14 was
made, and it was found that the aerodrome still flew with its midrod pointed
upward at a very steep angle. It was, therefore, felt certain that the upper
spring on the rudder was too stiff, and that it should not require so much as
1240 grammes to bring it to the horizontal. This spring was, therefore,
replaced by a weaker one, and the angle of the rudder was also decreased
until it had a negative angle of only 5 degrees and required only 200
grammes placed at its center of figure to bring it to the horizontal. From the
description of the flight of July 19, it will be seen that these changes
immediately corrected the tendency of the aerodrome to point its nose
upward at such a sharp angle, and it will be later seen that after a further
slight adjustment the flight of July 29 was made, in which the proper
balancing was obtained and the aerodrome made a good horizontal flight.
After these preliminary tests with the “overhead” launching apparatus, it
was dismounted and the “underneath” one substituted and the experiments
of July 28, 29 and August 3 were made. Everything connected with this
“underneath” launching apparatus worked perfectly from the start and four
flights of the aerodromes were made using it.
how stiff the spring was. Owing to the fact that wood not only warps and
twists, but also that any piece which has been steamed and bent gradually
loses a certain amount of its curvature, it was decided in 1898 to change this
method of attaching the tail, the wooden spring being replaced by a coiled
steel spring attached to an upper guy-post and connected to the tail by a
bridle wire fastened to the center of figure of the tail.
After the experiment of July 7, 1899, a lower spring, consisting of small
rubber bands, was connected by a wire to the lower part of the rudder and
fastened to the guy-post, thereby more nearly reproducing the conditions
obtained when using a wooden spring, which, of course, tends to return the
rudder to its normal position when it is displaced in either direction. After
attaching this lower spring to the rudder, the experiment of July 14 was
made, and it was found that the aerodrome still flew with its midrod pointed
upward at a very steep angle. It was, therefore, felt certain that the upper
spring on the rudder was too stiff, and that it should not require so much as
1240 grammes to bring it to the horizontal. This spring was, therefore,
replaced by a weaker one, and the angle of the rudder was also decreased
until it had a negative angle of only 5 degrees and required only 200
grammes placed at its center of figure to bring it to the horizontal. From the
description of the flight of July 19, it will be seen that these changes
immediately corrected the tendency of the aerodrome to point its nose
upward at such a sharp angle, and it will be later seen that after a further
slight adjustment the flight of July 29 was made, in which the proper
balancing was obtained and the aerodrome made a good horizontal flight.
After these preliminary tests with the “overhead” launching apparatus, it
was dismounted and the “underneath” one substituted and the experiments
of July 28, 29 and August 3 were made. Everything connected with this
“underneath” launching apparatus worked perfectly from the start and four
flights of the aerodromes were made using it.
Page 269
PL. 37. EXPERIMENTAL FORMS OF SUPERPOSED SURFACES, 1898, 1899 (SEE
ALSO PLATES 64 AND 65) ◊
ALSO PLATES 64 AND 65) ◊
Page 270
[p153]
It will be recalled that in “Experiments in Aerodynamics” Mr. Langley
made tests of the soaring speed, etc., of surfaces when superposed. In many
of his experiments with rubber-driven models, he also employed superposed
surfaces. During the summer of 1898 several forms of superposed surfaces,
of a proper size for use on the steam-driven models Nos. 5 and 6, were
constructed and were tested under as nearly as possible the same conditions
as would exist when used on the aerodrome, by mounting the surfaces on
the whirling-table and measuring their soaring speed, lift, drift, etc., to
determine just what arrangement of surfaces gave the greatest lifting effect
with the least resistance. Two of the forms which were tested are shown in
Plate 37, Figs. 1 and 2, and Plates 64 and 65. At the conclusion of these
tests, it was decided to construct a set of surfaces on the plan shown in
Plates 64 and 65, and to have them ready for use on either of the models
Nos. 5 and 6. These surfaces were taken to Chopawamsic Island in April,
1899, when all of the other aerodromic material was first carried there. It
was planned to make some tests with them to determine whether or not it
would be best to use superposed surfaces on the large aerodrome or to
follow the plan of “single-tier” ones, which had the great advantage of
having already proved their worth in the successful flights of the models.
On August 3, Aerodrome No. 5, equipped with these superposed surfaces,
was launched. It will be noted from Data Sheet No. 11 that the superficial
area of the superposed surfaces was considerably greater than that provided
by the “single-tier” ones, and on the assumption of the same efficiency per
unit of surface in both cases, the aerodrome should have soared at a less
speed and required less power when using the superposed surfaces. The
results obtained, however, were just the reverse, the aerodrome being
unable to sustain itself when using the superposed surfaces, whereas with
the “single-tier” ones it was evident that a slight excess weight might easily
have been carried without preventing the aerodrome from soaring properly.
While it was felt that these tests were not entirely conclusive as to the
superior lifting power of the “single-tier” surfaces, yet as the engine builder
was constantly promising, each time with increased emphasis, that he
It will be recalled that in “Experiments in Aerodynamics” Mr. Langley
made tests of the soaring speed, etc., of surfaces when superposed. In many
of his experiments with rubber-driven models, he also employed superposed
surfaces. During the summer of 1898 several forms of superposed surfaces,
of a proper size for use on the steam-driven models Nos. 5 and 6, were
constructed and were tested under as nearly as possible the same conditions
as would exist when used on the aerodrome, by mounting the surfaces on
the whirling-table and measuring their soaring speed, lift, drift, etc., to
determine just what arrangement of surfaces gave the greatest lifting effect
with the least resistance. Two of the forms which were tested are shown in
Plate 37, Figs. 1 and 2, and Plates 64 and 65. At the conclusion of these
tests, it was decided to construct a set of surfaces on the plan shown in
Plates 64 and 65, and to have them ready for use on either of the models
Nos. 5 and 6. These surfaces were taken to Chopawamsic Island in April,
1899, when all of the other aerodromic material was first carried there. It
was planned to make some tests with them to determine whether or not it
would be best to use superposed surfaces on the large aerodrome or to
follow the plan of “single-tier” ones, which had the great advantage of
having already proved their worth in the successful flights of the models.
On August 3, Aerodrome No. 5, equipped with these superposed surfaces,
was launched. It will be noted from Data Sheet No. 11 that the superficial
area of the superposed surfaces was considerably greater than that provided
by the “single-tier” ones, and on the assumption of the same efficiency per
unit of surface in both cases, the aerodrome should have soared at a less
speed and required less power when using the superposed surfaces. The
results obtained, however, were just the reverse, the aerodrome being
unable to sustain itself when using the superposed surfaces, whereas with
the “single-tier” ones it was evident that a slight excess weight might easily
have been carried without preventing the aerodrome from soaring properly.
While it was felt that these tests were not entirely conclusive as to the
superior lifting power of the “single-tier” surfaces, yet as the engine builder
was constantly promising, each time with increased emphasis, that he
Page 271
would within less than a fortnight deliver the engine for the large
aerodrome, and that it would develop even more power than the
specifications called for, it was deemed best to cease the experiments with
the models and concentrate all effort on the completion of the large
aerodrome frame and the construction of a set of “single-tier” supporting
surfaces for it. It was recognized from the first that the “single-tier”
supporting surfaces lacked the rigidity which could be secured by the truss
construction afforded by the superposed plan, yet these models, which were
the only machines in the history of the world that had ever flown
successfully, had been equipped with “single-tier” surfaces; and the
experience so dearly bought during the long [p154] years of development of
these models had taught the very valuable lesson that in work of this kind
where we have no margin on anything, but everything has to be calculated
on the “knife-edge” basis, it is an exceedingly unwise thing to introduce any
modification from what has been proved to be satisfactory, unless such
modification is absolutely necessary.
The principal object in building the one-eighth size model of the large
aerodrome, as mentioned in the first part of this chapter, was to determine
by actual experiment whether the new form of “underneath” launching
apparatus, which had just been designed, was likely to prove as satisfactory
as the original “overhead” type, which had been used in the successful
flights of the models in 1896. Yet after it was completed this aerodrome was
found so very strong and stiff, even though roughly constructed by merely
tying the joints of the tubing together with wires and soldering over the
joints, that it was decided to equip it with power, if a suitable form of power
could be found which could be easily applied. Just at this time liquid air as
a motive power was attracting considerable attention all over the country,
and attempts were made to procure a small power plant for operation by
liquid air. After devoting considerable time to the matter it was found
impossible to do anything with it just at that time, as the liquified air could
not be obtained in Washington, and one of the chief experimenters in New
York, who had been given a commission to make certain experiments at his
aerodrome, and that it would develop even more power than the
specifications called for, it was deemed best to cease the experiments with
the models and concentrate all effort on the completion of the large
aerodrome frame and the construction of a set of “single-tier” supporting
surfaces for it. It was recognized from the first that the “single-tier”
supporting surfaces lacked the rigidity which could be secured by the truss
construction afforded by the superposed plan, yet these models, which were
the only machines in the history of the world that had ever flown
successfully, had been equipped with “single-tier” surfaces; and the
experience so dearly bought during the long [p154] years of development of
these models had taught the very valuable lesson that in work of this kind
where we have no margin on anything, but everything has to be calculated
on the “knife-edge” basis, it is an exceedingly unwise thing to introduce any
modification from what has been proved to be satisfactory, unless such
modification is absolutely necessary.
The principal object in building the one-eighth size model of the large
aerodrome, as mentioned in the first part of this chapter, was to determine
by actual experiment whether the new form of “underneath” launching
apparatus, which had just been designed, was likely to prove as satisfactory
as the original “overhead” type, which had been used in the successful
flights of the models in 1896. Yet after it was completed this aerodrome was
found so very strong and stiff, even though roughly constructed by merely
tying the joints of the tubing together with wires and soldering over the
joints, that it was decided to equip it with power, if a suitable form of power
could be found which could be easily applied. Just at this time liquid air as
a motive power was attracting considerable attention all over the country,
and attempts were made to procure a small power plant for operation by
liquid air. After devoting considerable time to the matter it was found
impossible to do anything with it just at that time, as the liquified air could
not be obtained in Washington, and one of the chief experimenters in New
York, who had been given a commission to make certain experiments at his
Page 272
plant, so continuously delayed beginning them that it was found necessary
to give up the idea.
However, after the completion of the tests of the launching apparatus
some experiments were made in flying the model as a kite. For this purpose
a mast twenty feet high was constructed and so arranged that it could be
mounted at the center of a small power launch. The model aerodrome was
flown by a cord connected to it by a bridle, the cord passing over a swivel
pulley on top of the mast and down into the boat, whence it could be played
out or hauled in as occasion required. By heading the launch into the wind it
was possible to secure sufficient relative velocity to cause the model to
support itself and a number of tests were made in this way. It was found that
when the bridle was attached at the point at which the propellers would
deliver their thrust, had they been in use and driven by power, the model
flew exceedingly well, maintaining its equilibrium even during very strong
gusts. Owing to the rolling produced by waves from the large boats which
were continually passing in the part of the river where these tests were
made, the power launch was often in danger of being upset by its tall mast;
and finally, when the tests were just reaching the point where accurate
information was being obtained on the balancing of the model, a sudden
rolling of the boat caused the mast to snap off while the model was in the
air. Before it could be picked up from the water a passing boat had
swamped it and it was lost in the river. [p155]
Although the model was, as has been said, rudely constructed and,
therefore, did not represent a serious loss, yet the pressure of the more
important construction work for the large machine prohibited the
construction of another rough model for continuing these kite experiments,
which it was felt could not at best be more than approximate indications of
the general stability of the machine under practical conditions.
to give up the idea.
However, after the completion of the tests of the launching apparatus
some experiments were made in flying the model as a kite. For this purpose
a mast twenty feet high was constructed and so arranged that it could be
mounted at the center of a small power launch. The model aerodrome was
flown by a cord connected to it by a bridle, the cord passing over a swivel
pulley on top of the mast and down into the boat, whence it could be played
out or hauled in as occasion required. By heading the launch into the wind it
was possible to secure sufficient relative velocity to cause the model to
support itself and a number of tests were made in this way. It was found that
when the bridle was attached at the point at which the propellers would
deliver their thrust, had they been in use and driven by power, the model
flew exceedingly well, maintaining its equilibrium even during very strong
gusts. Owing to the rolling produced by waves from the large boats which
were continually passing in the part of the river where these tests were
made, the power launch was often in danger of being upset by its tall mast;
and finally, when the tests were just reaching the point where accurate
information was being obtained on the balancing of the model, a sudden
rolling of the boat caused the mast to snap off while the model was in the
air. Before it could be picked up from the water a passing boat had
swamped it and it was lost in the river. [p155]
Although the model was, as has been said, rudely constructed and,
therefore, did not represent a serious loss, yet the pressure of the more
important construction work for the large machine prohibited the
construction of another rough model for continuing these kite experiments,
which it was felt could not at best be more than approximate indications of
the general stability of the machine under practical conditions.
Page 273
[p156] ◊
CHAPTER IV
HOUSE-BOAT AND LAUNCHING APPARATUS
The use of a house-boat seemed to Mr. Langley so indispensable in
former years in making open-air tests of the models that he decided from
the outset, though advised by the writer against doing so, to use the same
plan on a much larger scale in connection with the large aerodrome. Aside
from its supposed utility as a convenient and apparently safe place from
which to launch the aerodrome, the house-boat was valuable as a portable
workshop for making necessary repairs and as a temporary storehouse for
the apparatus, thereby saving much packing and unpacking. It also provided
sleeping quarters for the workmen.
It was early seen that this plan would require a boat at least 60 by 40 feet,
which could be built only at a large initial cost. But as the experience with
models had so firmly convinced Mr. Langley that it was necessary not only
that the aerodrome be launched over the water, but also at a considerable
height above it, and from a station that commanded all points of the
compass, he decided to adopt this plan for the large aerodrome, and designs
for such a boat were accordingly made in the latter part of 1898.
In order to insure the completion of this house-boat by the time the
aerodrome was expected to be ready for trial, it was built under contract.
Immediately after its delivery in May, 1899, work was begun on the
superstructure which carried the launching track. This superstructure was a
considerable undertaking, involving a turn-table weighing about 15 tons,
supported on a double circular track, and this track in turn was supported
entirely from the side walls of the house to avoid having columns in the
middle of the floor. From the photographs, Plate 38, Figs. 1, 2 and 3, it will
be seen that the entire superstructure was supported by three trussed girders
extending across the boat above the roof and carried by vertical posts built
into the side walls of the house. The turn-table was 48 feet square and the
launching track carried by it was 5 feet gauge by 80 feet long.
CHAPTER IV
HOUSE-BOAT AND LAUNCHING APPARATUS
The use of a house-boat seemed to Mr. Langley so indispensable in
former years in making open-air tests of the models that he decided from
the outset, though advised by the writer against doing so, to use the same
plan on a much larger scale in connection with the large aerodrome. Aside
from its supposed utility as a convenient and apparently safe place from
which to launch the aerodrome, the house-boat was valuable as a portable
workshop for making necessary repairs and as a temporary storehouse for
the apparatus, thereby saving much packing and unpacking. It also provided
sleeping quarters for the workmen.
It was early seen that this plan would require a boat at least 60 by 40 feet,
which could be built only at a large initial cost. But as the experience with
models had so firmly convinced Mr. Langley that it was necessary not only
that the aerodrome be launched over the water, but also at a considerable
height above it, and from a station that commanded all points of the
compass, he decided to adopt this plan for the large aerodrome, and designs
for such a boat were accordingly made in the latter part of 1898.
In order to insure the completion of this house-boat by the time the
aerodrome was expected to be ready for trial, it was built under contract.
Immediately after its delivery in May, 1899, work was begun on the
superstructure which carried the launching track. This superstructure was a
considerable undertaking, involving a turn-table weighing about 15 tons,
supported on a double circular track, and this track in turn was supported
entirely from the side walls of the house to avoid having columns in the
middle of the floor. From the photographs, Plate 38, Figs. 1, 2 and 3, it will
be seen that the entire superstructure was supported by three trussed girders
extending across the boat above the roof and carried by vertical posts built
into the side walls of the house. The turn-table was 48 feet square and the
launching track carried by it was 5 feet gauge by 80 feet long.
Page 274
F IG. 1. F IG. 2. F IG. 3.
PL. 38. HOUSE-BOAT AND LAUNCHING APPARATUS, 1899
◊
PL. 38. HOUSE-BOAT AND LAUNCHING APPARATUS, 1899
◊
Page 275
In making tests of the models, it had been the practice to carry the main
body of the aerodrome up a ladder to the upper works of the boat, the wings
being also carried up in the same manner. As the large aerodrome was
expected to weigh at least 640 pounds, of which 350 pounds would be the
steel frame with its undetachable parts, such as the engine and its
appurtenances, it was seen that something more effective than a ladder
would need to be provided for getting the aerodrome from the interior of the
boat to the launching track [p157] above. It was therefore decided to place
the upper works of the boat rather nearer the rear end than the front, thus
leaving a space over the front end of the house through which a large trap-
door might be cut in the roof, and it was thought that in this way the
aerodrome might be passed up to the launching track by the use of suitable
ropes and pulleys. The upper works were so arranged, and a sliding trap-
door was provided in the roof, but more intimate knowledge of the
difficulties of handling so large and heavy a frame made it certain, even
before the aerodrome was ever placed upon the house-boat, that it would be
impossible to transport it to the upper works by passing it through the trap-
door. A different plan was then resorted to. A very large door was
constructed at the rear end of the house, through which the completely
assembled frame could be carried in a level position and placed upon a
large raft, consisting of a lattice flooring over pontoons, moored at the rear
end of the boat, as clearly seen in Plate 38. In order to raise the aerodrome
frame from the raft to the upper works, a large, but light, mast and boom,
with suitable stays were provided. As the wings, when mounted in their
proper position on the aerodrome, would be interfered with by such a mast,
the mast and boom were so devised as to be capable of rapid erection and
dismounting, only five minutes being necessary for either operation. In
Plate 38 the mast and boom are seen in position in Fig. 3, while in Figs. 1
and 2 they have been dismounted.
The construction of the launching track and car was begun in November,
1899, but their completion was long delayed, as they were frequently put
aside for the more immediately important parts of the work. Moreover, the
arrangement of the struts and clutch of the launching car depended entirely
body of the aerodrome up a ladder to the upper works of the boat, the wings
being also carried up in the same manner. As the large aerodrome was
expected to weigh at least 640 pounds, of which 350 pounds would be the
steel frame with its undetachable parts, such as the engine and its
appurtenances, it was seen that something more effective than a ladder
would need to be provided for getting the aerodrome from the interior of the
boat to the launching track [p157] above. It was therefore decided to place
the upper works of the boat rather nearer the rear end than the front, thus
leaving a space over the front end of the house through which a large trap-
door might be cut in the roof, and it was thought that in this way the
aerodrome might be passed up to the launching track by the use of suitable
ropes and pulleys. The upper works were so arranged, and a sliding trap-
door was provided in the roof, but more intimate knowledge of the
difficulties of handling so large and heavy a frame made it certain, even
before the aerodrome was ever placed upon the house-boat, that it would be
impossible to transport it to the upper works by passing it through the trap-
door. A different plan was then resorted to. A very large door was
constructed at the rear end of the house, through which the completely
assembled frame could be carried in a level position and placed upon a
large raft, consisting of a lattice flooring over pontoons, moored at the rear
end of the boat, as clearly seen in Plate 38. In order to raise the aerodrome
frame from the raft to the upper works, a large, but light, mast and boom,
with suitable stays were provided. As the wings, when mounted in their
proper position on the aerodrome, would be interfered with by such a mast,
the mast and boom were so devised as to be capable of rapid erection and
dismounting, only five minutes being necessary for either operation. In
Plate 38 the mast and boom are seen in position in Fig. 3, while in Figs. 1
and 2 they have been dismounted.
The construction of the launching track and car was begun in November,
1899, but their completion was long delayed, as they were frequently put
aside for the more immediately important parts of the work. Moreover, the
arrangement of the struts and clutch of the launching car depended entirely
Page 276
on the form and dimensions of the frame of the aerodrome, which could not
be entirely decided until a proper engine had been secured and tested in the
frame to determine what modifications of it were necessary. In the spring of
1902, however, the launching car was entirely finished and a number of
tests of the large engine were made in the shop with the frame mounted in
position on the car.
From the description of the “overhead” launching apparatus (Part I,
Chapter X ◊) which had proved so successful in the tests of the models,
both in 1896 and in the later experiments of 1899, it will be recalled that the
essential features of it were a track and a light car with three hinged struts
which extended below the body of the car, and against which suitable co-
acting bearing points attached to the frame of the aerodrome were tightly
drawn by means of a clutch which gripped a special fitting fastened to the
aerodrome frame near the central point of its length. After the engine of the
aerodrome had been started and got to running at full speed, the car was
released and moved forward along its track by the combined force of the
thrust of the propellers and the pull of the coiled launching springs. Just
before the car reached the forward end of the track, a cam at this point
caused the clutch to open and release [p158] the aerodrome, which
immediately dropped slightly, as it had purposely not quite reached a speed
sufficient to cause it to soar. This slight drop of the aerodrome, even if it
were only a fraction of an inch, made it possible for the hinged struts,
against which it had been held by the clutch, to be folded up by their special
springs against the floor of the car, thus leaving the aerodrome free in the
air without danger of entanglement.
The struts referred to above were three in number, two being placed near
the rear and one at the center of the front of the car. The use of three points
of support had the advantage of furnishing a rather rigid foundation against
which the frame could be tightly drawn by means of the clutch-hook
without risk of straining it. In designing the “underneath” launching
apparatus, which was very thoroughly tested in the experiments with the
models in the summer of 1899, the plan of having three struts with the
be entirely decided until a proper engine had been secured and tested in the
frame to determine what modifications of it were necessary. In the spring of
1902, however, the launching car was entirely finished and a number of
tests of the large engine were made in the shop with the frame mounted in
position on the car.
From the description of the “overhead” launching apparatus (Part I,
Chapter X ◊) which had proved so successful in the tests of the models,
both in 1896 and in the later experiments of 1899, it will be recalled that the
essential features of it were a track and a light car with three hinged struts
which extended below the body of the car, and against which suitable co-
acting bearing points attached to the frame of the aerodrome were tightly
drawn by means of a clutch which gripped a special fitting fastened to the
aerodrome frame near the central point of its length. After the engine of the
aerodrome had been started and got to running at full speed, the car was
released and moved forward along its track by the combined force of the
thrust of the propellers and the pull of the coiled launching springs. Just
before the car reached the forward end of the track, a cam at this point
caused the clutch to open and release [p158] the aerodrome, which
immediately dropped slightly, as it had purposely not quite reached a speed
sufficient to cause it to soar. This slight drop of the aerodrome, even if it
were only a fraction of an inch, made it possible for the hinged struts,
against which it had been held by the clutch, to be folded up by their special
springs against the floor of the car, thus leaving the aerodrome free in the
air without danger of entanglement.
The struts referred to above were three in number, two being placed near
the rear and one at the center of the front of the car. The use of three points
of support had the advantage of furnishing a rather rigid foundation against
which the frame could be tightly drawn by means of the clutch-hook
without risk of straining it. In designing the “underneath” launching
apparatus, which was very thoroughly tested in the experiments with the
models in the summer of 1899, the plan of having three struts with the
Page 277
aerodrome drawn tightly against them by means of a central clutch-hook
was continued with most satisfactory results.
When the position of the struts on this launching apparatus had been
changed so as to permit it to be used for the quarter-size model, it was
found, in making shop tests of the engine with the aerodrome mounted on
the launching car, that, owing to the greater vibration produced by the
gasoline engine, the three points of suspension did not hold the model in a
sufficiently rigid manner. It became necessary, therefore, to use four struts,
the two rear ones being left as before, and the single one in front being
replaced by two interconnected ones arranged similarly to those in the rear.
After making this change no difficulty was found in holding the aerodrome
rigidly against the struts, and this modification was therefore immediately
introduced in the designs for the large launching car which was already
under construction.
was continued with most satisfactory results.
When the position of the struts on this launching apparatus had been
changed so as to permit it to be used for the quarter-size model, it was
found, in making shop tests of the engine with the aerodrome mounted on
the launching car, that, owing to the greater vibration produced by the
gasoline engine, the three points of suspension did not hold the model in a
sufficiently rigid manner. It became necessary, therefore, to use four struts,
the two rear ones being left as before, and the single one in front being
replaced by two interconnected ones arranged similarly to those in the rear.
After making this change no difficulty was found in holding the aerodrome
rigidly against the struts, and this modification was therefore immediately
introduced in the designs for the large launching car which was already
under construction.
Page 278
PL. 39. METHOD OF ATTACHING GUY-WIRES TO GUY-POSTS TO RELIEVE
TORSIONAL STRAIN ◊
TORSIONAL STRAIN ◊
Page 279
Experience, both with models 5 and 6, and with the quarter-size model,
had also demonstrated the necessity of providing some means whereby the
aerodrome frame would be relieved of the torsional strains produced upon it
by a side wind striking the under surface of the wings when the aerodrome
was mounted on the car preparatory to a test. The means for preventing
these torsional strains in the case of the models, when “overhead” type of
launching car was used, has been described in Chapter X of Part I ◊.
However, with the “underneath” type of launching car, a different means
was necessary. A plan, in which outriggers projected from the body of the
car and wires running from these outriggers up to the main ribs of the
wings, with means for releasing the wires just before the car reached the
end of the track, was used with the “underneath” car in the tests of models 5
and 6 in the summer of 1899, but the outriggers were frequently deranged
by the sudden stopping of the car at the end of the run and they were
replaced by a simpler arrangement. In this plan the torsional strains were
relieved by providing, at the forward and rear ends [p159] of the car, smaller
hinged uprights furnished in their upper part with a small slot into which a
pin projected from the bottom of the forward and rear guy-posts,
respectively. The guy-wires from wings being connected to the lower ends
of the guy-posts the torsional strain produced by a side wind was
immediately transmitted from the wings through the guy-wires to the guy-
post, whence it was transmitted to the car itself, and thus prevented from
acting on the metal frame of the aerodrome, as shown in Plate 39. These
additional short struts for taking up the torsional strain were first added to
the small launching car in 1901, and in the succeeding tests made with the
quarter-size model no trouble of any kind was indicated as likely to be
caused by them. As it was these extra struts which were directly responsible
for the accident in the launching of the large aerodrome October 7, 1903, at
the time of its first trial, and possibly also for that on December 8, 1903, at
the time of the second trial, special attention is here called to them.
The length of travel which could be provided for the launching car in the
case of the large aerodrome, as well as in that of the models was necessarily
very limited, owing to the fact that the track had to be constructed on the
had also demonstrated the necessity of providing some means whereby the
aerodrome frame would be relieved of the torsional strains produced upon it
by a side wind striking the under surface of the wings when the aerodrome
was mounted on the car preparatory to a test. The means for preventing
these torsional strains in the case of the models, when “overhead” type of
launching car was used, has been described in Chapter X of Part I ◊.
However, with the “underneath” type of launching car, a different means
was necessary. A plan, in which outriggers projected from the body of the
car and wires running from these outriggers up to the main ribs of the
wings, with means for releasing the wires just before the car reached the
end of the track, was used with the “underneath” car in the tests of models 5
and 6 in the summer of 1899, but the outriggers were frequently deranged
by the sudden stopping of the car at the end of the run and they were
replaced by a simpler arrangement. In this plan the torsional strains were
relieved by providing, at the forward and rear ends [p159] of the car, smaller
hinged uprights furnished in their upper part with a small slot into which a
pin projected from the bottom of the forward and rear guy-posts,
respectively. The guy-wires from wings being connected to the lower ends
of the guy-posts the torsional strain produced by a side wind was
immediately transmitted from the wings through the guy-wires to the guy-
post, whence it was transmitted to the car itself, and thus prevented from
acting on the metal frame of the aerodrome, as shown in Plate 39. These
additional short struts for taking up the torsional strain were first added to
the small launching car in 1901, and in the succeeding tests made with the
quarter-size model no trouble of any kind was indicated as likely to be
caused by them. As it was these extra struts which were directly responsible
for the accident in the launching of the large aerodrome October 7, 1903, at
the time of its first trial, and possibly also for that on December 8, 1903, at
the time of the second trial, special attention is here called to them.
The length of travel which could be provided for the launching car in the
case of the large aerodrome, as well as in that of the models was necessarily
very limited, owing to the fact that the track had to be constructed on the
Page 280
top of the house of the boat. It was therefore necessary, in order that the
aerodrome might attain a speed sufficient for soaring before being
launched, to keep the weight of the launching car as small as possible, a
given spring tension being capable of accelerating a given mass a definite
amount in a given length of travel. With a heavier launching car the spring
tension would have to be increased. Moreover, since the blow which would
be struck when the car was suddenly stopped at the end of the track, would
depend on its mass as well as its velocity, there was an additional reason for
trying to keep the weight of the car as small as possible.
While it was found perfectly feasible to keep the weight of the launching
car for the model low enough for practical purposes, in designing the
launching car for the large aerodrome it was only by eliminating all flooring
of the car and providing merely a box frame with necessary cross-braces,
that its weight was kept within what appeared reasonable limits. Even then
the blow which it would strike when it reached the end of the track was
found by calculation to be exceedingly formidable.
Referring to the drawings of Plate 40, Figs. 1, 2 and 3, it will be seen that
the large launching car consisted essentially of two parallel longitudinal
side members 6 inches deep by 1.5 inches thick by 19 feet long, connected
by three main sets of cross-members: one set near the rear, at the point at
which the rear struts for supporting the aerodrome were mounted; a second
rather heavier set about the middle of its length, at the point where the strut
which carried the clutch-hook was mounted; and a third near the front, at
the point where the front struts were mounted. Projecting from the forward
end of each of the [p160] longitudinal side members were piston rods, on
which were mounted leather-cup pistons, which co-acted with buffer
cylinders fixed at the extreme front of the track to absorb the blow when the
car reached them at the end of its travel. The car was supported on each side
by means of four hangers (Figs. 4 and 5) which carried grooved wheels
having ball-bearings and running on a steel track consisting of flat plates
fastened on the side of the timbers of the launching track. On the extreme
lower point of these hangers were small guide pulleys, so placed as to be
just below and out of contact with a guard rail on the side of the launching
aerodrome might attain a speed sufficient for soaring before being
launched, to keep the weight of the launching car as small as possible, a
given spring tension being capable of accelerating a given mass a definite
amount in a given length of travel. With a heavier launching car the spring
tension would have to be increased. Moreover, since the blow which would
be struck when the car was suddenly stopped at the end of the track, would
depend on its mass as well as its velocity, there was an additional reason for
trying to keep the weight of the car as small as possible.
While it was found perfectly feasible to keep the weight of the launching
car for the model low enough for practical purposes, in designing the
launching car for the large aerodrome it was only by eliminating all flooring
of the car and providing merely a box frame with necessary cross-braces,
that its weight was kept within what appeared reasonable limits. Even then
the blow which it would strike when it reached the end of the track was
found by calculation to be exceedingly formidable.
Referring to the drawings of Plate 40, Figs. 1, 2 and 3, it will be seen that
the large launching car consisted essentially of two parallel longitudinal
side members 6 inches deep by 1.5 inches thick by 19 feet long, connected
by three main sets of cross-members: one set near the rear, at the point at
which the rear struts for supporting the aerodrome were mounted; a second
rather heavier set about the middle of its length, at the point where the strut
which carried the clutch-hook was mounted; and a third near the front, at
the point where the front struts were mounted. Projecting from the forward
end of each of the [p160] longitudinal side members were piston rods, on
which were mounted leather-cup pistons, which co-acted with buffer
cylinders fixed at the extreme front of the track to absorb the blow when the
car reached them at the end of its travel. The car was supported on each side
by means of four hangers (Figs. 4 and 5) which carried grooved wheels
having ball-bearings and running on a steel track consisting of flat plates
fastened on the side of the timbers of the launching track. On the extreme
lower point of these hangers were small guide pulleys, so placed as to be
just below and out of contact with a guard rail on the side of the launching
Page 281
track, thus preventing any possibility of the launching car being raised from
the track either during its forward motion or by a side wind striking
underneath the wings.
the track either during its forward motion or by a side wind striking
underneath the wings.
Page 282
Aerodrome “A.” (Details 13 Full Size )
PL. 40. GENERAL PLAN AND DETAILS OF LAUNCHING-CAR ◊ lgr
PL. 40. GENERAL PLAN AND DETAILS OF LAUNCHING-CAR ◊ lgr
Page 283
F IG. 1. F IG. 2. F IG. 3.
PL. 41. AERODROME ON LAUNCHING-CAR
◊
PL. 41. AERODROME ON LAUNCHING-CAR
◊
Page 284
PL. 42. DETAILS OF CLUTCH POST FOR LAUNCHING-CAR ◊ lgr
Page 285
PL. 43. FRONT END OF TRACK JUST PREPARATORY TO LAUNCHING
AERODROME ◊
On the large launching car the arrangement of the struts against which the
bearing points of the frame were tightly drawn by the clutch was similar in
all respects to that used on the model car, there being only slight differences
in details. The details of the uprights on which the bearing points of the
aerodrome frame rested are clearly shown in Figs. 6, 7, 8, and 9 of Plate 40.
From the photographs (Plate 41, Figs. 1, 2, and 3) which show the large
frame mounted on the launching car, the general arrangement of the struts
and the clutch-hook can be readily seen; and from Plate 42, Figs. 1, 2, and
3, which show in detail most of the important features of the clutch-post
and its clutch, a very good idea of the size of the different parts may be had
by observing that the distance from the fulcrum of each half of the hook to
the pin by which it was connected through the universal joint to the vertical
rods is five inches. As previously stated, this clutch-hook gripped the lower
pyramid and pulled the bearing points of the frame firmly against the
AERODROME ◊
On the large launching car the arrangement of the struts against which the
bearing points of the frame were tightly drawn by the clutch was similar in
all respects to that used on the model car, there being only slight differences
in details. The details of the uprights on which the bearing points of the
aerodrome frame rested are clearly shown in Figs. 6, 7, 8, and 9 of Plate 40.
From the photographs (Plate 41, Figs. 1, 2, and 3) which show the large
frame mounted on the launching car, the general arrangement of the struts
and the clutch-hook can be readily seen; and from Plate 42, Figs. 1, 2, and
3, which show in detail most of the important features of the clutch-post
and its clutch, a very good idea of the size of the different parts may be had
by observing that the distance from the fulcrum of each half of the hook to
the pin by which it was connected through the universal joint to the vertical
rods is five inches. As previously stated, this clutch-hook gripped the lower
pyramid and pulled the bearing points of the frame firmly against the
Page 286
forward and rear struts of the launching car, and in launching the aerodrome
the triggers arranged on the bottom of the car, which at the proper time pull
on the vertical rods and thereby force the two halves of the clutch-hook
apart, are so arranged that they strike a cross-beam at the front end of the
track one inch before the triggers, which keep the struts from being pulled
down by their springs, which tend to fold them up and force them down
against the car. The triggers, which prevent the struts from being folded
down, strike a cross-beam in the track one foot before the buffer pistons on
the end of the car begin to enter the buffer cylinders at the end of the track,
and, consequently, one foot before the folding prop, which supports the
front end of the track, is knocked out by the car striking a special trigger
which allows this folding prop to swing forward when the front end of the
track folds down to insure that the aerodrome will not become entangled
with the car, even though the aerodrome be not quite up to soaring speed at
the moment of launching. The manner in which this front end of the track
folds down can be very readily seen by comparing Plate 43 with Plate 95 of
Chapter XII ◊, the former showing the front end of the track in horizontal
position, with [p161] the aerodrome at the extreme rear end just preparatory
to launching, and the latter showing the front end of the track folded down
with the hinged prop standing outward in its downward path and the
aerodrome just launched. These photographs will be more particularly
referred to later, but attention is here called to them so that the description
immediately following may be more easily understood.
Although this method of launching the aerodrome seemed to Mr.
Langley, both theoretically and from the experience with the models, to be a
satisfactory and feasible plan, there were two very important respects in
which it seemed from the very first open to objection. In the first place, it
was necessary that the aerodrome should be launched as nearly at its
soaring speed as possible, because either an excess or deficiency of speed
interfered to some extent with the equilibrium of the machine. So many
factors were involved in the determination of what this final velocity should
be that it seemed almost impossible to be sure of the results until at least
one test of the aerodrome had been made. In the second place it was not
the triggers arranged on the bottom of the car, which at the proper time pull
on the vertical rods and thereby force the two halves of the clutch-hook
apart, are so arranged that they strike a cross-beam at the front end of the
track one inch before the triggers, which keep the struts from being pulled
down by their springs, which tend to fold them up and force them down
against the car. The triggers, which prevent the struts from being folded
down, strike a cross-beam in the track one foot before the buffer pistons on
the end of the car begin to enter the buffer cylinders at the end of the track,
and, consequently, one foot before the folding prop, which supports the
front end of the track, is knocked out by the car striking a special trigger
which allows this folding prop to swing forward when the front end of the
track folds down to insure that the aerodrome will not become entangled
with the car, even though the aerodrome be not quite up to soaring speed at
the moment of launching. The manner in which this front end of the track
folds down can be very readily seen by comparing Plate 43 with Plate 95 of
Chapter XII ◊, the former showing the front end of the track in horizontal
position, with [p161] the aerodrome at the extreme rear end just preparatory
to launching, and the latter showing the front end of the track folded down
with the hinged prop standing outward in its downward path and the
aerodrome just launched. These photographs will be more particularly
referred to later, but attention is here called to them so that the description
immediately following may be more easily understood.
Although this method of launching the aerodrome seemed to Mr.
Langley, both theoretically and from the experience with the models, to be a
satisfactory and feasible plan, there were two very important respects in
which it seemed from the very first open to objection. In the first place, it
was necessary that the aerodrome should be launched as nearly at its
soaring speed as possible, because either an excess or deficiency of speed
interfered to some extent with the equilibrium of the machine. So many
factors were involved in the determination of what this final velocity should
be that it seemed almost impossible to be sure of the results until at least
one test of the aerodrome had been made. In the second place it was not
Page 287
known whether the rapid acceleration of the car would seriously interfere
with the equilibrium of the aviator.
In reference to the first question it was, of course, known that a freely
falling body acquires a speed of 32 feet per second at the end of the first
second after having fallen a distance of 16 feet. It was proposed to launch
the aerodrome at approximately 35 feet per second; and, since the distance
over which the car would pass in acquiring this speed was approximately 60
feet, the rate of acceleration would, of course, be less than that for a freely
falling body. The conditions in the two cases, however, are quite different.
In the case of the freely falling body there is the constant force of gravity
which causes the acceleration. In the case of the aerodrome the car is
initially standing still but ready to be acted upon by the combined force of
the thrust of the propellers and the tension of the springs. The propeller
thrust is approximately 450 pounds at the moment of releasing the car,
while the spring tension adds approximately 400 pounds more pull, giving a
total pull of 850 pounds acting on the car at the start. The weight of the
aerodrome including the aeronaut being approximately 850 pounds, and the
weight of the car being approximately 450 pounds, the total weight to be
accelerated is 1300 pounds. The resistance of the car and the aerodrome is
zero at the moment the car is released, and increases approximately as the
square of the velocity until it reaches approximately 300 pounds at the
soaring speed of the aerodrome; while on the other hand the spring tension
decreases uniformly from 400 pounds at the start to approximately 76
pounds at the end of the track, and the thrust due to the propellers decreases
from 450 pounds at the start to approximately 250 pounds at the moment of
launching. Consequently, it is in a general way clear that the rate of
acceleration of the aerodrome and car decrease, probably in a geometric
ratio, the rate of acceleration [p162] at the moment of launching the
aerodrome being much less than that of a freely falling body. Since so many
factors enter into the problem no confidence was felt in calculations as to
what the rate of acceleration would be. It was, therefore, decided to
determine it experimentally at the same time that tests were made on the car
to determine what spring tension would be necessary to enable the
with the equilibrium of the aviator.
In reference to the first question it was, of course, known that a freely
falling body acquires a speed of 32 feet per second at the end of the first
second after having fallen a distance of 16 feet. It was proposed to launch
the aerodrome at approximately 35 feet per second; and, since the distance
over which the car would pass in acquiring this speed was approximately 60
feet, the rate of acceleration would, of course, be less than that for a freely
falling body. The conditions in the two cases, however, are quite different.
In the case of the freely falling body there is the constant force of gravity
which causes the acceleration. In the case of the aerodrome the car is
initially standing still but ready to be acted upon by the combined force of
the thrust of the propellers and the tension of the springs. The propeller
thrust is approximately 450 pounds at the moment of releasing the car,
while the spring tension adds approximately 400 pounds more pull, giving a
total pull of 850 pounds acting on the car at the start. The weight of the
aerodrome including the aeronaut being approximately 850 pounds, and the
weight of the car being approximately 450 pounds, the total weight to be
accelerated is 1300 pounds. The resistance of the car and the aerodrome is
zero at the moment the car is released, and increases approximately as the
square of the velocity until it reaches approximately 300 pounds at the
soaring speed of the aerodrome; while on the other hand the spring tension
decreases uniformly from 400 pounds at the start to approximately 76
pounds at the end of the track, and the thrust due to the propellers decreases
from 450 pounds at the start to approximately 250 pounds at the moment of
launching. Consequently, it is in a general way clear that the rate of
acceleration of the aerodrome and car decrease, probably in a geometric
ratio, the rate of acceleration [p162] at the moment of launching the
aerodrome being much less than that of a freely falling body. Since so many
factors enter into the problem no confidence was felt in calculations as to
what the rate of acceleration would be. It was, therefore, decided to
determine it experimentally at the same time that tests were made on the car
to determine what spring tension would be necessary to enable the
Page 288
aerodrome and car to acquire soaring speed by the time they reached the
end of the track.
It was obviously impossible to make this initial test with the aerodrome
mounted on the launching car, as the aerodrome would certainly wreck both
itself and the car were it allowed to remain fastened when the car was
stopped at the end of the track. It was, therefore, decided to make the tests
by mounting on the car boards which would have a head resistance equal to
that of the aerodrome. In order to minimize as much as possible the blow
due to the car striking the buffers at the end of the track, the car had been
made as light as possible. On this account it was felt to be unwise to risk
adding to it a weight of 850 pounds to represent the aerodrome, and
supplying an additional spring tension to represent the thrust of the
propellers, as the total effect of the added weight and the added pull would
certainly completely demolish the car. By calculation it was found that the
omission of the 850 pounds weight of the aerodrome and the spring tension
to represent the thrust of the propellers would practically counterbalance
each other; and that if sufficient spring tension were provided to cause the
car, with the light boards representing the head resistance of the aerodrome,
to reach the soaring speed by the time it arrived at the end of the track, it
would be safe to assume that this spring tension would be sufficient for use
in launching the aerodrome.
The method of measuring the final speed of the launching car for the
models consisted in fastening a strip of smoked paper to the launching car
in such a position that it was drawn past a stylus fastened to the end of a
vibrating tuning fork placed at the end of the track. This had proved
perfectly successful, but it gave a record merely of the final speed attained
by the car at the moment of launching the aerodrome. In the case of the
large aerodrome it was desirable to have a record of the speed of the car
during the first few feet, and also at several other points in its travel down
the launching track, and the more numerous these points the better. Short
strips of copper were accordingly placed every twelve inches along the
length of the track, and these were connected by a wire to one terminal of a
small electric battery. Mounted on the car, in such a way that it would be
end of the track.
It was obviously impossible to make this initial test with the aerodrome
mounted on the launching car, as the aerodrome would certainly wreck both
itself and the car were it allowed to remain fastened when the car was
stopped at the end of the track. It was, therefore, decided to make the tests
by mounting on the car boards which would have a head resistance equal to
that of the aerodrome. In order to minimize as much as possible the blow
due to the car striking the buffers at the end of the track, the car had been
made as light as possible. On this account it was felt to be unwise to risk
adding to it a weight of 850 pounds to represent the aerodrome, and
supplying an additional spring tension to represent the thrust of the
propellers, as the total effect of the added weight and the added pull would
certainly completely demolish the car. By calculation it was found that the
omission of the 850 pounds weight of the aerodrome and the spring tension
to represent the thrust of the propellers would practically counterbalance
each other; and that if sufficient spring tension were provided to cause the
car, with the light boards representing the head resistance of the aerodrome,
to reach the soaring speed by the time it arrived at the end of the track, it
would be safe to assume that this spring tension would be sufficient for use
in launching the aerodrome.
The method of measuring the final speed of the launching car for the
models consisted in fastening a strip of smoked paper to the launching car
in such a position that it was drawn past a stylus fastened to the end of a
vibrating tuning fork placed at the end of the track. This had proved
perfectly successful, but it gave a record merely of the final speed attained
by the car at the moment of launching the aerodrome. In the case of the
large aerodrome it was desirable to have a record of the speed of the car
during the first few feet, and also at several other points in its travel down
the launching track, and the more numerous these points the better. Short
strips of copper were accordingly placed every twelve inches along the
length of the track, and these were connected by a wire to one terminal of a
small electric battery. Mounted on the car, in such a way that it would be
Page 289
drawn across these contact strips, was a copper brush arranged to make
continuous contact with another wire stretched along the track, this second
wire being connected to the other terminal of the electric battery and having
in its circuit the magnet which actuated a pen on a chronograph. Since the
rate of revolution of the chronograph barrel was known, the [p163] distance
between the marks which the magnet would cause the pen to make when its
circuit was closed by the brush on the car passing across the contact strips
on the track would give correct measures of the time consumed by the car
in passing over each twelve inches of its travel. Upon test, however, it was
found impossible to get the chronograph magnets to work rapidly enough to
respond to the very rapid opening and closing of the circuit after the car had
passed over the first one-quarter of its length of travel. As a large part of the
slowness of action seemed to be due to the weight of the fountain pens, they
were replaced by small glass tubes drawn out to a fine point and containing
a small amount of ink. These seemed, however, to be still too heavy to
respond to the rapid closing of the circuit unless the contacts were made
unduly long. The contacts were finally made three inches long and placed
only every three feet along the track, but just as these contacts were
completed and placed in position the clock-work of the chronograph itself
became deranged. Before it could be repaired, the tests were discontinued,
as everything was in readiness for the boat to proceed down the river where
the actual tests in free flight were to be made. Tests of the final speed of the
car were, however, made by the tuning-fork method, and the springs were
adjusted until their tension was sufficient to cause the car to attain a speed
of thirty-five feet a second at a point three inches in front of the point at
which the aerodrome would be released from the car.
continuous contact with another wire stretched along the track, this second
wire being connected to the other terminal of the electric battery and having
in its circuit the magnet which actuated a pen on a chronograph. Since the
rate of revolution of the chronograph barrel was known, the [p163] distance
between the marks which the magnet would cause the pen to make when its
circuit was closed by the brush on the car passing across the contact strips
on the track would give correct measures of the time consumed by the car
in passing over each twelve inches of its travel. Upon test, however, it was
found impossible to get the chronograph magnets to work rapidly enough to
respond to the very rapid opening and closing of the circuit after the car had
passed over the first one-quarter of its length of travel. As a large part of the
slowness of action seemed to be due to the weight of the fountain pens, they
were replaced by small glass tubes drawn out to a fine point and containing
a small amount of ink. These seemed, however, to be still too heavy to
respond to the rapid closing of the circuit unless the contacts were made
unduly long. The contacts were finally made three inches long and placed
only every three feet along the track, but just as these contacts were
completed and placed in position the clock-work of the chronograph itself
became deranged. Before it could be repaired, the tests were discontinued,
as everything was in readiness for the boat to proceed down the river where
the actual tests in free flight were to be made. Tests of the final speed of the
car were, however, made by the tuning-fork method, and the springs were
adjusted until their tension was sufficient to cause the car to attain a speed
of thirty-five feet a second at a point three inches in front of the point at
which the aerodrome would be released from the car.
Page 290
[p164] ◊
CHAPTER V
CONSTRUCTION OF FRAME OF LARGE AERODROME
The general plan for the large aerodrome was never a matter of
uncertainty. At the time when the first general designs were made there had
been in the history of mankind only one type of machine, that of the steam-
driven Langley models, which had proved capable of flight for any
considerable distance. Furthermore, the selection of this type had been the
result not of sudden fancy or of purely theoretical consideration, but of
years of the most careful experimentation, in the course of which nearly
every conceivable style of machine had been tested with some form of
power. It would have been worse than folly, therefore, if the one clear path
had been left to seek some unknown way.
It was fully realized from the first, however, that the increase in size
alone would make necessary in the design for the large aerodrome a great
many modifications from the designs of the steam-driven models. It was not
possible here, as in nearly every other kind of structure, simply to magnify
uniformly the parts and proportions of the small machine in order to obtain
a successful large one. This is particularly true in the case of the aerodrome,
because the rapid increase of weight in the larger structure is out of all
proportion to the increase in strength, while it is very desirable that the
more expensive machine which is designed to carry a human being shall be
relatively even stronger than the easily replaced model. This problem of
increasing size without sacrificing strength and stability, it was known from
the beginning, would be encountered in a particularly difficult form in
designing the frame of the large machine, and was to be solved not by the
discovery of some new and wonderfully strong material, but by
improvements both in the general plan and the details of the machine. Here,
as is often the case, it was not the large changes in the design but the
improvements in small and sometimes seemingly unimportant details which
demanded the most careful consideration and, as a whole, contributed most
CHAPTER V
CONSTRUCTION OF FRAME OF LARGE AERODROME
The general plan for the large aerodrome was never a matter of
uncertainty. At the time when the first general designs were made there had
been in the history of mankind only one type of machine, that of the steam-
driven Langley models, which had proved capable of flight for any
considerable distance. Furthermore, the selection of this type had been the
result not of sudden fancy or of purely theoretical consideration, but of
years of the most careful experimentation, in the course of which nearly
every conceivable style of machine had been tested with some form of
power. It would have been worse than folly, therefore, if the one clear path
had been left to seek some unknown way.
It was fully realized from the first, however, that the increase in size
alone would make necessary in the design for the large aerodrome a great
many modifications from the designs of the steam-driven models. It was not
possible here, as in nearly every other kind of structure, simply to magnify
uniformly the parts and proportions of the small machine in order to obtain
a successful large one. This is particularly true in the case of the aerodrome,
because the rapid increase of weight in the larger structure is out of all
proportion to the increase in strength, while it is very desirable that the
more expensive machine which is designed to carry a human being shall be
relatively even stronger than the easily replaced model. This problem of
increasing size without sacrificing strength and stability, it was known from
the beginning, would be encountered in a particularly difficult form in
designing the frame of the large machine, and was to be solved not by the
discovery of some new and wonderfully strong material, but by
improvements both in the general plan and the details of the machine. Here,
as is often the case, it was not the large changes in the design but the
improvements in small and sometimes seemingly unimportant details which
demanded the most careful consideration and, as a whole, contributed most
Page 291
to the final result. For this reason, as well as because the large changes,
when pointed out, are usually easily understood, the present chapter is for
the most part a description of the improvement of details.
From the experience gained in the construction of the frames of the
several steam-driven models, it was decided that the frame for the large
aerodrome must consist essentially of two principal parts. First, a rigid
backbone was required, extending from the point of attachment of the front
wings to the point of attachment of the rear wings; and this backbone, for
convenience designated [p165] the “main frame,” must support the second
principal part, the “transverse frame,” which formed a cross with the main
frame, and at the ends of which the propellers were mounted. While it was
necessary that this transverse frame should have considerable rigidity and
strength in a vertical direction, yet its main strength and stiffness was
required in the horizontal plane for withstanding the thrust of the propellers.
It had been possible to construct the frames of the later steam-driven
models stiff enough, and at the same time light enough, by the use of
properly proportioned steel tubing, but calculation very soon showed that in
order to secure sufficient rigidity for the frame of the large aerodrome and
at the same time keep the weight within the permissible limit, it would be
necessary to depend very largely on guy-wires and to use tubing only for
forming the struts against which the guy-wires should act. But this
obviously introduced a new series of problems. The extensive system of
guy-wires necessary would add materially to the head resistance of the
aerodrome, and this might conceivably be so great as to require more
propulsive power than would be required for a frame heavier but
unincumbered by the head resistance of the wires. It became necessary to
consider these problems, but no data were accessible from which the head
resistance could be computed with any confidence. The coefficient of
resistance for a cylindrical body moving through the air in a direction
perpendicular to its length may in general be taken as one-half that of a flat
body of the same cross-section; but it was thought very certain that, owing
to the fact that tightly stretched wires are in constant vibration when the
aerodrome is in the air, the resistance of the wires must be considerably
when pointed out, are usually easily understood, the present chapter is for
the most part a description of the improvement of details.
From the experience gained in the construction of the frames of the
several steam-driven models, it was decided that the frame for the large
aerodrome must consist essentially of two principal parts. First, a rigid
backbone was required, extending from the point of attachment of the front
wings to the point of attachment of the rear wings; and this backbone, for
convenience designated [p165] the “main frame,” must support the second
principal part, the “transverse frame,” which formed a cross with the main
frame, and at the ends of which the propellers were mounted. While it was
necessary that this transverse frame should have considerable rigidity and
strength in a vertical direction, yet its main strength and stiffness was
required in the horizontal plane for withstanding the thrust of the propellers.
It had been possible to construct the frames of the later steam-driven
models stiff enough, and at the same time light enough, by the use of
properly proportioned steel tubing, but calculation very soon showed that in
order to secure sufficient rigidity for the frame of the large aerodrome and
at the same time keep the weight within the permissible limit, it would be
necessary to depend very largely on guy-wires and to use tubing only for
forming the struts against which the guy-wires should act. But this
obviously introduced a new series of problems. The extensive system of
guy-wires necessary would add materially to the head resistance of the
aerodrome, and this might conceivably be so great as to require more
propulsive power than would be required for a frame heavier but
unincumbered by the head resistance of the wires. It became necessary to
consider these problems, but no data were accessible from which the head
resistance could be computed with any confidence. The coefficient of
resistance for a cylindrical body moving through the air in a direction
perpendicular to its length may in general be taken as one-half that of a flat
body of the same cross-section; but it was thought very certain that, owing
to the fact that tightly stretched wires are in constant vibration when the
aerodrome is in the air, the resistance of the wires must be considerably
Page 292
greater than would be calculated from treating them as cylinders having a
coefficient of 0.5. Unfortunately, no data on the resistance of vibrating
wires were at hand. Before proceeding with the designs for the guying of
the frame, therefore, the following brief series of tests was made in
November, 1898, on the whirling table, in order to learn approximately the
resistance that the proposed system of guy-wires for the large aerodrome
would offer:
ME AS UR E ME NT S OF T HE RE S I S TAN CE O F GUY- WI R E S ,
U S I NG F R AME AT TA CH E D TO “B AL A NCE .”
RESISTANCE OF FRAME WITHOUT WIRES.
Frame consists of: 4 tubes, 1 cm. diameter, 14.5 cm. long; 2 tubes, 1 cm. diameter, 41
cm. long; 2 tubes, 1 cm. diameter, 101 cm. long.
Revolutions of turn- Velocity of frame. Resistance. Calculated resistance of
table per minute. Feet per minute. Grammes. r. frame. Grammes.
6.75 608 11.5 14.2
9.75 877 34.0 29.6
12.0 1080 51.8 44.8
16.35 1475 97.0 83.8
19.75 1775 134.0 121.3
22.7 2045 168.0 161.2
25.5 2290 205.0 202.0
[p166]
RESISTANCE OF FRAME WITH 1ST SET OF WIRES.
First set of wires: 16 wires, 0.6 mm. diameter, 102 cm. long; 6 wires, 0.6 mm. diameter,
42 cm. long.
Revolutions of Velocity of Resistance of frame Resistance of Calculated
turn-table per wires. Feet and wires. wires. resistance of
minute. per minute. Grammes. R1. R1−r =r1. wires. Grammes.
9.75 877 47.5 13.5 8.88
12.0 1080 73.5 21.7 13.47
13.75 1237 93.5 25.5 17.65
17.25 1550 144.0 37.0 27.7
20.25 1822 187.0 45.5 38.4
22.50 2025 216.0 47.5 47.4
22.875 2060 225.0 52.0 49.0
24.56 2215 250.0 56.5 56.7
coefficient of 0.5. Unfortunately, no data on the resistance of vibrating
wires were at hand. Before proceeding with the designs for the guying of
the frame, therefore, the following brief series of tests was made in
November, 1898, on the whirling table, in order to learn approximately the
resistance that the proposed system of guy-wires for the large aerodrome
would offer:
ME AS UR E ME NT S OF T HE RE S I S TAN CE O F GUY- WI R E S ,
U S I NG F R AME AT TA CH E D TO “B AL A NCE .”
RESISTANCE OF FRAME WITHOUT WIRES.
Frame consists of: 4 tubes, 1 cm. diameter, 14.5 cm. long; 2 tubes, 1 cm. diameter, 41
cm. long; 2 tubes, 1 cm. diameter, 101 cm. long.
Revolutions of turn- Velocity of frame. Resistance. Calculated resistance of
table per minute. Feet per minute. Grammes. r. frame. Grammes.
6.75 608 11.5 14.2
9.75 877 34.0 29.6
12.0 1080 51.8 44.8
16.35 1475 97.0 83.8
19.75 1775 134.0 121.3
22.7 2045 168.0 161.2
25.5 2290 205.0 202.0
[p166]
RESISTANCE OF FRAME WITH 1ST SET OF WIRES.
First set of wires: 16 wires, 0.6 mm. diameter, 102 cm. long; 6 wires, 0.6 mm. diameter,
42 cm. long.
Revolutions of Velocity of Resistance of frame Resistance of Calculated
turn-table per wires. Feet and wires. wires. resistance of
minute. per minute. Grammes. R1. R1−r =r1. wires. Grammes.
9.75 877 47.5 13.5 8.88
12.0 1080 73.5 21.7 13.47
13.75 1237 93.5 25.5 17.65
17.25 1550 144.0 37.0 27.7
20.25 1822 187.0 45.5 38.4
22.50 2025 216.0 47.5 47.4
22.875 2060 225.0 52.0 49.0
24.56 2215 250.0 56.5 56.7
Page 293
RESISTANCE OF FRAME WITH 2D SET OF WIRES.
Second set of wires: 15 wires, 1.2 mm. diameter, 102 cm. long; 2 wires, 1.2 mm.
diameter, 42 cm. long.
Revolutions of Velocity of Resistance of frame Resistance of Calculated
turn-table per wires. Feet and wires. wires. resistance of
minute. per minute. Grammes. R2. R2−r =r2. wires. Grammes.
9.25 833 54.0 26.5 15.35
9.35 841 55.0 27.0 15.4
11.3 1018 82.0 36.75 22.65
11.5 1035 82.0 35.25 23.4
13.0 1170 104.5 43.0 29.9
13.15 1185 105.0 42.5 30.60
16.7 1505 160.0 59.0 49.5
16.75 1510 160.0 58.0 49.9
19.5 1755 196.0 64.0 67.4
19.7 1770 203.0 69.5 68.5
21.60 1945 236.0 77.0 82.6
21.65 1950 237.0 77.75 83.2
21.75 1957 235.0 75.5 83.7
RESISTANCE OF FRAME WITH 3D SET OF WIRES.
Third set of wires: 15 wires, 2 mm. diameter, 102 cm. long; 2 wires, 2 mm. diameter, 42
cm. long.
Revolutions of Velocity of Resistance of frame Resistance of Calculated
turn-table per wires. Feet and wires. wires. resistance of
minute. per minute. Grammes. R3. R3−r =r3. wires. Grammes.
9.25 833 65 37.5 25.2
11.55 1040 91 43.5 39.35
11.55 1040 101 53.5 39.35
15.25 1375 160 75.0 68.7
18.1 1630 203 86.5 96.6
19.25 1735 221 92.0 109.5
19.25 1735 216 87.0 109.5
20.63 1860 237 90.5 125.8
The last column of these tables is calculated for a coefficient of form
equal to 0.5, which has been found to be approximately correct for a rigid
cylindrical body.
These tables are not sufficiently extensive to determine accurately the
exact resistance that wires of various sizes will offer at given velocities, or
to serve as the basis for the deduction of formulæ, and were not made for
that purpose. However, from the above data, and the curves plotted in Plate
44, it will be seen that some unexpected results were obtained.
Second set of wires: 15 wires, 1.2 mm. diameter, 102 cm. long; 2 wires, 1.2 mm.
diameter, 42 cm. long.
Revolutions of Velocity of Resistance of frame Resistance of Calculated
turn-table per wires. Feet and wires. wires. resistance of
minute. per minute. Grammes. R2. R2−r =r2. wires. Grammes.
9.25 833 54.0 26.5 15.35
9.35 841 55.0 27.0 15.4
11.3 1018 82.0 36.75 22.65
11.5 1035 82.0 35.25 23.4
13.0 1170 104.5 43.0 29.9
13.15 1185 105.0 42.5 30.60
16.7 1505 160.0 59.0 49.5
16.75 1510 160.0 58.0 49.9
19.5 1755 196.0 64.0 67.4
19.7 1770 203.0 69.5 68.5
21.60 1945 236.0 77.0 82.6
21.65 1950 237.0 77.75 83.2
21.75 1957 235.0 75.5 83.7
RESISTANCE OF FRAME WITH 3D SET OF WIRES.
Third set of wires: 15 wires, 2 mm. diameter, 102 cm. long; 2 wires, 2 mm. diameter, 42
cm. long.
Revolutions of Velocity of Resistance of frame Resistance of Calculated
turn-table per wires. Feet and wires. wires. resistance of
minute. per minute. Grammes. R3. R3−r =r3. wires. Grammes.
9.25 833 65 37.5 25.2
11.55 1040 91 43.5 39.35
11.55 1040 101 53.5 39.35
15.25 1375 160 75.0 68.7
18.1 1630 203 86.5 96.6
19.25 1735 221 92.0 109.5
19.25 1735 216 87.0 109.5
20.63 1860 237 90.5 125.8
The last column of these tables is calculated for a coefficient of form
equal to 0.5, which has been found to be approximately correct for a rigid
cylindrical body.
These tables are not sufficiently extensive to determine accurately the
exact resistance that wires of various sizes will offer at given velocities, or
to serve as the basis for the deduction of formulæ, and were not made for
that purpose. However, from the above data, and the curves plotted in Plate
44, it will be seen that some unexpected results were obtained.
Page 294
PL. 44. RESISTANCE OF WIRES AT GIVEN VELOCITIES ◊
[p167]
[p167]
Page 295
These results are fairly well summarized in the following general
statements: First, that the coefficient of resistance increases to some degree
as the size of the wire is decreased; second, that in the case of wires of the
size which it was expected to use, and at approximately the soaring speed of
the aerodrome, the resistance is certainly not greater than 75 per cent, and
more probably less than 50 per cent of the resistance encountered by a flat
surface of the same projected area; third, that the coefficient of resistance
did not seem to be increased by the vibration of the wires. On the contrary,
it was noted during the experiments that when they reached a speed which
just caused them to “sing,” there was a marked diminution in the resistance.
This statement is made, however, with some reserve, for it is probable that
the singing of the wires was due to vibration in the horizontal plane, and it
is not definitely known what the effect would be of vibration in the vertical
plane.
To make the very extensive experiments necessary to determine these
propositions conclusively would have required much more time than could
at this period be spared from the actual constructional work on the
aerodrome. Nevertheless, the data did seem to indicate that it was at least
not unwise to employ the extensive system of guying which had been
planned in order to give the necessary strength to the frame of the large
aerodrome. This plan of construction was, therefore, definitely adopted, and
as a result of later experience the system of guying was still further
extended.
As the transverse frame had to be made comparatively rigid in order to
prevent undue binding of the bearings of the transmission and propeller
shafts, it was necessary to make it intrinsically stronger and, therefore,
heavier in proportion to its size than the main frame. The main frame,
although requiring great strength to enable it to withstand the strains, both
torsional and direct, which were imposed upon it by the weights which it
supported, did not need excessive rigidity, and could, indeed, be distorted
an appreciable amount without danger of any serious effect on the action of
the wings or rudder; but even a small amount of distortion in the transverse
statements: First, that the coefficient of resistance increases to some degree
as the size of the wire is decreased; second, that in the case of wires of the
size which it was expected to use, and at approximately the soaring speed of
the aerodrome, the resistance is certainly not greater than 75 per cent, and
more probably less than 50 per cent of the resistance encountered by a flat
surface of the same projected area; third, that the coefficient of resistance
did not seem to be increased by the vibration of the wires. On the contrary,
it was noted during the experiments that when they reached a speed which
just caused them to “sing,” there was a marked diminution in the resistance.
This statement is made, however, with some reserve, for it is probable that
the singing of the wires was due to vibration in the horizontal plane, and it
is not definitely known what the effect would be of vibration in the vertical
plane.
To make the very extensive experiments necessary to determine these
propositions conclusively would have required much more time than could
at this period be spared from the actual constructional work on the
aerodrome. Nevertheless, the data did seem to indicate that it was at least
not unwise to employ the extensive system of guying which had been
planned in order to give the necessary strength to the frame of the large
aerodrome. This plan of construction was, therefore, definitely adopted, and
as a result of later experience the system of guying was still further
extended.
As the transverse frame had to be made comparatively rigid in order to
prevent undue binding of the bearings of the transmission and propeller
shafts, it was necessary to make it intrinsically stronger and, therefore,
heavier in proportion to its size than the main frame. The main frame,
although requiring great strength to enable it to withstand the strains, both
torsional and direct, which were imposed upon it by the weights which it
supported, did not need excessive rigidity, and could, indeed, be distorted
an appreciable amount without danger of any serious effect on the action of
the wings or rudder; but even a small amount of distortion in the transverse
Page 296
frame might easily cause such friction at the bearings of the shafts as to
absorb fifty per cent or more of the engine power.
In the photographs, Plates 45 to 48, which show the actual condition of
the frame on January 31 and February 1, 1900, the letters A, B, C, D, E, F,
G, H and I designate parts of the main frame, A and H being the rear and
front midrods, respectively, to which the wings were to be attached. B and I
are curved extensions of the starboard main tube, the port main tube being
exactly similar, and C, D, E, F and G are cross-tubes which connect the
midrods to the port and starboard tubes. R is the front main tube of the
transverse frame, the rear main tube being exactly similar, and both being
connected to the main tubes of the main frame where they cross them. The
ends of the main tubes of the [p168] transverse frame are joined together by
the “bed plates” L, which are of I-beam section, and have mounted on their
outer faces the bearings which support the propeller shafts. At V are bevel
gears mounted on the propeller shafts, which are driven by co-acting bevel
gears, M, mounted on the outer ends of the transmission shafts, O, the latter
being at this point firmly supported in bearings mounted on the inner faces
of the bed plates and steadied by the intermediate bearings, N. The two
transmission shafts are seen to be not in line, the rotary cylinder engine that
was then under construction requiring this arrangement. The bed plates, L,
are further stiffened by the brace tubes, K, and the transverse frame is
braced against the thrust of the propellers by the tubes J. The four tubes, P,
unite at their upper ends to form what was designated as the upper
“pyramid,” and the wires, S and T, radiate from its apex to the rear and
front, respectively, of the main frame. The lower “pyramid,” on the under
side of the frame, also has similar wires running fore and aft. The main
portions of both frames are further strengthened by their sub-frames, which
merge together, and the main tubes of the main frame are individually
stiffened in the vertical plane by a minor system of guying. The scales
shown in the photographs are calibrated in metres.
It is to be particularly noted that the midrod, which had heretofore
formed the backbone of the main frame, was now made to act merely as a
means of attaching the wings to the frame, the main strength of the frame
absorb fifty per cent or more of the engine power.
In the photographs, Plates 45 to 48, which show the actual condition of
the frame on January 31 and February 1, 1900, the letters A, B, C, D, E, F,
G, H and I designate parts of the main frame, A and H being the rear and
front midrods, respectively, to which the wings were to be attached. B and I
are curved extensions of the starboard main tube, the port main tube being
exactly similar, and C, D, E, F and G are cross-tubes which connect the
midrods to the port and starboard tubes. R is the front main tube of the
transverse frame, the rear main tube being exactly similar, and both being
connected to the main tubes of the main frame where they cross them. The
ends of the main tubes of the [p168] transverse frame are joined together by
the “bed plates” L, which are of I-beam section, and have mounted on their
outer faces the bearings which support the propeller shafts. At V are bevel
gears mounted on the propeller shafts, which are driven by co-acting bevel
gears, M, mounted on the outer ends of the transmission shafts, O, the latter
being at this point firmly supported in bearings mounted on the inner faces
of the bed plates and steadied by the intermediate bearings, N. The two
transmission shafts are seen to be not in line, the rotary cylinder engine that
was then under construction requiring this arrangement. The bed plates, L,
are further stiffened by the brace tubes, K, and the transverse frame is
braced against the thrust of the propellers by the tubes J. The four tubes, P,
unite at their upper ends to form what was designated as the upper
“pyramid,” and the wires, S and T, radiate from its apex to the rear and
front, respectively, of the main frame. The lower “pyramid,” on the under
side of the frame, also has similar wires running fore and aft. The main
portions of both frames are further strengthened by their sub-frames, which
merge together, and the main tubes of the main frame are individually
stiffened in the vertical plane by a minor system of guying. The scales
shown in the photographs are calibrated in metres.
It is to be particularly noted that the midrod, which had heretofore
formed the backbone of the main frame, was now made to act merely as a
means of attaching the wings to the frame, the main strength of the frame
Page 297
being furnished by the two parallel fifty millimetre tubes which extended
the entire length of the frame and which, reinforced by the guy-wires,
formed a truss not only more rigid transversely, but also many times
stronger in its ability to resist torsional strains than could be secured by a
single tube of equal weight. In this plan of constructing the main frame, the
pyramids constituted a very important element, for with the guy-wires
arranged as they were it was impossible for any portion of the frame to
experience a stress which was not transmitted in some way to the pyramids.
In the frame, as here shown, these pyramids were formed of tubes 15 mm.
in diameter, 0.5 mm. thick, stiffened against buckling under the end
pressure by means of the cross-braces, which united them near their
midpoints. While the sole function of the upper pyramid was to serve in the
system of guying the frame, the lower pyramid not only served a similar
purpose, but also provided a means for holding the aerodrome to the
launching car in the process of launching it, the clutch-hooks gripping
around the short horizontal tube at the apex of the pyramid and thus
drawing the “bearing points” of the machine firmly against the uprights on
the car. In fact, the particular arrangement of these pyramids was largely
determined by this necessity for providing means for holding the aerodrome
to the launching car, and the form which seemed best suited to the purpose
was duplicated on the upper side of the frame.
the entire length of the frame and which, reinforced by the guy-wires,
formed a truss not only more rigid transversely, but also many times
stronger in its ability to resist torsional strains than could be secured by a
single tube of equal weight. In this plan of constructing the main frame, the
pyramids constituted a very important element, for with the guy-wires
arranged as they were it was impossible for any portion of the frame to
experience a stress which was not transmitted in some way to the pyramids.
In the frame, as here shown, these pyramids were formed of tubes 15 mm.
in diameter, 0.5 mm. thick, stiffened against buckling under the end
pressure by means of the cross-braces, which united them near their
midpoints. While the sole function of the upper pyramid was to serve in the
system of guying the frame, the lower pyramid not only served a similar
purpose, but also provided a means for holding the aerodrome to the
launching car in the process of launching it, the clutch-hooks gripping
around the short horizontal tube at the apex of the pyramid and thus
drawing the “bearing points” of the machine firmly against the uprights on
the car. In fact, the particular arrangement of these pyramids was largely
determined by this necessity for providing means for holding the aerodrome
to the launching car, and the form which seemed best suited to the purpose
was duplicated on the upper side of the frame.
Page 298
PL. 45. FRAME OF AERODROME A, JANUARY 31, 1900 ◊
Page 299
PL. 46. FRAME OF AERODROME A, JANUARY 31, 1900 ◊
Page 300
PL. 47. FRAME OF AERODROME A, FEBRUARY 1, 1900 ◊
Page 301
PL. 48. FRAME OF AERODROME A, FEBRUARY 1, 1900 ◊
[p169]
[p169]
Page 302
The “bearing points” were not attached to the frame at the time these
photographs were taken, but are seen leaning against the scales in the
foreground of Plate 46. Their position on the frame will be more clearly
seen in later photographs, where it will be noted that they were made use of
in the more elaborate system of guying which was adopted.
While, in general, the frame at this time seemed to be reasonably stiff and
strong, yet it was subjected to a very thorough test by supporting it at
different points and suspending from it weights to represent the various
parts, such as engine, aviator, wings, rudder and so forth, the deflections
which were produced by these weights being carefully noted. It was further
tested by subjecting it to vibratory strains, such as it would be likely to meet
in actual use. After this the whole frame was tested against torsional strains,
such as would be caused by the wind twisting one set of wings more than
the other. As a result of these tests it was decided that the frame should be
strengthened as far as it was possible to do so without greatly increasing the
weight, which even now was found to be rapidly increasing beyond what
had been calculated as permissible. The main guy-wires were replaced by
heavier and stronger ones, and while these were found to add somewhat to
the stiffness of the frame, yet something more seemed necessary to insure
safety.
The delay in securing the engine, which had been contracted for with a
guarantee that it would be delivered in February, 1899, had become so
serious and had delayed the completion of the frame to such an extent that
the question of building an exact duplicate of the large machine, but of one-
quarter its linear dimensions was being carefully considered at this time,
and it was decided to make no further changes in the guying of the large
frame until after the small one was built. On account of its smaller size
changes could be more readily and cheaply made on it, and the advantages
of different methods of guying could be just as well studied. Later, when
this was completed, it was found that, with the same system of guying that
had been used in the larger frame, the model was so very stiff that it did not
require any further strengthening, the smaller scale, of course, accounting
for the difference. What was thought to be the best system to follow in
photographs were taken, but are seen leaning against the scales in the
foreground of Plate 46. Their position on the frame will be more clearly
seen in later photographs, where it will be noted that they were made use of
in the more elaborate system of guying which was adopted.
While, in general, the frame at this time seemed to be reasonably stiff and
strong, yet it was subjected to a very thorough test by supporting it at
different points and suspending from it weights to represent the various
parts, such as engine, aviator, wings, rudder and so forth, the deflections
which were produced by these weights being carefully noted. It was further
tested by subjecting it to vibratory strains, such as it would be likely to meet
in actual use. After this the whole frame was tested against torsional strains,
such as would be caused by the wind twisting one set of wings more than
the other. As a result of these tests it was decided that the frame should be
strengthened as far as it was possible to do so without greatly increasing the
weight, which even now was found to be rapidly increasing beyond what
had been calculated as permissible. The main guy-wires were replaced by
heavier and stronger ones, and while these were found to add somewhat to
the stiffness of the frame, yet something more seemed necessary to insure
safety.
The delay in securing the engine, which had been contracted for with a
guarantee that it would be delivered in February, 1899, had become so
serious and had delayed the completion of the frame to such an extent that
the question of building an exact duplicate of the large machine, but of one-
quarter its linear dimensions was being carefully considered at this time,
and it was decided to make no further changes in the guying of the large
frame until after the small one was built. On account of its smaller size
changes could be more readily and cheaply made on it, and the advantages
of different methods of guying could be just as well studied. Later, when
this was completed, it was found that, with the same system of guying that
had been used in the larger frame, the model was so very stiff that it did not
require any further strengthening, the smaller scale, of course, accounting
for the difference. What was thought to be the best system to follow in
Page 303
strengthening the frame of the large machine was, however, first tried on
the smaller one, and it was found that for a very slight increase in weight a
very great increase in strength could be obtained. This change in the system
of guying consisted essentially of building a “trestle” of tubing at a point on
the upper side, midway between the pyramid and the rear end of the frame.
One of the former sets of guy-wires which passed to the rear of the frame
was then replaced by a set which started at the foot of the rear tubes of the
upper pyramid, passed over and was fastened to the trestle, and from there
passed to the rear end of the frame at the points where the longer guy-wires
from the pyramid had formerly been attached. The [p170] guy-wires on the
lower side of the frame, at the rear, were correspondingly changed so that
the upper and lower systems should be similar, the wires which started from
the main tubes at the foot of the pyramid passing to the bearing points, and
from there to the rear end of the frame.
In order to keep the main frame of the large aerodrome as short as
possible, it had originally been planned to make the distance between the
center of pressure of the front wings and the center of pressure of the rear
equal to five metres. When these same proportions were followed in the
quarter-size model, it was found that it brought the rear wings so close to
the propellers that their lifting effect was certain to be interfered with by the
blast of air created by the slip of the propellers. It was therefore decided that
all things considered it would be best to increase this distance between the
wings, even though this involved an increase in weight, partly on account of
the increased amount of tubing, and still more on account of the guy-wires
which it would be necessary to add in order to make up for the weakness
due to increased length. The large aerodrome frame was accordingly
lengthened 2.5 feet (76.2 cm.), and the guy-wire system was changed to that
clearly shown by the photographs of July 10, 1902, Plates 49, 50 and 51,
the black cross-lines on the background being 50 centimetres apart. From
an inspection of these photographs it will be seen that two sets of guy-wires
were carried from the upper and lower pyramids, respectively, towards the
rear of the frame, the first set being carried to the main tubes at the foot of
the “trestle” and the bearing points, and the second set to these same main
the smaller one, and it was found that for a very slight increase in weight a
very great increase in strength could be obtained. This change in the system
of guying consisted essentially of building a “trestle” of tubing at a point on
the upper side, midway between the pyramid and the rear end of the frame.
One of the former sets of guy-wires which passed to the rear of the frame
was then replaced by a set which started at the foot of the rear tubes of the
upper pyramid, passed over and was fastened to the trestle, and from there
passed to the rear end of the frame at the points where the longer guy-wires
from the pyramid had formerly been attached. The [p170] guy-wires on the
lower side of the frame, at the rear, were correspondingly changed so that
the upper and lower systems should be similar, the wires which started from
the main tubes at the foot of the pyramid passing to the bearing points, and
from there to the rear end of the frame.
In order to keep the main frame of the large aerodrome as short as
possible, it had originally been planned to make the distance between the
center of pressure of the front wings and the center of pressure of the rear
equal to five metres. When these same proportions were followed in the
quarter-size model, it was found that it brought the rear wings so close to
the propellers that their lifting effect was certain to be interfered with by the
blast of air created by the slip of the propellers. It was therefore decided that
all things considered it would be best to increase this distance between the
wings, even though this involved an increase in weight, partly on account of
the increased amount of tubing, and still more on account of the guy-wires
which it would be necessary to add in order to make up for the weakness
due to increased length. The large aerodrome frame was accordingly
lengthened 2.5 feet (76.2 cm.), and the guy-wire system was changed to that
clearly shown by the photographs of July 10, 1902, Plates 49, 50 and 51,
the black cross-lines on the background being 50 centimetres apart. From
an inspection of these photographs it will be seen that two sets of guy-wires
were carried from the upper and lower pyramids, respectively, towards the
rear of the frame, the first set being carried to the main tubes at the foot of
the “trestle” and the bearing points, and the second set to these same main
Page 304
tubes at the second cross-tube. The sets of wires which started from the feet
of the pyramids were carried over the “trestle” on the upper side and the
bearing points on the lower side, and both joined to the main tubes at the
rear cross-tube. Additional cross-guy-wires for stiffening the frame
sideways were added in each of the squares formed by the junction of the
cross-tubes with the main tubes. A secondary system of truss guy-wires
running over short guy-posts attached to the tubes of the main frame also
contributed to the strength and rigidity of the whole.
Although the pyramids had shown no signs of weakness, nevertheless,
because of increased strains due to the lengthening of the main frame, it
was thought advisable to make them stronger. Instead of the 15-mm. tubing,
which had formerly been used, 25-mm. tubing of the same thickness was
therefore substituted, and additional cross-braces were added, as will be
seen from the photographs, and from the scale drawings in Plates 52, 53 and
54, which show the aerodrome as it was when completed. The numerals
attached to these drawings refer to the detail drawings shown in later plates.
of the pyramids were carried over the “trestle” on the upper side and the
bearing points on the lower side, and both joined to the main tubes at the
rear cross-tube. Additional cross-guy-wires for stiffening the frame
sideways were added in each of the squares formed by the junction of the
cross-tubes with the main tubes. A secondary system of truss guy-wires
running over short guy-posts attached to the tubes of the main frame also
contributed to the strength and rigidity of the whole.
Although the pyramids had shown no signs of weakness, nevertheless,
because of increased strains due to the lengthening of the main frame, it
was thought advisable to make them stronger. Instead of the 15-mm. tubing,
which had formerly been used, 25-mm. tubing of the same thickness was
therefore substituted, and additional cross-braces were added, as will be
seen from the photographs, and from the scale drawings in Plates 52, 53 and
54, which show the aerodrome as it was when completed. The numerals
attached to these drawings refer to the detail drawings shown in later plates.
Page 305
PL. 49. GUY-WIRE SYSTEM, JULY 10, 1902 ◊
Page 306
PL. 50. GUY-WIRE SYSTEM, JULY 10, 1902 ◊
Page 307
PL. 51. GUY-WIRE SYSTEM, JULY 10, 1902 ◊
Page 308
PL. 52. SCALE DRAWING OF AERODROME
A, END ELEVATION ◊ lgr
A, END ELEVATION ◊ lgr
Page 309
PL. 53. SCALE DRAWING OF
AERODROME A, SIDE
ELEVATION ◊ lgr
AERODROME A, SIDE
ELEVATION ◊ lgr
Page 310
PL. 54. SCALE DRAWING OF AERODROME A, PLAN ◊ lgr
In order to secure the proper adjustment of the guy-wires, not only of the
frame but of many other parts, notably the wings, propellers and rudder, it
was necessary to use a large number of turn-buckles. As almost every wire
[p171] required at least one, and in some cases two turn-buckles, the weight
represented by this single item rapidly became so formidable as to require
serious attention. In the construction of the models, it had been necessary to
employ some special turn-buckles in connecting the guy-wires of the wings
to their guy-posts in order to secure the minute adjustment of the wires
necessary to prevent the wings from being warped and distorted by unequal
and improper adjustment. These turn-buckles had been made in the
In order to secure the proper adjustment of the guy-wires, not only of the
frame but of many other parts, notably the wings, propellers and rudder, it
was necessary to use a large number of turn-buckles. As almost every wire
[p171] required at least one, and in some cases two turn-buckles, the weight
represented by this single item rapidly became so formidable as to require
serious attention. In the construction of the models, it had been necessary to
employ some special turn-buckles in connecting the guy-wires of the wings
to their guy-posts in order to secure the minute adjustment of the wires
necessary to prevent the wings from being warped and distorted by unequal
and improper adjustment. These turn-buckles had been made in the
Page 311
Institution shops, as the very lightest ones which could be secured in the
market were from ten to twenty times as heavy as it was necessary for them
to be to provide ample strength. In the construction of the large aerodrome,
however, the large number required, and the desire to complete the machine
at the earliest moment, made it advisable to procure the turn-buckles, if
possible, from outside sources, and a very careful search was accordingly
made among the various dealers. After much delay some bronze turn-
buckles were secured which were very much stronger for their weight than
any others on the market, but upon testing them it was found that while they
weighed 45 grammes, their average breaking strength was only 593 pounds.
Previous experience had shown that turn-buckles which would not break
under a less load than 750 pounds could certainly be made to weigh not
more than 18 grammes. As even at this time it was realized that at least 100
turn-buckles would be necessary for the entire machine, the excess weight
which the heavy turn-buckles would add was felt to be absolutely
prohibitory, and the construction of steel turn-buckles was immediately
begun in the Institution shops. These turn-buckles were at first made in
several sizes, and while some few were at first made “double ended,” most
of them were threaded at only one end, the other end being provided with a
swivel-hook, or eye. They were at first made of mild steel, the swivel-
hooks, in fact, being made of wire nails in order to utilize the head of the
nail as a shoulder without the expense of machining rod steel of a size large
enough to form the shoulder. It was found, however, that the weak point of
this type of turn-buckle was the swivel end, and most of those which were
then on hand were made double ended by removing the hook, tapping a
left-hand thread into this end of the shank, and fitting a threaded eye-socket
in it. The guy-wires themselves were attached to the eyes of the turn-
buckles and to the fittings on the frame by twisting loops at the ends of the
wires, and although the very greatest difference in the strength of a
completed guy-wire may result from the way in which the loops are twisted,
yet, after much training, the workmen were taught to twist these very
uniformly, following the plan which can be best understood by an
inspection of the drawings in Plate 55 which show the loops more clearly
market were from ten to twenty times as heavy as it was necessary for them
to be to provide ample strength. In the construction of the large aerodrome,
however, the large number required, and the desire to complete the machine
at the earliest moment, made it advisable to procure the turn-buckles, if
possible, from outside sources, and a very careful search was accordingly
made among the various dealers. After much delay some bronze turn-
buckles were secured which were very much stronger for their weight than
any others on the market, but upon testing them it was found that while they
weighed 45 grammes, their average breaking strength was only 593 pounds.
Previous experience had shown that turn-buckles which would not break
under a less load than 750 pounds could certainly be made to weigh not
more than 18 grammes. As even at this time it was realized that at least 100
turn-buckles would be necessary for the entire machine, the excess weight
which the heavy turn-buckles would add was felt to be absolutely
prohibitory, and the construction of steel turn-buckles was immediately
begun in the Institution shops. These turn-buckles were at first made in
several sizes, and while some few were at first made “double ended,” most
of them were threaded at only one end, the other end being provided with a
swivel-hook, or eye. They were at first made of mild steel, the swivel-
hooks, in fact, being made of wire nails in order to utilize the head of the
nail as a shoulder without the expense of machining rod steel of a size large
enough to form the shoulder. It was found, however, that the weak point of
this type of turn-buckle was the swivel end, and most of those which were
then on hand were made double ended by removing the hook, tapping a
left-hand thread into this end of the shank, and fitting a threaded eye-socket
in it. The guy-wires themselves were attached to the eyes of the turn-
buckles and to the fittings on the frame by twisting loops at the ends of the
wires, and although the very greatest difference in the strength of a
completed guy-wire may result from the way in which the loops are twisted,
yet, after much training, the workmen were taught to twist these very
uniformly, following the plan which can be best understood by an
inspection of the drawings in Plate 55 which show the loops more clearly
Page 312
than they can be described. After the loops had been properly twisted, soft
solder was run all through the twist in order to unite firmly the twists of the
wire. Although special grades of wire were found which showed very high
tensile strength when the wire was [p172] tested without having loops formed
in its ends, yet it appeared that the twisting of these high-grade wires so
seriously affected them that in the case of guy-wires with loops at the ends,
better final results could be obtained by using softer grades of steel. The
wire which was actually found best, after much experiment, was a good
grade of Bessemer steel of a medium hardness, which had been “coppered”
to prevent rusting. However, even with the softer grades of steel wire, it was
found that there were sometimes hard spots in the wire which revealed
themselves only upon test, and that when a hard spot occurred in the twisted
portion where the loop was formed, the final strength of the completed guy-
wire was sometimes only twenty-five per cent of what it should be. The
precaution was then taken to subject each of the completed guys to a test
strain at least twenty-five per cent greater than it was calculated the wire
would have to stand in actual use, so that no accident from defective wires
would be likely to occur.
Later on, however, much trouble was caused by the loops in the ends of
some of the guy-wires slipping, owing to the giving way of the solder
which had been run through the joint, the amount of slipping, while small,
being sufficient to alter completely the relative stresses on the various
wires, thus causing distortion of the framework itself. In order to avoid this
difficulty a new method was devised of attaching the guy-wires to the turn-
buckles and to the fittings by which they were carried to the frame. This
method consisted in threading the ends of the guy-wires so that they could
be inserted directly in the threaded ends of the turn-buckles. The wires
when connected in this way to the turn-buckles showed absolutely no slip,
and the entire system gained greatly in strength thereby. The only
disadvantage which was found in this new method of attaching the guy-
wires to their fittings, was that if the wire was bent very close to the fitting,
it would break in the screw thread very easily. But since most of the guy-
wires when once attached to the machine are always tight, and in fact, under
solder was run all through the twist in order to unite firmly the twists of the
wire. Although special grades of wire were found which showed very high
tensile strength when the wire was [p172] tested without having loops formed
in its ends, yet it appeared that the twisting of these high-grade wires so
seriously affected them that in the case of guy-wires with loops at the ends,
better final results could be obtained by using softer grades of steel. The
wire which was actually found best, after much experiment, was a good
grade of Bessemer steel of a medium hardness, which had been “coppered”
to prevent rusting. However, even with the softer grades of steel wire, it was
found that there were sometimes hard spots in the wire which revealed
themselves only upon test, and that when a hard spot occurred in the twisted
portion where the loop was formed, the final strength of the completed guy-
wire was sometimes only twenty-five per cent of what it should be. The
precaution was then taken to subject each of the completed guys to a test
strain at least twenty-five per cent greater than it was calculated the wire
would have to stand in actual use, so that no accident from defective wires
would be likely to occur.
Later on, however, much trouble was caused by the loops in the ends of
some of the guy-wires slipping, owing to the giving way of the solder
which had been run through the joint, the amount of slipping, while small,
being sufficient to alter completely the relative stresses on the various
wires, thus causing distortion of the framework itself. In order to avoid this
difficulty a new method was devised of attaching the guy-wires to the turn-
buckles and to the fittings by which they were carried to the frame. This
method consisted in threading the ends of the guy-wires so that they could
be inserted directly in the threaded ends of the turn-buckles. The wires
when connected in this way to the turn-buckles showed absolutely no slip,
and the entire system gained greatly in strength thereby. The only
disadvantage which was found in this new method of attaching the guy-
wires to their fittings, was that if the wire was bent very close to the fitting,
it would break in the screw thread very easily. But since most of the guy-
wires when once attached to the machine are always tight, and in fact, under
Page 313
more or less strain, there was in most cases no likelihood of the wires being
endangered by being bent close to the fittings. Since the screw threads,
which it was necessary to adopt in this new plan of connecting the guy-
wires, had to be very much finer than the threads which had been used in
the turn-buckles previously constructed, it was necessary to make new turn-
buckles, the others being too thin to permit of their being bored out, bushed
and re-threaded. The new turn-buckles were made of a much higher grade
of steel, and probably represent very nearly the maximum of strength for
the minimum of weight possible without the use of some of the very much
higher-grade steels which have recently come on the market, but which are
exceedingly expensive to work. By means of this improved plan of
attaching the wires,42 it [p173] was found possible to gain practically fifty per
cent in the strength of the entire system of guy-wires used on the frame.
Many small changes were from time to time made in the various small
fittings by which the guy-wires were attached to the frame, nearly all of
these fittings having been originally made of a very mild grade of steel
owing to the fact that it was so very much easier to work. At the time these
fittings were made it was constantly expected that a trial of the aerodrome
would be possible very soon, and it seemed necessary to expedite the work
as much as possible and avoid the delay involved in using grades of steel
that would have been materially harder to work. As is always the case in
work of this kind, retrospect shows many instances where what was
supposed to be a short cut to results actually proved to be the longest path,
but the work as a whole was remarkably free from imperfect parts which
necessitated reconstruction.
In the construction of the frames of the models it had been customary to
fit the tubing accurately at the joints and to join it permanently together by
brazing, as this was not only the lightest form of joint that could be made,
but also the most expeditious method consistent with securing a strength of
the joint comparable with that of the tubing itself. The construction of the
frame by this method of brazing the joints together permanently, offered,
however, several serious drawbacks: among them, that when a tube got
injured it was a considerable task to replace it, while the brazing of the new
endangered by being bent close to the fittings. Since the screw threads,
which it was necessary to adopt in this new plan of connecting the guy-
wires, had to be very much finer than the threads which had been used in
the turn-buckles previously constructed, it was necessary to make new turn-
buckles, the others being too thin to permit of their being bored out, bushed
and re-threaded. The new turn-buckles were made of a much higher grade
of steel, and probably represent very nearly the maximum of strength for
the minimum of weight possible without the use of some of the very much
higher-grade steels which have recently come on the market, but which are
exceedingly expensive to work. By means of this improved plan of
attaching the wires,42 it [p173] was found possible to gain practically fifty per
cent in the strength of the entire system of guy-wires used on the frame.
Many small changes were from time to time made in the various small
fittings by which the guy-wires were attached to the frame, nearly all of
these fittings having been originally made of a very mild grade of steel
owing to the fact that it was so very much easier to work. At the time these
fittings were made it was constantly expected that a trial of the aerodrome
would be possible very soon, and it seemed necessary to expedite the work
as much as possible and avoid the delay involved in using grades of steel
that would have been materially harder to work. As is always the case in
work of this kind, retrospect shows many instances where what was
supposed to be a short cut to results actually proved to be the longest path,
but the work as a whole was remarkably free from imperfect parts which
necessitated reconstruction.
In the construction of the frames of the models it had been customary to
fit the tubing accurately at the joints and to join it permanently together by
brazing, as this was not only the lightest form of joint that could be made,
but also the most expeditious method consistent with securing a strength of
the joint comparable with that of the tubing itself. The construction of the
frame by this method of brazing the joints together permanently, offered,
however, several serious drawbacks: among them, that when a tube got
injured it was a considerable task to replace it, while the brazing of the new
Page 314
tube in place required extreme care to prevent the frame from being warped
when completed, as the tube became longer while very hot and contracted
after the joint had set. Furthermore, the great heat required destroyed to a
considerable degree the desirable qualities due to the tube being “cold
drawn,” a reduction of strength of something like 25 per cent being almost
inevitable, even when the brazing was most carefully done. It was,
therefore, decided that in the construction of the large machine all of the
main joints should be made by a system of “thimbles,” and it was planned
at first to make these thimbles by brazing short pieces of steel tubing into
the proper shapes and angles so that they would accurately fit the tubes
which were to be joined. The construction of the thimbles in this manner,
however, seemed to involve an excessive amount of work; and, as it was
found that very thin castings of aluminum-bronze could be obtained, which
would show a tensile strength very nearly as great as steel, it was decided to
make up patterns for the thimbles and cast them of aluminum-bronze.
The aluminum-bronze castings were obtained and properly machined to
fit the tubes, but when it was attempted to “tin” the interior walls of the
thimbles it was found that the solder could not be made to stick to the
bronze. As a considerable amount of work had been expended on the
machine work of these thimbles much time and effort was spent in
attempting to devise “fluxes” [p174] and solders which could be made to
work with the aluminum-bronze, but the final result was that the aluminum-
bronze thimbles had to be abandoned. They were replaced by similar
castings of gun-metal of a slightly heavier section, which at the time were
thought to be very suitable for the purpose.
But, in finally assembling the frame after the changes described above
had been made, steel thimbles, built up of short pieces of tubing, as had
originally been planned, were substituted for the gun-metal thimbles. This
change was made not only because of the great increase in strength, but
more particularly because many of the gun-metal fittings had been
imperfectly constructed, so that it was extremely difficult to align the frame.
The steel thimbles, which were made in the Institution shops proved
thoroughly satisfactory and gave no trouble of any kind. Many of these
when completed, as the tube became longer while very hot and contracted
after the joint had set. Furthermore, the great heat required destroyed to a
considerable degree the desirable qualities due to the tube being “cold
drawn,” a reduction of strength of something like 25 per cent being almost
inevitable, even when the brazing was most carefully done. It was,
therefore, decided that in the construction of the large machine all of the
main joints should be made by a system of “thimbles,” and it was planned
at first to make these thimbles by brazing short pieces of steel tubing into
the proper shapes and angles so that they would accurately fit the tubes
which were to be joined. The construction of the thimbles in this manner,
however, seemed to involve an excessive amount of work; and, as it was
found that very thin castings of aluminum-bronze could be obtained, which
would show a tensile strength very nearly as great as steel, it was decided to
make up patterns for the thimbles and cast them of aluminum-bronze.
The aluminum-bronze castings were obtained and properly machined to
fit the tubes, but when it was attempted to “tin” the interior walls of the
thimbles it was found that the solder could not be made to stick to the
bronze. As a considerable amount of work had been expended on the
machine work of these thimbles much time and effort was spent in
attempting to devise “fluxes” [p174] and solders which could be made to
work with the aluminum-bronze, but the final result was that the aluminum-
bronze thimbles had to be abandoned. They were replaced by similar
castings of gun-metal of a slightly heavier section, which at the time were
thought to be very suitable for the purpose.
But, in finally assembling the frame after the changes described above
had been made, steel thimbles, built up of short pieces of tubing, as had
originally been planned, were substituted for the gun-metal thimbles. This
change was made not only because of the great increase in strength, but
more particularly because many of the gun-metal fittings had been
imperfectly constructed, so that it was extremely difficult to align the frame.
The steel thimbles, which were made in the Institution shops proved
thoroughly satisfactory and gave no trouble of any kind. Many of these
Page 315
thimbles and the method of attaching the guy-wire fittings to them are
shown in Plates 56 and 57, as well as in Plate 55.
T RANSVERSE F RAME
It will be recalled from the description of the models Nos. 5 and 6, in Part
I, that the position of the line of thrust, with respect to the positions of the
center of pressure and center of gravity in the vertical plane was,
theoretically, very much better in No. 6 than in No. 5. In designing the large
aerodrome, it was desired to reproduce as nearly as possible the relative
position of the line of thrust with reference to the center of pressure and
center of gravity which existed in No. 6, but for constructional reasons it
was found impossible to do so. In fact it appeared that without seriously
complicating the construction of the frame it was impossible to raise the
line of thrust with respect to the center of gravity materially higher than it
was in No. 5. In No. 6 the line of thrust was 12 centimetres above the
midrod, this being effected by placing the engines some distance from the
boiler, and at the extreme ends of the transverse frame where they were
connected directly to the propellers. In the case of the steam engine the
weight of the engine proper is a relatively small portion of the entire weight
of the power plant, and it is, therefore, possible to put the engine almost
anywhere without materially affecting the center of gravity. But where a gas
engine is used the engine itself constitutes the greater part of the weight of
the power plant, and any raising of the engine, therefore, materially raises
the center of gravity of the whole machine. The line of thrust in the large
aerodrome was, therefore, practically in the plane of the main frame, and
consequently very little higher than the center of gravity.
shown in Plates 56 and 57, as well as in Plate 55.
T RANSVERSE F RAME
It will be recalled from the description of the models Nos. 5 and 6, in Part
I, that the position of the line of thrust, with respect to the positions of the
center of pressure and center of gravity in the vertical plane was,
theoretically, very much better in No. 6 than in No. 5. In designing the large
aerodrome, it was desired to reproduce as nearly as possible the relative
position of the line of thrust with reference to the center of pressure and
center of gravity which existed in No. 6, but for constructional reasons it
was found impossible to do so. In fact it appeared that without seriously
complicating the construction of the frame it was impossible to raise the
line of thrust with respect to the center of gravity materially higher than it
was in No. 5. In No. 6 the line of thrust was 12 centimetres above the
midrod, this being effected by placing the engines some distance from the
boiler, and at the extreme ends of the transverse frame where they were
connected directly to the propellers. In the case of the steam engine the
weight of the engine proper is a relatively small portion of the entire weight
of the power plant, and it is, therefore, possible to put the engine almost
anywhere without materially affecting the center of gravity. But where a gas
engine is used the engine itself constitutes the greater part of the weight of
the power plant, and any raising of the engine, therefore, materially raises
the center of gravity of the whole machine. The line of thrust in the large
aerodrome was, therefore, practically in the plane of the main frame, and
consequently very little higher than the center of gravity.
Page 316
PL. 55. FRAME FITTINGS AND GUY-WIRE ATTACHMENTS, ETC. ◊ lgr
Page 317
PL. 56. FRAME FITTINGS AND GUY-WIRE ATTACHMENTS, ETC. ◊ lgr
Page 318
PL. 57. FRAME FITTINGS AND GUY-WIRE ATTACHMENTS, ETC. ◊ lgr
Page 319
The use of one engine to drive two propellers mounted at opposite ends
of the transverse frame, and in a direction perpendicular to the crank shaft
of the engine, necessitates the use of a pair of bevel gears between each of
the propeller shafts and the shafts by which the power is conveyed to them
from [p175] the engine shaft. Since the efficient transmission of power
through bevel gears requires that they be very accurately placed with
reference to each other, and maintained very accurately in this position
while they are at work, it was necessary to make the transverse frame very
rigid, especially at its extreme ends. This was accomplished by the use of
what were called “propeller-shaft bed plates.” They are designated by the
numeral 27 in Plate 54, and are shown in detail in Plate 58 as of a very deep
I-beam section, having very narrow flanges top and bottom, the web of the
I-beam furnishing the strength in a vertical direction, while sufficient
stiffness laterally was obtained from the flanges, assisted by the brace tubes,
which acted as struts between the bed plates and the main tubes of the
transverse frame. These struts, while very light, added enormously not only
to the lateral stiffness of the propeller bed plates, but furnished for a
minimum weight a maximum prevention against twisting of the plates. The
propeller-shaft bed plates were originally planned to be made of sheet metal
with the flanges brazed to the web. But at the time that they were
constructed the pressure of the work was so great in the Institution shops
that it was found necessary to have some of the work done outside, and the
parties who undertook the construction of these bed plates were unwilling
to attempt to braze them up, and accordingly worked them from steel
forgings made for the purpose. The expense of this plan of construction
proved large and unnecessary, as both previous and later experience proved
that it was not only practicable to braze up bed plates more complicated in
their design than these, but that equal strength for equal weight could thus
be obtained for less than one-quarter the cost of constructing them from
solid forgings. Furthermore, where such parts are made from the solid,
changes which later tests prove advisable can frequently not be carried out
without very serious cost and delay, while with the bed plates formed by
brazing less hesitancy is felt in removing parts which are brazed thereto and
of the transverse frame, and in a direction perpendicular to the crank shaft
of the engine, necessitates the use of a pair of bevel gears between each of
the propeller shafts and the shafts by which the power is conveyed to them
from [p175] the engine shaft. Since the efficient transmission of power
through bevel gears requires that they be very accurately placed with
reference to each other, and maintained very accurately in this position
while they are at work, it was necessary to make the transverse frame very
rigid, especially at its extreme ends. This was accomplished by the use of
what were called “propeller-shaft bed plates.” They are designated by the
numeral 27 in Plate 54, and are shown in detail in Plate 58 as of a very deep
I-beam section, having very narrow flanges top and bottom, the web of the
I-beam furnishing the strength in a vertical direction, while sufficient
stiffness laterally was obtained from the flanges, assisted by the brace tubes,
which acted as struts between the bed plates and the main tubes of the
transverse frame. These struts, while very light, added enormously not only
to the lateral stiffness of the propeller bed plates, but furnished for a
minimum weight a maximum prevention against twisting of the plates. The
propeller-shaft bed plates were originally planned to be made of sheet metal
with the flanges brazed to the web. But at the time that they were
constructed the pressure of the work was so great in the Institution shops
that it was found necessary to have some of the work done outside, and the
parties who undertook the construction of these bed plates were unwilling
to attempt to braze them up, and accordingly worked them from steel
forgings made for the purpose. The expense of this plan of construction
proved large and unnecessary, as both previous and later experience proved
that it was not only practicable to braze up bed plates more complicated in
their design than these, but that equal strength for equal weight could thus
be obtained for less than one-quarter the cost of constructing them from
solid forgings. Furthermore, where such parts are made from the solid,
changes which later tests prove advisable can frequently not be carried out
without very serious cost and delay, while with the bed plates formed by
brazing less hesitancy is felt in removing parts which are brazed thereto and
Page 320
substituting new parts, or even discarding the bed plates altogether and
substituting new ones. Particular emphasis is laid on this point for the
reason that much expense and delay would have been avoided had these
very expensive propeller-shaft bed plates been discarded as early as 1901
and replaced by others which would have permitted a considerable
strengthening of the ball-bearings, which, while strong enough to stand
even more power than they were originally designed for, were far too weak
to be safe when working under the greatly increased stress due to the very
much higher engine power which was later used. Instead of discarding these
bed plates then for new ones, they were strengthened by brazing to them
crescent-shaped pieces, as shown in the drawings and photographs. This
strengthening was made necessary by the larger hole cut in the bed plates
for the larger bevel gears. The bed plates for the engine, which are later
described, besides other bed plates which were made for other purposes,
were all [p176] formed by the use of sheet metal and tubing properly brazed
together, and none of them ever gave any trouble.
In the early photographs of the aerodrome frame, especially that of
January 31, 1900, Plate 45, it will be noted that the two transmission shafts,
which extend from the propeller-shaft bed plates towards the center, are not
in line, the port transmission shaft being at the center of the transverse
frame, while the starboard shaft is three inches to one side. This
arrangement was necessary in order to connect the shafts to the rotary
cylinder engine which was being constructed under contract, and which was
almost momentarily expected for more than a year after its original promise
of delivery on February 28, 1899. Later, when this engine was finally found
to be a failure, and the writer constructed the engine in the Institution shops,
the starboard transmission shaft was moved over to the center line and the
crank shaft of the engine, which was carried through on the center line of
the transverse frame, was then connected directly to the inner ends of the
transmission shafts.
These shafts, as well as the propeller shafts, were originally constructed
1
of steel tubing 1.5 inches in diameter and 16 of an inch thick, but on account
substituting new ones. Particular emphasis is laid on this point for the
reason that much expense and delay would have been avoided had these
very expensive propeller-shaft bed plates been discarded as early as 1901
and replaced by others which would have permitted a considerable
strengthening of the ball-bearings, which, while strong enough to stand
even more power than they were originally designed for, were far too weak
to be safe when working under the greatly increased stress due to the very
much higher engine power which was later used. Instead of discarding these
bed plates then for new ones, they were strengthened by brazing to them
crescent-shaped pieces, as shown in the drawings and photographs. This
strengthening was made necessary by the larger hole cut in the bed plates
for the larger bevel gears. The bed plates for the engine, which are later
described, besides other bed plates which were made for other purposes,
were all [p176] formed by the use of sheet metal and tubing properly brazed
together, and none of them ever gave any trouble.
In the early photographs of the aerodrome frame, especially that of
January 31, 1900, Plate 45, it will be noted that the two transmission shafts,
which extend from the propeller-shaft bed plates towards the center, are not
in line, the port transmission shaft being at the center of the transverse
frame, while the starboard shaft is three inches to one side. This
arrangement was necessary in order to connect the shafts to the rotary
cylinder engine which was being constructed under contract, and which was
almost momentarily expected for more than a year after its original promise
of delivery on February 28, 1899. Later, when this engine was finally found
to be a failure, and the writer constructed the engine in the Institution shops,
the starboard transmission shaft was moved over to the center line and the
crank shaft of the engine, which was carried through on the center line of
the transverse frame, was then connected directly to the inner ends of the
transmission shafts.
These shafts, as well as the propeller shafts, were originally constructed
1
of steel tubing 1.5 inches in diameter and 16 of an inch thick, but on account
Page 321
of the increased power of the large engine it was found necessary to
increase the thickness of the shafts to 18 of an inch. Difficulty was also found
with the tubing of which the shafts were made. This, though not exactly
straight when received from the factory, could be pretty accurately
straightened in the lathe by exercising proper care, but the moment any real
strain was put upon it in the transmission of power, it again went out of
shape and caused serious damage to the bearings by whirling, buckling, and
so forth. As the skin of the tubing is really the strongest part, owing to the
cold-drawing process to which it has been subjected, great care was taken to
secure shafts which were sufficiently straight for use without machining,
but it was finally found impossible to rely on the unmachined shafts, and all
the later shafts for the aerodrome were made by getting tubing a sixty-
fourth of an inch thicker than was calculated to be necessary and turning off
this extra metal in a lathe.
increase the thickness of the shafts to 18 of an inch. Difficulty was also found
with the tubing of which the shafts were made. This, though not exactly
straight when received from the factory, could be pretty accurately
straightened in the lathe by exercising proper care, but the moment any real
strain was put upon it in the transmission of power, it again went out of
shape and caused serious damage to the bearings by whirling, buckling, and
so forth. As the skin of the tubing is really the strongest part, owing to the
cold-drawing process to which it has been subjected, great care was taken to
secure shafts which were sufficiently straight for use without machining,
but it was finally found impossible to rely on the unmachined shafts, and all
the later shafts for the aerodrome were made by getting tubing a sixty-
fourth of an inch thicker than was calculated to be necessary and turning off
this extra metal in a lathe.
Page 322
PL. 58. BEDPLATE, GEARS, ETC. ◊ lgr
Page 323
Suitable flanges and collars were brazed to the propeller shafts; but, for
convenience in assembling, the flanges by which the main transmission
shafts were connected to the crank shaft of the engine were at first fastened
to the shafts by screw-threads, the threads being in the proper direction to
cause the flanges to jam against the shoulders of the shafts when the engine
turned in its normal direction. This method of fastening, however, caused
serious trouble, owing to the flanges jamming so tight that it became
impossible to unscrew them after they had once been used in driving the
propellers. The usual provisions of keys and key-ways adopted in general
engineering practice, where solid shafts are employed, were, of course, out
of the question, since the shaft would have to be greatly increased in
thickness throughout its entire length [p177] merely to provide the extra
metal at the small place in which the key-ways were formed. Taper pins
either sheared off or very soon stretched the holes so badly as to leave the
parts loose, and were otherwise very unsatisfactory. The method finally
adopted, which proved very successful, was that of forming integral with
the couplings shallow internal tongues and grooves which fitted
corresponding tongues and grooves either in the exterior surface of the
shafts or in collars brazed to them at the proper point. The form of flange
coupling, in which bolts draw the two flanges tightly together, was also a
source of considerable trouble and delay, which was finally overcome by
forming shallow tongues and grooves in the faces of the flanges, the
tongues taking up the torsion and relieving the bolts which held the flanges
together of all strain except one of slight tension. The same difficulties
experienced in mounting the couplings on the shafts were met with in
connection with the gears, both on the propeller and transmission shafts,
and were finally obviated in a manner similar to that described above.
The bevel gears originally constructed for transmitting the power from
the transmission shafts to the propeller shafts, were made of case-hardened
steel and were eight-pitch, twenty-five teeth, with three-quarter inch width
of face. The gears were very accurately planed to give as perfect a form of
tooth as possible, in order to avoid loss of power in transmission, and
although the manufacturer who cut the teeth on them asserted at the time
convenience in assembling, the flanges by which the main transmission
shafts were connected to the crank shaft of the engine were at first fastened
to the shafts by screw-threads, the threads being in the proper direction to
cause the flanges to jam against the shoulders of the shafts when the engine
turned in its normal direction. This method of fastening, however, caused
serious trouble, owing to the flanges jamming so tight that it became
impossible to unscrew them after they had once been used in driving the
propellers. The usual provisions of keys and key-ways adopted in general
engineering practice, where solid shafts are employed, were, of course, out
of the question, since the shaft would have to be greatly increased in
thickness throughout its entire length [p177] merely to provide the extra
metal at the small place in which the key-ways were formed. Taper pins
either sheared off or very soon stretched the holes so badly as to leave the
parts loose, and were otherwise very unsatisfactory. The method finally
adopted, which proved very successful, was that of forming integral with
the couplings shallow internal tongues and grooves which fitted
corresponding tongues and grooves either in the exterior surface of the
shafts or in collars brazed to them at the proper point. The form of flange
coupling, in which bolts draw the two flanges tightly together, was also a
source of considerable trouble and delay, which was finally overcome by
forming shallow tongues and grooves in the faces of the flanges, the
tongues taking up the torsion and relieving the bolts which held the flanges
together of all strain except one of slight tension. The same difficulties
experienced in mounting the couplings on the shafts were met with in
connection with the gears, both on the propeller and transmission shafts,
and were finally obviated in a manner similar to that described above.
The bevel gears originally constructed for transmitting the power from
the transmission shafts to the propeller shafts, were made of case-hardened
steel and were eight-pitch, twenty-five teeth, with three-quarter inch width
of face. The gears were very accurately planed to give as perfect a form of
tooth as possible, in order to avoid loss of power in transmission, and
although the manufacturer who cut the teeth on them asserted at the time
Page 324
they were made that they would not be capable of transmitting more than
five horse-power, yet they actually did transmit considerably more than
twelve horse-power on each set; but they were not strong enough to
transmit the full power of the large engine which was finally used. The
gears that were finally used were similarly constructed of mild steel which
1
was case hardened 64 of an inch deep after they were finished, there being
thirty-one teeth in the gear on the transmission shaft and forty teeth in the
one on the propeller shaft, the teeth being eight-pitch, three-quarters of an
inch face. These light gears proved amply strong, and several times stood
the strain which they accidentally received when one of the propellers broke
while the engine was under full power, and thus threw the entire fifty horse-
power over on the other propeller, which was consequently driven at a
greatly increased speed.
Plain bronze bearings had been used throughout on the model
aerodromes, but in the construction of the large aerodrome ball-bearings
were used on all of the propeller and transmission shafts, not only on
account of the decreased loss through friction, but also because ball-
bearings can be built much lighter than solid bronze ones, and, furthermore,
do not present such great difficulties in lubrication. However, owing to the
limited size which it was possible to secure for these bearings, because of
their having been originally designed for only twenty-four horse-power, and
without any margin for a later increase of the [p178] space in which they had
to be applied, they were never really large enough for the work they had to
do when transmitting the full power of the large engine. They gave
continual trouble, and were the source of delay which, while it cannot be
accurately measured, since there were often other causes, yet might be
conservatively estimated at not less than three or four months. Such a delay,
when reckoned in retrospect, can easily be seen to have caused an expense
which would have sufficed for almost any change in the bearings, bed
plates, etc., had the change been made immediately after the bearings were
found to give trouble. With the better steel which it is now possible to
obtain for the races of the bearings, and with the high-grade balls now
five horse-power, yet they actually did transmit considerably more than
twelve horse-power on each set; but they were not strong enough to
transmit the full power of the large engine which was finally used. The
gears that were finally used were similarly constructed of mild steel which
1
was case hardened 64 of an inch deep after they were finished, there being
thirty-one teeth in the gear on the transmission shaft and forty teeth in the
one on the propeller shaft, the teeth being eight-pitch, three-quarters of an
inch face. These light gears proved amply strong, and several times stood
the strain which they accidentally received when one of the propellers broke
while the engine was under full power, and thus threw the entire fifty horse-
power over on the other propeller, which was consequently driven at a
greatly increased speed.
Plain bronze bearings had been used throughout on the model
aerodromes, but in the construction of the large aerodrome ball-bearings
were used on all of the propeller and transmission shafts, not only on
account of the decreased loss through friction, but also because ball-
bearings can be built much lighter than solid bronze ones, and, furthermore,
do not present such great difficulties in lubrication. However, owing to the
limited size which it was possible to secure for these bearings, because of
their having been originally designed for only twenty-four horse-power, and
without any margin for a later increase of the [p178] space in which they had
to be applied, they were never really large enough for the work they had to
do when transmitting the full power of the large engine. They gave
continual trouble, and were the source of delay which, while it cannot be
accurately measured, since there were often other causes, yet might be
conservatively estimated at not less than three or four months. Such a delay,
when reckoned in retrospect, can easily be seen to have caused an expense
which would have sufficed for almost any change in the bearings, bed
plates, etc., had the change been made immediately after the bearings were
found to give trouble. With the better steel which it is now possible to
obtain for the races of the bearings, and with the high-grade balls now
Page 325
obtainable, the bearings could be readily replaced without changing any
other parts and still be amply strong for the work.
P ROPELLERS
Both the tests on the whirling-table and the actual results with the models
had shown that propellers which were true helices formed out of wood were
rather more efficient than those constructed by the use of a hub in which
were inserted wooden arms, forming a framing over which cloth was tightly
drawn. But the very great difference in the cost of construction and the
facility with which the latter type could be repaired in case of damage—the
wooden ones were practically of no use if once they were much injured-—
made it seem advisable to construct all the propellers for the large
aerodrome in the manner just explained. Several pair of small propellers
had been built on this plan, some as early as 1895, and one very important
advantage had been found to be possessed by this type besides cheapness
and facility of repair. Wooden propellers of even so small a diameter as one
metre had been found to suffer a quite appreciable bending of the blades,
due to the thrust produced by them, even though the blades had been made
of considerable thickness. In planning a propeller 2.5 metres in diameter for
the large aerodrome it was seen that in order to make the blade sufficiently
strong to withstand its own thrust it would be necessary to make it
inordinately thick, which, of course, would mean a considerable increase in
weight. In fact, it was seen that the weight of the larger propellers would
increase practically as the cube of the diameter; which, for the 2.5-metre
propeller, would involve a weight of something over fifteen times the
weight of those one metre in diameter. The other type, which for
convenience we will call “canvas covered,” permitted the bending moment
produced on the blade by the thrust to be taken up by guy-wires running
from the corners of the blades to a central post projecting from the hub of
the propeller, and it was found that in this way a considerable saving in
weight could be effected. [p179]
In November, 1897, in order to obtain by actual test some data on
propellers, such as it was planned to use on the large aerodrome in case it
other parts and still be amply strong for the work.
P ROPELLERS
Both the tests on the whirling-table and the actual results with the models
had shown that propellers which were true helices formed out of wood were
rather more efficient than those constructed by the use of a hub in which
were inserted wooden arms, forming a framing over which cloth was tightly
drawn. But the very great difference in the cost of construction and the
facility with which the latter type could be repaired in case of damage—the
wooden ones were practically of no use if once they were much injured-—
made it seem advisable to construct all the propellers for the large
aerodrome in the manner just explained. Several pair of small propellers
had been built on this plan, some as early as 1895, and one very important
advantage had been found to be possessed by this type besides cheapness
and facility of repair. Wooden propellers of even so small a diameter as one
metre had been found to suffer a quite appreciable bending of the blades,
due to the thrust produced by them, even though the blades had been made
of considerable thickness. In planning a propeller 2.5 metres in diameter for
the large aerodrome it was seen that in order to make the blade sufficiently
strong to withstand its own thrust it would be necessary to make it
inordinately thick, which, of course, would mean a considerable increase in
weight. In fact, it was seen that the weight of the larger propellers would
increase practically as the cube of the diameter; which, for the 2.5-metre
propeller, would involve a weight of something over fifteen times the
weight of those one metre in diameter. The other type, which for
convenience we will call “canvas covered,” permitted the bending moment
produced on the blade by the thrust to be taken up by guy-wires running
from the corners of the blades to a central post projecting from the hub of
the propeller, and it was found that in this way a considerable saving in
weight could be effected. [p179]
In November, 1897, in order to obtain by actual test some data on
propellers, such as it was planned to use on the large aerodrome in case it
Page 326
was later built, it was decided to construct one propeller 2.5 metres in
diameter and 1.25-pitch ratio with two blades, each covering the sector of
36 degrees on the projected circle. About this same time an engine builder,
who some years before had made some experimental model engines in the
Institution shops, proposed to construct a gasoline engine for the proposed
large aerodrome. As past experience, not only with such engines but with all
other forms of explosive motors, had not been very reassuring it was
thought best to make brake tests of one of the heavier engines which he was
at this time building, and at the same time make tests with one of these large
propellers. A first series of tests was made at several different speeds, and
then a second series was made with the engine driving the propeller at the
same speeds. The engine varied so much, however, in the power developed
at any speed that the data obtained were of little value. As it was also
desired to learn just how much thrust could be obtained from these
propellers, when driven by a given horse-power, a special hand car was
fitted up to carry the engine, which was connected to a shaft on which the
propeller was mounted. The propeller was raised above the floor of the car
and projected over the rear end of it so as to be as little disturbed as possible
by the deflection of the air currents caused by the car. This car, with the
engine and propeller, was tested on a track near Mount Holly, N. J., in
November, 1897, but the results were very unsatisfactory. In the first place,
the car with the engine mounted on it was so very heavy and offered such a
strong tractive resistance that very little speed of propulsion could be
obtained. In the second place, the engine, which was said to have furnished
over six horse-power on Prony-brake tests, evidently did not furnish
anything like this amount of power at this time. And in the third place, the
propeller was evidently far too large to permit the engine to run at the speed
at which it would develop a reasonable amount of power unless some
reduction gearing were interposed between it and the propeller. As the tests,
for various reasons, had to be made at a great distance from Washington,
and the supervision of them had to be entrusted by Mr. Langley to others,
who either did not understand or appreciate the value of obtaining accurate
data, it was found impracticable to continue them.
diameter and 1.25-pitch ratio with two blades, each covering the sector of
36 degrees on the projected circle. About this same time an engine builder,
who some years before had made some experimental model engines in the
Institution shops, proposed to construct a gasoline engine for the proposed
large aerodrome. As past experience, not only with such engines but with all
other forms of explosive motors, had not been very reassuring it was
thought best to make brake tests of one of the heavier engines which he was
at this time building, and at the same time make tests with one of these large
propellers. A first series of tests was made at several different speeds, and
then a second series was made with the engine driving the propeller at the
same speeds. The engine varied so much, however, in the power developed
at any speed that the data obtained were of little value. As it was also
desired to learn just how much thrust could be obtained from these
propellers, when driven by a given horse-power, a special hand car was
fitted up to carry the engine, which was connected to a shaft on which the
propeller was mounted. The propeller was raised above the floor of the car
and projected over the rear end of it so as to be as little disturbed as possible
by the deflection of the air currents caused by the car. This car, with the
engine and propeller, was tested on a track near Mount Holly, N. J., in
November, 1897, but the results were very unsatisfactory. In the first place,
the car with the engine mounted on it was so very heavy and offered such a
strong tractive resistance that very little speed of propulsion could be
obtained. In the second place, the engine, which was said to have furnished
over six horse-power on Prony-brake tests, evidently did not furnish
anything like this amount of power at this time. And in the third place, the
propeller was evidently far too large to permit the engine to run at the speed
at which it would develop a reasonable amount of power unless some
reduction gearing were interposed between it and the propeller. As the tests,
for various reasons, had to be made at a great distance from Washington,
and the supervision of them had to be entrusted by Mr. Langley to others,
who either did not understand or appreciate the value of obtaining accurate
data, it was found impracticable to continue them.
Page 327
The large propeller used in these tests was built without special regard to
weight, since it was expected that it would be subjected to rather rough
usage under the very sudden strains produced by the irregular working of
the gas engine. Its hub was made of brass tubing, the horns being brazed to
rings which were slid over a central tube, the rings being finally soldered to
the tube after the arms had been adjusted to the positions which would give
the blade the correct shape and dimensions. The wooden arms were 1.5
inches in [p180] diameter at the hub end, tapering to 1.25 inches at the end of
the blade. The blade was exceedingly stiff as regards pressure produced by
thrust, but it was found to be considerably strengthened and made very
much safer when guy-wires were added, in the manner explained above.
This general type of construction was adhered to in all the future propellers
for the aerodrome, though slight modifications, both as to the size of the
arms and the number and position of the cross-pieces which formed the
framing of the blade, were adopted from time to time. A pair of heavy
propellers, 2.5 metre, 1.25-pitch ratio, 36-degree blade, the hubs of which
were formed of brass castings, was, however, constructed for experimental
purposes, where weight was not an important factor.
When these propellers were designed, the calculations as to their size and
the horse-power which would be required to drive them at a certain speed
were based on the very incomplete data obtained from the various propeller
tests conducted during the preceding years. When later calculations were
made for them, on the data obtained in the more accurate tests made in the
summer of 1898, it was found that the power of the engines with which it
was proposed to equip the aerodrome would not be sufficient to drive the
propellers at anything like the speed which the former calculations had
shown would be possible; and that, therefore, either the ratio of the gearing
between the propellers and the engine would have to be changed so as to
permit the engine to run at a very much higher speed than the propellers, or
that propellers, having either less pitch or a smaller diameter, and possibly
both, would have to be substituted for these larger ones.
Since it was easier to change the propellers then to change the gearing, a
new set of propellers was designed which were of 2 metres diameter, with a
weight, since it was expected that it would be subjected to rather rough
usage under the very sudden strains produced by the irregular working of
the gas engine. Its hub was made of brass tubing, the horns being brazed to
rings which were slid over a central tube, the rings being finally soldered to
the tube after the arms had been adjusted to the positions which would give
the blade the correct shape and dimensions. The wooden arms were 1.5
inches in [p180] diameter at the hub end, tapering to 1.25 inches at the end of
the blade. The blade was exceedingly stiff as regards pressure produced by
thrust, but it was found to be considerably strengthened and made very
much safer when guy-wires were added, in the manner explained above.
This general type of construction was adhered to in all the future propellers
for the aerodrome, though slight modifications, both as to the size of the
arms and the number and position of the cross-pieces which formed the
framing of the blade, were adopted from time to time. A pair of heavy
propellers, 2.5 metre, 1.25-pitch ratio, 36-degree blade, the hubs of which
were formed of brass castings, was, however, constructed for experimental
purposes, where weight was not an important factor.
When these propellers were designed, the calculations as to their size and
the horse-power which would be required to drive them at a certain speed
were based on the very incomplete data obtained from the various propeller
tests conducted during the preceding years. When later calculations were
made for them, on the data obtained in the more accurate tests made in the
summer of 1898, it was found that the power of the engines with which it
was proposed to equip the aerodrome would not be sufficient to drive the
propellers at anything like the speed which the former calculations had
shown would be possible; and that, therefore, either the ratio of the gearing
between the propellers and the engine would have to be changed so as to
permit the engine to run at a very much higher speed than the propellers, or
that propellers, having either less pitch or a smaller diameter, and possibly
both, would have to be substituted for these larger ones.
Since it was easier to change the propellers then to change the gearing, a
new set of propellers was designed which were of 2 metres diameter, with a
Page 328
pitch ratio of unity, and with a width of blade of only 30 degrees. It was
calculated that 20 horse-power would drive these two propellers at a speed
of 640 R. P. M., when the aerodrome was flying at a speed of 35 feet per
second and the propellers were slipping about 50 per cent, this being found
to be about the speed at which the engines might be expected to develop
their maximum power. As the larger propellers having the brass hubs were
thought to be excessively heavy, the hubs weighing 10.25 pounds each, and
as any change either in size, pitch, or width of blade necessitated a new set
of patterns in case the hubs were cast, it was decided to construct the new
hubs of steel tubing. The weight was further reduced by decreasing the size
of the wooden arms to 1 14 inch in diameter at the hub, tapering to 1 inch at
the end of the blade.
After the engine builder in New York had been unable to fulfil his
contract on the engine, and it had been condemned, propeller tests were
made with the experimental engine built in the Institution shops. These tests
showed: First, that the results which might be expected from larger
propellers could be very safely predicted by extrapolation from the results
of the propeller tests of 1898; [p181] and, second, that in order to get a thrust
which would equal fifty per cent of the flying weight of the aerodrome it
would be necessary to use propellers larger than two metres in diameter
unless a very large surplus of power were provided. It was accordingly
decided to make a set of propellers intermediate between the two-metre,
unit-pitch ratio, thirty-degree blade ones, and the original ones which were
two and one-half metres, one and one-quarter-pitch ratio, thirty-six-degree
blade. A set was, therefore, designed two and one-half metres in diameter,
unit-pitch ratio, and thirty-degree width of blade, the hubs being made of
steel tubing brazed up in the same manner as the two-metre ones, and the
wooden arms of the blades being one and three-eighths inches in diameter
at the hub end, and tapering to one inch at the end of the blade.
Later, when the larger engine was actually tested in the frame, the
inability of the original transmission and propeller shafts to stand the extra
strain caused by the engine starting up very suddenly at times, together with
calculated that 20 horse-power would drive these two propellers at a speed
of 640 R. P. M., when the aerodrome was flying at a speed of 35 feet per
second and the propellers were slipping about 50 per cent, this being found
to be about the speed at which the engines might be expected to develop
their maximum power. As the larger propellers having the brass hubs were
thought to be excessively heavy, the hubs weighing 10.25 pounds each, and
as any change either in size, pitch, or width of blade necessitated a new set
of patterns in case the hubs were cast, it was decided to construct the new
hubs of steel tubing. The weight was further reduced by decreasing the size
of the wooden arms to 1 14 inch in diameter at the hub, tapering to 1 inch at
the end of the blade.
After the engine builder in New York had been unable to fulfil his
contract on the engine, and it had been condemned, propeller tests were
made with the experimental engine built in the Institution shops. These tests
showed: First, that the results which might be expected from larger
propellers could be very safely predicted by extrapolation from the results
of the propeller tests of 1898; [p181] and, second, that in order to get a thrust
which would equal fifty per cent of the flying weight of the aerodrome it
would be necessary to use propellers larger than two metres in diameter
unless a very large surplus of power were provided. It was accordingly
decided to make a set of propellers intermediate between the two-metre,
unit-pitch ratio, thirty-degree blade ones, and the original ones which were
two and one-half metres, one and one-quarter-pitch ratio, thirty-six-degree
blade. A set was, therefore, designed two and one-half metres in diameter,
unit-pitch ratio, and thirty-degree width of blade, the hubs being made of
steel tubing brazed up in the same manner as the two-metre ones, and the
wooden arms of the blades being one and three-eighths inches in diameter
at the hub end, and tapering to one inch at the end of the blade.
Later, when the larger engine was actually tested in the frame, the
inability of the original transmission and propeller shafts to stand the extra
strain caused by the engine starting up very suddenly at times, together with
Page 329
the unsatisfactoriness of the screw-thread method of fastening the gears and
couplings to the shafts made it necessary to provide new shafts, gears,
couplings, etc. It was then decided to change the ratio of gearing between
the engine and the propellers, which had been one to one, so that the engine
might run faster and, therefore, permit the use of larger propellers. For
constructional reasons the ratio chosen was thirty-one to forty, thus making
the engine run approximately one-third faster than the propellers.
In the various tests made of the engine working in the frame there were
two or three instances in which the propellers were damaged either by the
sudden starting of the engine or by their not being able to stand the strain to
which they were subjected by the power absorbed, but in every case such
breakages were found to be due to imperfections of the brazing in the joints.
While, therefore, it would have been desirable to make the propellers
somewhat heavier, yet since the total weight of the aerodrome had been
growing so very rapidly, it was felt that this need not be done, as a pair of
propellers which had stood quite severe service in shop tests might
reasonably be expected to stand the strain of actually propelling the
aerodrome through the air.
Nevertheless, when in the summer of 1903 the actual trials of the large
aerodrome were started, it was found that the very important difference
between a propeller working in a closed room and one working in the open
air had not been given due consideration. Several sets of propellers, 2.5
metres in diameter, unit-pitch ratio, 30-degree blade had been constructed
and were on hand, in order that no delays might be caused through a lack of
such extra parts. On September 9, 1903, when the aerodrome frame without
the wings was mounted on the launching car on top of the boat for some
trial runs with the engine to make sure that everything was again in
readiness, before the engine had made 500 revolutions, the port propeller
broke; and a few minutes [p182] later, when a new propeller had been
substituted for this and the engine was again started up, the starboard
propeller also broke. When, upon further trials and replacements of
propellers, all had been so thoroughly demolished that there was not a
complete set remaining, it was seen very clearly that the strains produced on
couplings to the shafts made it necessary to provide new shafts, gears,
couplings, etc. It was then decided to change the ratio of gearing between
the engine and the propellers, which had been one to one, so that the engine
might run faster and, therefore, permit the use of larger propellers. For
constructional reasons the ratio chosen was thirty-one to forty, thus making
the engine run approximately one-third faster than the propellers.
In the various tests made of the engine working in the frame there were
two or three instances in which the propellers were damaged either by the
sudden starting of the engine or by their not being able to stand the strain to
which they were subjected by the power absorbed, but in every case such
breakages were found to be due to imperfections of the brazing in the joints.
While, therefore, it would have been desirable to make the propellers
somewhat heavier, yet since the total weight of the aerodrome had been
growing so very rapidly, it was felt that this need not be done, as a pair of
propellers which had stood quite severe service in shop tests might
reasonably be expected to stand the strain of actually propelling the
aerodrome through the air.
Nevertheless, when in the summer of 1903 the actual trials of the large
aerodrome were started, it was found that the very important difference
between a propeller working in a closed room and one working in the open
air had not been given due consideration. Several sets of propellers, 2.5
metres in diameter, unit-pitch ratio, 30-degree blade had been constructed
and were on hand, in order that no delays might be caused through a lack of
such extra parts. On September 9, 1903, when the aerodrome frame without
the wings was mounted on the launching car on top of the boat for some
trial runs with the engine to make sure that everything was again in
readiness, before the engine had made 500 revolutions, the port propeller
broke; and a few minutes [p182] later, when a new propeller had been
substituted for this and the engine was again started up, the starboard
propeller also broke. When, upon further trials and replacements of
propellers, all had been so thoroughly demolished that there was not a
complete set remaining, it was seen very clearly that the strains produced on
Page 330
a propeller working in the open air are very much greater than those
produced in shop tests, where the air is necessarily quiet. These open-air
tests of the propellers had demonstrated that their weakest point was where
the steel tubes which received the wooden arms of the blade terminated, and
that another, though not so serious, point of weakness was where the steel
arms were brazed to the central hub, the thin metal tending to tear loose
even before the brazed joint would give way. It was, therefore, decided to
construct immediately a new set of propellers in which the steel arms
should be made of much heavier tubing, that is, a sixteenth of an inch thick
at the end where it was brazed to the central hub, and tapering in thickness
to one-thirty-second of an inch at the other end. These arms were further
made twelve inches long in place of being only three inches long as before.
This added length carried the steel out beyond the point where the first
section brace joined the three arms together, and where they were further
strengthened by having the cloth covering tightly stretched around them. In
order to utilize such of the hubs of the former propellers as had not been
seriously damaged when the propellers broke, it was also decided to try the
effect of merely adding an extra length of tube to the short arms by means
of a thimble slipped over and brazed to the two parts, which would make
these arms twelve inches long. The construction of these propellers was
pushed as rapidly as possible; and after their completion no further trouble
was at any later time caused by insufficient strength of the propellers. Even
in the test of October 7, 1903, when the aerodrome came down in the water
at a speed of something like fifty miles an hour, and at an angle of
approximately forty-five degrees, no break occurred in either propeller
until, when the aerodrome was plunging through the water, a blade of one
propeller was broken by the terrific blow which it received when it struck
the water under the impulse of the engine driving it at full speed. The
severity of this blow is attested by the fact that the shaft, which was of steel
tubing one-eighth inch thick, was twisted about ninety degrees.
This experience with propellers very strongly emphasizes the fact that on
any flying machine the strains which are apt to be met with in the open air
must be allowed for in the proportioning of the parts of the machine. But
produced in shop tests, where the air is necessarily quiet. These open-air
tests of the propellers had demonstrated that their weakest point was where
the steel tubes which received the wooden arms of the blade terminated, and
that another, though not so serious, point of weakness was where the steel
arms were brazed to the central hub, the thin metal tending to tear loose
even before the brazed joint would give way. It was, therefore, decided to
construct immediately a new set of propellers in which the steel arms
should be made of much heavier tubing, that is, a sixteenth of an inch thick
at the end where it was brazed to the central hub, and tapering in thickness
to one-thirty-second of an inch at the other end. These arms were further
made twelve inches long in place of being only three inches long as before.
This added length carried the steel out beyond the point where the first
section brace joined the three arms together, and where they were further
strengthened by having the cloth covering tightly stretched around them. In
order to utilize such of the hubs of the former propellers as had not been
seriously damaged when the propellers broke, it was also decided to try the
effect of merely adding an extra length of tube to the short arms by means
of a thimble slipped over and brazed to the two parts, which would make
these arms twelve inches long. The construction of these propellers was
pushed as rapidly as possible; and after their completion no further trouble
was at any later time caused by insufficient strength of the propellers. Even
in the test of October 7, 1903, when the aerodrome came down in the water
at a speed of something like fifty miles an hour, and at an angle of
approximately forty-five degrees, no break occurred in either propeller
until, when the aerodrome was plunging through the water, a blade of one
propeller was broken by the terrific blow which it received when it struck
the water under the impulse of the engine driving it at full speed. The
severity of this blow is attested by the fact that the shaft, which was of steel
tubing one-eighth inch thick, was twisted about ninety degrees.
This experience with propellers very strongly emphasizes the fact that on
any flying machine the strains which are apt to be met with in the open air
must be allowed for in the proportioning of the parts of the machine. But
Page 331
since an indiscriminate increase of strength in all the various parts of the
machine would entail a prohibitory weight, very careful judgment, based on
experience, will have to be exercised in deciding just where added strength
must be employed, and also where the “live strains” are not apt to exceed
very appreciably the calculation for statical conditions.
machine would entail a prohibitory weight, very careful judgment, based on
experience, will have to be exercised in deciding just where added strength
must be employed, and also where the “live strains” are not apt to exceed
very appreciably the calculation for statical conditions.
Page 332
PL. 59. WING CLAMPS ◊ lgr
Page 333
[p183]
Owing to Mr. Langley’s belief that the tests of the man-carrying
aerodrome must not only be made over the water, but that it was necessary
that the machine be launched from a car running on a track at a
considerable elevation in order to permit the machine to drop a short
distance after being launched in case it was not quite up to soaring speed
when launched, it was necessary that the aerodrome be so constructed that it
could be readily transported to the launching track from the interior of the
house-boat where it was stored. This plan of storing the main body of the
machine in the interior of the boat and hoisting it to the launching track just
before attempting a flight (some of the difficulties of which may be more
clearly appreciated by an inspection of Plate 60), made it necessary that the
wings, tail and guy-posts be so constructed as to be readily attachable to
and detachable from the main frame, and since the weather conditions are
seldom suitable for a test for more than a couple of hours at a time, it was
necessary that the mechanism employed for attaching these parts be so
arranged that the proper settings of the different parts could be quickly
obtained, and without requiring the exercise of judgment which past
experience had shown did not often manifest itself during the hurry of the
preparations for a test. While the wings, therefore, were made removable,
yet all of the sockets, guy-wires, etc., which were loosened in removing
them, were made with positive stops on them so that each fitting that was to
be tightened up in assembling could be adjusted to its definitely determined
position.
As all of the models had been constructed with these same parts
removable in order to permit them to be readily shipped back and forth in
the many trips which had been made with them from Washington to
Chopawamsic Island, the same details of arrangement were used for
attaching these parts on the large aerodrome, though the actual fittings by
which the parts were attached in the latter case became more elaborate.
In the drawings, Plates 52, 53 and 54, the method of attaching the wings
to the frame is clearly shown. Each of the two main ribs of each wing was
secured to the midrod of the frame by a wing clamp, shown in detail in
Owing to Mr. Langley’s belief that the tests of the man-carrying
aerodrome must not only be made over the water, but that it was necessary
that the machine be launched from a car running on a track at a
considerable elevation in order to permit the machine to drop a short
distance after being launched in case it was not quite up to soaring speed
when launched, it was necessary that the aerodrome be so constructed that it
could be readily transported to the launching track from the interior of the
house-boat where it was stored. This plan of storing the main body of the
machine in the interior of the boat and hoisting it to the launching track just
before attempting a flight (some of the difficulties of which may be more
clearly appreciated by an inspection of Plate 60), made it necessary that the
wings, tail and guy-posts be so constructed as to be readily attachable to
and detachable from the main frame, and since the weather conditions are
seldom suitable for a test for more than a couple of hours at a time, it was
necessary that the mechanism employed for attaching these parts be so
arranged that the proper settings of the different parts could be quickly
obtained, and without requiring the exercise of judgment which past
experience had shown did not often manifest itself during the hurry of the
preparations for a test. While the wings, therefore, were made removable,
yet all of the sockets, guy-wires, etc., which were loosened in removing
them, were made with positive stops on them so that each fitting that was to
be tightened up in assembling could be adjusted to its definitely determined
position.
As all of the models had been constructed with these same parts
removable in order to permit them to be readily shipped back and forth in
the many trips which had been made with them from Washington to
Chopawamsic Island, the same details of arrangement were used for
attaching these parts on the large aerodrome, though the actual fittings by
which the parts were attached in the latter case became more elaborate.
In the drawings, Plates 52, 53 and 54, the method of attaching the wings
to the frame is clearly shown. Each of the two main ribs of each wing was
secured to the midrod of the frame by a wing clamp, shown in detail in
Page 334
Figs. 1, 2, 5, 6 and 7 of Plate 59. Figs. 1 and 2 show the clamp for the
middle main rib of each pair of wings, and Figs. 5 and 6 show the clamp for
the main front rib, the latter being so constructed that the wings could be
rocked on the midrib clamp as a pivot and secured at any angle of lift
desired from 6 12 degrees to 15 degrees. The horns on each clamp merely
acted as receiving sockets for the ends of the ribs, and were not in any way
intended to do anything more than merely hold the ends of the ribs in their
correct positions. The wings were fastened to the frame by the guy-wires
which ran from two points on each main rib to an upper and a lower guy-
post mounted on the midrod. The system of guy-wires for the wings is
clearly shown in Plates 52, 53 and 54, and [p184] in Plate 61, which shows
the aerodrome mounted on its launching car at the rear end of the track, and
with the front pair of wings in place and all the guy-wires adjusted. The
details of the guy-posts are shown in Plate 62, where it will be noted that
the lower guy-post was of wood, with metal fittings, and was 2 metres long
from the center of the midrod to the bottom, while the upper guy-post was a
steel tube 109 centimetres long from the center of the midrod to its top. The
guy-wires from the middle rib of each of the pair of wings were fastened to
the fittings at the bottom of the lower guy-post, while the wires from the
front main rib were fastened to the fittings which were brazed and riveted to
the slidable collar, which was mounted on the steel tube forming the cap on
this guy-post. This collar was made slidable to permit the angle of lift of the
wings to be readily changed without affecting the length of the guy-wires.
This collar, when once set for any particular angle of the wing, was
prevented from sliding by a taper pin (not shown) which passed through it
and the guy-post. In order to secure the wings more rigidly to the main
frame and thereby throw on it all torsional strains from the wings, which it
was specially designed to take, each of the middle main ribs was secured to
one of the main tubes of the main frame by an auxiliary clamp at the point
where this rib crossed the main tube. These auxiliary clamps are clearly
shown in Figs. 3 and 4 of Plate 59.
middle main rib of each pair of wings, and Figs. 5 and 6 show the clamp for
the main front rib, the latter being so constructed that the wings could be
rocked on the midrib clamp as a pivot and secured at any angle of lift
desired from 6 12 degrees to 15 degrees. The horns on each clamp merely
acted as receiving sockets for the ends of the ribs, and were not in any way
intended to do anything more than merely hold the ends of the ribs in their
correct positions. The wings were fastened to the frame by the guy-wires
which ran from two points on each main rib to an upper and a lower guy-
post mounted on the midrod. The system of guy-wires for the wings is
clearly shown in Plates 52, 53 and 54, and [p184] in Plate 61, which shows
the aerodrome mounted on its launching car at the rear end of the track, and
with the front pair of wings in place and all the guy-wires adjusted. The
details of the guy-posts are shown in Plate 62, where it will be noted that
the lower guy-post was of wood, with metal fittings, and was 2 metres long
from the center of the midrod to the bottom, while the upper guy-post was a
steel tube 109 centimetres long from the center of the midrod to its top. The
guy-wires from the middle rib of each of the pair of wings were fastened to
the fittings at the bottom of the lower guy-post, while the wires from the
front main rib were fastened to the fittings which were brazed and riveted to
the slidable collar, which was mounted on the steel tube forming the cap on
this guy-post. This collar was made slidable to permit the angle of lift of the
wings to be readily changed without affecting the length of the guy-wires.
This collar, when once set for any particular angle of the wing, was
prevented from sliding by a taper pin (not shown) which passed through it
and the guy-post. In order to secure the wings more rigidly to the main
frame and thereby throw on it all torsional strains from the wings, which it
was specially designed to take, each of the middle main ribs was secured to
one of the main tubes of the main frame by an auxiliary clamp at the point
where this rib crossed the main tube. These auxiliary clamps are clearly
shown in Figs. 3 and 4 of Plate 59.
Page 335
Projecting from the lower end of each of the lower guy-posts was a five-
sixteenth-inch steel rod about one inch long, as clearly seen in Plate 62.
Brazed to the side of this rod, in such a position that it would project
towards the rear of the aerodrome when the guy-post was in position, was a
small arm or bracket. When the guy-post was in place with the aerodrome
on the launching car, this pin was in a slot formed in a metal cap on the top
of the small folding upright at the front or rear of the car, as seen in Fig. 1,
Plate 63, while Fig. 2 of Plate 63 shows the pin just being inserted into this
slot as the guy-wires of the guy-post are being fastened. This small arm or
bracket on this rod projected under the cap to prevent the rod of the guy-
post from being lifted out of the slot in the folding upright, when the wind
acting under the wings tended to lift the aerodrome from the car. Particular
attention is here called to this apparently insignificant detail, for it was this
arm or bracket on this small rod of the front guy-post which, hanging in the
cap on top of the folding upright, caused the accident in the launching of the
aerodrome on October 7, 1903. Certain it is that but for the accident due to
this apparently insignificant detail, success would have crowned the efforts
of Mr. Langley, who above all men deserved success in this field of work,
which his labors had so greatly enriched.
sixteenth-inch steel rod about one inch long, as clearly seen in Plate 62.
Brazed to the side of this rod, in such a position that it would project
towards the rear of the aerodrome when the guy-post was in position, was a
small arm or bracket. When the guy-post was in place with the aerodrome
on the launching car, this pin was in a slot formed in a metal cap on the top
of the small folding upright at the front or rear of the car, as seen in Fig. 1,
Plate 63, while Fig. 2 of Plate 63 shows the pin just being inserted into this
slot as the guy-wires of the guy-post are being fastened. This small arm or
bracket on this rod projected under the cap to prevent the rod of the guy-
post from being lifted out of the slot in the folding upright, when the wind
acting under the wings tended to lift the aerodrome from the car. Particular
attention is here called to this apparently insignificant detail, for it was this
arm or bracket on this small rod of the front guy-post which, hanging in the
cap on top of the folding upright, caused the accident in the launching of the
aerodrome on October 7, 1903. Certain it is that but for the accident due to
this apparently insignificant detail, success would have crowned the efforts
of Mr. Langley, who above all men deserved success in this field of work,
which his labors had so greatly enriched.
Page 336
F IG. 1 F IG. 2 F IG. 3
PL. 60. HOISTING AERODROME TO
LAUNCHING-TRACK ◊
PL. 60. HOISTING AERODROME TO
LAUNCHING-TRACK ◊
Page 337
PL. 61. AERODROME ON LAUNCHING-CAR; FRONT WINGS IN PLACE, GUY-
WIRES ADJUSTED ◊
WIRES ADJUSTED ◊
Page 338
PL. 62. DETAILS OF GUY-POSTS ◊ lgr
Page 339
F IG. 1. F IG. 2.
PL. 63. GUY-POST AND PIN ON LAUNCHING CAR ◊
PL. 63. GUY-POST AND PIN ON LAUNCHING CAR ◊
Page 340
[p185]
A VIATOR’S C AR
In determining on a suitable car for the aviator various designs were
made, differing all the way from that in which the aviator occupied a sitting
position facing directly ahead and with practically no freedom of
movement, but was even strapped to the machine to avoid the possibility of
being thrown out, to the one finally adopted, in which he was provided with
the greatest freedom of movement, could either stand or sit, as the occasion
seemed to demand, and could face in any direction for giving proper
attention to any of the multitudinous things which might at any time require
his attention, and could, if agile, even climb from the extreme front of the
machine to the rear. The wisdom of giving the aviator complete freedom
without hampering him in any way by provisions for preventing his being
thrown out of the machine was amply justified, as will later be seen in the
description of the tests of the machine, where freedom of movement and
agility prevented a fatal accident.
The aviator’s car was therefore designed to occupy the entire available
space between the engine and the front bearing points, and between the two
main tubes of the main frame, thus allowing him a space of something like
three feet by five feet. The car itself was shaped like a flat-bottomed boat,
the bottom being approximately level with the bottom of the lower pyramid.
It had a guard rail of steel tubing eighteen inches above the floor, with a
cloth covering drawn over the frame to decrease the head resistance of the
appurtenances of the engine which were placed at the rear end of the car.
The car was supported by vertical wires passing from its bottom up to the
main frame, and was prevented from longitudinal or side motion by being
fastened at the front to the cross-rod connecting the front bearing points,
and at the rear to the lower pyramid. A light wooden seat extended fore and
aft of the car at a height of about two feet from the floor, this seat resting on
blocks of sponge rubber to absorb some of the tremor which existed in the
whole aerodrome when the engine and propellers were working at high
speed. The aviator was thus free to stand, to sit sidewise or to straddle the
A VIATOR’S C AR
In determining on a suitable car for the aviator various designs were
made, differing all the way from that in which the aviator occupied a sitting
position facing directly ahead and with practically no freedom of
movement, but was even strapped to the machine to avoid the possibility of
being thrown out, to the one finally adopted, in which he was provided with
the greatest freedom of movement, could either stand or sit, as the occasion
seemed to demand, and could face in any direction for giving proper
attention to any of the multitudinous things which might at any time require
his attention, and could, if agile, even climb from the extreme front of the
machine to the rear. The wisdom of giving the aviator complete freedom
without hampering him in any way by provisions for preventing his being
thrown out of the machine was amply justified, as will later be seen in the
description of the tests of the machine, where freedom of movement and
agility prevented a fatal accident.
The aviator’s car was therefore designed to occupy the entire available
space between the engine and the front bearing points, and between the two
main tubes of the main frame, thus allowing him a space of something like
three feet by five feet. The car itself was shaped like a flat-bottomed boat,
the bottom being approximately level with the bottom of the lower pyramid.
It had a guard rail of steel tubing eighteen inches above the floor, with a
cloth covering drawn over the frame to decrease the head resistance of the
appurtenances of the engine which were placed at the rear end of the car.
The car was supported by vertical wires passing from its bottom up to the
main frame, and was prevented from longitudinal or side motion by being
fastened at the front to the cross-rod connecting the front bearing points,
and at the rear to the lower pyramid. A light wooden seat extended fore and
aft of the car at a height of about two feet from the floor, this seat resting on
blocks of sponge rubber to absorb some of the tremor which existed in the
whole aerodrome when the engine and propellers were working at high
speed. The aviator was thus free to stand, to sit sidewise or to straddle the
Page 341
seat, and while the network of wires surrounding him prevented any great
possibility of his being thrown out, yet there was a comparatively large
opening between the guy-wires passing overhead which permitted him to
climb out of the machine.
In order to enable the aviator to know exactly how the engine was
operating, a tachometer, giving instantaneous readings of the number of
revolutions, was connected by a suitable gear to one of the transmission
shafts and placed where it could readily be seen.
During 1898 and 1899 considerable time and attention had been given to
designing an instrument to be carried by the aerodrome which would
automatically record the number of revolutions of the engine, the velocity
and direction [p186] of the wind relative to the machine, the height of the
aerodrome as shown by a specially sensitive aneroid barometer, and the
angle of the machine with the horizontal plane of the earth. The
construction of this instrument was undertaken by a noted firm of
instrument makers, but after many months of delay, during which it was
several times delivered as being complete, only to be returned for further
work, it was finally condemned as unsatisfactory, and it was decided not to
encumber the machine with such a delicate apparatus, which, even if
perfectly made, could not be depended on to work properly when mounted
on the aerodrome frame, in which there was a constant, though minute,
tremor due to the high speed and power of the engine.
The completed frame, which is perhaps best shown in Plates 49, 50 and
51, and Plate 60, Figs. 1, 2 and 3, in spite of its size gave an appearance of
grace and strength which is inadequately represented in the photographs. In
making the designs for the large aerodrome no data were available for use
in calculating the strains that would come on the different parts of the frame
while in the air, and the size and thickness of the tubes and the strength of
the guy-wires were consequently determined almost entirely by “rule of
thumb,” backed by experience with the models. Although the dimensions,
shape, and arrangement of most of the auxiliary parts of the machine were
considerably changed during the course of construction in accordance with
the indications of the exhaustive series of shop tests, the fundamental
possibility of his being thrown out, yet there was a comparatively large
opening between the guy-wires passing overhead which permitted him to
climb out of the machine.
In order to enable the aviator to know exactly how the engine was
operating, a tachometer, giving instantaneous readings of the number of
revolutions, was connected by a suitable gear to one of the transmission
shafts and placed where it could readily be seen.
During 1898 and 1899 considerable time and attention had been given to
designing an instrument to be carried by the aerodrome which would
automatically record the number of revolutions of the engine, the velocity
and direction [p186] of the wind relative to the machine, the height of the
aerodrome as shown by a specially sensitive aneroid barometer, and the
angle of the machine with the horizontal plane of the earth. The
construction of this instrument was undertaken by a noted firm of
instrument makers, but after many months of delay, during which it was
several times delivered as being complete, only to be returned for further
work, it was finally condemned as unsatisfactory, and it was decided not to
encumber the machine with such a delicate apparatus, which, even if
perfectly made, could not be depended on to work properly when mounted
on the aerodrome frame, in which there was a constant, though minute,
tremor due to the high speed and power of the engine.
The completed frame, which is perhaps best shown in Plates 49, 50 and
51, and Plate 60, Figs. 1, 2 and 3, in spite of its size gave an appearance of
grace and strength which is inadequately represented in the photographs. In
making the designs for the large aerodrome no data were available for use
in calculating the strains that would come on the different parts of the frame
while in the air, and the size and thickness of the tubes and the strength of
the guy-wires were consequently determined almost entirely by “rule of
thumb,” backed by experience with the models. Although the dimensions,
shape, and arrangement of most of the auxiliary parts of the machine were
considerably changed during the course of construction in accordance with
the indications of the exhaustive series of shop tests, the fundamental
Page 342
features of the construction were practically unaltered, but the changes in
the guy-wire system and in the fittings by which they were attached, made
the frame as a whole several times as strong as it was originally, and it was
felt that the direction of further improvements in it would be shown only by
actual test of it in flight where any weaknesses would be certain to manifest
themselves.
It may be well to remark here that even with the data which were later
obtained, judgment based on experience proved after all to be the safest
guide for proportioning the strength of the various parts. It can be assumed
that a live stress will produce a strain ten times as great as that due to a
static stress on the part when the machine is stationary. For greater safety, it
would be still better to assume a strain twenty times as great. If one is
building bridges, houses, and similar structures, where weight is not a prime
consideration, it would be criminal negligence to fail to provide a sufficient
“factor of safety,” or what in many instances may be more properly termed
a “factor of ignorance,” while at the present time the insistence on large
factors of safety in machines intended to fly would so enormously increase
the weight that, before one-half the necessary parts were provided, the
weight would be many times what could possibly be supported in the air.
Later, no doubt, as experience is gained in properly handling the machine in
the air, increased strength entailing [p187] increased weight may be added in
proportion to the skill acquired; and there is no doubt that man will acquire
this skill with marvelous rapidity, approaching, if not equaling, that
exhibited by him in the use of the bicycle, which, when first ridden,
requires not only all of the rider’s skill but that of a couple of assistants, but
when once mastered requires hardly more thought for its proper
manipulation than even the act of walking involves, the balancing and
guiding being done intuitively merely by the motion of the body and with
practically no exertion.
the guy-wire system and in the fittings by which they were attached, made
the frame as a whole several times as strong as it was originally, and it was
felt that the direction of further improvements in it would be shown only by
actual test of it in flight where any weaknesses would be certain to manifest
themselves.
It may be well to remark here that even with the data which were later
obtained, judgment based on experience proved after all to be the safest
guide for proportioning the strength of the various parts. It can be assumed
that a live stress will produce a strain ten times as great as that due to a
static stress on the part when the machine is stationary. For greater safety, it
would be still better to assume a strain twenty times as great. If one is
building bridges, houses, and similar structures, where weight is not a prime
consideration, it would be criminal negligence to fail to provide a sufficient
“factor of safety,” or what in many instances may be more properly termed
a “factor of ignorance,” while at the present time the insistence on large
factors of safety in machines intended to fly would so enormously increase
the weight that, before one-half the necessary parts were provided, the
weight would be many times what could possibly be supported in the air.
Later, no doubt, as experience is gained in properly handling the machine in
the air, increased strength entailing [p187] increased weight may be added in
proportion to the skill acquired; and there is no doubt that man will acquire
this skill with marvelous rapidity, approaching, if not equaling, that
exhibited by him in the use of the bicycle, which, when first ridden,
requires not only all of the rider’s skill but that of a couple of assistants, but
when once mastered requires hardly more thought for its proper
manipulation than even the act of walking involves, the balancing and
guiding being done intuitively merely by the motion of the body and with
practically no exertion.
Page 343
[p188] ◊
CHAPTER VI
CONSTRUCTION OF SUPPORTING SURFACES
An examination of the wings of birds, whether those of soarers or of any
other type, impresses one not only with the general strength of the wing, but
also with the fact that, while it possesses considerable stiffness, there is also
a graduated pliability, not only of the whole wing, including the bones, but
more especially in the feathers, the rear tips being exceedingly pliable so
that, when the wing is held in a stiff breeze, they are seen to be easily
deflected in a gentle curve towards the rear and upper side. This lack of
rigidity has several advantages, among the more notable of which is the
lessening of the strains on the wing caused by sudden wind gusts. Of great
importance is the further fact that a supporting surface having a graduated
pliability, such as is possessed by a bird’s wing, does not experience a
shifting of the center of pressure to the same extent as a rigid surface of
similar form. Furthermore, since any bird, even the best soarer, must use its
wings not only for soaring, but, when starting to fly from a state of rest, for
flapping, a rigid surface would not furnish anything like the same
universally available sustaining and propelling means that the bird’s wing
does.
In an inspection of the various wings or supporting surfaces which Mr.
Langley built, from the very earliest rubber-pull models up to the successful
steam machines Nos. 5 and 6, the point which is most impressed upon the
observer is the increasing strength and rigidity embodied in these wings.
While the success with the later models was due to many things, including
the development of a strong frame and a suitable power plant giving
sufficient power for the permissible weight, besides the very important
development of effective equilibrium mechanism, yet it is safe to say that
even with the development of all these other things to the state to which
they had been brought in 1896, success would not have been achieved had
not the wings themselves been simultaneously changed from the very
CHAPTER VI
CONSTRUCTION OF SUPPORTING SURFACES
An examination of the wings of birds, whether those of soarers or of any
other type, impresses one not only with the general strength of the wing, but
also with the fact that, while it possesses considerable stiffness, there is also
a graduated pliability, not only of the whole wing, including the bones, but
more especially in the feathers, the rear tips being exceedingly pliable so
that, when the wing is held in a stiff breeze, they are seen to be easily
deflected in a gentle curve towards the rear and upper side. This lack of
rigidity has several advantages, among the more notable of which is the
lessening of the strains on the wing caused by sudden wind gusts. Of great
importance is the further fact that a supporting surface having a graduated
pliability, such as is possessed by a bird’s wing, does not experience a
shifting of the center of pressure to the same extent as a rigid surface of
similar form. Furthermore, since any bird, even the best soarer, must use its
wings not only for soaring, but, when starting to fly from a state of rest, for
flapping, a rigid surface would not furnish anything like the same
universally available sustaining and propelling means that the bird’s wing
does.
In an inspection of the various wings or supporting surfaces which Mr.
Langley built, from the very earliest rubber-pull models up to the successful
steam machines Nos. 5 and 6, the point which is most impressed upon the
observer is the increasing strength and rigidity embodied in these wings.
While the success with the later models was due to many things, including
the development of a strong frame and a suitable power plant giving
sufficient power for the permissible weight, besides the very important
development of effective equilibrium mechanism, yet it is safe to say that
even with the development of all these other things to the state to which
they had been brought in 1896, success would not have been achieved had
not the wings themselves been simultaneously changed from the very
Page 344
flimsy construction which was at first used to the later type, using a very
strong and rigid wooden frame over which the cloth covering was tightly
stretched, and which possessed only a small amount of pliability at the
extreme rear ends of the cross-ribs.
The development of this successful type of wing for the models, it will be
remembered, had been achieved only after an extensive series of
experiments; and it was realized that the construction of suitable wings for
the large aerodrome, even with the knowledge gained in the early work,
would be still more [p189] difficult. The problem was that of constructing for
a very little greater weight per square foot, wings containing approximately
sixteen times the area of the model wings.
It will be recalled from the previous description of model Aerodrome No.
5, that its four wings had a combined area of 68 square feet and weighed
approximately 2500 grammes, or 37 grammes per square foot. It was not
expected that the large wings would be of so light a weight per square foot,
which would have meant only about 35,500 grammes (approximately 78
pounds) weight for the 960 square feet originally planned. It was hoped,
however, that the increase in weight per square foot for the large wings
would be less than the square root of the increased linear dimensions. In
this case, the increase in linear dimensions being approximately four, it was,
therefore, hoped that the larger wings would not have quite twice the weight
per square foot of the smaller ones; the computed weight permissible for the
large wings was therefore placed at 120 pounds.
To obtain the required area within the permissible limits of weight two
well-defined paths of procedure were open: First, it was possible to so
modify the structural form of the wing as to obtain the advantage of the
increased strength of trussed structures, that is, by superposing the wings.
Or, second, the “single-tier” type of wing, the efficiency of which had been
fairly well determined, could be retained, and strength gained without
increase of weight by improving the method of constructing the wooden
framework and by extending the system of guy-wires.
Some knowledge of the superposed type of supporting surfaces had
already been gained by the experiments at Allegheny and the tests of the
strong and rigid wooden frame over which the cloth covering was tightly
stretched, and which possessed only a small amount of pliability at the
extreme rear ends of the cross-ribs.
The development of this successful type of wing for the models, it will be
remembered, had been achieved only after an extensive series of
experiments; and it was realized that the construction of suitable wings for
the large aerodrome, even with the knowledge gained in the early work,
would be still more [p189] difficult. The problem was that of constructing for
a very little greater weight per square foot, wings containing approximately
sixteen times the area of the model wings.
It will be recalled from the previous description of model Aerodrome No.
5, that its four wings had a combined area of 68 square feet and weighed
approximately 2500 grammes, or 37 grammes per square foot. It was not
expected that the large wings would be of so light a weight per square foot,
which would have meant only about 35,500 grammes (approximately 78
pounds) weight for the 960 square feet originally planned. It was hoped,
however, that the increase in weight per square foot for the large wings
would be less than the square root of the increased linear dimensions. In
this case, the increase in linear dimensions being approximately four, it was,
therefore, hoped that the larger wings would not have quite twice the weight
per square foot of the smaller ones; the computed weight permissible for the
large wings was therefore placed at 120 pounds.
To obtain the required area within the permissible limits of weight two
well-defined paths of procedure were open: First, it was possible to so
modify the structural form of the wing as to obtain the advantage of the
increased strength of trussed structures, that is, by superposing the wings.
Or, second, the “single-tier” type of wing, the efficiency of which had been
fairly well determined, could be retained, and strength gained without
increase of weight by improving the method of constructing the wooden
framework and by extending the system of guy-wires.
Some knowledge of the superposed type of supporting surfaces had
already been gained by the experiments at Allegheny and the tests of the
Page 345
rubber-driven models, in which superposed wings had frequently been used;
but it was felt that this knowledge was altogether inadequate to aid in
determining either whether the superposed type of construction possessed in
practice the advantages which theory would indicate, or how and at what
distance apart the surfaces should be superposed to obtain the best results.
In order to obtain the desired information, a series of tests on the whirling-
table of complete wings suitable for use on the models was made. These
experiments were supplemented by the practical tests with the models,
which have already been described in Chapter III ◊, in order to give the
wings a trial under the conditions of flight, where they would be subjected
to the action of the propellers and the uneven character of the wind.
In addition to determining what type of construction and what form of
surface would give the greatest “lift” with the smallest “drift,” these
whirling-table tests supplied data as to how much greater the actual
resistance of the wing with its necessary guy-posts and guy-wires was than
the theoretical resistance, found by extrapolation from the results obtained
in the tests of rigid [p190] curved surfaces formed of wood. The first of this
series of tests, the results of which are given below, was made November
30, 1898, on the superposed wing shown in Plate 37, Figs. 1 and 2. It
should be noted, however, that when this test was made the wing was not
provided with the stiffening strips or the vertical partitions.
Weight of wing = 1000 grammes; weight of guy-posts, etc., = 475 grammes; distance of mean
center of gravity of guy-posts, etc., from pivots of balance arm = one-half distance of CP of wing
from pivots of balance arm; the wing, therefore, had a lever arm of two to one with reference to
weight of guy-posts, etc., so that the equivalent weight of guy-posts, etc., = 237 grammes. This
gives 1237 grammes of equivalent load on the wing = 2.73 pounds. Area of wing = 21.85 square
feet. Therefore load on wing = 0.125 pounds per square foot.
but it was felt that this knowledge was altogether inadequate to aid in
determining either whether the superposed type of construction possessed in
practice the advantages which theory would indicate, or how and at what
distance apart the surfaces should be superposed to obtain the best results.
In order to obtain the desired information, a series of tests on the whirling-
table of complete wings suitable for use on the models was made. These
experiments were supplemented by the practical tests with the models,
which have already been described in Chapter III ◊, in order to give the
wings a trial under the conditions of flight, where they would be subjected
to the action of the propellers and the uneven character of the wind.
In addition to determining what type of construction and what form of
surface would give the greatest “lift” with the smallest “drift,” these
whirling-table tests supplied data as to how much greater the actual
resistance of the wing with its necessary guy-posts and guy-wires was than
the theoretical resistance, found by extrapolation from the results obtained
in the tests of rigid [p190] curved surfaces formed of wood. The first of this
series of tests, the results of which are given below, was made November
30, 1898, on the superposed wing shown in Plate 37, Figs. 1 and 2. It
should be noted, however, that when this test was made the wing was not
provided with the stiffening strips or the vertical partitions.
Weight of wing = 1000 grammes; weight of guy-posts, etc., = 475 grammes; distance of mean
center of gravity of guy-posts, etc., from pivots of balance arm = one-half distance of CP of wing
from pivots of balance arm; the wing, therefore, had a lever arm of two to one with reference to
weight of guy-posts, etc., so that the equivalent weight of guy-posts, etc., = 237 grammes. This
gives 1237 grammes of equivalent load on the wing = 2.73 pounds. Area of wing = 21.85 square
feet. Therefore load on wing = 0.125 pounds per square foot.
Page 346
Velocity of center
Angle of Revolutions of Drift
of wing (ft. per Velocity (ft. per second).
chord. turn-table. (grammes).
min.)
2.0° 10.75 1086 18.1 255
3.0° 10.0 1010 16.85 255
5.0° 9.5 960 16.0 255
10.0° 7.75 783 13.0 255
Calculated soaring speed
Angle of Foot-pounds per
Drift (pounds). carrying 0.5 pounds per sq.
chord. sec. RV.
ft. (ft. per sec.).
2.0° 0.561 10.15 36.2
3.0° 0.561 9.47 33.7
5.0° 0.561 8.98 32.0
10.0° 0.561 7.3 26.0
The very interesting phenomenon was noted in this test that the “drift” or
resistance of the wing seemed to remain unchanged at soaring speed at
different angles of elevation. It is hardly probable that this result is accurate,
for the “balance arm” undoubtedly twisted under the action of the wing, and
this caused it to strain on its pivots, and thus, to a certain extent, falsify the
record as to drift.
A test of a single-tier wing at different angles of elevation was made on
December 6, 1898. This wing was nearly the same as those used in actual
flights of Aerodromes Nos. 5 and 6 in May and November, 1896, the wing
being of the same width fore and aft, but somewhat shorter. The actual wing
was a little too long to permit its being used on the whirling-table in the
limited space of the shop.
Weight of wing = 420 grammes; weight of guy-posts, etc., = 320 grammes; equivalent weight of
guy-posts, etc., = 150 grammes applied on the wing. Therefore, total load on wing = 570 grammes.
Area of wing = 11.2 square feet; equivalent load on wing = 0.112 pounds per square foot.
Angle of Revolutions of Drift
of wing (ft. per Velocity (ft. per second).
chord. turn-table. (grammes).
min.)
2.0° 10.75 1086 18.1 255
3.0° 10.0 1010 16.85 255
5.0° 9.5 960 16.0 255
10.0° 7.75 783 13.0 255
Calculated soaring speed
Angle of Foot-pounds per
Drift (pounds). carrying 0.5 pounds per sq.
chord. sec. RV.
ft. (ft. per sec.).
2.0° 0.561 10.15 36.2
3.0° 0.561 9.47 33.7
5.0° 0.561 8.98 32.0
10.0° 0.561 7.3 26.0
The very interesting phenomenon was noted in this test that the “drift” or
resistance of the wing seemed to remain unchanged at soaring speed at
different angles of elevation. It is hardly probable that this result is accurate,
for the “balance arm” undoubtedly twisted under the action of the wing, and
this caused it to strain on its pivots, and thus, to a certain extent, falsify the
record as to drift.
A test of a single-tier wing at different angles of elevation was made on
December 6, 1898. This wing was nearly the same as those used in actual
flights of Aerodromes Nos. 5 and 6 in May and November, 1896, the wing
being of the same width fore and aft, but somewhat shorter. The actual wing
was a little too long to permit its being used on the whirling-table in the
limited space of the shop.
Weight of wing = 420 grammes; weight of guy-posts, etc., = 320 grammes; equivalent weight of
guy-posts, etc., = 150 grammes applied on the wing. Therefore, total load on wing = 570 grammes.
Area of wing = 11.2 square feet; equivalent load on wing = 0.112 pounds per square foot.
Page 347
Velocity of center
Angle of Revolutions of Drift
of wing (ft. per Velocity (ft. per second).
chord. turn-table. (grammes).
min.)
2.0° 11.6 1195 19.9 210
3.0° 9.75 1005 16.7 157
5.0° 8.25 850 14.2 133
10.0° 6.75 695 11.6 129
12.5° 6.0 618 10.3 129
Calculated soaring speed
Angle of Foot-pounds per
Drift (pounds). carrying 0.5 pounds per sq.
chord. sec. RV.
ft. (ft. per sec.).
2.0° 0.462 9.2 42.1
3.0° 0.345 5.77 35.3
5.0° 0.293 4.16 30.0
10.0° 0.284 3.29 24.5
12.5° 0.284 2.92 21.8
In this test it is to be noted that the “drift,” or resistance, while
considerably greater at soaring speed for 2 degrees than for 5 degrees,
remains practically the same between 5 degrees and 12 12 degrees.
Comparing it with the preceding test with the superposed wing, it is seen
that at soaring speed at an angle of 10 degrees, the single-tier wing having a
load of 0.112 pounds per [p191] square foot, has only 129 grammes drift,
while the superposed one, while supporting 0.125 pounds per square foot,
has 255 grammes drift. Moreover, the soaring speed of the single-tier wing
is only 11.6 feet per second, while the superposed one requires a speed of
13 feet per second.
As the superposed wing tested on November 30 was so weak structurally
that it could not be made to keep its proper shape without adding an
excessive number of guy-wires, it was decided that it was not adapted for
use on the aerodrome, but before abandoning it the partitions and strips
were added and it was again tested on the whirling-table on March 1, 1899,
with the following results:
Weight of wing = 905 grammes; weight of guy-posts, etc., = 320 grammes; equivalent weight of
guy-posts, etc., = 150 grammes applied at CP of the wing; equivalent load on the wing = 1055
grammes = 2.321 pounds; area of wing = 21.85 square feet; equivalent load on wing = 0.1062
pounds per square foot.
Angle of Revolutions of Drift
of wing (ft. per Velocity (ft. per second).
chord. turn-table. (grammes).
min.)
2.0° 11.6 1195 19.9 210
3.0° 9.75 1005 16.7 157
5.0° 8.25 850 14.2 133
10.0° 6.75 695 11.6 129
12.5° 6.0 618 10.3 129
Calculated soaring speed
Angle of Foot-pounds per
Drift (pounds). carrying 0.5 pounds per sq.
chord. sec. RV.
ft. (ft. per sec.).
2.0° 0.462 9.2 42.1
3.0° 0.345 5.77 35.3
5.0° 0.293 4.16 30.0
10.0° 0.284 3.29 24.5
12.5° 0.284 2.92 21.8
In this test it is to be noted that the “drift,” or resistance, while
considerably greater at soaring speed for 2 degrees than for 5 degrees,
remains practically the same between 5 degrees and 12 12 degrees.
Comparing it with the preceding test with the superposed wing, it is seen
that at soaring speed at an angle of 10 degrees, the single-tier wing having a
load of 0.112 pounds per [p191] square foot, has only 129 grammes drift,
while the superposed one, while supporting 0.125 pounds per square foot,
has 255 grammes drift. Moreover, the soaring speed of the single-tier wing
is only 11.6 feet per second, while the superposed one requires a speed of
13 feet per second.
As the superposed wing tested on November 30 was so weak structurally
that it could not be made to keep its proper shape without adding an
excessive number of guy-wires, it was decided that it was not adapted for
use on the aerodrome, but before abandoning it the partitions and strips
were added and it was again tested on the whirling-table on March 1, 1899,
with the following results:
Weight of wing = 905 grammes; weight of guy-posts, etc., = 320 grammes; equivalent weight of
guy-posts, etc., = 150 grammes applied at CP of the wing; equivalent load on the wing = 1055
grammes = 2.321 pounds; area of wing = 21.85 square feet; equivalent load on wing = 0.1062
pounds per square foot.
Page 348
Velocity of center
Angle of Revolutions of Drift
of wing (ft. per Velocity (ft. per second).
chord. turn-table. (grammes).
min.)
5.0° 10.875 1100 18.35 250
5.0° 10.75 1085 18.07 250
5.0° 10.75 1085 18.07 250
10.0° 8.0 808 13.47 250
10.0° 8.0 808 13.47 250
10.5° 7.875 797 13.3 250
10.5° 7.875 797 13.3 250
13.0° 7.0 707 11.78 250
Calculated soaring speed
Angle of Foot-pounds per
Drift (pounds). carrying 0.5 pounds per sq.
chord. sec. RV.
ft. (ft. per sec.).
5.0° 0.55 10.1 39.81
5.0° 0.55 9.94 39.19
5.0° 0.55 9.94 39.19
10.0° 0.55 7.4 29.226
10.0° 0.55 7.4 29.226
10.5° 0.55 7.32 28.86
10.5° 0.55 7.32 28.86
13.0° 0.55 6.48 25.553
An examination of the data obtained in this test shows the wing to be of
slightly less efficiency than when first tested. While it was considerably
stronger it was still too weak for use on the aerodromes.
A second type of superposed wing, Plates 64 and 65, was therefore
constructed and tested on the whirling-table on March 2, 1899, with the
following results:
Weight of wing = 1025 grammes; weight of guy-posts, etc., = 320 grammes; equivalent weight
of guy-posts, etc., = 150 grammes applied at CP of the wing; equivalent load on the wing = 1175
grammes = 2.585 pounds; area of wing = 21.85 square feet; equivalent load on wing = .1183
pounds per square foot.
Angle of Revolutions of Drift
of wing (ft. per Velocity (ft. per second).
chord. turn-table. (grammes).
min.)
5.0° 10.875 1100 18.35 250
5.0° 10.75 1085 18.07 250
5.0° 10.75 1085 18.07 250
10.0° 8.0 808 13.47 250
10.0° 8.0 808 13.47 250
10.5° 7.875 797 13.3 250
10.5° 7.875 797 13.3 250
13.0° 7.0 707 11.78 250
Calculated soaring speed
Angle of Foot-pounds per
Drift (pounds). carrying 0.5 pounds per sq.
chord. sec. RV.
ft. (ft. per sec.).
5.0° 0.55 10.1 39.81
5.0° 0.55 9.94 39.19
5.0° 0.55 9.94 39.19
10.0° 0.55 7.4 29.226
10.0° 0.55 7.4 29.226
10.5° 0.55 7.32 28.86
10.5° 0.55 7.32 28.86
13.0° 0.55 6.48 25.553
An examination of the data obtained in this test shows the wing to be of
slightly less efficiency than when first tested. While it was considerably
stronger it was still too weak for use on the aerodromes.
A second type of superposed wing, Plates 64 and 65, was therefore
constructed and tested on the whirling-table on March 2, 1899, with the
following results:
Weight of wing = 1025 grammes; weight of guy-posts, etc., = 320 grammes; equivalent weight
of guy-posts, etc., = 150 grammes applied at CP of the wing; equivalent load on the wing = 1175
grammes = 2.585 pounds; area of wing = 21.85 square feet; equivalent load on wing = .1183
pounds per square foot.
Page 349
Velocity of center
Angle of Revolutions of Drift
of wing (ft. per Velocity (ft. per second).
chord. turn-table. (grammes).
min.)
5.0° 11.625 1170 19.5 250
5.0° 11.625 1170 19.5 250
8.0° 10.5 1060 17.7 250
10.0° 9.125 919 15.3 250
10.0° 9.125 919 15.3 250
Calculated soaring speed
Angle of Foot-pounds per
Drift (pounds). carrying 0.5 pounds per sq.
chord. sec. RV.
ft. (ft. per sec.).
5.0° 0.55 10.72 40.087
5.0° 0.55 10.72 40.087
8.0° 0.55 9.75 36.37
10.0° 0.55 8.43 31.4
10.0° 0.55 8.43 31.4
During the tests on the whirling-table this type of construction seemed to
be exceedingly strong and stiff, and to be easily maintained in whatever
position it was placed. It was therefore thought that it would prove strong
enough for the aerodrome, and it was accordingly inverted and given a
“sanding test” [p192] by sprinkling sand uniformly over it to such a thickness
as to cause it to have a load of 0.75 pounds per square foot. As it showed no
serious deflection or change of form under the sanding test, it was decided
that it was strong enough for use in tests of the model aerodromes in actual
flight.
Upon the completion of these whirling-table tests, the cloth covering of
this wing was painted with collodion varnish, which increased the weight of
the wing only 50 grammes. In order to make the results of its tests more
easily comparable with those obtained before varnishing, the cross guy-
wires on the wing were changed to a slightly smaller size in order to make
the weight of the wing the same as before. It was tested on March 3, and the
following results were obtained:
Weight of wing = 1025 grammes; weight of guy posts, etc., = 320 grammes; equivalent weight
of guy-posts, etc., = 150 grammes applied at CP of the wing; equivalent load on wing = 1175
grammes = 2.585 pounds; area of wing = 21.85 square feet; equivalent load on wing = .1183
pounds per square foot.
Angle of Revolutions of Drift
of wing (ft. per Velocity (ft. per second).
chord. turn-table. (grammes).
min.)
5.0° 11.625 1170 19.5 250
5.0° 11.625 1170 19.5 250
8.0° 10.5 1060 17.7 250
10.0° 9.125 919 15.3 250
10.0° 9.125 919 15.3 250
Calculated soaring speed
Angle of Foot-pounds per
Drift (pounds). carrying 0.5 pounds per sq.
chord. sec. RV.
ft. (ft. per sec.).
5.0° 0.55 10.72 40.087
5.0° 0.55 10.72 40.087
8.0° 0.55 9.75 36.37
10.0° 0.55 8.43 31.4
10.0° 0.55 8.43 31.4
During the tests on the whirling-table this type of construction seemed to
be exceedingly strong and stiff, and to be easily maintained in whatever
position it was placed. It was therefore thought that it would prove strong
enough for the aerodrome, and it was accordingly inverted and given a
“sanding test” [p192] by sprinkling sand uniformly over it to such a thickness
as to cause it to have a load of 0.75 pounds per square foot. As it showed no
serious deflection or change of form under the sanding test, it was decided
that it was strong enough for use in tests of the model aerodromes in actual
flight.
Upon the completion of these whirling-table tests, the cloth covering of
this wing was painted with collodion varnish, which increased the weight of
the wing only 50 grammes. In order to make the results of its tests more
easily comparable with those obtained before varnishing, the cross guy-
wires on the wing were changed to a slightly smaller size in order to make
the weight of the wing the same as before. It was tested on March 3, and the
following results were obtained:
Weight of wing = 1025 grammes; weight of guy posts, etc., = 320 grammes; equivalent weight
of guy-posts, etc., = 150 grammes applied at CP of the wing; equivalent load on wing = 1175
grammes = 2.585 pounds; area of wing = 21.85 square feet; equivalent load on wing = .1183
pounds per square foot.
Page 350
Velocity of center
Angle of Revolutions of Drift
of wing (ft. per Velocity (ft. per second).
chord. turn-table. (grammes).
min.)
5.0° 10.5 1060 17.7 250
5.0° 10.5 1060 17.7 250
10.0° 8.5 859 14.3 250
10.0° 8.5 859 14.3 250
Calculated soaring speed
Angle of Foot-pounds per
Drift (pounds). carrying 0.5 pounds per sq.
chord. sec. RV.
ft. (ft. per sec.).
5.0° 0.55 9.75 36.37
5.0° 0.55 9.75 36.37
10.0° 0.55 7.88 29.4
10.0° 0.55 7.88 29.4
Although the varnishing of the wing seemed to have no effect on the
“drift,” the soaring speed was slightly decreased.
As a result of these tests it was decided to construct three more wings
like this second type, the four forming a complete set for use on the steam-
driven models Nos. 5 and 6. Although the tests on the whirling-table
indicated a superior efficiency for the “single-tier” wings, and it was not
expected that in actual use on the aerodrome the result would be different,
yet it was felt that as the conditions of actual use are so very different from
those of a whirling-table experiment it would not be safe to decide too
definitely against the superposed wings without first giving them a test
under actual conditions. Aside from the decreased lifting effect shown by
the superposed wing when compared with the “single-tier” one, it was also
thought that under the actual conditions of use on the machine the
superposed wing would show up still worse. The deflection of the air by the
front wings diminishes the lift of the rear ones even for the “single-tier”
type, and this, it seemed certain, would be greatly aggravated in the case of
the superposed type.
In order to emphasize more fully the results of these tests the following
table is added, which gives the data for the “single-tier” wing and this
second type of superposed one, when each was tested at ten degrees angle
of elevation:
Angle of Revolutions of Drift
of wing (ft. per Velocity (ft. per second).
chord. turn-table. (grammes).
min.)
5.0° 10.5 1060 17.7 250
5.0° 10.5 1060 17.7 250
10.0° 8.5 859 14.3 250
10.0° 8.5 859 14.3 250
Calculated soaring speed
Angle of Foot-pounds per
Drift (pounds). carrying 0.5 pounds per sq.
chord. sec. RV.
ft. (ft. per sec.).
5.0° 0.55 9.75 36.37
5.0° 0.55 9.75 36.37
10.0° 0.55 7.88 29.4
10.0° 0.55 7.88 29.4
Although the varnishing of the wing seemed to have no effect on the
“drift,” the soaring speed was slightly decreased.
As a result of these tests it was decided to construct three more wings
like this second type, the four forming a complete set for use on the steam-
driven models Nos. 5 and 6. Although the tests on the whirling-table
indicated a superior efficiency for the “single-tier” wings, and it was not
expected that in actual use on the aerodrome the result would be different,
yet it was felt that as the conditions of actual use are so very different from
those of a whirling-table experiment it would not be safe to decide too
definitely against the superposed wings without first giving them a test
under actual conditions. Aside from the decreased lifting effect shown by
the superposed wing when compared with the “single-tier” one, it was also
thought that under the actual conditions of use on the machine the
superposed wing would show up still worse. The deflection of the air by the
front wings diminishes the lift of the rear ones even for the “single-tier”
type, and this, it seemed certain, would be greatly aggravated in the case of
the superposed type.
In order to emphasize more fully the results of these tests the following
table is added, which gives the data for the “single-tier” wing and this
second type of superposed one, when each was tested at ten degrees angle
of elevation:
Page 351
PL. 64. EXPERIMENTAL TYPE OF SUPERPOSED WINGS, MARCH 2, 1899 ◊
Page 352
PL. 65. EXPERIMENTAL TYPE OF SUPERPOSED WINGS,
MARCH 2, 1899 ◊
[p193]
MARCH 2, 1899 ◊
[p193]
Page 353
Wing
Superposed.
“Single-tier”
Type No. 2
Length (feet). 4.27 4.27
Area (sq. ft.). 11.2 21.9
Weight (pounds). 1.26 2.59
Angle of chord. (°) 10 10
Soaringspeed, (ft. per sec.). 11.6 14.3
Weight (lbs. per sq. ft.). .112 .118
Drift (lbs. per sq. ft.). .025 .026
Calculated soaring speed, carrying 0.5 lbs. per
24.5 29.4
sq. ft. (ft. per sec.).
The “single-tier” wings actually used on Aerodrome No. 6 were 5.33 feet
long, while the wing tested above was only 4.27 feet long. In order to bring
out more fully what might be expected of Aerodrome No. 6, when using the
two different types of wings, the following table, calculated from the
preceding one, is given. This shows the results which might be expected
from the aerodrome when the resistance of the machine itself was included:
Aerodrome No. 6 without wings weighs 22 pounds.
“Single-tier”
“Single-tier” Superposed.
(full
(short) Type No. 2
length)
Length (feet). 4.27 5.30 4.27
Area of two pair of wings (sq. feet). 44.8 54.0 87.6
Weight of two pair of wings (pounds). 5.04 5.5 10.36
Weight of aerodrome with two pair of wings
27.04 27.5 32.36
(lbs.).
Total weight to be supported (lbs. per sq. ft.). 0.603 0.51 0.369
Drift of wings (lbs.). 6.06 6.13 6.9
Assumed drift of aerodrome body (lbs.). 1.0 1.0 1.0
Total drift (pounds). 7.06 7.13 7.9
Soaring speed (ft. per sec.). 27.0 24.7 25.3
Thrust horse-power expended. 0.35 0.32 0.364
Brake horse-power expended. 0.70 0.64 0.73
The first line shows the calculations for the aerodrome when equipped
with the short “single-tier” wings; the second line, when equipped with the
“single-tier” wings of the full length used in the flights of 1896; and the
third line, when equipped with superposed wings, Type No. 2.
It will be seen that, on the whole, the result of the comparison of the full-
length “single-tier” wing and the superposed one is less in favor of the latter
Superposed.
“Single-tier”
Type No. 2
Length (feet). 4.27 4.27
Area (sq. ft.). 11.2 21.9
Weight (pounds). 1.26 2.59
Angle of chord. (°) 10 10
Soaringspeed, (ft. per sec.). 11.6 14.3
Weight (lbs. per sq. ft.). .112 .118
Drift (lbs. per sq. ft.). .025 .026
Calculated soaring speed, carrying 0.5 lbs. per
24.5 29.4
sq. ft. (ft. per sec.).
The “single-tier” wings actually used on Aerodrome No. 6 were 5.33 feet
long, while the wing tested above was only 4.27 feet long. In order to bring
out more fully what might be expected of Aerodrome No. 6, when using the
two different types of wings, the following table, calculated from the
preceding one, is given. This shows the results which might be expected
from the aerodrome when the resistance of the machine itself was included:
Aerodrome No. 6 without wings weighs 22 pounds.
“Single-tier”
“Single-tier” Superposed.
(full
(short) Type No. 2
length)
Length (feet). 4.27 5.30 4.27
Area of two pair of wings (sq. feet). 44.8 54.0 87.6
Weight of two pair of wings (pounds). 5.04 5.5 10.36
Weight of aerodrome with two pair of wings
27.04 27.5 32.36
(lbs.).
Total weight to be supported (lbs. per sq. ft.). 0.603 0.51 0.369
Drift of wings (lbs.). 6.06 6.13 6.9
Assumed drift of aerodrome body (lbs.). 1.0 1.0 1.0
Total drift (pounds). 7.06 7.13 7.9
Soaring speed (ft. per sec.). 27.0 24.7 25.3
Thrust horse-power expended. 0.35 0.32 0.364
Brake horse-power expended. 0.70 0.64 0.73
The first line shows the calculations for the aerodrome when equipped
with the short “single-tier” wings; the second line, when equipped with the
“single-tier” wings of the full length used in the flights of 1896; and the
third line, when equipped with superposed wings, Type No. 2.
It will be seen that, on the whole, the result of the comparison of the full-
length “single-tier” wing and the superposed one is less in favor of the latter
Page 354
than was to be expected, as, aside from its greater structural strength, it
seems to have no real point of superiority, except that it is shorter; and, as
already pointed out, one point of presumable inferiority, though not
exhibited in the table, is the fact that the rear set of wings would suffer
relatively more from being in the lee of the front ones, in the case of the
superposed wings, than in the case of the “single-tier” ones.
Besides these “conventional” forms of wings, various other types were
tested on the whirling-table. The data of these tests are not given, as in the
rough preliminary tests the results were so entirely negative in character
that accurate quantitative tests were never made. However, since in work of
this kind the greatest delay is experienced in learning what not to do, and in
ridding one’s self of freak notions which are continually suggesting
themselves, it may be well here to describe sufficiently at least one of these
types of wing to enable others to avoid any loss of time in experiments with
it. Since the principal disadvantages of a wing possessing considerable
width in the fore and aft direction are due to the great extent through which
the center of pressure [p194] shifts when the velocity of advance or angle of
incidence is changed, and to the further fact that a wide surface does not
support proportionately as much per square foot as a long and narrow one,
it was thought that some advantage might be gained by making the covering
of the wing in the form of strips, the edges of which would be perpendicular
to the direction of motion, or by making this covering in more or less slat-
like form, which would permit the air which had already been acted upon
by the leading slat to slip through between the rear edge of the first slat and
the leading edge of the succeeding one. In the tests on the whirling-table,
however, it was found that this type of construction not only did not possess
any advantages, but was even less effective than a similar one in which the
covering was continuous. The difference was probably due to the fact that
the air which passed between the slats reduced the suction on the upper side
of the following slat, and also to the fact that the distance between the slats
was not sufficient to gain the effect of having each slat act on air which had
not already been partially deflected by the preceding one.
seems to have no real point of superiority, except that it is shorter; and, as
already pointed out, one point of presumable inferiority, though not
exhibited in the table, is the fact that the rear set of wings would suffer
relatively more from being in the lee of the front ones, in the case of the
superposed wings, than in the case of the “single-tier” ones.
Besides these “conventional” forms of wings, various other types were
tested on the whirling-table. The data of these tests are not given, as in the
rough preliminary tests the results were so entirely negative in character
that accurate quantitative tests were never made. However, since in work of
this kind the greatest delay is experienced in learning what not to do, and in
ridding one’s self of freak notions which are continually suggesting
themselves, it may be well here to describe sufficiently at least one of these
types of wing to enable others to avoid any loss of time in experiments with
it. Since the principal disadvantages of a wing possessing considerable
width in the fore and aft direction are due to the great extent through which
the center of pressure [p194] shifts when the velocity of advance or angle of
incidence is changed, and to the further fact that a wide surface does not
support proportionately as much per square foot as a long and narrow one,
it was thought that some advantage might be gained by making the covering
of the wing in the form of strips, the edges of which would be perpendicular
to the direction of motion, or by making this covering in more or less slat-
like form, which would permit the air which had already been acted upon
by the leading slat to slip through between the rear edge of the first slat and
the leading edge of the succeeding one. In the tests on the whirling-table,
however, it was found that this type of construction not only did not possess
any advantages, but was even less effective than a similar one in which the
covering was continuous. The difference was probably due to the fact that
the air which passed between the slats reduced the suction on the upper side
of the following slat, and also to the fact that the distance between the slats
was not sufficient to gain the effect of having each slat act on air which had
not already been partially deflected by the preceding one.
Page 355
In view of the results of these tests on various types of wings, it was
decided that in constructing the first set of wings for the large aerodrome it
would be best to employ the “single-tier” type, which had proved successful
with the models, and that after getting a successful flight with these the
superposed wings would be tried in order to get, if possible, the advantage
which they possessed of being structurally stronger and more compact. It
was therefore clear that any gain in the strength and rigidity of the first set
of wings, as a whole, would have to be obtained by improvements in the
construction of its integral parts, that is, in the main and cross-ribs which
made up its framework.
Before attempting to proportion the parts of the necessary wooden wing
frame, which it was expected would probably undergo many changes before
a final design was secured which would embody maximum strength for
minimum weight, various tests were made to determine just how light a
cloth covering could be obtained which would be strong enough and
sufficiently impervious to the air. In the construction of the wings for the
models a good grade of China silk had been employed, but on account of
the greatly increased quantity of cloth required for the large wings, it was
hoped that something approximately as good as the silk could be secured at
a much less cost, and various grades of percaline were therefore tested. The
weight of the various grades of percaline ranged from three grammes to ten
grammes per square foot, the lighter samples being of a rather coarse mesh,
while the heaviest ones were not only close mesh but some specimens
contained a large amount of “sizing.” The particular grade which was
finally adopted weighed seven grammes per square foot. This material was
practically impervious to air at a pressure of one pound per square foot,
which, of course, was considerably [p195] more than it would be subjected to
in flight. This grade of percaline weighed approximately one and a half
times as much as a grade of silk, which on test was found to have a slightly
greater tensile strength than the percaline, though the latter did not “flute”
or “pocket” nearly as much as the silk. Moreover, the cost of the percaline
was only about one-third that of the silk, and it was chiefly for this reason
that percaline was adopted in place of silk. Allowing for necessary seams
decided that in constructing the first set of wings for the large aerodrome it
would be best to employ the “single-tier” type, which had proved successful
with the models, and that after getting a successful flight with these the
superposed wings would be tried in order to get, if possible, the advantage
which they possessed of being structurally stronger and more compact. It
was therefore clear that any gain in the strength and rigidity of the first set
of wings, as a whole, would have to be obtained by improvements in the
construction of its integral parts, that is, in the main and cross-ribs which
made up its framework.
Before attempting to proportion the parts of the necessary wooden wing
frame, which it was expected would probably undergo many changes before
a final design was secured which would embody maximum strength for
minimum weight, various tests were made to determine just how light a
cloth covering could be obtained which would be strong enough and
sufficiently impervious to the air. In the construction of the wings for the
models a good grade of China silk had been employed, but on account of
the greatly increased quantity of cloth required for the large wings, it was
hoped that something approximately as good as the silk could be secured at
a much less cost, and various grades of percaline were therefore tested. The
weight of the various grades of percaline ranged from three grammes to ten
grammes per square foot, the lighter samples being of a rather coarse mesh,
while the heaviest ones were not only close mesh but some specimens
contained a large amount of “sizing.” The particular grade which was
finally adopted weighed seven grammes per square foot. This material was
practically impervious to air at a pressure of one pound per square foot,
which, of course, was considerably [p195] more than it would be subjected to
in flight. This grade of percaline weighed approximately one and a half
times as much as a grade of silk, which on test was found to have a slightly
greater tensile strength than the percaline, though the latter did not “flute”
or “pocket” nearly as much as the silk. Moreover, the cost of the percaline
was only about one-third that of the silk, and it was chiefly for this reason
that percaline was adopted in place of silk. Allowing for necessary seams
Page 356
and extra material to be turned over at the front and rear edges of the wings,
the percaline covering, which under the original plans comprised
approximately 1000 square feet, was therefore calculated to weigh
approximately 7000 grammes, exclusive of the necessary cords for lacing
the coverings to the wooden frames of the wings.
As the one hundred and twenty pounds allowed for the four wings
permitted only thirty pounds per wing, and as the cloth covering, lacing
cords, etc., were found to weigh something over four pounds, there
remained only about 25 pounds as the permissible weight of the wooden
framing, including the necessary metal clips, secondary guy-wires, etc., for
each wing. With the relative proportions of the various parts of the wooden
framing of the wings of the models as a basis, it was decided to make the
main ribs of the large wings 1.5 inches in diameter for one-half their length,
and have them taper from this size to one inch in diameter at the extreme
point. After making allowance for the weight of these ribs, it was found
that, if the cross-ribs were to be spaced no farther than ten inches apart, and
the two end ones were to be made at least as wide as 1.5 inches in order to
resist the end strain due to the stress of the cloth, the twenty-six
intermediate cross-ribs could be only seven-sixteenths of an inch in
diameter at the point where they crossed the main rib, and that they must be
tapered to three-eighths of an inch in diameter at the front end and to one-
fourth of an inch in diameter at the rear tip.
A trial wing, whose total weight was 30 pounds 2 ounces, was made up
with the various parts of its frame of the above dimensions. Even upon
inspection it appeared to be too flimsy to withstand the sudden gusts of
wind which were certain to be met in actual practice. In order, however, to
get some definite data as a guide, the wing was inverted and guyed in the
same way that it was proposed to guy it on the aerodrome, and a uniform
thickness of sand was then sprinkled over it to such a depth as to give it a
load of 0.7 pounds per square foot. Even before one-quarter of the sand was
sprinkled over it, it was seen that the wing was rapidly going out of shape,
and it was feared that the full amount of sand would not only seriously
distort it, but would even break it. The full quantity of sand, however, did
the percaline covering, which under the original plans comprised
approximately 1000 square feet, was therefore calculated to weigh
approximately 7000 grammes, exclusive of the necessary cords for lacing
the coverings to the wooden frames of the wings.
As the one hundred and twenty pounds allowed for the four wings
permitted only thirty pounds per wing, and as the cloth covering, lacing
cords, etc., were found to weigh something over four pounds, there
remained only about 25 pounds as the permissible weight of the wooden
framing, including the necessary metal clips, secondary guy-wires, etc., for
each wing. With the relative proportions of the various parts of the wooden
framing of the wings of the models as a basis, it was decided to make the
main ribs of the large wings 1.5 inches in diameter for one-half their length,
and have them taper from this size to one inch in diameter at the extreme
point. After making allowance for the weight of these ribs, it was found
that, if the cross-ribs were to be spaced no farther than ten inches apart, and
the two end ones were to be made at least as wide as 1.5 inches in order to
resist the end strain due to the stress of the cloth, the twenty-six
intermediate cross-ribs could be only seven-sixteenths of an inch in
diameter at the point where they crossed the main rib, and that they must be
tapered to three-eighths of an inch in diameter at the front end and to one-
fourth of an inch in diameter at the rear tip.
A trial wing, whose total weight was 30 pounds 2 ounces, was made up
with the various parts of its frame of the above dimensions. Even upon
inspection it appeared to be too flimsy to withstand the sudden gusts of
wind which were certain to be met in actual practice. In order, however, to
get some definite data as a guide, the wing was inverted and guyed in the
same way that it was proposed to guy it on the aerodrome, and a uniform
thickness of sand was then sprinkled over it to such a depth as to give it a
load of 0.7 pounds per square foot. Even before one-quarter of the sand was
sprinkled over it, it was seen that the wing was rapidly going out of shape,
and it was feared that the full amount of sand would not only seriously
distort it, but would even break it. The full quantity of sand, however, did
Page 357
not break it, but distorted it to such an extent that, had the pressure been due
to its being propelled through the air, its serious change in form would have
rendered it worse than useless. [p196] While the main ribs had shown a
certain amount of deflection under the sanding test, the more serious
distortion had been in the cross-ribs, the small guy-wires, which had been
fastened to each cross-rib, becoming loose instead of tight, as had been
expected, since the rib tended to increase its curvature instead of
straightening out. This increase in the curvature of the cross-ribs was partly
overcome by tying the guy-wire flat against the cross-rib for a distance of
about 2 feet from the rear tip. But while this caused the guy-wire to tighten
the general contour of the wing showed very little improvement, as the ribs
now assumed a curve more or less like the letter S, the rear tip now being
bent downward to form the tail of the elongated S.
From this sanding test it was seen that the cross-ribs must be materially
stiffer, and a new set was accordingly made one-sixteenth of an inch larger
in diameter at the various points of measurement. Upon giving the wing,
equipped with these larger ribs, a sanding test it was found that, while there
had been some improvement, it was entirely too flimsy, even when it been
double-guyed by running a second wire on each cross-rib from the middle
of the portion in front of the mid-rib to the middle of the portion behind the
mid-rib. As the weight of the wing with these larger solid cross-ribs had
now increased to more than 33 pounds, and the wing had proved itself
altogether too weak for use on the aerodrome, it was evident that some
other plan of constructing the ribs which would give greater strength for the
same weight must be found. At first sight it might appear that the obvious
way of increasing the stiffness of the cross-ribs was to employ a cross-
section other than a round one, since material added to the depth of the rib
is very much more effective than if added to the width. It must, however, be
remembered that these cross-ribs were 11 feet long, and that, as the main
mid-rib was 6 feet in front of the rear tips of the cross-ribs, with no
intermediate bracing, except the light threads by which the cloth cover was
attached, it was inevitable that, should the depth be made materially greater
than the width, the rib would buckle sideways. Test ribs of I-beam form,
to its being propelled through the air, its serious change in form would have
rendered it worse than useless. [p196] While the main ribs had shown a
certain amount of deflection under the sanding test, the more serious
distortion had been in the cross-ribs, the small guy-wires, which had been
fastened to each cross-rib, becoming loose instead of tight, as had been
expected, since the rib tended to increase its curvature instead of
straightening out. This increase in the curvature of the cross-ribs was partly
overcome by tying the guy-wire flat against the cross-rib for a distance of
about 2 feet from the rear tip. But while this caused the guy-wire to tighten
the general contour of the wing showed very little improvement, as the ribs
now assumed a curve more or less like the letter S, the rear tip now being
bent downward to form the tail of the elongated S.
From this sanding test it was seen that the cross-ribs must be materially
stiffer, and a new set was accordingly made one-sixteenth of an inch larger
in diameter at the various points of measurement. Upon giving the wing,
equipped with these larger ribs, a sanding test it was found that, while there
had been some improvement, it was entirely too flimsy, even when it been
double-guyed by running a second wire on each cross-rib from the middle
of the portion in front of the mid-rib to the middle of the portion behind the
mid-rib. As the weight of the wing with these larger solid cross-ribs had
now increased to more than 33 pounds, and the wing had proved itself
altogether too weak for use on the aerodrome, it was evident that some
other plan of constructing the ribs which would give greater strength for the
same weight must be found. At first sight it might appear that the obvious
way of increasing the stiffness of the cross-ribs was to employ a cross-
section other than a round one, since material added to the depth of the rib
is very much more effective than if added to the width. It must, however, be
remembered that these cross-ribs were 11 feet long, and that, as the main
mid-rib was 6 feet in front of the rear tips of the cross-ribs, with no
intermediate bracing, except the light threads by which the cloth cover was
attached, it was inevitable that, should the depth be made materially greater
than the width, the rib would buckle sideways. Test ribs of I-beam form,
Page 358
which are later described, were constructed, but, although they proved
exceedingly stiff, had to be discarded.
In view of these facts the obvious remedy appeared to be to make the rib
hollow, and one cross-rib, 34 of an inch in diameter at the point where it
crossed the main rib, tapering to 58 of an inch at the front and 38 of an inch at
the rear tip, was accordingly constructed. Tests showed that this form of rib,
which was about 10 grammes lighter than the 12 -inch solid ribs, was much
stiffer than anything yet constructed. But when a wing, with cross-ribs of
this size placed 20 inches apart, was sanded it was found that, although a
great advance in construction had been made, still further improvement was
necessary before a suitable wing for the large aerodrome could be procured.
[p197]
Before proceeding with the construction of any more complete wings, an
extended series of experiments was made in order to secure ribs of proper
lightness and strength. Various forms of metal tubes were tested; but,
although aluminum seemed at one time to promise good results, it was
found that hollow ribs could be constructed of spruce which were much
stronger than aluminum tubes of the same weight. In order to determine
more accurately what mode of construction would give the greatest stiffness
and strength for a minimum weight, it was decided to make up some test
pieces of different forms before making up complete ribs. For convenience
in construction, these test pieces were made straight and shorter than the
large cross-ribs. Each piece was tested by fastening it in the testing clamp
with 1 metre of its length projecting horizontally, and attaching at its end a
weight of 1 kilogramme. The deflection from the horizontal gave an index
of the stiffness of the piece under examination.
The first test piece was a hollow square, 17 mm. length of side on the
exterior, and 11 mm. length of side on the interior, the walls thus being 3
mm. thick. This weighed 73 grammes per metre and had small internal
stiffening pieces, like the partitions in bamboo, glued into it 4 inches apart.
A weight of 1 kilogramme at the distance of 1 metre gave a deflection of 56
exceedingly stiff, had to be discarded.
In view of these facts the obvious remedy appeared to be to make the rib
hollow, and one cross-rib, 34 of an inch in diameter at the point where it
crossed the main rib, tapering to 58 of an inch at the front and 38 of an inch at
the rear tip, was accordingly constructed. Tests showed that this form of rib,
which was about 10 grammes lighter than the 12 -inch solid ribs, was much
stiffer than anything yet constructed. But when a wing, with cross-ribs of
this size placed 20 inches apart, was sanded it was found that, although a
great advance in construction had been made, still further improvement was
necessary before a suitable wing for the large aerodrome could be procured.
[p197]
Before proceeding with the construction of any more complete wings, an
extended series of experiments was made in order to secure ribs of proper
lightness and strength. Various forms of metal tubes were tested; but,
although aluminum seemed at one time to promise good results, it was
found that hollow ribs could be constructed of spruce which were much
stronger than aluminum tubes of the same weight. In order to determine
more accurately what mode of construction would give the greatest stiffness
and strength for a minimum weight, it was decided to make up some test
pieces of different forms before making up complete ribs. For convenience
in construction, these test pieces were made straight and shorter than the
large cross-ribs. Each piece was tested by fastening it in the testing clamp
with 1 metre of its length projecting horizontally, and attaching at its end a
weight of 1 kilogramme. The deflection from the horizontal gave an index
of the stiffness of the piece under examination.
The first test piece was a hollow square, 17 mm. length of side on the
exterior, and 11 mm. length of side on the interior, the walls thus being 3
mm. thick. This weighed 73 grammes per metre and had small internal
stiffening pieces, like the partitions in bamboo, glued into it 4 inches apart.
A weight of 1 kilogramme at the distance of 1 metre gave a deflection of 56
Page 359
mm. The second test piece was a duplicate of the first one, except that it had
no internal stiffening pieces, and the weight per metre was made the same,
73 grammes, as formerly, by leaving the walls a fraction thicker. The
deflection in this case was, as would be expected, exactly the same as in the
first one. The first test piece, however, was superior to the second one in
that it was stiffer against being crushed in by accident. The third test piece
was a hollow cylinder, 22 mm. outside diameter and 17 mm. inside
diameter, the walls thus being 2.5 mm. thick. The weight per metre was 91
grammes, and the deflection was 46 mm. The fourth test was made by
taking two of the original solid cross-ribs, 12 mm. in diameter, and
fastening them in the clamp side by side, with a length of 1 metre
projecting. The weight per metre for the two ribs was 105 grammes, and the
deflection produced on the two by 1 kilogramme at 1 metre distance was
115 mm. The fifth test piece was an I-beam of spruce, having a depth of 25
mm., with the flanges 12.5 mm. wide and the web 3 mm. thick. The weight
per metre was 65 grammes, and the deflection was 26 mm. All of these test
pieces were made of carefully selected straight-grained spruce.
It is readily seen that the test piece having the I-beam section weighed
less than the hollow square in the first and second tests, and had a deflection
of less than half. This I-beam section, however, did not show up so well
when a longer piece was tested, for as soon as the length was made
appreciably greater than a metre it began to twist, the twisting becoming
more and more serious the [p198] greater the length, until with a piece 11 feet
long, the full length of a cross-rib, the twisting was so serious as to make
the rib practically useless. It was at first thought that this twisting might be
overcome by making the webs slightly wider, and it would to a certain
extent, but in looking ahead and planning how the cross-ribs were to be
fastened to the main ribs, the I-beam section was seen to present so many
difficulties that it was thought hardly worth while to spend time on further
experiments with it. This decision was made all the more imperative by
foreseeing the difficulty of bending the I-beam section to the curve which
the cross-ribs were to have. In fact it had been found by experience that
while many different forms of ribs could be bent to the proper curve by
no internal stiffening pieces, and the weight per metre was made the same,
73 grammes, as formerly, by leaving the walls a fraction thicker. The
deflection in this case was, as would be expected, exactly the same as in the
first one. The first test piece, however, was superior to the second one in
that it was stiffer against being crushed in by accident. The third test piece
was a hollow cylinder, 22 mm. outside diameter and 17 mm. inside
diameter, the walls thus being 2.5 mm. thick. The weight per metre was 91
grammes, and the deflection was 46 mm. The fourth test was made by
taking two of the original solid cross-ribs, 12 mm. in diameter, and
fastening them in the clamp side by side, with a length of 1 metre
projecting. The weight per metre for the two ribs was 105 grammes, and the
deflection produced on the two by 1 kilogramme at 1 metre distance was
115 mm. The fifth test piece was an I-beam of spruce, having a depth of 25
mm., with the flanges 12.5 mm. wide and the web 3 mm. thick. The weight
per metre was 65 grammes, and the deflection was 26 mm. All of these test
pieces were made of carefully selected straight-grained spruce.
It is readily seen that the test piece having the I-beam section weighed
less than the hollow square in the first and second tests, and had a deflection
of less than half. This I-beam section, however, did not show up so well
when a longer piece was tested, for as soon as the length was made
appreciably greater than a metre it began to twist, the twisting becoming
more and more serious the [p198] greater the length, until with a piece 11 feet
long, the full length of a cross-rib, the twisting was so serious as to make
the rib practically useless. It was at first thought that this twisting might be
overcome by making the webs slightly wider, and it would to a certain
extent, but in looking ahead and planning how the cross-ribs were to be
fastened to the main ribs, the I-beam section was seen to present so many
difficulties that it was thought hardly worth while to spend time on further
experiments with it. This decision was made all the more imperative by
foreseeing the difficulty of bending the I-beam section to the curve which
the cross-ribs were to have. In fact it had been found by experience that
while many different forms of ribs could be bent to the proper curve by
Page 360
steaming and clamping them over a form and then drying them out while
still clamped to the form, yet the grain of the wood varied so in different
ribs, that of a dozen steamed and bent over the same form it was seldom
that as many as three would have approximately the same amount of
curvature when removed from the form after drying. If, however, the curve
was formed in the ribs by making them in two parts, which were glued
together and clamped up on the form while the glue dried, practically any
number could be made which would have the same curvature when thinned
down to the proper thickness of wall.
It was recognized at all times that the gluing together of the ribs not only
entailed extra work, but introduced an element of uncertainty unless some
kind of a varnish for the ribs could be found which would prevent any
possibility of the glue becoming soft from moisture in the atmosphere or
from the wings actually coming down into the water when the aerodrome
was tried in flight. A search was therefore made for a varnish that was
water-proof. A large number of different varnishes were tried, and one was
finally found which, after repeated tests, seemed to be thoroughly good.
Several test ribs were given three coats of this varnish, and were then kept
immersed in water for 24 hours without the glue showing any signs of
softening. It was therefore decided to follow the plan of gluing the ribs
together and protecting them with three coats of this varnish, which seemed
to possess the remarkable properties of being not only impervious to water,
but also unaffected by the application of concentrated ammonia or of
gasoline, either of which produces immediate softening when applied to
ordinary varnishes.
Following the indication of these tests that the hollow, round section, 22
mm. outside diameter by 17 mm. inside diameter, would probably give the
best cross-rib for the weight that it seemed possible to allow, a set of cross-
ribs of this form was constructed and put in place in the large experimental
wing, in which the former solid ribs had been tested. The wing was inverted
and fastened into two posts at the angle it would have in flight, the guy-
wires from the [p199] lower guy-posts of the aerodrome being represented by
wires stretched from the posts. In actual use on the aerodrome it was
still clamped to the form, yet the grain of the wood varied so in different
ribs, that of a dozen steamed and bent over the same form it was seldom
that as many as three would have approximately the same amount of
curvature when removed from the form after drying. If, however, the curve
was formed in the ribs by making them in two parts, which were glued
together and clamped up on the form while the glue dried, practically any
number could be made which would have the same curvature when thinned
down to the proper thickness of wall.
It was recognized at all times that the gluing together of the ribs not only
entailed extra work, but introduced an element of uncertainty unless some
kind of a varnish for the ribs could be found which would prevent any
possibility of the glue becoming soft from moisture in the atmosphere or
from the wings actually coming down into the water when the aerodrome
was tried in flight. A search was therefore made for a varnish that was
water-proof. A large number of different varnishes were tried, and one was
finally found which, after repeated tests, seemed to be thoroughly good.
Several test ribs were given three coats of this varnish, and were then kept
immersed in water for 24 hours without the glue showing any signs of
softening. It was therefore decided to follow the plan of gluing the ribs
together and protecting them with three coats of this varnish, which seemed
to possess the remarkable properties of being not only impervious to water,
but also unaffected by the application of concentrated ammonia or of
gasoline, either of which produces immediate softening when applied to
ordinary varnishes.
Following the indication of these tests that the hollow, round section, 22
mm. outside diameter by 17 mm. inside diameter, would probably give the
best cross-rib for the weight that it seemed possible to allow, a set of cross-
ribs of this form was constructed and put in place in the large experimental
wing, in which the former solid ribs had been tested. The wing was inverted
and fastened into two posts at the angle it would have in flight, the guy-
wires from the [p199] lower guy-posts of the aerodrome being represented by
wires stretched from the posts. In actual use on the aerodrome it was
Page 361
proposed to have three main guy-wires running from each of the main
cross-ribs to the lower guy-post, but in the test, which is now to be
described, the wires which would have come nearest the body of the
machine were left off to see what effect their removal would have on the
wing.
The weight and dimensions of the wing, as set up, were as follows:
Length of the main ribs, 24 feet; length of the cloth covering, 22 feet; width
of the cloth covering, 11 feet; total weight, 29 pounds. The two main ribs
(front rib and mid-rib) were solid, 3.5 cm. in diameter at butt, 2.5 cm. in
diameter at tip, and tapering from the middle to the tip. There were twelve
regular cross-ribs set 50.8 cm. (20 inches) apart, each rib being as above
described, 11 feet long, 22 mm. outside diameter by 17 mm. inside diameter
at the butt, and tapering from where they were attached to the mid-rib to the
tip, and each weighing 300 grammes. There were two extra cross-ribs, one
at the inner end next to the body of the machine and the other at the outer
end. These were solid strips of wood 3.8 cm. wide by 1.2 cm. thick, made
extra wide and stiff in order to withstand the strain of stretching the cloth
covering. There was also a thin, flat strip at the rear edge, which connected
together all the tips of the cross-ribs, holding them a uniform distance apart,
and also serving to fasten the cloth. The main mid-rib was stiffened in a
vertical direction by a system of small guy-wires drawn over short guy-
posts about 6 inches high. With the wing inverted and fastened in the way
above described, a weight of 2 kilogrammes placed at the inner rear corner
produced a deflection of 26.7 cm. When the inner rear corner was pulled up
by a spring balance until the balance registered 2 kilogrammes, there was an
upward deflection of 41.3 cm. When the main mid-rib was held at the inner
end, the pull of 2 kilogrammes, applied to the inner corner as before, caused
an upward deflection of 25.4 cm. instead of 41.3 cm. This wing was
afterwards given a sanding test under a weight of 0.7 pound per square foot.
With fine guy-wires fastened from the front of the cross-ribs to the tip and
drawn just taut, the ribs showed an average deflection of 9 inches at the tip
under the above weight. When a small wooden guy-post was added under
each of these small guy-wires, the same weight produced an average
cross-ribs to the lower guy-post, but in the test, which is now to be
described, the wires which would have come nearest the body of the
machine were left off to see what effect their removal would have on the
wing.
The weight and dimensions of the wing, as set up, were as follows:
Length of the main ribs, 24 feet; length of the cloth covering, 22 feet; width
of the cloth covering, 11 feet; total weight, 29 pounds. The two main ribs
(front rib and mid-rib) were solid, 3.5 cm. in diameter at butt, 2.5 cm. in
diameter at tip, and tapering from the middle to the tip. There were twelve
regular cross-ribs set 50.8 cm. (20 inches) apart, each rib being as above
described, 11 feet long, 22 mm. outside diameter by 17 mm. inside diameter
at the butt, and tapering from where they were attached to the mid-rib to the
tip, and each weighing 300 grammes. There were two extra cross-ribs, one
at the inner end next to the body of the machine and the other at the outer
end. These were solid strips of wood 3.8 cm. wide by 1.2 cm. thick, made
extra wide and stiff in order to withstand the strain of stretching the cloth
covering. There was also a thin, flat strip at the rear edge, which connected
together all the tips of the cross-ribs, holding them a uniform distance apart,
and also serving to fasten the cloth. The main mid-rib was stiffened in a
vertical direction by a system of small guy-wires drawn over short guy-
posts about 6 inches high. With the wing inverted and fastened in the way
above described, a weight of 2 kilogrammes placed at the inner rear corner
produced a deflection of 26.7 cm. When the inner rear corner was pulled up
by a spring balance until the balance registered 2 kilogrammes, there was an
upward deflection of 41.3 cm. When the main mid-rib was held at the inner
end, the pull of 2 kilogrammes, applied to the inner corner as before, caused
an upward deflection of 25.4 cm. instead of 41.3 cm. This wing was
afterwards given a sanding test under a weight of 0.7 pound per square foot.
With fine guy-wires fastened from the front of the cross-ribs to the tip and
drawn just taut, the ribs showed an average deflection of 9 inches at the tip
under the above weight. When a small wooden guy-post was added under
each of these small guy-wires, the same weight produced an average
Page 362
deflection of 5 inches at the tip of each rib under the same load. In a
previous test of the wing, using hollow cross-ribs 16 mm. outside diameter
by 10 mm. inside diameter at the butt, and only half as far apart as the later
ones, a load of 1 pound per square foot on the wing produced an average
deflection of 9 inches at the tip of each rib when the cross guy-wires on
each rib were held up by short guy-posts, but when these short guy-posts
were removed, the same load produced a deflection of nearly 25 inches at
the tip of each rib. [p200]
Although this wing was a great improvement in every way over any of
the previous constructions, it was felt that it was too weak for the large
aerodrome. Further experiments were therefore made in order to secure a
form of cross-rib which would meet the rigorous requirements imposed. An
inordinate amount of time was spent in the construction and tests of various
forms of rib, but as a result a satisfactory cross-rib was at last constructed of
the form shown in Plate 66, Figs. 4–8, the dimensions at the three principal
points, viz., first, where the cross-ribs join the front rib; second, where they
cross the mid-rib; and third, at the rear tip, being given both for the
intermediate cross-ribs and the end cross-ribs.
Following the plan employed by Nature in the construction of the
bamboo pole, small partitions, approximately one millimetre thick, were
placed every three inches in the thin, hollow rib to keep it from being
crushed. The partitions were glued in place when the hollow rib was glued
together on the form around which it was bent and clamped until the glue
dried. Longer blocks were also inserted in each of the intermediate ribs at
the point where it crossed the main rib and also at the front end where it
was attached to the front rib. In the end ribs blocks were also inserted at the
points where the cross-braces were fastened to them for resisting the end
stress due to the cloth covering.
Upon making up one of these ribs and testing it, it was found to possess
remarkable stiffness, so much so that it was thought probable that it was as
stiff in proportion to its size as the best thing that Nature had produced in
the bird’s wing. A large quill from the wing of a harpy eagle was therefore
stripped and the large end clamped in a special holder, and measurements
previous test of the wing, using hollow cross-ribs 16 mm. outside diameter
by 10 mm. inside diameter at the butt, and only half as far apart as the later
ones, a load of 1 pound per square foot on the wing produced an average
deflection of 9 inches at the tip of each rib when the cross guy-wires on
each rib were held up by short guy-posts, but when these short guy-posts
were removed, the same load produced a deflection of nearly 25 inches at
the tip of each rib. [p200]
Although this wing was a great improvement in every way over any of
the previous constructions, it was felt that it was too weak for the large
aerodrome. Further experiments were therefore made in order to secure a
form of cross-rib which would meet the rigorous requirements imposed. An
inordinate amount of time was spent in the construction and tests of various
forms of rib, but as a result a satisfactory cross-rib was at last constructed of
the form shown in Plate 66, Figs. 4–8, the dimensions at the three principal
points, viz., first, where the cross-ribs join the front rib; second, where they
cross the mid-rib; and third, at the rear tip, being given both for the
intermediate cross-ribs and the end cross-ribs.
Following the plan employed by Nature in the construction of the
bamboo pole, small partitions, approximately one millimetre thick, were
placed every three inches in the thin, hollow rib to keep it from being
crushed. The partitions were glued in place when the hollow rib was glued
together on the form around which it was bent and clamped until the glue
dried. Longer blocks were also inserted in each of the intermediate ribs at
the point where it crossed the main rib and also at the front end where it
was attached to the front rib. In the end ribs blocks were also inserted at the
points where the cross-braces were fastened to them for resisting the end
stress due to the cloth covering.
Upon making up one of these ribs and testing it, it was found to possess
remarkable stiffness, so much so that it was thought probable that it was as
stiff in proportion to its size as the best thing that Nature had produced in
the bird’s wing. A large quill from the wing of a harpy eagle was therefore
stripped and the large end clamped in a special holder, and measurements
Page 363
were made of the deflection produced by weights at various distances from
the clamp. As the main mid-rib of the wing of the aerodrome is placed
approximately at the point of the center of pressure, the bending action on
the cross-ribs may be assumed to act on a lever arm from the mid-rib
towards the front, and from the mid-rib towards the rear in the cases of the
pressure on the front and rear portions of the wing, respectively. In testing
these cross-ribs, therefore, against the quill, the rib was clamped at the point
where it crosses the mid-rib of the wing, and measurements were made of
the deflection produced by weights placed at various distances from the
point of clamping both front and rear.
the clamp. As the main mid-rib of the wing of the aerodrome is placed
approximately at the point of the center of pressure, the bending action on
the cross-ribs may be assumed to act on a lever arm from the mid-rib
towards the front, and from the mid-rib towards the rear in the cases of the
pressure on the front and rear portions of the wing, respectively. In testing
these cross-ribs, therefore, against the quill, the rib was clamped at the point
where it crosses the mid-rib of the wing, and measurements were made of
the deflection produced by weights placed at various distances from the
point of clamping both front and rear.
Page 364
PL. 66. DETAILS OF RIBS AND FITTINGS FOR WINGS ◊ lgr
Page 365
PL. 67. CROSS SECTION OF RIBS ◊ lgr
Page 366
The quill on which the measurements were made was 19.5 inches long
and had a gradual curve, the highest point of the curve being about the
center of the length of the quill, and the depth of curvature being about 2
inches. When the butt of this quill was placed in the clamp the tip stood 17
cm. above the horizontal. The hollow spruce rib, when clamped at a point 5
feet from the tip (the point from which it tapers in both directions) had its
tip 2.2 cm. above the horizontal, there being very little curve in that portion
of the rib. The quill weighed 4 grammes when stripped and 18 inches of it
projected from the [p201] clamp which held it during the tests. The rear
portion of the spruce rib projected 5 feet from the clamp, being thus 3.3
times as long as the quill, and it weighed 120 grammes, the weight for the
larger size having, therefore, increased slightly less than the cube of the
length.
The results of the tests of both the quill and the rib are given in the
following table. The approximate cross-section of the quill at the point of
clamping, the middle and the tip are shown in diagrams A, B and C,
respectively, of Plate 67. The cross-sections of the rib at the corresponding
points are shown in diagrams D, E and F. The cross-sections of the quill,
enlarged five times, are shown in diagrams A′, B′, and C′.
QUILL FROM THE REMIGES OF HARPY EAGLE.
Weight, 4 grammes; length, 45 cm.; tip, 17 cm. above butt when the latter is horizontal.
Point of application of weight Absolute weight in Weight in terms of Deflection in terms
in terms of length. grammes. greatest weight. of length.
0.39 1050 1.0 .38
0.445 605 0.58 .38
0.56 405 0.39 .38
0.75 210 0.20 .38
0.95 77 0.075 .38
HOLLOW SPRUCE RIB.
Weight, 120 grammes; length 153 cm.; section, rectangular; tip, 17 cm. above butt.
Point of application of weight Absolute weight in Weight in terms of Deflection in terms
in terms of length. grammes. greatest weight. of length.
0.39 15,000 1.0 .11
0.445 11,400 0.76 .11
0.56 7,900 0.53 .11
0.75 4,000 0.27 .11
0.95 2,000 0.135 .11
and had a gradual curve, the highest point of the curve being about the
center of the length of the quill, and the depth of curvature being about 2
inches. When the butt of this quill was placed in the clamp the tip stood 17
cm. above the horizontal. The hollow spruce rib, when clamped at a point 5
feet from the tip (the point from which it tapers in both directions) had its
tip 2.2 cm. above the horizontal, there being very little curve in that portion
of the rib. The quill weighed 4 grammes when stripped and 18 inches of it
projected from the [p201] clamp which held it during the tests. The rear
portion of the spruce rib projected 5 feet from the clamp, being thus 3.3
times as long as the quill, and it weighed 120 grammes, the weight for the
larger size having, therefore, increased slightly less than the cube of the
length.
The results of the tests of both the quill and the rib are given in the
following table. The approximate cross-section of the quill at the point of
clamping, the middle and the tip are shown in diagrams A, B and C,
respectively, of Plate 67. The cross-sections of the rib at the corresponding
points are shown in diagrams D, E and F. The cross-sections of the quill,
enlarged five times, are shown in diagrams A′, B′, and C′.
QUILL FROM THE REMIGES OF HARPY EAGLE.
Weight, 4 grammes; length, 45 cm.; tip, 17 cm. above butt when the latter is horizontal.
Point of application of weight Absolute weight in Weight in terms of Deflection in terms
in terms of length. grammes. greatest weight. of length.
0.39 1050 1.0 .38
0.445 605 0.58 .38
0.56 405 0.39 .38
0.75 210 0.20 .38
0.95 77 0.075 .38
HOLLOW SPRUCE RIB.
Weight, 120 grammes; length 153 cm.; section, rectangular; tip, 17 cm. above butt.
Point of application of weight Absolute weight in Weight in terms of Deflection in terms
in terms of length. grammes. greatest weight. of length.
0.39 15,000 1.0 .11
0.445 11,400 0.76 .11
0.56 7,900 0.53 .11
0.75 4,000 0.27 .11
0.95 2,000 0.135 .11
Page 367
In each case the unit of length was the portion extending beyond the
clamp; the unit of weight, the greatest weight employed to produce the
deflection. It should be noted, however, that the relative deflection was
quite different in the two comparisons. In the case of the quill the deflection
was 17 cm. in 45 cm., or 38 per cent; in the case of the rib it was 17 cm. in
153 cm., or 11 per cent. In the case of the rib at the point 0.39 the absolute
weight was 15,000 grammes, the relative weight unity and the deflection in
terms of length 0.11. While no rigorous comparison can be instituted, since
the rib was not deflected nearly as much proportionately as the quill, yet the
general inference is that while the rib was not intended to be, and was not as
elastic proportionately as the quill, it was probably at least as strong in
proportion to its weight. Briefly summarizing these results it will be noted
that the spruce rib was about 3.3 times the length and 30 times as heavy,
while it was 15 times as stiff near the butt and 26 times as stiff at the tip, as
the quill.
As this test on the rib for the large wings had apparently shown that the
plan of constructing the ribs in the form of a hollow square secured
maximum strength for minimum weight, it was decided to construct a few
sample ribs after the same plan for the wings of the new quarter-size model
of the large aerodrome, and to test, these ribs in a similar manner. The
following table shows the results of the test on one of these ribs:
Total length of rib = 80 cm. Curve = 1 in 18. Highest point of curvature = 0.25 from front.
Section of rib = 10 mm × 14 mm. at the point of attachment to mid-rib, tapering to 8 mm. × 12
mm. at the front point and to 7 mm. × 2 mm. at the tip. The rib was clamped with the tip projecting
[p202] 46 cm. and was weighted at different percentages of its length to such an extent that it was
deflected 11 per cent of its length, or 5 cm. The weight of the 46 cm. length of rib which projected
from the clamp was 11 grammes, the whole rib weighing 22 grammes and balancing on a knife
edge placed at the point where it was clamped.
Point of application of weight Absolute weight in Weight in terms of Deflection in terms
in terms of length. grammes. greatest weight. of length.
0.39 7680 1.0 0.11
0.445 5980 0.78 0.11
0.56 3680 0.48 0.11
0.75 2300 0.30 0.11
0.95 1100 0.143 0.11
1.00 930 0.121 0.11
clamp; the unit of weight, the greatest weight employed to produce the
deflection. It should be noted, however, that the relative deflection was
quite different in the two comparisons. In the case of the quill the deflection
was 17 cm. in 45 cm., or 38 per cent; in the case of the rib it was 17 cm. in
153 cm., or 11 per cent. In the case of the rib at the point 0.39 the absolute
weight was 15,000 grammes, the relative weight unity and the deflection in
terms of length 0.11. While no rigorous comparison can be instituted, since
the rib was not deflected nearly as much proportionately as the quill, yet the
general inference is that while the rib was not intended to be, and was not as
elastic proportionately as the quill, it was probably at least as strong in
proportion to its weight. Briefly summarizing these results it will be noted
that the spruce rib was about 3.3 times the length and 30 times as heavy,
while it was 15 times as stiff near the butt and 26 times as stiff at the tip, as
the quill.
As this test on the rib for the large wings had apparently shown that the
plan of constructing the ribs in the form of a hollow square secured
maximum strength for minimum weight, it was decided to construct a few
sample ribs after the same plan for the wings of the new quarter-size model
of the large aerodrome, and to test, these ribs in a similar manner. The
following table shows the results of the test on one of these ribs:
Total length of rib = 80 cm. Curve = 1 in 18. Highest point of curvature = 0.25 from front.
Section of rib = 10 mm × 14 mm. at the point of attachment to mid-rib, tapering to 8 mm. × 12
mm. at the front point and to 7 mm. × 2 mm. at the tip. The rib was clamped with the tip projecting
[p202] 46 cm. and was weighted at different percentages of its length to such an extent that it was
deflected 11 per cent of its length, or 5 cm. The weight of the 46 cm. length of rib which projected
from the clamp was 11 grammes, the whole rib weighing 22 grammes and balancing on a knife
edge placed at the point where it was clamped.
Point of application of weight Absolute weight in Weight in terms of Deflection in terms
in terms of length. grammes. greatest weight. of length.
0.39 7680 1.0 0.11
0.445 5980 0.78 0.11
0.56 3680 0.48 0.11
0.75 2300 0.30 0.11
0.95 1100 0.143 0.11
1.00 930 0.121 0.11
Page 368
A lighter rib than the above, which was constructed at the same time, was
also tested with the results shown in the following table. This rib was also
80 cm. long, but was only one-half the linear dimensions in section of the
rib previously tested. The rear portion of it projected 46 cm. from the
clamp. The total weight of the rib was 11 grammes, or 5.5 grammes for the
46 cm. on which the measurements were made.
Point of application of weight Absolute weight in Weight in terms of Deflection in terms
in terms of length. grammes. greatest weight. of length.
0.39 1400 1.0 0.11
0.445 1100 0.785 0.11
0.56 700 0.50 0.11
0.75 400 0.275 0.11
0.95 250 0.178 0.11
1.00 220 0.157 0.11
A still lighter rib of the same length, weighing 9 grammes, suitable for
use in the wings of the quarter-size model, was constructed and a set of tests
was made on it with the following results. As in the above test, 46 cm. of
the rear portion of it projected from the clamp which held it.
Point of application of weight Absolute weight in Weight in terms of Deflection in terms
in terms of length. grammes. greatest weight. of length.
0.39 1450 1.0 0.11
0.445 1150 0.795 0.11
0.56 740 0.51 0.11
0.75 380 0.262 0.11
0.95 210 0.145 0.11
1.00 180 0.124 0.11
Among quite a number of different forms of cross-ribs which were
constructed of a size suitable for use in the model aerodrome, but made
primarily for use in tests to determine the best form to employ, may be
mentioned the following, in which both ribs were seven-sixteenths of an
inch outside diameter and five-sixteenths of an inch inside diameter. One
was filled with elder pith, formed up into a round rod that just fit the
interior of the hollow rib, and was glued into it when the rib was glued up.
The other rib was left hollow. Upon testing these by suspending weights at
different points, the rib without [p203] the pith showed a slightly less
deflection than the one with it, it happening probably that the wood in one
also tested with the results shown in the following table. This rib was also
80 cm. long, but was only one-half the linear dimensions in section of the
rib previously tested. The rear portion of it projected 46 cm. from the
clamp. The total weight of the rib was 11 grammes, or 5.5 grammes for the
46 cm. on which the measurements were made.
Point of application of weight Absolute weight in Weight in terms of Deflection in terms
in terms of length. grammes. greatest weight. of length.
0.39 1400 1.0 0.11
0.445 1100 0.785 0.11
0.56 700 0.50 0.11
0.75 400 0.275 0.11
0.95 250 0.178 0.11
1.00 220 0.157 0.11
A still lighter rib of the same length, weighing 9 grammes, suitable for
use in the wings of the quarter-size model, was constructed and a set of tests
was made on it with the following results. As in the above test, 46 cm. of
the rear portion of it projected from the clamp which held it.
Point of application of weight Absolute weight in Weight in terms of Deflection in terms
in terms of length. grammes. greatest weight. of length.
0.39 1450 1.0 0.11
0.445 1150 0.795 0.11
0.56 740 0.51 0.11
0.75 380 0.262 0.11
0.95 210 0.145 0.11
1.00 180 0.124 0.11
Among quite a number of different forms of cross-ribs which were
constructed of a size suitable for use in the model aerodrome, but made
primarily for use in tests to determine the best form to employ, may be
mentioned the following, in which both ribs were seven-sixteenths of an
inch outside diameter and five-sixteenths of an inch inside diameter. One
was filled with elder pith, formed up into a round rod that just fit the
interior of the hollow rib, and was glued into it when the rib was glued up.
The other rib was left hollow. Upon testing these by suspending weights at
different points, the rib without [p203] the pith showed a slightly less
deflection than the one with it, it happening probably that the wood in one
Page 369
case was a little stiffer than in the other, although they were carefully
selected to be as nearly alike as possible. The rib with the pith in it weighed
34 grammes and the one without it weighed 30 grammes. It was inferred
from this test that the placing of a light pithy material in the interior of the
ribs would have no good effect, and would not only add weight, but also
complicate the construction. The reason for making this test with pith in one
of the ribs was that it was thought probable that the rib flattened out
somewhat when it was deflected under a load, and that the pith stiffened
with the glue with which it was fastened in, might lessen this.
As the cross-rib described above, which was tested on October 23, 1899,
seemed in every way suited for use in the wings of the large aerodrome, a
complete wing equipped with similar ribs but of slightly changed
dimensions, as shown in Plate 66, Fig. 5, was immediately constructed. As
previous tests had shown that the wing covering did not “flute” or “pocket”
to any considerable extent even when the ribs were as much as thirty inches
apart, only ten cross-ribs were used in this wing. The eight intermediate
cross-ribs were of the form described above, but the ribs at either end of the
wing were made of a larger cross-section and otherwise stiffened in order to
resist the strain of the tightly stretched cloth covering.
On April 13, 1900, a final sanding test was made on this wing, guyed in a
manner similar to that used in the aerodrome, in which the following results
were obtained:
SANDING TEST OF LARGE WING.
Area, 260 sq. ft.; weight of wing, 29 pounds; weight of sand on wing, 231 pounds; total
weight supported by wing, 260 pounds, or one pound per square foot.
Deflection of cross-rib, numbering from inner edge to extreme outer edge of wing—
Number of rib. Deflection. Inches.
1 (Heavy end rib) 5.5
2 9.5
3 11.75
4 12.25
5 12.5
6 12.75
7 12.9
8 13.0
9 12.0
10 (Heavy end rib) 9.75
selected to be as nearly alike as possible. The rib with the pith in it weighed
34 grammes and the one without it weighed 30 grammes. It was inferred
from this test that the placing of a light pithy material in the interior of the
ribs would have no good effect, and would not only add weight, but also
complicate the construction. The reason for making this test with pith in one
of the ribs was that it was thought probable that the rib flattened out
somewhat when it was deflected under a load, and that the pith stiffened
with the glue with which it was fastened in, might lessen this.
As the cross-rib described above, which was tested on October 23, 1899,
seemed in every way suited for use in the wings of the large aerodrome, a
complete wing equipped with similar ribs but of slightly changed
dimensions, as shown in Plate 66, Fig. 5, was immediately constructed. As
previous tests had shown that the wing covering did not “flute” or “pocket”
to any considerable extent even when the ribs were as much as thirty inches
apart, only ten cross-ribs were used in this wing. The eight intermediate
cross-ribs were of the form described above, but the ribs at either end of the
wing were made of a larger cross-section and otherwise stiffened in order to
resist the strain of the tightly stretched cloth covering.
On April 13, 1900, a final sanding test was made on this wing, guyed in a
manner similar to that used in the aerodrome, in which the following results
were obtained:
SANDING TEST OF LARGE WING.
Area, 260 sq. ft.; weight of wing, 29 pounds; weight of sand on wing, 231 pounds; total
weight supported by wing, 260 pounds, or one pound per square foot.
Deflection of cross-rib, numbering from inner edge to extreme outer edge of wing—
Number of rib. Deflection. Inches.
1 (Heavy end rib) 5.5
2 9.5
3 11.75
4 12.25
5 12.5
6 12.75
7 12.9
8 13.0
9 12.0
10 (Heavy end rib) 9.75
Page 370
The weight of sand put on the wing in this test was 1.5 times as great as
the pressure which at this time it was expected would be imposed upon it in
flight, and was in fact 1.2 times as great as the normal pressure when
supporting the aerodrome as finally constructed. Even under this weight the
greatest deflection noted in terms of the total length of the rib was less than
0.10, showing that the elastic limit of the rib was far from being reached.
[p204]
As this test seemed to indicate that the wings constructed in this manner
were certainly strong and rigid enough for use on the aerodrome, and that
immediate further improvement could hardly be made, three similar wings
were at once constructed to complete the set. Somewhat later two additional
wings were provided, so that when the large aerodrome was taken to
Widewater on the Potomac in 1903 one and a half complete sets of wings
were on hand, which seemed to be ample to provide for any emergencies
that might arise.
Each of these wings had, as is clearly shown in the drawings, Plates 53
and 54, two main ribs, which formed the main strength of the framework
and gave the wing longitudinal rigidity. To the main front rib were attached
the cross-ribs and the pieces for the curved extension later described. The
mid-rib extended across the cross-ribs, parallel to and about 5 feet behind
the front rib, this being approximately the line in which lay the center of
pressure of the wing. It was upon this rib, therefore, that the greatest strain
would fall.
The mid-rib, Plate 66, Fig. 2, was 731.5 cm. (24 ft.) long, having at the
butt an outer diameter of 38 mm. (1.5 in.) and an inner diameter of 25 mm.
(1 in.), the walls being, therefore, approximately 6.5 mm. (0.25 in.) thick.
From the butt to the middle point the section was uniform, but from this
point it had a taper of one-twenty-fourth of an inch to the foot, so that at the
tip it had an outer diameter of 25 mm. (1 in.), the thickness of the wall
being unchanged. At the butt end a wooden block 8 inches long was glued
inside the rib, and at uniform distances of 75 mm. (30 in.) 10 smaller blocks
were glued in where the cross-ribs were attached. The main front rib was of
the pressure which at this time it was expected would be imposed upon it in
flight, and was in fact 1.2 times as great as the normal pressure when
supporting the aerodrome as finally constructed. Even under this weight the
greatest deflection noted in terms of the total length of the rib was less than
0.10, showing that the elastic limit of the rib was far from being reached.
[p204]
As this test seemed to indicate that the wings constructed in this manner
were certainly strong and rigid enough for use on the aerodrome, and that
immediate further improvement could hardly be made, three similar wings
were at once constructed to complete the set. Somewhat later two additional
wings were provided, so that when the large aerodrome was taken to
Widewater on the Potomac in 1903 one and a half complete sets of wings
were on hand, which seemed to be ample to provide for any emergencies
that might arise.
Each of these wings had, as is clearly shown in the drawings, Plates 53
and 54, two main ribs, which formed the main strength of the framework
and gave the wing longitudinal rigidity. To the main front rib were attached
the cross-ribs and the pieces for the curved extension later described. The
mid-rib extended across the cross-ribs, parallel to and about 5 feet behind
the front rib, this being approximately the line in which lay the center of
pressure of the wing. It was upon this rib, therefore, that the greatest strain
would fall.
The mid-rib, Plate 66, Fig. 2, was 731.5 cm. (24 ft.) long, having at the
butt an outer diameter of 38 mm. (1.5 in.) and an inner diameter of 25 mm.
(1 in.), the walls being, therefore, approximately 6.5 mm. (0.25 in.) thick.
From the butt to the middle point the section was uniform, but from this
point it had a taper of one-twenty-fourth of an inch to the foot, so that at the
tip it had an outer diameter of 25 mm. (1 in.), the thickness of the wall
being unchanged. At the butt end a wooden block 8 inches long was glued
inside the rib, and at uniform distances of 75 mm. (30 in.) 10 smaller blocks
were glued in where the cross-ribs were attached. The main front rib was of
Page 371
the same form and size, except that it was some 2 inches shorter and had no
blocks, except the long one at the butt, glued in it.
To these main ribs were attached, in the manner later described, the 10
cross-ribs, to which the cloth cover was attached. The 8 intermediate cross-
ribs have already been described in connection with the tests. The cross-ribs
at the end of the wings, upon which greater lateral strains would come from
the stretching of the cloth, were made of the larger cross-section shown in
Fig. 8 of Plate 66. Additional longitudinal stiffness was provided by gluing
a strip 2 mm. thick between the upper and lower halves, as shown in the
section. These end ribs, as well as those next to the ends, had small blocks
glued into them where they were crossed by the diagonal braces, in addition
to the small partitions 1 mm. thick, which were glued into the ribs every 3
inches to prevent crushing, and the blocks 2.5 and 3 inches long
respectively, where they were attached to the front rib and to the mid-rib. At
the extreme rear edge of the wing the cross-ribs were attached to the small
“D”-rib, which served to hold the ribs at equal distances and to keep the
cloth cover stretched tight. This “D”-rib, as shown in Plate 66, Fig. 3, had
semi-circular walls 4 mm. thick, 21 mm. in diameter, to the edge of which
was glued a flat strip 3 mm. thick. [p205]
As originally designed the wings had a curve of only 1 in 18, the main
front rib forming the leading edge of the wing. Later, however, it seemed
desirable to “quicken” the curve and at the same time give the wing a
sharper leading edge. This was accomplished by attaching to the front rib, at
the points where the cross-ribs joined it, properly curved wooden pieces of
the form shown in Plate 66, Fig. 10, over which the cloth cover of the wing
was stretched. The curve of the wing after the addition of this extension is
shown in Plate 66, Fig. 4, and was a curve having a rise of approximately 1
in 12, with the highest point .25 from the front end.
On account of the large size of these wings and the consequent difficulty
in handling them it was necessary to construct them in such a manner that
they could be easily taken apart, rolled up, transported to the house-boat or
any other point where they might need to be used, and then quickly
reassembled. After much experiment as to the best means of constructing
blocks, except the long one at the butt, glued in it.
To these main ribs were attached, in the manner later described, the 10
cross-ribs, to which the cloth cover was attached. The 8 intermediate cross-
ribs have already been described in connection with the tests. The cross-ribs
at the end of the wings, upon which greater lateral strains would come from
the stretching of the cloth, were made of the larger cross-section shown in
Fig. 8 of Plate 66. Additional longitudinal stiffness was provided by gluing
a strip 2 mm. thick between the upper and lower halves, as shown in the
section. These end ribs, as well as those next to the ends, had small blocks
glued into them where they were crossed by the diagonal braces, in addition
to the small partitions 1 mm. thick, which were glued into the ribs every 3
inches to prevent crushing, and the blocks 2.5 and 3 inches long
respectively, where they were attached to the front rib and to the mid-rib. At
the extreme rear edge of the wing the cross-ribs were attached to the small
“D”-rib, which served to hold the ribs at equal distances and to keep the
cloth cover stretched tight. This “D”-rib, as shown in Plate 66, Fig. 3, had
semi-circular walls 4 mm. thick, 21 mm. in diameter, to the edge of which
was glued a flat strip 3 mm. thick. [p205]
As originally designed the wings had a curve of only 1 in 18, the main
front rib forming the leading edge of the wing. Later, however, it seemed
desirable to “quicken” the curve and at the same time give the wing a
sharper leading edge. This was accomplished by attaching to the front rib, at
the points where the cross-ribs joined it, properly curved wooden pieces of
the form shown in Plate 66, Fig. 10, over which the cloth cover of the wing
was stretched. The curve of the wing after the addition of this extension is
shown in Plate 66, Fig. 4, and was a curve having a rise of approximately 1
in 12, with the highest point .25 from the front end.
On account of the large size of these wings and the consequent difficulty
in handling them it was necessary to construct them in such a manner that
they could be easily taken apart, rolled up, transported to the house-boat or
any other point where they might need to be used, and then quickly
reassembled. After much experiment as to the best means of constructing
Page 372
them, the following plan was devised. The cloth covering was permanently
fastened to the front rib, to which were attached the front extension pieces
by means of small metal clips secured by small wood screws. On the rear
edge of the front main rib, at a uniform distance of 30 inches apart, 10 small
metal horns of 1-mm. tubing, 5 cm. long, each brazed to an independent
clamping thimble, as shown in Fig. 9 of Plate 66, were fastened. The front
end of each of the cross-ribs was slightly rounded out to fit the front main
rib, and in the wooden block which was glued in this end of the cross-rib a
hole was bored to fit these horns. Each of the cross-ribs was then pushed
over its proper horn and against the front main rib, and the cloth covering
then drawn back toward the rear tips of the cross-ribs. In the extreme rear
edge of the cloth covering a seam was made, and in this was inserted the
“D”-rib already described. The cloth was then tightly stretched and a wood
screw forced through the “D”-rib and into and through the metal ferrule at
the tip of the cross-rib. Near the inner and outer edges of the cloth covering
eyelets were placed about 6 inches apart, through which small cords were
then inserted and tied to the end cross-ribs. The main or mid-rib was then
placed on top of the cross-ribs and fastened to them with wood screws, and
the cross-braces were then fastened on the top of the wing, as shown in
Plate 54. The frame of the wing was stiffened horizontally by cross guy-
wires which passed from each cross-rib, at the point where the mid-rib
crossed it, to the adjoining cross-rib, at the point where it was connected to
the front rib. Each of the main ribs was individually guyed, in the manner
clearly shown in Plate 52, in order to stiffen it in the vertical direction, the
fittings for these guy-wires being shown in detail in Figs. 11–15 of Plate 66.
Finally, small guy-wires were run from the front end of the cross-ribs over a
guy-post 12 inches high at the point where the cross-rib crossed the mid-rib
to the rear tip of the cross-rib. These cross guy-wires were regulated in [p206]
tightness by raising and lowering a screw in the slot of the head of which
they rested, and which was threaded in the end of the small guy-post. Upper
and lower guy-wires, running from the main ribs to the guy-posts on the
aerodrome, as already described, and as is clearly shown in the drawings,
Plates 52 and 54, completed the guy-wire system for the wings, except for
fastened to the front rib, to which were attached the front extension pieces
by means of small metal clips secured by small wood screws. On the rear
edge of the front main rib, at a uniform distance of 30 inches apart, 10 small
metal horns of 1-mm. tubing, 5 cm. long, each brazed to an independent
clamping thimble, as shown in Fig. 9 of Plate 66, were fastened. The front
end of each of the cross-ribs was slightly rounded out to fit the front main
rib, and in the wooden block which was glued in this end of the cross-rib a
hole was bored to fit these horns. Each of the cross-ribs was then pushed
over its proper horn and against the front main rib, and the cloth covering
then drawn back toward the rear tips of the cross-ribs. In the extreme rear
edge of the cloth covering a seam was made, and in this was inserted the
“D”-rib already described. The cloth was then tightly stretched and a wood
screw forced through the “D”-rib and into and through the metal ferrule at
the tip of the cross-rib. Near the inner and outer edges of the cloth covering
eyelets were placed about 6 inches apart, through which small cords were
then inserted and tied to the end cross-ribs. The main or mid-rib was then
placed on top of the cross-ribs and fastened to them with wood screws, and
the cross-braces were then fastened on the top of the wing, as shown in
Plate 54. The frame of the wing was stiffened horizontally by cross guy-
wires which passed from each cross-rib, at the point where the mid-rib
crossed it, to the adjoining cross-rib, at the point where it was connected to
the front rib. Each of the main ribs was individually guyed, in the manner
clearly shown in Plate 52, in order to stiffen it in the vertical direction, the
fittings for these guy-wires being shown in detail in Figs. 11–15 of Plate 66.
Finally, small guy-wires were run from the front end of the cross-ribs over a
guy-post 12 inches high at the point where the cross-rib crossed the mid-rib
to the rear tip of the cross-rib. These cross guy-wires were regulated in [p206]
tightness by raising and lowering a screw in the slot of the head of which
they rested, and which was threaded in the end of the small guy-post. Upper
and lower guy-wires, running from the main ribs to the guy-posts on the
aerodrome, as already described, and as is clearly shown in the drawings,
Plates 52 and 54, completed the guy-wire system for the wings, except for
Page 373
the “drift wires,” which for the front wings were run from the lower side of
the mid-rib to the bowsprit at the front of the machine, and for the rear
wings to the main frame.
Each wing when completely assembled weighed approximately 29
pounds, and had a rectangular surface 22.5 by 11.5 feet (measured on the
chord of the curve), or 260 square feet, making the weight per square foot
equal about 50 grammes, rather less than 1.5 times as much per square foot
as the wings for the steam-driven models. The total supporting surface of
the aerodrome was 1040 square feet, and as the aerodrome when equipped
for flight weighed, including the aviator, 850 pounds this gave 1.22 square
feet to the pound, or 0.82 pound to the square foot. Although this was a
somewhat larger proportion of weight to supporting surface than it had
originally been expected to have, there is every reason to believe that it was
sufficient, for the quarter-size model, when weighted so that it had 1.22
square feet to the pound, flew well, as will later appear.
the mid-rib to the bowsprit at the front of the machine, and for the rear
wings to the main frame.
Each wing when completely assembled weighed approximately 29
pounds, and had a rectangular surface 22.5 by 11.5 feet (measured on the
chord of the curve), or 260 square feet, making the weight per square foot
equal about 50 grammes, rather less than 1.5 times as much per square foot
as the wings for the steam-driven models. The total supporting surface of
the aerodrome was 1040 square feet, and as the aerodrome when equipped
for flight weighed, including the aviator, 850 pounds this gave 1.22 square
feet to the pound, or 0.82 pound to the square foot. Although this was a
somewhat larger proportion of weight to supporting surface than it had
originally been expected to have, there is every reason to believe that it was
sufficient, for the quarter-size model, when weighted so that it had 1.22
square feet to the pound, flew well, as will later appear.
Page 374
[p207] ◊
CHAPTER VII
EQUILIBRIUM AND CONTROL
In an aerodrome it is essential not only that its component parts shall be
so disposed that the initial equilibrium is correct and highly stable, but also
that some efficient means be provided for quickly and accurately restoring
the equilibrium, if for any reason it is disturbed. If the aerodrome is of
sufficient size and power to carry a human being it is, of course, possible
merely to supply an efficient means of controlling the lateral and horizontal
equilibrium of the machine and depend upon the intelligence and skill of
the operator, as developed by practice and experience, to maintain the
proper equilibrium of the machine while in the air. This method, however, is
open to the objection that no matter how skilled the aviator may be there
remains the probability of a serious if not fatal accident as the result of any
momentary lapse or diversion of attention until the “sense of equilibrium”
has been developed. One of the chief problems, therefore, which had
impressed itself from the beginning of the work, was to devise some means
by which the equilibrium of the aerodrome would be automatically
maintained under the varying conditions of flight, so as to leave the aviator
free, as far as possible, to control the direction of flight and to devote his
attention to other important matters connected with the proper functioning
of the various parts of the aerodrome. In the development of the models it
had been absolutely necessary to develop some efficient automatic control,
as they were far too small to carry an aviator, and the conditions of flight in
the open air, even on the calmest day, were such that constant readjustments
of the equilibrium were necessary. The success attained in the automatic
control of the equilibrium of the models had been so great, and so much
time would have been required for an aviator to acquire skill sufficient to
control a machine without such automatic equilibrium, that it was
considered both expedient and safe to embody in the large aerodrome the
plans which had proved so successful in the models. It was necessary,
CHAPTER VII
EQUILIBRIUM AND CONTROL
In an aerodrome it is essential not only that its component parts shall be
so disposed that the initial equilibrium is correct and highly stable, but also
that some efficient means be provided for quickly and accurately restoring
the equilibrium, if for any reason it is disturbed. If the aerodrome is of
sufficient size and power to carry a human being it is, of course, possible
merely to supply an efficient means of controlling the lateral and horizontal
equilibrium of the machine and depend upon the intelligence and skill of
the operator, as developed by practice and experience, to maintain the
proper equilibrium of the machine while in the air. This method, however, is
open to the objection that no matter how skilled the aviator may be there
remains the probability of a serious if not fatal accident as the result of any
momentary lapse or diversion of attention until the “sense of equilibrium”
has been developed. One of the chief problems, therefore, which had
impressed itself from the beginning of the work, was to devise some means
by which the equilibrium of the aerodrome would be automatically
maintained under the varying conditions of flight, so as to leave the aviator
free, as far as possible, to control the direction of flight and to devote his
attention to other important matters connected with the proper functioning
of the various parts of the aerodrome. In the development of the models it
had been absolutely necessary to develop some efficient automatic control,
as they were far too small to carry an aviator, and the conditions of flight in
the open air, even on the calmest day, were such that constant readjustments
of the equilibrium were necessary. The success attained in the automatic
control of the equilibrium of the models had been so great, and so much
time would have been required for an aviator to acquire skill sufficient to
control a machine without such automatic equilibrium, that it was
considered both expedient and safe to embody in the large aerodrome the
plans which had proved so successful in the models. It was necessary,
Page 375
however, to provide in addition in the large machine means whereby the
aviator could quickly and accurately either modify the action of the
automatic devices or, if desired, entirely supersede the automatic control by
purely manual control. Three distinct problems were, therefore, encountered
in connection with the equilibrium and control of the large aerodrome. In
the first place, the machine as a whole had to be so designed, and its
component parts so disposed as to secure a highly stable initial equilibrium;
second, automatic means had to be provided for [p208] maintaining this
equilibrium under the varying conditions of flight and for restoring it if for
any reason it was disturbed, and, finally, provision had to be made for the
quick and accurate control of the flight by the aviator. These problems,
while intimately related, had to be met one by one and solved separately.
The general type of machine adopted was that which had been developed
in the years of experiment with the steam-driven models. From the very
first consideration of the large aerodrome, it seemed advisable to follow this
type, which not only had shown itself to be distinguished by remarkable
longitudinal and lateral stability in the tests, but was actually the only type
in the world which had at that time shown any possibility of successful
flight. There was, of course, a question whether single surface or
superposed wings would be used, and in spite of the negative results
obtained in the tests of the models with the superposed wings, it was felt
that a considerable field for development was open in this direction.
However, in spite of the advantages which theoretical considerations
showed might be obtained through the introduction of this and various other
modifications of the original type, the whole teaching of past experience in
the construction of the model aerodromes had been that success was more
certain to be achieved by following the course in which genuine practical
results had been achieved. It was decided, therefore, that in the construction
of the large aerodrome the design should follow as closely as constructional
conditions would permit the lines of the successful model Aerodromes Nos.
5 and 6, which have already been fully described.
The longitudinal stability of an aerodrome is largely dependent upon the
relation of three chief factors; the center of pressure, the center of gravity
aviator could quickly and accurately either modify the action of the
automatic devices or, if desired, entirely supersede the automatic control by
purely manual control. Three distinct problems were, therefore, encountered
in connection with the equilibrium and control of the large aerodrome. In
the first place, the machine as a whole had to be so designed, and its
component parts so disposed as to secure a highly stable initial equilibrium;
second, automatic means had to be provided for [p208] maintaining this
equilibrium under the varying conditions of flight and for restoring it if for
any reason it was disturbed, and, finally, provision had to be made for the
quick and accurate control of the flight by the aviator. These problems,
while intimately related, had to be met one by one and solved separately.
The general type of machine adopted was that which had been developed
in the years of experiment with the steam-driven models. From the very
first consideration of the large aerodrome, it seemed advisable to follow this
type, which not only had shown itself to be distinguished by remarkable
longitudinal and lateral stability in the tests, but was actually the only type
in the world which had at that time shown any possibility of successful
flight. There was, of course, a question whether single surface or
superposed wings would be used, and in spite of the negative results
obtained in the tests of the models with the superposed wings, it was felt
that a considerable field for development was open in this direction.
However, in spite of the advantages which theoretical considerations
showed might be obtained through the introduction of this and various other
modifications of the original type, the whole teaching of past experience in
the construction of the model aerodromes had been that success was more
certain to be achieved by following the course in which genuine practical
results had been achieved. It was decided, therefore, that in the construction
of the large aerodrome the design should follow as closely as constructional
conditions would permit the lines of the successful model Aerodromes Nos.
5 and 6, which have already been fully described.
The longitudinal stability of an aerodrome is largely dependent upon the
relation of three chief factors; the center of pressure, the center of gravity
Page 376
and the line of thrust. For an aerodrome of the “Langley” type, the relative
positions of these which give the greatest degree of stability had been
determined as far as possible through the years of experiment with the
models. However, while it is the usual experience in designing machinery,
or even scientific apparatus, that what appears theoretically to be the best
plan has to be considerably modified for constructional reasons, yet in the
design of an aerodrome this is particularly true, for not only must all the
various parts function properly, both separately and as a whole, but this
result must be secured for the very minimum of weight. Experience alone
can enable one to appreciate thoroughly how seriously this consideration of
weight complicates the problem.
In making the original designs for the large aerodrome it had been
recognized that the relative positions of the line of thrust, center of pressure,
and center of gravity were much better in model No. 6 than in model No. 5.
From Data Sheet No. 1, for Aerodrome No. 5 when it made its flight on
May 6, 1896, it will be noted that the line of thrust being assumed to be at
the point 1500,43 [p209] the center of gravity was at the point 1497, and that,
assuming the rear wings to have two-thirds of the lifting effect of the front
ones, the center of pressure was calculated to be at the point 1498, or one
centimetre in front of the center of gravity, measured in the horizontal
plane. In the vertical plane the center of pressure was calculated to be at the
point 2536, and the center of gravity was found by test to be at the point
2501, when the line of thrust was assumed to be at the point 2500, the
center of gravity being actually one centimetre above the line of thrust.
From the data sheet of Aerodrome No. 6, for its flight of November 28,
1896, it will be noted that the line of thrust being at the point 1500 the
center of pressure was at the point 1487, and the center of gravity at the
point 1484; that is, the center of pressure was three centimeters in front of
the center of gravity, measured in the horizontal plane. In the vertical plane,
taking the line of thrust at the point 2500, the center of pressure was at the
point 2525, and the center of gravity at the point 2486, the center of gravity
being 14 centimetres below the line of thrust and 39 centimetres below the
center of pressure, the distance from the center of pressure to the line of
positions of these which give the greatest degree of stability had been
determined as far as possible through the years of experiment with the
models. However, while it is the usual experience in designing machinery,
or even scientific apparatus, that what appears theoretically to be the best
plan has to be considerably modified for constructional reasons, yet in the
design of an aerodrome this is particularly true, for not only must all the
various parts function properly, both separately and as a whole, but this
result must be secured for the very minimum of weight. Experience alone
can enable one to appreciate thoroughly how seriously this consideration of
weight complicates the problem.
In making the original designs for the large aerodrome it had been
recognized that the relative positions of the line of thrust, center of pressure,
and center of gravity were much better in model No. 6 than in model No. 5.
From Data Sheet No. 1, for Aerodrome No. 5 when it made its flight on
May 6, 1896, it will be noted that the line of thrust being assumed to be at
the point 1500,43 [p209] the center of gravity was at the point 1497, and that,
assuming the rear wings to have two-thirds of the lifting effect of the front
ones, the center of pressure was calculated to be at the point 1498, or one
centimetre in front of the center of gravity, measured in the horizontal
plane. In the vertical plane the center of pressure was calculated to be at the
point 2536, and the center of gravity was found by test to be at the point
2501, when the line of thrust was assumed to be at the point 2500, the
center of gravity being actually one centimetre above the line of thrust.
From the data sheet of Aerodrome No. 6, for its flight of November 28,
1896, it will be noted that the line of thrust being at the point 1500 the
center of pressure was at the point 1487, and the center of gravity at the
point 1484; that is, the center of pressure was three centimeters in front of
the center of gravity, measured in the horizontal plane. In the vertical plane,
taking the line of thrust at the point 2500, the center of pressure was at the
point 2525, and the center of gravity at the point 2486, the center of gravity
being 14 centimetres below the line of thrust and 39 centimetres below the
center of pressure, the distance from the center of pressure to the line of
Page 377
thrust being, therefore, 64 per cent of the distance between the center of
pressure and the center of gravity.
As has been explained in Part I, while it is not desirable that the center of
gravity be a great distance below the center of pressure, as such a relation
tends to produce a special kind of rolling and pitching in varying currents of
air, it is highly desirable that the center of gravity should lie some distance
below the line of thrust in order that the three forces may be balanced. In a
machine like model No. 5, where the center of gravity was actually, though
very slightly above the line of thrust, there is a constant tendency to
produce rotation of the aerodrome, if for any reason its equilibrium is
disturbed, which is corrected in practice by the action of the Pénaud tail. In
model No. 6, on the other hand, the disposition of the three factors was such
that they tended to maintain, rather than to destroy, the initial equilibrium of
the machine.
These desirable relative positions had been made possible in model No. 6
by the fact that the center of gravity and line of thrust could be located at
practically any desired point, since with the use of steam the power plant
consists of two separable parts, the boiler, with its fuel and water tanks, and
the engine. These parts can, therefore, be placed in any part of the
aerodrome that constructional or theoretical reasons demand. Furthermore,
the engine constitutes such a relatively small portion of the weight of the
entire machine that, if for any reason it is desirable to place the engine in
the same plane as the line of thrust, its weight is not sufficient to alter
materially the position of the center of gravity, since the boiler, water and
fuel tanks can be placed as low as desirable and connected with the engine
by suitable pipes. [p210]
With a gasoline engine, however, the conditions are very greatly altered.
Here the engine constitutes practically the entire weight of the power plant,
only such accessories as the ignition coil, batteries, and carburetor being
available for lowering the center of gravity, unless the fuel, cooling water
tanks and radiator be placed below the engine and the liquids forced up by
means of a pump. In making the first designs for the large aerodrome,
therefore, it was found that it would be practically impossible to make the
pressure and the center of gravity.
As has been explained in Part I, while it is not desirable that the center of
gravity be a great distance below the center of pressure, as such a relation
tends to produce a special kind of rolling and pitching in varying currents of
air, it is highly desirable that the center of gravity should lie some distance
below the line of thrust in order that the three forces may be balanced. In a
machine like model No. 5, where the center of gravity was actually, though
very slightly above the line of thrust, there is a constant tendency to
produce rotation of the aerodrome, if for any reason its equilibrium is
disturbed, which is corrected in practice by the action of the Pénaud tail. In
model No. 6, on the other hand, the disposition of the three factors was such
that they tended to maintain, rather than to destroy, the initial equilibrium of
the machine.
These desirable relative positions had been made possible in model No. 6
by the fact that the center of gravity and line of thrust could be located at
practically any desired point, since with the use of steam the power plant
consists of two separable parts, the boiler, with its fuel and water tanks, and
the engine. These parts can, therefore, be placed in any part of the
aerodrome that constructional or theoretical reasons demand. Furthermore,
the engine constitutes such a relatively small portion of the weight of the
entire machine that, if for any reason it is desirable to place the engine in
the same plane as the line of thrust, its weight is not sufficient to alter
materially the position of the center of gravity, since the boiler, water and
fuel tanks can be placed as low as desirable and connected with the engine
by suitable pipes. [p210]
With a gasoline engine, however, the conditions are very greatly altered.
Here the engine constitutes practically the entire weight of the power plant,
only such accessories as the ignition coil, batteries, and carburetor being
available for lowering the center of gravity, unless the fuel, cooling water
tanks and radiator be placed below the engine and the liquids forced up by
means of a pump. In making the first designs for the large aerodrome,
therefore, it was found that it would be practically impossible to make the
Page 378
relative positions of the center of gravity and line of thrust the same as had
existed in model No. 6, however desirable it might be. The center of gravity
could be brought appreciably lower than the line of thrust only by placing
the gasoline engine in a plane considerably below that of the propellers, and
this necessitated the addition of at least two more sets of gears with heavy
bearings and braces. Besides this almost prohibitive factor of weight, it was
also foreseen that great difficulty would be experienced in keeping even the
two sets of bevel gears already necessary aligned and in proper condition
for efficiently transmitting the power to the propellers unless the frame and
other parts were made prohibitively heavy. It was, therefore, found
necessary to bring the center of gravity practically in the same plane with
the line of thrust, which made its general features as regards equilibrium
more nearly resemble those of model No. 5 than of No. 6.
The weight of the aviator, it is true, constituted an appreciable part of the
flying weight of the large machine, and it at first seemed possible to lower
the center of gravity by placing him at a considerable distance below the
line of thrust. But it was recognized from the beginning that the aviator
would probably have to give a great deal of attention to any form of engine
in order to insure its working properly, and his position must, therefore, be
selected with a view to the proper supervision of the engine and without
regard to its effect on the center of gravity.
Although the repeated successful flights of model No. 5 under varying
conditions of wind and power inspired the belief that the minor
adjustments, as well as the general plan of the large aerodrome, were such
as to give highly stable equilibrium, nevertheless, more direct corroboration
of this opinion was desired, and it was largely for this reason that the
quarter-size model was constructed. In it every detail of the larger machine
which in any way affected its equilibrium was exactly reproduced to scale,
and the greatest care was taken that the same relative positions of the center
of pressure, the center of gravity and the line of thrust which it was
proposed to employ for the large aerodrome should be used on the model in
its flight of August 8, 1903, which is later described. The entire success of
this flight, so far as the balancing was concerned, in spite of the fact that the
existed in model No. 6, however desirable it might be. The center of gravity
could be brought appreciably lower than the line of thrust only by placing
the gasoline engine in a plane considerably below that of the propellers, and
this necessitated the addition of at least two more sets of gears with heavy
bearings and braces. Besides this almost prohibitive factor of weight, it was
also foreseen that great difficulty would be experienced in keeping even the
two sets of bevel gears already necessary aligned and in proper condition
for efficiently transmitting the power to the propellers unless the frame and
other parts were made prohibitively heavy. It was, therefore, found
necessary to bring the center of gravity practically in the same plane with
the line of thrust, which made its general features as regards equilibrium
more nearly resemble those of model No. 5 than of No. 6.
The weight of the aviator, it is true, constituted an appreciable part of the
flying weight of the large machine, and it at first seemed possible to lower
the center of gravity by placing him at a considerable distance below the
line of thrust. But it was recognized from the beginning that the aviator
would probably have to give a great deal of attention to any form of engine
in order to insure its working properly, and his position must, therefore, be
selected with a view to the proper supervision of the engine and without
regard to its effect on the center of gravity.
Although the repeated successful flights of model No. 5 under varying
conditions of wind and power inspired the belief that the minor
adjustments, as well as the general plan of the large aerodrome, were such
as to give highly stable equilibrium, nevertheless, more direct corroboration
of this opinion was desired, and it was largely for this reason that the
quarter-size model was constructed. In it every detail of the larger machine
which in any way affected its equilibrium was exactly reproduced to scale,
and the greatest care was taken that the same relative positions of the center
of pressure, the center of gravity and the line of thrust which it was
proposed to employ for the large aerodrome should be used on the model in
its flight of August 8, 1903, which is later described. The entire success of
this flight, so far as the balancing was concerned, in spite of the fact that the
Page 379
engine worked erratically and that the launching speed was much less than
it should have been, removed every doubt [p211] that the equilibrium of the
large aerodrome would be satisfactory under normal conditions.
The second problem encountered in connection with the balancing and
control of the large aerodrome was that of providing an efficient means for
maintaining the equilibrium under varying atmospheric conditions.
Although much had been done toward the solution of this problem in the
development of the models, the whole question was reopened and
thoroughly reconsidered in designing the large aerodrome. The Pénaud tail,
when made elastic or when more or less rigid, but attached to the frame
through an elastic connection, and normally set at a negative angle,
furnishes a means of automatically controlling the equilibrium, which is
sufficiently sensitive and accurate to enable a machine to fly for a
considerable distance, at least in moderately calm weather, as is evidenced
by the various flights of the model aerodromes, where there was no human
intelligence to control them. But owing to the principle of action of the
Pénaud tail, the flight of an aerodrome controlled by it must of necessity be
more or less undulatory in its course. Furthermore, the tests with the models
had indicated that, while the Pénaud tail served remarkably well as a means
of controlling the equilibrium of the machine, provided the balancing had
been rather accurately determined, and, further, provided nothing happened
to affect seriously the equilibrium of the machine, it was limited in its
effectiveness by its narrow range of action. It was thought that a control
mechanism which should be more sensitive and at the same time should act
more powerfully to prevent the upsetting of the equilibrium when the
machine was subjected to rather strong disturbing forces was desirable for
any machine which was to transport a human being and, therefore, involved
the risk of a fatal accident.
In the earlier period of the work and before the correct application of the
Pénaud tail to the model aerodromes had been found, Mr. Langley had
planned a large number of different forms of automatic control for
preserving the equilibrium of the machines. The more frequently recurring
of these were devices for changing the angle of the wings or tail, and others
it should have been, removed every doubt [p211] that the equilibrium of the
large aerodrome would be satisfactory under normal conditions.
The second problem encountered in connection with the balancing and
control of the large aerodrome was that of providing an efficient means for
maintaining the equilibrium under varying atmospheric conditions.
Although much had been done toward the solution of this problem in the
development of the models, the whole question was reopened and
thoroughly reconsidered in designing the large aerodrome. The Pénaud tail,
when made elastic or when more or less rigid, but attached to the frame
through an elastic connection, and normally set at a negative angle,
furnishes a means of automatically controlling the equilibrium, which is
sufficiently sensitive and accurate to enable a machine to fly for a
considerable distance, at least in moderately calm weather, as is evidenced
by the various flights of the model aerodromes, where there was no human
intelligence to control them. But owing to the principle of action of the
Pénaud tail, the flight of an aerodrome controlled by it must of necessity be
more or less undulatory in its course. Furthermore, the tests with the models
had indicated that, while the Pénaud tail served remarkably well as a means
of controlling the equilibrium of the machine, provided the balancing had
been rather accurately determined, and, further, provided nothing happened
to affect seriously the equilibrium of the machine, it was limited in its
effectiveness by its narrow range of action. It was thought that a control
mechanism which should be more sensitive and at the same time should act
more powerfully to prevent the upsetting of the equilibrium when the
machine was subjected to rather strong disturbing forces was desirable for
any machine which was to transport a human being and, therefore, involved
the risk of a fatal accident.
In the earlier period of the work and before the correct application of the
Pénaud tail to the model aerodromes had been found, Mr. Langley had
planned a large number of different forms of automatic control for
preserving the equilibrium of the machines. The more frequently recurring
of these were devices for changing the angle of the wings or tail, and others
Page 380
for shifting the wings or tail bodily so as to shift the position of the center
of pressure with respect to the center of gravity, the motive power for
operating the devices being in some cases that derived from a gyroscope or
a pendulum, and in others small electric motor apparatus controlled by a
pendulum or a gyroscope. Most of these, however, never reached the stage
of development where they were actually tried on the machines in flight, as
the tests of some of them in the shop showed that they were unreliable,
while others were abandoned either when partly built or when only the
drawings for them had been made. Among the better-preserved models of
devices for this purpose which were in existence when the writer became
associated with the work are those shown in Plate 68, [p212] where the piece
at the top is a pendulum (inverted or direct) which controls the movement
of the horizontal tail by means of the cords and apparatus shown, actuating
these through the small electro magnets and apparatus attached. Just below
the rod, which represents a piece of the midrod, are three parts, the first of
which is a group of six little batteries clustered in a circle, while next to it is
a system of needles hung in gymbals, with electro-steering apparatus in
cups which itself turns on a graduated base, these electric connections,
together with the battery, controlling the vertical rudder. On the right of this
is another piece of apparatus for actuating windlass cylinders which turn
one way or the other as the contact is made by one side or the other of the
pendulum or the needle. At the bottom, on the two rods, is a tail-piece
which automatically throws the center of pressure forward or backward
according as the aerodrome departs one way or the other from the
horizontal.
In spite of the fact that all the early attempts of Mr. Langley to devise
such a mechanical control had been very unsatisfactory, the idea that
something of this kind was necessary had never really been abandoned by
him. Here was to be seen one of his chief characteristics, which was never
to abandon any idea that seemed valuable until it was brought to a
successful issue or some very strong proof was developed that the idea was
impracticable. While on a trip abroad during the summer of 1899, and
especially while resting at Vallombrosa, Italy, Mr. Langley’s mind again
of pressure with respect to the center of gravity, the motive power for
operating the devices being in some cases that derived from a gyroscope or
a pendulum, and in others small electric motor apparatus controlled by a
pendulum or a gyroscope. Most of these, however, never reached the stage
of development where they were actually tried on the machines in flight, as
the tests of some of them in the shop showed that they were unreliable,
while others were abandoned either when partly built or when only the
drawings for them had been made. Among the better-preserved models of
devices for this purpose which were in existence when the writer became
associated with the work are those shown in Plate 68, [p212] where the piece
at the top is a pendulum (inverted or direct) which controls the movement
of the horizontal tail by means of the cords and apparatus shown, actuating
these through the small electro magnets and apparatus attached. Just below
the rod, which represents a piece of the midrod, are three parts, the first of
which is a group of six little batteries clustered in a circle, while next to it is
a system of needles hung in gymbals, with electro-steering apparatus in
cups which itself turns on a graduated base, these electric connections,
together with the battery, controlling the vertical rudder. On the right of this
is another piece of apparatus for actuating windlass cylinders which turn
one way or the other as the contact is made by one side or the other of the
pendulum or the needle. At the bottom, on the two rods, is a tail-piece
which automatically throws the center of pressure forward or backward
according as the aerodrome departs one way or the other from the
horizontal.
In spite of the fact that all the early attempts of Mr. Langley to devise
such a mechanical control had been very unsatisfactory, the idea that
something of this kind was necessary had never really been abandoned by
him. Here was to be seen one of his chief characteristics, which was never
to abandon any idea that seemed valuable until it was brought to a
successful issue or some very strong proof was developed that the idea was
impracticable. While on a trip abroad during the summer of 1899, and
especially while resting at Vallombrosa, Italy, Mr. Langley’s mind again
Page 381
turned to this problem, and he wrote a number of very interesting letters
emphasizing the importance of devising such a mechanism which should be
controlled by gravity. When he returned to the Institution in the fall he
insisted upon the same idea.
emphasizing the importance of devising such a mechanism which should be
controlled by gravity. When he returned to the Institution in the fall he
insisted upon the same idea.
Page 382
PL. 68. AUTOMATIC EQUILIBRIUM DEVICES ◊
Page 383
F IG. 1 F IG. 2
PL. 69. MECHANISM OF CONTROL ◊ lgr
A mechanism which had been devised by the writer for another, but
somewhat similar, purpose seemed to be well adapted to this end, and it was
accordingly decided to construct a small model of such a size as would be
suitable for use on one of the steam-driven models. The plan of control
which it was proposed to follow was to have some mechanism which would
control the angle of the tail through the action of gravity on a pendulum
bob. Since it would require an exceedingly heavy pendulum should the
deflections of it be directly utilized to produce corresponding movements of
the tail, the most feasible plan seemed to be to have a light pendulum,
which, while free to move under the action of gravity, would nevertheless
by its movement cause some outside force to produce corresponding and
simultaneous movements of the tail. The general scheme of arrangement is
shown in Plate 69, Figs. 1 and 2. This device consists essentially of a
cylinder (1) in which is mounted a piston with the piston rod (3) passing
through the cylinder head and connected to the cord (5) which passes over
the pulley (6), fastened to the tube (2), which is slidably mounted on the
midrod (7), whence it is carried over the pulley (8) on the guy-post (9).
From here it is connected to the spring (10) which is fastened by the [p213]
PL. 69. MECHANISM OF CONTROL ◊ lgr
A mechanism which had been devised by the writer for another, but
somewhat similar, purpose seemed to be well adapted to this end, and it was
accordingly decided to construct a small model of such a size as would be
suitable for use on one of the steam-driven models. The plan of control
which it was proposed to follow was to have some mechanism which would
control the angle of the tail through the action of gravity on a pendulum
bob. Since it would require an exceedingly heavy pendulum should the
deflections of it be directly utilized to produce corresponding movements of
the tail, the most feasible plan seemed to be to have a light pendulum,
which, while free to move under the action of gravity, would nevertheless
by its movement cause some outside force to produce corresponding and
simultaneous movements of the tail. The general scheme of arrangement is
shown in Plate 69, Figs. 1 and 2. This device consists essentially of a
cylinder (1) in which is mounted a piston with the piston rod (3) passing
through the cylinder head and connected to the cord (5) which passes over
the pulley (6), fastened to the tube (2), which is slidably mounted on the
midrod (7), whence it is carried over the pulley (8) on the guy-post (9).
From here it is connected to the spring (10) which is fastened by the [p213]
Page 384
bridle (11) to the upper side of the Pénaud tail (12). The other end of the
piston rod (3) passes through the head in the other end of the cylinder, and
has connected to it a cord (14) which passes over the pulley (15) fastened to
the tube (2), whence it is continued over the pulley (16) and is joined to the
spring (17), which is connected by the bridle (18) to the lower side of the
tail. Mounted on top of the cylinder (1) is a valve chamber (20) having ports
leading to the two ends of the cylinder. Mounted in the valve chamber is a
rocking valve surrounded by a bushing having ports in it, and to which is
fastened a rod (25) which passes through the said valve and the head of the
valve chamber. Fastened to the rod (25) of the bushing is a lever (26),
which by means of the link (27) is connected to the piston rod (3). Fastened
to the rocking valve is a rod (28) which telescopes over the rod (25) and
also passes through the same head of the valve chamber, and carries at its
outer end a pendulum (29) on the lower end of which is the bob (30).
If steam or any other fluid under pressure is furnished to the valve
chamber through the pipe (31), none will be admitted to the cylinder so
long as the pendulum is vertical or at right angles to the axis of the cylinder;
and the tail will be in its normal position, which we will suppose to be an
upward inclination of five degrees. If, now, the front of the machine be
depressed, thereby causing the pendulum to move to the right, such
movement of the pendulum will cause the valve to open, admitting fluid to
the left-hand end of the cylinder. This, acting on the piston, will force it
towards the right, which, by means of the cord, will cause the angle of the
tail to be increased, thereby causing the rear of the machine to be depressed
and the front to be raised. But as soon as the piston begins to move under
the action of the fluid pressure it simultaneously moves the bushing which
surrounds the valve by means of the connecting links and levers, so that as
soon as the piston has moved a distance proportional to the amount that the
valve has been opened by the pendulum, it causes the bushing to shut off
the port and thus prevents further fluid entering the cylinder. As soon as the
aerodrome responds to the action of the tail the pendulum will, of course,
begin to move back to its normal position of perpendicularity to the
cylinder, and will then open the valve to the other port, thereby causing
piston rod (3) passes through the head in the other end of the cylinder, and
has connected to it a cord (14) which passes over the pulley (15) fastened to
the tube (2), whence it is continued over the pulley (16) and is joined to the
spring (17), which is connected by the bridle (18) to the lower side of the
tail. Mounted on top of the cylinder (1) is a valve chamber (20) having ports
leading to the two ends of the cylinder. Mounted in the valve chamber is a
rocking valve surrounded by a bushing having ports in it, and to which is
fastened a rod (25) which passes through the said valve and the head of the
valve chamber. Fastened to the rod (25) of the bushing is a lever (26),
which by means of the link (27) is connected to the piston rod (3). Fastened
to the rocking valve is a rod (28) which telescopes over the rod (25) and
also passes through the same head of the valve chamber, and carries at its
outer end a pendulum (29) on the lower end of which is the bob (30).
If steam or any other fluid under pressure is furnished to the valve
chamber through the pipe (31), none will be admitted to the cylinder so
long as the pendulum is vertical or at right angles to the axis of the cylinder;
and the tail will be in its normal position, which we will suppose to be an
upward inclination of five degrees. If, now, the front of the machine be
depressed, thereby causing the pendulum to move to the right, such
movement of the pendulum will cause the valve to open, admitting fluid to
the left-hand end of the cylinder. This, acting on the piston, will force it
towards the right, which, by means of the cord, will cause the angle of the
tail to be increased, thereby causing the rear of the machine to be depressed
and the front to be raised. But as soon as the piston begins to move under
the action of the fluid pressure it simultaneously moves the bushing which
surrounds the valve by means of the connecting links and levers, so that as
soon as the piston has moved a distance proportional to the amount that the
valve has been opened by the pendulum, it causes the bushing to shut off
the port and thus prevents further fluid entering the cylinder. As soon as the
aerodrome responds to the action of the tail the pendulum will, of course,
begin to move back to its normal position of perpendicularity to the
cylinder, and will then open the valve to the other port, thereby causing
Page 385
fluid to pass into the opposite end of the cylinder. This fluid acting on the
piston will move it in the opposite direction and thereby cause the tail to be
drawn back to its normal position at the same time that the pendulum
gradually reaches its normal position, owing to the return of the aerodrome
to its normal position. In the explanation given above it was assumed that
the slidable tube (2) was in a fixed position. It was planned to have the
equilibrium normally maintained automatically and at the same time permit
the operator to modify the automatic control and even to assume full
manual control. To secure this, the slidable tube (2) was connected at each
end to an [p214] endless cord (20) which after passing over suitable pulleys
was connected to the control wheel (51) at the aviator’s car.
A model of this device was constructed in the spring of 1900 and was
tested with steam pressure in the shop. The test showed that the device
acted immediately and with precision, the piston performing movements
simultaneously and in exact accordance with the pendulum. The device,
however, was never tried in a flight of any of the aerodromes owing to the
lack of time necessary to properly install it on the machine. Furthermore, it
was thought probable that the rapid acceleration of the aerodrome at the
moment of launching would so disturb the pendulum as to cause it to be in a
very different position from that of vertical, and also that the motion of the
aerodrome through the air would itself be a somewhat disturbing factor.
Because of the difficulties involved in this or any other mechanical
device for controlling the equilibrium, it was in every way advisable to
retain in the large machine the Pénaud system, which, though itself
imperfect in many ways, had been thoroughly tested in actual flight. In the
models, it will be remembered, the combined Pénaud tail and rudder
controlled the longitudinal equilibrium by movement in the vertical plane
under the combined influence of its initial negative angle and the elasticity
of its connection with the frame, the flight being kept as nearly as possible
in a straight line by the vertical surfaces of the tail. Although it was
necessary that the large aerodrome should be capable of being steered in a
horizontal direction, it was felt to be unwise to give the combined Pénaud
tail and rudder motion in the horizontal plane in order to attain this end,
piston will move it in the opposite direction and thereby cause the tail to be
drawn back to its normal position at the same time that the pendulum
gradually reaches its normal position, owing to the return of the aerodrome
to its normal position. In the explanation given above it was assumed that
the slidable tube (2) was in a fixed position. It was planned to have the
equilibrium normally maintained automatically and at the same time permit
the operator to modify the automatic control and even to assume full
manual control. To secure this, the slidable tube (2) was connected at each
end to an [p214] endless cord (20) which after passing over suitable pulleys
was connected to the control wheel (51) at the aviator’s car.
A model of this device was constructed in the spring of 1900 and was
tested with steam pressure in the shop. The test showed that the device
acted immediately and with precision, the piston performing movements
simultaneously and in exact accordance with the pendulum. The device,
however, was never tried in a flight of any of the aerodromes owing to the
lack of time necessary to properly install it on the machine. Furthermore, it
was thought probable that the rapid acceleration of the aerodrome at the
moment of launching would so disturb the pendulum as to cause it to be in a
very different position from that of vertical, and also that the motion of the
aerodrome through the air would itself be a somewhat disturbing factor.
Because of the difficulties involved in this or any other mechanical
device for controlling the equilibrium, it was in every way advisable to
retain in the large machine the Pénaud system, which, though itself
imperfect in many ways, had been thoroughly tested in actual flight. In the
models, it will be remembered, the combined Pénaud tail and rudder
controlled the longitudinal equilibrium by movement in the vertical plane
under the combined influence of its initial negative angle and the elasticity
of its connection with the frame, the flight being kept as nearly as possible
in a straight line by the vertical surfaces of the tail. Although it was
necessary that the large aerodrome should be capable of being steered in a
horizontal direction, it was felt to be unwise to give the combined Pénaud
tail and rudder motion in the horizontal plane in order to attain this end,
Page 386
since the use of it for such a double function might very seriously interfere
with its proper action in preserving the longitudinal stability. It was,
therefore, at first thought best to dissociate the rudder and tail so that the
rudder might be used for horizontal steering without in any way interfering
with the proper functioning of the tail. But, as the main desideratum was to
obtain a flight of the large machine as soon as possible, and perfection of
steering control seemed secondary, it was decided, after further
consideration, in order not to risk the unpredictable effects that might result
from small changes, to duplicate on the large machine the combined Pénaud
tail and rudder of the model, and to add another rudder for steering in the
horizontal plane. Constructional requirements determined as the only
available position for this rudder a rather disadvantageous one. As will be
seen from Plate 53, its efficiency was diminished by its being only about
half as far from the center of gravity as the combined Pénaud tail and
rudder, and by being located in the lee of a considerable portion of the
frame, where it would be subject to the cross-currents of air created by the
forward motion of the frame. [p215]
For the preservation of the equilibrium of the aerodrome, though the
aviator might assist by such slight movements as he was able to make in the
limited space of the aviator’s car, the main reliance was upon the Pénaud
tail. But, in the absence of any data for determining the effect produced in
passing from the model to the large machine, it could not be certain that
calculations based upon the balancing of the model would accurately
determine the proper balancing of the large machine. It was therefore
decided to provide such attachment for the Pénaud tail that, while it would
always have elastic connection with the main frame, yet its angle could be
appreciably changed without affecting in any way the degree of elasticity of
this connection. After many changes in plans for securing this result, it was
finally decided to arrange it in the manner shown in the drawings. Referring
to the general plans in Plates 53 and 54, and to the details in Fig. 1 of Plate
56, the main stem of the Pénaud tail is seen to be connected by a pin to the
horn (17), which is brazed to the clamping thimble, by which it is mounted
on the vertical tube (16), suitably connected and braced to the rear end of
with its proper action in preserving the longitudinal stability. It was,
therefore, at first thought best to dissociate the rudder and tail so that the
rudder might be used for horizontal steering without in any way interfering
with the proper functioning of the tail. But, as the main desideratum was to
obtain a flight of the large machine as soon as possible, and perfection of
steering control seemed secondary, it was decided, after further
consideration, in order not to risk the unpredictable effects that might result
from small changes, to duplicate on the large machine the combined Pénaud
tail and rudder of the model, and to add another rudder for steering in the
horizontal plane. Constructional requirements determined as the only
available position for this rudder a rather disadvantageous one. As will be
seen from Plate 53, its efficiency was diminished by its being only about
half as far from the center of gravity as the combined Pénaud tail and
rudder, and by being located in the lee of a considerable portion of the
frame, where it would be subject to the cross-currents of air created by the
forward motion of the frame. [p215]
For the preservation of the equilibrium of the aerodrome, though the
aviator might assist by such slight movements as he was able to make in the
limited space of the aviator’s car, the main reliance was upon the Pénaud
tail. But, in the absence of any data for determining the effect produced in
passing from the model to the large machine, it could not be certain that
calculations based upon the balancing of the model would accurately
determine the proper balancing of the large machine. It was therefore
decided to provide such attachment for the Pénaud tail that, while it would
always have elastic connection with the main frame, yet its angle could be
appreciably changed without affecting in any way the degree of elasticity of
this connection. After many changes in plans for securing this result, it was
finally decided to arrange it in the manner shown in the drawings. Referring
to the general plans in Plates 53 and 54, and to the details in Fig. 1 of Plate
56, the main stem of the Pénaud tail is seen to be connected by a pin to the
horn (17), which is brazed to the clamping thimble, by which it is mounted
on the vertical tube (16), suitably connected and braced to the rear end of
Page 387
the midrod, the horn (17) being larger than the stem of the tail and set at an
angle to the vertical tube (16), the pin connection permitting the tail to
swing up and down. The bridle (40), connected to the center of the tail on
its upper side, passes upward where it is connected to the spring (41), the
other end of which is connected to a single wire rope (42), which passes
over the pulley mounted on the top of the post (43), which is guyed to the
upper guy-post by the wire (44). The wire rope (42), after passing over the
pulley, is connected to the spring (45), around the two ends of which it
forms a loop, and from there it passes down to the plane of the main frame
and through suitable pulley blocks to the aviator’s control wheel (50),
which is mounted on the starboard side of the main frame, convenient to the
aviator’s right hand when he is facing forward. From this point the wire
rope passes through the various pulley blocks towards the rear of the
machine, and through the pulley block (46) mounted on the side and near
the bottom of the rear lower guy-post. At a short distance beyond this pulley
it is connected to a weaker spring (47), the other end of which is connected
by a second bridle (48) to the under side of the Pénaud tail at its center. In
order to prevent the springs (41), (45) and (47), which furnish the elasticity
for the Pénaud-tail connection, from being strained beyond their elastic
limit, either by a sudden gust of wind or by the aviator attempting to move
so large an area of surface too suddenly, the wire rope (42) was made
continuous around the springs, the portion between the points where it was
joined to the two ends of the springs being made of such a length as to take
the entire strain should the strain on the cord become greater than sufficient
to stretch the springs 50 per cent of their original length. [p216]
In the construction of the equilibrium control wheel it was decided that
some arrangement must be secured whereby the wheel would normally be
inactive and maintain whatever position it had been set to, and at the same
time could be moved by the aviator with one hand, the mere act of grasping
it rendering it free to be moved, and whereby it must automatically lock
itself in any position in which it might be when the aviator removed his
hand from it. The multiplicity of things requiring the attention of the aviator
made it desirable that his attention to any one of the important details,
angle to the vertical tube (16), the pin connection permitting the tail to
swing up and down. The bridle (40), connected to the center of the tail on
its upper side, passes upward where it is connected to the spring (41), the
other end of which is connected to a single wire rope (42), which passes
over the pulley mounted on the top of the post (43), which is guyed to the
upper guy-post by the wire (44). The wire rope (42), after passing over the
pulley, is connected to the spring (45), around the two ends of which it
forms a loop, and from there it passes down to the plane of the main frame
and through suitable pulley blocks to the aviator’s control wheel (50),
which is mounted on the starboard side of the main frame, convenient to the
aviator’s right hand when he is facing forward. From this point the wire
rope passes through the various pulley blocks towards the rear of the
machine, and through the pulley block (46) mounted on the side and near
the bottom of the rear lower guy-post. At a short distance beyond this pulley
it is connected to a weaker spring (47), the other end of which is connected
by a second bridle (48) to the under side of the Pénaud tail at its center. In
order to prevent the springs (41), (45) and (47), which furnish the elasticity
for the Pénaud-tail connection, from being strained beyond their elastic
limit, either by a sudden gust of wind or by the aviator attempting to move
so large an area of surface too suddenly, the wire rope (42) was made
continuous around the springs, the portion between the points where it was
joined to the two ends of the springs being made of such a length as to take
the entire strain should the strain on the cord become greater than sufficient
to stretch the springs 50 per cent of their original length. [p216]
In the construction of the equilibrium control wheel it was decided that
some arrangement must be secured whereby the wheel would normally be
inactive and maintain whatever position it had been set to, and at the same
time could be moved by the aviator with one hand, the mere act of grasping
it rendering it free to be moved, and whereby it must automatically lock
itself in any position in which it might be when the aviator removed his
hand from it. The multiplicity of things requiring the attention of the aviator
made it desirable that his attention to any one of the important details,
Page 388
whether the engine, the equilibrium, or the steering, should never require
more than one hand, thus leaving the other hand free either to hold on to the
machine or to control some other detail at the same time. While an
irreversible wheel, such as would be secured by the use of a worm and
worm-wheel, at first seemed likely to answer the purpose, yet the
movement of a worm-wheel by means of a worm is necessarily very slow if
it is irreversible, and it here seemed desirable to so arrange the wheel that in
case of emergency, of for rising or descending, the aviator could swing the
Pénaud tail from its extreme upper position to its extreme lower one by a
small motion of his hand, and thus small or large adjustments of the Pénaud
tail could be intuitively felt to have been produced without the aviator
having to remember how many turns he had made of the wheel.
The control of the steering rudder was effected by a steering wheel (51)
similar in construction to the equilibrium control wheel (50), a continuous
cord (52) passing from the steering wheel through suitable pulleys to either
side of the steering rudder (r ), springs being interposed in loops in the cord
on either side of the steering rudder to give some elasticity to the control
apparatus in order to prevent possible danger from the aviator attempting to
move the rudder too suddenly. This steering rope passed directly through
the steering rudder at the points where it was joined to it; so that, should
one side of the cord in any way become entangled with the frame or with its
pulleys, the strain produced by the aviator in attempting to move it in the
opposite direction would be taken up by the cord and thereby avoid the
possibility of destroying the rudder. For even should the cord become
entangled on one side, the rudder could be given a slight amount of
adjustment through the elasticity of the coiled springs.
The design of the combined Pénaud tail and rudder followed very closely
that which had been used for the models, and its area of ninety-five square
feet on the horizontal surface with a corresponding area of vertical surface
bore the same relation to the area of the tail and rudder of the models that
the area of the wings of the large machine bore to that of the wings of its
prototype.
more than one hand, thus leaving the other hand free either to hold on to the
machine or to control some other detail at the same time. While an
irreversible wheel, such as would be secured by the use of a worm and
worm-wheel, at first seemed likely to answer the purpose, yet the
movement of a worm-wheel by means of a worm is necessarily very slow if
it is irreversible, and it here seemed desirable to so arrange the wheel that in
case of emergency, of for rising or descending, the aviator could swing the
Pénaud tail from its extreme upper position to its extreme lower one by a
small motion of his hand, and thus small or large adjustments of the Pénaud
tail could be intuitively felt to have been produced without the aviator
having to remember how many turns he had made of the wheel.
The control of the steering rudder was effected by a steering wheel (51)
similar in construction to the equilibrium control wheel (50), a continuous
cord (52) passing from the steering wheel through suitable pulleys to either
side of the steering rudder (r ), springs being interposed in loops in the cord
on either side of the steering rudder to give some elasticity to the control
apparatus in order to prevent possible danger from the aviator attempting to
move the rudder too suddenly. This steering rope passed directly through
the steering rudder at the points where it was joined to it; so that, should
one side of the cord in any way become entangled with the frame or with its
pulleys, the strain produced by the aviator in attempting to move it in the
opposite direction would be taken up by the cord and thereby avoid the
possibility of destroying the rudder. For even should the cord become
entangled on one side, the rudder could be given a slight amount of
adjustment through the elasticity of the coiled springs.
The design of the combined Pénaud tail and rudder followed very closely
that which had been used for the models, and its area of ninety-five square
feet on the horizontal surface with a corresponding area of vertical surface
bore the same relation to the area of the tail and rudder of the models that
the area of the wings of the large machine bore to that of the wings of its
prototype.
Page 389
While the provisions for automatic equilibrium and manual control were
not entirely ideal, even for the quiet atmospheric conditions under which it
[p217] was proposed to make the first tests, nevertheless it was and still is
believed that the provisions for such conditions were sufficient to enable a
successful flight of a few miles to be obtained. It was thought to be very
certain that, once a successful flight could be made, the funds for the further
prosecution of the work would be readily forthcoming, and that when these
funds were obtained the many problems of control, rising and alighting,
could be undertaken.
not entirely ideal, even for the quiet atmospheric conditions under which it
[p217] was proposed to make the first tests, nevertheless it was and still is
believed that the provisions for such conditions were sufficient to enable a
successful flight of a few miles to be obtained. It was thought to be very
certain that, once a successful flight could be made, the funds for the further
prosecution of the work would be readily forthcoming, and that when these
funds were obtained the many problems of control, rising and alighting,
could be undertaken.
Page 390
[p218] ◊
CHAPTER VIII
THE EXPERIMENTAL ENGINE
It will be recalled that the contract for the engine for the large aerodrome,
which had been entered into on December 12, 1898, called for its
completion on February 28, 1899. Between the time when the engine
should have been completed and May, 1900, the engine builder had been
engaged in a continuous series of changes on it, all connected with what
might be briefly called its proper functioning. The actual mechanical
construction of the more important parts had been admirably executed, and
this main portion of the constructional work had been completed within the
time called for by the contract. The trouble was that the engine, which was
of the rotary cylinder type, would not furnish anything like the power which
had been expected of it, and which the size and number of its cylinders
indicated that it should furnish. No one who has not had practical
experience in the development of gasoline engines, can understand or
appreciate how fourteen months could be spent in changes in the minor
details of the engine with the expectation that each contemplated change
would bring success; and to anyone who has had experience in the matter,
an attempt to explain the delays would merely seem like a history of his
own experiences. It is, therefore, sufficient to say that the delay on the
engine had now reached a point where it was necessary to bring it to a
successful completion immediately or to abandon it definitely, and either
find a competent builder who had already built engines which, while not
necessarily light, were successful, and who would undertake to construct a
light one on the same principles, or, as a last resort, to turn to steam; and
even the contemplation of this was appalling.
On May 6, 1900, the writer went to New York to see what could be done
towards assisting the engine builder to complete the large engine and also,
if possible, the small one which had been ordered for the quarter-size model
later described. He immediately made brake tests of the engine to determine
CHAPTER VIII
THE EXPERIMENTAL ENGINE
It will be recalled that the contract for the engine for the large aerodrome,
which had been entered into on December 12, 1898, called for its
completion on February 28, 1899. Between the time when the engine
should have been completed and May, 1900, the engine builder had been
engaged in a continuous series of changes on it, all connected with what
might be briefly called its proper functioning. The actual mechanical
construction of the more important parts had been admirably executed, and
this main portion of the constructional work had been completed within the
time called for by the contract. The trouble was that the engine, which was
of the rotary cylinder type, would not furnish anything like the power which
had been expected of it, and which the size and number of its cylinders
indicated that it should furnish. No one who has not had practical
experience in the development of gasoline engines, can understand or
appreciate how fourteen months could be spent in changes in the minor
details of the engine with the expectation that each contemplated change
would bring success; and to anyone who has had experience in the matter,
an attempt to explain the delays would merely seem like a history of his
own experiences. It is, therefore, sufficient to say that the delay on the
engine had now reached a point where it was necessary to bring it to a
successful completion immediately or to abandon it definitely, and either
find a competent builder who had already built engines which, while not
necessarily light, were successful, and who would undertake to construct a
light one on the same principles, or, as a last resort, to turn to steam; and
even the contemplation of this was appalling.
On May 6, 1900, the writer went to New York to see what could be done
towards assisting the engine builder to complete the large engine and also,
if possible, the small one which had been ordered for the quarter-size model
later described. He immediately made brake tests of the engine to determine
Page 391
accurately just what effects were being produced by the different changes
the engine builder was making. Upon the first test the engine was found to
develop only 2.83 horse-power, and this could not be maintained for more
than a few minutes, when without any apparent cause and without any signs
of overheating the engine would altogether cease to develop any power.
After remaining in New York for several weeks, during which time many
changes were made in the engine, he finally got it to the point where it
would develop four horse-power continuously; but, as it seemed impossible
to get any better results [p219] without an indefinite amount of experiment, it
was decided that all hope of making this engine an immediate success
would have to be abandoned.
Interest in the development of the automobile was increasing at a rapid
rate all over the world, and while the builders in this country had not
reached the stage of development which had been attained in Europe,
especially in France, yet some American builders had succeeded in
constructing cars propelled by gasoline engines which could be depended
upon to run at least a short distance, and it was, therefore, hoped that some
one of the more competent of these builders might be found who would
undertake to construct a suitable engine. After making a most extensive but
fruitless search for such a builder in this country, it was decided that it
would be best to see what could be done in Europe, and as other
administrative matters made it necessary for Mr. Langley to go to Europe
about the middle of June, the writer accompanied him to see what could be
done towards having a suitable engine built there. Some six weeks were
spent in visiting all the important builders of gasoline engines in Europe,
and the results were very discouraging. Everywhere the builders said that
they did not care to undertake the work, and that they did not consider it
possible to construct an engine of 12 horse-power weighing less than 100 to
150 kilograms (220 to 330 lbs.), or that, if they had thought it possible, they
would already have built it, as they had had numerous inquiries for such
engines, and also wanted them for their own use. The last hope of securing
a suitable gasoline engine seemed to have vanished.
the engine builder was making. Upon the first test the engine was found to
develop only 2.83 horse-power, and this could not be maintained for more
than a few minutes, when without any apparent cause and without any signs
of overheating the engine would altogether cease to develop any power.
After remaining in New York for several weeks, during which time many
changes were made in the engine, he finally got it to the point where it
would develop four horse-power continuously; but, as it seemed impossible
to get any better results [p219] without an indefinite amount of experiment, it
was decided that all hope of making this engine an immediate success
would have to be abandoned.
Interest in the development of the automobile was increasing at a rapid
rate all over the world, and while the builders in this country had not
reached the stage of development which had been attained in Europe,
especially in France, yet some American builders had succeeded in
constructing cars propelled by gasoline engines which could be depended
upon to run at least a short distance, and it was, therefore, hoped that some
one of the more competent of these builders might be found who would
undertake to construct a suitable engine. After making a most extensive but
fruitless search for such a builder in this country, it was decided that it
would be best to see what could be done in Europe, and as other
administrative matters made it necessary for Mr. Langley to go to Europe
about the middle of June, the writer accompanied him to see what could be
done towards having a suitable engine built there. Some six weeks were
spent in visiting all the important builders of gasoline engines in Europe,
and the results were very discouraging. Everywhere the builders said that
they did not care to undertake the work, and that they did not consider it
possible to construct an engine of 12 horse-power weighing less than 100 to
150 kilograms (220 to 330 lbs.), or that, if they had thought it possible, they
would already have built it, as they had had numerous inquiries for such
engines, and also wanted them for their own use. The last hope of securing
a suitable gasoline engine seemed to have vanished.
Page 392
But, discouraging as was the refusal of the engine builders of Europe to
undertake to build the engine, and still more so their opinion that such an
engine was an impossibility, inspection of the engines exhibited at the Paris
Exposition had so strengthened the writer’s conviction of the possibility of
the undertaking that, before parting with Mr. Langley on August 3 to return
to America, he personally assumed the responsibility of building an engine
which would meet the requirements.
Upon returning from Europe on August 13, and finding that the engine
builder in New York had made no progress whatever towards improving the
engine during his absence, the writer condemned both the large engine and
the small one. The engine builder had practically bankrupted himself in his
attempts to construct these two engines, having spent something like $8000
or $10,000 in actual wages over and above the contract prices for the
engines, to say nothing of remuneration for his own time or such expenses
as shop rent and power. As all of the money for the large machine and
practically all for the small one had been advanced to him at various times
to assist him over financial stringencies—such advances, however, having
been secured by suitable bonds—it was decided to take the various parts of
the two engines in [p220] payment for the money which had been advanced,
as it was hoped that some of the parts of the engines might prove of use in
experimental work.
Immediately after the writer’s return to Washington he began work on the
development of an engine. Taking some of the parts of the engine which
had been condemned and constructing others, he was able by September 18
to have an experimental engine at work which, while not water-jacketed,
but provisionally cooled by wrapping wet cloths around the cylinders,
developed 18 12 horse-power on the Prony brake at 715 R. P. M., the engine,
including these wet cloths, weighing 108 pounds. Of course these wet
cloths sufficed to keep the engine cool for only a short time—three to four
minutes being the maximum. This was only a temporary expedient for
enabling the engine to run for a sufficient time to make brake tests and
determine the power it developed, but the results obtained were so very
undertake to build the engine, and still more so their opinion that such an
engine was an impossibility, inspection of the engines exhibited at the Paris
Exposition had so strengthened the writer’s conviction of the possibility of
the undertaking that, before parting with Mr. Langley on August 3 to return
to America, he personally assumed the responsibility of building an engine
which would meet the requirements.
Upon returning from Europe on August 13, and finding that the engine
builder in New York had made no progress whatever towards improving the
engine during his absence, the writer condemned both the large engine and
the small one. The engine builder had practically bankrupted himself in his
attempts to construct these two engines, having spent something like $8000
or $10,000 in actual wages over and above the contract prices for the
engines, to say nothing of remuneration for his own time or such expenses
as shop rent and power. As all of the money for the large machine and
practically all for the small one had been advanced to him at various times
to assist him over financial stringencies—such advances, however, having
been secured by suitable bonds—it was decided to take the various parts of
the two engines in [p220] payment for the money which had been advanced,
as it was hoped that some of the parts of the engines might prove of use in
experimental work.
Immediately after the writer’s return to Washington he began work on the
development of an engine. Taking some of the parts of the engine which
had been condemned and constructing others, he was able by September 18
to have an experimental engine at work which, while not water-jacketed,
but provisionally cooled by wrapping wet cloths around the cylinders,
developed 18 12 horse-power on the Prony brake at 715 R. P. M., the engine,
including these wet cloths, weighing 108 pounds. Of course these wet
cloths sufficed to keep the engine cool for only a short time—three to four
minutes being the maximum. This was only a temporary expedient for
enabling the engine to run for a sufficient time to make brake tests and
determine the power it developed, but the results obtained were so very
Page 393
encouraging that it was decided to make water jackets for the cylinders of
this engine and see what power it would then develop for more extended
periods.
This experimental engine, which was merely a “patched-up” affair, was
first equipped with a sparking arrangement built on the wiping-contact
principle. With this sparking arrangement several important difficulties
presented themselves, among which may be particularly mentioned the
great difficulty of so adjusting the sparking arrangements that the explosion
in each cylinder occurred at exactly the same point in its cycle that the
explosions occurred in all the other cylinders, it being necessary to secure
this result to a reasonably accurate degree in order to cause the engine to
run smoothly enough to be used in the aerodrome. Where an engine has a
large and heavy fly-wheel running at a high rate of speed, the nicety of
adjustment of the sparking arrangement is not so essential, for the fly-wheel
acts as a reservoir of energy and tends to smooth out the rough and jerky
impulses which would be otherwise introduced by slight variations in the
force of the explosions in the cylinders. In constructing an engine for an
aerodrome, however, the permissible weight of the engine is so very small
that the use of a fly-wheel having sufficient weight to act as an energy
reservoir is practically prohibited. Another serious difficulty which was
encountered with the wiping-contact type of sparking arrangement was that
of keeping the stuffing boxes around the rotating contact rods tight enough
to prevent leakage, without at the same time binding and causing excessive
friction. Although it seemed probable that the difficulties which have been
mentioned, and other minor ones which were apparent, could be remedied
by further experiment, yet the high tension or “jump-spark” type of
sparking apparatus seemed to offer much greater advantages. Since it had
fewer moving parts, and furthermore since the wiping-contact sparking
arrangement would have to be considerably modified in order to permit the
construction of water jackets around the cylinders, it was decided to
construct a [p221] new sparking arrangement for the engine on the jump-
spark principle. After introducing this change in the engine it was found to
this engine and see what power it would then develop for more extended
periods.
This experimental engine, which was merely a “patched-up” affair, was
first equipped with a sparking arrangement built on the wiping-contact
principle. With this sparking arrangement several important difficulties
presented themselves, among which may be particularly mentioned the
great difficulty of so adjusting the sparking arrangements that the explosion
in each cylinder occurred at exactly the same point in its cycle that the
explosions occurred in all the other cylinders, it being necessary to secure
this result to a reasonably accurate degree in order to cause the engine to
run smoothly enough to be used in the aerodrome. Where an engine has a
large and heavy fly-wheel running at a high rate of speed, the nicety of
adjustment of the sparking arrangement is not so essential, for the fly-wheel
acts as a reservoir of energy and tends to smooth out the rough and jerky
impulses which would be otherwise introduced by slight variations in the
force of the explosions in the cylinders. In constructing an engine for an
aerodrome, however, the permissible weight of the engine is so very small
that the use of a fly-wheel having sufficient weight to act as an energy
reservoir is practically prohibited. Another serious difficulty which was
encountered with the wiping-contact type of sparking arrangement was that
of keeping the stuffing boxes around the rotating contact rods tight enough
to prevent leakage, without at the same time binding and causing excessive
friction. Although it seemed probable that the difficulties which have been
mentioned, and other minor ones which were apparent, could be remedied
by further experiment, yet the high tension or “jump-spark” type of
sparking apparatus seemed to offer much greater advantages. Since it had
fewer moving parts, and furthermore since the wiping-contact sparking
arrangement would have to be considerably modified in order to permit the
construction of water jackets around the cylinders, it was decided to
construct a [p221] new sparking arrangement for the engine on the jump-
spark principle. After introducing this change in the engine it was found to
Page 394
run very much more smoothly and to require a minimum amount of care in
adjusting it.
At the time that this engine was being developed it was practically
impossible to obtain any outside information regarding the proper way of
constructing it. The little that was then known had been learned through
laborious experience and at great cost by the experimenters who were
attempting to build automobiles, and was zealously guarded in the hope of
preventing their rivals from utilizing the results of their labors. It was the
known custom, however, of all engine builders at this time to use a separate
spark coil and a separate contact maker for each cylinder of an engine, no
matter how many cylinders there were. This multiplication of the spark
coils, which at that time were very heavy, not only added greatly to the
weight but also had the same defect that the wipe-spark type of sparking
arrangement had of being exceedingly difficult to so adjust that all of the
contact makers would perform their functions at exactly the same point in
the cycle for each cylinder. To obviate these difficulties, both of adjustment
and of excessive weight, the writer devised what is supposed to have been
at that time a new and valuable multiple-sparking arrangement whereby
only one battery, one coil and one contact maker were utilized for causing
the spark in all five cylinders, a small commutating arrangement in the
high-tension circuit distributing the sparks to the proper cylinders at the
proper time. This form of sparking arrangement was found upon test to
work so satisfactorily that it was afterwards adopted for the small engine of
the quarter-size model, and also for the new and larger engine which was
afterwards built and which will be described further on. It is needless to
describe in detail the many and perplexing difficulties which were
experienced in procuring suitable spark coils, spark plugs and other
appurtenances of the sparking apparatus, all of which at this time were in a
very crude state of development, there being only a few different makes on
the market, and most of these being very unsatisfactory. One important
minor improvement connected with the spark plugs may be described, as
the beneficial effect produced by it was so very great that its use was
continued in all future spark plugs for all of the engines. This improvement,
adjusting it.
At the time that this engine was being developed it was practically
impossible to obtain any outside information regarding the proper way of
constructing it. The little that was then known had been learned through
laborious experience and at great cost by the experimenters who were
attempting to build automobiles, and was zealously guarded in the hope of
preventing their rivals from utilizing the results of their labors. It was the
known custom, however, of all engine builders at this time to use a separate
spark coil and a separate contact maker for each cylinder of an engine, no
matter how many cylinders there were. This multiplication of the spark
coils, which at that time were very heavy, not only added greatly to the
weight but also had the same defect that the wipe-spark type of sparking
arrangement had of being exceedingly difficult to so adjust that all of the
contact makers would perform their functions at exactly the same point in
the cycle for each cylinder. To obviate these difficulties, both of adjustment
and of excessive weight, the writer devised what is supposed to have been
at that time a new and valuable multiple-sparking arrangement whereby
only one battery, one coil and one contact maker were utilized for causing
the spark in all five cylinders, a small commutating arrangement in the
high-tension circuit distributing the sparks to the proper cylinders at the
proper time. This form of sparking arrangement was found upon test to
work so satisfactorily that it was afterwards adopted for the small engine of
the quarter-size model, and also for the new and larger engine which was
afterwards built and which will be described further on. It is needless to
describe in detail the many and perplexing difficulties which were
experienced in procuring suitable spark coils, spark plugs and other
appurtenances of the sparking apparatus, all of which at this time were in a
very crude state of development, there being only a few different makes on
the market, and most of these being very unsatisfactory. One important
minor improvement connected with the spark plugs may be described, as
the beneficial effect produced by it was so very great that its use was
continued in all future spark plugs for all of the engines. This improvement,
Page 395
however, is now incorporated in many of the plugs which are on the market,
and in some cases patents, covering the particular form in which the
improvement is incorporated, are exploited by the manufacturer.
Considerable difficulty was at first experienced with the spark plugs from a
coating of soot (resulting from the incomplete combustion of the gas and oil
in the cylinder at the time of explosion) which formed on the porcelain and
thereby caused a short-circuit, preventing the plug from working properly.
This was overcome by extending the metal portion of the plug for some
distance into the cylinder, and for something like three-quarters of an [p222]
inch beyond the end of the porcelain insulator. The terminal which passed
through the insulator was also extended for something like half an inch
beyond the porcelain and bent to a proper extent to co-act with a piece of
platinum wire inserted in the interior wall of the plug which formed the
other terminal. After making this improvement in the plugs practically no
difficulty was experienced from short-circuits caused by the soot.
In making the tests of this experimental engine it was found practically
impossible to absorb the power by a Prony brake in a sufficiently uniform
manner on account of the fact that the engine was being run without a fly
wheel. The consequent variation in the torque and speed during each
revolution caused such great fluctuations in the reading of the scales which
measured the pull of the Prony brake that no confidence could be felt in the
accuracy of the readings and, therefore, no confidence could be placed in
the determinations of the effect which different changes in the engine
produced. A water-absorption dynamometer consisting of a number of flat,
circular discs fastened to a shaft and rotating between other parallel flat
discs arranged in a circular drum which was filled to any desired extent
with water was immediately planned, and the construction of two of them
was begun so that power could be taken from both ends of the engine shaft,
which, on account of its necessary lightness, was apt to be injured by being
twisted when all the power was taken from one end of the shaft. In order to
continue the tests on the engine while this dynamometer was being made it
was decided to employ one of the propellers as a dynamometer. Although
no accurate tests had been made to determine just how much power was
and in some cases patents, covering the particular form in which the
improvement is incorporated, are exploited by the manufacturer.
Considerable difficulty was at first experienced with the spark plugs from a
coating of soot (resulting from the incomplete combustion of the gas and oil
in the cylinder at the time of explosion) which formed on the porcelain and
thereby caused a short-circuit, preventing the plug from working properly.
This was overcome by extending the metal portion of the plug for some
distance into the cylinder, and for something like three-quarters of an [p222]
inch beyond the end of the porcelain insulator. The terminal which passed
through the insulator was also extended for something like half an inch
beyond the porcelain and bent to a proper extent to co-act with a piece of
platinum wire inserted in the interior wall of the plug which formed the
other terminal. After making this improvement in the plugs practically no
difficulty was experienced from short-circuits caused by the soot.
In making the tests of this experimental engine it was found practically
impossible to absorb the power by a Prony brake in a sufficiently uniform
manner on account of the fact that the engine was being run without a fly
wheel. The consequent variation in the torque and speed during each
revolution caused such great fluctuations in the reading of the scales which
measured the pull of the Prony brake that no confidence could be felt in the
accuracy of the readings and, therefore, no confidence could be placed in
the determinations of the effect which different changes in the engine
produced. A water-absorption dynamometer consisting of a number of flat,
circular discs fastened to a shaft and rotating between other parallel flat
discs arranged in a circular drum which was filled to any desired extent
with water was immediately planned, and the construction of two of them
was begun so that power could be taken from both ends of the engine shaft,
which, on account of its necessary lightness, was apt to be injured by being
twisted when all the power was taken from one end of the shaft. In order to
continue the tests on the engine while this dynamometer was being made it
was decided to employ one of the propellers as a dynamometer. Although
no accurate tests had been made to determine just how much power was
Page 396
required to drive these propellers at various speeds, yet the fundamental law
was known that under the same conditions the power required to drive any
propeller would vary as the cube of the number of revolutions, and since the
Prony-brake tests had given an approximation as to the amount of power
which the engine developed at certain speeds, the law of the propeller, and
extrapolations from the data obtained in the tests of the smaller propellers in
1898, enabled further approximations to be made as to the amount of extra
power which the engine developed when certain changes enabled it to drive
the propeller at increased speeds. This method had also the great advantage
that, since the power required varies as the cube of the number of
revolutions, it is practically impossible for the engine to “run away” with
the propeller and cause serious damage through the possible excessive
strains introduced by high speed. This feature is also possessed by water-
absorption dynamometers of the type which were built and used in the later
tests.
The construction of water jackets for this engine proved an exceedingly
formidable task, it being impossible to braze the jackets directly to the walls
of the cylinders without risk of ruining them. It therefore became necessary
to attach them by means of stuffing boxes, which, on account of their large
size [p223] and the necessity for keeping the weight a minimum, was a most
difficult piece of work. The work was rendered still more difficult by the
fact that the water jackets had to be made in halves which were brazed
together after they had been fitted over the head of the cylinder. Even when
the work was done in the most careful way this method of construction gave
a great deal of trouble from the leaking of the stuffing boxes or the jackets
themselves. However, after much delay, the water jackets were finally
completed, and upon test the engine was found to develop 21.5 horse-power
at 825 R. P. M., the engine itself weighing 120 pounds.
Further changes were made in this engine, especially in the pistons, a
new set of which were constructed which weighed 15 pounds less than the
original set. On account of the difficulty with the leakage of the water
around the stuffing boxes of the water jackets, and also from imperfections
in the brazed joints of the jackets themselves, it was found impossible to
was known that under the same conditions the power required to drive any
propeller would vary as the cube of the number of revolutions, and since the
Prony-brake tests had given an approximation as to the amount of power
which the engine developed at certain speeds, the law of the propeller, and
extrapolations from the data obtained in the tests of the smaller propellers in
1898, enabled further approximations to be made as to the amount of extra
power which the engine developed when certain changes enabled it to drive
the propeller at increased speeds. This method had also the great advantage
that, since the power required varies as the cube of the number of
revolutions, it is practically impossible for the engine to “run away” with
the propeller and cause serious damage through the possible excessive
strains introduced by high speed. This feature is also possessed by water-
absorption dynamometers of the type which were built and used in the later
tests.
The construction of water jackets for this engine proved an exceedingly
formidable task, it being impossible to braze the jackets directly to the walls
of the cylinders without risk of ruining them. It therefore became necessary
to attach them by means of stuffing boxes, which, on account of their large
size [p223] and the necessity for keeping the weight a minimum, was a most
difficult piece of work. The work was rendered still more difficult by the
fact that the water jackets had to be made in halves which were brazed
together after they had been fitted over the head of the cylinder. Even when
the work was done in the most careful way this method of construction gave
a great deal of trouble from the leaking of the stuffing boxes or the jackets
themselves. However, after much delay, the water jackets were finally
completed, and upon test the engine was found to develop 21.5 horse-power
at 825 R. P. M., the engine itself weighing 120 pounds.
Further changes were made in this engine, especially in the pistons, a
new set of which were constructed which weighed 15 pounds less than the
original set. On account of the difficulty with the leakage of the water
around the stuffing boxes of the water jackets, and also from imperfections
in the brazed joints of the jackets themselves, it was found impossible to
Page 397
rely on the power that the engine would develop at any particular time, as
the water leaking from the jackets and running down on the spark plugs of
the lower cylinders caused these cylinders to work erratically, and this not
only materially reduced the power but also caused jerky impulses in the
absence of fly wheels.
It seemed so desirable to obtain as soon as possible a first test in actual
flight of the large machine that the writer offered to put this engine in the
aerodrome frame and make a test with it if the machine were launched over
the water, but with the launching track mounted directly on the river bank.
However, Mr. Langley felt it so necessary to make the initial test from the
top of the house-boat and at an elevation of 30 feet or more that he would
not consent to this, and as the engine at its best did not develop quite 24
horse-power, which had been calculated as the minimum which should be
provided, it was thought unwise to attempt to make the first test from the
top of the house-boat until the aerodrome had been provided with engines
that could be depended on to develop continuously not less than 24 horse-
power.
It then became necessary either to build a duplicate engine and use both
of them in the aerodrome, the original plan as already explained having
been to have two engines developing the 24 horse-power together; or,
second, to construct an entirely new engine large enough to furnish a
minimum of 24 horse-power and use this single engine.
As the construction and tests of this experimental engine had shown
many places in which the weight might be safely reduced, the writer
decided to construct an entirely new and larger single engine, and thereby
avoid the extra weight and difficulties which would be introduced by
having to use synchronizing gears where two engines were used, it being
impossible, of course, to run the two propellers from the two engines
independently without risk of serious disaster. [p224]
It will be recalled that when the aerodrome was originally planned in
1898 it was proposed to have two engines of 12 horse-power each, and the
contract for the single engine of 12 horse-power provided that a duplicate
was to be supplied, if desired, immediately upon the completion and
the water leaking from the jackets and running down on the spark plugs of
the lower cylinders caused these cylinders to work erratically, and this not
only materially reduced the power but also caused jerky impulses in the
absence of fly wheels.
It seemed so desirable to obtain as soon as possible a first test in actual
flight of the large machine that the writer offered to put this engine in the
aerodrome frame and make a test with it if the machine were launched over
the water, but with the launching track mounted directly on the river bank.
However, Mr. Langley felt it so necessary to make the initial test from the
top of the house-boat and at an elevation of 30 feet or more that he would
not consent to this, and as the engine at its best did not develop quite 24
horse-power, which had been calculated as the minimum which should be
provided, it was thought unwise to attempt to make the first test from the
top of the house-boat until the aerodrome had been provided with engines
that could be depended on to develop continuously not less than 24 horse-
power.
It then became necessary either to build a duplicate engine and use both
of them in the aerodrome, the original plan as already explained having
been to have two engines developing the 24 horse-power together; or,
second, to construct an entirely new engine large enough to furnish a
minimum of 24 horse-power and use this single engine.
As the construction and tests of this experimental engine had shown
many places in which the weight might be safely reduced, the writer
decided to construct an entirely new and larger single engine, and thereby
avoid the extra weight and difficulties which would be introduced by
having to use synchronizing gears where two engines were used, it being
impossible, of course, to run the two propellers from the two engines
independently without risk of serious disaster. [p224]
It will be recalled that when the aerodrome was originally planned in
1898 it was proposed to have two engines of 12 horse-power each, and the
contract for the single engine of 12 horse-power provided that a duplicate
was to be supplied, if desired, immediately upon the completion and
Page 398
delivery of the first one. The calculations, both from the whirling-table tests
and from the results with the steam-driven models in actual flight, indicated
that 24 horse-power would be ample for the aerodrome, which it was then
expected would not exceed 640 pounds in weight, with a supporting surface
of 960 square feet. But it was found that the total weight of the machine
was rapidly increasing on account of slight increases in the various details,
which when added together made a considerable increase in weight.
Furthermore, as it had been found difficult to keep all five of the cylinders
of the experimental engine working uniformly, it was thought best to build
this new engine sufficiently large to provide not only the extra power
necessary because of the increased weight of the aerodrome, but also to
provide for further inevitable increases in weight, and over and above all
this, to provide also that the engine would furnish all the power necessary,
even though one of its cylinders should absolutely fail to work and act as a
dead load on the others. The writer accordingly designed this new engine to
give 40 horse-power when all five of the cylinders were working, and 28
horse-power even though one cylinder should act as a dead load on the
others.
The various materials for the construction of this engine were ordered
early in December, 1900, with the promise of delivery not later than
January, 1901. Owing to various causes, however, the major portion of the
materials could not be obtained until late in the spring, and, in fact, a
portion of them were not obtained until the summer of 1901. During this
period of delay, however, the engine for the quarter-size model was
completely reconstructed and further tests were made with the experimental
engine in developing accessories, such as carburetors and spark coils.
The float-feed type of carburetor which was then coming into
prominence in automobile work proved at that stage of its development to
be totally unsuitable, as the slight but constant tremor of the aerodrome
frame, when the engine was working at high speeds under a heavy load,
caused the float to act as a pump and periodically flood the carburetor. This
resulted in an irregularity of action of the engine which at times injured not
only the transmission shafts, gears, and frame, but the engine itself by the
and from the results with the steam-driven models in actual flight, indicated
that 24 horse-power would be ample for the aerodrome, which it was then
expected would not exceed 640 pounds in weight, with a supporting surface
of 960 square feet. But it was found that the total weight of the machine
was rapidly increasing on account of slight increases in the various details,
which when added together made a considerable increase in weight.
Furthermore, as it had been found difficult to keep all five of the cylinders
of the experimental engine working uniformly, it was thought best to build
this new engine sufficiently large to provide not only the extra power
necessary because of the increased weight of the aerodrome, but also to
provide for further inevitable increases in weight, and over and above all
this, to provide also that the engine would furnish all the power necessary,
even though one of its cylinders should absolutely fail to work and act as a
dead load on the others. The writer accordingly designed this new engine to
give 40 horse-power when all five of the cylinders were working, and 28
horse-power even though one cylinder should act as a dead load on the
others.
The various materials for the construction of this engine were ordered
early in December, 1900, with the promise of delivery not later than
January, 1901. Owing to various causes, however, the major portion of the
materials could not be obtained until late in the spring, and, in fact, a
portion of them were not obtained until the summer of 1901. During this
period of delay, however, the engine for the quarter-size model was
completely reconstructed and further tests were made with the experimental
engine in developing accessories, such as carburetors and spark coils.
The float-feed type of carburetor which was then coming into
prominence in automobile work proved at that stage of its development to
be totally unsuitable, as the slight but constant tremor of the aerodrome
frame, when the engine was working at high speeds under a heavy load,
caused the float to act as a pump and periodically flood the carburetor. This
resulted in an irregularity of action of the engine which at times injured not
only the transmission shafts, gears, and frame, but the engine itself by the
Page 399
serious pounding which occurred. A form was next tried in which the
gasoline was fed in through the valve seat of a lightly loaded valve which
raised whenever there was suction in the inlet pipe, the amount of gasoline
fed being regulated by a pin valve. Later there were built several shapes and
sizes of tanks filled with absorbent material, which was saturated with
gasoline and the surplus drawn off before starting the engine. Some of these
tanks were provided with a jacket through which [p225] a portion of the
exhaust gases was passed in order to compensate for the cooling of the tank
caused by the evaporation of the gasoline. As a result of these tests it was
found that a type consisting essentially of a tank filled with small lumps of
a porous cellular wood (tupelo wood) which was initially saturated with
gasoline, and into which the gasoline was fed through a distributing pipe as
rapidly as it was taken up by the air, which was sucked through it by the
engine, gave the best results. Instead of jacketing this tank, the cooling
effect due to evaporation was compensated by drawing the somewhat
heated air from around the engine cylinders up through the loosely packed
lumps of wood. When tested in the shop this type was found to give such a
very uniform mixture that the engine ran as smoothly and regularly as an
electric motor, the vibration in no way interfering with it, and even when
the sudden change from a state of rest to one of rapid motion through the air
was imitated by suddenly turning on the carburetor the blast of several large
electric fans from various angles, it was found to have no appreciable effect
on the running of the engine, thus indicating that the trouble which was
experienced with the model aerodrome in the trials of 1901 was not likely
to be repeated with the large aerodrome. Somewhat more than a dozen
carburetors of various forms were constructed before this last type was
devised, but this proved so satisfactory that there were never thereafter any
carburetor troubles. In fact, as will later appear, a carburetor of this type
kept the engine on the large aerodrome running at full power not only when
the aerodrome was in a vertical position in the air, but also after it had
turned completely over on its back.
gasoline was fed in through the valve seat of a lightly loaded valve which
raised whenever there was suction in the inlet pipe, the amount of gasoline
fed being regulated by a pin valve. Later there were built several shapes and
sizes of tanks filled with absorbent material, which was saturated with
gasoline and the surplus drawn off before starting the engine. Some of these
tanks were provided with a jacket through which [p225] a portion of the
exhaust gases was passed in order to compensate for the cooling of the tank
caused by the evaporation of the gasoline. As a result of these tests it was
found that a type consisting essentially of a tank filled with small lumps of
a porous cellular wood (tupelo wood) which was initially saturated with
gasoline, and into which the gasoline was fed through a distributing pipe as
rapidly as it was taken up by the air, which was sucked through it by the
engine, gave the best results. Instead of jacketing this tank, the cooling
effect due to evaporation was compensated by drawing the somewhat
heated air from around the engine cylinders up through the loosely packed
lumps of wood. When tested in the shop this type was found to give such a
very uniform mixture that the engine ran as smoothly and regularly as an
electric motor, the vibration in no way interfering with it, and even when
the sudden change from a state of rest to one of rapid motion through the air
was imitated by suddenly turning on the carburetor the blast of several large
electric fans from various angles, it was found to have no appreciable effect
on the running of the engine, thus indicating that the trouble which was
experienced with the model aerodrome in the trials of 1901 was not likely
to be repeated with the large aerodrome. Somewhat more than a dozen
carburetors of various forms were constructed before this last type was
devised, but this proved so satisfactory that there were never thereafter any
carburetor troubles. In fact, as will later appear, a carburetor of this type
kept the engine on the large aerodrome running at full power not only when
the aerodrome was in a vertical position in the air, but also after it had
turned completely over on its back.
Page 400
[p226] ◊
CHAPTER IX
THE QUARTER-SIZE MODEL AERODROME
Owing to the very considerable changes which constructional reasons
necessitated in the relative positions of the center of pressure, center of
gravity, and line of thrust from those which theoretical considerations
pointed to as being best, it was decided in January, 1900, to build a one-
quarter-size model of the large aerodrome, if a suitable engine capable of
furnishing something like one and a half horse-power could be procured
without delay. It was hoped that it might be possible to construct this model
immediately without seriously interfering with the progress of the work on
the large machine, and that some tests in free flight could then be made with
it, which would give very much more reliable data from which to determine
the balancing of the large aerodrome than had been obtained from the tests
of the steam-driven models Nos. 5 and 6. A factor of uncertainty would still
remain, due to the difference in size between the large machine and the
model, which could be determined only by actual trial of the large machine
itself; but by making the model an exact duplicate, on a smaller scale of the
large machine, very valuable results could be obtained. Tests of it in free
flight would involve, even with the probable attendant breakages, a
comparatively small expenditure of time and money. A search was
immediately begun for an engine builder who would undertake to furnish a
suitable engine for this model. The specifications called for an engine
developing one and a half horse-power on the Prony brake for five minutes
without diminution in power caused by over heating. While it was desired if
possible to get an engine which would come within the given weight and
develop the required power for a longer time than five minutes, it was
foreseen that the construction of a multiple-cylinder engine of so small a
power made it necessary to resort to the air-cooled type, and that such an
engine would be doing exceedingly well to develop its maximum power
continuously for as much as five minutes. The only engine builder who
CHAPTER IX
THE QUARTER-SIZE MODEL AERODROME
Owing to the very considerable changes which constructional reasons
necessitated in the relative positions of the center of pressure, center of
gravity, and line of thrust from those which theoretical considerations
pointed to as being best, it was decided in January, 1900, to build a one-
quarter-size model of the large aerodrome, if a suitable engine capable of
furnishing something like one and a half horse-power could be procured
without delay. It was hoped that it might be possible to construct this model
immediately without seriously interfering with the progress of the work on
the large machine, and that some tests in free flight could then be made with
it, which would give very much more reliable data from which to determine
the balancing of the large aerodrome than had been obtained from the tests
of the steam-driven models Nos. 5 and 6. A factor of uncertainty would still
remain, due to the difference in size between the large machine and the
model, which could be determined only by actual trial of the large machine
itself; but by making the model an exact duplicate, on a smaller scale of the
large machine, very valuable results could be obtained. Tests of it in free
flight would involve, even with the probable attendant breakages, a
comparatively small expenditure of time and money. A search was
immediately begun for an engine builder who would undertake to furnish a
suitable engine for this model. The specifications called for an engine
developing one and a half horse-power on the Prony brake for five minutes
without diminution in power caused by over heating. While it was desired if
possible to get an engine which would come within the given weight and
develop the required power for a longer time than five minutes, it was
foreseen that the construction of a multiple-cylinder engine of so small a
power made it necessary to resort to the air-cooled type, and that such an
engine would be doing exceedingly well to develop its maximum power
continuously for as much as five minutes. The only engine builder who
Page 401
could be found willing to undertake the construction of such an engine was
the one already engaged in the construction of the larger engine. As this
builder was already twelve months behind in the delivery of the large
engine, it was felt that it would be unwise to give it to him, both because the
work on it might still further delay him in the completion of the large one,
and also because he was still having troubles with the large one, which it
was not certain he would ever be able to overcome. After further
consideration of the matter, however, it seemed so important to have a
model which was an exact duplicate of the large machine for the [p227]
making of tests, which might prevent not only serious damage but possibly
fatal accidents, that upon the assurance of the engine builder that the
undertaking of the small engine would in no way interfere with the
completion of the large one, a contract was entered into on February 23,
1900, which specified that the engine should be delivered by April 1, with a
penalty for any delay beyond that date.
The frame for this quarter-size model was immediately begun and extra
workmen were employed for work on it in order that its construction should
in no way delay the completion of the large machine. The decision to
construct this quarter-size model of the large aerodrome had been made on
the assumption that, since it was to be one-sixteenth the weight of the large
machine, and therefore much heavier in comparison to its size than the
steam models Nos. 5 and 6, it would, therefore, not need to be so carefully
constructed in order to obtain sufficient strength. But when construction
was actually begun it was found not only that the simpler and less
expensive methods which it had been proposed to use in joining its frame
together resulted in a weak construction, but also that the time consumed in
tinkering up the imperfections in the joints more than counterbalanced the
extra time which would have been required to make the joints in the best
manner from the beginning. Before going very far it was therefore decided
to make the joints by following the same process which had been developed
in the construction of the previous models. The frame was accordingly built
in the most substantial manner, and when guyed by a system of guy-wires
similar to that employed for the large machine it was found to be
the one already engaged in the construction of the larger engine. As this
builder was already twelve months behind in the delivery of the large
engine, it was felt that it would be unwise to give it to him, both because the
work on it might still further delay him in the completion of the large one,
and also because he was still having troubles with the large one, which it
was not certain he would ever be able to overcome. After further
consideration of the matter, however, it seemed so important to have a
model which was an exact duplicate of the large machine for the [p227]
making of tests, which might prevent not only serious damage but possibly
fatal accidents, that upon the assurance of the engine builder that the
undertaking of the small engine would in no way interfere with the
completion of the large one, a contract was entered into on February 23,
1900, which specified that the engine should be delivered by April 1, with a
penalty for any delay beyond that date.
The frame for this quarter-size model was immediately begun and extra
workmen were employed for work on it in order that its construction should
in no way delay the completion of the large machine. The decision to
construct this quarter-size model of the large aerodrome had been made on
the assumption that, since it was to be one-sixteenth the weight of the large
machine, and therefore much heavier in comparison to its size than the
steam models Nos. 5 and 6, it would, therefore, not need to be so carefully
constructed in order to obtain sufficient strength. But when construction
was actually begun it was found not only that the simpler and less
expensive methods which it had been proposed to use in joining its frame
together resulted in a weak construction, but also that the time consumed in
tinkering up the imperfections in the joints more than counterbalanced the
extra time which would have been required to make the joints in the best
manner from the beginning. Before going very far it was therefore decided
to make the joints by following the same process which had been developed
in the construction of the previous models. The frame was accordingly built
in the most substantial manner, and when guyed by a system of guy-wires
similar to that employed for the large machine it was found to be
Page 402
exceedingly stiff, in fact very much stronger and stiffer than the frame of
any of the preceding models.
In originally planning the model the intention was to make all its linear
dimensions exactly one-fourth those of the large aerodrome. Before the
designs were completed, however, it was seen from the previous experience
with the steam-driven models that instead of the 62.5-cm. propellers, which
a strict adherence to the quarter-size plan would demand, it would be
necessary to use propellers which were at least one metre in diameter.
Moreover, as the small engine would be more than one-fourth the size of
the engine under construction for the large aerodrome, a departure from the
scale in the case of the transverse frame would be necessary. The designs
were therefore altered so as to admit of using the larger propellers, and the
tubes which formed the front of the transverse frame were bent, as shown in
the plan photograph, Plate 70, in order to give a large enough space for
properly mounting the engine.
The frame with these modifications was completed in June, 1900, but no
engine was ready for it, as the builder had failed to fulfill his contract for
either the large or the small engine, although several trips to New York had
been made to expedite their successful completion. [p228]
Soon after this it became certain that the engines for both aerodromes
would have to be constructed in the shops of the Institution, and owing to
the greater importance of the experimental engine for the large aerodrome,
all the facilities of the shops were devoted to the early completion of it. In
November, 1900, however, it was seen that the experimental engine alone
would not furnish sufficient power for the large aerodrome, and that a
duplicate of it would have to be built or a new and larger engine designed
and constructed, and that therefore it would be impossible to get the first
tests of the large aerodrome in free flight before the following summer. It
was therefore decided that it would be best to suspend work temporarily on
the large aerodrome and its engine, and put all the workmen who could
possibly be employed on the construction of the small engine, so that it
would be ready in time to permit some tests of the quarter-size model to be
made during the following spring.
any of the preceding models.
In originally planning the model the intention was to make all its linear
dimensions exactly one-fourth those of the large aerodrome. Before the
designs were completed, however, it was seen from the previous experience
with the steam-driven models that instead of the 62.5-cm. propellers, which
a strict adherence to the quarter-size plan would demand, it would be
necessary to use propellers which were at least one metre in diameter.
Moreover, as the small engine would be more than one-fourth the size of
the engine under construction for the large aerodrome, a departure from the
scale in the case of the transverse frame would be necessary. The designs
were therefore altered so as to admit of using the larger propellers, and the
tubes which formed the front of the transverse frame were bent, as shown in
the plan photograph, Plate 70, in order to give a large enough space for
properly mounting the engine.
The frame with these modifications was completed in June, 1900, but no
engine was ready for it, as the builder had failed to fulfill his contract for
either the large or the small engine, although several trips to New York had
been made to expedite their successful completion. [p228]
Soon after this it became certain that the engines for both aerodromes
would have to be constructed in the shops of the Institution, and owing to
the greater importance of the experimental engine for the large aerodrome,
all the facilities of the shops were devoted to the early completion of it. In
November, 1900, however, it was seen that the experimental engine alone
would not furnish sufficient power for the large aerodrome, and that a
duplicate of it would have to be built or a new and larger engine designed
and constructed, and that therefore it would be impossible to get the first
tests of the large aerodrome in free flight before the following summer. It
was therefore decided that it would be best to suspend work temporarily on
the large aerodrome and its engine, and put all the workmen who could
possibly be employed on the construction of the small engine, so that it
would be ready in time to permit some tests of the quarter-size model to be
made during the following spring.
Page 403
In order to expedite its construction as much as possible, the attempt was
made to utilize all the available parts from the small engine which had been
undertaken by the engine builder in New York. The cylinders, which it had
been expected would be kept cool by their rotation around the crank pin,
were not well adapted for use as stationary cylinders, since they were not
provided with radiating ribs, but it was hoped that by using them an engine
could be very quickly constructed which would keep cool long enough to
enable some short flights to be made with the model.
The work on this small engine was pushed forward very rapidly, so that
within a short time it was sufficiently complete to allow some power tests to
be made with it. In the first of these tests the attempt was made to measure
the power by means of the Prony brake, but as the engine had no fly wheel
the fluctuations in speed during each revolution were so great as to make it
impossible to obtain readings of any value. When it was attempted to
remedy this by putting a fly wheel on either side of the crank shaft of the
engine, it was found that the sudden starting of the engine caused such
severe strains in the crank shaft, which had been built strong enough for
driving the propellers but not for suddenly starting fly wheels having
considerable inertia, as to make it unsafe to continue the use of fly wheels.
As without them the Prony brake could not be used, it was decided to build
a small water-absorption dynamometer on the same principle as the larger
ones which were under construction for the large engine. As this larger
dynamometer has already been described, it is only necessary to add that
the small one consisted of twelve rotating plates and twelve stator plates
twelve inches in diameter. In order to avoid the construction of a special
and elaborate testing frame for mounting the engine and the dynamometer
exactly in line with each other, it was attempted to connect them by means
of a universal joint. This “short cut” also proved the “long way around.”
The strains set up in the universal joint by the sudden starting of [p229] the
engine caused so much trouble on account of the inertia of the rotating
plates of the dynamometer that the time lost in keeping the universal joint in
working order during the tests more than counterbalanced the extra time
which would have been required to construct a special wooden frame on
made to utilize all the available parts from the small engine which had been
undertaken by the engine builder in New York. The cylinders, which it had
been expected would be kept cool by their rotation around the crank pin,
were not well adapted for use as stationary cylinders, since they were not
provided with radiating ribs, but it was hoped that by using them an engine
could be very quickly constructed which would keep cool long enough to
enable some short flights to be made with the model.
The work on this small engine was pushed forward very rapidly, so that
within a short time it was sufficiently complete to allow some power tests to
be made with it. In the first of these tests the attempt was made to measure
the power by means of the Prony brake, but as the engine had no fly wheel
the fluctuations in speed during each revolution were so great as to make it
impossible to obtain readings of any value. When it was attempted to
remedy this by putting a fly wheel on either side of the crank shaft of the
engine, it was found that the sudden starting of the engine caused such
severe strains in the crank shaft, which had been built strong enough for
driving the propellers but not for suddenly starting fly wheels having
considerable inertia, as to make it unsafe to continue the use of fly wheels.
As without them the Prony brake could not be used, it was decided to build
a small water-absorption dynamometer on the same principle as the larger
ones which were under construction for the large engine. As this larger
dynamometer has already been described, it is only necessary to add that
the small one consisted of twelve rotating plates and twelve stator plates
twelve inches in diameter. In order to avoid the construction of a special
and elaborate testing frame for mounting the engine and the dynamometer
exactly in line with each other, it was attempted to connect them by means
of a universal joint. This “short cut” also proved the “long way around.”
The strains set up in the universal joint by the sudden starting of [p229] the
engine caused so much trouble on account of the inertia of the rotating
plates of the dynamometer that the time lost in keeping the universal joint in
working order during the tests more than counterbalanced the extra time
which would have been required to construct a special wooden frame on
Page 404
which the dynamometer and engine could have been mounted in line with
each other so that the crank shaft of the engine could have been directly
connected to the shaft of the dynamometer.
Much time was also lost in the effort to construct an apparatus by which a
record could be obtained of the power actually used in propelling the
aerodrome. Various methods were in use by which the thrust of the
propellers could be more or less satisfactorily measured while the
aerodrome was at rest, but it was desired to know just how much power the
aerodrome consumed while in actual free flight. Such a record it was hoped
to obtain from a device incorporated in the propeller shafts. This thrust-
measuring device consisted essentially of a propeller shaft made in two
sections, one section telescoping the other for a short distance. On the
section of the shaft to which the propeller was attached there was mounted a
drum, having in its circumference two long slots diametrically opposite. To
the other section of the shaft a disc was fastened with two diametrically
opposite rollers mounted on its periphery, which fitted the slots in the drum
of the other section. A compression spring was interposed between the disc
and the drum, and the outside of the drum was so arranged that a strip of
paper could be wound around and fastened to it which would serve as a
chronograph sheet. A pencil was fastened to the frame, and, since the drum
was connected to the section of the shaft to which the propeller was
attached and which therefore moved to and from the frame under the action
of the propeller thrust, a record of the actual thrust of the propeller at any
particular moment could be obtained by simply pressing the pencil up
against the paper on the drum and calculating the thrust from the calibration
of the compression spring. Since the thrust would naturally be greater when
the propellers were revolving in a moored condition, during the few
moments after the engine was started up and before the aerodrome was
launched, it was necessary to provide means for having the pencil point
held away from the chronograph sheet until the aerodrome was launched,
and then have the point come to bear on the sheet. This was accomplished
by having the point held off by a small trigger arrangement which was to be
released just at the moment that the aerodrome left the launching car. A set
each other so that the crank shaft of the engine could have been directly
connected to the shaft of the dynamometer.
Much time was also lost in the effort to construct an apparatus by which a
record could be obtained of the power actually used in propelling the
aerodrome. Various methods were in use by which the thrust of the
propellers could be more or less satisfactorily measured while the
aerodrome was at rest, but it was desired to know just how much power the
aerodrome consumed while in actual free flight. Such a record it was hoped
to obtain from a device incorporated in the propeller shafts. This thrust-
measuring device consisted essentially of a propeller shaft made in two
sections, one section telescoping the other for a short distance. On the
section of the shaft to which the propeller was attached there was mounted a
drum, having in its circumference two long slots diametrically opposite. To
the other section of the shaft a disc was fastened with two diametrically
opposite rollers mounted on its periphery, which fitted the slots in the drum
of the other section. A compression spring was interposed between the disc
and the drum, and the outside of the drum was so arranged that a strip of
paper could be wound around and fastened to it which would serve as a
chronograph sheet. A pencil was fastened to the frame, and, since the drum
was connected to the section of the shaft to which the propeller was
attached and which therefore moved to and from the frame under the action
of the propeller thrust, a record of the actual thrust of the propeller at any
particular moment could be obtained by simply pressing the pencil up
against the paper on the drum and calculating the thrust from the calibration
of the compression spring. Since the thrust would naturally be greater when
the propellers were revolving in a moored condition, during the few
moments after the engine was started up and before the aerodrome was
launched, it was necessary to provide means for having the pencil point
held away from the chronograph sheet until the aerodrome was launched,
and then have the point come to bear on the sheet. This was accomplished
by having the point held off by a small trigger arrangement which was to be
released just at the moment that the aerodrome left the launching car. A set
Page 405
of propeller shafts embodying this thrust-recording device was constructed,
but when they were actually tested on the aerodrome many difficulties were
encountered which had not been anticipated. In the first place the gasoline
engine for the model was started up (or “cranked over”) by turning the
propellers by hand. A gasoline engine never starts slowly, and on account of
this suddenness of starting causes a very great strain in any [p230] shafting
by which it is connected to any driven mechanism. The inertia of the driven
mechanism, even though it be apparently small, becomes a most serious
matter when an attempt is made to start up very suddenly. This effect is very
much intensified if the driven mechanism is connected to the engine
through even one pair of gears, for there is always a certain amount of back-
lash between the teeth of the gears, and the effect of this back-lash is still
further intensified when the driven mechanism is turned over by hand in
order to start the engine, as this takes up the back-lash on one side of the
gears, and the moment the engine starts permits a free movement until it
suddenly takes up the back-lash and strikes the other side of the gear teeth
with a blow. The effect of this sudden starting of the engine proved most
disastrous to the thrust-recording devices, and, although they were
considerably strengthened, it was found after a short time that in order to
make them strong enough to withstand the shock of the sudden starting of
the engine it would be necessary to make them inordinately heavy. It was
therefore decided to abandon all attempts to incorporate the thrust-recording
device on this quarter-size model, but it was hoped to install it later on one
of the steam-driven models, where the engine starts so slowly that there
would be no need for excessive strength in it.
The engine for the quarter model when reconstructed with stationary
instead of rotating cylinders was found in the shop tests referred to above to
develop when working at its best between 1 12 and 2 horse-power, as
measured by the absorption dynamometers. However, it was impossible to
maintain this power steadily for more than 30 seconds. In the first place, the
same difficulties (heretofore described) that were met with in securing a
suitable carburetor for the experimental engine were experienced at the
but when they were actually tested on the aerodrome many difficulties were
encountered which had not been anticipated. In the first place the gasoline
engine for the model was started up (or “cranked over”) by turning the
propellers by hand. A gasoline engine never starts slowly, and on account of
this suddenness of starting causes a very great strain in any [p230] shafting
by which it is connected to any driven mechanism. The inertia of the driven
mechanism, even though it be apparently small, becomes a most serious
matter when an attempt is made to start up very suddenly. This effect is very
much intensified if the driven mechanism is connected to the engine
through even one pair of gears, for there is always a certain amount of back-
lash between the teeth of the gears, and the effect of this back-lash is still
further intensified when the driven mechanism is turned over by hand in
order to start the engine, as this takes up the back-lash on one side of the
gears, and the moment the engine starts permits a free movement until it
suddenly takes up the back-lash and strikes the other side of the gear teeth
with a blow. The effect of this sudden starting of the engine proved most
disastrous to the thrust-recording devices, and, although they were
considerably strengthened, it was found after a short time that in order to
make them strong enough to withstand the shock of the sudden starting of
the engine it would be necessary to make them inordinately heavy. It was
therefore decided to abandon all attempts to incorporate the thrust-recording
device on this quarter-size model, but it was hoped to install it later on one
of the steam-driven models, where the engine starts so slowly that there
would be no need for excessive strength in it.
The engine for the quarter model when reconstructed with stationary
instead of rotating cylinders was found in the shop tests referred to above to
develop when working at its best between 1 12 and 2 horse-power, as
measured by the absorption dynamometers. However, it was impossible to
maintain this power steadily for more than 30 seconds. In the first place, the
same difficulties (heretofore described) that were met with in securing a
suitable carburetor for the experimental engine were experienced at the
Page 406
same time in the development of the small engine. In the second place, as
the engine had no cooling apparatus of any kind, it was found that it could
not be tested in the shop for more than 30 seconds owing to premature
explosions. It was hoped, however, that by having everything ready for a
flight before starting the engine, it might be possible to launch the
aerodrome before the cylinders began to heat seriously, and that the greatly
increased cooling effect due to the motion of the aerodrome through the air
would permit the engine to develop sufficient power to secure a flight that
would show whether or not the balancing was correct, as the final
disposition of some of the accessories on the large aerodrome could not be
so well settled until it was known just how the calculated balancing of this
new model corresponded with the actual balancing necessary for flight.
On account of Mr. Langley’s reliance on the generally sound theory that
where a successful method of conducting an experiment has been found
only after a long series of failures it is best not to change to some unknown
and untried plan, it was impossible, especially where failure in the test
might involve a fatal accident, to get him to deviate from his original plan
of [p231] launching the large aerodrome from the top of the house-boat. He
apparently realized as well as anyone, that in many respects the making of
the test from the top of the house-boat had many serious drawbacks, but he
emphasized and impressed on the writer the importance of following as far
as possible in the construction and test of the large machine, the plans
which had brought success with the models. Believing, however, that there
was probably a better method of launching the aerodrome than from the top
of the house-boat, and that it would be well to prepare before hand as far as
possible for following some other plan of launching immediately after a
first successful test had been obtained from the top of the boat, Mr. Langley
had constructed some floats which were arranged to be attached to the
launching car of the quarter-size model so that the car could be converted
into a catamaran raft. It was not believed that this crude arrangement would
suffice for a complete launching apparatus, since the power of the
aerodrome propellers would not be great enough to force the raft through
the water at a sufficiently high speed; still it was thought that by having the
the engine had no cooling apparatus of any kind, it was found that it could
not be tested in the shop for more than 30 seconds owing to premature
explosions. It was hoped, however, that by having everything ready for a
flight before starting the engine, it might be possible to launch the
aerodrome before the cylinders began to heat seriously, and that the greatly
increased cooling effect due to the motion of the aerodrome through the air
would permit the engine to develop sufficient power to secure a flight that
would show whether or not the balancing was correct, as the final
disposition of some of the accessories on the large aerodrome could not be
so well settled until it was known just how the calculated balancing of this
new model corresponded with the actual balancing necessary for flight.
On account of Mr. Langley’s reliance on the generally sound theory that
where a successful method of conducting an experiment has been found
only after a long series of failures it is best not to change to some unknown
and untried plan, it was impossible, especially where failure in the test
might involve a fatal accident, to get him to deviate from his original plan
of [p231] launching the large aerodrome from the top of the house-boat. He
apparently realized as well as anyone, that in many respects the making of
the test from the top of the house-boat had many serious drawbacks, but he
emphasized and impressed on the writer the importance of following as far
as possible in the construction and test of the large machine, the plans
which had brought success with the models. Believing, however, that there
was probably a better method of launching the aerodrome than from the top
of the house-boat, and that it would be well to prepare before hand as far as
possible for following some other plan of launching immediately after a
first successful test had been obtained from the top of the boat, Mr. Langley
had constructed some floats which were arranged to be attached to the
launching car of the quarter-size model so that the car could be converted
into a catamaran raft. It was not believed that this crude arrangement would
suffice for a complete launching apparatus, since the power of the
aerodrome propellers would not be great enough to force the raft through
the water at a sufficiently high speed; still it was thought that by having the
Page 407
launching car arranged in this way the model might be allowed to drive the
raft rapidly through the water and thus give some idea as to what would be
necessary, in a more complete launching apparatus, to obviate the danger of
the drag of the raft causing the model to plunge over headlong into the
water. The launching car with these floats attached to it, and with the
quarter-size model mounted on the car, is clearly shown in Plates 73 and 74.
While the results obtained with superposed wings in the tests of models
Nos. 5 and 6 in the summer of 1899 indicated that the “single-tier” surfaces
were much more efficient, still, as has been already stated, the great
advantages of the superposed surfaces, so far as strength of construction is
concerned, was fully realized at all times. As a result of these tests it was
decided to use the “single-tier” surfaces in the first test of the large machine
in order to insure as far as possible the best conditions. However, it was
from the beginning planned to construct superposed surfaces for use in the
later tests of the large machine; and, in order to obtain more reliable data on
such surfaces than had been obtained in the tests of the models in the
summer of 1899, a set of superposed surfaces for the quarter-size model
were constructed during the winter of 1900–1901. The quarter-size model,
equipped with these surfaces, is shown in Plates 75 and 76, where the
model is seen mounted on its launching car, which is attached to the floats
heretofore referred to. It was originally planned not to employ guy-posts
when using the superposed surfaces, but after the latter had been
constructed and attached to the frame, it was found that they would have to
be made with rigid joints instead of hinged joints if the guy-posts were
omitted. As the hinged joints, however, were already made, and permitted
the surfaces to be folded up so as to occupy a much smaller [p232] space in
shipping them, it was decided to retain the hinged form of construction and
use the guy-posts as shown in the above plates.
raft rapidly through the water and thus give some idea as to what would be
necessary, in a more complete launching apparatus, to obviate the danger of
the drag of the raft causing the model to plunge over headlong into the
water. The launching car with these floats attached to it, and with the
quarter-size model mounted on the car, is clearly shown in Plates 73 and 74.
While the results obtained with superposed wings in the tests of models
Nos. 5 and 6 in the summer of 1899 indicated that the “single-tier” surfaces
were much more efficient, still, as has been already stated, the great
advantages of the superposed surfaces, so far as strength of construction is
concerned, was fully realized at all times. As a result of these tests it was
decided to use the “single-tier” surfaces in the first test of the large machine
in order to insure as far as possible the best conditions. However, it was
from the beginning planned to construct superposed surfaces for use in the
later tests of the large machine; and, in order to obtain more reliable data on
such surfaces than had been obtained in the tests of the models in the
summer of 1899, a set of superposed surfaces for the quarter-size model
were constructed during the winter of 1900–1901. The quarter-size model,
equipped with these surfaces, is shown in Plates 75 and 76, where the
model is seen mounted on its launching car, which is attached to the floats
heretofore referred to. It was originally planned not to employ guy-posts
when using the superposed surfaces, but after the latter had been
constructed and attached to the frame, it was found that they would have to
be made with rigid joints instead of hinged joints if the guy-posts were
omitted. As the hinged joints, however, were already made, and permitted
the surfaces to be folded up so as to occupy a much smaller [p232] space in
shipping them, it was decided to retain the hinged form of construction and
use the guy-posts as shown in the above plates.
Page 408
PL. 70. PLAN VIEW OF QUARTER-SIZE MODEL AERODROME, JUNE 1, 1900 ◊
Page 409
PL. 71. PLAN VIEW OF QUARTER-SIZE MODEL AERODROME ◊
Page 410
PL. 72. END, SIDE, AND THREE-QUARTER ELEVATION OF QUARTER-SIZE
MODEL AERODROME ◊
MODEL AERODROME ◊
Page 411
PL. 73. LAUNCHING-CAR WITH FLOATS ◊
Page 412
PL. 74. LAUNCHING-CAR WITH FLOATS ◊
Page 413
PL. 75. QUARTER-SIZE MODEL AERODROME EQUIPPED WITH SUPERPOSED
SURFACES, JUNE 11, 1901, SIDE VIEW ◊
SURFACES, JUNE 11, 1901, SIDE VIEW ◊
Page 414
PL. 76. QUARTER-SIZE MODEL AERODROME EQUIPPED
WITH SUPERPOSED SURFACES, JUNE 11, 1901. END VIEW
◊
WITH SUPERPOSED SURFACES, JUNE 11, 1901. END VIEW
◊
Page 415
PL. 77. CYLINDERS OF ENGINE OF
QUARTER-SIZE MODEL AERODROME ◊
After much delay, due to various causes, the quarter-size model, as
shown in plan, end elevation, side elevation and three-quarter elevation in
QUARTER-SIZE MODEL AERODROME ◊
After much delay, due to various causes, the quarter-size model, as
shown in plan, end elevation, side elevation and three-quarter elevation in
Page 416
Plates 71 and 72, respectively, was taken down the river in June, 1901, in
order to make some tests with it from the small house-boat, which had been
previously moved to the middle of the river opposite Widewater, Va. A test
of it in free flight was made on June 18, its condition at this time being
shown by Data Sheet No. 12 in Appendix. The launching apparatus worked
perfectly and the aerodrome started off on an absolutely even keel, dropping
only a few inches immediately upon leaving the launching apparatus, and
continuing straight ahead directly into the light wind of something less than
2 miles an hour. After it had gone only about 100 feet, however, it began to
descend slowly, but still maintained a perfectly even balance, and finally
touched the water about 150 feet from the house-boat, having been in the
air between 4 and 5 seconds. It was immediately recovered, and as soon as
the wings could be dried out another test was made, as it was thought
probable that the wind had interfered with the carburetor to such an extent
that the engine had not received the proper mixture of gas. Upon this
second test the launching apparatus again worked perfectly and the
aerodrome again flew straight ahead on a perfectly even keel, and at a
uniform height from the water until it had gone about 300 feet, when it
again began to descend slowly and finally touched the water about 350 feet
from the house-boat, having been in the air about 10 seconds. While the
tests were very disappointing, owing to the extreme brevity of the flights,
yet they showed conclusively that the balancing of the aerodrome was
correct, at least as far as motion in a straight line and in a quiet atmosphere
was concerned. As one and a half horse-power, which was felt to be the
very minimum which would successfully propel the aerodrome, was
furnished by the engine only when working at its very best, and as the
change in conditions from a quiet state to a velocity of something like 40
feet per second evidently caused a considerable drop in the power because
of the change in the gaseous mixture which the carburetor furnished to the
engine, it was decided not to make any further test of the aerodrome until
the engine cylinders could be reconstructed so as to provide more effective
means for cooling it, and thereby a reasonable margin of power above that
actually necessary. The aerodrome was accordingly returned to Washington
order to make some tests with it from the small house-boat, which had been
previously moved to the middle of the river opposite Widewater, Va. A test
of it in free flight was made on June 18, its condition at this time being
shown by Data Sheet No. 12 in Appendix. The launching apparatus worked
perfectly and the aerodrome started off on an absolutely even keel, dropping
only a few inches immediately upon leaving the launching apparatus, and
continuing straight ahead directly into the light wind of something less than
2 miles an hour. After it had gone only about 100 feet, however, it began to
descend slowly, but still maintained a perfectly even balance, and finally
touched the water about 150 feet from the house-boat, having been in the
air between 4 and 5 seconds. It was immediately recovered, and as soon as
the wings could be dried out another test was made, as it was thought
probable that the wind had interfered with the carburetor to such an extent
that the engine had not received the proper mixture of gas. Upon this
second test the launching apparatus again worked perfectly and the
aerodrome again flew straight ahead on a perfectly even keel, and at a
uniform height from the water until it had gone about 300 feet, when it
again began to descend slowly and finally touched the water about 350 feet
from the house-boat, having been in the air about 10 seconds. While the
tests were very disappointing, owing to the extreme brevity of the flights,
yet they showed conclusively that the balancing of the aerodrome was
correct, at least as far as motion in a straight line and in a quiet atmosphere
was concerned. As one and a half horse-power, which was felt to be the
very minimum which would successfully propel the aerodrome, was
furnished by the engine only when working at its very best, and as the
change in conditions from a quiet state to a velocity of something like 40
feet per second evidently caused a considerable drop in the power because
of the change in the gaseous mixture which the carburetor furnished to the
engine, it was decided not to make any further test of the aerodrome until
the engine cylinders could be reconstructed so as to provide more effective
means for cooling it, and thereby a reasonable margin of power above that
actually necessary. The aerodrome was accordingly returned to Washington
Page 417
for the purpose of making new cylinders for the engine. In constructing
these new cylinders the old cylinder heads from the previous cylinders were
used in order to expedite their completion. This proved in the end to be a
very great mistake, though at the time it seemed probable that the use of
them would save much delay and considerable expense. The new cylinders
were constructed of steel tubing originally one-half inch thick, which [p233]
was machined to the form clearly shown in the photograph, Plate 77, where
it will be seen that thin radiating ribs spaced one-quarter inch apart were
formed integral with the cylinder, the combustion chambers or heads being
screwed on and brazed to the cylinders. After much delay the new cylinders
were completed, and upon test it was found that while the radiating ribs
assisted very greatly in keeping the engine cool, yet the valves were so
small that the gas was not able to get in and out of the cylinders rapidly
enough to permit the engine to furnish its full power. Even at this stage it
would have been better either to have made new cylinder heads with larger
valves or to have made entirely new cylinders and cylinder heads, but in the
effort to economize time and money it seemed best to try to overcome part
of the defect by adding an auxiliary inlet valve. This was constructed, and
upon test it was found that, although the engine developed 3.2 horse-power
on the Prony brake at 1800 R. P. M., and even maintained 5.1 horse-power
on the brake for a few seconds when running at 3000 R. P. M., the ports
leading from the valve chamber to the cylinders were so small that they
became heated after the engine had run for 2 minutes and premature
ignition occurred, which, of course, immediately and very greatly reduced
the power developed.
It was decided, however, in view of the tests in which the engine had
developed 3.2 horse-power at 1800 R. P. M., that there was sufficient
margin of power to enable it to propel the quarter-size model, even if it was
not working at its best. After concluding the Prony-brake tests on the
engine, it was mounted in its proper position in the aerodrome frame and
connected to the propeller shafts. Some pendulum tests were then made,
showing an average lift of approximately 57 per cent of the total flying
weight. But it was found that the propeller and transmission shafts and their
these new cylinders the old cylinder heads from the previous cylinders were
used in order to expedite their completion. This proved in the end to be a
very great mistake, though at the time it seemed probable that the use of
them would save much delay and considerable expense. The new cylinders
were constructed of steel tubing originally one-half inch thick, which [p233]
was machined to the form clearly shown in the photograph, Plate 77, where
it will be seen that thin radiating ribs spaced one-quarter inch apart were
formed integral with the cylinder, the combustion chambers or heads being
screwed on and brazed to the cylinders. After much delay the new cylinders
were completed, and upon test it was found that while the radiating ribs
assisted very greatly in keeping the engine cool, yet the valves were so
small that the gas was not able to get in and out of the cylinders rapidly
enough to permit the engine to furnish its full power. Even at this stage it
would have been better either to have made new cylinder heads with larger
valves or to have made entirely new cylinders and cylinder heads, but in the
effort to economize time and money it seemed best to try to overcome part
of the defect by adding an auxiliary inlet valve. This was constructed, and
upon test it was found that, although the engine developed 3.2 horse-power
on the Prony brake at 1800 R. P. M., and even maintained 5.1 horse-power
on the brake for a few seconds when running at 3000 R. P. M., the ports
leading from the valve chamber to the cylinders were so small that they
became heated after the engine had run for 2 minutes and premature
ignition occurred, which, of course, immediately and very greatly reduced
the power developed.
It was decided, however, in view of the tests in which the engine had
developed 3.2 horse-power at 1800 R. P. M., that there was sufficient
margin of power to enable it to propel the quarter-size model, even if it was
not working at its best. After concluding the Prony-brake tests on the
engine, it was mounted in its proper position in the aerodrome frame and
connected to the propeller shafts. Some pendulum tests were then made,
showing an average lift of approximately 57 per cent of the total flying
weight. But it was found that the propeller and transmission shafts and their
Page 418
bearings would not stand the strain due to the increased power of the
engine. Newer and stronger shafts and bearings were, therefore, constructed
and further pendulum tests were made. It was then found that the transverse
frame which supported the shafts and bearings was too weak, and this was
strengthened by substituting newer and thicker tubing where it seemed
necessary.
These changes and repairs were all completed by October, 1901, and the
quarter-size model was at last, after months of delay, felt to be in a
condition which justified the expectation that its next flight would be
entirely successful. In view of the much more important work on the large
aerodrome which demanded immediate attention the quarter-size model in
this completed condition was put aside. Nothing more was done with it until
April, 1903, when some shop tests were made preliminary to taking it to
Quantico, where, on August 8, it made a successful flight, which is
described in Chapter XII ◊.
engine. Newer and stronger shafts and bearings were, therefore, constructed
and further pendulum tests were made. It was then found that the transverse
frame which supported the shafts and bearings was too weak, and this was
strengthened by substituting newer and thicker tubing where it seemed
necessary.
These changes and repairs were all completed by October, 1901, and the
quarter-size model was at last, after months of delay, felt to be in a
condition which justified the expectation that its next flight would be
entirely successful. In view of the much more important work on the large
aerodrome which demanded immediate attention the quarter-size model in
this completed condition was put aside. Nothing more was done with it until
April, 1903, when some shop tests were made preliminary to taking it to
Quantico, where, on August 8, it made a successful flight, which is
described in Chapter XII ◊.
Page 419
[p234] ◊
CHAPTER X
CONSTRUCTION AND TESTS OF THE LARGE ENGINE
The main requirement in an engine for an aerodrome—aside from
reliability and smoothness of operation, which are necessary in an engine
for any kind of locomotion—is that it shall develop the greatest amount of
power for the least weight. It is, therefore, desirable to reduce the weight
and number of parts of the engine to the very minimum, so far as this can be
done without sacrificing reliability and smoothness of running.
Furthermore, since the strongest metal for its weight is steel, and since the
greatest strength of steel is utilized when the stress acting on it is one of
tension, it is advisable to design the engine so that the parts which sustain
the greatest strains shall be of steel and, as far as possible, meet with strains
which are purely tensional ones.
In designing the new engine for the large aerodrome it was, therefore,
planned to make it entirely of steel, as far as this was possible. The only
parts which were not of steel were the bronze bushings for the bearings, the
cast-iron pistons, and cast-iron liners of the cylinders. Previous experience
had shown that, while it is possible to use a cast-iron piston in a steel
cylinder or even a steel piston in a steel cylinder, provided the lubrication
be kept exactly adjusted, yet the proper lubrication of the piston and
cylinder of a gas engine is difficult even under the most favorable
conditions, owing to the fact that excessive lubrication causes trouble from
the surplus oil interfering with the sparking apparatus. It was, therefore,
determined not to risk serious trouble by attempting to have the pistons bear
directly on the steel walls of the cylinders.
While visiting the French engine builders in the summer of 1900 in the
attempt to find one willing to undertake the construction of a suitable
engine for the aerodrome, it was pointed out to them that the great amount
of weight which they claimed to be necessary for the cylinders, and which
they stated made it impossible for them to build an engine which would
CHAPTER X
CONSTRUCTION AND TESTS OF THE LARGE ENGINE
The main requirement in an engine for an aerodrome—aside from
reliability and smoothness of operation, which are necessary in an engine
for any kind of locomotion—is that it shall develop the greatest amount of
power for the least weight. It is, therefore, desirable to reduce the weight
and number of parts of the engine to the very minimum, so far as this can be
done without sacrificing reliability and smoothness of running.
Furthermore, since the strongest metal for its weight is steel, and since the
greatest strength of steel is utilized when the stress acting on it is one of
tension, it is advisable to design the engine so that the parts which sustain
the greatest strains shall be of steel and, as far as possible, meet with strains
which are purely tensional ones.
In designing the new engine for the large aerodrome it was, therefore,
planned to make it entirely of steel, as far as this was possible. The only
parts which were not of steel were the bronze bushings for the bearings, the
cast-iron pistons, and cast-iron liners of the cylinders. Previous experience
had shown that, while it is possible to use a cast-iron piston in a steel
cylinder or even a steel piston in a steel cylinder, provided the lubrication
be kept exactly adjusted, yet the proper lubrication of the piston and
cylinder of a gas engine is difficult even under the most favorable
conditions, owing to the fact that excessive lubrication causes trouble from
the surplus oil interfering with the sparking apparatus. It was, therefore,
determined not to risk serious trouble by attempting to have the pistons bear
directly on the steel walls of the cylinders.
While visiting the French engine builders in the summer of 1900 in the
attempt to find one willing to undertake the construction of a suitable
engine for the aerodrome, it was pointed out to them that the great amount
of weight which they claimed to be necessary for the cylinders, and which
they stated made it impossible for them to build an engine which would
Page 420
meet the requirements as to power and weight, could be very greatly
reduced by making the cylinders in the form of thin steel shells having cast-
iron linings. All, however, to whom this suggestion was made declared that
it was impossible to build satisfactory cylinders in this way; some of them
even stated that they had tried it and found it impossible to keep the thin
liners tight in the steel shells. The difficulty which they had encountered is
due to the difference in expansion of the steel and the iron when raised to a
rather high temperature by the heat of the explosions, if the cylinders are
not well jacketed with water; and if the steel [p235] shells are water jacketed
they then do not expand as much as the cast-iron liners, and this causes the
latter to become “out of round” because of the compression strains
produced in them when trying to expand more than the steel shells. As past
experience had shown, however, that it was possible to keep the liners tight
in small cylinders, it was believed that by taking proper care in the
construction there would be no difficulty in this respect with the cylinders
of this larger engine.
In carrying out these plans, however, of making the cylinders of steel,
numerous constructional difficulties were encountered which could not be
foreseen when the design was made. Had they been foreseen, provision for
obviating them could easily have been made. As will be seen from the
drawing, Plate 78, the engine cylinders consisted primarily of a main outer
shell of steel one-sixteenth of an inch thick, near the bottom end of which
was screwed and brazed a suitable flange, by which it was bolted to the
supporting drum or crank chamber. These shells, which were seamless, with
the heads formed integral, were designed to be of sufficient strength to
withstand the force of the explosion in them, and, in order to provide a
suitable wearing surface for the piston, a cast-iron liner one-sixteenth of an
inch thick was carefully shrunk into them. Entering the side of the cylinder
near the top, was the combustion chamber, machined out of a solid steel
forging, which also formed the port which entered the cylinder and was
fastened to it by brazing. The water jackets, which were formed of sheet
steel .020 inch thick, were also fastened to the cylinder by brazing, and it
was in connection with the brazing of these water jackets that the first
reduced by making the cylinders in the form of thin steel shells having cast-
iron linings. All, however, to whom this suggestion was made declared that
it was impossible to build satisfactory cylinders in this way; some of them
even stated that they had tried it and found it impossible to keep the thin
liners tight in the steel shells. The difficulty which they had encountered is
due to the difference in expansion of the steel and the iron when raised to a
rather high temperature by the heat of the explosions, if the cylinders are
not well jacketed with water; and if the steel [p235] shells are water jacketed
they then do not expand as much as the cast-iron liners, and this causes the
latter to become “out of round” because of the compression strains
produced in them when trying to expand more than the steel shells. As past
experience had shown, however, that it was possible to keep the liners tight
in small cylinders, it was believed that by taking proper care in the
construction there would be no difficulty in this respect with the cylinders
of this larger engine.
In carrying out these plans, however, of making the cylinders of steel,
numerous constructional difficulties were encountered which could not be
foreseen when the design was made. Had they been foreseen, provision for
obviating them could easily have been made. As will be seen from the
drawing, Plate 78, the engine cylinders consisted primarily of a main outer
shell of steel one-sixteenth of an inch thick, near the bottom end of which
was screwed and brazed a suitable flange, by which it was bolted to the
supporting drum or crank chamber. These shells, which were seamless, with
the heads formed integral, were designed to be of sufficient strength to
withstand the force of the explosion in them, and, in order to provide a
suitable wearing surface for the piston, a cast-iron liner one-sixteenth of an
inch thick was carefully shrunk into them. Entering the side of the cylinder
near the top, was the combustion chamber, machined out of a solid steel
forging, which also formed the port which entered the cylinder and was
fastened to it by brazing. The water jackets, which were formed of sheet
steel .020 inch thick, were also fastened to the cylinder by brazing, and it
was in connection with the brazing of these water jackets that the first
Page 421
serious difficulty was met in the construction of the engine. In the first
place, as the jackets were of an irregular shape and of a different thickness
of metal from the walls of the cylinder to which they were joined, the
expansion and contraction due to the extreme heat necessary for properly
brazing the joints caused such serious strains in various and unexpected
directions that it was only by exercising the very greatest care and patience
that a completely tight joint at all points of the jacket could be secured. In
the second place, the size of the cylinders and the consequently large extent
of water-jacket surface, complicated the problem. The maintenance over
this large surface of the extreme heat necessary for brazing involved
discomfort and, indeed, actual suffering to the person engaged in the work,
and much care and skill were demanded in so distributing the heat that the
temperature of the surface of the jackets would be uniform enough to
prevent serious strains from expansion and contraction. As no workman
could be found either competent to do the work or willing to undergo the
personal discomfort, the writer was obliged to do all this brazing work
himself. Besides the difficulties due to the expansion and contraction of the
jackets while they were being brazed, the greatest care had to be exercised
to avoid heating the cylinders so hot as to weaken the [p236] joint where the
explosion chambers were joined to the cylinders, which, of course, had
been brazed before the jackets were fitted to them preparatory to brazing
them.
Another great difficulty was that the ring which encircled the cylinder
near the middle of its length, and which formed the bottom part of the water
jacket, expanded very much more than the cylinder itself, so that, if it was
brazed to the cylinder before the jacket was brazed to it, the heat of brazing
the jacket to the ring would cause the ring to break loose from the cylinder;
while if the ring was not previously brazed to the cylinder, but was brazed
after the jacket had been brazed to it, the very much greater heat required
for brazing the ring to the cylinder caused the spelter to burn out of the joint
between the jacket and the ring. Furthermore, it was found very difficult to
braze the two joints at the same time, since in brazing the ring to the
cylinder it was best to have the cylinder in an inverted vertical position, so
place, as the jackets were of an irregular shape and of a different thickness
of metal from the walls of the cylinder to which they were joined, the
expansion and contraction due to the extreme heat necessary for properly
brazing the joints caused such serious strains in various and unexpected
directions that it was only by exercising the very greatest care and patience
that a completely tight joint at all points of the jacket could be secured. In
the second place, the size of the cylinders and the consequently large extent
of water-jacket surface, complicated the problem. The maintenance over
this large surface of the extreme heat necessary for brazing involved
discomfort and, indeed, actual suffering to the person engaged in the work,
and much care and skill were demanded in so distributing the heat that the
temperature of the surface of the jackets would be uniform enough to
prevent serious strains from expansion and contraction. As no workman
could be found either competent to do the work or willing to undergo the
personal discomfort, the writer was obliged to do all this brazing work
himself. Besides the difficulties due to the expansion and contraction of the
jackets while they were being brazed, the greatest care had to be exercised
to avoid heating the cylinders so hot as to weaken the [p236] joint where the
explosion chambers were joined to the cylinders, which, of course, had
been brazed before the jackets were fitted to them preparatory to brazing
them.
Another great difficulty was that the ring which encircled the cylinder
near the middle of its length, and which formed the bottom part of the water
jacket, expanded very much more than the cylinder itself, so that, if it was
brazed to the cylinder before the jacket was brazed to it, the heat of brazing
the jacket to the ring would cause the ring to break loose from the cylinder;
while if the ring was not previously brazed to the cylinder, but was brazed
after the jacket had been brazed to it, the very much greater heat required
for brazing the ring to the cylinder caused the spelter to burn out of the joint
between the jacket and the ring. Furthermore, it was found very difficult to
braze the two joints at the same time, since in brazing the ring to the
cylinder it was best to have the cylinder in an inverted vertical position, so
Page 422
that the spelter could be made to flow evenly around the ring and form a
fillet against the wall of the cylinder, while in brazing the jackets to the ring
it was best to have the cylinder in the reverse vertical position or lying on
its side so that the spelter could properly flow into this joint. Finally,
however, after what proved to be most exasperating and tedious work, the
five cylinders necessary for the engine were completed and a series of tests
was immediately made. During the course of these tests the water
circulation became obstructed in several instances, and the consequent high
temperature to which the cylinders and jackets were raised caused severe
strains in the jackets which, in turn, produced breaks in the brazed joints.
These breaks had to be rebrazed, and in brazing them it was necessary in
almost every case to remove the cast-iron liners and rebraze the entire
jackets from start to finish, as the application of the intense heat necessary
for brazing at any one point produced such severe strains that before the
break which was being repaired could be completed other breaks developed
at various points of the jacket. It was, therefore, necessary to get the whole
jacket up to a fairly uniform heat and complete the brazing while it was in
this condition, and then keep the whole cylinder at a uniform but gradually
decreasing temperature until it had sufficiently cooled off.
On account of these troubles with the water jackets and the cylinders, it
was decided to build some extra cylinders, not only because past experience
had suggested improvements in detail in the construction of the jackets,
which would prevent to a large extent the great troubles which had been
met with in the brazed joints, but also to insure having sufficient cylinders
to enable the engine to be always in working condition, even though several
of the cylinders might be out of commission from slight imperfections in
the jackets or at other points. While the construction of these new cylinders
involved a repetition of the arduous task of brazing, yet the minor
improvements which were introduced [p237] proved eminently successful in
providing against future troubles from leaky jackets.
fillet against the wall of the cylinder, while in brazing the jackets to the ring
it was best to have the cylinder in the reverse vertical position or lying on
its side so that the spelter could properly flow into this joint. Finally,
however, after what proved to be most exasperating and tedious work, the
five cylinders necessary for the engine were completed and a series of tests
was immediately made. During the course of these tests the water
circulation became obstructed in several instances, and the consequent high
temperature to which the cylinders and jackets were raised caused severe
strains in the jackets which, in turn, produced breaks in the brazed joints.
These breaks had to be rebrazed, and in brazing them it was necessary in
almost every case to remove the cast-iron liners and rebraze the entire
jackets from start to finish, as the application of the intense heat necessary
for brazing at any one point produced such severe strains that before the
break which was being repaired could be completed other breaks developed
at various points of the jacket. It was, therefore, necessary to get the whole
jacket up to a fairly uniform heat and complete the brazing while it was in
this condition, and then keep the whole cylinder at a uniform but gradually
decreasing temperature until it had sufficiently cooled off.
On account of these troubles with the water jackets and the cylinders, it
was decided to build some extra cylinders, not only because past experience
had suggested improvements in detail in the construction of the jackets,
which would prevent to a large extent the great troubles which had been
met with in the brazed joints, but also to insure having sufficient cylinders
to enable the engine to be always in working condition, even though several
of the cylinders might be out of commission from slight imperfections in
the jackets or at other points. While the construction of these new cylinders
involved a repetition of the arduous task of brazing, yet the minor
improvements which were introduced [p237] proved eminently successful in
providing against future troubles from leaky jackets.
Page 423
1 1
5 in Cylinder by 5 2 in Stroke Engine. Scale 2 Full Size.
PL. 78. ENGINE OF AERODROME A. SECTION THROUGH CYLINDER AND
DRUM ◊ lgr
5 in Cylinder by 5 2 in Stroke Engine. Scale 2 Full Size.
PL. 78. ENGINE OF AERODROME A. SECTION THROUGH CYLINDER AND
DRUM ◊ lgr
Page 424
1
5 in Cylinder Engine ( 4 Size)
PL. 79. ENGINE OF AERODROME A. END ELEVATION, PORT SIDE ◊ lgr
5 in Cylinder Engine ( 4 Size)
PL. 79. ENGINE OF AERODROME A. END ELEVATION, PORT SIDE ◊ lgr
Page 425
1
5 in Cylinder Engine ( 4 Full Size)
PL. 80. ENGINE OF AERODROME A. TOP PLAN ◊ lgr
5 in Cylinder Engine ( 4 Full Size)
PL. 80. ENGINE OF AERODROME A. TOP PLAN ◊ lgr
Page 426
1
Scale 4 Full Size
PL. 81 ENGINE OF AERODROME A.
ELEVATION STARBOARD BED PLATE,
SPARKING MECHANISM ◊ lgr
Scale 4 Full Size
PL. 81 ENGINE OF AERODROME A.
ELEVATION STARBOARD BED PLATE,
SPARKING MECHANISM ◊ lgr
Page 427
The general form of construction of the engine with the improved
cylinders will be readily understood from the drawings, Plates 78–81, in
which Plate 78 is a detail sectional view, previously referred to, through one
of the cylinders; Plate 79 is an end elevation of the port side, Plate 80 is a
plan view, and Plate 81 is an elevation of the starboard bed plate which
supports that side of the engine, and by which it was fastened to the
aerodrome frame, this view showing particularly the sparking apparatus
which was mounted on the bed plate. The engine consists primarily of a
single crank shaft provided with a single crank pin, the shaft having
bearings in a drum which consists essentially of two heads. Arranged
around the crank shaft and attached at equidistant points of the drum are
five cylinders. Mounted on the port side of the crank shaft and close to the
crank arm is a small gear, which through suitable gears mounted on the port
head of the drum drives a double-pointed cam which has a bearing on the
exterior of the hub of the drum. The ratio of these gears is such that the cam
is driven at one-quarter the speed of the crank shaft, and in the reverse
direction. Mounted on the exterior side of the port head of the drum are five
punch rods, the upper ends of which are within a sixty-fourth of an inch of
being in contact with the exhaust-valve stems of the cylinders, and on the
lower end of these rods are hardened-steel rollers which rest on the double-
pointed cam—this one cam thus serving to operate the exhaust valves of all
five of the cylinders. The port head of the drum is connected to the port bed
plate, by which it is supported, by means of a flanged bushing in which are
formed tongues and grooves which fit into corresponding grooves and
tongues formed in the hub of the drum, it being necessary to have a certain
amount of space between this bed plate and the head of the drum to provide
room for the exhaust-valve cam and its co-acting punch rods. The starboard
bed plate is fastened to the starboard head of the drum by bolts which draw
the web of the bed plate against the face of the drum. The sparking gears are
driven by means of a gear formed on a sleeve which telescopes over the hub
of the starboard drum, and has a bearing thereon, the end of the sleeve
terminating in a ring which is fastened to the crank shaft.
cylinders will be readily understood from the drawings, Plates 78–81, in
which Plate 78 is a detail sectional view, previously referred to, through one
of the cylinders; Plate 79 is an end elevation of the port side, Plate 80 is a
plan view, and Plate 81 is an elevation of the starboard bed plate which
supports that side of the engine, and by which it was fastened to the
aerodrome frame, this view showing particularly the sparking apparatus
which was mounted on the bed plate. The engine consists primarily of a
single crank shaft provided with a single crank pin, the shaft having
bearings in a drum which consists essentially of two heads. Arranged
around the crank shaft and attached at equidistant points of the drum are
five cylinders. Mounted on the port side of the crank shaft and close to the
crank arm is a small gear, which through suitable gears mounted on the port
head of the drum drives a double-pointed cam which has a bearing on the
exterior of the hub of the drum. The ratio of these gears is such that the cam
is driven at one-quarter the speed of the crank shaft, and in the reverse
direction. Mounted on the exterior side of the port head of the drum are five
punch rods, the upper ends of which are within a sixty-fourth of an inch of
being in contact with the exhaust-valve stems of the cylinders, and on the
lower end of these rods are hardened-steel rollers which rest on the double-
pointed cam—this one cam thus serving to operate the exhaust valves of all
five of the cylinders. The port head of the drum is connected to the port bed
plate, by which it is supported, by means of a flanged bushing in which are
formed tongues and grooves which fit into corresponding grooves and
tongues formed in the hub of the drum, it being necessary to have a certain
amount of space between this bed plate and the head of the drum to provide
room for the exhaust-valve cam and its co-acting punch rods. The starboard
bed plate is fastened to the starboard head of the drum by bolts which draw
the web of the bed plate against the face of the drum. The sparking gears are
driven by means of a gear formed on a sleeve which telescopes over the hub
of the starboard drum, and has a bearing thereon, the end of the sleeve
terminating in a ring which is fastened to the crank shaft.
Page 428
Since the five connecting rods must center on the one crank pin, the
bronze shoes in which they terminate can occupy only a portion of the
circumference of the pin, and with the relative proportions which here
existed between the length of stroke of crank and the length of the
connecting rod, the circumferential width of the connecting-rod shoes was
slightly less than sixty degrees, thus leaving uncovered a crank space of
about one-sixth of the circumference, which it was necessary to have in
order to provide room for the change in relative position of the shoes due to
the angularity of the connecting rods. In [p238] the experimental engine the
connecting-rod shoes were all given their bearing directly on the crank pin,
as heretofore described, being held in contact therewith by means of cone
nuts, which were screw-threaded to the crank pin, the taper of the cones
permitting adjustment for wear. This method of connecting these parts to
the crank pin is the usual plan of connecting three or more connecting rods
to one crank pin. So much trouble had been experienced with the water
jackets and with minor defects in the experimental engine that no long runs
had been possible with it, and consequently no trouble had been
experienced because of the small amount of bearing area provided by this
method of joining the connecting rods to the crank pin. When, however, the
new engine was completed it was found that after working at high power
for a few minutes the connecting-rod shoes heated so rapidly that it was
impossible to run the engine for more than ten or twelve minutes, the
excessive heating of the shoes causing a great diminution in power besides
the danger of serious damage if the tests were continued longer. At first this
defect seemed almost fatal, as there appeared to be no way of providing
sufficient bearing area for the five connecting rods on one crank pin.
Happily, however, the writer was able to overcome this defect by an
improved design which enables all five connecting rods to operate on the
one crank pin, and at the same time provides each with the full amount of
bearing area which it would have were it the only connecting rod operating
on the crank pin. This arrangement consists essentially of a main connecting
rod formed of a steel forging terminating in a sleeve which encircles the
crank pin and is provided with a bronze lining for giving a proper bearing
bronze shoes in which they terminate can occupy only a portion of the
circumference of the pin, and with the relative proportions which here
existed between the length of stroke of crank and the length of the
connecting rod, the circumferential width of the connecting-rod shoes was
slightly less than sixty degrees, thus leaving uncovered a crank space of
about one-sixth of the circumference, which it was necessary to have in
order to provide room for the change in relative position of the shoes due to
the angularity of the connecting rods. In [p238] the experimental engine the
connecting-rod shoes were all given their bearing directly on the crank pin,
as heretofore described, being held in contact therewith by means of cone
nuts, which were screw-threaded to the crank pin, the taper of the cones
permitting adjustment for wear. This method of connecting these parts to
the crank pin is the usual plan of connecting three or more connecting rods
to one crank pin. So much trouble had been experienced with the water
jackets and with minor defects in the experimental engine that no long runs
had been possible with it, and consequently no trouble had been
experienced because of the small amount of bearing area provided by this
method of joining the connecting rods to the crank pin. When, however, the
new engine was completed it was found that after working at high power
for a few minutes the connecting-rod shoes heated so rapidly that it was
impossible to run the engine for more than ten or twelve minutes, the
excessive heating of the shoes causing a great diminution in power besides
the danger of serious damage if the tests were continued longer. At first this
defect seemed almost fatal, as there appeared to be no way of providing
sufficient bearing area for the five connecting rods on one crank pin.
Happily, however, the writer was able to overcome this defect by an
improved design which enables all five connecting rods to operate on the
one crank pin, and at the same time provides each with the full amount of
bearing area which it would have were it the only connecting rod operating
on the crank pin. This arrangement consists essentially of a main connecting
rod formed of a steel forging terminating in a sleeve which encircles the
crank pin and is provided with a bronze lining for giving a proper bearing
Page 429
surface between the connecting rod and the crank pin, both the steel sleeve
and the bronze lining being split, but at right angles to each other, to permit
assembling them on the crank pin. This steel sleeve, the upper half of which
is formed integral with the main connecting rod is rounded off to a true
circle on its exterior circumference, except at the point where the rod joins
it. The other four connecting rods terminating in bronze shoes are then
caused to bear on the exterior of this sleeve, being held in contact therewith,
and permitted to have a sliding motion thereon sufficient to take care of the
variation in angularity of the connecting rods, by means of the cone nuts
which are screw-threaded to the sleeve and locked thereto by means of the
jam nuts, as shown in the drawings. The main connecting rod, of course,
acts in the same way as in the ordinary case where each cylinder has its
separate crank pin. The other four connecting rods deliver their effort to the
crank pin through the sleeve in which the first connecting rod terminates,
and they, therefore, do not receive any of the rubbing effect due to the
rotation of the crank pin, except that of slipping a very short distance over
the circumference of the sleeve during each revolution, the amount of
slipping depending on the angularity of the connecting rod. This improved
type of bearing was successful from the time of its first trial, and even in
later [p239] tests in which the engine was run for ten consecutive hours at full
power it showed no signs whatever of overheating. As this new form of
connecting-rod bearing for the crank pin had never been tried before, the
precaution was taken to leave the threads on the crank pin for the cone nuts,
so that if this new bearing should not prove successful the old plan of
having the connecting-rod shoes bear directly on the crank pin could be
reverted to. These threads are clearly seen in Plate 78 and were never
removed from the crank pin, though their removal would have added
considerably to the area of the bearing surface of the main connecting rod,
had more bearing surface seemed necessary.
The lubrication of the main crank-shaft bearing and of the crank pin was
effected by means of a small oil cup, fastened to the port bed plate, which
fed oil through a hole in the hub of the drum to a circular groove formed in
the bronze bushing in the hub. The crank shaft being hollow, a hole was
and the bronze lining being split, but at right angles to each other, to permit
assembling them on the crank pin. This steel sleeve, the upper half of which
is formed integral with the main connecting rod is rounded off to a true
circle on its exterior circumference, except at the point where the rod joins
it. The other four connecting rods terminating in bronze shoes are then
caused to bear on the exterior of this sleeve, being held in contact therewith,
and permitted to have a sliding motion thereon sufficient to take care of the
variation in angularity of the connecting rods, by means of the cone nuts
which are screw-threaded to the sleeve and locked thereto by means of the
jam nuts, as shown in the drawings. The main connecting rod, of course,
acts in the same way as in the ordinary case where each cylinder has its
separate crank pin. The other four connecting rods deliver their effort to the
crank pin through the sleeve in which the first connecting rod terminates,
and they, therefore, do not receive any of the rubbing effect due to the
rotation of the crank pin, except that of slipping a very short distance over
the circumference of the sleeve during each revolution, the amount of
slipping depending on the angularity of the connecting rod. This improved
type of bearing was successful from the time of its first trial, and even in
later [p239] tests in which the engine was run for ten consecutive hours at full
power it showed no signs whatever of overheating. As this new form of
connecting-rod bearing for the crank pin had never been tried before, the
precaution was taken to leave the threads on the crank pin for the cone nuts,
so that if this new bearing should not prove successful the old plan of
having the connecting-rod shoes bear directly on the crank pin could be
reverted to. These threads are clearly seen in Plate 78 and were never
removed from the crank pin, though their removal would have added
considerably to the area of the bearing surface of the main connecting rod,
had more bearing surface seemed necessary.
The lubrication of the main crank-shaft bearing and of the crank pin was
effected by means of a small oil cup, fastened to the port bed plate, which
fed oil through a hole in the hub of the drum to a circular groove formed in
the bronze bushing in the hub. The crank shaft being hollow, a hole was
Page 430
drilled through it in line with the groove in the bushing, and the oil was then
led from the interior of the crank shaft through a pipe connected to the plug
in the end thereof, and through a hole drilled in the crank arm to the hollow
crank pin. Small holes through the crank pin permitted oil to pass to the
exterior thereof and thus oil the bearing of the main connecting rod. Small
holes through the sleeve and bushing of the main connecting rod fed oil
under the shoes of the other four connecting rods, the small holes being
placed in oil grooves formed in the interior of the bronze bushing. The
lubrication of the pistons was effected by means of small crescent-shaped
oil cups fastened to the outer wall of the cylinders, which distributed the oil
equidistantly around the circumference of the pistons, through small tubes
which projected through corresponding holes drilled in the cylinder wall.
These oil cups for the cylinders were, while small, of sufficient size to
furnish a supply for approximately one hour, and were so positioned on
each cylinder as to have a gravity feed. It may be mentioned here that while
there were many parts of the engine which were of unprecedented lightness
there was nothing which excelled these oil cups in this respect, as they were
made of sheet steel .003 of an inch thick, riveted and soldered up. The
crank-shaft bearing in the starboard drum was oiled from an oil cup
mounted on the outside of the bed plate and connected by a pipe to a hole in
the inner wall of the drum, which was connected to the oil grooves in the
bronze bushing in the hub of the drum.
The first set of pistons for this engine were similar in design to those
shown in the assembled drawings, except that they had side walls and heads
which were twice as thick as those shown. These lighter pistons were
constructed later, and were just as good as the earlier and heavier ones. It
will be noted that the pistons have two deep but thin ribs reinforcing the
head. The pistons were slightly tapered from the middle, where they were
.005 inch smaller than the cylinder bore, toward the outer end, where they
were .0075 inch smaller [p240] than the bore. The outer piston ring was .0035
inch narrower than its groove, the second one .003 inch, the third .0025
inch, and the inner one .002 inch narrower than its groove. The rings were
bored one-sixteenth inch off center with the exterior surface, and had one-
led from the interior of the crank shaft through a pipe connected to the plug
in the end thereof, and through a hole drilled in the crank arm to the hollow
crank pin. Small holes through the crank pin permitted oil to pass to the
exterior thereof and thus oil the bearing of the main connecting rod. Small
holes through the sleeve and bushing of the main connecting rod fed oil
under the shoes of the other four connecting rods, the small holes being
placed in oil grooves formed in the interior of the bronze bushing. The
lubrication of the pistons was effected by means of small crescent-shaped
oil cups fastened to the outer wall of the cylinders, which distributed the oil
equidistantly around the circumference of the pistons, through small tubes
which projected through corresponding holes drilled in the cylinder wall.
These oil cups for the cylinders were, while small, of sufficient size to
furnish a supply for approximately one hour, and were so positioned on
each cylinder as to have a gravity feed. It may be mentioned here that while
there were many parts of the engine which were of unprecedented lightness
there was nothing which excelled these oil cups in this respect, as they were
made of sheet steel .003 of an inch thick, riveted and soldered up. The
crank-shaft bearing in the starboard drum was oiled from an oil cup
mounted on the outside of the bed plate and connected by a pipe to a hole in
the inner wall of the drum, which was connected to the oil grooves in the
bronze bushing in the hub of the drum.
The first set of pistons for this engine were similar in design to those
shown in the assembled drawings, except that they had side walls and heads
which were twice as thick as those shown. These lighter pistons were
constructed later, and were just as good as the earlier and heavier ones. It
will be noted that the pistons have two deep but thin ribs reinforcing the
head. The pistons were slightly tapered from the middle, where they were
.005 inch smaller than the cylinder bore, toward the outer end, where they
were .0075 inch smaller [p240] than the bore. The outer piston ring was .0035
inch narrower than its groove, the second one .003 inch, the third .0025
inch, and the inner one .002 inch narrower than its groove. The rings were
bored one-sixteenth inch off center with the exterior surface, and had one-
Page 431
eighth inch diameter of spring. They were of the lap-joint type, with the
sides of the laps carefully fitted and only one-sixty-fourth-inch clearance at
the ends of the laps to allow for thermal expansion. As no grinding facilities
were obtainable in Washington, the cylinders were carefully bored smooth
and free from taper, and the pistons were worn in to a perfect fit by running
them in by a belt for twenty-four hours, with copious oil supply.
The main connecting rod was 78 -inch diameter and solid, while the other
four were of the same diameter but with a 58 -inch hole in them. The gudgeon
pins in the pistons were hollow steel tubes 78 -inch diameter and case-
hardened, and were oiled entirely by the oil thrown off by centrifugal force
from the crank-pin bearing, the oil running along the connecting rods and
through suitable holes at the heads into oil grooves in the bronze bushings
in these heads.
Since on an engine for an aerodrome the best plan for releasing the
exhaust gases from the engine is to get rid of them as soon as possible, so
long as they are released behind the aviator and do not interfere with his
view in the direction of motion, it was decided to have the gases exhaust
immediately from the combustion chambers; but in order to prevent their
playing on and heating the main bearing of the crank shaft in the port drum
the combustion chambers were each provided with a chamber below the
exhaust-valve seat, with a side outlet therefrom. The manifold pipe through
which the gaseous mixture was supplied to the inlet valves of the engine
consisted of a tube bent to a circle and having five branch tubes, each
leading to one of the automatic inlet valves, which fitted removable cast-
iron seats fastened by a nut in the upper part of each combustion chamber.
The very small amount of clearance between the engine and the frame
necessitated that this pipe be cut in three places and joined by flanges in
order to properly assemble it on the engine when the latter was mounted in
the frame. The carburetor, which was placed near the rear of the aviator’s
car, was connected through suitable pipes to this circular inlet pipe, at a
point horizontally in line with the center of the shaft. The auxiliary air valve
sides of the laps carefully fitted and only one-sixty-fourth-inch clearance at
the ends of the laps to allow for thermal expansion. As no grinding facilities
were obtainable in Washington, the cylinders were carefully bored smooth
and free from taper, and the pistons were worn in to a perfect fit by running
them in by a belt for twenty-four hours, with copious oil supply.
The main connecting rod was 78 -inch diameter and solid, while the other
four were of the same diameter but with a 58 -inch hole in them. The gudgeon
pins in the pistons were hollow steel tubes 78 -inch diameter and case-
hardened, and were oiled entirely by the oil thrown off by centrifugal force
from the crank-pin bearing, the oil running along the connecting rods and
through suitable holes at the heads into oil grooves in the bronze bushings
in these heads.
Since on an engine for an aerodrome the best plan for releasing the
exhaust gases from the engine is to get rid of them as soon as possible, so
long as they are released behind the aviator and do not interfere with his
view in the direction of motion, it was decided to have the gases exhaust
immediately from the combustion chambers; but in order to prevent their
playing on and heating the main bearing of the crank shaft in the port drum
the combustion chambers were each provided with a chamber below the
exhaust-valve seat, with a side outlet therefrom. The manifold pipe through
which the gaseous mixture was supplied to the inlet valves of the engine
consisted of a tube bent to a circle and having five branch tubes, each
leading to one of the automatic inlet valves, which fitted removable cast-
iron seats fastened by a nut in the upper part of each combustion chamber.
The very small amount of clearance between the engine and the frame
necessitated that this pipe be cut in three places and joined by flanges in
order to properly assemble it on the engine when the latter was mounted in
the frame. The carburetor, which was placed near the rear of the aviator’s
car, was connected through suitable pipes to this circular inlet pipe, at a
point horizontally in line with the center of the shaft. The auxiliary air valve
Page 432
consisted of a sleeve rotatably mounted on the vertical pipe leading from
the carburetor to the manifold, holes in the sleeve being brought to coincide
more or less with holes in the vertical pipe, by the operator, when more or
less air was required or when he wished to vary the speed of the engine. The
cooling water for the jackets of the cylinders was led to them through a
circular manifold pipe on the starboard side connected by a vertical pipe
with the centrifugal pump situated at the lower point of the lower pyramid
of the aerodrome frame. The heated water was led from the jackets through
another [p241] circular manifold pipe on the port side, through two
connections to the radiating tubes at the front and rear, respectively, of the
cross-frame. These radiating tubes, which were provided with thin radiating
ribs soldered to them, finally led the cooled water to the tank situated in the
extreme rear of the aviator’s car, a suitable pipe from the bottom of this tank
being connected to the inlet side of the centrifugal pump. The centrifugal
pump was driven by means of a vertical shaft connected to the crank shaft
through a set of bevel gears which drove it at three times the speed of the
engine. The bearings through which these gears were connected were
mounted on the port bed plate, and in order to allow for a certain amount of
vibration between the engine and the pump this vertical connecting shaft
had a telescoping section connected through suitable splines.
The sparking apparatus comprised, first, a primary sparker similar to the
simplest form of such devices which have since come into common use,
where a cam driven by the engine co-acts with a pawl on the end of a
spring, but in this case, as this sparker was used for all five cylinders, the
cam was driven at a speed of two and one-half times that of the engine
shaft, thus making and breaking the primary circuit five times in each two
revolutions of the engine. Second, a spark coil, the primary terminals of
which were connected to the primary sparker and to a set of dry batteries.
Third, a secondary distributor consisting of a disc carrying a contact brush
and driven at a speed one-half that of the engine, this brush being constantly
connected through a contact ring to one of the terminals of the high-tension
side of the spark coil and running over the face of a five-section
commutator, each of the sections of which was connected to a spark plug,
the carburetor to the manifold, holes in the sleeve being brought to coincide
more or less with holes in the vertical pipe, by the operator, when more or
less air was required or when he wished to vary the speed of the engine. The
cooling water for the jackets of the cylinders was led to them through a
circular manifold pipe on the starboard side connected by a vertical pipe
with the centrifugal pump situated at the lower point of the lower pyramid
of the aerodrome frame. The heated water was led from the jackets through
another [p241] circular manifold pipe on the port side, through two
connections to the radiating tubes at the front and rear, respectively, of the
cross-frame. These radiating tubes, which were provided with thin radiating
ribs soldered to them, finally led the cooled water to the tank situated in the
extreme rear of the aviator’s car, a suitable pipe from the bottom of this tank
being connected to the inlet side of the centrifugal pump. The centrifugal
pump was driven by means of a vertical shaft connected to the crank shaft
through a set of bevel gears which drove it at three times the speed of the
engine. The bearings through which these gears were connected were
mounted on the port bed plate, and in order to allow for a certain amount of
vibration between the engine and the pump this vertical connecting shaft
had a telescoping section connected through suitable splines.
The sparking apparatus comprised, first, a primary sparker similar to the
simplest form of such devices which have since come into common use,
where a cam driven by the engine co-acts with a pawl on the end of a
spring, but in this case, as this sparker was used for all five cylinders, the
cam was driven at a speed of two and one-half times that of the engine
shaft, thus making and breaking the primary circuit five times in each two
revolutions of the engine. Second, a spark coil, the primary terminals of
which were connected to the primary sparker and to a set of dry batteries.
Third, a secondary distributor consisting of a disc carrying a contact brush
and driven at a speed one-half that of the engine, this brush being constantly
connected through a contact ring to one of the terminals of the high-tension
side of the spark coil and running over the face of a five-section
commutator, each of the sections of which was connected to a spark plug,
Page 433
the other high-tension terminal of the spark coil being, of course, grounded
on the engine frame. This sparking apparatus was first constructed by using
blocks of red fibre for insulation. After the engine was completed and was
being tested difficulties were met with in the sparking apparatus which at
that time appeared inexplicable. After a great deal of annoyance and loss of
time it was finally discovered that the red fibre was not as good an
insulating medium as it was supposed to be, owing to the zinc oxide used in
making it. In damp weather the sparking apparatus absolutely refused to
work, and it was found that the moisture in the air caused the zinc oxide in
the fibre to nullify its insulating qualities. This trouble, after being located,
was cured by substituting hard rubber for the red fibre.
At the time when this engine was built, as well as earlier when the
experimental engine was built, it was impossible to procure any wire which
had been properly insulated to withstand the high voltages necessary for the
connections between the high-tension side of the spark coil and the
secondary distributor, and from the secondary distributor to the spark plugs
in the cylinders. While at this time this appears a very simple matter, yet the
trouble experienced and [p242] the delays caused by the lack of such small
accessories which are now so easily procurable were very exasperating, and
it was finally necessary to insulate these wires by covering them with
several thicknesses of ordinary rubber tube of different diameters
telescoped over each other.
In the early tests of this new engine, which were made with it mounted
on a special testing frame and delivering its power to the water-absorption
dynamometers, the engine was operated without any fly wheels, and, so far
as its smoothness of operation was concerned and its ability to generate its
maximum power, it did not require any.
After the completion of the tests on the testing frame the engine was
assembled in the aerodrome frame, which was first mounted on the floor of
the launching car. The car itself was mounted on a short track in the shop,
which arrangement provided a smoothly rolling carriage which could be
utilized for measuring the thrust of the propellers by merely attaching a
spring balance between the rear of the car and a proper holding strap on the
on the engine frame. This sparking apparatus was first constructed by using
blocks of red fibre for insulation. After the engine was completed and was
being tested difficulties were met with in the sparking apparatus which at
that time appeared inexplicable. After a great deal of annoyance and loss of
time it was finally discovered that the red fibre was not as good an
insulating medium as it was supposed to be, owing to the zinc oxide used in
making it. In damp weather the sparking apparatus absolutely refused to
work, and it was found that the moisture in the air caused the zinc oxide in
the fibre to nullify its insulating qualities. This trouble, after being located,
was cured by substituting hard rubber for the red fibre.
At the time when this engine was built, as well as earlier when the
experimental engine was built, it was impossible to procure any wire which
had been properly insulated to withstand the high voltages necessary for the
connections between the high-tension side of the spark coil and the
secondary distributor, and from the secondary distributor to the spark plugs
in the cylinders. While at this time this appears a very simple matter, yet the
trouble experienced and [p242] the delays caused by the lack of such small
accessories which are now so easily procurable were very exasperating, and
it was finally necessary to insulate these wires by covering them with
several thicknesses of ordinary rubber tube of different diameters
telescoped over each other.
In the early tests of this new engine, which were made with it mounted
on a special testing frame and delivering its power to the water-absorption
dynamometers, the engine was operated without any fly wheels, and, so far
as its smoothness of operation was concerned and its ability to generate its
maximum power, it did not require any.
After the completion of the tests on the testing frame the engine was
assembled in the aerodrome frame, which was first mounted on the floor of
the launching car. The car itself was mounted on a short track in the shop,
which arrangement provided a smoothly rolling carriage which could be
utilized for measuring the thrust of the propellers by merely attaching a
spring balance between the rear of the car and a proper holding strap on the
Page 434
track. In the first tests of the engine under these conditions, it was found
that while the engine itself did not require any fly wheels, yet the lack of
them caused trouble with the transmission and propeller shafts, which,
while it had never been anticipated, was easily understood when it was
encountered. This difficulty was caused by the “reverse torque,” which
fluctuated from a maximum to a minimum five times during each double
revolution of the engine, and which set up fluctuating torsional strains of
such magnitude in the transmission and propeller shafts that the shafts
themselves became exceedingly hot after a few minutes operation of the
engine, and under more prolonged periods of operation these fluctuating
torsional strains caused a permanent twisting and bending of the shafts. The
transmission and propeller shafts were at first made of tubing one-sixteenth
of an inch thick, but these were abandoned both on account of the necessity
of abandoning the screw-thread method of attaching the flange couplings
and gears, and also because these shafts had been designed when it was
expected to transmit only twelve horse-power to each propeller, while the
increase of power in the large engine necessarily required much stronger
shafts. The first shafts which were actually tested in the frame were,
therefore, one and one-half inches in diameter by three-thirty-seconds of an
inch thick, the tubing having been one-thirty-second of an inch larger
originally and turned down to this size to insure a straight shaft. When these
shafts twisted under the action of the reverse torque of the engine, a very
much heavier set, practically twice as thick, were constructed. When used in
the tests these heavier shafts, while much stronger, still showed a large
amount of heating due to the fluctuating torsional strains.
Upon calculation it was found that by providing specially light fly wheels
the major portion of this reverse torque could be eliminated for a less
increase [p243] in weight than would be occasioned by sufficiently increasing
the thickness of the transmission and propeller shafts to safely stand it.
Since it was desired to concentrate as much as possible of the weight of the
fly wheels in the rims, the idea at once suggested itself of building them up
like a bicycle wheel by means of tangent spokes. Two steel automobile-
wheel rims were therefore procured thirty-three inches in diameter, and
that while the engine itself did not require any fly wheels, yet the lack of
them caused trouble with the transmission and propeller shafts, which,
while it had never been anticipated, was easily understood when it was
encountered. This difficulty was caused by the “reverse torque,” which
fluctuated from a maximum to a minimum five times during each double
revolution of the engine, and which set up fluctuating torsional strains of
such magnitude in the transmission and propeller shafts that the shafts
themselves became exceedingly hot after a few minutes operation of the
engine, and under more prolonged periods of operation these fluctuating
torsional strains caused a permanent twisting and bending of the shafts. The
transmission and propeller shafts were at first made of tubing one-sixteenth
of an inch thick, but these were abandoned both on account of the necessity
of abandoning the screw-thread method of attaching the flange couplings
and gears, and also because these shafts had been designed when it was
expected to transmit only twelve horse-power to each propeller, while the
increase of power in the large engine necessarily required much stronger
shafts. The first shafts which were actually tested in the frame were,
therefore, one and one-half inches in diameter by three-thirty-seconds of an
inch thick, the tubing having been one-thirty-second of an inch larger
originally and turned down to this size to insure a straight shaft. When these
shafts twisted under the action of the reverse torque of the engine, a very
much heavier set, practically twice as thick, were constructed. When used in
the tests these heavier shafts, while much stronger, still showed a large
amount of heating due to the fluctuating torsional strains.
Upon calculation it was found that by providing specially light fly wheels
the major portion of this reverse torque could be eliminated for a less
increase [p243] in weight than would be occasioned by sufficiently increasing
the thickness of the transmission and propeller shafts to safely stand it.
Since it was desired to concentrate as much as possible of the weight of the
fly wheels in the rims, the idea at once suggested itself of building them up
like a bicycle wheel by means of tangent spokes. Two steel automobile-
wheel rims were therefore procured thirty-three inches in diameter, and
Page 435
these were provided with tangent spokes connected to special steel hubs
fitted to the crank shaft of the engine. The rims themselves not being quite
heavy enough, and constructional reasons necessitating their being at
different distances from the center of length of the crank pin, the extra
weight which it was desired to give to these rims was provided by means of
steel wire wound tightly around and fastened to the rims, the weight of each
rim being made inversely proportional to its distance from the center of the
crank pin. The first spokes which were used for these wheels were standard
bicycle spokes three-thirty-seconds of an inch in diameter, but these were
soon found to be entirely too weak to withstand the sudden strains due to
the rapid starting of the engine. They were therefore replaced by standard
spokes one-eighth of an inch in diameter, but these also proved too weak
and were later replaced with special spokes made in the shop out of No. 10
coppered-steel wire, which by test was found to have a tensional strength of
2192 pounds. As these steel rims were only one-sixteenth of an inch thick
and had not been made exactly true, but had been straightened before being
used, it was found that they very quickly went out of shape under the strain
due to the centrifugal force at high speeds, and also when the engine was
suddenly accelerated. As long as they did stay true, however, it was found
that they were sufficiently heavy to provide all of the fly-wheel effect it was
necessary to have in order to eliminate all trouble from the reverse torque.
After further consideration, it was decided that the only means of
constructing a fly wheel which would have a stiff rim and at the same time
would not be heavier than the steel ones, which had been found adequate,
was by perpetrating what would at first sight appear to be an absurdity. A
new set of rims for the fly wheels was made by constructing them of an
aluminum casting, the section of the rim being U-shaped. After machining
these rims and assembling the fly wheels with them, it was found that they
were many times stiffer than the previous steel ones of the same weight, and
after this change no further trouble was experienced in keeping the fly
wheels perfectly true, even under the most severe strains. In fact, on one
occasion when the engine broke loose from the propellers, it ran to a speed,
fitted to the crank shaft of the engine. The rims themselves not being quite
heavy enough, and constructional reasons necessitating their being at
different distances from the center of length of the crank pin, the extra
weight which it was desired to give to these rims was provided by means of
steel wire wound tightly around and fastened to the rims, the weight of each
rim being made inversely proportional to its distance from the center of the
crank pin. The first spokes which were used for these wheels were standard
bicycle spokes three-thirty-seconds of an inch in diameter, but these were
soon found to be entirely too weak to withstand the sudden strains due to
the rapid starting of the engine. They were therefore replaced by standard
spokes one-eighth of an inch in diameter, but these also proved too weak
and were later replaced with special spokes made in the shop out of No. 10
coppered-steel wire, which by test was found to have a tensional strength of
2192 pounds. As these steel rims were only one-sixteenth of an inch thick
and had not been made exactly true, but had been straightened before being
used, it was found that they very quickly went out of shape under the strain
due to the centrifugal force at high speeds, and also when the engine was
suddenly accelerated. As long as they did stay true, however, it was found
that they were sufficiently heavy to provide all of the fly-wheel effect it was
necessary to have in order to eliminate all trouble from the reverse torque.
After further consideration, it was decided that the only means of
constructing a fly wheel which would have a stiff rim and at the same time
would not be heavier than the steel ones, which had been found adequate,
was by perpetrating what would at first sight appear to be an absurdity. A
new set of rims for the fly wheels was made by constructing them of an
aluminum casting, the section of the rim being U-shaped. After machining
these rims and assembling the fly wheels with them, it was found that they
were many times stiffer than the previous steel ones of the same weight, and
after this change no further trouble was experienced in keeping the fly
wheels perfectly true, even under the most severe strains. In fact, on one
occasion when the engine broke loose from the propellers, it ran to a speed,
Page 436
which, while not exactly known, yet reached the limit of the tachometer,
which was 2000 R. P. M., without injury to the fly wheels.
It will be recalled that in starting up the engine on the quarter-size model,
the initial “cranking” necessary with a gasoline engine was accomplished
by [p244] having two of the mechanics turn the propellers. While this same
plan might have been followed in the case of the large aerodrome, yet it
would have involved some danger to the mechanics and would also have
left the aviator without any means of restarting the engine should it for any
reason stop while in the air. Believing it to be very important to provide
means for enabling the aviator to restart the engine in case it stopped in the
air, the writer devised the starting mechanism shown in the drawings, Plates
78 to 80. Fastened by tongues and grooves to the port side of the engine
crank shaft, just outside of the bed plate, is a worm wheel, on the hub of
which is mounted the bevel gear which drives the water-circulation pump
through the bevel pinion, as already described. Mounted on the web of the
bed plate are two brackets, in which the shaft for the starting crank is
journaled, this shaft passing forward and downward through the front of the
cross-frame of the aerodrome, where it is journaled in a bracket secured to
the brace tubes thereof. At the front or lower end of the shaft a crank handle
is connected thereto by a ratchet mechanism. The upper end of the starting
shaft, between the bearings of the two supporting brackets, is tongued and
grooved, and slidably mounted thereon with co-acting grooves and tongues
is a worm screw which, in the position shown in Plates 79 and 80, is in gear
with the worm wheel just described. However, when the worm screw is slid
along on the shaft until it is against the upper bracket it is out of gear with
the worm wheel. Mounted in the interior of the tubular starting shaft is a
spring-pressed pawl plug, not shown, but which projects through one of the
tongues on the shaft near the upper bracket. If the worm screw is slid up
against this upper bracket, this pawl catches in a radial hole in the worm
screw and holds it in this position out of gear with the worm wheel.
Connected to this pawl plug and passing longitudinally through the center
of the shaft is a wire which terminates in a button just at the end thereof. By
pulling on this button the operator may release the worm and thus permit it
which was 2000 R. P. M., without injury to the fly wheels.
It will be recalled that in starting up the engine on the quarter-size model,
the initial “cranking” necessary with a gasoline engine was accomplished
by [p244] having two of the mechanics turn the propellers. While this same
plan might have been followed in the case of the large aerodrome, yet it
would have involved some danger to the mechanics and would also have
left the aviator without any means of restarting the engine should it for any
reason stop while in the air. Believing it to be very important to provide
means for enabling the aviator to restart the engine in case it stopped in the
air, the writer devised the starting mechanism shown in the drawings, Plates
78 to 80. Fastened by tongues and grooves to the port side of the engine
crank shaft, just outside of the bed plate, is a worm wheel, on the hub of
which is mounted the bevel gear which drives the water-circulation pump
through the bevel pinion, as already described. Mounted on the web of the
bed plate are two brackets, in which the shaft for the starting crank is
journaled, this shaft passing forward and downward through the front of the
cross-frame of the aerodrome, where it is journaled in a bracket secured to
the brace tubes thereof. At the front or lower end of the shaft a crank handle
is connected thereto by a ratchet mechanism. The upper end of the starting
shaft, between the bearings of the two supporting brackets, is tongued and
grooved, and slidably mounted thereon with co-acting grooves and tongues
is a worm screw which, in the position shown in Plates 79 and 80, is in gear
with the worm wheel just described. However, when the worm screw is slid
along on the shaft until it is against the upper bracket it is out of gear with
the worm wheel. Mounted in the interior of the tubular starting shaft is a
spring-pressed pawl plug, not shown, but which projects through one of the
tongues on the shaft near the upper bracket. If the worm screw is slid up
against this upper bracket, this pawl catches in a radial hole in the worm
screw and holds it in this position out of gear with the worm wheel.
Connected to this pawl plug and passing longitudinally through the center
of the shaft is a wire which terminates in a button just at the end thereof. By
pulling on this button the operator may release the worm and thus permit it
Page 437
to slide downward so that when the starting crank is turned in a clockwise
direction the worm will screw itself into gear with the worm wheel, and any
further turning of the starting crank will cause the worm to force the worm
wheel, and, consequently, the engine shaft, around in a clockwise direction.
As soon as the engine gets an explosion the worm wheel slides the worm
along against the upper bracket, where the spring pawl catches and holds it
till it is again released by the operator as before.
This starting mechanism was a success from the first, and the engine was
never started up in any other way. With an aerodrome having the qualities
of automatic equilibrium, which the Langley machines have, it was felt very
certain that by this mechanism the engine could be easily restarted while in
the air, in case it was inadvertently stopped. [p245]
The reason for building the engine with five cylinders instead of some
other number, and for arranging them radially on a central drum using only
one crank pin may not appear quite obvious. The advantages gained by such
a construction, however, are very great, and may be briefly summed up as
follows:
First, since in a gas engine of the four-cycle type there is only one
explosion in each cylinder every two revolutions, and the crank shaft and
crank pin therefore are loaded only one-quarter of the time for each
cylinder, it is obvious that by having four cylinders arranged radially around
a central drum the load on the bearings of a single crank shaft and crank pin
may be kept very uniform. However, with four cylinders thus arranged it is
impossible to have the cylinders explode and exert their effort on the crank
at uniform intervals in the cycle, it being necessary to have the cylinders
explode in the order of 1, 3, 4, 2, 1, etc., thus giving intervals between
explosions of 180 degrees, 90 degrees, 180 degrees, 270 degrees, etc., or to
have them explode in the order of 1, 3, 2, 4, 1, etc., thus giving intervals of
180 degrees, 270 degrees, 180 degrees, 90 degrees, etc. On the other hand,
with any odd number of cylinders the explosions will occur at equal
intervals in the cycle. With three cylinders they will explode in the order of
1, 3, 2, 1, etc., or at equal intervals of 240 degrees, while with five cylinders
they will explode in the order of 1, 3, 5, 2, 4, 1, etc., or at equal intervals of
direction the worm will screw itself into gear with the worm wheel, and any
further turning of the starting crank will cause the worm to force the worm
wheel, and, consequently, the engine shaft, around in a clockwise direction.
As soon as the engine gets an explosion the worm wheel slides the worm
along against the upper bracket, where the spring pawl catches and holds it
till it is again released by the operator as before.
This starting mechanism was a success from the first, and the engine was
never started up in any other way. With an aerodrome having the qualities
of automatic equilibrium, which the Langley machines have, it was felt very
certain that by this mechanism the engine could be easily restarted while in
the air, in case it was inadvertently stopped. [p245]
The reason for building the engine with five cylinders instead of some
other number, and for arranging them radially on a central drum using only
one crank pin may not appear quite obvious. The advantages gained by such
a construction, however, are very great, and may be briefly summed up as
follows:
First, since in a gas engine of the four-cycle type there is only one
explosion in each cylinder every two revolutions, and the crank shaft and
crank pin therefore are loaded only one-quarter of the time for each
cylinder, it is obvious that by having four cylinders arranged radially around
a central drum the load on the bearings of a single crank shaft and crank pin
may be kept very uniform. However, with four cylinders thus arranged it is
impossible to have the cylinders explode and exert their effort on the crank
at uniform intervals in the cycle, it being necessary to have the cylinders
explode in the order of 1, 3, 4, 2, 1, etc., thus giving intervals between
explosions of 180 degrees, 90 degrees, 180 degrees, 270 degrees, etc., or to
have them explode in the order of 1, 3, 2, 4, 1, etc., thus giving intervals of
180 degrees, 270 degrees, 180 degrees, 90 degrees, etc. On the other hand,
with any odd number of cylinders the explosions will occur at equal
intervals in the cycle. With three cylinders they will explode in the order of
1, 3, 2, 1, etc., or at equal intervals of 240 degrees, while with five cylinders
they will explode in the order of 1, 3, 5, 2, 4, 1, etc., or at equal intervals of
Page 438
144 degrees. It is therefore seen that there is a great advantage in
smoothness of operation and uniformity of torque of the engine through
having an odd number of cylinders instead of an even number.
Second, it is readily apparent that the greater the number of cylinders,
provided the number is an odd one, the more uniform the torque will be,
and it would seem at first that seven cylinders would therefore be better
than five, since the uniform intervals between explosions with seven
cylinders would be only 103 degrees (approximately). The advantage
gained, however, through seven cylinders instead of five is largely, if not
completely, counterbalanced by the added number of parts and the difficulty
of providing sufficient circumferencial width for the connecting-rod shoes
on the crank-pin bearing, even with the improved construction of this
bearing already described. There is considerable fluctuation of the torque in
each revolution of the engine with five cylinders, but this fluctuation of
torque is more easily smoothed out by the use of very light fly wheels than
by increasing the number of cylinders, and thus adding to the complication
of the engine.
Third, the strongest point in favor of the radially arranged cylinders is the
reduction in weight and complication which it permits. The crank shaft is
reduced to the very minimum, there being only one crank pin with two
main bearings which can, without any difficulty whatever, be kept
absolutely in line with each other and thus prevent binding and loss of
power. Again, the use of a single-throw crank not only reduces the cost and
weight of the crank [p246] itself, but makes it very much less liable to
damage; long crank shafts with several crank pins being frequently twisted
by improper explosions in the cylinders. The supporting drum or crank
chamber is likewise reduced to the very minimum, both in weight and
simplicity, the drums being perfectly symmetrical with no lost space either
inside of them or on their exteriors. The cam mechanism for operating the
valves is reduced to a simple ring carrying (for a five-cylinder engine) a
double-pointed cam and journaled on the exterior of the hub of one of the
drums, the cam being driven by a train of gears journaled on studs mounted
smoothness of operation and uniformity of torque of the engine through
having an odd number of cylinders instead of an even number.
Second, it is readily apparent that the greater the number of cylinders,
provided the number is an odd one, the more uniform the torque will be,
and it would seem at first that seven cylinders would therefore be better
than five, since the uniform intervals between explosions with seven
cylinders would be only 103 degrees (approximately). The advantage
gained, however, through seven cylinders instead of five is largely, if not
completely, counterbalanced by the added number of parts and the difficulty
of providing sufficient circumferencial width for the connecting-rod shoes
on the crank-pin bearing, even with the improved construction of this
bearing already described. There is considerable fluctuation of the torque in
each revolution of the engine with five cylinders, but this fluctuation of
torque is more easily smoothed out by the use of very light fly wheels than
by increasing the number of cylinders, and thus adding to the complication
of the engine.
Third, the strongest point in favor of the radially arranged cylinders is the
reduction in weight and complication which it permits. The crank shaft is
reduced to the very minimum, there being only one crank pin with two
main bearings which can, without any difficulty whatever, be kept
absolutely in line with each other and thus prevent binding and loss of
power. Again, the use of a single-throw crank not only reduces the cost and
weight of the crank [p246] itself, but makes it very much less liable to
damage; long crank shafts with several crank pins being frequently twisted
by improper explosions in the cylinders. The supporting drum or crank
chamber is likewise reduced to the very minimum, both in weight and
simplicity, the drums being perfectly symmetrical with no lost space either
inside of them or on their exteriors. The cam mechanism for operating the
valves is reduced to a simple ring carrying (for a five-cylinder engine) a
double-pointed cam and journaled on the exterior of the hub of one of the
drums, the cam being driven by a train of gears journaled on studs mounted
Page 439
on the drum, and co-acting with a gear fastened to the crank shaft against
the crank arm.
The radial arrangement of the cylinders is thus seen to give not only an
engine with the smallest number of parts, each of which is as far as possible
worked to a uniform amount during each complete revolution of the crank
shaft, but it also gives a very compact and readily accessible mechanism
with its center of gravity coincident with its center of figure, and with the
liability of damage to it, in case of a smash of the vehicle on which it is
used, reduced to the minimum from the fact that the greatest weight is
located at the strongest part.
Fourth, and of almost as great importance as the reduction in weight
which the five-cylinder radial arrangement permits, is its unusual qualities
as regards vibration. Since these five-cylinder engines were built by the
writer a very thorough treatment of their properties as regards balancing has
been given in a treatise on the balancing of engines,44 so no discussion of
the mathematical formulæ involved in a study of the question of the
inherent balancing properties of these engines will be here given. It is
sufficient to call attention to the fact that in an engine having five cylinders
arranged radially, all of the reciprocating parts are balanced for all forces of
the first, second and third orders. As it is only the reciprocating parts which
give any trouble in balancing any engine, the unbalanced rotating parts
being readily balanced by placing an equal weight at an equal distance from
the center of rotation, and on the opposite side thereof, it is readily seen that
the properties of balancing which are inherent in this type of engine are
unusual. A six-cylinder engine having a six-throw crank shaft is not nearly
so thoroughly balanced as this type having its five cylinders radially
arranged, for in the latter case all the moving parts are in one plane, while in
the former case the moving parts are in six separate and parallel planes, and
there is consequently considerable longitudinal vibration which can never
be overcome. While this is true as regards the vibration due to moving
masses, it is still more impressively true as regards vibration due to reaction
arising from the force of the explosions in the engine cylinders, especially
when the engine is running slowly and having heavy explosions.
the crank arm.
The radial arrangement of the cylinders is thus seen to give not only an
engine with the smallest number of parts, each of which is as far as possible
worked to a uniform amount during each complete revolution of the crank
shaft, but it also gives a very compact and readily accessible mechanism
with its center of gravity coincident with its center of figure, and with the
liability of damage to it, in case of a smash of the vehicle on which it is
used, reduced to the minimum from the fact that the greatest weight is
located at the strongest part.
Fourth, and of almost as great importance as the reduction in weight
which the five-cylinder radial arrangement permits, is its unusual qualities
as regards vibration. Since these five-cylinder engines were built by the
writer a very thorough treatment of their properties as regards balancing has
been given in a treatise on the balancing of engines,44 so no discussion of
the mathematical formulæ involved in a study of the question of the
inherent balancing properties of these engines will be here given. It is
sufficient to call attention to the fact that in an engine having five cylinders
arranged radially, all of the reciprocating parts are balanced for all forces of
the first, second and third orders. As it is only the reciprocating parts which
give any trouble in balancing any engine, the unbalanced rotating parts
being readily balanced by placing an equal weight at an equal distance from
the center of rotation, and on the opposite side thereof, it is readily seen that
the properties of balancing which are inherent in this type of engine are
unusual. A six-cylinder engine having a six-throw crank shaft is not nearly
so thoroughly balanced as this type having its five cylinders radially
arranged, for in the latter case all the moving parts are in one plane, while in
the former case the moving parts are in six separate and parallel planes, and
there is consequently considerable longitudinal vibration which can never
be overcome. While this is true as regards the vibration due to moving
masses, it is still more impressively true as regards vibration due to reaction
arising from the force of the explosions in the engine cylinders, especially
when the engine is running slowly and having heavy explosions.
Page 440
The usual practice in balancing the rotating parts of an engine is to attach
[p247] balance weights to the crank arms which are prolonged beyond the
center of the crank shaft and on the opposite side from the crank pin; the
radius of rotation of these balance weights being made approximately equal
to the radius of the crank pin. But aside from the constructional difficulties
which would be introduced, it was seen that if this plan was followed in this
engine it would require a very large additional weight. Since the amount of
this weight could be diminished in exact proportion to the increase of the
radius of rotation of the balance weights, it was at first decided to attach the
weights to the rims of the fly wheels, the relative amount of weight attached
to each wheel being inversely proportional to its actual longitudinal
distance from the crank-pin center. It was very soon found that the
attachment of these balance weights to the fly wheel caused excessive
strains on the rims of the wheels, thereby causing them to go out of line. In
order, therefore, to keep the amount of balance weight small by carrying it
at a considerable distance from the center of the shaft, the weights were
finally arranged as clearly shown in the drawings, Plates 78 to 80. There it
is seen that the main portion of each of the balance weights consists of a flat
arm bolted between the flanges which couple the transmission shafts to the
engine shafts. The flat arm terminates in a lozenge-shaped lug, additional
weight being provided by a plate fastened to one end of a tube, the other
end of which terminates in a collar fastened around the transmission shaft.
The tube is inclined at an angle of about thirty degrees with the flat balance
arm, thus acting as a brace to prevent the balance arm from wobbling, the
plate on the bracing tube being fastened to the lozenge-shaped lug by means
of small bolts.
The tabulated statement of the weight of this large engine is given below.
From this it will be readily seen that the net weight of the engine proper is
124.17 pounds. The fly wheels were in no way necessary to the engine
itself, but were used solely for the purpose of smoothing out the torque of
the engine so that the transmission shafts and propeller shafts might be kept
down to the very minimum in weight. Including the two fly wheels, the
weight is 140 pounds.
[p247] balance weights to the crank arms which are prolonged beyond the
center of the crank shaft and on the opposite side from the crank pin; the
radius of rotation of these balance weights being made approximately equal
to the radius of the crank pin. But aside from the constructional difficulties
which would be introduced, it was seen that if this plan was followed in this
engine it would require a very large additional weight. Since the amount of
this weight could be diminished in exact proportion to the increase of the
radius of rotation of the balance weights, it was at first decided to attach the
weights to the rims of the fly wheels, the relative amount of weight attached
to each wheel being inversely proportional to its actual longitudinal
distance from the crank-pin center. It was very soon found that the
attachment of these balance weights to the fly wheel caused excessive
strains on the rims of the wheels, thereby causing them to go out of line. In
order, therefore, to keep the amount of balance weight small by carrying it
at a considerable distance from the center of the shaft, the weights were
finally arranged as clearly shown in the drawings, Plates 78 to 80. There it
is seen that the main portion of each of the balance weights consists of a flat
arm bolted between the flanges which couple the transmission shafts to the
engine shafts. The flat arm terminates in a lozenge-shaped lug, additional
weight being provided by a plate fastened to one end of a tube, the other
end of which terminates in a collar fastened around the transmission shaft.
The tube is inclined at an angle of about thirty degrees with the flat balance
arm, thus acting as a brace to prevent the balance arm from wobbling, the
plate on the bracing tube being fastened to the lozenge-shaped lug by means
of small bolts.
The tabulated statement of the weight of this large engine is given below.
From this it will be readily seen that the net weight of the engine proper is
124.17 pounds. The fly wheels were in no way necessary to the engine
itself, but were used solely for the purpose of smoothing out the torque of
the engine so that the transmission shafts and propeller shafts might be kept
down to the very minimum in weight. Including the two fly wheels, the
weight is 140 pounds.
Page 441
Including the 20 pounds of cooling water the total weight of the power
plant is 207.47 pounds. Without flywheels the total weight is 191.64
pounds.
The construction of this large engine was completed in December, 1901,
and the first tests of it were made in January, 1902. As already stated, these
first tests were made with the engine mounted on a special testing frame
and delivering its power to two water-absorption dynamometers, no fly
wheels being used, as none were required. Later, when it became necessary
either to use fly wheels or to greatly increase the weight of the transmission
and propeller shafts, in order to overcome the reverse torque, the two light
fly wheels were added, and another series of tests was made of the engine
on its testing frame. The arrangement of the engine, dynamometers, and
accessory [p248] apparatus is clearly shown in Plates 82, 83 and 84. The
engine ran in a clockwise direction, as viewed in Plate 82. AA are the fly
wheels; BB the balance weights; CC the dynamometer shafts, on which are
fastened the rotor plates which revolve inside of the dynamometer drums,
DD, between stator plates fastened therein. The drums have a hub on either
side, by which they are supported, these hubs being journaled on ball-
bearings in the pedestals resting on the wooden framework. The rotor plates
do not touch the stator plates in the dynamometers, but drag on the water
with which the drums are partially filled, and thus tend to cause the drums
to revolve around with them. The torque on each drum is measured by
means of a rope, not shown, fastened into the hook at the top of the drum,
the rope being given a partial coil around the drum and passing off tangent
thereto at the horizontal diameter is fastened to a pair of spring scales hung
from the ceiling vertically above the point of tangency. The scales and ropes
were unfortunately not in position when these photographs were taken, but
the arrangement of them should be readily understood. As the friction of the
rotor plates on the water heats it in exact proportion to the amount of power
absorbed, the small amount of water in the drums would be soon converted
into steam unless continually renewed or cooled. When the rotor plates are
revolving the centrifugal force keeps the water pressed toward the
circumference of the drum, and the friction at any speed is dependent on the
plant is 207.47 pounds. Without flywheels the total weight is 191.64
pounds.
The construction of this large engine was completed in December, 1901,
and the first tests of it were made in January, 1902. As already stated, these
first tests were made with the engine mounted on a special testing frame
and delivering its power to two water-absorption dynamometers, no fly
wheels being used, as none were required. Later, when it became necessary
either to use fly wheels or to greatly increase the weight of the transmission
and propeller shafts, in order to overcome the reverse torque, the two light
fly wheels were added, and another series of tests was made of the engine
on its testing frame. The arrangement of the engine, dynamometers, and
accessory [p248] apparatus is clearly shown in Plates 82, 83 and 84. The
engine ran in a clockwise direction, as viewed in Plate 82. AA are the fly
wheels; BB the balance weights; CC the dynamometer shafts, on which are
fastened the rotor plates which revolve inside of the dynamometer drums,
DD, between stator plates fastened therein. The drums have a hub on either
side, by which they are supported, these hubs being journaled on ball-
bearings in the pedestals resting on the wooden framework. The rotor plates
do not touch the stator plates in the dynamometers, but drag on the water
with which the drums are partially filled, and thus tend to cause the drums
to revolve around with them. The torque on each drum is measured by
means of a rope, not shown, fastened into the hook at the top of the drum,
the rope being given a partial coil around the drum and passing off tangent
thereto at the horizontal diameter is fastened to a pair of spring scales hung
from the ceiling vertically above the point of tangency. The scales and ropes
were unfortunately not in position when these photographs were taken, but
the arrangement of them should be readily understood. As the friction of the
rotor plates on the water heats it in exact proportion to the amount of power
absorbed, the small amount of water in the drums would be soon converted
into steam unless continually renewed or cooled. When the rotor plates are
revolving the centrifugal force keeps the water pressed toward the
circumference of the drum, and the friction at any speed is dependent on the
Page 442
area of the rotor plates in contact with the water. The horse-power required
to revolve the plates at any definite speed can therefore be controlled by
having an outlet for the water at the proper radial distance from the shaft.
The water from the water mains is led through the upper vertical pipe and
allowed to flow into the funnel, and thence into the drum near the center
where the centrifugal force throws it to the circumference of the drum. The
lower vertical pipe is connected to the drum at a suitable radial distance
from the center, and the heated water thus passes through this pipe and into
the lower funnel connected to the sewer. By the use of the funnels the
drums are allowed to rock sufficiently to exert their pull on the spring scales
without being affected by the supply and exhaust of water.
to revolve the plates at any definite speed can therefore be controlled by
having an outlet for the water at the proper radial distance from the shaft.
The water from the water mains is led through the upper vertical pipe and
allowed to flow into the funnel, and thence into the drum near the center
where the centrifugal force throws it to the circumference of the drum. The
lower vertical pipe is connected to the drum at a suitable radial distance
from the center, and the heated water thus passes through this pipe and into
the lower funnel connected to the sewer. By the use of the funnels the
drums are allowed to rock sufficiently to exert their pull on the spring scales
without being affected by the supply and exhaust of water.
Page 443
PL. 82. DYNAMOMETER TESTS OF LARGE ENGINE ◊
Page 444
PL. 83. DYNAMOMETER TESTS OF LARGE ENGINE ◊
Page 445
PL. 84. DYNAMOMETER TESTS OF LARGE ENGINE ◊
Page 446
The water for cooling the cylinders is led from the bottom of the tank E
to the circulating pump F, supported in a discarded lower pyramid of the
aerodrome frame, the pump being driven by the small vertical shaft, as
already described. The water, after passing through the pump and the engine
cylinders, is led back to the upper part of the tank. By suitable connections
to the water mains and sewer, the water in the tank is kept at any desired
temperature. The gasoline supply tank is seen on the left-hand side of the
testing frame, as viewed in Plate 82, the carburetor being placed below it
and the gas supply pipe from the carburetor passing through the gasoline
tank. Instead of jacketing the carburetor, a grid formed of thin copper tubes
is supported just above the multitude of small air pipes leading into the
carburetor, and some of [p249] the hot water from the engine is by-passed
through this grid and thus warms the air as it passes into the carburetor. The
small pipe that by-passes this water through the grid is seen connected to
the outlet water pipe just above the cylinders, a small butterfly valve in the
outlet pipe enabling the amount of heated water passing through the grid to
be controlled. The return from the grid is by means of the small pipe
leading to the top of the large water tank. The tachometer, which gives
instantaneous readings of the speed of the engine, is seen at G, where it is at
all times in full view of the operator.
These dynamometers proved to be excellently suited for the testing work,
and far ahead of anything else the writer has ever found for engine testing.
Since the power required to rotate the rotor plates, with a uniform amount
of water in the drums, varies as the cube of the speed, it is readily seen that
it is impossible for the engine to race or injure itself by running away, as
frequently happens where there is no engine governor and Prony brakes are
used to measure the power.
In the early tests the engine was never allowed to develop more than 40
horse-power, as it was feared that by letting it develop more, which it was
clearly seen to be capable of, it might be injured and cause a delay in the
tests of the aerodrome. In the second series of tests it was allowed to
develop 51 horse-power at 935 R. P. M., but it was not thought to be
advisable to let it run at maximum power for more than an hour, for the
to the circulating pump F, supported in a discarded lower pyramid of the
aerodrome frame, the pump being driven by the small vertical shaft, as
already described. The water, after passing through the pump and the engine
cylinders, is led back to the upper part of the tank. By suitable connections
to the water mains and sewer, the water in the tank is kept at any desired
temperature. The gasoline supply tank is seen on the left-hand side of the
testing frame, as viewed in Plate 82, the carburetor being placed below it
and the gas supply pipe from the carburetor passing through the gasoline
tank. Instead of jacketing the carburetor, a grid formed of thin copper tubes
is supported just above the multitude of small air pipes leading into the
carburetor, and some of [p249] the hot water from the engine is by-passed
through this grid and thus warms the air as it passes into the carburetor. The
small pipe that by-passes this water through the grid is seen connected to
the outlet water pipe just above the cylinders, a small butterfly valve in the
outlet pipe enabling the amount of heated water passing through the grid to
be controlled. The return from the grid is by means of the small pipe
leading to the top of the large water tank. The tachometer, which gives
instantaneous readings of the speed of the engine, is seen at G, where it is at
all times in full view of the operator.
These dynamometers proved to be excellently suited for the testing work,
and far ahead of anything else the writer has ever found for engine testing.
Since the power required to rotate the rotor plates, with a uniform amount
of water in the drums, varies as the cube of the speed, it is readily seen that
it is impossible for the engine to race or injure itself by running away, as
frequently happens where there is no engine governor and Prony brakes are
used to measure the power.
In the early tests the engine was never allowed to develop more than 40
horse-power, as it was feared that by letting it develop more, which it was
clearly seen to be capable of, it might be injured and cause a delay in the
tests of the aerodrome. In the second series of tests it was allowed to
develop 51 horse-power at 935 R. P. M., but it was not thought to be
advisable to let it run at maximum power for more than an hour, for the
Page 447
same reason as before. In the summer of 1904, after it was seen that there
was no immediate possibility of securing funds for continuing the tests of
the aerodrome, it was planned to enter the engine in the competitive tests at
the St. Louis Exposition, where a prize of $2500 was offered for the lightest
engine for its power. As the conditions specified in this competition
required that the engine run at its maximum power for one hour, and that
this be followed by a durability test of ten hours’ continuous running, it was
decided to make some durability tests of the engine before taking it to St.
Louis. In these tests, the engine was run on three separate trials for a period
of ten hours45 with a constant load of 52.4 horse-power at 950 R. P. M.
Even in these long durability tests the engine and the dynamometers both
worked so smoothly and evenly that the engine did not vary its speed more
than ten revolutions per minute, and the pull on the spring scales varied less
than ten pounds in the entire ten hours. Considerable correspondence was
had with the officials of the St. Louis Exposition regarding the entrance of
the engine in the competition, in order to make sure that suitable facilities
for conducting the tests had been provided. After receiving assurance that
everything necessary had been provided, the engine and its testing
dynamometers were boxed for shipment to St. Louis and arrangements were
just being completed for their transportation when the following telegram
was [p250] received from the director in charge of the aeronautical
department of the Exposition: “On account of lack of competition engine
tests abandoned.” As the main object of entering the engine in the
competition was to insure for it an unquestioned record of its performance it
was decided to reassemble it in the testing frame in Washington and invite
some engineers of prominence to witness and certify to its performance, but
on account of the lack of funds for meeting the expenses incident to such a
series of tests as it was planned to make this was never done.
In the tests which were witnessed on April 26, 1902, by Captain I. N.
Lewis, Recorder of the Board of Ordnance and Fortification, the engine was
held down to a pull of 200 pounds on a 13-inch lever, when running at 1000
revolutions per minute. In the later tests in May, 1903, which were
witnessed by Captain Gibson, who was then Recorder of the Board of
was no immediate possibility of securing funds for continuing the tests of
the aerodrome, it was planned to enter the engine in the competitive tests at
the St. Louis Exposition, where a prize of $2500 was offered for the lightest
engine for its power. As the conditions specified in this competition
required that the engine run at its maximum power for one hour, and that
this be followed by a durability test of ten hours’ continuous running, it was
decided to make some durability tests of the engine before taking it to St.
Louis. In these tests, the engine was run on three separate trials for a period
of ten hours45 with a constant load of 52.4 horse-power at 950 R. P. M.
Even in these long durability tests the engine and the dynamometers both
worked so smoothly and evenly that the engine did not vary its speed more
than ten revolutions per minute, and the pull on the spring scales varied less
than ten pounds in the entire ten hours. Considerable correspondence was
had with the officials of the St. Louis Exposition regarding the entrance of
the engine in the competition, in order to make sure that suitable facilities
for conducting the tests had been provided. After receiving assurance that
everything necessary had been provided, the engine and its testing
dynamometers were boxed for shipment to St. Louis and arrangements were
just being completed for their transportation when the following telegram
was [p250] received from the director in charge of the aeronautical
department of the Exposition: “On account of lack of competition engine
tests abandoned.” As the main object of entering the engine in the
competition was to insure for it an unquestioned record of its performance it
was decided to reassemble it in the testing frame in Washington and invite
some engineers of prominence to witness and certify to its performance, but
on account of the lack of funds for meeting the expenses incident to such a
series of tests as it was planned to make this was never done.
In the tests which were witnessed on April 26, 1902, by Captain I. N.
Lewis, Recorder of the Board of Ordnance and Fortification, the engine was
held down to a pull of 200 pounds on a 13-inch lever, when running at 1000
revolutions per minute. In the later tests in May, 1903, which were
witnessed by Captain Gibson, who was then Recorder of the Board of
Page 448
Ordnance and Fortification, and Mr. G. H. Powell, the Secretary of the
Board, the engine was allowed to work at a pull of 265 pounds on the 13-
inch lever arm at a speed of 950 revolutions per minute. In the tests made in
August, 1904, the engine was run for ten consecutive hours46 at a pull
which varied from 263 to 271 pounds, or an average of 267 pounds, on a
13-inch lever, with the speed varying from 945 to 955 revolutions per
minute, thus showing 52.4 horse-power at the average speed of 950 R. P. M.
DETAILED WEIGHT OF NEW LARGE ENGINE.
Name of part. Weight in grammes.
Crank shaft 5,225
Connecting rods (total) 5,005
Pistons—
No. 1 1,652
No. 2 1,647
No. 3 1,655
No. 4 1,660
No. 5 1,646
Cylinders—
No. 1 (including exhaust and inlet valves, oil cups, etc.) 4,768
No. 2 (including exhaust and inlet valves, oil cups, etc.) 4,685
No. 3 (including exhaust and inlet valves, oil cups, etc.) 4,638
No. 4 (including exhaust and inlet valves, oil cups, etc.) 4,637
No. 5 (including exhaust and inlet valves, oil cups, etc.) 4,796
Port crank chamber drum, including cam, cam gears, punch rods, etc. 5,225
Starboard crank chamber drum 3,440
Spark plugs (5) 450
Outlet water pipe 450
Inlet water pipe 360
Inlet gas manifold 1,700
Primary and secondary sparkers and wires 512
Balance arm with braces for same—starboard 1,040
Balance arm with braces for same—port 1,067
Total 56,323 gm.=124.17 lbs.
Starboard fly wheel 3,946
Port fly wheel 3,234
Total weight of engine and fly wheels 63,503 gm.=140.00 lbs.
Spark coil and batteries 6,800
Carburetor 3,751
Inlet gas pipe from carburetor to manifold 756
Gasoline tank 1,004
Water tank 717
Water circulating pump and shaft 807
Radiator 7,700
Total weight of power plant 85,038 gm.=187.47 lbs.
Board, the engine was allowed to work at a pull of 265 pounds on the 13-
inch lever arm at a speed of 950 revolutions per minute. In the tests made in
August, 1904, the engine was run for ten consecutive hours46 at a pull
which varied from 263 to 271 pounds, or an average of 267 pounds, on a
13-inch lever, with the speed varying from 945 to 955 revolutions per
minute, thus showing 52.4 horse-power at the average speed of 950 R. P. M.
DETAILED WEIGHT OF NEW LARGE ENGINE.
Name of part. Weight in grammes.
Crank shaft 5,225
Connecting rods (total) 5,005
Pistons—
No. 1 1,652
No. 2 1,647
No. 3 1,655
No. 4 1,660
No. 5 1,646
Cylinders—
No. 1 (including exhaust and inlet valves, oil cups, etc.) 4,768
No. 2 (including exhaust and inlet valves, oil cups, etc.) 4,685
No. 3 (including exhaust and inlet valves, oil cups, etc.) 4,638
No. 4 (including exhaust and inlet valves, oil cups, etc.) 4,637
No. 5 (including exhaust and inlet valves, oil cups, etc.) 4,796
Port crank chamber drum, including cam, cam gears, punch rods, etc. 5,225
Starboard crank chamber drum 3,440
Spark plugs (5) 450
Outlet water pipe 450
Inlet water pipe 360
Inlet gas manifold 1,700
Primary and secondary sparkers and wires 512
Balance arm with braces for same—starboard 1,040
Balance arm with braces for same—port 1,067
Total 56,323 gm.=124.17 lbs.
Starboard fly wheel 3,946
Port fly wheel 3,234
Total weight of engine and fly wheels 63,503 gm.=140.00 lbs.
Spark coil and batteries 6,800
Carburetor 3,751
Inlet gas pipe from carburetor to manifold 756
Gasoline tank 1,004
Water tank 717
Water circulating pump and shaft 807
Radiator 7,700
Total weight of power plant 85,038 gm.=187.47 lbs.
Page 449
[p251] ◊
CHAPTER XI
SHOP TESTS OF THE AERODROME
In June, 1902, after the proper adjustments of the carburetor and other
accessories of the engine had been accurately determined in the tests on the
testing frame, the engine was assembled in its proper position in the
aerodrome frame and connected to the propellers. The aerodrome frame
was then mounted directly on the floor of the launching car, which was
placed on a short track laid on the floor of the shop, as previously
described. A large spring balance, which had been previously calibrated,
was then connected between the car and an upright fastened to the track,
and tests were made to determine the thrust developed when the engine
drove the propellers at different speeds. Upon finding that there was
comparatively little vibration when the engine was driving the propellers
even at its maximum speed, it was felt safe to raise the aerodrome from the
floor of the car and place it upon the uprights on which it would be
supported in launching it. Quite an extended series of tests was then made,
and although the uprights raised the aerodrome frame until the midrod was
practically 9 feet from the floor of the car, and in the tests at maximum
power the propellers developed an average thrust of 450 pounds, yet it was
found that the clutch hook held the bearing points of the frame so securely
on the uprights of the car that all fear that the aerodrome might break loose
from the car during the launching process was removed.
Upon the completion of these tests, which had proved most satisfactory,
the aerodrome frame was supported from the ceiling of the shop by means
of four short coil springs which reproduced as nearly as possible the elastic
or flexible suspension which the aerodrome would have when supported by
its wings in the air. These springs were attached at the same points on the
main frame of the aerodrome at which the wings would be attached, thus
permitting a careful study of the amount of flexure and vibration which it
would undergo in actual flight. The most remarkable difference in the
CHAPTER XI
SHOP TESTS OF THE AERODROME
In June, 1902, after the proper adjustments of the carburetor and other
accessories of the engine had been accurately determined in the tests on the
testing frame, the engine was assembled in its proper position in the
aerodrome frame and connected to the propellers. The aerodrome frame
was then mounted directly on the floor of the launching car, which was
placed on a short track laid on the floor of the shop, as previously
described. A large spring balance, which had been previously calibrated,
was then connected between the car and an upright fastened to the track,
and tests were made to determine the thrust developed when the engine
drove the propellers at different speeds. Upon finding that there was
comparatively little vibration when the engine was driving the propellers
even at its maximum speed, it was felt safe to raise the aerodrome from the
floor of the car and place it upon the uprights on which it would be
supported in launching it. Quite an extended series of tests was then made,
and although the uprights raised the aerodrome frame until the midrod was
practically 9 feet from the floor of the car, and in the tests at maximum
power the propellers developed an average thrust of 450 pounds, yet it was
found that the clutch hook held the bearing points of the frame so securely
on the uprights of the car that all fear that the aerodrome might break loose
from the car during the launching process was removed.
Upon the completion of these tests, which had proved most satisfactory,
the aerodrome frame was supported from the ceiling of the shop by means
of four short coil springs which reproduced as nearly as possible the elastic
or flexible suspension which the aerodrome would have when supported by
its wings in the air. These springs were attached at the same points on the
main frame of the aerodrome at which the wings would be attached, thus
permitting a careful study of the amount of flexure and vibration which it
would undergo in actual flight. The most remarkable difference in the
Page 450
nature of the vibration induced in the frame was found when the aerodrome
was thus supported by springs. When it was supported on the rather
unyielding launching car, the general tremor set up in the frame by the
engine and propellers was, while small, yet harsh, the effect on a person
standing in the aviator’s car being rather unpleasant in the joints of the
knees when experienced for several minutes. When the frame was
suspended by the springs it was found that all this harshness of tremor
disappeared, it being replaced by a slight general and rapid tremor of the
whole frame, which was not at all unpleasant, and which [p252] had no tiring
effect on one standing in the aviator’s car. In fact, the vibration in the first
case resembled rather closely that of a motor vehicle supported on wheels
having metal tires, and in the second case a motor vehicle supported on
wheels having pneumatic tires.
As in these tests in the shop it was impossible to keep the engine cool by
circulating its cooling water through the radiator, since there was no air
current blowing across the latter to carry away the heat, it was necessary to
connect an extra water tank in the cooling-water circuit. A tank holding
about ten gallons was used, and this sufficed for about ten minutes before
the water was raised to the boiling point.
During one of these tests when the frame was supported from the springs,
and while the engine was developing about fifty horse-power, without any
warning whatever, both propellers suddenly twisted off from the flanges by
which they were connected to the propeller shafts, thus leaving the engine
entirely unloaded. The propellers both dropped quietly to the floor, making
only about one or two turns in falling the distance of approximately 10 feet,
and the engine, which had been running at about 850 R. P. M., immediately
speeded up to an exceedingly high speed, which, while not exactly known,
since the tachometer only read to 2000 R. P. M., yet from the deflection
produced on the tachometer needle must have been considerably higher
than this. Although the fly wheels, which were 33 inches in diameter, with
the aluminum rims and wire spokes, had been exceedingly well made, yet it
was not considered safe to run them at this speed, and the engine was
immediately shut down. At the moment, however, that the engine had
was thus supported by springs. When it was supported on the rather
unyielding launching car, the general tremor set up in the frame by the
engine and propellers was, while small, yet harsh, the effect on a person
standing in the aviator’s car being rather unpleasant in the joints of the
knees when experienced for several minutes. When the frame was
suspended by the springs it was found that all this harshness of tremor
disappeared, it being replaced by a slight general and rapid tremor of the
whole frame, which was not at all unpleasant, and which [p252] had no tiring
effect on one standing in the aviator’s car. In fact, the vibration in the first
case resembled rather closely that of a motor vehicle supported on wheels
having metal tires, and in the second case a motor vehicle supported on
wheels having pneumatic tires.
As in these tests in the shop it was impossible to keep the engine cool by
circulating its cooling water through the radiator, since there was no air
current blowing across the latter to carry away the heat, it was necessary to
connect an extra water tank in the cooling-water circuit. A tank holding
about ten gallons was used, and this sufficed for about ten minutes before
the water was raised to the boiling point.
During one of these tests when the frame was supported from the springs,
and while the engine was developing about fifty horse-power, without any
warning whatever, both propellers suddenly twisted off from the flanges by
which they were connected to the propeller shafts, thus leaving the engine
entirely unloaded. The propellers both dropped quietly to the floor, making
only about one or two turns in falling the distance of approximately 10 feet,
and the engine, which had been running at about 850 R. P. M., immediately
speeded up to an exceedingly high speed, which, while not exactly known,
since the tachometer only read to 2000 R. P. M., yet from the deflection
produced on the tachometer needle must have been considerably higher
than this. Although the fly wheels, which were 33 inches in diameter, with
the aluminum rims and wire spokes, had been exceedingly well made, yet it
was not considered safe to run them at this speed, and the engine was
immediately shut down. At the moment, however, that the engine had
Page 451
broken loose from its propellers and also momentarily jumped to this
exceedingly high speed there was absolutely no vibration that could be
noticed, the unloaded engine running as smoothly as an electric motor. This
showed very clearly that the running balance of the engine was as near
perfect as it would be possible to get it, except with a seven-cylinder
engine, which is theoretically capable of more perfect balance. It was
evident that what small vibration there was in the frame while the engine
was developing its power was due almost entirely to the reverse torque,
and, of course, could never be entirely eliminated.
In the tests of the engine working in the frame, both while mounted on
the car and also when suspended from the springs, a great amount of delay
was caused from the fact that the ball-bearings on the transmission and
propeller shafts frequently went to pieces. There were two reasons for this:
In the first place, although carefully selected balls were used, defective ones
were continually encountered. Even a slight defect in a single ball resulted
in its breaking under the rather severe test to which they were subjected,
and, as is well known, the breaking of one ball in a ball-bearing usually
results in the destruction of the whole bearing, especially if the races are
light. The second cause was that [p253] the whole aerodrome had been
originally designed with the expectation of using a maximum of 24 horse-
power, and as no margin had been left to provide for possible increases in
the size of the bearings, there was no room to permit them to be increased
without almost completely reconstructing portions of the transverse frame.
While in the end it would have been cheaper to have reconstructed these
portions in order to put in larger bearings, yet, as is always the case in
experimental work of this kind, small changes which seem to hold out hope
of overcoming difficulties are usually followed, rather than reconstructions
which can be seen to involve considerable expense and delay. After a
number of minor changes had been made in the bearings, they were finally
able to stand up fairly well under the severe strain to which they were
subjected when the engine developed its full power, and no further changes
were made in them; a defective race being, however, replaced by a new one
as occasion demanded.
exceedingly high speed there was absolutely no vibration that could be
noticed, the unloaded engine running as smoothly as an electric motor. This
showed very clearly that the running balance of the engine was as near
perfect as it would be possible to get it, except with a seven-cylinder
engine, which is theoretically capable of more perfect balance. It was
evident that what small vibration there was in the frame while the engine
was developing its power was due almost entirely to the reverse torque,
and, of course, could never be entirely eliminated.
In the tests of the engine working in the frame, both while mounted on
the car and also when suspended from the springs, a great amount of delay
was caused from the fact that the ball-bearings on the transmission and
propeller shafts frequently went to pieces. There were two reasons for this:
In the first place, although carefully selected balls were used, defective ones
were continually encountered. Even a slight defect in a single ball resulted
in its breaking under the rather severe test to which they were subjected,
and, as is well known, the breaking of one ball in a ball-bearing usually
results in the destruction of the whole bearing, especially if the races are
light. The second cause was that [p253] the whole aerodrome had been
originally designed with the expectation of using a maximum of 24 horse-
power, and as no margin had been left to provide for possible increases in
the size of the bearings, there was no room to permit them to be increased
without almost completely reconstructing portions of the transverse frame.
While in the end it would have been cheaper to have reconstructed these
portions in order to put in larger bearings, yet, as is always the case in
experimental work of this kind, small changes which seem to hold out hope
of overcoming difficulties are usually followed, rather than reconstructions
which can be seen to involve considerable expense and delay. After a
number of minor changes had been made in the bearings, they were finally
able to stand up fairly well under the severe strain to which they were
subjected when the engine developed its full power, and no further changes
were made in them; a defective race being, however, replaced by a new one
as occasion demanded.
Page 452
These tests demonstrated very clearly that at speeds of approximately
1000 revolutions per minute ball-bearings which are subjected to
considerable loads should be calculated with a considerable margin of
safety, as the yielding of the frame, which must necessarily be far from
rigid, causes more or less error in the alignment of the shafts and bearings,
and this introduces considerably increased strains on the bearings. In the
early tests before the bearings were strengthened, the balls in some of the
races were on a few occasions ground to a very fine powder before it was
discovered that they had failed. Such a result, it will be understood, could
and did occur in the course of a very minute length of time.
In imitating as nearly as possible the conditions to which the carburetor
of the engine would be subjected during the period of launching, numerous
tests were made in which the engine was brought to its maximum speed
and, without changing the adjustment of the mixture-controlling devices of
the carburetor, sudden blasts of air were turned on it from various
directions, and these were continued until the mixture-control devices were
perfected to such a point that gusts of thirty miles an hour suddenly directed
from any point against any portion of the apparatus would in no way effect
the speed and power of the engine. These tests were considered necessary in
view of the very sudden changes in conditions to which the aerodrome
would be subjected during its brief run down the launching track, the
conditions changing in approximately three seconds from absolute
quiescence of the aerodrome to a plunge through space at thirty-five feet
per second. An aviator would be more than occupied with maintaining
control of himself and of the aerodrome, which at the moment of leaving
the track might require considerable change in the adjustment of the Pénaud
tail, and he would, therefore, not be able to make any adjustments of the
engine-control devices. This supposition was entirely confirmed in the
actual tests of the aerodrome which are to be later described, the rush down
the track being [p254] so very brief that the engine could not have been given
any attention by the aviator had it needed it, which fortunately it did not.
It is hardly necessary to recount at any length the great difficulties which
was experienced in these tests of the engine in the aerodrome frame before
1000 revolutions per minute ball-bearings which are subjected to
considerable loads should be calculated with a considerable margin of
safety, as the yielding of the frame, which must necessarily be far from
rigid, causes more or less error in the alignment of the shafts and bearings,
and this introduces considerably increased strains on the bearings. In the
early tests before the bearings were strengthened, the balls in some of the
races were on a few occasions ground to a very fine powder before it was
discovered that they had failed. Such a result, it will be understood, could
and did occur in the course of a very minute length of time.
In imitating as nearly as possible the conditions to which the carburetor
of the engine would be subjected during the period of launching, numerous
tests were made in which the engine was brought to its maximum speed
and, without changing the adjustment of the mixture-controlling devices of
the carburetor, sudden blasts of air were turned on it from various
directions, and these were continued until the mixture-control devices were
perfected to such a point that gusts of thirty miles an hour suddenly directed
from any point against any portion of the apparatus would in no way effect
the speed and power of the engine. These tests were considered necessary in
view of the very sudden changes in conditions to which the aerodrome
would be subjected during its brief run down the launching track, the
conditions changing in approximately three seconds from absolute
quiescence of the aerodrome to a plunge through space at thirty-five feet
per second. An aviator would be more than occupied with maintaining
control of himself and of the aerodrome, which at the moment of leaving
the track might require considerable change in the adjustment of the Pénaud
tail, and he would, therefore, not be able to make any adjustments of the
engine-control devices. This supposition was entirely confirmed in the
actual tests of the aerodrome which are to be later described, the rush down
the track being [p254] so very brief that the engine could not have been given
any attention by the aviator had it needed it, which fortunately it did not.
It is hardly necessary to recount at any length the great difficulties which
was experienced in these tests of the engine in the aerodrome frame before
Page 453
the shafts, bearings, propellers, and, in fact, the frame itself were all
properly co-ordinated so that confidence could be felt that all of the parts
would stand the strains which were likely to come on them when the
aerodrome was in flight. These tests were really not tests of the engine
itself, but of the frame, shafts, and bearings. Suffice it to say that nearly a
year was consumed by the various breakages of the shafts, bearings, and
propellers before it was felt that all of these parts could be depended on, and
even then the weakness of the bearings above referred to was fully
recognized. Had some of the better-grade balls and steels for the bearings,
which have since that time come on the market, been obtainable then, there
would have been no difficulty with these bearings. However, this same
remark might be made with reference to nearly all of the details of the
aerodrome, for it was the accessories, such as bearings for the transmission
and propeller shafts, spark plugs, coils, batteries, and a suitable carburetor
for the engine, that caused the chief delay after the main difficulty of getting
a suitable engine had been overcome.
properly co-ordinated so that confidence could be felt that all of the parts
would stand the strains which were likely to come on them when the
aerodrome was in flight. These tests were really not tests of the engine
itself, but of the frame, shafts, and bearings. Suffice it to say that nearly a
year was consumed by the various breakages of the shafts, bearings, and
propellers before it was felt that all of these parts could be depended on, and
even then the weakness of the bearings above referred to was fully
recognized. Had some of the better-grade balls and steels for the bearings,
which have since that time come on the market, been obtainable then, there
would have been no difficulty with these bearings. However, this same
remark might be made with reference to nearly all of the details of the
aerodrome, for it was the accessories, such as bearings for the transmission
and propeller shafts, spark plugs, coils, batteries, and a suitable carburetor
for the engine, that caused the chief delay after the main difficulty of getting
a suitable engine had been overcome.
Page 454
[p255] ◊
CHAPTER XII
FIELD-TRIALS IN 1903
The extended series of shop tests which had occupied a considerable
portion of the late winter and early spring of 1903 had demonstrated the
following facts: First, with the aerodrome mounted on the launching car, a
propeller thrust of from 450 to 475 pounds could be maintained indefinitely
by the engine, and even when the engine was delivering its full power to the
propellers, the vibration was so small as to cause no apprehension that the
wings and rudder would be made to vibrate sufficiently to produce undue
strains in them. Second, with the aerodrome suspended from the ceiling by
springs at the points at which the wings would be attached, the vibration
produced by the engine developing it’s full power was even less than when
the machine was mounted on the launching car and there was, consequently,
even less cause for concern that the wings and rudder might be set in
vibration when the machine was free in the air. Third, the engine could be
depended upon to deliver something over 52 horse-power when the five
cylinders were working properly, and even with one cylinder not working,
but acting as a dead load against the others, approximately 35 horse-power
could be developed, while with two cylinders not working at all, the three
which were working would deliver about 25 horse-power. Therefore, even
assuming that two of the five cylinders might become deranged during a
flight, there should still be sufficient power to propel the machine. These
tests, some of which had been witnessed by members of the Board of
Ordnance and Fortification, clearly demonstrated that the time had arrived
when it was safe to give the aerodrome a test in free flight. The machine
itself together with all its appurtenances and much extra material for repairs
in case of breakages, which previous experience had shown to be almost
certain, was accordingly taken from the shop and placed on the house-boat
preparatory to taking it down the river to the point opposite Widewater, Va.,
which had already been selected as the “experimental ground.”
CHAPTER XII
FIELD-TRIALS IN 1903
The extended series of shop tests which had occupied a considerable
portion of the late winter and early spring of 1903 had demonstrated the
following facts: First, with the aerodrome mounted on the launching car, a
propeller thrust of from 450 to 475 pounds could be maintained indefinitely
by the engine, and even when the engine was delivering its full power to the
propellers, the vibration was so small as to cause no apprehension that the
wings and rudder would be made to vibrate sufficiently to produce undue
strains in them. Second, with the aerodrome suspended from the ceiling by
springs at the points at which the wings would be attached, the vibration
produced by the engine developing it’s full power was even less than when
the machine was mounted on the launching car and there was, consequently,
even less cause for concern that the wings and rudder might be set in
vibration when the machine was free in the air. Third, the engine could be
depended upon to deliver something over 52 horse-power when the five
cylinders were working properly, and even with one cylinder not working,
but acting as a dead load against the others, approximately 35 horse-power
could be developed, while with two cylinders not working at all, the three
which were working would deliver about 25 horse-power. Therefore, even
assuming that two of the five cylinders might become deranged during a
flight, there should still be sufficient power to propel the machine. These
tests, some of which had been witnessed by members of the Board of
Ordnance and Fortification, clearly demonstrated that the time had arrived
when it was safe to give the aerodrome a test in free flight. The machine
itself together with all its appurtenances and much extra material for repairs
in case of breakages, which previous experience had shown to be almost
certain, was accordingly taken from the shop and placed on the house-boat
preparatory to taking it down the river to the point opposite Widewater, Va.,
which had already been selected as the “experimental ground.”
Page 455
Owing to the limited size of the shops it had been impossible to place the
wings and rudder in their proper positions on the aerodrome and determine
its balancing in a way similar to that practiced with the models. The
approximate settings for the wings and rudder had, however, been
determined by calculation from the data obtained in the test of the quarter-
size model, so that it remained only to place the wings and a weight to
represent the rudder actually on the machine in the large space of the house-
boat (which, however, was not large enough to permit the rudder to be
assembled along with the wings), and thus check the balancing previously
determined by calculation. There were very [p256] few appurtenances which
could be shifted in balancing the aerodrome, but the proper disposition of
weight had been so accurately determined by calculation that the floats,
which, as will be seen from the various photographs, were merely
cylindrical tanks with pointed ends, and of a sufficient capacity to cause a
displacement great enough to float the aerodrome when it came down into
the water, proved sufficient ballast for shifting the center of gravity to its
proper point. The flying weight of the aerodrome was 830 pounds,47
including the weight of the writer, which was 125 pounds. The total area of
the wings or supporting surfaces was 1040 square feet, or the ratio of
supporting surface to weight was 1.25 square feet per pound, which is the
same as .8 pound per square foot.
After the balancing of the large aerodrome had been completed on the
house-boat, and everything else got in readiness as far as could be done
before actually arriving at the point at which the test was to be made, the
house-boat was towed down the river on July 14, 1903, and fastened to its
mooring buoy, which had been placed in the middle of the river at a point
practically opposite Widewater, Va., and approximately forty miles from
Washington. See Coast-Survey Chart, Plate 85.
Sleeping quarters for the force of eight workmen and the regular soldier
from the United States Army, who had been detailed as a special guard, had
been provided on the boat, but owing to the lack of space it had been found
impracticable to arrange proper cooking facilities on the boat, and it had
been found necessary to arrange to transport the workmen to Chopawamsic
wings and rudder in their proper positions on the aerodrome and determine
its balancing in a way similar to that practiced with the models. The
approximate settings for the wings and rudder had, however, been
determined by calculation from the data obtained in the test of the quarter-
size model, so that it remained only to place the wings and a weight to
represent the rudder actually on the machine in the large space of the house-
boat (which, however, was not large enough to permit the rudder to be
assembled along with the wings), and thus check the balancing previously
determined by calculation. There were very [p256] few appurtenances which
could be shifted in balancing the aerodrome, but the proper disposition of
weight had been so accurately determined by calculation that the floats,
which, as will be seen from the various photographs, were merely
cylindrical tanks with pointed ends, and of a sufficient capacity to cause a
displacement great enough to float the aerodrome when it came down into
the water, proved sufficient ballast for shifting the center of gravity to its
proper point. The flying weight of the aerodrome was 830 pounds,47
including the weight of the writer, which was 125 pounds. The total area of
the wings or supporting surfaces was 1040 square feet, or the ratio of
supporting surface to weight was 1.25 square feet per pound, which is the
same as .8 pound per square foot.
After the balancing of the large aerodrome had been completed on the
house-boat, and everything else got in readiness as far as could be done
before actually arriving at the point at which the test was to be made, the
house-boat was towed down the river on July 14, 1903, and fastened to its
mooring buoy, which had been placed in the middle of the river at a point
practically opposite Widewater, Va., and approximately forty miles from
Washington. See Coast-Survey Chart, Plate 85.
Sleeping quarters for the force of eight workmen and the regular soldier
from the United States Army, who had been detailed as a special guard, had
been provided on the boat, but owing to the lack of space it had been found
impracticable to arrange proper cooking facilities on the boat, and it had
been found necessary to arrange to transport the workmen to Chopawamsic
Page 456
Island, near Quantico, Va., for their meals. It had been planned to use the
twenty-five-foot power launch for this purpose, but owing to the heavy
storms which became quite frequent soon after the house-boat was taken
down the river, it was found that the small launch was not sufficient, and it
was necessary to employ a tug-boat and keep it stationed there at all times.
This added very considerably to the expense of the experiments, as the hire
of this one tug-boat very nearly equalled the pay-roll of the workmen, and
while it was not expected that the stay down the river would be so greatly
prolonged as afterwards proved the case it was felt certain that minor delays
were sure to occur and the experiments would at the very least require
several weeks.
twenty-five-foot power launch for this purpose, but owing to the heavy
storms which became quite frequent soon after the house-boat was taken
down the river, it was found that the small launch was not sufficient, and it
was necessary to employ a tug-boat and keep it stationed there at all times.
This added very considerably to the expense of the experiments, as the hire
of this one tug-boat very nearly equalled the pay-roll of the workmen, and
while it was not expected that the stay down the river would be so greatly
prolonged as afterwards proved the case it was felt certain that minor delays
were sure to occur and the experiments would at the very least require
several weeks.
Page 457
FROM SHEET NO. 3, U. S. COAST AND GEODETIC SURVEY CHART OF POTOMAC
RIVER, ISSUE OF 1882 SCALE 1 1-16 INCH TO STATUTE MILE
RIVER, ISSUE OF 1882 SCALE 1 1-16 INCH TO STATUTE MILE
Page 458
PL. 85. LOCATION OF HOUSE BOAT IN CENTER OF POTOMAC
RIVER, JULY 14, 1903 ◊ lgr
Had it been possible to foresee the great delay which finally occurred
before the large aerodrome was actually launched, and the great expense
arising from the necessity of maintaining one or more expensive tug-boats
constantly, it is very certain that an experimental station nearer Washington
would have been selected, even though the nearer places on the river which
were available were much less suitable, both on account of the river being
much narrower and the traffic very much heavier. In fact, at the time that
the house-boat was taken down the river on July 14, with the expectation
that the experiments with the [p257] large aerodrome would certainly be
concluded within four weeks, the expenses of the work, which had been
met from the Hodgkins Fund of the Smithsonian Institution since the
original allotment from the Board of Ordnance and Fortification was
exhausted more than a year previously, had already made such heavy drafts
on this fund that Mr. Langley was most reluctant to draw further on it, even
to the extent which seemed necessary to meet the expenses of a month of
“field-work.”
Before making the tests of the large aerodrome, it was intended to give
the quarter-size model a preliminary trial to test the balancing which it was
proposed to use on the large machine. For this test it was planned to employ
the small launching apparatus mounted on top of the small house-boat,
which had been used in the experiments with the steam-driven models Nos.
5 and 6 in 1899, and later with the quarter-size model in 1901. However,
after arriving down the river, it was found that the small house-boat which
had been anchored at Chopawamsic Island since the experiments in 1901
had deteriorated to such an extent that it was unsafe to take it out into the
river. The launching apparatus for the model was, therefore, removed from
it and placed on the turn-table of the large house-boat, alongside the
launching track for the large machine. After completing this transfer of the
model-launching apparatus everything was thought to be in readiness for a
test of the quarter-size model, but upon making a shop test of the model to
make sure that its engine was working properly, it was found impossible to
RIVER, JULY 14, 1903 ◊ lgr
Had it been possible to foresee the great delay which finally occurred
before the large aerodrome was actually launched, and the great expense
arising from the necessity of maintaining one or more expensive tug-boats
constantly, it is very certain that an experimental station nearer Washington
would have been selected, even though the nearer places on the river which
were available were much less suitable, both on account of the river being
much narrower and the traffic very much heavier. In fact, at the time that
the house-boat was taken down the river on July 14, with the expectation
that the experiments with the [p257] large aerodrome would certainly be
concluded within four weeks, the expenses of the work, which had been
met from the Hodgkins Fund of the Smithsonian Institution since the
original allotment from the Board of Ordnance and Fortification was
exhausted more than a year previously, had already made such heavy drafts
on this fund that Mr. Langley was most reluctant to draw further on it, even
to the extent which seemed necessary to meet the expenses of a month of
“field-work.”
Before making the tests of the large aerodrome, it was intended to give
the quarter-size model a preliminary trial to test the balancing which it was
proposed to use on the large machine. For this test it was planned to employ
the small launching apparatus mounted on top of the small house-boat,
which had been used in the experiments with the steam-driven models Nos.
5 and 6 in 1899, and later with the quarter-size model in 1901. However,
after arriving down the river, it was found that the small house-boat which
had been anchored at Chopawamsic Island since the experiments in 1901
had deteriorated to such an extent that it was unsafe to take it out into the
river. The launching apparatus for the model was, therefore, removed from
it and placed on the turn-table of the large house-boat, alongside the
launching track for the large machine. After completing this transfer of the
model-launching apparatus everything was thought to be in readiness for a
test of the quarter-size model, but upon making a shop test of the model to
make sure that its engine was working properly, it was found impossible to
Page 459
get it to work at all. A few explosions could be obtained once in a while, but
very irregularly. After spending considerable time in trying to locate the
difficulty, it was found that the commutator which distributes the high-
tension sparking current to the proper cylinder at the proper time was short-
circuited. This commutator had been made of “insulating fibre” and had
never caused any previous trouble. It was now found, however, that the very
damp atmosphere which had been experienced during the preceding two
weeks, when the fog for a large portion of the time was so heavy that
objects at a short distance across the water could not be seen, had caused
the moisture to penetrate the fibre and thus destroy its insulating qualities.
After much trouble some vulcanite and mica were secured and a new
commutator made to replace the fibre one, and, then, after some minor
difficulties had been remedied, the engine for the model was got into good
condition again. After getting satisfactory shop tests on the model
aerodrome, and having everything in readiness for a flight, it was necessary
to wait many days before the weather was calm enough for a test. However,
on August 8 the weather quieted down and the model was launched at 9.30
a. m. into a wind blowing about 12 miles per hour from E. SE.
Referring to Plate 86, which shows the quarter-size model mounted on its
launching car on top of the large house-boat, and which was taken only a
few [p258] minutes before the model was actually launched, it will be noted
that a board (A ) projects from the front of the launching car. This board,
which is mounted in a false floor of the launching car, is so arranged that
when it strikes the two blocks (B ) at the end of the track it is driven
backward in the car against the triggers which prevent the uprights (D ),
supporting the aerodrome, from being folded down against the floor. When
this board strikes the triggers it releases them and the springs (C ), which in
this case were rubber bands, immediately fold the vertical posts or uprights
(D ) against the brace posts (E ), which are immediately folded down flat
against the floor of the car through the action of the spring hinges, by which
they are connected to it. These uprights (D ), which support the aerodrome
at the front and rear, respectively, are not released until a fraction of a
second after the release of the clutch hook (F ), which is attached to the
very irregularly. After spending considerable time in trying to locate the
difficulty, it was found that the commutator which distributes the high-
tension sparking current to the proper cylinder at the proper time was short-
circuited. This commutator had been made of “insulating fibre” and had
never caused any previous trouble. It was now found, however, that the very
damp atmosphere which had been experienced during the preceding two
weeks, when the fog for a large portion of the time was so heavy that
objects at a short distance across the water could not be seen, had caused
the moisture to penetrate the fibre and thus destroy its insulating qualities.
After much trouble some vulcanite and mica were secured and a new
commutator made to replace the fibre one, and, then, after some minor
difficulties had been remedied, the engine for the model was got into good
condition again. After getting satisfactory shop tests on the model
aerodrome, and having everything in readiness for a flight, it was necessary
to wait many days before the weather was calm enough for a test. However,
on August 8 the weather quieted down and the model was launched at 9.30
a. m. into a wind blowing about 12 miles per hour from E. SE.
Referring to Plate 86, which shows the quarter-size model mounted on its
launching car on top of the large house-boat, and which was taken only a
few [p258] minutes before the model was actually launched, it will be noted
that a board (A ) projects from the front of the launching car. This board,
which is mounted in a false floor of the launching car, is so arranged that
when it strikes the two blocks (B ) at the end of the track it is driven
backward in the car against the triggers which prevent the uprights (D ),
supporting the aerodrome, from being folded down against the floor. When
this board strikes the triggers it releases them and the springs (C ), which in
this case were rubber bands, immediately fold the vertical posts or uprights
(D ) against the brace posts (E ), which are immediately folded down flat
against the floor of the car through the action of the spring hinges, by which
they are connected to it. These uprights (D ), which support the aerodrome
at the front and rear, respectively, are not released until a fraction of a
second after the release of the clutch hook (F ), which is attached to the
Page 460
middle upright (G ), and which, grasping the lower pyramid, holds the
machine down firmly against the uprights (D ) previously referred to. In
order to prevent the possibility of the aerodrome being released prematurely
while the car is held at the extreme rear end of the track by the hook (H ), a
steel pin (J ), which can just be seen in the photograph, is pushed through a
hole in the board (A ), and into a hole in a cross-member on the bottom of
the car, thus holding the board in its proper position. After the engine is
started up one of the mechanics who has assisted in starting it is under
orders to remove the pin at the word “Ready,” and at the word “Go” the
other mechanic who has assisted in starting the engine is under orders to
release the hook (H ), and thus allow the car to dash down the track. In the
experiment on August 8 the mechanic failed to remove the pin (J ) at the
proper time, and it was only after the machine had been released and started
down the track that it was seen that the pin had not been removed. It was
then, however, too late to stop it, so the car dashed down the track.
Although the striking of the board against the blocks caused the pin to split
the board to pieces, the launching apparatus worked perfectly and the
aerodrome started off on a perfectly even keel, the propellers revolving at
an exceedingly high rate of speed. The aerodrome flew straight ahead for a
distance of 350 feet, when it began to circle towards the right, descending
slightly as it circled. Upon completing a quarter circle it again began to rise,
flying straight ahead until it had gone a similar distance, when it again lost
headway, but before it reached the water the engine increased its speed and
the aerodrome again rose. When the engine slowed down for the third time,
however, the aerodrome was not many feet above the river, so that before
the engine regained its normal speed the aerodrome touched the water with
its propellers still revolving, but very slowly. While the total distance
covered was only about 1000 feet, and the time that it was actually in the air
27 seconds, yet in this brief time it had served the main purpose for which it
had been built, which was to find out if the balancing of [p259] the large
aerodrome, which had been determined by calculation from the results
obtained with the steam-driven models, was correct. For it was assumed
that if the quarter-size model, which was an exact counterpart of the large
machine down firmly against the uprights (D ) previously referred to. In
order to prevent the possibility of the aerodrome being released prematurely
while the car is held at the extreme rear end of the track by the hook (H ), a
steel pin (J ), which can just be seen in the photograph, is pushed through a
hole in the board (A ), and into a hole in a cross-member on the bottom of
the car, thus holding the board in its proper position. After the engine is
started up one of the mechanics who has assisted in starting it is under
orders to remove the pin at the word “Ready,” and at the word “Go” the
other mechanic who has assisted in starting the engine is under orders to
release the hook (H ), and thus allow the car to dash down the track. In the
experiment on August 8 the mechanic failed to remove the pin (J ) at the
proper time, and it was only after the machine had been released and started
down the track that it was seen that the pin had not been removed. It was
then, however, too late to stop it, so the car dashed down the track.
Although the striking of the board against the blocks caused the pin to split
the board to pieces, the launching apparatus worked perfectly and the
aerodrome started off on a perfectly even keel, the propellers revolving at
an exceedingly high rate of speed. The aerodrome flew straight ahead for a
distance of 350 feet, when it began to circle towards the right, descending
slightly as it circled. Upon completing a quarter circle it again began to rise,
flying straight ahead until it had gone a similar distance, when it again lost
headway, but before it reached the water the engine increased its speed and
the aerodrome again rose. When the engine slowed down for the third time,
however, the aerodrome was not many feet above the river, so that before
the engine regained its normal speed the aerodrome touched the water with
its propellers still revolving, but very slowly. While the total distance
covered was only about 1000 feet, and the time that it was actually in the air
27 seconds, yet in this brief time it had served the main purpose for which it
had been built, which was to find out if the balancing of [p259] the large
aerodrome, which had been determined by calculation from the results
obtained with the steam-driven models, was correct. For it was assumed
that if the quarter-size model, which was an exact counterpart of the large
Page 461
machine, should fly successfully with the same balancing as that calculated
for the large one, the large one could reasonably be expected to act
similarly. It was at first thought best to make another test with the model
immediately after recovering it from the water, but by the time it could be
brought into the house-boat and the water which had got into the engine
cylinders could be removed and the engine made to work properly quite a
strong wind had sprung up and rendered further tests of the model on this
day impossible. If the launching track for the small machine could have
remained on the top of the boat without interfering with the completion of
the preparations for testing the large machine, it would have been left there
and other tests made with the model when the weather was suitable, but as
this could not be done without interfering with the work on the large
machine, and the delays with the model had already been so great, the small
track was immediately removed and the model stored away in the house-
boat for possible later tests.
At the first it was impossible to account for the engine on the model
running so irregularly and slowing down so soon after it was launched, as it
was felt very certain that the cylinders could not in so short a time, and with
the aerodrome actually moving through the air, have heated up sufficiently
to cause it. After a while, however, one of the workmen volunteered the
information that in his zeal to fill the fuel tank completely so as to insure a
long flight, he had caused the tank to overflow so that some of the gasoline
had run into the intake pipe, and that he had noticed gasoline dripping from
the intake pipe as the machine went down the track. This excess gasoline in
the intake pipe had caused the mixing valve which controls the quality of
the explosive mixture to be improperly set, so that it would not furnish the
proper mixture when the fuel was supplied in the proper way by the
carburetor, and consequently when this excess gasoline had evaporated, the
mixture furnished to the engine was not proper, and it consequently slowed
down, there being no human intelligence on board to correct the adjustment
of the mixing valve.
A series of seven photographs of this flight of the quarter-size model is
given in Plates 87 to 93. Plate 87, taken with a kodak from the tug-boat
for the large one, the large one could reasonably be expected to act
similarly. It was at first thought best to make another test with the model
immediately after recovering it from the water, but by the time it could be
brought into the house-boat and the water which had got into the engine
cylinders could be removed and the engine made to work properly quite a
strong wind had sprung up and rendered further tests of the model on this
day impossible. If the launching track for the small machine could have
remained on the top of the boat without interfering with the completion of
the preparations for testing the large machine, it would have been left there
and other tests made with the model when the weather was suitable, but as
this could not be done without interfering with the work on the large
machine, and the delays with the model had already been so great, the small
track was immediately removed and the model stored away in the house-
boat for possible later tests.
At the first it was impossible to account for the engine on the model
running so irregularly and slowing down so soon after it was launched, as it
was felt very certain that the cylinders could not in so short a time, and with
the aerodrome actually moving through the air, have heated up sufficiently
to cause it. After a while, however, one of the workmen volunteered the
information that in his zeal to fill the fuel tank completely so as to insure a
long flight, he had caused the tank to overflow so that some of the gasoline
had run into the intake pipe, and that he had noticed gasoline dripping from
the intake pipe as the machine went down the track. This excess gasoline in
the intake pipe had caused the mixing valve which controls the quality of
the explosive mixture to be improperly set, so that it would not furnish the
proper mixture when the fuel was supplied in the proper way by the
carburetor, and consequently when this excess gasoline had evaporated, the
mixture furnished to the engine was not proper, and it consequently slowed
down, there being no human intelligence on board to correct the adjustment
of the mixing valve.
A series of seven photographs of this flight of the quarter-size model is
given in Plates 87 to 93. Plate 87, taken with a kodak from the tug-boat
Page 462
stationed several hundred yards directly ahead of the house-boat, shows the
machine in full flight heading directly for the tug-boat. Although the
aerodrome was about fifteen or twenty feet higher above the level of the
water than the camera, still, at the considerable distance from which the
photograph was taken, this view would not show so much of the under side
unless the machine had been pointing upward. The photograph also proves
very clearly that at the time it was taken the machine had certainly not
dropped at all below the level [p260] at which was launched. In Plate 88 the
camera was unfortunately not well aimed, and only the front guy-post,
bearing points, float and bowsprit are visible, besides the blur of the
propellers, which, it will be noted, were moving very rapidly. The camera
with which this and the succeeding plates were taken was one of the two
special telephoto cameras belonging to the Zoological Park, but built in the
course of the aerodromic work and used where especially rapid shutters
1
were needed. As the shutters on these cameras give an exposure of only 500
of a second, and consequently are sufficiently rapid to show the individual
feathers in a rapidly moving bird’s wing, any distortion of the machine in
flight would certainly have been shown, but, as will be seen from the later
photographs, no distortion of any kind occurred, both the surfaces and the
framework remaining in a perfectly straight condition. Near the bottom of
Plate 88 is the tug from which Plate 87 was taken, and a careful inspection
of Plate 87 shows two persons standing on the roof of the house-boat,
below the upper works, the gentleman on the left being Mr. Thomas W.
Smillie, the official photographer of the Smithsonian Institution, who took
all of the photographs except Plate 87, and, as stated above, used therefor
the special telephoto cameras with the rapid shutters. Plate 89 is an
exceedingly good view, and shows the propellers revolving very rapidly
while Plates 90, 91 and 92 show very clearly that the speed of the propellers
had greatly decreased between the successive photographs. Plate 93 shows
the aerodrome shortly after it touched the water and had been almost
completely submerged, in spite of its floats, by the very strong tide which
was running. Though these plates show all that photographs can, they give
machine in full flight heading directly for the tug-boat. Although the
aerodrome was about fifteen or twenty feet higher above the level of the
water than the camera, still, at the considerable distance from which the
photograph was taken, this view would not show so much of the under side
unless the machine had been pointing upward. The photograph also proves
very clearly that at the time it was taken the machine had certainly not
dropped at all below the level [p260] at which was launched. In Plate 88 the
camera was unfortunately not well aimed, and only the front guy-post,
bearing points, float and bowsprit are visible, besides the blur of the
propellers, which, it will be noted, were moving very rapidly. The camera
with which this and the succeeding plates were taken was one of the two
special telephoto cameras belonging to the Zoological Park, but built in the
course of the aerodromic work and used where especially rapid shutters
1
were needed. As the shutters on these cameras give an exposure of only 500
of a second, and consequently are sufficiently rapid to show the individual
feathers in a rapidly moving bird’s wing, any distortion of the machine in
flight would certainly have been shown, but, as will be seen from the later
photographs, no distortion of any kind occurred, both the surfaces and the
framework remaining in a perfectly straight condition. Near the bottom of
Plate 88 is the tug from which Plate 87 was taken, and a careful inspection
of Plate 87 shows two persons standing on the roof of the house-boat,
below the upper works, the gentleman on the left being Mr. Thomas W.
Smillie, the official photographer of the Smithsonian Institution, who took
all of the photographs except Plate 87, and, as stated above, used therefor
the special telephoto cameras with the rapid shutters. Plate 89 is an
exceedingly good view, and shows the propellers revolving very rapidly
while Plates 90, 91 and 92 show very clearly that the speed of the propellers
had greatly decreased between the successive photographs. Plate 93 shows
the aerodrome shortly after it touched the water and had been almost
completely submerged, in spite of its floats, by the very strong tide which
was running. Though these plates show all that photographs can, they give
Page 463
no adequate idea of the wonder and beauty of the machine when actually in
flight. For while the graceful lines of the machine make it very attractive to
the eye even when stationary, yet when it is actually in flight it seems
veritably endowed with life and intelligence, and the spectacle holds the
observer awed and breathless until the flight is ended. It seems hardly
probable that anyone, no matter how skeptical beforehand, could witness a
flight of one of the models and note the almost bird-like intelligence with
which the automatic adjustments respond to varying conditions of the air
without feeling that, in order to traverse at will the great aerial highway
man no longer needs to wrest from nature some strange, mysterious secret,
but only, by diligent practice with machines of this very type, to acquire an
expertness in the management of the aerodrome not different in kind from
that acquired by every expert bicyclist in the control of his bicycle.
flight. For while the graceful lines of the machine make it very attractive to
the eye even when stationary, yet when it is actually in flight it seems
veritably endowed with life and intelligence, and the spectacle holds the
observer awed and breathless until the flight is ended. It seems hardly
probable that anyone, no matter how skeptical beforehand, could witness a
flight of one of the models and note the almost bird-like intelligence with
which the automatic adjustments respond to varying conditions of the air
without feeling that, in order to traverse at will the great aerial highway
man no longer needs to wrest from nature some strange, mysterious secret,
but only, by diligent practice with machines of this very type, to acquire an
expertness in the management of the aerodrome not different in kind from
that acquired by every expert bicyclist in the control of his bicycle.
Page 464
PL. 86. QUARTER-SIZE MODEL AERODROME MOUNTED ON LAUNCHING-
CAR ◊ lgr
CAR ◊ lgr
Page 465
PL. 87. QUARTER-SIZE MODEL AERODROME IN FLIGHT, AUGUST 8, 1903 ◊
Page 466
PL. 88. QUARTER-SIZE MODEL AERODROME IN FLIGHT, AUGUST 8, 1903 ◊
Page 467
PL. 89. QUARTER-SIZE MODEL AERODROME IN FLIGHT, AUGUST 8, 1903 ◊
Page 468
PL. 90. QUARTER-SIZE MODEL AERODROME IN FLIGHT, AUGUST 8, 1903 ◊
Page 469
PL. 91. QUARTER-SIZE MODEL AERODROME IN FLIGHT, AUGUST 8, 1903 ◊
Page 470
PL. 92. QUARTER-SIZE MODEL AERODROME IN FLIGHT, AUGUST 8, 1903 ◊
Page 471
PL. 93. QUARTER-SIZE MODEL AERODROME AT END OF FLIGHT,
AUGUST 8, 1903 ◊
In describing this flight immediately after it was made, Professor John M.
Manly, who took the photograph shown in Plate 87, said: “The flight of the
small aerodrome was an event which all who saw it will remember for the
rest of their lives. We were, of course, in a state of considerable nervous
excitement and tension, for, after weeks of delay from high winds, rains,
AUGUST 8, 1903 ◊
In describing this flight immediately after it was made, Professor John M.
Manly, who took the photograph shown in Plate 87, said: “The flight of the
small aerodrome was an event which all who saw it will remember for the
rest of their lives. We were, of course, in a state of considerable nervous
excitement and tension, for, after weeks of delay from high winds, rains,
Page 472
and [p261] other uncontrollable causes, at last we had a day ideally suited to
the test. This was, to be sure, not the great test, the final test, the test of the
man-carrying flyer, but it was felt by all to be of almost equal importance,
for if the balancing of the small aerodrome was correct, the large one would
maintain its equilibrium, and the problem of human flight would be solved
practically as well as theoretically. That the weather was now favorable for
the test filled us with excitement. Again and again the favorable moment
had seemed to come, and had gone again before we could make ready for it.
The aerodrome was rapidly carried to the upper works of the house-boat
and the observers and helpers went hastily to their positions. The large tug-
boat was stationed directly ahead, almost in the line of flight, and about a
mile from the house-boat. Signals of readiness were exchanged, and with
every sense astrain we awaited the supreme moment. The rocket gave the
starting signal, and instantly there rushed towards us, moving smoothly,
without a quiver of its wings, with no visible means of motion and no
apparent effort, but with tremendous speed, the strange new inhabitant of
the air. Onward it moved, looking like a huge white moth, but seeming no
creature of this world, not only on account of its size, its ease of movement
and its wonderful speed, but also because of its strange, uncanny beauty. It
seemed visibly and gloriously alive as it advanced, growing rapidly larger
and more impressive. Straight at us it came, and for a moment there was a
wild fear that it would come right on and crush itself against the ponderous
tug-boat. There was a half impulse to move the tug-boat out of its way, but
the aerodrome seemed to realize its danger and rapidly, though not abruptly
or violently, as if it had intelligence and power of self-direction, it checked
its speed and circled to the right, descending slightly. Soon it quickened its
speed again and went straight ahead for about ten seconds, when it again
checked its flight and descended, circling once more. Once again it
attempted to increase its speed and rise, but it was too near the water, and in
a few moments the waves had wet its propellers and wings, and it sank, a
poor, bedraggled creature. But the vision of its beauty and power and
seeming intelligence and life will long remain with those who saw its
flight.”
the test. This was, to be sure, not the great test, the final test, the test of the
man-carrying flyer, but it was felt by all to be of almost equal importance,
for if the balancing of the small aerodrome was correct, the large one would
maintain its equilibrium, and the problem of human flight would be solved
practically as well as theoretically. That the weather was now favorable for
the test filled us with excitement. Again and again the favorable moment
had seemed to come, and had gone again before we could make ready for it.
The aerodrome was rapidly carried to the upper works of the house-boat
and the observers and helpers went hastily to their positions. The large tug-
boat was stationed directly ahead, almost in the line of flight, and about a
mile from the house-boat. Signals of readiness were exchanged, and with
every sense astrain we awaited the supreme moment. The rocket gave the
starting signal, and instantly there rushed towards us, moving smoothly,
without a quiver of its wings, with no visible means of motion and no
apparent effort, but with tremendous speed, the strange new inhabitant of
the air. Onward it moved, looking like a huge white moth, but seeming no
creature of this world, not only on account of its size, its ease of movement
and its wonderful speed, but also because of its strange, uncanny beauty. It
seemed visibly and gloriously alive as it advanced, growing rapidly larger
and more impressive. Straight at us it came, and for a moment there was a
wild fear that it would come right on and crush itself against the ponderous
tug-boat. There was a half impulse to move the tug-boat out of its way, but
the aerodrome seemed to realize its danger and rapidly, though not abruptly
or violently, as if it had intelligence and power of self-direction, it checked
its speed and circled to the right, descending slightly. Soon it quickened its
speed again and went straight ahead for about ten seconds, when it again
checked its flight and descended, circling once more. Once again it
attempted to increase its speed and rise, but it was too near the water, and in
a few moments the waves had wet its propellers and wings, and it sank, a
poor, bedraggled creature. But the vision of its beauty and power and
seeming intelligence and life will long remain with those who saw its
flight.”
Page 473
After removing the model-launching track so that the final arrangements
could be completed for testing the large machine, many weeks of delay
were experienced, almost entirely due to the unusually bad weather
conditions which prevailed, and which were unprecedented for the time of
the year. However, on September 3 the weather became more suitable, and
the aerodrome being in readiness the metal frame of the large machine was
hoisted to the top of the boat and placed on the launching car, and the
wings, rudder, etc., were then hoisted up and properly assembled and
everything made ready for a flight. The parties with the telephoto cameras
were sent to their stations on the shore, where definite base lines had been
marked out so that with the data as to [p262] altitude and azimuth, which
these cameras automatically recorded, the speed, height, etc., of the
machine in flight could be accurately computed. After stationing the tug-
boats at proper points, so as to render assistance should the aerodrome come
down into the water at a considerable distance from the house-boat, it was
found, upon attempting to start the engine, that for some reason it would not
operate. The sparking battery which had been placed at the extreme rear of
the aerodrome was found to be giving such a weak spark that it would not
ignite the mixture in the cylinders. Upon removing the connection which
grounded the terminal of the battery to the framework and replacing it by a
large copper wire leading up to the engine so as to decrease the resistance of
the circuit it was found that the battery still would not give sufficient spark.
A large quantity of dry cells, such as were used for the engine, had been
procured to insure against delay from lack of batteries, but upon attempting
to get a new set from this reserve supply it was found that they, as well as
the set that was on the machine, had so deteriorated that instead of giving
eighteen amperes on short circuit they would give only three, which was not
a sufficient current to enable the engine to operate. No shop tests on the
large engine had been made since the large aerodrome had been brought
down the river, as no provision had been made for properly supporting the
aerodrome in the house-boat in such a way as to permit the large propellers
to whirl around without causing damage, and, therefore, the batteries which
had hitherto proved to be suitable had not had any special test since they
could be completed for testing the large machine, many weeks of delay
were experienced, almost entirely due to the unusually bad weather
conditions which prevailed, and which were unprecedented for the time of
the year. However, on September 3 the weather became more suitable, and
the aerodrome being in readiness the metal frame of the large machine was
hoisted to the top of the boat and placed on the launching car, and the
wings, rudder, etc., were then hoisted up and properly assembled and
everything made ready for a flight. The parties with the telephoto cameras
were sent to their stations on the shore, where definite base lines had been
marked out so that with the data as to [p262] altitude and azimuth, which
these cameras automatically recorded, the speed, height, etc., of the
machine in flight could be accurately computed. After stationing the tug-
boats at proper points, so as to render assistance should the aerodrome come
down into the water at a considerable distance from the house-boat, it was
found, upon attempting to start the engine, that for some reason it would not
operate. The sparking battery which had been placed at the extreme rear of
the aerodrome was found to be giving such a weak spark that it would not
ignite the mixture in the cylinders. Upon removing the connection which
grounded the terminal of the battery to the framework and replacing it by a
large copper wire leading up to the engine so as to decrease the resistance of
the circuit it was found that the battery still would not give sufficient spark.
A large quantity of dry cells, such as were used for the engine, had been
procured to insure against delay from lack of batteries, but upon attempting
to get a new set from this reserve supply it was found that they, as well as
the set that was on the machine, had so deteriorated that instead of giving
eighteen amperes on short circuit they would give only three, which was not
a sufficient current to enable the engine to operate. No shop tests on the
large engine had been made since the large aerodrome had been brought
down the river, as no provision had been made for properly supporting the
aerodrome in the house-boat in such a way as to permit the large propellers
to whirl around without causing damage, and, therefore, the batteries which
had hitherto proved to be suitable had not had any special test since they
Page 474
had been brought down the river. As no batteries suitable for use were on
hand, and as none could be procured from a point nearer than Washington,
the test had to be abandoned for the day and the aerodrome removed to the
interior of the boat.
It was at first impossible to account for the rapid deterioration of so large
a number of dry cells, but it was later found that the damp, penetrating fogs
which had been experienced for nearly two months were responsible for it,
and that in order to preserve the batteries in such a climate it was necessary
to place them in metallic boxes which could be nearly, if not quite,
hermetically sealed. New batteries were immediately procured from
Washington, and before again mounting the aerodrome on the launching
track provision was made for testing the engine inside the house-boat.
PL. 94. HOISTING WING OF FULL-SIZE AERODROME ◊
Up to this time the wings had been stored inside the house-boat by
suspending them from the ceiling, but the time required to hoist them to the
upper works on top of the boat, after the main body of the aerodrome had
hand, and as none could be procured from a point nearer than Washington,
the test had to be abandoned for the day and the aerodrome removed to the
interior of the boat.
It was at first impossible to account for the rapid deterioration of so large
a number of dry cells, but it was later found that the damp, penetrating fogs
which had been experienced for nearly two months were responsible for it,
and that in order to preserve the batteries in such a climate it was necessary
to place them in metallic boxes which could be nearly, if not quite,
hermetically sealed. New batteries were immediately procured from
Washington, and before again mounting the aerodrome on the launching
track provision was made for testing the engine inside the house-boat.
PL. 94. HOISTING WING OF FULL-SIZE AERODROME ◊
Up to this time the wings had been stored inside the house-boat by
suspending them from the ceiling, but the time required to hoist them to the
upper works on top of the boat, after the main body of the aerodrome had
Page 475
been placed on the launching car preparatory to making a flight, had added
so greatly to the delay, and consequently to the difficulty of getting the
machine entirely ready for a flight while the weather conditions remained
suitable for a test, that it was decided to build some framework on the upper
works and cover it with canvas so as to provide some boxes in which the
wings could be [p263] stored whenever it seemed probable that a flight
would soon be possible. Some of the difficulties experienced in hoisting
these wings from the interior of the boat to the upper works may be
appreciated by an inspection of Plate 94, where one of them is seen just
ready to be hoisted from the raft. Only one wing at a time could be handled
on the raft, even when there was no appreciable wind or roughness of the
water, so that in order to hoist all four wings the raft had to be hauled
around from the door at the end of the boat to the side where the wing was
hoisted, and back again four times every time the machine was assembled
preparatory to a flight. The necessity for making occasional tests of the
engine in order to make sure that no trouble would be again experienced in
having proper batteries, etc., for the engine when the machine was again on
the point of being launched also made it imperative to remove the wings
from the interior of the house-boat, as the tremendous blasts of air from the
propellers would certainly have wrecked the wings had they remained in the
boat while the engine was being tested.
After the wings had been stored in the “wing boxes,” thorough tests of
the engine were made, and before there came another day which was at all
suitable for a trial, it was accidentally discovered that the glued joints in the
cross-ribs of the large wings had been softened by the moisture of the fogs
which had penetrated everything, and that the joints had all opened up and
left the ribs in a practically useless condition.
It will be recalled from the description of these cross-ribs, Chapter VI ◊,
that the rib is composed of two channel-shaped strips, the edges of which
are glued together while the strips are bent over a form which causes the
ribs to maintain the curved form desired after the glue has hardened.
Recalling these facts, it will be readily understood that there is at all times a
considerable strain on the glued joints due to the two strips of wood trying
so greatly to the delay, and consequently to the difficulty of getting the
machine entirely ready for a flight while the weather conditions remained
suitable for a test, that it was decided to build some framework on the upper
works and cover it with canvas so as to provide some boxes in which the
wings could be [p263] stored whenever it seemed probable that a flight
would soon be possible. Some of the difficulties experienced in hoisting
these wings from the interior of the boat to the upper works may be
appreciated by an inspection of Plate 94, where one of them is seen just
ready to be hoisted from the raft. Only one wing at a time could be handled
on the raft, even when there was no appreciable wind or roughness of the
water, so that in order to hoist all four wings the raft had to be hauled
around from the door at the end of the boat to the side where the wing was
hoisted, and back again four times every time the machine was assembled
preparatory to a flight. The necessity for making occasional tests of the
engine in order to make sure that no trouble would be again experienced in
having proper batteries, etc., for the engine when the machine was again on
the point of being launched also made it imperative to remove the wings
from the interior of the house-boat, as the tremendous blasts of air from the
propellers would certainly have wrecked the wings had they remained in the
boat while the engine was being tested.
After the wings had been stored in the “wing boxes,” thorough tests of
the engine were made, and before there came another day which was at all
suitable for a trial, it was accidentally discovered that the glued joints in the
cross-ribs of the large wings had been softened by the moisture of the fogs
which had penetrated everything, and that the joints had all opened up and
left the ribs in a practically useless condition.
It will be recalled from the description of these cross-ribs, Chapter VI ◊,
that the rib is composed of two channel-shaped strips, the edges of which
are glued together while the strips are bent over a form which causes the
ribs to maintain the curved form desired after the glue has hardened.
Recalling these facts, it will be readily understood that there is at all times a
considerable strain on the glued joints due to the two strips of wood trying
Page 476
to straighten out, and, therefore, if the glue should at any time become
softened sufficiently to allow one strip to slide along on the other, the joint
would open up and the rib would consequently become straight. When the
construction of the hollow ribs was first contemplated it was realized that
although the hollow construction would enable the ribs to be strong, and at
the same time exceedingly light, yet it would make it imperative that the
ribs be covered with a water-proof varnish in order to prevent the glue from
being softened when the aerodrome came down into the water, as it was
expected from the first that it would do at the end of its flight. Considerable
time and attention had, therefore, been given to this very problem of
securing a suitable water-proof varnish, and ribs coated with the varnish
which was finally used had been submerged in water for more than 24
hours in testing this very point, and no softening of the glue could be
detected after this long submergence. It had, therefore, been felt that the ribs
had been given a test which was much more severe than any conditions
which [p264] were likely to be met with, since the aerodrome would, in no
case which could be anticipated, be in the water for so long a period as 24
hours, and no trouble from this source need be anticipated.
In the present case, however, the moisture of the atmosphere, which had
been heavily laden with fog for several weeks, had penetrated the varnish
and softened the glue, even though the submergence of 24 hours in water
had shown no effect. To construct new ribs for the wings would have
required several weeks, and the delays which had already been experienced
had by this time prolonged the stay down the river so greatly that even
under the very best conditions it seemed hardly possible to complete the
tests before the coming of the equinoxial storms, which would make it
necessary to remove the boat from the middle of the river and place it in a
safe harbor. Something, therefore, had to be done, and that very quickly, so
that an immediate test could be made, or else the tests would have to be
delayed until the following season, or possibly postponed indefinitely on
account of the lack of funds.
Owing to the varnish with which the ribs were covered, it was impossible
in repairing them to carry out the first plan which suggested itself of
softened sufficiently to allow one strip to slide along on the other, the joint
would open up and the rib would consequently become straight. When the
construction of the hollow ribs was first contemplated it was realized that
although the hollow construction would enable the ribs to be strong, and at
the same time exceedingly light, yet it would make it imperative that the
ribs be covered with a water-proof varnish in order to prevent the glue from
being softened when the aerodrome came down into the water, as it was
expected from the first that it would do at the end of its flight. Considerable
time and attention had, therefore, been given to this very problem of
securing a suitable water-proof varnish, and ribs coated with the varnish
which was finally used had been submerged in water for more than 24
hours in testing this very point, and no softening of the glue could be
detected after this long submergence. It had, therefore, been felt that the ribs
had been given a test which was much more severe than any conditions
which [p264] were likely to be met with, since the aerodrome would, in no
case which could be anticipated, be in the water for so long a period as 24
hours, and no trouble from this source need be anticipated.
In the present case, however, the moisture of the atmosphere, which had
been heavily laden with fog for several weeks, had penetrated the varnish
and softened the glue, even though the submergence of 24 hours in water
had shown no effect. To construct new ribs for the wings would have
required several weeks, and the delays which had already been experienced
had by this time prolonged the stay down the river so greatly that even
under the very best conditions it seemed hardly possible to complete the
tests before the coming of the equinoxial storms, which would make it
necessary to remove the boat from the middle of the river and place it in a
safe harbor. Something, therefore, had to be done, and that very quickly, so
that an immediate test could be made, or else the tests would have to be
delayed until the following season, or possibly postponed indefinitely on
account of the lack of funds.
Owing to the varnish with which the ribs were covered, it was impossible
in repairing them to carry out the first plan which suggested itself of
Page 477
binding the ribs with a strip of cloth impregnated with glue and wound
spirally from end to end. As the wood was so very thin, it was impossible to
bind the two parts together with wire, and even thin bands of metal driven
up on the tapered portion of the rib were not likely to draw the two strips
together without crushing the wood. What was finally done was to scrape
the edges of the two strips where the joint had opened, thereby removing all
the old glue, and after putting fresh glue on all these edges the two strips
were drawn together and bound with surgeons’ tape, which was found to
adhere very firmly even to the varnished surface.
After repairing the ribs in this manner and readjusting the guy-wires of
their framework so as to make the wing assume the correct form, which had
been slightly altered by the warping and twisting consequent on the opening
up of the ribs, everything was again in readiness for a test in free flight,
numerous tests of the engine having meanwhile been made both with the
aerodrome frame inside of the house-boat and also when mounted on the
launching track above. The weather, which had been unprecedentedly bad
all summer, now became even worse, and although short periods of calm
lasting an hour or less occasionally occurred, there were for several weeks
no calm periods long enough for completing the necessary preparations and
making a test, although the time required for assembling the aerodrome had
been greatly shortened by building the “wing boxes” on the superstructure,
and in other ways previously described. On several occasions when an
attempt was made to utilize what appeared to be a relative calm, the
aerodrome was assembled on the launching apparatus and everything got in
readiness except the actual fastening of the [p265] wings and rudder to it, but
in every instance, before the wings could be actually applied and a flight
made, the wind became so strong as to absolutely prohibit a test. On two
occasions when the wings were actually attached, heavy rain storms
suddenly came up and drenched the machine before the wings could be
removed, and on several occasions it was necessary to leave the entire metal
frame and engine of the aerodrome mounted on top of the boat all night,
because the heavy sea which was running made it impossible to utilize the
large raft in returning the frame to the interior of the boat.
spirally from end to end. As the wood was so very thin, it was impossible to
bind the two parts together with wire, and even thin bands of metal driven
up on the tapered portion of the rib were not likely to draw the two strips
together without crushing the wood. What was finally done was to scrape
the edges of the two strips where the joint had opened, thereby removing all
the old glue, and after putting fresh glue on all these edges the two strips
were drawn together and bound with surgeons’ tape, which was found to
adhere very firmly even to the varnished surface.
After repairing the ribs in this manner and readjusting the guy-wires of
their framework so as to make the wing assume the correct form, which had
been slightly altered by the warping and twisting consequent on the opening
up of the ribs, everything was again in readiness for a test in free flight,
numerous tests of the engine having meanwhile been made both with the
aerodrome frame inside of the house-boat and also when mounted on the
launching track above. The weather, which had been unprecedentedly bad
all summer, now became even worse, and although short periods of calm
lasting an hour or less occasionally occurred, there were for several weeks
no calm periods long enough for completing the necessary preparations and
making a test, although the time required for assembling the aerodrome had
been greatly shortened by building the “wing boxes” on the superstructure,
and in other ways previously described. On several occasions when an
attempt was made to utilize what appeared to be a relative calm, the
aerodrome was assembled on the launching apparatus and everything got in
readiness except the actual fastening of the [p265] wings and rudder to it, but
in every instance, before the wings could be actually applied and a flight
made, the wind became so strong as to absolutely prohibit a test. On two
occasions when the wings were actually attached, heavy rain storms
suddenly came up and drenched the machine before the wings could be
removed, and on several occasions it was necessary to leave the entire metal
frame and engine of the aerodrome mounted on top of the boat all night,
because the heavy sea which was running made it impossible to utilize the
large raft in returning the frame to the interior of the boat.
Page 478
Finally, however, after it seemed almost useless to hope for calm weather,
what appeared to be a most propitious day arrived on October 7. The wind
which had been quite high in the early morning gradually quieted until at 10
a. m. it was blowing only about twelve miles per hour and the indications
were that it would quiet down still more. Every energy was concentrated in
getting the aerodrome ready at the earliest possible moment, as previous
experience had shown too clearly that the conditions might be completely
reversed in less than an hour. As the tide and wind caused the boat to swing
up the river from its buoy, and thus made the launching track point down
the river, the steam tug-boat was sent down the river for a distance of a mile
or more so that, should the aerodrome come down into the water without
being able to make a return trip to the house-boat, the tug-boat would be
able to reach it quickly and render assistance to both the writer and the
machine should they need it. At 12.20 p. m. everything was in readiness and
what appeared to be the decisive moment had arrived, when the writer, after
starting up the engine and gradually raising its speed to the maximum, and
after taking the last survey of the whole machine to insure that everything
was as it should be, finally gave the orders to release it.
Although the writer did not have the privilege of seeing it glide down the
track, as his attention was too thoroughly engaged in insuring that he was in
the proper position for reaching immediately any of the control apparatus,
either of the aerodrome or of the engine, yet those who did witness the
actual passage of the machine down the track have said that the sight was
most impressive and majestic. No sign of jar was apparent when the
machine was first released, but with lightning-like rapidity it gathered its
speed as it rushed down the sixty feet of track, the end of which it reached
in three seconds, at which time it had attained a speed of something over
thirty-two feet per second. Just as the machine reached the end of the track
the writer felt a sudden shock, immediately followed by an indescribable
sensation of being free in the air, which had hardly been realized before the
important fact was intuitively felt that the machine was plunging downward
at a very sharp angle, and he instinctively grasped the wheel which controls
the Pénaud tail and threw it to its uppermost extent in an attempt to depress
what appeared to be a most propitious day arrived on October 7. The wind
which had been quite high in the early morning gradually quieted until at 10
a. m. it was blowing only about twelve miles per hour and the indications
were that it would quiet down still more. Every energy was concentrated in
getting the aerodrome ready at the earliest possible moment, as previous
experience had shown too clearly that the conditions might be completely
reversed in less than an hour. As the tide and wind caused the boat to swing
up the river from its buoy, and thus made the launching track point down
the river, the steam tug-boat was sent down the river for a distance of a mile
or more so that, should the aerodrome come down into the water without
being able to make a return trip to the house-boat, the tug-boat would be
able to reach it quickly and render assistance to both the writer and the
machine should they need it. At 12.20 p. m. everything was in readiness and
what appeared to be the decisive moment had arrived, when the writer, after
starting up the engine and gradually raising its speed to the maximum, and
after taking the last survey of the whole machine to insure that everything
was as it should be, finally gave the orders to release it.
Although the writer did not have the privilege of seeing it glide down the
track, as his attention was too thoroughly engaged in insuring that he was in
the proper position for reaching immediately any of the control apparatus,
either of the aerodrome or of the engine, yet those who did witness the
actual passage of the machine down the track have said that the sight was
most impressive and majestic. No sign of jar was apparent when the
machine was first released, but with lightning-like rapidity it gathered its
speed as it rushed down the sixty feet of track, the end of which it reached
in three seconds, at which time it had attained a speed of something over
thirty-two feet per second. Just as the machine reached the end of the track
the writer felt a sudden shock, immediately followed by an indescribable
sensation of being free in the air, which had hardly been realized before the
important fact was intuitively felt that the machine was plunging downward
at a very sharp angle, and he instinctively grasped the wheel which controls
the Pénaud tail and threw it to its uppermost extent in an attempt to depress
Page 479
the rear of the machine and [p266] thereby overcome the sharp angle of
descent. Finding that the machine made no response to this extreme
movement of the tail, he immediately realized that a crash into the water
was unavoidable and braced himself for the shock. The tremendous crash of
the front wings being completely demolished as they struck the water had
hardly become apparent before he found himself and the machine plunging
downward through the water. By some instinct he grasped the main guy-
wires which were above his head, and pulling himself through the narrow
space between them freed himself from the machine and swam upward as
rapidly as possible. A few moments after reaching the surface of the water
the uppermost point of the pyramid of the machine was seen to project from
the water and he swam over and sat down on it until a row-boat could be
sent to it from the nearby power-boat.
The first thing that the writer saw after looking around him was a
newspaper reporter, his boatman expending the utmost limit of his power in
pushing his boat ahead to be the first one to arrive.
After giving directions to the workmen regarding the recovery of the
machine, the writer returned to the house-boat to obtain dry clothing, and
although his first inclination was not to make any statement until a
complete examination could be made to determine both the cause of the
lack of success and also the extent of the damage which had been sustained
by the machine, yet owing to the very great pressure brought to bear by the
press representatives who said that unless some statement was given out
they would write their own conclusions as to the cause of the mishap, he
finally gave out the following statement:
STATEMENT MADE BY MR. MANLY TO ASSOCIATED PRESS
“It must be understood that the test to-day was entirely an experiment, and the first of its kind
ever made. The experiment was unsuccessful. The balancing, upon which depends the success of a
flight, was based upon the tests of the models and proved to be incorrect, but only an actual trial of
the full-size machine itself could determine this. My confidence in the future success of the work
is unchanged. I can give you no further information. I shall make a formal report to Secretary
Langley.”
descent. Finding that the machine made no response to this extreme
movement of the tail, he immediately realized that a crash into the water
was unavoidable and braced himself for the shock. The tremendous crash of
the front wings being completely demolished as they struck the water had
hardly become apparent before he found himself and the machine plunging
downward through the water. By some instinct he grasped the main guy-
wires which were above his head, and pulling himself through the narrow
space between them freed himself from the machine and swam upward as
rapidly as possible. A few moments after reaching the surface of the water
the uppermost point of the pyramid of the machine was seen to project from
the water and he swam over and sat down on it until a row-boat could be
sent to it from the nearby power-boat.
The first thing that the writer saw after looking around him was a
newspaper reporter, his boatman expending the utmost limit of his power in
pushing his boat ahead to be the first one to arrive.
After giving directions to the workmen regarding the recovery of the
machine, the writer returned to the house-boat to obtain dry clothing, and
although his first inclination was not to make any statement until a
complete examination could be made to determine both the cause of the
lack of success and also the extent of the damage which had been sustained
by the machine, yet owing to the very great pressure brought to bear by the
press representatives who said that unless some statement was given out
they would write their own conclusions as to the cause of the mishap, he
finally gave out the following statement:
STATEMENT MADE BY MR. MANLY TO ASSOCIATED PRESS
“It must be understood that the test to-day was entirely an experiment, and the first of its kind
ever made. The experiment was unsuccessful. The balancing, upon which depends the success of a
flight, was based upon the tests of the models and proved to be incorrect, but only an actual trial of
the full-size machine itself could determine this. My confidence in the future success of the work
is unchanged. I can give you no further information. I shall make a formal report to Secretary
Langley.”
Page 480
PL. 95. FLIGHT OF LARGE AERODROME, OCTOBER 7, 1903 ◊
Page 481
PL. 96. FLIGHT OF LARGE AERODROME, OCTOBER 7, 1903 ◊
PHOTOGRAPH BY T. W. SMILLIE
After recovering the machine the foreman of the workmen (Mr. Reed)
[who together with Mr. McDonald were the only ones on top of the boat
when the launching actually took place], busied himself to discover what
had caused the jerk to the machine at the moment it was released, which
had been immediately followed by the great depression of the front end.
After some little time he discovered that the upright guide at the extreme
front of the launching car (which, as heretofore stated, was slotted to
receive a metal lug projecting from the end of the guy-post, and thus
prevent the front end of the [p267] framework from being twisted by a side
wind striking the machine while it was still on the launching car) had been
distorted, the metal cap on it being stretched out of shape in a way which
indicated that the pin of the front guy-post had hung in the cap, and that the
PHOTOGRAPH BY T. W. SMILLIE
After recovering the machine the foreman of the workmen (Mr. Reed)
[who together with Mr. McDonald were the only ones on top of the boat
when the launching actually took place], busied himself to discover what
had caused the jerk to the machine at the moment it was released, which
had been immediately followed by the great depression of the front end.
After some little time he discovered that the upright guide at the extreme
front of the launching car (which, as heretofore stated, was slotted to
receive a metal lug projecting from the end of the guy-post, and thus
prevent the front end of the [p267] framework from being twisted by a side
wind striking the machine while it was still on the launching car) had been
distorted, the metal cap on it being stretched out of shape in a way which
indicated that the pin of the front guy-post had hung in the cap, and that the
Page 482
guy-post was not therefore free from this part of the car when the end of the
launching track dropped. The shock which the writer felt at the moment of
launching and which had also been seen by others to occur was thus
conclusively shown to have been due to the falling track, dragging the front
end of the machine down with it. As the machine was travelling forward
and the car had been almost instantly brought to a standstill by its buffer
pistons co-acting with the buffer cylinders at the foot of the track, this front
guy-post had been pulled backwards, and thus not only pulled the main
guy-wires of the wings backwards and thereby depressed the front edge of
the front wings so that they had no angle of inclination, but had also bent
the front end of the metal framework downward,—effects which were
discovered from the later examination of the frame and the guy-post itself.
From the instantaneous photographs which were obtained, indisputable
evidence was obtained that this was what actually occurred. Referring to the
photograph, Plate 95, which was taken by Mr. G. H. Powell, Secretary of
the Board of Ordnance and Fortification, and which shows the machine just
a few feet in front of the point where it was actually launched, it will at
once be seen that the front end of the frame is bent downward and that the
front guy-post instead of being parallel with the rear one has been deflected
backward at the lower end through an angle of 30 degrees. Referring further
to the photograph, Plate 96, which was taken at the same instant as the one
just described, it will be seen that even this one, which is a view of the
machine as it passed almost directly over Mr. Smillie’s head, most clearly
shows the extreme extent to which the front wings had been distorted, the
rear edges of the wings near the frame having been twisted up until they
struck the cross-frame, and the outer ends being free to twist had been
forced up very much higher.
After completing the recovery of the machine and the examination as to
the extent of the injuries it had sustained, and finding unquestionable
evidence that the accident had been caused by the front guy-post hanging in
its guide block on the launching car, the workmen were set to work
straightening out and arranging the various parts, fittings and accessories,
and cleaning up the engine which fortunately had sustained no injury
launching track dropped. The shock which the writer felt at the moment of
launching and which had also been seen by others to occur was thus
conclusively shown to have been due to the falling track, dragging the front
end of the machine down with it. As the machine was travelling forward
and the car had been almost instantly brought to a standstill by its buffer
pistons co-acting with the buffer cylinders at the foot of the track, this front
guy-post had been pulled backwards, and thus not only pulled the main
guy-wires of the wings backwards and thereby depressed the front edge of
the front wings so that they had no angle of inclination, but had also bent
the front end of the metal framework downward,—effects which were
discovered from the later examination of the frame and the guy-post itself.
From the instantaneous photographs which were obtained, indisputable
evidence was obtained that this was what actually occurred. Referring to the
photograph, Plate 95, which was taken by Mr. G. H. Powell, Secretary of
the Board of Ordnance and Fortification, and which shows the machine just
a few feet in front of the point where it was actually launched, it will at
once be seen that the front end of the frame is bent downward and that the
front guy-post instead of being parallel with the rear one has been deflected
backward at the lower end through an angle of 30 degrees. Referring further
to the photograph, Plate 96, which was taken at the same instant as the one
just described, it will be seen that even this one, which is a view of the
machine as it passed almost directly over Mr. Smillie’s head, most clearly
shows the extreme extent to which the front wings had been distorted, the
rear edges of the wings near the frame having been twisted up until they
struck the cross-frame, and the outer ends being free to twist had been
forced up very much higher.
After completing the recovery of the machine and the examination as to
the extent of the injuries it had sustained, and finding unquestionable
evidence that the accident had been caused by the front guy-post hanging in
its guide block on the launching car, the workmen were set to work
straightening out and arranging the various parts, fittings and accessories,
and cleaning up the engine which fortunately had sustained no injury
Page 483
whatever. After a consultation in Washington with Mr. Langley, who had
been unable to be present at the experiment, both concerning what had
already occurred and also what should be done regarding the future of the
work, and in view of the fact that the statement which the writer had given
to the press representatives, immediately after the accident, had been made
before there had been time to make an examination of the machine itself, it
was decided that it would be best to give to the press [p268] a short statement
to correct the earlier one, and Mr. Langley accordingly made public the
following note:
“Mr. Langley states that he was not an eye witness of the experiment at Widewater yesterday,
having been detained in Washington by business, but that on the report of Mr. Manly, immediately
in charge, he is able to say that the latter’s first impression that there had been defective balancing
was corrected by a minuter examination, when the clutch, which held the aerodrome on the
launching ways and which should have released it at the instant of the fall, was found to be injured.
“The machinery was working perfectly and giving every reason to anticipate a successful flight,
when this accident (due wholly to the launching mechanism) drew the aerodrome abruptly
downward at the moment of release and cast it into the water near the house-boat. The statement
that the machine failed for lack of power to fly was wholly a mistaken one.
“The engine, the frame and all the more important parts were practically uninjured. The engine
is actually in good working order. The damage done was confined to the slighter portions, like the
canvas wings and propellers, and these can be readily replaced.
“The belief of those charged with the experiment in the ultimate successful working of the
machine is in no way affected by this accident, which is one of the large chapter of accidents that
beset the initial stages of experiments so novel as the present ones. It is chiefly unfortunate in
coming at the end of the season when outdoor work of this sort is impossible.
“Whether the experiments will be continued this year or not has not yet been determined.”
In view of the many inaccurate accounts published in the daily press at
the time of this experiment, special attention is directed to the fact that even
under the enormous strain to which the aerodrome was subjected, due to its
striking the water at an angle of approximately forty-five degrees and at a
speed certainly not less than forty miles an hour, no bending or distortion of
any kind was found in the frame after it was recovered, except that a slight
depression at the front had been produced by the lower guy-post catching
on the launching car, as previously described. This is very clearly seen in
Plate 97, Fig. 1, which shows the aerodrome being hoisted from the water,
and in Plate 97, Fig. 2, which shows it just afterwards resting on the raft, the
wings, tail and rudder having been completely demolished by towing it
been unable to be present at the experiment, both concerning what had
already occurred and also what should be done regarding the future of the
work, and in view of the fact that the statement which the writer had given
to the press representatives, immediately after the accident, had been made
before there had been time to make an examination of the machine itself, it
was decided that it would be best to give to the press [p268] a short statement
to correct the earlier one, and Mr. Langley accordingly made public the
following note:
“Mr. Langley states that he was not an eye witness of the experiment at Widewater yesterday,
having been detained in Washington by business, but that on the report of Mr. Manly, immediately
in charge, he is able to say that the latter’s first impression that there had been defective balancing
was corrected by a minuter examination, when the clutch, which held the aerodrome on the
launching ways and which should have released it at the instant of the fall, was found to be injured.
“The machinery was working perfectly and giving every reason to anticipate a successful flight,
when this accident (due wholly to the launching mechanism) drew the aerodrome abruptly
downward at the moment of release and cast it into the water near the house-boat. The statement
that the machine failed for lack of power to fly was wholly a mistaken one.
“The engine, the frame and all the more important parts were practically uninjured. The engine
is actually in good working order. The damage done was confined to the slighter portions, like the
canvas wings and propellers, and these can be readily replaced.
“The belief of those charged with the experiment in the ultimate successful working of the
machine is in no way affected by this accident, which is one of the large chapter of accidents that
beset the initial stages of experiments so novel as the present ones. It is chiefly unfortunate in
coming at the end of the season when outdoor work of this sort is impossible.
“Whether the experiments will be continued this year or not has not yet been determined.”
In view of the many inaccurate accounts published in the daily press at
the time of this experiment, special attention is directed to the fact that even
under the enormous strain to which the aerodrome was subjected, due to its
striking the water at an angle of approximately forty-five degrees and at a
speed certainly not less than forty miles an hour, no bending or distortion of
any kind was found in the frame after it was recovered, except that a slight
depression at the front had been produced by the lower guy-post catching
on the launching car, as previously described. This is very clearly seen in
Plate 97, Fig. 1, which shows the aerodrome being hoisted from the water,
and in Plate 97, Fig. 2, which shows it just afterwards resting on the raft, the
wings, tail and rudder having been completely demolished by towing it
Page 484
through the water to the house-boat from the place where it struck the
water. This single distortion, therefore, was in no way a result of the strains
experienced by the frame either while it was in the air or when it struck the
water. Some of the press reports, and, in fact, some of the accounts
published in the scientific press, stated that the aerodrome frame had proved
so weak that it broke while the machine was in the air, and that this was the
cause of the accident. Nothing could be farther from the actual facts than
this, for though there were many things connected with the machine which
could not be properly tested until it was actually in the air, yet the strength
of the frame had been most thoroughly [p269] tested in the shops prior to the
trial, and it had been found that with the frame supported only at the
extreme front and rear, no appreciable deflection was produced upon it by
the concentrated weight of four men at the center, even when they
simultaneously jumped up and down on it. That the aerodrome frame was
amply strong was further evidenced by the fact that in the later trial,
hereafter described, no injury was sustained by the frame even when the
machine turned over in mid-air and struck the water flat on its back. In fact,
no point regarding the aerodrome is more certain than that the frame was
more than strong enough for its purpose.
Plates 98 to 100 show the aerodrome in the water from the moment after
it arose and the writer, who had extricated himself while it was plunging
down through the water and beat it to the surface, had swum over to it and
sat down on the upper pyramid to await a row-boat, until the machine was
taken in tow by the tug-boat.
As the weather conditions were continually growing worse, owing to the
lateness of the season, it was decided that it would be absolutely impossible
to undertake to keep the house-boat down the river until the aerodrome
could be repaired and another test made, and the writer accordingly
returned to Quantico on the following day, expecting to take the tug-boat
from there to the house-boat and complete arrangements for bringing
everything to Washington. On reaching Quantico, however, it was found
that a most violent storm was raging on the river, and had, in fact, been
increasing in violence since the evening of October 7, immediately
water. This single distortion, therefore, was in no way a result of the strains
experienced by the frame either while it was in the air or when it struck the
water. Some of the press reports, and, in fact, some of the accounts
published in the scientific press, stated that the aerodrome frame had proved
so weak that it broke while the machine was in the air, and that this was the
cause of the accident. Nothing could be farther from the actual facts than
this, for though there were many things connected with the machine which
could not be properly tested until it was actually in the air, yet the strength
of the frame had been most thoroughly [p269] tested in the shops prior to the
trial, and it had been found that with the frame supported only at the
extreme front and rear, no appreciable deflection was produced upon it by
the concentrated weight of four men at the center, even when they
simultaneously jumped up and down on it. That the aerodrome frame was
amply strong was further evidenced by the fact that in the later trial,
hereafter described, no injury was sustained by the frame even when the
machine turned over in mid-air and struck the water flat on its back. In fact,
no point regarding the aerodrome is more certain than that the frame was
more than strong enough for its purpose.
Plates 98 to 100 show the aerodrome in the water from the moment after
it arose and the writer, who had extricated himself while it was plunging
down through the water and beat it to the surface, had swum over to it and
sat down on the upper pyramid to await a row-boat, until the machine was
taken in tow by the tug-boat.
As the weather conditions were continually growing worse, owing to the
lateness of the season, it was decided that it would be absolutely impossible
to undertake to keep the house-boat down the river until the aerodrome
could be repaired and another test made, and the writer accordingly
returned to Quantico on the following day, expecting to take the tug-boat
from there to the house-boat and complete arrangements for bringing
everything to Washington. On reaching Quantico, however, it was found
that a most violent storm was raging on the river, and had, in fact, been
increasing in violence since the evening of October 7, immediately
Page 485
following the trial. On account of the storm it was impossible to reach the
house-boat or to get into communication with the workmen, who had
sought refuge at the hotel at Clifton Beach, as the tug-boat itself was not at
the point at which it was expected to be found, and, in fact, it had not been
seen by any of the river people since the morning of October 8, when it was
seen taking the workmen from the boat to Clifton Beach. Two days later, or
October 11, when the storm had subsided and the tug-boat, which had been
blown many miles down the river, was able to return the workmen to the
house-boat, it was found that the storm had made a complete wreck of all
the row-boats, the power-launch, and the large raft. The row-boats had been
completely demolished on the beaches, the launch had been broken from its
moorings to the house-boat and driven ashore some four miles down the
river, where it was found with the deck torn completely off, a large hole
stove in it amidships, and the engine seriously damaged, while the raft had
been very seriously damaged on the beach many miles down the river. After
making temporary repairs to the raft and getting it launched, it was used as
a floating dock for making temporary repairs on the power-launch; both
were then returned to their moorings at the house-boat and everything got in
readiness for towing the house-boat to Washington, and this was finally
accomplished on October 12. [p270] Even while the boat was en route some
of the workmen were busily engaged in the repair of the damaged parts, the
others having been sent ahead to Washington to begin work on the
construction of new wings, so that another trial could be had at the earliest
moment that the weather would permit.
One extra pair of wings was on hand, but these had been stored in the
house-boat while it was down the river, and the damp weather, which had
caused such serious damage to the cross-ribs of the wings which were
actually used, had also so seriously affected the ribs of these extra wings
that it was necessary to discard some of them and repair the others. An extra
Pénaud tail was on hand, as well as a steering rudder, and it was estimated
that unless some unforeseen delay occurred the aerodrome would be ready
for flight in three weeks.
house-boat or to get into communication with the workmen, who had
sought refuge at the hotel at Clifton Beach, as the tug-boat itself was not at
the point at which it was expected to be found, and, in fact, it had not been
seen by any of the river people since the morning of October 8, when it was
seen taking the workmen from the boat to Clifton Beach. Two days later, or
October 11, when the storm had subsided and the tug-boat, which had been
blown many miles down the river, was able to return the workmen to the
house-boat, it was found that the storm had made a complete wreck of all
the row-boats, the power-launch, and the large raft. The row-boats had been
completely demolished on the beaches, the launch had been broken from its
moorings to the house-boat and driven ashore some four miles down the
river, where it was found with the deck torn completely off, a large hole
stove in it amidships, and the engine seriously damaged, while the raft had
been very seriously damaged on the beach many miles down the river. After
making temporary repairs to the raft and getting it launched, it was used as
a floating dock for making temporary repairs on the power-launch; both
were then returned to their moorings at the house-boat and everything got in
readiness for towing the house-boat to Washington, and this was finally
accomplished on October 12. [p270] Even while the boat was en route some
of the workmen were busily engaged in the repair of the damaged parts, the
others having been sent ahead to Washington to begin work on the
construction of new wings, so that another trial could be had at the earliest
moment that the weather would permit.
One extra pair of wings was on hand, but these had been stored in the
house-boat while it was down the river, and the damp weather, which had
caused such serious damage to the cross-ribs of the wings which were
actually used, had also so seriously affected the ribs of these extra wings
that it was necessary to discard some of them and repair the others. An extra
Pénaud tail was on hand, as well as a steering rudder, and it was estimated
that unless some unforeseen delay occurred the aerodrome would be ready
for flight in three weeks.
Page 486
After making a careful examination of the places on the river which
seemed most available for an experiment, it was finally decided to make the
next test just off the Potomac Flats, at the junction of the main body of the
river and the Eastern Branch, the traffic on this part of the river, which
would have been more dangerous and troublesome during the summer,
being quite light at this time of the year. By making the experiment at this
point it was possible to leave the house-boat at its dock until the weather
seemed suitable and then have a tug-boat tow it to the exact point, which
would be determined by the state of the wind and the tide.
After more completely examining the condition of the framework of the
machine, and discussing and maturely deliberating on the causes which had
led to the accident of October 7, the writer advised Mr. Langley not to make
any changes either in the machine itself or in the launching apparatus,
except to remove the small lug from the metal rod which projected from the
end of the guy-post, and which by catching in its guide on the launching car
had been the sole cause of the accident. The aerodrome was accordingly
repaired so as to reproduce exactly the conditions which obtained at the
time of the previous experiment, except for this slight change, and it was
again ready for trial by the middle of November. The weather, however, at
this time was very variable, there being at times comparatively quiet
periods which lasted for only an hour or less, which was not sufficient time
for procuring a tug-boat and towing the boat to the proper point, and then
assembling the aerodrome and making a trial. However, after many days
waiting, what appeared to be an exceptionally quiet day occurred on
December 8, the wind quieting down by noon to such an extent that
practically a dead calm prevailed. Vigorous search was immediately
instituted for a tug-boat to tow the house-boat to the point selected, but it
was very late in the afternoon before one could be procured, and by the time
the boat arrived at the proper place darkness was descending and a strong
[p271] and exceedingly gusty wind had sprung up, and it seemed almost
disastrous to attempt an experiment.
seemed most available for an experiment, it was finally decided to make the
next test just off the Potomac Flats, at the junction of the main body of the
river and the Eastern Branch, the traffic on this part of the river, which
would have been more dangerous and troublesome during the summer,
being quite light at this time of the year. By making the experiment at this
point it was possible to leave the house-boat at its dock until the weather
seemed suitable and then have a tug-boat tow it to the exact point, which
would be determined by the state of the wind and the tide.
After more completely examining the condition of the framework of the
machine, and discussing and maturely deliberating on the causes which had
led to the accident of October 7, the writer advised Mr. Langley not to make
any changes either in the machine itself or in the launching apparatus,
except to remove the small lug from the metal rod which projected from the
end of the guy-post, and which by catching in its guide on the launching car
had been the sole cause of the accident. The aerodrome was accordingly
repaired so as to reproduce exactly the conditions which obtained at the
time of the previous experiment, except for this slight change, and it was
again ready for trial by the middle of November. The weather, however, at
this time was very variable, there being at times comparatively quiet
periods which lasted for only an hour or less, which was not sufficient time
for procuring a tug-boat and towing the boat to the proper point, and then
assembling the aerodrome and making a trial. However, after many days
waiting, what appeared to be an exceptionally quiet day occurred on
December 8, the wind quieting down by noon to such an extent that
practically a dead calm prevailed. Vigorous search was immediately
instituted for a tug-boat to tow the house-boat to the point selected, but it
was very late in the afternoon before one could be procured, and by the time
the boat arrived at the proper place darkness was descending and a strong
[p271] and exceedingly gusty wind had sprung up, and it seemed almost
disastrous to attempt an experiment.
Page 487
PL. 97. AERODROME BEING RECOVERED, OCTOBER 7, 1903 ◊
Page 488
PL. 98. AERODROME IN WATER, OCTOBER 7, 1903 ◊
Page 489
PL. 99. AERODROME IN WATER, OCTOBER 7, 1903 ◊
Page 490
PL. 100. AERODROME IN WATER, OCTOBER 7, 1903 ◊
Page 491
However, the funds which had been appropriated by the Board of
Ordnance and Fortification had been exhausted nearly two years before, and
all the expense since that time had been met from a special fund of the
Smithsonian Institution. But, owing to the heavy drains which the work had
made upon this fund, Mr. Langley felt unwilling to draw further upon it,
and since there were no other funds available from which to meet the
expenses which would be incurred by postponing the experiments until
spring, it was decided that it was practically a case of “now or never,” and
although the river was full of large blocks of floating ice several inches
thick, which added enormously to the danger involved in the experiment,
the writer decided to make the test immediately so that the long-hoped-for
success, which seemed so certain, could be finally achieved.
After considerable delay, due to the great difficulty of properly
assembling the huge wings in the strong and gusty wind, into which the
boat could not be kept directly pointed, owing both to the strong tide which
was running and to the fact that the wind itself was rapidly varying through
as great a range as ninety degrees, and after many minor delays, due to
causes too numerous to mention, the aerodrome was finally ready for test.
The wind was exceedingly gusty, varying in velocity from twelve to
eighteen miles per hour and shifting its direction most abruptly and
disconcertingly, so that the aerodrome was at one moment pointed directly
into it and at the next moment side gusts striking under the port or starboard
wings would wrench the frame severely, thus tending to twist the whole
machine from its fastenings on the launching car. After starting up the
engine and bringing it to full speed, the writer gave the signal for the
machine to be released, and it started quietly, but at a rapidly accelerated
pace, down the launching track. Exactly what happened, either just before
or just as the aerodrome reached the end of the track, it has been impossible
to determine, as all the workmen and visitors had gone to their stations on
the various auxiliary boats, except the two workmen (Mr. Reed and Mr.
McDonald) who had been retained on top of the boat to assist in the
launching. It had grown so dark that the cameras of Mr. Smillie, the official
photographer, were unable to get any impression when he used them, owing
Ordnance and Fortification had been exhausted nearly two years before, and
all the expense since that time had been met from a special fund of the
Smithsonian Institution. But, owing to the heavy drains which the work had
made upon this fund, Mr. Langley felt unwilling to draw further upon it,
and since there were no other funds available from which to meet the
expenses which would be incurred by postponing the experiments until
spring, it was decided that it was practically a case of “now or never,” and
although the river was full of large blocks of floating ice several inches
thick, which added enormously to the danger involved in the experiment,
the writer decided to make the test immediately so that the long-hoped-for
success, which seemed so certain, could be finally achieved.
After considerable delay, due to the great difficulty of properly
assembling the huge wings in the strong and gusty wind, into which the
boat could not be kept directly pointed, owing both to the strong tide which
was running and to the fact that the wind itself was rapidly varying through
as great a range as ninety degrees, and after many minor delays, due to
causes too numerous to mention, the aerodrome was finally ready for test.
The wind was exceedingly gusty, varying in velocity from twelve to
eighteen miles per hour and shifting its direction most abruptly and
disconcertingly, so that the aerodrome was at one moment pointed directly
into it and at the next moment side gusts striking under the port or starboard
wings would wrench the frame severely, thus tending to twist the whole
machine from its fastenings on the launching car. After starting up the
engine and bringing it to full speed, the writer gave the signal for the
machine to be released, and it started quietly, but at a rapidly accelerated
pace, down the launching track. Exactly what happened, either just before
or just as the aerodrome reached the end of the track, it has been impossible
to determine, as all the workmen and visitors had gone to their stations on
the various auxiliary boats, except the two workmen (Mr. Reed and Mr.
McDonald) who had been retained on top of the boat to assist in the
launching. It had grown so dark that the cameras of Mr. Smillie, the official
photographer, were unable to get any impression when he used them, owing
Page 492
to the extreme rapidity of the shutters with which they were equipped.
Fortunately, one photograph of the machine while still in the air was
secured, which shows the result of what had occurred in the launching and
before any further damage had been caused by its coming down into the
water, but the all-important question as to just what caused the accident
which did occur remains to a certain extent a mystery. [p272]
Mr. Reed, the foreman, who was qualified to observe accurately, not only
through his having worked continuously for many years on the machines,
but also from his having witnessed the numerous tests of the models, states
that from his position near the rear end of the launching track he noticed
that at a point about ten feet before the machine reached the end of the track
the Pénaud tail seemed to have dropped at the rear end in some inexplicable
way so that it was dragging against the cross-pieces of the track, and that at
the next instant, when the car reached the end of the track, he saw the
machine continue onward, but the rudder and whole rear portion of the
frame and the wings seemed to be dragging on the launching car. Mr.
McDonald, the head machinist, states that he had his attention so
concentrated on the engine, which he noticed was working perfectly and
driving the propellers at a higher rate of speed than he had ever before seen
it do, that he did not see anything happen until he saw the machine shoot
upward in the air, gradually attaining a vertical position with its bow
upward, where it was sustained for a few moments by the upward thrust of
the propellers. After a few moments, however, the strong wind, which was
blowing from twelve to eighteen miles an hour directly ahead and acting
against the wings which were now vertical, drove the machine backwards
towards the house-boat, and he saw it come down into the water on its back,
with the writer gradually righting himself in accordance with the turning of
the machine until he was finally hidden from view by the machine coming
down on top of him. The witnesses on the tug-boats seem not to have been
able to perceive exactly what occurred. All unite in stating that something
seemed to happen to the machine just a few feet before the launching car
reached the end of the track, but what it was they could not say. Everyone
who saw the accident and who was sufficiently familiar with the
Fortunately, one photograph of the machine while still in the air was
secured, which shows the result of what had occurred in the launching and
before any further damage had been caused by its coming down into the
water, but the all-important question as to just what caused the accident
which did occur remains to a certain extent a mystery. [p272]
Mr. Reed, the foreman, who was qualified to observe accurately, not only
through his having worked continuously for many years on the machines,
but also from his having witnessed the numerous tests of the models, states
that from his position near the rear end of the launching track he noticed
that at a point about ten feet before the machine reached the end of the track
the Pénaud tail seemed to have dropped at the rear end in some inexplicable
way so that it was dragging against the cross-pieces of the track, and that at
the next instant, when the car reached the end of the track, he saw the
machine continue onward, but the rudder and whole rear portion of the
frame and the wings seemed to be dragging on the launching car. Mr.
McDonald, the head machinist, states that he had his attention so
concentrated on the engine, which he noticed was working perfectly and
driving the propellers at a higher rate of speed than he had ever before seen
it do, that he did not see anything happen until he saw the machine shoot
upward in the air, gradually attaining a vertical position with its bow
upward, where it was sustained for a few moments by the upward thrust of
the propellers. After a few moments, however, the strong wind, which was
blowing from twelve to eighteen miles an hour directly ahead and acting
against the wings which were now vertical, drove the machine backwards
towards the house-boat, and he saw it come down into the water on its back,
with the writer gradually righting himself in accordance with the turning of
the machine until he was finally hidden from view by the machine coming
down on top of him. The witnesses on the tug-boats seem not to have been
able to perceive exactly what occurred. All unite in stating that something
seemed to happen to the machine just a few feet before the launching car
reached the end of the track, but what it was they could not say. Everyone
who saw the accident and who was sufficiently familiar with the
Page 493
construction of the machine to be able intuitively to form an idea as to just
what was taking place was so very close to the machine that when the
accident happened everything seemed to merge into one vision, which was
that of the whole rear of the wings and rudder being completely destroyed
as the machine shot upward at a rapidly increasing angle until it reached the
vertical position previously mentioned.
The writer can only say that from his position in the front end of the
machine, where he was facing forward and where his main attention was
directed towards insuring that the engine was performing at its best, he was
unable to see anything that occurred at the rear of the machine, but that just
before the machine was freed from the launching car he felt an extreme
swaying motion immediately followed by a tremendous jerk which caused
the machine to quiver all over, and almost instantly he found the machine
dashing ahead with its bow rising at a very rapid rate, and that he, therefore,
swung the wheel which controls the Pénaud tail to its extreme downward
limit of motion. Finding that [p273] this had absolutely no effect, and that by
this time the machine had passed its vertical position and was beginning to
fall backwards, he swung himself around on his arms, from which he
supported himself, so that in striking the water with the machine on top of
him he would strike feet foremost. The next few moments were for him
most intense, for he found himself under the water with the machine on top
of him, and with his cork-lined canvas jacket so caught in the fittings of the
framework that he could not dive downward, while the floor of the aviator’s
car, which was pressing against his head, prevented him from coming
upward. His one thought was that if he was to get out alive he would have
to do so immediately, as the pressure of the water on his lungs was
beginning to make itself seriously felt. Exerting all of the strength he could
muster, he succeeded in ripping the jacket entirely in two and thus freeing
himself from the fastenings which had accidentally held him, he dived
under the machine and swam under the water for some distance until he
thought he was out from under the machine. Upon rising to the surface his
head came in contact with a block of ice, which necessitated another dive to
get free of the ice. Upon coming to the surface of the water he noticed Mr.
what was taking place was so very close to the machine that when the
accident happened everything seemed to merge into one vision, which was
that of the whole rear of the wings and rudder being completely destroyed
as the machine shot upward at a rapidly increasing angle until it reached the
vertical position previously mentioned.
The writer can only say that from his position in the front end of the
machine, where he was facing forward and where his main attention was
directed towards insuring that the engine was performing at its best, he was
unable to see anything that occurred at the rear of the machine, but that just
before the machine was freed from the launching car he felt an extreme
swaying motion immediately followed by a tremendous jerk which caused
the machine to quiver all over, and almost instantly he found the machine
dashing ahead with its bow rising at a very rapid rate, and that he, therefore,
swung the wheel which controls the Pénaud tail to its extreme downward
limit of motion. Finding that [p273] this had absolutely no effect, and that by
this time the machine had passed its vertical position and was beginning to
fall backwards, he swung himself around on his arms, from which he
supported himself, so that in striking the water with the machine on top of
him he would strike feet foremost. The next few moments were for him
most intense, for he found himself under the water with the machine on top
of him, and with his cork-lined canvas jacket so caught in the fittings of the
framework that he could not dive downward, while the floor of the aviator’s
car, which was pressing against his head, prevented him from coming
upward. His one thought was that if he was to get out alive he would have
to do so immediately, as the pressure of the water on his lungs was
beginning to make itself seriously felt. Exerting all of the strength he could
muster, he succeeded in ripping the jacket entirely in two and thus freeing
himself from the fastenings which had accidentally held him, he dived
under the machine and swam under the water for some distance until he
thought he was out from under the machine. Upon rising to the surface his
head came in contact with a block of ice, which necessitated another dive to
get free of the ice. Upon coming to the surface of the water he noticed Mr.
Page 494
Hewitt, one of the workmen, just about to plunge in; before he could call
out to indicate he was safe, Mr. Hewitt had heroically plunged in with the
expectation of diving under the machine where he believed the writer to be
entangled. Finding the house-boat was being rapidly shoved upon him,
imperilling the life of both himself and Mr. Hewitt, besides the safety of the
aerodrome, the writer gave orders that the tug-boat reverse and tow the
house-boat away. Then, with the assistance of a row-boat, he reached the
house-boat, where willing hands drew him on board and assisted him into
dryer and warmer clothing.
Meanwhile, it had become quite dark, and when the writer went outside
to see about the aerodrome he found that the men on the tug-boat, in their
zeal to render assistance, had fastened a rope to the rear end of the machine,
at the same time pulling it in the direction in which the front end was
pointed, and through their ignorance had forced it down into the muddy
bottom of the river and broken the main framework completely in two, thus
rendering it absolutely impossible with the facilities at hand to remove it
from the water to the interior of the boat. It was finally necessary to tie the
wrecked machine to the stern of the house-boat and have the boat towed to
its dock where the mast and boom were assembled and the wrecked
machine hoisted from the water. This was finally accomplished about
midnight, when the workmen, who had been working at a fever heat all day,
were glad to close up the work for the day, which had proved so
unfortunate.
out to indicate he was safe, Mr. Hewitt had heroically plunged in with the
expectation of diving under the machine where he believed the writer to be
entangled. Finding the house-boat was being rapidly shoved upon him,
imperilling the life of both himself and Mr. Hewitt, besides the safety of the
aerodrome, the writer gave orders that the tug-boat reverse and tow the
house-boat away. Then, with the assistance of a row-boat, he reached the
house-boat, where willing hands drew him on board and assisted him into
dryer and warmer clothing.
Meanwhile, it had become quite dark, and when the writer went outside
to see about the aerodrome he found that the men on the tug-boat, in their
zeal to render assistance, had fastened a rope to the rear end of the machine,
at the same time pulling it in the direction in which the front end was
pointed, and through their ignorance had forced it down into the muddy
bottom of the river and broken the main framework completely in two, thus
rendering it absolutely impossible with the facilities at hand to remove it
from the water to the interior of the boat. It was finally necessary to tie the
wrecked machine to the stern of the house-boat and have the boat towed to
its dock where the mast and boom were assembled and the wrecked
machine hoisted from the water. This was finally accomplished about
midnight, when the workmen, who had been working at a fever heat all day,
were glad to close up the work for the day, which had proved so
unfortunate.
Page 495
PL. 101. ATTEMPTED LAUNCHING OF AERODROME, DECEMBER 8, 1903 ◊
ENLARGEMENT OF PHOTOGRAPH BY THE WASHINGTON STAR
As has already been remarked, darkness had descended to such an extent
that the light was not strong enough to give photographs with the very rapid
ENLARGEMENT OF PHOTOGRAPH BY THE WASHINGTON STAR
As has already been remarked, darkness had descended to such an extent
that the light was not strong enough to give photographs with the very rapid
Page 496
shutters with which Mr. Smillie had his cameras equipped, and that,
therefore, [p274] incontrovertible evidence, which the instantaneous
photographs had given as to just what had occurred to the machine in the
accident of October 7, was in this case unfortunately lacking. It was at first
thought that no photographs had been obtained while the machine was
actually in the air, but it was later found that by some rare fortune the
photographer for The Washington Star had secured a photograph, which,
while small, showed very distinctly some decidedly interesting facts. An
enlargement of this photograph is shown in Plate 101, by the kind
permission of The Washington Star. Referring to this photograph, it will be
seen that at the moment it was taken the machine was practically vertical in
the air, and it confirms the testimony of the eye witnesses, and also the
writer’s impression that the machine was maintained in a vertical position
for several moments by the upward thrust of the propellers. It will also be
seen that the Pénaud tail has been completely demolished and is hanging as
a limp roll of cloth, which the strong wind has deflected backwards towards
the house-boat, the port rear wing has broken its main ribs, both where they
are attached to the main frame and also about midway the length of the
wing, the outer end being partially folded towards the frame. The starboard
rear wing has also broken both of its main ribs at the point where they are
joined to the frame, and they have also broken at a point about one-third
their length from the frame, the outer end being likewise folded towards the
frame. By a still more careful inspection, it will also be seen that the port
front wing is apparently uninjured, while the starboard front wing has
broken the middle main rib at a point between the sixth and seventh cross-
ribs, and while it cannot be distinctly seen at first that the front main rib has
also broken at the same point very careful inspection will show that this is
the case, as the sixth and seventh ribs, showing as faintly darker lines in the
photograph, are seen to be displaced, so that they are together and actually
crossing each other. It will furthermore be seen that both front wings have
been pressed upward by the wind until their tips near the inner ends are in
contact with the cross-frame. This could not have happened unless the front
guy-post had given away either by bending or breaking. The fact that it has
therefore, [p274] incontrovertible evidence, which the instantaneous
photographs had given as to just what had occurred to the machine in the
accident of October 7, was in this case unfortunately lacking. It was at first
thought that no photographs had been obtained while the machine was
actually in the air, but it was later found that by some rare fortune the
photographer for The Washington Star had secured a photograph, which,
while small, showed very distinctly some decidedly interesting facts. An
enlargement of this photograph is shown in Plate 101, by the kind
permission of The Washington Star. Referring to this photograph, it will be
seen that at the moment it was taken the machine was practically vertical in
the air, and it confirms the testimony of the eye witnesses, and also the
writer’s impression that the machine was maintained in a vertical position
for several moments by the upward thrust of the propellers. It will also be
seen that the Pénaud tail has been completely demolished and is hanging as
a limp roll of cloth, which the strong wind has deflected backwards towards
the house-boat, the port rear wing has broken its main ribs, both where they
are attached to the main frame and also about midway the length of the
wing, the outer end being partially folded towards the frame. The starboard
rear wing has also broken both of its main ribs at the point where they are
joined to the frame, and they have also broken at a point about one-third
their length from the frame, the outer end being likewise folded towards the
frame. By a still more careful inspection, it will also be seen that the port
front wing is apparently uninjured, while the starboard front wing has
broken the middle main rib at a point between the sixth and seventh cross-
ribs, and while it cannot be distinctly seen at first that the front main rib has
also broken at the same point very careful inspection will show that this is
the case, as the sixth and seventh ribs, showing as faintly darker lines in the
photograph, are seen to be displaced, so that they are together and actually
crossing each other. It will furthermore be seen that both front wings have
been pressed upward by the wind until their tips near the inner ends are in
contact with the cross-frame. This could not have happened unless the front
guy-post had given away either by bending or breaking. The fact that it has
Page 497
given way is further evidenced by a more careful examination of the
extreme front end of the machine, where it will be seen that the bowsprit
and the curved tubes which form the extreme end of the steel frame have
been bent from a straight line with reference to the main frame. This
bending of the bowsprit and the curved tubes could be produced only by the
front guy-post coming in contact with some obstruction on the launching
car as the machine left it. It is known very certainly that the rear end of the
machine came in contact with the launching car, as the car itself shows a
very deep gash in the wooden cross-piece at its center, which was produced
by the port-bearing point at the rear striking it. As this bearing point was
elevated five feet above the cross-piece of the launching car, and was also
six feet six inches to [p275] the rear of the point where the wood is torn, this
rear-bearing point must have travelled downward at an angle of
approximately thirty-eight degrees in order for the bearing point to strike
the car at this point. As the lower end of the rear guy-post was only eighteen
inches above the cross-piece of the launching car, it, of course, would be
broken before the bearing point could descend so much. As has been
previously stated, Mr. Reed, who was at the rear of the launching track,
states very positively that the rudder was dragging on the track at least ten
feet before the launching car reached the front end of the track where the
machine was actually launched. There are several ways in which the rudder
could have gotten down on the track, but positive information is lacking. If
it was dragging on the track, as Mr. Reed states (and from his extended
experience and rather acute powers of observation I should place great
credence in his report), the subsequent demolition of the guy-posts
succeeded by the destruction of the rear wings and serious injury of the
front ones is easily explained. If the dropping of the rudder on the track
occurred from the breaking of the upper rudder post, over which the upper
control wire passed, the lower vertical surface would first come in contact
with the track, and the destruction of this part would certainly occasion
subsequent destruction of the horizontal and upper vertical surfaces of the
rudder, leaving the central rib of the rudder still attached to the frame, and
upon the machine being released from the car a few moments later this
extreme front end of the machine, where it will be seen that the bowsprit
and the curved tubes which form the extreme end of the steel frame have
been bent from a straight line with reference to the main frame. This
bending of the bowsprit and the curved tubes could be produced only by the
front guy-post coming in contact with some obstruction on the launching
car as the machine left it. It is known very certainly that the rear end of the
machine came in contact with the launching car, as the car itself shows a
very deep gash in the wooden cross-piece at its center, which was produced
by the port-bearing point at the rear striking it. As this bearing point was
elevated five feet above the cross-piece of the launching car, and was also
six feet six inches to [p275] the rear of the point where the wood is torn, this
rear-bearing point must have travelled downward at an angle of
approximately thirty-eight degrees in order for the bearing point to strike
the car at this point. As the lower end of the rear guy-post was only eighteen
inches above the cross-piece of the launching car, it, of course, would be
broken before the bearing point could descend so much. As has been
previously stated, Mr. Reed, who was at the rear of the launching track,
states very positively that the rudder was dragging on the track at least ten
feet before the launching car reached the front end of the track where the
machine was actually launched. There are several ways in which the rudder
could have gotten down on the track, but positive information is lacking. If
it was dragging on the track, as Mr. Reed states (and from his extended
experience and rather acute powers of observation I should place great
credence in his report), the subsequent demolition of the guy-posts
succeeded by the destruction of the rear wings and serious injury of the
front ones is easily explained. If the dropping of the rudder on the track
occurred from the breaking of the upper rudder post, over which the upper
control wire passed, the lower vertical surface would first come in contact
with the track, and the destruction of this part would certainly occasion
subsequent destruction of the horizontal and upper vertical surfaces of the
rudder, leaving the central rib of the rudder still attached to the frame, and
upon the machine being released from the car a few moments later this
Page 498
destroyed rudder would easily catch in the launching car and pull the
aerodrome down on it, and thus cause the destruction of the guy-posts,
wings, and so forth. If the dropping of the rudder was caused primarily by
its main rib breaking loose from its connection with the frame, the rudder
would still be dragged along behind the machine by the wire cords through
which it was operated, and the subsequent launching of the machine would
still give the rudder every chance to catch in the launching car and drag the
machine down on it.
It can therefore be said that, while positive information is lacking, there
is very strong evidence that the accident in the launching was due to the
rudder becoming entangled with the launching track owing to the breakage
of some part of the mechanism by which it was connected to the main
frame.
It is of importance to note that the photograph furnishes incontrovertible
evidence that the main frame of the machine was in no way injured, except
for the slight bending of the forward curved extension, and that, therefore,
the accident was in no way due to the weakness of the frame. The main
frame was not even injured by the machine coming down in the water on its
back, and the later damage was entirely caused by the combination of the
ignorance of the tug-boatmen and the darkness in which they were working,
when they attempted to tow it to the rear of the house-boat so that it could
be removed from the water. [p276]
On the day following the trial a very careful inspection was made in the
hope of obtaining some more definite information as to just what caused the
accident, but the serious injury to the machine caused by the tug-boatmen
breaking it in the water had so greatly tangled things up that it was
impossible to tell anything about it. The workmen were immediately put to
work removing fittings from the broken wings, rudder, etc., and
dismounting the engine, which was immediately reassembled on its testing
frame and found to be absolutely uninjured. The transverse frame of the
machine was comparatively uninjured, the damage done by the men on the
tug-boat being the breaking of the machine in two at a point just back of the
cross-frame, together with the consequent destruction of the bearing points,
aerodrome down on it, and thus cause the destruction of the guy-posts,
wings, and so forth. If the dropping of the rudder was caused primarily by
its main rib breaking loose from its connection with the frame, the rudder
would still be dragged along behind the machine by the wire cords through
which it was operated, and the subsequent launching of the machine would
still give the rudder every chance to catch in the launching car and drag the
machine down on it.
It can therefore be said that, while positive information is lacking, there
is very strong evidence that the accident in the launching was due to the
rudder becoming entangled with the launching track owing to the breakage
of some part of the mechanism by which it was connected to the main
frame.
It is of importance to note that the photograph furnishes incontrovertible
evidence that the main frame of the machine was in no way injured, except
for the slight bending of the forward curved extension, and that, therefore,
the accident was in no way due to the weakness of the frame. The main
frame was not even injured by the machine coming down in the water on its
back, and the later damage was entirely caused by the combination of the
ignorance of the tug-boatmen and the darkness in which they were working,
when they attempted to tow it to the rear of the house-boat so that it could
be removed from the water. [p276]
On the day following the trial a very careful inspection was made in the
hope of obtaining some more definite information as to just what caused the
accident, but the serious injury to the machine caused by the tug-boatmen
breaking it in the water had so greatly tangled things up that it was
impossible to tell anything about it. The workmen were immediately put to
work removing fittings from the broken wings, rudder, etc., and
dismounting the engine, which was immediately reassembled on its testing
frame and found to be absolutely uninjured. The transverse frame of the
machine was comparatively uninjured, the damage done by the men on the
tug-boat being the breaking of the machine in two at a point just back of the
cross-frame, together with the consequent destruction of the bearing points,
Page 499
“trestle,” and certain fittings by which the main guy-wires were attached to
the main tubes and pyramids.
The situation which now existed was most distressing and disheartening.
Mr. Langley felt that he could not approve of further expenditures from any
Smithsonian fund, and the Board of Ordnance and Fortification of the War
Department having been severely criticised on the floors of Congress for its
original allotment for the work, deemed it inexpedient to incur a possible
curtailment of the funds annually placed at its disposal for general
experimental work through a manifestation of continued interest in the
flying machine.
As has already been stated, representatives from the Board of Ordnance
and Fortification of the War Department were present at both tests of the
large aerodrome; on October 7 Major Montgomery M. Macomb and Mr. G.
H. Powell, and on December 7 General W. F. Randolph accompanied by
Major Macomb and Mr. Powell, represented the War Department, and Dr. F.
S. Nash, at that time Contract Surgeon, U. S. A., was officially present at
both trials to render medical assistance should it be needed.
By permission of the War Department, the official report of the tests
submitted by Major Macomb to the Board of Ordnance and Fortification is
here made public:
Enc. 1st to 3d end’t, BOF 6191.
REPORT
Experiments with working models which were concluded August 8 last having proved the
principles and calculations on which the design of the Langley aerodrome was based to be correct,
the next step was to apply these principles to the construction of a machine of sufficient size and
power to permit the carrying of a man, who could control the motive power and guide its flight,
thus pointing the way to attaining the final goal of producing a machine capable of such extensive
and precise aerial flight, under normal atmospheric conditions, as to prove of military or
commercial utility.
Mr. C. M. Manly, working under Prof. Langley, had, by the summer of 1903, succeeded in
completing an engine-driven machine which under favorable [p277] atmospheric conditions was
expected to carry a man for any time up to half an hour, and to be capable of having its flight
directed and controlled by him.
The supporting surface of the wings was ample, and experiment showed the engine capable of
supplying more than the necessary motive power.
Owing to the necessity of lightness, the weight of the various elements had to be kept at a
minimum, and the factor of safety in construction was therefore exceedingly small, so that the
machine as a whole was delicate and frail and incapable of sustaining any unusual strain. This
the main tubes and pyramids.
The situation which now existed was most distressing and disheartening.
Mr. Langley felt that he could not approve of further expenditures from any
Smithsonian fund, and the Board of Ordnance and Fortification of the War
Department having been severely criticised on the floors of Congress for its
original allotment for the work, deemed it inexpedient to incur a possible
curtailment of the funds annually placed at its disposal for general
experimental work through a manifestation of continued interest in the
flying machine.
As has already been stated, representatives from the Board of Ordnance
and Fortification of the War Department were present at both tests of the
large aerodrome; on October 7 Major Montgomery M. Macomb and Mr. G.
H. Powell, and on December 7 General W. F. Randolph accompanied by
Major Macomb and Mr. Powell, represented the War Department, and Dr. F.
S. Nash, at that time Contract Surgeon, U. S. A., was officially present at
both trials to render medical assistance should it be needed.
By permission of the War Department, the official report of the tests
submitted by Major Macomb to the Board of Ordnance and Fortification is
here made public:
Enc. 1st to 3d end’t, BOF 6191.
REPORT
Experiments with working models which were concluded August 8 last having proved the
principles and calculations on which the design of the Langley aerodrome was based to be correct,
the next step was to apply these principles to the construction of a machine of sufficient size and
power to permit the carrying of a man, who could control the motive power and guide its flight,
thus pointing the way to attaining the final goal of producing a machine capable of such extensive
and precise aerial flight, under normal atmospheric conditions, as to prove of military or
commercial utility.
Mr. C. M. Manly, working under Prof. Langley, had, by the summer of 1903, succeeded in
completing an engine-driven machine which under favorable [p277] atmospheric conditions was
expected to carry a man for any time up to half an hour, and to be capable of having its flight
directed and controlled by him.
The supporting surface of the wings was ample, and experiment showed the engine capable of
supplying more than the necessary motive power.
Owing to the necessity of lightness, the weight of the various elements had to be kept at a
minimum, and the factor of safety in construction was therefore exceedingly small, so that the
machine as a whole was delicate and frail and incapable of sustaining any unusual strain. This
Page 500
defect was to be corrected in later models by utilizing data gathered in future experiments under
varied conditions.
One of the most remarkable results attained was the production of a gasoline engine furnishing
over fifty continuous horse-power for a weight of one hundred and twenty pounds.
The aerodrome, as completed and prepared for test, is briefly described by Prof. Langley as
“built of steel, weighing complete about seven hundred and thirty pounds, supported by one
thousand and forty feet of sustaining surface, having two propellers driven by a gas engine
developing continuously over fifty brake horse-power.”
The appearance of the machine prepared for flight was exceedingly light and graceful, giving an
impression to all observers of being capable of successful flight.
On October 7 last everything was in readiness, and I witnessed the attempted trial on that day at
Widewater, Va., on the Potomac. The engine worked well and the machine was launched at about
12.15 p. m. The trial was unsuccessful because the front guy-post caught in its support on the
launching car and was not released in time to give free flight, as was intended, but on the contrary,
caused the front of the machine to be dragged downward, bending the guy-post and making the
machine plunge into the water about 50 yards in front of the house-boat. The machine was
subsequently recovered and brought back to the house-boat. The engine was uninjured and the
frame only slightly damaged, but the four wings and rudder were practically destroyed by the first
plunge and subsequent towing back to the house-boat. This accident necessitated the removal of
the house-boat to Washington for the more convenient repair of damages.
On December 8 last, between 4 and 5 p. m., another attempt at a trial was made, this time at the
junction of the Anacostia with the Potomac, just below Washington Barracks.
On this occasion General Randolph and myself represented the Board of Ordnance and
Fortification. The launching car was released at 4.45 p. m., being pointed up the Anacostia towards
the Navy Yard. My position was on the tug Bartholdi about 150 feet from and at right angles to the
direction of proposed flight. The car was set in motion and the propellers revolved rapidly, the
engine working perfectly, but there was something wrong with the launching. The rear guy-post
seemed to drag, bringing the rudder down on the launching ways, and a crashing, rending sound,
followed by the collapse of the rear wings, showed that the machine had been wrecked in the
launching, just how, it was impossible for me to see. The fact remains that the rear wings and
rudder were wrecked before the machine was free of the ways. Their collapse deprived the
machine of its support in the rear, and it consequently reared up in front under the action of the
motor, assumed a vertical position, and then toppled over to the rear, falling into the water a few
feet in front of the boat. [p278]
Mr. Manly was pulled out of the wreck uninjured and the wrecked machine was subsequently
placed upon the house-boat, and the whole brought back to Washington.
From what has been said it will be seen that these unfortunate accidents have prevented any test
of the apparatus in free flight, and the claim that an engine-driven, man-carrying aerodrome has
been constructed lacks the proof which actual flight alone can give.
Having reached the present stage of advancement in its development, it would seem highly
desirable, before laying down the investigation, to obtain conclusive proof of the possibility of free
flight, not only because there are excellent reasons to hope for success, but because it marks the
end of a definite step toward the attainment of the final goal.
Just what further procedure is necessary to secure successful flight with the large aerodrome has
not yet been decided upon. Professor Langley is understood to have this subject under advisement,
and will doubtless inform the Board of his final conclusions as soon as practicable.
varied conditions.
One of the most remarkable results attained was the production of a gasoline engine furnishing
over fifty continuous horse-power for a weight of one hundred and twenty pounds.
The aerodrome, as completed and prepared for test, is briefly described by Prof. Langley as
“built of steel, weighing complete about seven hundred and thirty pounds, supported by one
thousand and forty feet of sustaining surface, having two propellers driven by a gas engine
developing continuously over fifty brake horse-power.”
The appearance of the machine prepared for flight was exceedingly light and graceful, giving an
impression to all observers of being capable of successful flight.
On October 7 last everything was in readiness, and I witnessed the attempted trial on that day at
Widewater, Va., on the Potomac. The engine worked well and the machine was launched at about
12.15 p. m. The trial was unsuccessful because the front guy-post caught in its support on the
launching car and was not released in time to give free flight, as was intended, but on the contrary,
caused the front of the machine to be dragged downward, bending the guy-post and making the
machine plunge into the water about 50 yards in front of the house-boat. The machine was
subsequently recovered and brought back to the house-boat. The engine was uninjured and the
frame only slightly damaged, but the four wings and rudder were practically destroyed by the first
plunge and subsequent towing back to the house-boat. This accident necessitated the removal of
the house-boat to Washington for the more convenient repair of damages.
On December 8 last, between 4 and 5 p. m., another attempt at a trial was made, this time at the
junction of the Anacostia with the Potomac, just below Washington Barracks.
On this occasion General Randolph and myself represented the Board of Ordnance and
Fortification. The launching car was released at 4.45 p. m., being pointed up the Anacostia towards
the Navy Yard. My position was on the tug Bartholdi about 150 feet from and at right angles to the
direction of proposed flight. The car was set in motion and the propellers revolved rapidly, the
engine working perfectly, but there was something wrong with the launching. The rear guy-post
seemed to drag, bringing the rudder down on the launching ways, and a crashing, rending sound,
followed by the collapse of the rear wings, showed that the machine had been wrecked in the
launching, just how, it was impossible for me to see. The fact remains that the rear wings and
rudder were wrecked before the machine was free of the ways. Their collapse deprived the
machine of its support in the rear, and it consequently reared up in front under the action of the
motor, assumed a vertical position, and then toppled over to the rear, falling into the water a few
feet in front of the boat. [p278]
Mr. Manly was pulled out of the wreck uninjured and the wrecked machine was subsequently
placed upon the house-boat, and the whole brought back to Washington.
From what has been said it will be seen that these unfortunate accidents have prevented any test
of the apparatus in free flight, and the claim that an engine-driven, man-carrying aerodrome has
been constructed lacks the proof which actual flight alone can give.
Having reached the present stage of advancement in its development, it would seem highly
desirable, before laying down the investigation, to obtain conclusive proof of the possibility of free
flight, not only because there are excellent reasons to hope for success, but because it marks the
end of a definite step toward the attainment of the final goal.
Just what further procedure is necessary to secure successful flight with the large aerodrome has
not yet been decided upon. Professor Langley is understood to have this subject under advisement,
and will doubtless inform the Board of his final conclusions as soon as practicable.
Page 501
In the meantime, to avoid any possible misunderstanding, it should be stated that even after a
successful test of the present great aerodrome, designed to carry a man, we are still far from the
ultimate goal, and it would seem as if years of constant work and study by experts, together with
the expenditure of thousands of dollars, would still be necessary before we can hope to produce an
apparatus of practical utility on these lines.
M. M. MACOMB,
WASHINGTON, January 6, 1904. Major Artillery Corps.
The attitude of the Board of Ordnance and Fortification, with reference to
rendering further financial assistance to the work, is clearly shown by the
following extract from the official report of the Board on October 6, 1904,
to the Secretary of War:
THE LANGLEY AERODROME
Early in the year 1898 a board composed of officers of the Army and Navy was appointed to
examine the models and principles of the aerodrome devised by Dr. S. P. Langley, Secretary of the
Smithsonian Institution, and to report whether or not, in its opinion, a large machine of this design
could be built, and, if so, whether it would be of practical value.
The report of this board was referred to the Board of Ordnance and Fortification for action, and
Doctor Langley was invited to appear before the Board and further explain the proposed
construction.
In view of the great utility of such a device, if a practical success, the Board, on November 9,
1898, made an allotment of $25,000 for the construction, development, and test of an aerodrome to
be made under the direction of Doctor Langley, with the understanding that an additional allotment
of the same amount would be made later. On December 18, 1899, the additional allotment of
$25,000 was made.
The construction of the machine was delayed by Doctor Langley’s inability to procure a suitable
motor, which he was finally obliged to design. The aerodrome was completed about July 15, 1903,
and preparations for its test were made at a point in the Potomac River about 40 miles below
Washington. [p279]
Preliminary arrangements having been completed and tests made of a quarter-size model, the
first attempt at actual flight with the man-carrying aerodrome was made on October 7, 1903.
On this occasion there were present on behalf of the Board, Major M. M. Macomb, Artillery
Corps, and Mr. G. H. Powell, clerk of the Board.
Major Macomb in his report to the Board stated that—
“The trial was unsuccessful because the front guy-post caught in its support on the launching
car and was not released in time to give free flight, as was intended, but on the contrary, caused
the front of the machine to be dragged downward, bending the guy-post and making the
machine plunge into the water about 50 yards in front of the house-boat.”
This accident necessitated the removal of the house-boat to Washington for the more convenient
repair of damages. The repairs having been completed, on December 8, 1903, another attempt at a
trial was made, this time at the junction of the Anacostia and the Potomac Rivers. General W. F.
Randolph and Major Macomb, members of the Board, and Mr. Powell, were present. Major
Macomb reported as follows:
“The launching car was released at 4.45 p. m. . . . The car was set in motion and the propellers
revolved rapidly, the engine working perfectly, but there was something wrong with the
successful test of the present great aerodrome, designed to carry a man, we are still far from the
ultimate goal, and it would seem as if years of constant work and study by experts, together with
the expenditure of thousands of dollars, would still be necessary before we can hope to produce an
apparatus of practical utility on these lines.
M. M. MACOMB,
WASHINGTON, January 6, 1904. Major Artillery Corps.
The attitude of the Board of Ordnance and Fortification, with reference to
rendering further financial assistance to the work, is clearly shown by the
following extract from the official report of the Board on October 6, 1904,
to the Secretary of War:
THE LANGLEY AERODROME
Early in the year 1898 a board composed of officers of the Army and Navy was appointed to
examine the models and principles of the aerodrome devised by Dr. S. P. Langley, Secretary of the
Smithsonian Institution, and to report whether or not, in its opinion, a large machine of this design
could be built, and, if so, whether it would be of practical value.
The report of this board was referred to the Board of Ordnance and Fortification for action, and
Doctor Langley was invited to appear before the Board and further explain the proposed
construction.
In view of the great utility of such a device, if a practical success, the Board, on November 9,
1898, made an allotment of $25,000 for the construction, development, and test of an aerodrome to
be made under the direction of Doctor Langley, with the understanding that an additional allotment
of the same amount would be made later. On December 18, 1899, the additional allotment of
$25,000 was made.
The construction of the machine was delayed by Doctor Langley’s inability to procure a suitable
motor, which he was finally obliged to design. The aerodrome was completed about July 15, 1903,
and preparations for its test were made at a point in the Potomac River about 40 miles below
Washington. [p279]
Preliminary arrangements having been completed and tests made of a quarter-size model, the
first attempt at actual flight with the man-carrying aerodrome was made on October 7, 1903.
On this occasion there were present on behalf of the Board, Major M. M. Macomb, Artillery
Corps, and Mr. G. H. Powell, clerk of the Board.
Major Macomb in his report to the Board stated that—
“The trial was unsuccessful because the front guy-post caught in its support on the launching
car and was not released in time to give free flight, as was intended, but on the contrary, caused
the front of the machine to be dragged downward, bending the guy-post and making the
machine plunge into the water about 50 yards in front of the house-boat.”
This accident necessitated the removal of the house-boat to Washington for the more convenient
repair of damages. The repairs having been completed, on December 8, 1903, another attempt at a
trial was made, this time at the junction of the Anacostia and the Potomac Rivers. General W. F.
Randolph and Major Macomb, members of the Board, and Mr. Powell, were present. Major
Macomb reported as follows:
“The launching car was released at 4.45 p. m. . . . The car was set in motion and the propellers
revolved rapidly, the engine working perfectly, but there was something wrong with the
Page 502
launching. The rear guy-post seemed to drag, bringing the rudder down on the launching ways,
and a crashing, rending sound, followed by the collapse of the rear wings, showed that the
machine had been wrecked in the launching, just how, it was impossible for me to see.”
March 3, 1904, the Board stated that it was not “prepared to make an additional allotment at this
time for continuing the work,” whereupon Doctor Langley requested that arrangements be made
for a distribution of the aerodrome material procured jointly from funds allotted by the Board and
by the Smithsonian Institution. Doctor Langley was informed that all of the material would be left
in his possession and available for any future work that he might be able to carry on in connection
with the problem of mechanical flight.
That this refusal of the Board of Ordnance and Fortification to render
further assistance to the work was due to the fear that such action would
result in a curtailment of their appropriation by Congress is clearly shown
by the following extract from the official report of the Board on November
14, 1908, to the Secretary of War:
AERIAL NAVIGATION
For a number of years the Board has been interested in the subject of aerial navigation, and as
long ago as 1898 made allotments to carry on experiments with a machine of the heavier-than-air
type, under the direction of the late Dr. S. P. Langley, Secretary of the Smithsonian Institution, who
had made exhaustive experiments in aerodynamics,48 and who had demonstrated the practicability
of mechanical flight by the successful operation of engine-driven models.
The many problems and mechanical difficulties met with in the development of the full-size
machine have been set forth in the various published statements49 [p280] of Doctor Langley, and
the unsuccessful outcome of the experiments is too well known to require reiteration. It may be
said, however, that at the time of the trials the Board was of the opinion that the failure of the
aerodrome to successfully operate was in no manner due to the machine itself, but solely to
accidents in the launching apparatus, which caused the wreck of the aerodrome before it was in
free flight.
Doctor Langley considered it desirable to continue the experiments, but the Board deemed it
advisable, largely in view of the adverse opinions expressed in Congress and elsewhere, to suspend
operations in this direction.
These adverse opinions expressed in Congress were wholly due to the
bitter criticism by the newspapers, whose hostility was engendered by Mr.
Langley’s refusal to admit their representatives to the shops and house-boat
where the work was in progress. Mr. Langley had at all times tried to make
his position in the matter clear to the newspapers, but, on August 19, 1903,
at the time of one of his visits to the experimental station near Widewater,
Va., he found the newspaper representatives so persistent in their
misrepresentations of his reasons for excluding them that he gave out the
following statement, which was published at that time:
and a crashing, rending sound, followed by the collapse of the rear wings, showed that the
machine had been wrecked in the launching, just how, it was impossible for me to see.”
March 3, 1904, the Board stated that it was not “prepared to make an additional allotment at this
time for continuing the work,” whereupon Doctor Langley requested that arrangements be made
for a distribution of the aerodrome material procured jointly from funds allotted by the Board and
by the Smithsonian Institution. Doctor Langley was informed that all of the material would be left
in his possession and available for any future work that he might be able to carry on in connection
with the problem of mechanical flight.
That this refusal of the Board of Ordnance and Fortification to render
further assistance to the work was due to the fear that such action would
result in a curtailment of their appropriation by Congress is clearly shown
by the following extract from the official report of the Board on November
14, 1908, to the Secretary of War:
AERIAL NAVIGATION
For a number of years the Board has been interested in the subject of aerial navigation, and as
long ago as 1898 made allotments to carry on experiments with a machine of the heavier-than-air
type, under the direction of the late Dr. S. P. Langley, Secretary of the Smithsonian Institution, who
had made exhaustive experiments in aerodynamics,48 and who had demonstrated the practicability
of mechanical flight by the successful operation of engine-driven models.
The many problems and mechanical difficulties met with in the development of the full-size
machine have been set forth in the various published statements49 [p280] of Doctor Langley, and
the unsuccessful outcome of the experiments is too well known to require reiteration. It may be
said, however, that at the time of the trials the Board was of the opinion that the failure of the
aerodrome to successfully operate was in no manner due to the machine itself, but solely to
accidents in the launching apparatus, which caused the wreck of the aerodrome before it was in
free flight.
Doctor Langley considered it desirable to continue the experiments, but the Board deemed it
advisable, largely in view of the adverse opinions expressed in Congress and elsewhere, to suspend
operations in this direction.
These adverse opinions expressed in Congress were wholly due to the
bitter criticism by the newspapers, whose hostility was engendered by Mr.
Langley’s refusal to admit their representatives to the shops and house-boat
where the work was in progress. Mr. Langley had at all times tried to make
his position in the matter clear to the newspapers, but, on August 19, 1903,
at the time of one of his visits to the experimental station near Widewater,
Va., he found the newspaper representatives so persistent in their
misrepresentations of his reasons for excluding them that he gave out the
following statement, which was published at that time:
Page 503
SMITHSONIAN INSTITUTION, WASHINGTON, D. C.,
August 19, 1903.
TO THE PRESS: The present experiments being made in mechanical flight have been carried
on partly with funds provided by the Board of Ordnance and Fortification and partly from private
sources, and from a special endowment of the Smithsonian Institution. The experiments are carried
on with the approval of the Board of Regents of the Smithsonian Institution.
The public’s interest in them may lead to an unfounded expectation as to their immediate results,
without an explanation which is here briefly given.
These trials, with some already conducted with steam-driven flying machines, are believed to be
the first in the history of invention where bodies, far heavier than the air itself, have been sustained
in the air for more than a few seconds by purely mechanical means.
In my previous trials, success has only been reached after initial failures, which alone have
taught the way to it, and I know no reason why the prospective trials should be an exception.
It is possible, rather than probable, that it may be otherwise now, but judging them from the light
of past experience, it is to be regretted that the enforced publicity which has been given to these
initial experiments, which are essentially experiments and nothing else, may lead to quite
unfounded expectations.
It is the practice of all scientific men, indeed of all prudent men, not to make public the results
of their work till these are certain. This consideration, and not any desire to withhold from the
public matters in which the public is interested, has dictated the policy thus far pursued here. The
fullest publicity, consistent with the national interest (since these recent experiments have for their
object the development of a machine for war purposes), will be given to this work when it reaches
a stage which warrants publication.
(Signed.) S. P. LANGLEY.
[p281]
Although it was impossible to immediately find funds for actively
continuing the work, the writer finally, after some delay, persuaded Mr.
Langley to allot a small sum from a limited fund which personal friends had
some time previously placed at his disposal for use in any experiments he
might wish to make. This small sum was used to meet the expense of the
workmen who were kept employed long enough to completely repair the
main frame so that, should further experiments be possible at a later time,
there would be no danger of important parts and fittings having been lost in
the meantime, and even if no further experiments were made the frame
would be in such condition that others could profit from an examination of
it, the frame itself embodying the solution of many important problems
which had cost much time and money.
In the spring of 1904, after the repairs to the main frame were well under
way, the writer on his own initiative undertook to see what could be done
towards securing for Mr. Langley’s disposal the small financial assistance
August 19, 1903.
TO THE PRESS: The present experiments being made in mechanical flight have been carried
on partly with funds provided by the Board of Ordnance and Fortification and partly from private
sources, and from a special endowment of the Smithsonian Institution. The experiments are carried
on with the approval of the Board of Regents of the Smithsonian Institution.
The public’s interest in them may lead to an unfounded expectation as to their immediate results,
without an explanation which is here briefly given.
These trials, with some already conducted with steam-driven flying machines, are believed to be
the first in the history of invention where bodies, far heavier than the air itself, have been sustained
in the air for more than a few seconds by purely mechanical means.
In my previous trials, success has only been reached after initial failures, which alone have
taught the way to it, and I know no reason why the prospective trials should be an exception.
It is possible, rather than probable, that it may be otherwise now, but judging them from the light
of past experience, it is to be regretted that the enforced publicity which has been given to these
initial experiments, which are essentially experiments and nothing else, may lead to quite
unfounded expectations.
It is the practice of all scientific men, indeed of all prudent men, not to make public the results
of their work till these are certain. This consideration, and not any desire to withhold from the
public matters in which the public is interested, has dictated the policy thus far pursued here. The
fullest publicity, consistent with the national interest (since these recent experiments have for their
object the development of a machine for war purposes), will be given to this work when it reaches
a stage which warrants publication.
(Signed.) S. P. LANGLEY.
[p281]
Although it was impossible to immediately find funds for actively
continuing the work, the writer finally, after some delay, persuaded Mr.
Langley to allot a small sum from a limited fund which personal friends had
some time previously placed at his disposal for use in any experiments he
might wish to make. This small sum was used to meet the expense of the
workmen who were kept employed long enough to completely repair the
main frame so that, should further experiments be possible at a later time,
there would be no danger of important parts and fittings having been lost in
the meantime, and even if no further experiments were made the frame
would be in such condition that others could profit from an examination of
it, the frame itself embodying the solution of many important problems
which had cost much time and money.
In the spring of 1904, after the repairs to the main frame were well under
way, the writer on his own initiative undertook to see what could be done
towards securing for Mr. Langley’s disposal the small financial assistance
Page 504
necessary to continue the work; but he found that while a number of men of
means were willing to assist in the development of the aerodrome, provided
arrangements were made for later commercialization, yet none were ready
to render the assistance from a desire to assist in the prosecution of
scientific work. Many years prior to this Mr. Langley had had some very
tempting propositions made to him by certain business men with a view to
carrying on the work in a way that would lead to later commercial
development. He had never patented anything previously in his life, and
although many friends had urged that it was only proper that he should
patent whatever of value had been developed in connection with the
aerodromes, he steadfastly refused to do so. He had given his time and his
best labors to the world without hope of remuneration, and he could not
bring himself at his stage of life to consent to capitalize his scientific work.
Success seemed only a step away, and his age was such that any delay in
achieving success increased the probability of his not living to see it, but he
maintained positively and resolutely that, if neither the War Department nor
others felt sufficient interest in the work to provide the small amount of
funds necessary to continue the experiments, and they therefore could be
continued only by his giving in and permitting his work to be capitalized,
he would have to deny himself the hope of living to see the machine
achieve success.
The result is well known to all.
P RESENT S TATUS OF THE W ORK
The completely repaired frame of the large machine is now stored in one
of the workshops at the Smithsonian Institution. The large engine, the
steam-driven models Nos. 5 and 6, and the quarter-size model, driven by
the three [p282] horse-power gasoline engine, are on exhibition at the U. S.
National Museum. The launching-car and a small amount of materials have
also been stored away. The large house-boat, the construction and
maintenance of which proved such a serious drain on the finances, and the
preservation of which would have entailed the continuance of heavy fixed
charges, has been turned over to the War Department and sold, as has also
means were willing to assist in the development of the aerodrome, provided
arrangements were made for later commercialization, yet none were ready
to render the assistance from a desire to assist in the prosecution of
scientific work. Many years prior to this Mr. Langley had had some very
tempting propositions made to him by certain business men with a view to
carrying on the work in a way that would lead to later commercial
development. He had never patented anything previously in his life, and
although many friends had urged that it was only proper that he should
patent whatever of value had been developed in connection with the
aerodromes, he steadfastly refused to do so. He had given his time and his
best labors to the world without hope of remuneration, and he could not
bring himself at his stage of life to consent to capitalize his scientific work.
Success seemed only a step away, and his age was such that any delay in
achieving success increased the probability of his not living to see it, but he
maintained positively and resolutely that, if neither the War Department nor
others felt sufficient interest in the work to provide the small amount of
funds necessary to continue the experiments, and they therefore could be
continued only by his giving in and permitting his work to be capitalized,
he would have to deny himself the hope of living to see the machine
achieve success.
The result is well known to all.
P RESENT S TATUS OF THE W ORK
The completely repaired frame of the large machine is now stored in one
of the workshops at the Smithsonian Institution. The large engine, the
steam-driven models Nos. 5 and 6, and the quarter-size model, driven by
the three [p282] horse-power gasoline engine, are on exhibition at the U. S.
National Museum. The launching-car and a small amount of materials have
also been stored away. The large house-boat, the construction and
maintenance of which proved such a serious drain on the finances, and the
preservation of which would have entailed the continuance of heavy fixed
charges, has been turned over to the War Department and sold, as has also
Page 505
the power-launch and other paraphernalia which it seemed useless to
preserve.
The writer is firmly convinced that the aerodrome is not only correct in
principle but that it possesses no inherent faults or weaknesses, and that the
success which the work deserves has been frustrated by two most
unfortunate accidents in the launching of the machine. Other plans of
launching, several of which were studied out during the early stages of the
work on the large machine, would have avoided the accident which did
occur, but, of course, might have produced others possibly even more
disastrous, but which could be determined only by actual trial. But even
recognizing certain fundamental weaknesses of the launching mechanism as
used, he believes that there is no inherent reason why the machine should
not have been successfully launched, and that the accidents which proved
so disastrous in the two experiments were not such as should cause a lack of
confidence in the final success of the aerodrome.
It might be of interest to add that the writer is now preparing to resume
the work at the earliest opportunity, and that the machine will be used in
practically the form in which it existed at the two previous experiments,
though a slight change will be made permitting experiments over the land
rather than the water. The only thing that prevents an immediate resumption
is the pressure of private business matters.
Before closing this record the writer wishes to acknowledge the very
valuable assistance in the work rendered by Mr. Richard Rathbun, Assistant
Secretary of the Smithsonian Institution, through his moral support and
interest in it at all times, and especially during the trying days of the
summer of 1903; by Captain I. N. Lewis, who, while Recorder of the Board
of Ordnance and Fortification from 1898 to 1902, manifested keen interest
in the work and gave it his moral support before the Board; by Professor
John M. Manly, who devoted the whole of the summer of 1903 to it; and by
Professor W. G. Manly, who devoted a large part of the summer of 1903 to
assistance in the preparation for the actual field-trials of the aerodrome.
Mention must also be made of the very loyal and valuable services
rendered by Mr. R. L. Reed, the very efficient foreman of the work during
preserve.
The writer is firmly convinced that the aerodrome is not only correct in
principle but that it possesses no inherent faults or weaknesses, and that the
success which the work deserves has been frustrated by two most
unfortunate accidents in the launching of the machine. Other plans of
launching, several of which were studied out during the early stages of the
work on the large machine, would have avoided the accident which did
occur, but, of course, might have produced others possibly even more
disastrous, but which could be determined only by actual trial. But even
recognizing certain fundamental weaknesses of the launching mechanism as
used, he believes that there is no inherent reason why the machine should
not have been successfully launched, and that the accidents which proved
so disastrous in the two experiments were not such as should cause a lack of
confidence in the final success of the aerodrome.
It might be of interest to add that the writer is now preparing to resume
the work at the earliest opportunity, and that the machine will be used in
practically the form in which it existed at the two previous experiments,
though a slight change will be made permitting experiments over the land
rather than the water. The only thing that prevents an immediate resumption
is the pressure of private business matters.
Before closing this record the writer wishes to acknowledge the very
valuable assistance in the work rendered by Mr. Richard Rathbun, Assistant
Secretary of the Smithsonian Institution, through his moral support and
interest in it at all times, and especially during the trying days of the
summer of 1903; by Captain I. N. Lewis, who, while Recorder of the Board
of Ordnance and Fortification from 1898 to 1902, manifested keen interest
in the work and gave it his moral support before the Board; by Professor
John M. Manly, who devoted the whole of the summer of 1903 to it; and by
Professor W. G. Manly, who devoted a large part of the summer of 1903 to
assistance in the preparation for the actual field-trials of the aerodrome.
Mention must also be made of the very loyal and valuable services
rendered by Mr. R. L. Reed, the very efficient foreman of the work during
Page 506
the last ten years of its progress, to whom much credit is due for his
perseverance and skill in overcoming many of the difficulties which
presented themselves, as well as to Mr. G. D. McDonald, Mr. C. H. Darcey,
Mr. F. Hewitt, Mr. R. S. Newham [p283] and the other employees who
labored faithfully for the several years they were engaged on it.
B LÉRIOT M ACHINE OF 19 07 ON L ANGLEY T YPE
Since completing the preparation of this Memoir, the writer’s attention
has been called to some very interesting tests made at Issy by M. Louis
Blériot with a machine of the Langley type. These tests confirm in such a
practical manner the conviction that the large aerodrome would have flown
successfully had it not been wrecked in launching that it has seemed well to
here quote an interesting description of them published in the “Bollettino
della Società Aeronautica Italiana, August, 1907,” under the title “Il nuovo
aeroplano Blériot,” a translation of which is as follows:
THE NEW BLÉRIOT AEROPLANE
The Blériot IV in the form of a bird, of which we spoke at length in No. 4 of the Bulletin of this
year, does not appear to give good results, perhaps on account of its lack of stability, and Blériot
instead of trying some modifications which might remedy such a grave fault, laid it aside and at
once began the construction of a new type, No. V, adopting purely and simply the arrangement of
the American, Langley, which offers a good stability (see Bulletin 11–12, November to December,
1905, pages 187 and 188).
The experiments, which were commenced a month ago, were first completely negative, because
the 24 HP. motor would not turn the propeller, which was 1.80 m. in diameter and 1.40 m. pitch.
By advice of Captain Ferber, Blériot reduced the pitch of his propeller to 0.90 m., so that the
motor could give all its force.
This modification was an important one for his aeroplane. From that moment every trial marked
an advance. On July 12, he made a flight of 30 m., and the aviator was able to show that the lateral
stability was perfect. On July 15, the trial was made against a wind of 6 miles an hour, but gave
good results. He made a flight of 80 m., showing, however, that the hind part of the aeroplane was
too heavy. In this flight he arose as high as a second story, and on landing the wheels and one
propeller were somewhat damaged.
On July 24, repairs having been completed, a new trial was made. This time, in order to remedy
the defect in the balance, Blériot had moved his seat forward about 80 cm. The correction was too
great, for on that day the aeroplane, although the hind part arose, was not able to leave the ground.
On July 27, after having mounted the seat on wheels as skiffs, Blériot resumed the trials and made
a flight of 120 m., at first moving his seat back and then, after getting started, bringing it forward.
Blériot had not provided this aeroplane with an elevating rudder, but, following the example of
Lilienthal, changed the center of gravity of the apparatus by moving his own person, and after
having established the proper angle remained immovable on his seat. In order to arise or descend,
the aviator made use of the spark lever, thus varying the number of turns of the propeller.
perseverance and skill in overcoming many of the difficulties which
presented themselves, as well as to Mr. G. D. McDonald, Mr. C. H. Darcey,
Mr. F. Hewitt, Mr. R. S. Newham [p283] and the other employees who
labored faithfully for the several years they were engaged on it.
B LÉRIOT M ACHINE OF 19 07 ON L ANGLEY T YPE
Since completing the preparation of this Memoir, the writer’s attention
has been called to some very interesting tests made at Issy by M. Louis
Blériot with a machine of the Langley type. These tests confirm in such a
practical manner the conviction that the large aerodrome would have flown
successfully had it not been wrecked in launching that it has seemed well to
here quote an interesting description of them published in the “Bollettino
della Società Aeronautica Italiana, August, 1907,” under the title “Il nuovo
aeroplano Blériot,” a translation of which is as follows:
THE NEW BLÉRIOT AEROPLANE
The Blériot IV in the form of a bird, of which we spoke at length in No. 4 of the Bulletin of this
year, does not appear to give good results, perhaps on account of its lack of stability, and Blériot
instead of trying some modifications which might remedy such a grave fault, laid it aside and at
once began the construction of a new type, No. V, adopting purely and simply the arrangement of
the American, Langley, which offers a good stability (see Bulletin 11–12, November to December,
1905, pages 187 and 188).
The experiments, which were commenced a month ago, were first completely negative, because
the 24 HP. motor would not turn the propeller, which was 1.80 m. in diameter and 1.40 m. pitch.
By advice of Captain Ferber, Blériot reduced the pitch of his propeller to 0.90 m., so that the
motor could give all its force.
This modification was an important one for his aeroplane. From that moment every trial marked
an advance. On July 12, he made a flight of 30 m., and the aviator was able to show that the lateral
stability was perfect. On July 15, the trial was made against a wind of 6 miles an hour, but gave
good results. He made a flight of 80 m., showing, however, that the hind part of the aeroplane was
too heavy. In this flight he arose as high as a second story, and on landing the wheels and one
propeller were somewhat damaged.
On July 24, repairs having been completed, a new trial was made. This time, in order to remedy
the defect in the balance, Blériot had moved his seat forward about 80 cm. The correction was too
great, for on that day the aeroplane, although the hind part arose, was not able to leave the ground.
On July 27, after having mounted the seat on wheels as skiffs, Blériot resumed the trials and made
a flight of 120 m., at first moving his seat back and then, after getting started, bringing it forward.
Blériot had not provided this aeroplane with an elevating rudder, but, following the example of
Lilienthal, changed the center of gravity of the apparatus by moving his own person, and after
having established the proper angle remained immovable on his seat. In order to arise or descend,
the aviator made use of the spark lever, thus varying the number of turns of the propeller.
Page 507
During a second trial on the same day, having accidently reached the limit of the aviation field,
Blériot, without allowing himself to be surprised and obliged to descend, decided to attempt a turn
by maneuvering the steering rudder [p284] and to return again to the center of the field. With
marvelous precision, the aeroplane began to describe a circle of about 200 m. radius, inclining as if
on a banked track. Having finished the flight, he quickly regained his balance still in the direction
of the wind, but on account of a slight movement of the aviator, the aeroplane fell to such an extent
that he was obliged to land. He landed gently and without shock, rolling on his wheels.
1
On August 1, he made another flight of 100 m. in 6 2 seconds; and on the 6th, one of 265 m. with
one interruption. While the attention of the pilot was distracted for a moment, the aeroplane, which
was flying at a height of 2 or 3 m. above the ground, touched the soil with its sustaining wheels at
the end of 122 m. and then immediately arising, covered the remaining 143 m. at a height of 12 m.
Blériot, moving forward too quickly, caused the aeroplane to descend swiftly to the ground, and
the shock broke the axle and the blades of the propeller were bent. In order to confirm this account,
we reproduce what was said in the “Auto” of August 7, 1907.
“M. Blériot, continuing the trials of his aeroplane yesterday, surpassed the superb results which
he had already obtained. The trial took place at 2 o’clock in the afternoon on the aviation field of
Issy. After a sustained flight of about 122 m. at a height of 2 m., the aeroplane touched the ground,
without stopping, however, and set out again almost immediately at a height of 12 m. and traversed
about 143 m. M. Blériot, who for the time had no other means of balancing but by moving his
body, then moved a little forward to stop the ascent. The aeroplane plunged forward, and in the fall
the propeller was damaged and the axle broken.
“M. Blériot, whose courage as a sportsman equals his learning as an engineer, was fortunately
uninjured. An inspection of the apparatus showed that one blade of the propeller was bent, which
was sufficient to prevent the maneuver made by the aviator having its desired effect and
contributed to the fall. The engine will be repaired without difficulty and the trials will be resumed
Friday.”
On August 10, he made a flight of 80 m., but the motor was not in perfect order, so Blériot did
not make other trials. He decided, however, to substitute definitely a 50 HP. motor for the 24 HP.
motor with which he made all the experiments above reported, which were of a character to
encourage the most sanguine expectations.
Ferber advised Blériot to adopt an elevating rudder also, because the effect produced by
changing the position of the center of gravity, although efficacious is very difficult and delicate to
control.
The conclusion of an article by Ferber in “Nature” of August 10, is worthy of note. He says:
“Let us remark, in conclusion, how fruitful is the method of personal trial which we have always
advised in preference to any calculation. This year, with his fourth apparatus, Blériot has not met
with any damage to his aeroplane. He made the trials himself and they quickly led to results,
because each trial gave him an exact idea of what was to be corrected. That is the condition of
success.”
Blériot, without allowing himself to be surprised and obliged to descend, decided to attempt a turn
by maneuvering the steering rudder [p284] and to return again to the center of the field. With
marvelous precision, the aeroplane began to describe a circle of about 200 m. radius, inclining as if
on a banked track. Having finished the flight, he quickly regained his balance still in the direction
of the wind, but on account of a slight movement of the aviator, the aeroplane fell to such an extent
that he was obliged to land. He landed gently and without shock, rolling on his wheels.
1
On August 1, he made another flight of 100 m. in 6 2 seconds; and on the 6th, one of 265 m. with
one interruption. While the attention of the pilot was distracted for a moment, the aeroplane, which
was flying at a height of 2 or 3 m. above the ground, touched the soil with its sustaining wheels at
the end of 122 m. and then immediately arising, covered the remaining 143 m. at a height of 12 m.
Blériot, moving forward too quickly, caused the aeroplane to descend swiftly to the ground, and
the shock broke the axle and the blades of the propeller were bent. In order to confirm this account,
we reproduce what was said in the “Auto” of August 7, 1907.
“M. Blériot, continuing the trials of his aeroplane yesterday, surpassed the superb results which
he had already obtained. The trial took place at 2 o’clock in the afternoon on the aviation field of
Issy. After a sustained flight of about 122 m. at a height of 2 m., the aeroplane touched the ground,
without stopping, however, and set out again almost immediately at a height of 12 m. and traversed
about 143 m. M. Blériot, who for the time had no other means of balancing but by moving his
body, then moved a little forward to stop the ascent. The aeroplane plunged forward, and in the fall
the propeller was damaged and the axle broken.
“M. Blériot, whose courage as a sportsman equals his learning as an engineer, was fortunately
uninjured. An inspection of the apparatus showed that one blade of the propeller was bent, which
was sufficient to prevent the maneuver made by the aviator having its desired effect and
contributed to the fall. The engine will be repaired without difficulty and the trials will be resumed
Friday.”
On August 10, he made a flight of 80 m., but the motor was not in perfect order, so Blériot did
not make other trials. He decided, however, to substitute definitely a 50 HP. motor for the 24 HP.
motor with which he made all the experiments above reported, which were of a character to
encourage the most sanguine expectations.
Ferber advised Blériot to adopt an elevating rudder also, because the effect produced by
changing the position of the center of gravity, although efficacious is very difficult and delicate to
control.
The conclusion of an article by Ferber in “Nature” of August 10, is worthy of note. He says:
“Let us remark, in conclusion, how fruitful is the method of personal trial which we have always
advised in preference to any calculation. This year, with his fourth apparatus, Blériot has not met
with any damage to his aeroplane. He made the trials himself and they quickly led to results,
because each trial gave him an exact idea of what was to be corrected. That is the condition of
success.”
Page 508
[p285] ◊
APPENDIX
STUDY OF THE AMERICAN BUZZARD AND THE “JOHN
CROW”
In the preparation of this Memoir, the writer has deemed it best to
generally omit any mention of plans and ideas which were brought forth in
the work, unless constructions or tests in accordance with them were carried
to a sufficient extent to admit of some definite conclusion regarding them.
However, owing to the important part played by the warping of the
supporting surfaces, or the variation in the angle of auxiliary surfaces, in the
methods of preserving the equilibrium of practically all flying machines of
the present day, it may be of interest to here add a short mention of the
direction in which plans along this line were originally proposed in this
work. Mention has already been made of the importance which Mr. Langley
attached to the study of the works of the great master-builder, Nature,
though recognizing at the same time that owing both to the difference in the
forces and methods of construction possible to man, it was not in general
possible for him to produce the best results by attempting to too closely
imitate the methods or plans of Nature.
Mr. Langley considered it not practicable or best to attempt to imitate the
details of construction of the flying mechanism of birds. At the same time,
he strongly believed that much was to be learned from them about the
practical side of the art of balancing, and he therefore spent a great deal of
time both in analyzing the methods practiced by the birds in preserving
their equilibrium and in criticizing his own plans in this direction in the
light of what Nature would seem likely to do if she had to construct a flying
creature on such a large scale. In carrying on his investigations in the art as
practiced by the birds, he made a trip to Jamaica during the early weeks of
1900, in order to study the species of buzzard which are so numerous and
tame there and are known locally as the “John Crow.” After his return from
this trip he wrote the following very interesting letter to Mr. Robert
APPENDIX
STUDY OF THE AMERICAN BUZZARD AND THE “JOHN
CROW”
In the preparation of this Memoir, the writer has deemed it best to
generally omit any mention of plans and ideas which were brought forth in
the work, unless constructions or tests in accordance with them were carried
to a sufficient extent to admit of some definite conclusion regarding them.
However, owing to the important part played by the warping of the
supporting surfaces, or the variation in the angle of auxiliary surfaces, in the
methods of preserving the equilibrium of practically all flying machines of
the present day, it may be of interest to here add a short mention of the
direction in which plans along this line were originally proposed in this
work. Mention has already been made of the importance which Mr. Langley
attached to the study of the works of the great master-builder, Nature,
though recognizing at the same time that owing both to the difference in the
forces and methods of construction possible to man, it was not in general
possible for him to produce the best results by attempting to too closely
imitate the methods or plans of Nature.
Mr. Langley considered it not practicable or best to attempt to imitate the
details of construction of the flying mechanism of birds. At the same time,
he strongly believed that much was to be learned from them about the
practical side of the art of balancing, and he therefore spent a great deal of
time both in analyzing the methods practiced by the birds in preserving
their equilibrium and in criticizing his own plans in this direction in the
light of what Nature would seem likely to do if she had to construct a flying
creature on such a large scale. In carrying on his investigations in the art as
practiced by the birds, he made a trip to Jamaica during the early weeks of
1900, in order to study the species of buzzard which are so numerous and
tame there and are known locally as the “John Crow.” After his return from
this trip he wrote the following very interesting letter to Mr. Robert
Page 509
Ridgway, requesting certain data regarding the American buzzard, which he
wished to compare with some data on the “John Crow” which he had
obtained on this trip:
MARCH 29, 1900.
DEAR MR. RIDGWAY:
I have just returned from Jamaica, where among other occupations, I have been studying the
evolutions of the buzzard locally called the “John Crow,” a soaring bird which is almost as much
superior in skill to our buzzard as that is to a barn-yard fowl in its power of keeping itself in the air
without flapping its wings, in what is very nearly a calm.
I have observed particularly the following points with the Jamaica specimen (which I can only
give, however, approximately), and I should like to have you give corresponding ones for our
Washington buzzard if you can oblige me. [p286]
I note here that the measurements were made on a live bird and that it was impracticable to get
the separate weight of the wings except by estimate, but the two wings may be estimated
1 3
collectively as 1 4 lbs., the whole weight being 2 4 lbs. to 3 lbs.
Approximate values:
Weight of the bird complete, 3 pounds.
Length of bird, 23 inches.
Spread of wings from tip to tip, 5 ft. 5 in.
Complete curtate area of both wings (that is, the area of the shadow of the bird’s wings when
these are fully extended under a vertical sun) is 600 square inches, or nearly 4 sq. ft.,
3
consequently each square foot of the bird’s sustaining surface carries 4 lbs. Diedral angle
nearly 150°.
When the bird is soaring in a nearly calm atmosphere, which it inexplicably does,—soaring I
mean nearly in line of the observer’s eyes and coming directly to of going directly away from him,
—it presents nearly the following appearance:
wished to compare with some data on the “John Crow” which he had
obtained on this trip:
MARCH 29, 1900.
DEAR MR. RIDGWAY:
I have just returned from Jamaica, where among other occupations, I have been studying the
evolutions of the buzzard locally called the “John Crow,” a soaring bird which is almost as much
superior in skill to our buzzard as that is to a barn-yard fowl in its power of keeping itself in the air
without flapping its wings, in what is very nearly a calm.
I have observed particularly the following points with the Jamaica specimen (which I can only
give, however, approximately), and I should like to have you give corresponding ones for our
Washington buzzard if you can oblige me. [p286]
I note here that the measurements were made on a live bird and that it was impracticable to get
the separate weight of the wings except by estimate, but the two wings may be estimated
1 3
collectively as 1 4 lbs., the whole weight being 2 4 lbs. to 3 lbs.
Approximate values:
Weight of the bird complete, 3 pounds.
Length of bird, 23 inches.
Spread of wings from tip to tip, 5 ft. 5 in.
Complete curtate area of both wings (that is, the area of the shadow of the bird’s wings when
these are fully extended under a vertical sun) is 600 square inches, or nearly 4 sq. ft.,
3
consequently each square foot of the bird’s sustaining surface carries 4 lbs. Diedral angle
nearly 150°.
When the bird is soaring in a nearly calm atmosphere, which it inexplicably does,—soaring I
mean nearly in line of the observer’s eyes and coming directly to of going directly away from him,
—it presents nearly the following appearance:
Page 510
F IG. 1—Jamaica, Mch. 22, 1900. “John Crow.” Sketch soaring horizontally, by W.
H. Holmes. Weight 3 lbs. Total wings area = 546 in. Perpendicular distance c below
a b = 3.3 in. =
√(546)
7
= CP 2 −CG 2 .
F IG. 2—Another.
√(546)
CP 2 −CG 2 = 3.3 in. = 7
.
FIGS. 1 and 2.—Type sketches of wings by Holmes from a mean of positions taken from his
own sketches and photographs, and also from sketches and photographs by Langley.
F IG. 3.—Type sketch of same birds, average type, position of wings.—
S. P. Langley.
√(546)
CP 2 −CG 2 =3.6 in. = 6.5
.
F IG. 4.—Average typical position of wings in soaring gull. From memory by S.
1
P. Langley. (The scale here may be taken approximately at 13 ).
[p287]
H. Holmes. Weight 3 lbs. Total wings area = 546 in. Perpendicular distance c below
a b = 3.3 in. =
√(546)
7
= CP 2 −CG 2 .
F IG. 2—Another.
√(546)
CP 2 −CG 2 = 3.3 in. = 7
.
FIGS. 1 and 2.—Type sketches of wings by Holmes from a mean of positions taken from his
own sketches and photographs, and also from sketches and photographs by Langley.
F IG. 3.—Type sketch of same birds, average type, position of wings.—
S. P. Langley.
√(546)
CP 2 −CG 2 =3.6 in. = 6.5
.
F IG. 4.—Average typical position of wings in soaring gull. From memory by S.
1
P. Langley. (The scale here may be taken approximately at 13 ).
[p287]
Page 511
I must preface what follows by a little statement of the things which particularly interest me here
and which are not a naturalist’s ordinary concern.
First, I want to know the CG of the bird when in flight. You will understand that though there is
but one center of gravity (here symbolized as CG ), it may be considered (1) with reference to its
position on the horizontal plan of the bird with wings extended, when it will always be found
somewhere in the medial vertical plane, passing through the body, and usually nearly at a certain
point with reference to length, the position thus considered being called CG, or (2) the position of
the same CG with reference to a vertical plane passing transversely through the medial line, the
position thus considered being called CG2. In the latter case you will understand that the CG which
is that of the whole body, wings and all, will be carried more or less upward when the wings are
thrown high up, and will be carried temporarily downward when the wings are at their lowest point
of the stroke. It would have a certain position when the bird was at rest and another position when
it was soaring and the wings were above the body.
The soaring bird is chiefly held upward by the pressure of the air under each wing, and just as
the common center of gravity is a point where all the efforts of gravity are supposed to be
centered, so there is a common center of pressure, or one point where all the efforts of the upper
pressure of the air may be supposed to be centered, and it will be clear, on very little consideration
that this latter point must be always nearly in a vertical line through the CG, and usually above it.
Call it CP.
CG1 and CP1 are then, the symbols of CG and CP as referred to the horizontal plane. CG2 and
CP2 are the symbols for the corresponding ones when referred to their position in the vertical
plane.
I shall be glad to explain to you, if you are not familiar with it, the simple method of finding the
CG1 and CG2. It consists in bending the wings into just the position that they would ordinarily
occupy above the body in plain soaring flight, keeping them there by a very light bent stick or
wire, then hanging the bird up by a line attached to the tip of one wing, and see where this line
would pass through the body of the bird, for the CG will be somewhere in this line. After marking
then, on the body of the bird its position, hang it up a second time by the head or tail and note
again where the new vertical line runs in the new position. There is but one CG and but one point
in which two straight lines can cross, and that will be the CG necessarily. Note with all care just
where this is above or below the center of the body of the bird.
As for the CP for either wing, that may be nearly found by tracing the wing on a flat piece of
thick paper or cardboard strong enough not to bend much—cutting out the tracing and balancing it
well on the point of a pencil—the point about which it balances is very near CP2 or the center of
pressure in the vertical plane. There is such a point of course in each wing, and when they are
thrown up in the actual position that they have in calm soaring flight, we may suppose a horizontal
line drawn between them, and it is the distance from this horizontal line to CG2 compared with the
area of the wings or with the distance between their extended tips which we want to know, which
gives the vertical distance which the CG is below the CP, the thing we want to know.
It will be very convenient also to have a wing dissected from the body and the wing itself held
in about the soaring curve by a bit of light stick balanced on a pencil point, which will give the CG
of the wing as distinct from that of the body. However, the three things I principally want, beside a
sketch or [p288] photograph of the bird from about its own level coming directly toward or going
directly away in soaring flight, are these:
Approximate weight of the bird,—and approximate tracing of its extended wing with the area,
so that we can tell the area of the supporting surface relative to the weight, and finally, the distance
and which are not a naturalist’s ordinary concern.
First, I want to know the CG of the bird when in flight. You will understand that though there is
but one center of gravity (here symbolized as CG ), it may be considered (1) with reference to its
position on the horizontal plan of the bird with wings extended, when it will always be found
somewhere in the medial vertical plane, passing through the body, and usually nearly at a certain
point with reference to length, the position thus considered being called CG, or (2) the position of
the same CG with reference to a vertical plane passing transversely through the medial line, the
position thus considered being called CG2. In the latter case you will understand that the CG which
is that of the whole body, wings and all, will be carried more or less upward when the wings are
thrown high up, and will be carried temporarily downward when the wings are at their lowest point
of the stroke. It would have a certain position when the bird was at rest and another position when
it was soaring and the wings were above the body.
The soaring bird is chiefly held upward by the pressure of the air under each wing, and just as
the common center of gravity is a point where all the efforts of gravity are supposed to be
centered, so there is a common center of pressure, or one point where all the efforts of the upper
pressure of the air may be supposed to be centered, and it will be clear, on very little consideration
that this latter point must be always nearly in a vertical line through the CG, and usually above it.
Call it CP.
CG1 and CP1 are then, the symbols of CG and CP as referred to the horizontal plane. CG2 and
CP2 are the symbols for the corresponding ones when referred to their position in the vertical
plane.
I shall be glad to explain to you, if you are not familiar with it, the simple method of finding the
CG1 and CG2. It consists in bending the wings into just the position that they would ordinarily
occupy above the body in plain soaring flight, keeping them there by a very light bent stick or
wire, then hanging the bird up by a line attached to the tip of one wing, and see where this line
would pass through the body of the bird, for the CG will be somewhere in this line. After marking
then, on the body of the bird its position, hang it up a second time by the head or tail and note
again where the new vertical line runs in the new position. There is but one CG and but one point
in which two straight lines can cross, and that will be the CG necessarily. Note with all care just
where this is above or below the center of the body of the bird.
As for the CP for either wing, that may be nearly found by tracing the wing on a flat piece of
thick paper or cardboard strong enough not to bend much—cutting out the tracing and balancing it
well on the point of a pencil—the point about which it balances is very near CP2 or the center of
pressure in the vertical plane. There is such a point of course in each wing, and when they are
thrown up in the actual position that they have in calm soaring flight, we may suppose a horizontal
line drawn between them, and it is the distance from this horizontal line to CG2 compared with the
area of the wings or with the distance between their extended tips which we want to know, which
gives the vertical distance which the CG is below the CP, the thing we want to know.
It will be very convenient also to have a wing dissected from the body and the wing itself held
in about the soaring curve by a bit of light stick balanced on a pencil point, which will give the CG
of the wing as distinct from that of the body. However, the three things I principally want, beside a
sketch or [p288] photograph of the bird from about its own level coming directly toward or going
directly away in soaring flight, are these:
Approximate weight of the bird,—and approximate tracing of its extended wing with the area,
so that we can tell the area of the supporting surface relative to the weight, and finally, the distance
Page 512
between CP2, and CG2, which is obtainable by the process which I have explained.
I am afraid that what I have just been describing at such length may have a certain obscurity to
you, but if you will give me an opportunity, I shall be pleased to illustrate it with the actual
experiment when the bird is hung up by a string, and you will see that it is in reality simple.
Referring to the sketches on page 3 of this communication, a and b correspond to the centers of
pressure on either wing where the upward pressure of the air distributed over each wing may be
supposed to be gathered in a single point. This, as I have said, is called the center of pressure with
reference to the vertical flight, and its symbol is CP2, while the horizontal dotted line between
them represents the level of CP2, from the best estimate that I could make when the wings are in
their natural position of soaring. It is evident that this line passed far above the body of the vulture,
and if (the corresponding symbol for the height of the center of gravity being CG2), the CG2, of the
entire bird be taken, it will be found to lie nearly in the point c. Where c is in the present case, I
could not determine exactly in my hasty examinations in the live bird, but I assume that it is about
1
2
way between the central horizontal axial line of the bird’s body and the upper portion. I repeat
that it is important to me to know what the vertical distance is between CP2 and CG2 in each
specimen of soaring bird. I may observe in illustration that in the common sea-gull, it is nearly as
shown in the faint sketch; that is to say, that the corresponding line a b in the soaring gull passes
distinctly through the upper part of the body, and the distance down to the CG2 of the whole in the
gull is almost nil, while in the buzzard it is very considerable as shown by the corresponding
distance in the “John Crow.”
Now, what I want to get from you is the corresponding figures for an average specimen of our
Washington buzzard. If you will kindly have one killed and weighed while fresh, and before the
rigor-mortis has set in, first noting the position of its wings when soaring in a calm, and (if
possible) when coming toward you or going away in about a horizontal plane with your eye, in
which position the wings will be elevated and bent somewhat as in the case of the above sketch of
the “John Crow”; if you will kindly do this, so as to give me corresponding facts with reference to
the buzzard, namely weight, area of extended wing surface, distance between tips as bent up in
ordinary flight, distance between extended tips, the quantity CP2−CG2, and also will make such a
tracing of the buzzard’s wing as Mr. Manly will show you of the “John Crow’s,” I shall be obliged.
My impression is that the buzzard is a considerably heavier bird than the “John Crow,” without,
however, very much greater spread of wing. I may observe that when the wings of the Jamaica bird
were spread out, they were spread quite to their utmost extent, and the distance between the tips of
the terminal feathers was much greater than when in flight. I wish you would kindly also add the
scientific name of the “John Crow,” with any particulars that you would think of interest.
If there be any special expenses incurred in the preparation of this memorandum, including the
time of a photographer, I will direct them to be paid from the Smithsonian fund. [p289]
I am afraid that what I have just been describing at such length may have a certain obscurity to
you, but if you will give me an opportunity, I shall be pleased to illustrate it with the actual
experiment when the bird is hung up by a string, and you will see that it is in reality simple.
Referring to the sketches on page 3 of this communication, a and b correspond to the centers of
pressure on either wing where the upward pressure of the air distributed over each wing may be
supposed to be gathered in a single point. This, as I have said, is called the center of pressure with
reference to the vertical flight, and its symbol is CP2, while the horizontal dotted line between
them represents the level of CP2, from the best estimate that I could make when the wings are in
their natural position of soaring. It is evident that this line passed far above the body of the vulture,
and if (the corresponding symbol for the height of the center of gravity being CG2), the CG2, of the
entire bird be taken, it will be found to lie nearly in the point c. Where c is in the present case, I
could not determine exactly in my hasty examinations in the live bird, but I assume that it is about
1
2
way between the central horizontal axial line of the bird’s body and the upper portion. I repeat
that it is important to me to know what the vertical distance is between CP2 and CG2 in each
specimen of soaring bird. I may observe in illustration that in the common sea-gull, it is nearly as
shown in the faint sketch; that is to say, that the corresponding line a b in the soaring gull passes
distinctly through the upper part of the body, and the distance down to the CG2 of the whole in the
gull is almost nil, while in the buzzard it is very considerable as shown by the corresponding
distance in the “John Crow.”
Now, what I want to get from you is the corresponding figures for an average specimen of our
Washington buzzard. If you will kindly have one killed and weighed while fresh, and before the
rigor-mortis has set in, first noting the position of its wings when soaring in a calm, and (if
possible) when coming toward you or going away in about a horizontal plane with your eye, in
which position the wings will be elevated and bent somewhat as in the case of the above sketch of
the “John Crow”; if you will kindly do this, so as to give me corresponding facts with reference to
the buzzard, namely weight, area of extended wing surface, distance between tips as bent up in
ordinary flight, distance between extended tips, the quantity CP2−CG2, and also will make such a
tracing of the buzzard’s wing as Mr. Manly will show you of the “John Crow’s,” I shall be obliged.
My impression is that the buzzard is a considerably heavier bird than the “John Crow,” without,
however, very much greater spread of wing. I may observe that when the wings of the Jamaica bird
were spread out, they were spread quite to their utmost extent, and the distance between the tips of
the terminal feathers was much greater than when in flight. I wish you would kindly also add the
scientific name of the “John Crow,” with any particulars that you would think of interest.
If there be any special expenses incurred in the preparation of this memorandum, including the
time of a photographer, I will direct them to be paid from the Smithsonian fund. [p289]
Page 513
If you could get Mr. Holmes (who made most of the sketches and all of the photographs of the
“John Crow”), to try and do something like this for your buzzard, especially getting such a
photograph of it in flight, as will give the position of its center of gravity relative to the center of
pressure on the wings, it would add very greatly to the value of your memoranda, and I think Mr.
Holmes takes so full and intelligent an interest in the subject, that he might be pleased to give his
help.
Very truly yours,
S. P. LANGLEY,
Secretary.
MR. ROBERT RIDGWAY,
Smithsonian Institution,
Curator, Division of Ornithology, U. S. National Museum, Washington, D. C.
In response to this request, Mr. Ridgway submitted the following very
interesting information:
SMITHSONIAN INSTITUTION,
UNITED STATES NATIONAL MUSEUM
WASHINGTON, D. C., October 16, 1900.
PROF. S. P. LANGLEY,
Secretary, Smithsonian Institution.
SIR:
I have the honor of submitting herewith the data obtained by Mr. Rolla P. Currie concerning
measurements, etc., of the common Turkey Buzzard (Cathartes aura ) of the United States, as
requested by you in your letter of March 29, last.
The difficulties in the way of securing these data, already explained by me in previous
communications, are responsible for the delay in submitting them.
Hoping that this material may prove of use to you, I am,
Very respectfully,
R. RIDGWAY,
Curator, Division of Birds.
MEMORANDA IN REGARD TO THE TURKEY BUZZARD (SECOND SPECIMEN)
1. Weight.—1850 grammes.
2. Area of outstretched wings.—641 square inches. (Computed from three sheets of tracings, A1
and A2 comprising the entire area of both wings; B, a single wing.)
Note.—As the bird was in process of moult, one of the large wing quills, as shown by the
tracings and compo-board patterns, is but partially developed, thus slightly modifying the results
obtained. Its length, if full grown, would be nearly the same as that of the quill just above it.
3. Distance between the tips of these wings.—5 feet, 8.7 inches.
4. Distance between the tips of the same wings when the bird is in horizontal soaring flight.—
Estimating the dihedral angle of the wings to be 150°, and elevating the wings so as to make this
angle, the distance between their tips [p290] measures 5 feet, 5.7 inches, or 3 inches less than
when fully extended in the horizontal plane.
5. The position of the center of pressure of the wing.—This is indicated on two compo-board
patterns, C and D. C was made from a fully extended wing, while D was made from the wing in
the soaring position. The centers of pressure of the wings are about 2 feet, 0.5 inches apart, or 1
foot, 0.25 inches from the central point of the bird’s body.
“John Crow”), to try and do something like this for your buzzard, especially getting such a
photograph of it in flight, as will give the position of its center of gravity relative to the center of
pressure on the wings, it would add very greatly to the value of your memoranda, and I think Mr.
Holmes takes so full and intelligent an interest in the subject, that he might be pleased to give his
help.
Very truly yours,
S. P. LANGLEY,
Secretary.
MR. ROBERT RIDGWAY,
Smithsonian Institution,
Curator, Division of Ornithology, U. S. National Museum, Washington, D. C.
In response to this request, Mr. Ridgway submitted the following very
interesting information:
SMITHSONIAN INSTITUTION,
UNITED STATES NATIONAL MUSEUM
WASHINGTON, D. C., October 16, 1900.
PROF. S. P. LANGLEY,
Secretary, Smithsonian Institution.
SIR:
I have the honor of submitting herewith the data obtained by Mr. Rolla P. Currie concerning
measurements, etc., of the common Turkey Buzzard (Cathartes aura ) of the United States, as
requested by you in your letter of March 29, last.
The difficulties in the way of securing these data, already explained by me in previous
communications, are responsible for the delay in submitting them.
Hoping that this material may prove of use to you, I am,
Very respectfully,
R. RIDGWAY,
Curator, Division of Birds.
MEMORANDA IN REGARD TO THE TURKEY BUZZARD (SECOND SPECIMEN)
1. Weight.—1850 grammes.
2. Area of outstretched wings.—641 square inches. (Computed from three sheets of tracings, A1
and A2 comprising the entire area of both wings; B, a single wing.)
Note.—As the bird was in process of moult, one of the large wing quills, as shown by the
tracings and compo-board patterns, is but partially developed, thus slightly modifying the results
obtained. Its length, if full grown, would be nearly the same as that of the quill just above it.
3. Distance between the tips of these wings.—5 feet, 8.7 inches.
4. Distance between the tips of the same wings when the bird is in horizontal soaring flight.—
Estimating the dihedral angle of the wings to be 150°, and elevating the wings so as to make this
angle, the distance between their tips [p290] measures 5 feet, 5.7 inches, or 3 inches less than
when fully extended in the horizontal plane.
5. The position of the center of pressure of the wing.—This is indicated on two compo-board
patterns, C and D. C was made from a fully extended wing, while D was made from the wing in
the soaring position. The centers of pressure of the wings are about 2 feet, 0.5 inches apart, or 1
foot, 0.25 inches from the central point of the bird’s body.
Page 514
6. The position of the center of gravity of the soaring bird.—(Length of buzzard, 26 inches.) The
1
center of gravity of the soaring buzzard in the horizontal plane, CG1, was found to lie 9 2 inches
1
behind the tip of the beak and 16 2 inches in front of the tip of the tail.
The center of gravity of the soaring bird in the vertical plane, CG2, was found to lie 2.8 inches
above the ventral point of the body and 1.6 inches below the dorsal point, the depth of the bird’s
body at CG1, being 4.4 inches.
In determining the center of gravity, the bird was frozen in the soaring position, its wings
making a dihedral angle of 150°. It was then hung up, first horizontally and then vertically, and
balanced till the line from which it was suspended coincided with a plumb-line placed in front of
it; the measurements were then made.
The bird was afterwards, and while still frozen, hung up in the same way in Mr. Smillie’s
photographic room, and exposures made by him in both positions. These photographs, E1 and F1
were enlarged to natural size, and measurements made on the enlargements yielded, as nearly as
could be determined, the same results as when taken directly upon the bird.
As determined by measurements upon the buzzard in soaring position, the center of gravity was
found to be 2.65 inches below the center of pressure (estimating the center of pressure to be at the
bend of the wing); or, employing the compo-board pattern in a corresponding position, the distance
was seen to be a small fraction of an inch less.
7. The position of the root of the wing.—This is indicated on the tracing A1.
a. (Depth of the body on a vertical line with root, 3.5 inches.) The root lies 1.6 inches below
dorsal line, 1.9 inches above ventral line.
b. (Length of body, 26 inches.) The root lies 7.6 inches behind tip of beak, 18.4 inches in front
of tip of tail.
8. The dihedral angle between the wings.—The photographs taken previously were not
sufficiently large or distinct to enable us to determine this with exactness. It was estimated,
however, as 150°, and experiments were made on this basis.
9. The center of gravity of the dissected wing.—This was found, first, for the wing having all the
muscles, up to the ball and socket joint, intact. One of the wings was frozen in the soaring position
and its center of gravity found by balancing on a point. Its position was marked by a wire thrust
through the wing at this place, and the wing (H ) is preserved in formalin. This position is also
marked on a special tracing, I. It lies 6 inches from the base of the humerus bone (root of wing).
Secondly, it was found for the wing denuded of all muscle. Its position was marked on the other
3
wing of the bird, which is preserved dry, spread in the soaring position. It lies 9 4 inches from the
base of the humerus. [p291]
10. The weight of the dissected wing.—
a. With all muscle up to the ball and socket joint intact, 325 grammes.
b. With all muscle removed, 190 grammes.
Weight of muscle, therefore, 135 grammes.
The position of the root of the tail.—
a. In the horizontal plane, 11.8 inches in front of the tip of the longest tail feather; 14.2 inches
behind tip of beak.
b. In the vertical plane: (depth of body from ventral point below root of tail to a point directly
above, which is on a level with the highest point of the back, 2.5 inches.) 1.5 inches above ventral
point, 1 inch below dorsal point.
1
center of gravity of the soaring buzzard in the horizontal plane, CG1, was found to lie 9 2 inches
1
behind the tip of the beak and 16 2 inches in front of the tip of the tail.
The center of gravity of the soaring bird in the vertical plane, CG2, was found to lie 2.8 inches
above the ventral point of the body and 1.6 inches below the dorsal point, the depth of the bird’s
body at CG1, being 4.4 inches.
In determining the center of gravity, the bird was frozen in the soaring position, its wings
making a dihedral angle of 150°. It was then hung up, first horizontally and then vertically, and
balanced till the line from which it was suspended coincided with a plumb-line placed in front of
it; the measurements were then made.
The bird was afterwards, and while still frozen, hung up in the same way in Mr. Smillie’s
photographic room, and exposures made by him in both positions. These photographs, E1 and F1
were enlarged to natural size, and measurements made on the enlargements yielded, as nearly as
could be determined, the same results as when taken directly upon the bird.
As determined by measurements upon the buzzard in soaring position, the center of gravity was
found to be 2.65 inches below the center of pressure (estimating the center of pressure to be at the
bend of the wing); or, employing the compo-board pattern in a corresponding position, the distance
was seen to be a small fraction of an inch less.
7. The position of the root of the wing.—This is indicated on the tracing A1.
a. (Depth of the body on a vertical line with root, 3.5 inches.) The root lies 1.6 inches below
dorsal line, 1.9 inches above ventral line.
b. (Length of body, 26 inches.) The root lies 7.6 inches behind tip of beak, 18.4 inches in front
of tip of tail.
8. The dihedral angle between the wings.—The photographs taken previously were not
sufficiently large or distinct to enable us to determine this with exactness. It was estimated,
however, as 150°, and experiments were made on this basis.
9. The center of gravity of the dissected wing.—This was found, first, for the wing having all the
muscles, up to the ball and socket joint, intact. One of the wings was frozen in the soaring position
and its center of gravity found by balancing on a point. Its position was marked by a wire thrust
through the wing at this place, and the wing (H ) is preserved in formalin. This position is also
marked on a special tracing, I. It lies 6 inches from the base of the humerus bone (root of wing).
Secondly, it was found for the wing denuded of all muscle. Its position was marked on the other
3
wing of the bird, which is preserved dry, spread in the soaring position. It lies 9 4 inches from the
base of the humerus. [p291]
10. The weight of the dissected wing.—
a. With all muscle up to the ball and socket joint intact, 325 grammes.
b. With all muscle removed, 190 grammes.
Weight of muscle, therefore, 135 grammes.
The position of the root of the tail.—
a. In the horizontal plane, 11.8 inches in front of the tip of the longest tail feather; 14.2 inches
behind tip of beak.
b. In the vertical plane: (depth of body from ventral point below root of tail to a point directly
above, which is on a level with the highest point of the back, 2.5 inches.) 1.5 inches above ventral
point, 1 inch below dorsal point.
Page 515
Weight of tail.—With muscle, 40 grammes; without muscle, 30 grammes. Weight of muscle,
therefore, 10 grammes.
EXHIBITS ACCOMPANYING THESE MEMORANDA
E XHIBIT E 1 .—Turkey Buzzard suspended in soaring position.
(R. P. Currie.)
A1 and A2. Two sheets, comprising a tracing of the entire turkey buzzard with fully outstretched
wings. From these the area of the wings and the distance between their tips was obtained. The
position of the root of the wing and the root of the tail is also marked on one of these sheets.
B. One sheet, comprising a tracing of a single wing, and from which the area was also
computed. This area, multiplied by 2, gives the same result as the sum of both wings on A1 and A2.
The compo-board pattern C was made from this tracing.
C. Compo-board pattern of fully extended wing, on which the center of pressure is indicated.
D. Compo-board pattern of wing in soaring position, on which the center of pressure is shown.
[p292]
E1. Photograph of bird in soaring position, suspended horizontally.
E2. Same, enlarged to natural size.
F1. Photograph of bird in soaring position, suspended vertically.
F2. Same, enlarged to natural size.
G. Tracing of wing in soaring position, from which the compo-board pattern D was made.
therefore, 10 grammes.
EXHIBITS ACCOMPANYING THESE MEMORANDA
E XHIBIT E 1 .—Turkey Buzzard suspended in soaring position.
(R. P. Currie.)
A1 and A2. Two sheets, comprising a tracing of the entire turkey buzzard with fully outstretched
wings. From these the area of the wings and the distance between their tips was obtained. The
position of the root of the wing and the root of the tail is also marked on one of these sheets.
B. One sheet, comprising a tracing of a single wing, and from which the area was also
computed. This area, multiplied by 2, gives the same result as the sum of both wings on A1 and A2.
The compo-board pattern C was made from this tracing.
C. Compo-board pattern of fully extended wing, on which the center of pressure is indicated.
D. Compo-board pattern of wing in soaring position, on which the center of pressure is shown.
[p292]
E1. Photograph of bird in soaring position, suspended horizontally.
E2. Same, enlarged to natural size.
F1. Photograph of bird in soaring position, suspended vertically.
F2. Same, enlarged to natural size.
G. Tracing of wing in soaring position, from which the compo-board pattern D was made.
Page 516
E XHIBIT F 1 .—Turkey Buzzard suspended vertically in soaring position.
(R. P. Currie.)
(R. P. Currie.)
Page 517
H. Wing preserved in formalin, on which the center of gravity is recorded.
I. Tracing of wing H when frozen in soaring position, on which the center of gravity is marked.
J. Wing with muscle removed, on which the center of gravity is shown.
Several persons connected with the Smithsonian Institution and U. S. National Museum have
contributed towards securing the results herewith submitted. Among them, I desire especially to
mention Mr. W. H. Holmes, Mr. [p293] F. A. Lucas, Mr. N. R. Wood, and Mr. R. L. Reed. Mr.
Holmes superintended the experiments in connection with No. 6 (finding the bird’s center of
gravity), and by his suggestions and criticisms helped me in many other particulars. The
photographs and enlargements were made by Mr. T. W. Smillie.
Respectfully submitted,
ROLLA P. CURRIE,
Aid, Division of Insects, acting in the Division of Birds.
OCTOBER 16, 1900.
The feats of airmanship performed by the “John Crow” seemed to greatly
impress Mr. Langley and shortly after this trip he wrote the following letter
to the writer:
SMITHSONIAN INSTITUTION
WASHINGTON, D. C., April 16, 1900.
DEAR MR. MANLY:
I am reminded of the consequence that I have, in connection with Mr. Chanute and perhaps Mr.
Huffaker, attached in the past to the possibility of directing the bird, and consequently the flying
machine, by the mere inflection of the wing, that is, by changing its angle; and you recall to me
that Mr. Huffaker at one time proposed to arrange a wing, with some provision of a spring, which
should enable it to change its angle automatically. . . . .
I have been noting this ability to guide by the slight inflection of the wing, in my studies of the
Jamaica buzzard, and am ready to say that I think, while the quarter-sized working model of the
great aerodrome is building, it will be worth while to make some arrangement of the frame or
wing-holder which will make it possible to test this idea. I will endeavor to work out something of
the kind more in detail myself, but whatever it is, it will apparently involve the ability of the wing
to rotate about a line passing nearly through it lengthwise, and an allowance for this; if not in the
wing itself, then in the wing-holder; will need to be made while the present model is under
construction.
I will request you to especially look out for this, as far as you can on these indications.
Very respectfully yours,
S. P. LANGLEY,
Secretary.
The instructions and suggestions contained in this letter and in many
conferences on the subject were never carried out by the writer, on account
of the extreme pressure of the work already on him which had for its object,
not the production of a flying machine which would embody all of the
control which we wished it to have, but which would be burdened only with
I. Tracing of wing H when frozen in soaring position, on which the center of gravity is marked.
J. Wing with muscle removed, on which the center of gravity is shown.
Several persons connected with the Smithsonian Institution and U. S. National Museum have
contributed towards securing the results herewith submitted. Among them, I desire especially to
mention Mr. W. H. Holmes, Mr. [p293] F. A. Lucas, Mr. N. R. Wood, and Mr. R. L. Reed. Mr.
Holmes superintended the experiments in connection with No. 6 (finding the bird’s center of
gravity), and by his suggestions and criticisms helped me in many other particulars. The
photographs and enlargements were made by Mr. T. W. Smillie.
Respectfully submitted,
ROLLA P. CURRIE,
Aid, Division of Insects, acting in the Division of Birds.
OCTOBER 16, 1900.
The feats of airmanship performed by the “John Crow” seemed to greatly
impress Mr. Langley and shortly after this trip he wrote the following letter
to the writer:
SMITHSONIAN INSTITUTION
WASHINGTON, D. C., April 16, 1900.
DEAR MR. MANLY:
I am reminded of the consequence that I have, in connection with Mr. Chanute and perhaps Mr.
Huffaker, attached in the past to the possibility of directing the bird, and consequently the flying
machine, by the mere inflection of the wing, that is, by changing its angle; and you recall to me
that Mr. Huffaker at one time proposed to arrange a wing, with some provision of a spring, which
should enable it to change its angle automatically. . . . .
I have been noting this ability to guide by the slight inflection of the wing, in my studies of the
Jamaica buzzard, and am ready to say that I think, while the quarter-sized working model of the
great aerodrome is building, it will be worth while to make some arrangement of the frame or
wing-holder which will make it possible to test this idea. I will endeavor to work out something of
the kind more in detail myself, but whatever it is, it will apparently involve the ability of the wing
to rotate about a line passing nearly through it lengthwise, and an allowance for this; if not in the
wing itself, then in the wing-holder; will need to be made while the present model is under
construction.
I will request you to especially look out for this, as far as you can on these indications.
Very respectfully yours,
S. P. LANGLEY,
Secretary.
The instructions and suggestions contained in this letter and in many
conferences on the subject were never carried out by the writer, on account
of the extreme pressure of the work already on him which had for its object,
not the production of a flying machine which would embody all of the
control which we wished it to have, but which would be burdened only with
Page 518
such devices and arrangements as would enable it to transport a human
being, and thus demonstrate the practicability of human flight.
[p294]
S E C RE TA RY L ANGL E Y ’ S I N S T R UC T I ON S TO
A S S I S TANT S
SMITHSONIAN INSTITUTION, WASHINGTON, D. C., November 30, 1895.
DEAR SIR:
The following instructions are to replace those of May 13, 1895:
1. The minimum fraction of its own “flying weight” (that is, weight complete with initial water
and fuel), which the aerodrome shall lift on the pendulum, is 50 percent,50 under such engine
power as can certainly be gotten up in the field and maintained during forty seconds from the time
the aerodrome is let go.
The blast, the pumps, and all other essential parts must, in other words, be in such a condition
that steam enough for this lifting over 50 per cent of weight can be gotten up readily and surely in
the field and in a time which will still leave at least forty seconds’ supply.
2. The minimum relation of supporting area to weight in any aerodrome constructed hereafter, is
to be two feet to the pound,50 and the minimum of power at the rate of one steadily-maintained
horse power50 at the brake under ordinary conditions, to not over twenty-two pounds (ten kilos) of
flying weight. In absence of a brake determination horse power may be taken—
H. P. =
revs. per min. at rest × pitch × diameter (in ft.) × thrust (in lbs.)
.
33,000
These rules do not apply to No. 5, but they do to No. 6, which is to be built over, if necessary, to
meet them.
3. In balancing an aerodrome, unless otherwise instructed, set wings at a root angle of either
10°, 7°, or 5°, after being certain from previous inversion and sanding, that the tip angle in motion
will not differ from this root angle as much as 5°.
The object in balancing any aerodrome with a single pair of wings is to be able to bring the c g2
under their c p2 without any reference to the tail, which supports nothing, unless specially ordered.
But as this condition cannot now be obtained in Nos. 5 and 6, these at any rate, and perhaps future
aerodromes, are to carry a second pair of wings. When this second pair of wings is of nearly equal
size with the first it is to be assumed in preliminary adjustments for weight and center of pressure,
that the second pair has two-thirds the lifting efficiency per unit area of the first.
Calling the whole distance from the mean center of pressure of the wings to the center of gravity
M. M is to have a definite relation to the breadth of [p295] wings from tip to tip (b ) and total fore
√(bl)
and aft length (1), which is provisionally fixed at M = 8 , and the line of thrust is to be not over
one-fourth the way from c p2 to c g2.
Generally speaking the front pair of wings will be fixed in position and the adjustment for
balancing made by moving the rear pair.
The individual weights of all parts checked by lump weighing are to be given by the caretaker
(Mr. Huffaker), under the general scheme shown in the note. The work on the aerodromes being
being, and thus demonstrate the practicability of human flight.
[p294]
S E C RE TA RY L ANGL E Y ’ S I N S T R UC T I ON S TO
A S S I S TANT S
SMITHSONIAN INSTITUTION, WASHINGTON, D. C., November 30, 1895.
DEAR SIR:
The following instructions are to replace those of May 13, 1895:
1. The minimum fraction of its own “flying weight” (that is, weight complete with initial water
and fuel), which the aerodrome shall lift on the pendulum, is 50 percent,50 under such engine
power as can certainly be gotten up in the field and maintained during forty seconds from the time
the aerodrome is let go.
The blast, the pumps, and all other essential parts must, in other words, be in such a condition
that steam enough for this lifting over 50 per cent of weight can be gotten up readily and surely in
the field and in a time which will still leave at least forty seconds’ supply.
2. The minimum relation of supporting area to weight in any aerodrome constructed hereafter, is
to be two feet to the pound,50 and the minimum of power at the rate of one steadily-maintained
horse power50 at the brake under ordinary conditions, to not over twenty-two pounds (ten kilos) of
flying weight. In absence of a brake determination horse power may be taken—
H. P. =
revs. per min. at rest × pitch × diameter (in ft.) × thrust (in lbs.)
.
33,000
These rules do not apply to No. 5, but they do to No. 6, which is to be built over, if necessary, to
meet them.
3. In balancing an aerodrome, unless otherwise instructed, set wings at a root angle of either
10°, 7°, or 5°, after being certain from previous inversion and sanding, that the tip angle in motion
will not differ from this root angle as much as 5°.
The object in balancing any aerodrome with a single pair of wings is to be able to bring the c g2
under their c p2 without any reference to the tail, which supports nothing, unless specially ordered.
But as this condition cannot now be obtained in Nos. 5 and 6, these at any rate, and perhaps future
aerodromes, are to carry a second pair of wings. When this second pair of wings is of nearly equal
size with the first it is to be assumed in preliminary adjustments for weight and center of pressure,
that the second pair has two-thirds the lifting efficiency per unit area of the first.
Calling the whole distance from the mean center of pressure of the wings to the center of gravity
M. M is to have a definite relation to the breadth of [p295] wings from tip to tip (b ) and total fore
√(bl)
and aft length (1), which is provisionally fixed at M = 8 , and the line of thrust is to be not over
one-fourth the way from c p2 to c g2.
Generally speaking the front pair of wings will be fixed in position and the adjustment for
balancing made by moving the rear pair.
The individual weights of all parts checked by lump weighing are to be given by the caretaker
(Mr. Huffaker), under the general scheme shown in the note. The work on the aerodromes being
Page 519
divided into two classes, viz.: metal work and all which is not metal, the two in charge of this work
(Mr. Reed and Mr. Maltby) are severally responsible for knowing the weight in grammes of any of
the parts they have put into their work, giving these weights to Mr. Huffaker, together with any
data for filling out the annexed tables,51 on his request.
Until further orders, Mr. Huffaker is charged with the responsibility of seeing that these
conditions are met before any aerodrome is boxed, and will keep the record of weights of the
aerodromes and their principal parts as already completed, in a book, to be preserved in your
keeping, which will also be arranged to show with signed photographs and descriptions, and with
sketches where needed, the condition and weight (as far as constructed) of every aerodrome, and
of any new construction of any part, on the first of each month.
Particular attention is directed to the preceding paragraph, and to the need that evidence of a
definite character is to be obtained and preserved of everything already done, and being done.
Without special orders to the contrary, you will not authorize the boxing of any aerodrome
which does not, to your knowledge, meet these conditions.
Each aerodrome is to have the following parts in duplicate or in triplicate:
2 pairs wings;
2 pairs tails;
2 pairs light silk covered rudders;
3 pairs wheels;
with any other parts in duplicate or triplicate, which experience has shown to be necessary.
Mr. Reed will not box any aerodrome till a certificate from Mr. Huffaker can be put on the
inside cover, with the list of contents, showing what the conditions are as to weight, wing area,
power, etc., and the person in the field charged with the duty of launching the aerodrome (at
present Mr. Reed), is authorized not to let it go unless he is satisfied that it has a full forty seconds’
supply of steam. [p296]
I am satisfied that a great deal of time is lost in putting the aerodrome together for flight, owing
to the absence of any preliminary drill in doing this. Before it goes into the field the whole is to be
completely boxed, and then taken out from the box and set up on the clutch, and steam gotten up
for flight. All this is to be done in the shop before the final boxing, and provision is to be made so
that no wiring or adjusting of parts is to be done in the field which can possibly be avoided by
forethought in the shop. The tail-piece, for instance, is to be bushed with brass, so that it will
always come into the same place, and make a tight fit, in spite of wetting or shrinking, in the steel
tube, where it is to go into a guide-way with a bayonet spring, or a like contrivance for setting it at
once securely into position.
(Mr. Reed and Mr. Maltby) are severally responsible for knowing the weight in grammes of any of
the parts they have put into their work, giving these weights to Mr. Huffaker, together with any
data for filling out the annexed tables,51 on his request.
Until further orders, Mr. Huffaker is charged with the responsibility of seeing that these
conditions are met before any aerodrome is boxed, and will keep the record of weights of the
aerodromes and their principal parts as already completed, in a book, to be preserved in your
keeping, which will also be arranged to show with signed photographs and descriptions, and with
sketches where needed, the condition and weight (as far as constructed) of every aerodrome, and
of any new construction of any part, on the first of each month.
Particular attention is directed to the preceding paragraph, and to the need that evidence of a
definite character is to be obtained and preserved of everything already done, and being done.
Without special orders to the contrary, you will not authorize the boxing of any aerodrome
which does not, to your knowledge, meet these conditions.
Each aerodrome is to have the following parts in duplicate or in triplicate:
2 pairs wings;
2 pairs tails;
2 pairs light silk covered rudders;
3 pairs wheels;
with any other parts in duplicate or triplicate, which experience has shown to be necessary.
Mr. Reed will not box any aerodrome till a certificate from Mr. Huffaker can be put on the
inside cover, with the list of contents, showing what the conditions are as to weight, wing area,
power, etc., and the person in the field charged with the duty of launching the aerodrome (at
present Mr. Reed), is authorized not to let it go unless he is satisfied that it has a full forty seconds’
supply of steam. [p296]
I am satisfied that a great deal of time is lost in putting the aerodrome together for flight, owing
to the absence of any preliminary drill in doing this. Before it goes into the field the whole is to be
completely boxed, and then taken out from the box and set up on the clutch, and steam gotten up
for flight. All this is to be done in the shop before the final boxing, and provision is to be made so
that no wiring or adjusting of parts is to be done in the field which can possibly be avoided by
forethought in the shop. The tail-piece, for instance, is to be bushed with brass, so that it will
always come into the same place, and make a tight fit, in spite of wetting or shrinking, in the steel
tube, where it is to go into a guide-way with a bayonet spring, or a like contrivance for setting it at
once securely into position.
Page 520
The mean positions of the wings and tail are to be laid out in some way permanently on the mid-
rod, but every guy-rod or adjustable piece is to be arranged so as to fit at once securely and
permanently in its position without wiring or like slow process.
Very truly yours,
S. P. LANGLEY,
Secretary.
W. C. WINLOCK, Esq.,
Assistant in Charge,
Smithsonian Institution.
A copy to be communicated to:——Mr. Huffaker,
Mr. Reed,
Mr. Maltby.
rod, but every guy-rod or adjustable piece is to be arranged so as to fit at once securely and
permanently in its position without wiring or like slow process.
Very truly yours,
S. P. LANGLEY,
Secretary.
W. C. WINLOCK, Esq.,
Assistant in Charge,
Smithsonian Institution.
A copy to be communicated to:——Mr. Huffaker,
Mr. Reed,
Mr. Maltby.
Page 521
FOOTNOTES.
[37] “The Flying Machine” McClure’s Magazine, June, 1897.
[38] One noted astronomer and mathematician re-affirmed this opinion as late as 1900 and
even stated that man could not hope to construct a flying machine capable of sustaining a weight
as great as our largest birds, knowing that even at that time the model Aerodromes Nos. 5 and 6
had already done more than this.
[39] These wings are described in Chapter VI, pp. 191.
[40] See “Experiments in Aerodynamics.” It will be recalled that in the experiments with the
“plane-dropper” there was a greatly reduced lifting power with superposed planes when their
distance apart was one-half the width the planes, unless a speed of about 42.5 feet a second was
obtained. In the above tests with the superposed wings, the speed was only from twenty to twenty-
two feet a second at the time of launching, and as the distance between the surfaces was only one-
half as great as their width, it is not surprising that the lifting power should not be as great as with
the “single-tier” wings.
[41] In fact the setting of the tail at a negative angle and fastening it to the frame by an elastic
or spring connection was only begun in 1896, and while it proved to be the key to the solution of
the problem of automatic longitudinal stability, yet it was not at that time so recognized, although
the first real test of the aerodromes after the elastic connection and negative angle of the tail were
adopted resulted in the epoch-making flight of No. 5 on May 6. By comparing the angle of the tail
on No. 5 in Plate 27A, Part I, with the angle of the tail on No. 6 in Plate 27B, Part I, it will be seen
that while the first had an angle of much less than 5 degrees, the latter had an angle of about 15
degrees. But the wooden springs changed so that it was not accurately known what the angle really
was at the time at either flight in 1896.
[42] The drawings, Plate 55, which illustrate many of the fittings used on the frame, show the
guy-wires as attached by means of loops twisted in their ends, these drawings having been made
before the final plan of attaching the wires had been devised.
[43] See explanation of system of locating points in Part I, Chap. II, p. 15.
[44] See Balancing of Engines, by Archibald Sharpe.
[45] Except for a ten minute stop to renew the supply of lubricating oil and change the
sparking batteries.
[46] See foot-note, page 249.
[47] The weight was afterwards increased to 850 pounds due to repairing the wings and
adding more sparking batteries.
[48] See Experiments in Aerodynamics, Smithsonian Contributions to Knowledge, Vol. 27,
Washington 1891.
[49] Researches and Experiments in Aerial Navigation, Smithsonian Publication No. 1809,
Washington, 1908.
[37] “The Flying Machine” McClure’s Magazine, June, 1897.
[38] One noted astronomer and mathematician re-affirmed this opinion as late as 1900 and
even stated that man could not hope to construct a flying machine capable of sustaining a weight
as great as our largest birds, knowing that even at that time the model Aerodromes Nos. 5 and 6
had already done more than this.
[39] These wings are described in Chapter VI, pp. 191.
[40] See “Experiments in Aerodynamics.” It will be recalled that in the experiments with the
“plane-dropper” there was a greatly reduced lifting power with superposed planes when their
distance apart was one-half the width the planes, unless a speed of about 42.5 feet a second was
obtained. In the above tests with the superposed wings, the speed was only from twenty to twenty-
two feet a second at the time of launching, and as the distance between the surfaces was only one-
half as great as their width, it is not surprising that the lifting power should not be as great as with
the “single-tier” wings.
[41] In fact the setting of the tail at a negative angle and fastening it to the frame by an elastic
or spring connection was only begun in 1896, and while it proved to be the key to the solution of
the problem of automatic longitudinal stability, yet it was not at that time so recognized, although
the first real test of the aerodromes after the elastic connection and negative angle of the tail were
adopted resulted in the epoch-making flight of No. 5 on May 6. By comparing the angle of the tail
on No. 5 in Plate 27A, Part I, with the angle of the tail on No. 6 in Plate 27B, Part I, it will be seen
that while the first had an angle of much less than 5 degrees, the latter had an angle of about 15
degrees. But the wooden springs changed so that it was not accurately known what the angle really
was at the time at either flight in 1896.
[42] The drawings, Plate 55, which illustrate many of the fittings used on the frame, show the
guy-wires as attached by means of loops twisted in their ends, these drawings having been made
before the final plan of attaching the wires had been devised.
[43] See explanation of system of locating points in Part I, Chap. II, p. 15.
[44] See Balancing of Engines, by Archibald Sharpe.
[45] Except for a ten minute stop to renew the supply of lubricating oil and change the
sparking batteries.
[46] See foot-note, page 249.
[47] The weight was afterwards increased to 850 pounds due to repairing the wings and
adding more sparking batteries.
[48] See Experiments in Aerodynamics, Smithsonian Contributions to Knowledge, Vol. 27,
Washington 1891.
[49] Researches and Experiments in Aerial Navigation, Smithsonian Publication No. 1809,
Washington, 1908.
Page 522
[50] All these minimum permissible conditions are connected by the tacit assumption that the
supporting area is not greatly over 2 ft. to the pound of weight. If for instance the weight were
increased by larger wings or more wings, furnishing a much greater supporting area per pound,
these conditions would not necessarily apply.
[51] These tables were later designated as “Data Sheets.” Several copies, with the data duly
entered on them, are given in this appendix, and the form which Mr. Langley included in this letter
is therefore not repeated here.—EDITOR.
supporting area is not greatly over 2 ft. to the pound of weight. If for instance the weight were
increased by larger wings or more wings, furnishing a much greater supporting area per pound,
these conditions would not necessarily apply.
[51] These tables were later designated as “Data Sheets.” Several copies, with the data duly
entered on them, are given in this appendix, and the form which Mr. Langley included in this letter
is therefore not repeated here.—EDITOR.
Page 523
[p297] ◊
DATA SHEETS.
DATA S HE E T No. 1.
We i g h t o f A e r o d r o m e N o . 5 , a s p h o t o g r a p h e d o n M a y 11 , 1 8 9 6 . C e r t i f i e d
to by R. L. Reed, May 6, 1896.
Sizes. Weight.
Parts.
m. ft. gr. lbs.
1 Frame, including everything of metal, permanent and undetachable, such
as bed-plate, cross-rods for the support of propellers, bearing points for 2443
clutch, etc.
2 Engine, gears, shafts, etc. 1110
3 Pump, pump shaft 231
4 Hull covering 350
5 Gasoline tanks, valves 178
6 Smokestack 342
7 Float 275
8 Reel 77
9 Wing clamps, 235; clamp for guy-posts, 29 264
10 Other things, counter 75
11 Burners 360
12 Boilers 651
13 Separators, steam gauge, pipe to engine 540
14 Exhaust pipe 143
15
16
17 Wings (without clamp) 1950
18 Tail (without clamp)
19 Rudder 350
20 Guy sticks, each, 57 114
21 Propellers 800
22 Extra length of midrod, 308; drop piece for rudder, 40 348
23 Wood Bowsprit 74
24 Other things
25
26
27 Fuel (at starting flight) 200
28 Water (at starting flight) 900
29
30
DATA SHEETS.
DATA S HE E T No. 1.
We i g h t o f A e r o d r o m e N o . 5 , a s p h o t o g r a p h e d o n M a y 11 , 1 8 9 6 . C e r t i f i e d
to by R. L. Reed, May 6, 1896.
Sizes. Weight.
Parts.
m. ft. gr. lbs.
1 Frame, including everything of metal, permanent and undetachable, such
as bed-plate, cross-rods for the support of propellers, bearing points for 2443
clutch, etc.
2 Engine, gears, shafts, etc. 1110
3 Pump, pump shaft 231
4 Hull covering 350
5 Gasoline tanks, valves 178
6 Smokestack 342
7 Float 275
8 Reel 77
9 Wing clamps, 235; clamp for guy-posts, 29 264
10 Other things, counter 75
11 Burners 360
12 Boilers 651
13 Separators, steam gauge, pipe to engine 540
14 Exhaust pipe 143
15
16
17 Wings (without clamp) 1950
18 Tail (without clamp)
19 Rudder 350
20 Guy sticks, each, 57 114
21 Propellers 800
22 Extra length of midrod, 308; drop piece for rudder, 40 348
23 Wood Bowsprit 74
24 Other things
25
26
27 Fuel (at starting flight) 200
28 Water (at starting flight) 900
29
30
Page 524
Sizes. Weight.
Parts.
m. ft. gr. lbs.
31 Sundries unknown
32
33
34 Total flying weight 11,775 26
35
36
37
38 Total area of support (not including tail) . . . sq. ft. 68
39 Total area of support in feet, divided by total flying weight in lbs. 2.6
40 Total area of horizontal tail . . . sq. ft.
41 Total area of rudder (vertical) . . . sq. ft. 6
42 Horse-power at brake. Horse-power by formula* .72 7
43 Minimum pressure during 40 secs. lift, 150 lbs.
44 Lift at pendulum (during 40 secs. absolute) 5772
45 Lift at pendulum (during 40 secs. in terms of wt.) 49%
46 Minimum pressure with which wheels turn, 10 lbs.
47 Position of center of pressure of wings† F. W., 1575; R. W., 1383.5
48 Time of getting up full steam, 1 minute
49
50 Curvature of wings, 1/11
51 Root angle of wings, 9°
52 Tip angle of wings, 9°
53 Position of wings, Front rib on F. W., 1607; R. W., 1415.5
54 How guyed
55
56
57
58 Position of tail
59 Angle of tail
60 Co-efficient elasticity of tail
61 Position of rudder, center, 1288.3; rear end, 1229.8
62 Line of thrust, 2500
63 Line of thrust, 1500 which is 9 cm. below the center of midrod
64 Center of gravity1 of whole, 1497
65 Center of gravity2 2501, i. e., 1 cm. above line of thrust
66 Center of pressure1 of whole estimate, 1498
67 Center of pressure2, 2536
68
69
70
Parts.
m. ft. gr. lbs.
31 Sundries unknown
32
33
34 Total flying weight 11,775 26
35
36
37
38 Total area of support (not including tail) . . . sq. ft. 68
39 Total area of support in feet, divided by total flying weight in lbs. 2.6
40 Total area of horizontal tail . . . sq. ft.
41 Total area of rudder (vertical) . . . sq. ft. 6
42 Horse-power at brake. Horse-power by formula* .72 7
43 Minimum pressure during 40 secs. lift, 150 lbs.
44 Lift at pendulum (during 40 secs. absolute) 5772
45 Lift at pendulum (during 40 secs. in terms of wt.) 49%
46 Minimum pressure with which wheels turn, 10 lbs.
47 Position of center of pressure of wings† F. W., 1575; R. W., 1383.5
48 Time of getting up full steam, 1 minute
49
50 Curvature of wings, 1/11
51 Root angle of wings, 9°
52 Tip angle of wings, 9°
53 Position of wings, Front rib on F. W., 1607; R. W., 1415.5
54 How guyed
55
56
57
58 Position of tail
59 Angle of tail
60 Co-efficient elasticity of tail
61 Position of rudder, center, 1288.3; rear end, 1229.8
62 Line of thrust, 2500
63 Line of thrust, 1500 which is 9 cm. below the center of midrod
64 Center of gravity1 of whole, 1497
65 Center of gravity2 2501, i. e., 1 cm. above line of thrust
66 Center of pressure1 of whole estimate, 1498
67 Center of pressure2, 2536
68
69
70
Page 525
Sizes. Weight.
Parts.
m. ft. gr. lbs.
71
72
Parts.
m. ft. gr. lbs.
71
72
Page 526
Parts. Remarks.
1 Front end of bowsprit, 1686.3.
2 Front end of midrod, 1611.6.
5 Front edge of F. W., 1607.
8 C. of P. on F. W., 1575.
11 Back edge of F. W., 1527.
14 Back edge of cross frame, 1509.
17 Line through center of propellers, 1500.
21 C. of G., 1497.
24 Front edge of R. W., 1415.5.
27 C. of P. on R. W., 1383.5.
30 End of mid-rod, 1360.5.
33 Front end of rudder, 1343.8.
36 Back edge of R. W., 1335.5.
39 Center of rudder, 1288.3.
41 Back end of rudder, 1229.8.
Footnotes.
* H. P. = (Rev. × diam. × pitch ratio × thrust)/33000
† This is calculated on the assumption that the center of pressure on each wing or on pair of
wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from
front to rear, that for wings of usual size the rear wings have 2-3 of the efficiency per surface
of the front ones and that the tail proper bears no part of the weight; but if rear wing is
smaller or larger this efficiency is smaller or larger per unit of surface.
1 Front end of bowsprit, 1686.3.
2 Front end of midrod, 1611.6.
5 Front edge of F. W., 1607.
8 C. of P. on F. W., 1575.
11 Back edge of F. W., 1527.
14 Back edge of cross frame, 1509.
17 Line through center of propellers, 1500.
21 C. of G., 1497.
24 Front edge of R. W., 1415.5.
27 C. of P. on R. W., 1383.5.
30 End of mid-rod, 1360.5.
33 Front end of rudder, 1343.8.
36 Back edge of R. W., 1335.5.
39 Center of rudder, 1288.3.
41 Back end of rudder, 1229.8.
Footnotes.
* H. P. = (Rev. × diam. × pitch ratio × thrust)/33000
† This is calculated on the assumption that the center of pressure on each wing or on pair of
wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from
front to rear, that for wings of usual size the rear wings have 2-3 of the efficiency per surface
of the front ones and that the tail proper bears no part of the weight; but if rear wing is
smaller or larger this efficiency is smaller or larger per unit of surface.
Page 527
[p298]
DATA S HE E T No. 2.
We i g h t o f A e r o d r o m e N o . 6 . C e r t i f i e d t o b y R . L . R e e d , N o v e m b e r 2 7 a n d
28, 1896.
Sizes. Weight.
Parts.
m. ft. gr. lbs.
1 Frame, including everything of metal, permanent and undetachable,
such as bed-plate, cross-rods for the support of propellers, bearing 1178
points for clutch, etc.
2 Engine, gears, shafts, etc. 1043
3 Pump, pump shaft 190
4 Hull covering 345
5 Gasoline tanks, valves 306
6 Smokestack, 302; burner, 172 474
7 Float 275
8 Reel 77
9 Wing clamps, 238; drop piece for rudder, 40 278
10 Other things 156
11 Boiler, frames, mica cover 694
12 Separator, steam gauge, pipe to engines 535
13 Exhaust pipe 82
14
15
16
17 Wings (without clamp), wet 2154
18 Tail (without clamp)
19 Rudder 375
20 Guy sticks, each 53 106
21 Propellers 644
22 Extra length of midrod 398
23 Wood bowsprit 135
24 Counter 75
25
26
27 Fuel (at starting flight) 250
28 Water (at starting flight) 2350
29
30
31 Sundries unknown
32
33
DATA S HE E T No. 2.
We i g h t o f A e r o d r o m e N o . 6 . C e r t i f i e d t o b y R . L . R e e d , N o v e m b e r 2 7 a n d
28, 1896.
Sizes. Weight.
Parts.
m. ft. gr. lbs.
1 Frame, including everything of metal, permanent and undetachable,
such as bed-plate, cross-rods for the support of propellers, bearing 1178
points for clutch, etc.
2 Engine, gears, shafts, etc. 1043
3 Pump, pump shaft 190
4 Hull covering 345
5 Gasoline tanks, valves 306
6 Smokestack, 302; burner, 172 474
7 Float 275
8 Reel 77
9 Wing clamps, 238; drop piece for rudder, 40 278
10 Other things 156
11 Boiler, frames, mica cover 694
12 Separator, steam gauge, pipe to engines 535
13 Exhaust pipe 82
14
15
16
17 Wings (without clamp), wet 2154
18 Tail (without clamp)
19 Rudder 375
20 Guy sticks, each 53 106
21 Propellers 644
22 Extra length of midrod 398
23 Wood bowsprit 135
24 Counter 75
25
26
27 Fuel (at starting flight) 250
28 Water (at starting flight) 2350
29
30
31 Sundries unknown
32
33
Page 528
Sizes. Weight.
Parts.
m. ft. gr. lbs.
34 Total flying weight 12,120
35
36
37
38 Total area of support (not including tail) . . . sq. ft. 54
39 Total area of support in feet, divided by total flying weight in lbs. 2
40 Total area of horizontal tail . . . sq. ft. .6
41 Total area of rudder (vertical) . . . sq. ft. .6
42 Horse-power at brake. . .Horse-power by formula*
43 Minimum steam pressure during 40 secs. lift 130
44 Lift at pendulum (during one minute absolute) 7,211
45 Lift at pendulum (during one minute in terms of wt.)
46 Minimum pressure with which wheels turn 10
47 Position of center of pressure of wings†
48 Time of getting up full steam, 75 secs.
49 Angle of midrod with horizon, 2° 17′
50 Curvature of wings, 1 in 18, 1/4 from front
51 Root angle of wings, 10° 30′
52 Tip angle of wings, 10° 30′
53 Position of wings
54 How guyed
55
56
57
58 Position of tail
59 Angle of tail
60 Co-efficient elasticity of tail
61 Position of rudder
62
63 Line of thrust 1500
64 Center of gravity1 of whole, 1483.8
65 Center of gravity2, 2482‡
66 Center of pressure1 of whole estimate, 1487
67 Center of pressure2, 2520
68
69
70
71
72
Parts.
m. ft. gr. lbs.
34 Total flying weight 12,120
35
36
37
38 Total area of support (not including tail) . . . sq. ft. 54
39 Total area of support in feet, divided by total flying weight in lbs. 2
40 Total area of horizontal tail . . . sq. ft. .6
41 Total area of rudder (vertical) . . . sq. ft. .6
42 Horse-power at brake. . .Horse-power by formula*
43 Minimum steam pressure during 40 secs. lift 130
44 Lift at pendulum (during one minute absolute) 7,211
45 Lift at pendulum (during one minute in terms of wt.)
46 Minimum pressure with which wheels turn 10
47 Position of center of pressure of wings†
48 Time of getting up full steam, 75 secs.
49 Angle of midrod with horizon, 2° 17′
50 Curvature of wings, 1 in 18, 1/4 from front
51 Root angle of wings, 10° 30′
52 Tip angle of wings, 10° 30′
53 Position of wings
54 How guyed
55
56
57
58 Position of tail
59 Angle of tail
60 Co-efficient elasticity of tail
61 Position of rudder
62
63 Line of thrust 1500
64 Center of gravity1 of whole, 1483.8
65 Center of gravity2, 2482‡
66 Center of pressure1 of whole estimate, 1487
67 Center of pressure2, 2520
68
69
70
71
72
Page 529
Parts. Remarks.
1 Front end of bowsprit, 1797.
2 Center of float in first trial, Nov.
6 Front end of midrod, 1613.7. 9 Front edge of F. W., 1595.7.
12 Center of float in flight, Nov. 28, 1896, 1575.8.
16 C. of P. on F. W., 1563.7.
19 Back edge of F. W., 1515.7.
22 Line through center
of propellers, 1500.
26 C. of G., 1484.4 (old C. of G., 1486.3).
29 Front edge of R. W., 1406.
32 C. of P. on R. W., 1374.
35 End of midrod, 1351.3
38 Front end of rudder, 1334.5.
41 Back edge of R. W., 1326.
43 Center of rudder, 1279.
46 Back end of rudder, 1220.5.
49 Reed wings, 80 cm. × 185 cm. in rectangle.
53 Weight in shop, 1982 g.
56 On day of flight they weighed 2154 g. because they were damp.
60 Area 54 sq. ft.
3
63 Spread of wings, 359 cms. or 11′ 9 8 ″.
67 Weight of aerodrome in flight, 12,120 grs.
Footnotes.
* H. P. = (Rev. × diam. × pitch ratio × thrust)/33000
† This is calculated on the assumption that the center of pressure on each wing or on pair of
wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from
front to rear, that for wings of usual size the rear wings have 2-3 of the efficiency per surface
of the front ones and that the tail proper bears no part of the weight; but if rear wing is
smaller or larger this efficiency is smaller or larger per unit of surface.
‡ This is undoubtedly incorrect, as if it were true, the C. G. would be just at the center of the
separator, and this would be impossible. Mr. Reed states that the C. G. was 2 cm. below the
side frame, and if this is correct, we would have C. G. = 2486.
1 Front end of bowsprit, 1797.
2 Center of float in first trial, Nov.
6 Front end of midrod, 1613.7. 9 Front edge of F. W., 1595.7.
12 Center of float in flight, Nov. 28, 1896, 1575.8.
16 C. of P. on F. W., 1563.7.
19 Back edge of F. W., 1515.7.
22 Line through center
of propellers, 1500.
26 C. of G., 1484.4 (old C. of G., 1486.3).
29 Front edge of R. W., 1406.
32 C. of P. on R. W., 1374.
35 End of midrod, 1351.3
38 Front end of rudder, 1334.5.
41 Back edge of R. W., 1326.
43 Center of rudder, 1279.
46 Back end of rudder, 1220.5.
49 Reed wings, 80 cm. × 185 cm. in rectangle.
53 Weight in shop, 1982 g.
56 On day of flight they weighed 2154 g. because they were damp.
60 Area 54 sq. ft.
3
63 Spread of wings, 359 cms. or 11′ 9 8 ″.
67 Weight of aerodrome in flight, 12,120 grs.
Footnotes.
* H. P. = (Rev. × diam. × pitch ratio × thrust)/33000
† This is calculated on the assumption that the center of pressure on each wing or on pair of
wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from
front to rear, that for wings of usual size the rear wings have 2-3 of the efficiency per surface
of the front ones and that the tail proper bears no part of the weight; but if rear wing is
smaller or larger this efficiency is smaller or larger per unit of surface.
‡ This is undoubtedly incorrect, as if it were true, the C. G. would be just at the center of the
separator, and this would be impossible. Mr. Reed states that the C. G. was 2 cm. below the
side frame, and if this is correct, we would have C. G. = 2486.
Page 530
[p299]
DATA S HE E T No. 3.
We i g h t o f A e r o d r o m e N o . 6 , F l a t Wi n g s a n d P é n a u d R u d d e r. C e r t i f i e d t o
b y C h a s . M . M a n l y, J u n e 7 , 1 8 9 9 .
Sizes. Weight.
Parts.
m. ft. gr. lbs.
1 Frame, including everything of metal, permanent and undetachable,
such as bed-plate, cross-rods for the support of propellers, bearing 2867
points for clutch, etc.
2 Engine, gears, shafts, etc.
3 Pump, 123; pump shaft, 49 172
4 Hull covering, including apron and piece behind separator 274
5 Gasoline and air tanks, 167, 114; air valve, 16 297
6 Smokestack, 319; counter, 95; burner, 165 679
7 Float, 275; pipe from pump to boiler, 40 315
8 Reel, with fork and float 128
9 Wing clamps, 188; guy-post clamps, 24 212
10 Boiler, 764; steam gauge and connections, 79 843
11 Front lower bearing post, 75; clutch post, 58; rear bearing points,
288
155
12 Separator and pipes leading to engines and pump 502
13 Drop piece for rudder, 57; guy-post for rudder, 18 75
14
15
16
17 Wings (without clamp) 2077
18 Superposed wings, 3448
19 Rudder 323
20 Guy sticks, each 53 106
21 Propellers 620
22 Extra length of midrod 377
23 Wood bowsprit 128
24 Canvas keel, 36; rudder, 76 112
25
26
27 Fuel (at starting flight) 175
28 Water (at starting flight) 1525
29
30
31 Sundries unknown
32
DATA S HE E T No. 3.
We i g h t o f A e r o d r o m e N o . 6 , F l a t Wi n g s a n d P é n a u d R u d d e r. C e r t i f i e d t o
b y C h a s . M . M a n l y, J u n e 7 , 1 8 9 9 .
Sizes. Weight.
Parts.
m. ft. gr. lbs.
1 Frame, including everything of metal, permanent and undetachable,
such as bed-plate, cross-rods for the support of propellers, bearing 2867
points for clutch, etc.
2 Engine, gears, shafts, etc.
3 Pump, 123; pump shaft, 49 172
4 Hull covering, including apron and piece behind separator 274
5 Gasoline and air tanks, 167, 114; air valve, 16 297
6 Smokestack, 319; counter, 95; burner, 165 679
7 Float, 275; pipe from pump to boiler, 40 315
8 Reel, with fork and float 128
9 Wing clamps, 188; guy-post clamps, 24 212
10 Boiler, 764; steam gauge and connections, 79 843
11 Front lower bearing post, 75; clutch post, 58; rear bearing points,
288
155
12 Separator and pipes leading to engines and pump 502
13 Drop piece for rudder, 57; guy-post for rudder, 18 75
14
15
16
17 Wings (without clamp) 2077
18 Superposed wings, 3448
19 Rudder 323
20 Guy sticks, each 53 106
21 Propellers 620
22 Extra length of midrod 377
23 Wood bowsprit 128
24 Canvas keel, 36; rudder, 76 112
25
26
27 Fuel (at starting flight) 175
28 Water (at starting flight) 1525
29
30
31 Sundries unknown
32
Page 531
Sizes. Weight.
Parts.
m. ft. gr. lbs.
33
34 Total flying weight 11,995 26.44
35
36
37
38 Total area of support (not including tail) . . . sq. ft. 54
39 Total area of support in feet, divided by total flying weight in lbs. 2.04
40 Total area of horizontal tail . . . sq. ft. 9.5
41 Total area of rudder (vertical) . . . sq. ft. 7.75
42 Horse-power at brake . . . Horse-power by formula*
43
44 Lift at pendulum (during one minute absolute)
45 Lift at pendulum (during one minute in terms of wt.)
46 Minimum pressure with which wheels turn
47 Position of center of pressure of wings† 40% from front
48
49
50 Curvature of wings, 1 in 18
51 Root angle of wings, 10°
52 Tip angle of wings, 10°
53 Position of wings—front edge of front wing, 1595.7; of rear wing,
1406.5
54 How guyed—with wires from wing to wing on top and to guy-post
on bottom
55
56
57
58 Position of center of rudder, 1279.5
59 Angle of tail, 10°
60 Co-efficient elasticity of tail
61 Position of rudder
62
63 Line of thrust, 1500
64 Center of gravity1 of whole, 1484.4
65 Center of gravity2
66 Center of pressure1 of whole estimate
67 Center of pressure2
68
69
70
Parts.
m. ft. gr. lbs.
33
34 Total flying weight 11,995 26.44
35
36
37
38 Total area of support (not including tail) . . . sq. ft. 54
39 Total area of support in feet, divided by total flying weight in lbs. 2.04
40 Total area of horizontal tail . . . sq. ft. 9.5
41 Total area of rudder (vertical) . . . sq. ft. 7.75
42 Horse-power at brake . . . Horse-power by formula*
43
44 Lift at pendulum (during one minute absolute)
45 Lift at pendulum (during one minute in terms of wt.)
46 Minimum pressure with which wheels turn
47 Position of center of pressure of wings† 40% from front
48
49
50 Curvature of wings, 1 in 18
51 Root angle of wings, 10°
52 Tip angle of wings, 10°
53 Position of wings—front edge of front wing, 1595.7; of rear wing,
1406.5
54 How guyed—with wires from wing to wing on top and to guy-post
on bottom
55
56
57
58 Position of center of rudder, 1279.5
59 Angle of tail, 10°
60 Co-efficient elasticity of tail
61 Position of rudder
62
63 Line of thrust, 1500
64 Center of gravity1 of whole, 1484.4
65 Center of gravity2
66 Center of pressure1 of whole estimate
67 Center of pressure2
68
69
70
Page 532
Sizes. Weight.
Parts.
m. ft. gr. lbs.
71
72
Parts.
m. ft. gr. lbs.
71
72
Page 533
Parts. Remarks.
1 Front edge of bowsprit, 1702.7. Weight 2867 gm. for part 1 includes also part 2.
2 Center of float with small wind vane rudder, 1628.9.
6 Front edge of midrod, 1613.7.
9 Center of float with small rudder off, 1609.2.
12 Front edge of F. W., 1595.7.
15 C. of P. on F. W., 1563.7.
18 Back edge of F. W., 1515.7.
21 Line through center of propellers, 1500.
25 C. of G., 1484.4.
28 Front edge of R. W., 1406.5.
31 C. of P. on R. W., 1374.5.
34 End of midrod, 1351.8.
37 Front end of rudder, 1335.
39 Back edge of R. W., 1326.5.
42 Center of rudder, 1279.5.
45 Back end of rudder, 1221.
Footnotes.
* H. P. = (Rev. × diam. × pitch ratio × thrust)/33000
† This is calculated on the assumption that the center of pressure on each wing or on pair of
wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from
front to rear, that for wings of usual size the rear wings have 2-3 of the efficiency per surface
of the front ones and that the tail proper bears no part of the weight; but if rear wing is
smaller or larger this efficiency is smaller or larger per unit of surface.
1 Front edge of bowsprit, 1702.7. Weight 2867 gm. for part 1 includes also part 2.
2 Center of float with small wind vane rudder, 1628.9.
6 Front edge of midrod, 1613.7.
9 Center of float with small rudder off, 1609.2.
12 Front edge of F. W., 1595.7.
15 C. of P. on F. W., 1563.7.
18 Back edge of F. W., 1515.7.
21 Line through center of propellers, 1500.
25 C. of G., 1484.4.
28 Front edge of R. W., 1406.5.
31 C. of P. on R. W., 1374.5.
34 End of midrod, 1351.8.
37 Front end of rudder, 1335.
39 Back edge of R. W., 1326.5.
42 Center of rudder, 1279.5.
45 Back end of rudder, 1221.
Footnotes.
* H. P. = (Rev. × diam. × pitch ratio × thrust)/33000
† This is calculated on the assumption that the center of pressure on each wing or on pair of
wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from
front to rear, that for wings of usual size the rear wings have 2-3 of the efficiency per surface
of the front ones and that the tail proper bears no part of the weight; but if rear wing is
smaller or larger this efficiency is smaller or larger per unit of surface.
Page 534
[p300]
DATA S HE E T No. 4.
We i g h t o f A e r o d r o m e N o . 6 , S u p e r p o s e d Wi n g s a n d P é n a u d R u d d e r.
C e r t i f i e d t o b y C h a s . M . M a n l y, J u n e 1 3 , 1 8 9 9 .
Sizes. Weight.
Parts.
m. ft. gr. lbs.
1 Frame, including everything of metal, permanent and undetachable,
such as bed-plate, cross-rods for the support of propellers, bearing
2867
points for clutch, etc.
2 Engine, gears, shafts, etc.
3 Pump, 123; pump shaft, 49 172
4 Hull covering, including apron and piece behind separator 274
5 Gasoline and air tanks, 167, 114; air valve, 16 297
6 Smokestack, 319; counter, 95; burner, 170 584
7 Float 315
8 Reel, with fork and float 128
9 Wing clamps, 188; guy-post clamps, 24 212
10 Boiler, 764; steam gauge and connections, 79 843
11 Front bearing point, 75; clutch post, 58; rear bearing points, 155 288
12 Separator and pipes to engines and pump 502
13 Drop piece and guy-post for rudder 75
14
15
16
17 Wings (without clamp), 2077; superposed wings 3448
18 Tail (without clamp)
19 Rudder 323
20 Guy sticks 106
21 Propellers 620
22 Extra length of midrod 377
23 Wood bowsprit 128
24 Canvas keel, 36 36
25
26
27 Fuel (at starting flight) 175
28 Water (at starting flight) 1525
29
30
31 Sundries unknown
32
33
DATA S HE E T No. 4.
We i g h t o f A e r o d r o m e N o . 6 , S u p e r p o s e d Wi n g s a n d P é n a u d R u d d e r.
C e r t i f i e d t o b y C h a s . M . M a n l y, J u n e 1 3 , 1 8 9 9 .
Sizes. Weight.
Parts.
m. ft. gr. lbs.
1 Frame, including everything of metal, permanent and undetachable,
such as bed-plate, cross-rods for the support of propellers, bearing
2867
points for clutch, etc.
2 Engine, gears, shafts, etc.
3 Pump, 123; pump shaft, 49 172
4 Hull covering, including apron and piece behind separator 274
5 Gasoline and air tanks, 167, 114; air valve, 16 297
6 Smokestack, 319; counter, 95; burner, 170 584
7 Float 315
8 Reel, with fork and float 128
9 Wing clamps, 188; guy-post clamps, 24 212
10 Boiler, 764; steam gauge and connections, 79 843
11 Front bearing point, 75; clutch post, 58; rear bearing points, 155 288
12 Separator and pipes to engines and pump 502
13 Drop piece and guy-post for rudder 75
14
15
16
17 Wings (without clamp), 2077; superposed wings 3448
18 Tail (without clamp)
19 Rudder 323
20 Guy sticks 106
21 Propellers 620
22 Extra length of midrod 377
23 Wood bowsprit 128
24 Canvas keel, 36 36
25
26
27 Fuel (at starting flight) 175
28 Water (at starting flight) 1525
29
30
31 Sundries unknown
32
33
Page 535
Sizes. Weight.
Parts.
m. ft. gr. lbs.
34 Total flying weight 13,275
35
36
37
38 Total area of support (not including tail) . . . . . . sq. ft. 87.4
39 Total area of support in feet, divided by total flying weight in lbs.
40 Total area of horizontal tail . . . . . . sq. ft. 9.5
41 Total area of rudder (vertical) . . . . . . sq. ft. 7.75
42 Horse-power at brake . . . Horse-power by formula*
43
44 Lift at pendulum (during one minute absolute)
45 Lift at pendulum (during one minute in terms of wt.)
46 Minimum pressure with which wheels turn
47 Position of center of pressure of wings†, 40% from front
48
49
50 Curvature of wings, 1 in 18
51 Root angle of wings, 10°
52 Tip angle of wings, 10°
53 Position of wings—front edge of front wing, 159
54 How guyed
55
56
57
58 Position of tail
1
59 Angle of tail, 7 °
2
60 Co-efficient elasticity of tail, 1240 grammes at center to deflect to the
horizontal
61 Position of rudder
62
63 Line of thrust, 1500
64 Center of gravity1 of whole, 1484.4
65 Center of gravity2
66 Center of pressure1 of whole estimate
67 Center of pressure2
68
69
70
71
Parts.
m. ft. gr. lbs.
34 Total flying weight 13,275
35
36
37
38 Total area of support (not including tail) . . . . . . sq. ft. 87.4
39 Total area of support in feet, divided by total flying weight in lbs.
40 Total area of horizontal tail . . . . . . sq. ft. 9.5
41 Total area of rudder (vertical) . . . . . . sq. ft. 7.75
42 Horse-power at brake . . . Horse-power by formula*
43
44 Lift at pendulum (during one minute absolute)
45 Lift at pendulum (during one minute in terms of wt.)
46 Minimum pressure with which wheels turn
47 Position of center of pressure of wings†, 40% from front
48
49
50 Curvature of wings, 1 in 18
51 Root angle of wings, 10°
52 Tip angle of wings, 10°
53 Position of wings—front edge of front wing, 159
54 How guyed
55
56
57
58 Position of tail
1
59 Angle of tail, 7 °
2
60 Co-efficient elasticity of tail, 1240 grammes at center to deflect to the
horizontal
61 Position of rudder
62
63 Line of thrust, 1500
64 Center of gravity1 of whole, 1484.4
65 Center of gravity2
66 Center of pressure1 of whole estimate
67 Center of pressure2
68
69
70
71
Page 536
Sizes. Weight.
Parts.
m. ft. gr. lbs.
72
Parts.
m. ft. gr. lbs.
72
Page 537
Parts. Remarks.
1 Front edge of bowsprit, 1702.7. Weight 2867 gm. includes parts 2.
2 Center of float without small wind vane rudder, 1666.1. (Center of float with wind vane
rudder on, 1627.)
8 Front edge of midrod, 1613.7.
11 Front edge of F. W., 1585.
13 C. of P. on F. W., 1563.7.
16 Rear edge of F. W., 1531.7.
19 Line through center of propellers, 1500.
23 C. of G., 1484.4.
26 Front edge of R. W., 1395.8.
29 C. of P. on R. W., 1374.5.
32 End of midrod, 1351.8.
35 Front end of rudder, 1335.
38 Back edge of R. W., 1342.5.
40 Center of rudder, 1279.5.
43 Back end of rudder, 1221.
Footnotes.
* H. P. = (Rev. × diam. × pitch ratio × thrust)/33000
† This is calculated on the assumption that the center of pressure on each wing or on pair of
wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from
front to rear, that for wings of usual size the rear wings have 2-3 of the efficiency per surface
of the front ones and that the tail proper bears no part of the weight; but if rear wing is
smaller or larger this efficiency is smaller or larger per unit of surface.
1 Front edge of bowsprit, 1702.7. Weight 2867 gm. includes parts 2.
2 Center of float without small wind vane rudder, 1666.1. (Center of float with wind vane
rudder on, 1627.)
8 Front edge of midrod, 1613.7.
11 Front edge of F. W., 1585.
13 C. of P. on F. W., 1563.7.
16 Rear edge of F. W., 1531.7.
19 Line through center of propellers, 1500.
23 C. of G., 1484.4.
26 Front edge of R. W., 1395.8.
29 C. of P. on R. W., 1374.5.
32 End of midrod, 1351.8.
35 Front end of rudder, 1335.
38 Back edge of R. W., 1342.5.
40 Center of rudder, 1279.5.
43 Back end of rudder, 1221.
Footnotes.
* H. P. = (Rev. × diam. × pitch ratio × thrust)/33000
† This is calculated on the assumption that the center of pressure on each wing or on pair of
wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from
front to rear, that for wings of usual size the rear wings have 2-3 of the efficiency per surface
of the front ones and that the tail proper bears no part of the weight; but if rear wing is
smaller or larger this efficiency is smaller or larger per unit of surface.
Page 538
[p301]
DATA S HE E T No. 5.
We i g h t o f A e r o d r o m e N o . 6 , F l a t Wi n g s a n d P é n a u d R u d d e r. C e r t i f i e d t o
b y C h a s . M . M a n l y, J u n e 2 2 , 1 8 9 9 .
Sizes. Weight.
Parts.
m. ft. gr. lbs.
1 Frame, including everything of metal, permanent and undetachable,
such as bed-plate, cross-rods for the support of propellers, bearing
2867
points for clutch, etc. (bowsprit, 78g)
2 Engine, gears, shafts, etc.
3 Pump, 123; pump shaft, 49 172
4 Hull covering, including apron and piece behind separator 274
5 Gasoline and air tanks, 167, 174; air valve, 16 357
6 Smokestack, 319; counter, 95; burner, 170 584
7 Float 315
8 Reel, with fork and float 128
9 Wing clamps, 188; guy-post clamps, 24 212
10 Boiler, 764; steam gauge and connections, 79 843
11 Front bearing post, 75; clutch-post, 58 133
12 Rear bearing points 155
13 Separator and pipes to engines and pump 502
14 Drop piece and guy-posts, 18; for rudder, 57 75
15
16
17 Wings (without clamp) 2077
18 Tail (without clamp)
19 Rudder 323
20 Guy sticks 106
21 Propellers 620
22 Extra length of midrod 377
23 Wood bowsprit 128
24 Other things
25
26
27 Fuel (at starting flight) 175
28 Water (at starting flight) 1525
29
30
31 Sundries unknown
32
33
DATA S HE E T No. 5.
We i g h t o f A e r o d r o m e N o . 6 , F l a t Wi n g s a n d P é n a u d R u d d e r. C e r t i f i e d t o
b y C h a s . M . M a n l y, J u n e 2 2 , 1 8 9 9 .
Sizes. Weight.
Parts.
m. ft. gr. lbs.
1 Frame, including everything of metal, permanent and undetachable,
such as bed-plate, cross-rods for the support of propellers, bearing
2867
points for clutch, etc. (bowsprit, 78g)
2 Engine, gears, shafts, etc.
3 Pump, 123; pump shaft, 49 172
4 Hull covering, including apron and piece behind separator 274
5 Gasoline and air tanks, 167, 174; air valve, 16 357
6 Smokestack, 319; counter, 95; burner, 170 584
7 Float 315
8 Reel, with fork and float 128
9 Wing clamps, 188; guy-post clamps, 24 212
10 Boiler, 764; steam gauge and connections, 79 843
11 Front bearing post, 75; clutch-post, 58 133
12 Rear bearing points 155
13 Separator and pipes to engines and pump 502
14 Drop piece and guy-posts, 18; for rudder, 57 75
15
16
17 Wings (without clamp) 2077
18 Tail (without clamp)
19 Rudder 323
20 Guy sticks 106
21 Propellers 620
22 Extra length of midrod 377
23 Wood bowsprit 128
24 Other things
25
26
27 Fuel (at starting flight) 175
28 Water (at starting flight) 1525
29
30
31 Sundries unknown
32
33
Page 539
Sizes. Weight.
Parts.
m. ft. gr. lbs.
34 Total flying weight 11,948 26.3
35
36
37
38 Total area of support (not including tail) . . . sq. ft. 54
39 Total area of support in feet, divided by total flying weight in lbs.
40 Total area of horizontal tail . . . sq. ft. 9.5
41 Total area of rudder (vertical) . . . sq. ft. 7.75
42 Horse-power at brake . . . Horse-power by formula*
43
44 Lift at pendulum (during one minute absolute)
45 Lift at pendulum (during one minute in terms of wt.)
46 Minimum pressure with which wheels turn
47 Position of center of pressure of wings† 40% from front
48
49
50 Curvature of wings, 1 in 18
51 Root angle of wings, 10°
52 Tip angle of wings, 10°
53 Position of wings
54 How guyed
55
56
57
58 Position of tail
59 Angle of tail, 7° 30′
60 Co-efficient elasticity of tail, 1240 grammes at center to deflect to
the horizontal
61 Position of rudder
62
63 Line of thrust, 1500
64 Center of gravity1 of whole
65 Center of gravity2
66 Center of pressure1 of whole estimate
67 Center of pressure2
68
69
70
71
72
Parts.
m. ft. gr. lbs.
34 Total flying weight 11,948 26.3
35
36
37
38 Total area of support (not including tail) . . . sq. ft. 54
39 Total area of support in feet, divided by total flying weight in lbs.
40 Total area of horizontal tail . . . sq. ft. 9.5
41 Total area of rudder (vertical) . . . sq. ft. 7.75
42 Horse-power at brake . . . Horse-power by formula*
43
44 Lift at pendulum (during one minute absolute)
45 Lift at pendulum (during one minute in terms of wt.)
46 Minimum pressure with which wheels turn
47 Position of center of pressure of wings† 40% from front
48
49
50 Curvature of wings, 1 in 18
51 Root angle of wings, 10°
52 Tip angle of wings, 10°
53 Position of wings
54 How guyed
55
56
57
58 Position of tail
59 Angle of tail, 7° 30′
60 Co-efficient elasticity of tail, 1240 grammes at center to deflect to
the horizontal
61 Position of rudder
62
63 Line of thrust, 1500
64 Center of gravity1 of whole
65 Center of gravity2
66 Center of pressure1 of whole estimate
67 Center of pressure2
68
69
70
71
72
Page 540
Parts. Remarks.
1 Front edge of bowsprit, 1685.7. Weight 2867 gm. includes Parts 2.
2 Back edge of cylindrical part of float, 1606.5
5 Front edge of midrod, 1613.7.
8 Front edge of F. W., 1595.7.
11 C. of P. on F. W., 1563.7.
14 Back edge of F. W., 1515.7.
17 Line through center of propellers, 1500.
21 C. of G., 1484.4.
24 Front edge R. W., 1406.5.
27 C. of P. on R. W., 1374.5.
30 End of midrod, 1351.8.
33 Front end of rudder, 1335.
36 Back edge R. W., 1326.5.
38 Center of rudder, 1279.5.
41 Back end of rudder, 1221.
Footnotes.
* H. P. = (Rev. × diam. × pitch ratio × thrust)/33000
† This is calculated on the assumption that the center of pressure on each wing or on pair of
wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from
front to rear, that for wings of usual size the rear wings have 2-3 of the efficiency per surface
of the front ones and that the tail proper bears no part of the weight; but if rear wing is
smaller or larger this efficiency is smaller or larger per unit of surface.
1 Front edge of bowsprit, 1685.7. Weight 2867 gm. includes Parts 2.
2 Back edge of cylindrical part of float, 1606.5
5 Front edge of midrod, 1613.7.
8 Front edge of F. W., 1595.7.
11 C. of P. on F. W., 1563.7.
14 Back edge of F. W., 1515.7.
17 Line through center of propellers, 1500.
21 C. of G., 1484.4.
24 Front edge R. W., 1406.5.
27 C. of P. on R. W., 1374.5.
30 End of midrod, 1351.8.
33 Front end of rudder, 1335.
36 Back edge R. W., 1326.5.
38 Center of rudder, 1279.5.
41 Back end of rudder, 1221.
Footnotes.
* H. P. = (Rev. × diam. × pitch ratio × thrust)/33000
† This is calculated on the assumption that the center of pressure on each wing or on pair of
wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from
front to rear, that for wings of usual size the rear wings have 2-3 of the efficiency per surface
of the front ones and that the tail proper bears no part of the weight; but if rear wing is
smaller or larger this efficiency is smaller or larger per unit of surface.
Page 541
[p302]
DATA S HE E T No. 6.
We i g h t o f A e r o d r o m e N o . 5 , F l a t Wi n g s a n d P é n a u d R u d d e r. C e r t i f i e d t o
b y C h a s . M . M a n l y, J u n e 2 3 , 1 8 9 9 .
Sizes. Weight.
Parts.
m. ft. gr. lbs.
1 Frame, including everything of metal, permanent and undetachable,
such as bed-plate, cross-rods for the support of propellers, bearing 3050
points for clutch, etc.
2 Engine 464
3 Pump, 334; pump shaft, 55 389
4 Hull covering 398
5 Gasoline tanks, air tanks, valves, etc. 348
6 Smokestack 373
7 Float, 275; drop piece for rudder, 57; guy-post, 18 350
8 Reel, 128; steam gauge, 81 209
9 Wing clamps, 200; guy-post clamps, 32 232
10 Boiler, 764; burner, 170; counter, 95 1029
11 Rear extension to midrod 174
12 Separator and pipes to engine and pump 502
13 Exhaust pipe 84
14 Front lower bearing point, 84; clutch post, 41 125
15 Rear bearing points, 146; extra strengtheners, 32 178
16
17 Wings (without clamp) 2342
18 Tail (without clamp)
19 Rudder 322
20 Guy sticks, each 56 112
21 Propellers 837
22 Extra length of midrod at front 129
23 Wood bowsprit 132
24 Other things
25
26
27 Fuel (375 at starting flight) 200
28 Water (2100 at starting flight) + 616 in boiler 1400
29
30
31 Sundries unknown
32
33
DATA S HE E T No. 6.
We i g h t o f A e r o d r o m e N o . 5 , F l a t Wi n g s a n d P é n a u d R u d d e r. C e r t i f i e d t o
b y C h a s . M . M a n l y, J u n e 2 3 , 1 8 9 9 .
Sizes. Weight.
Parts.
m. ft. gr. lbs.
1 Frame, including everything of metal, permanent and undetachable,
such as bed-plate, cross-rods for the support of propellers, bearing 3050
points for clutch, etc.
2 Engine 464
3 Pump, 334; pump shaft, 55 389
4 Hull covering 398
5 Gasoline tanks, air tanks, valves, etc. 348
6 Smokestack 373
7 Float, 275; drop piece for rudder, 57; guy-post, 18 350
8 Reel, 128; steam gauge, 81 209
9 Wing clamps, 200; guy-post clamps, 32 232
10 Boiler, 764; burner, 170; counter, 95 1029
11 Rear extension to midrod 174
12 Separator and pipes to engine and pump 502
13 Exhaust pipe 84
14 Front lower bearing point, 84; clutch post, 41 125
15 Rear bearing points, 146; extra strengtheners, 32 178
16
17 Wings (without clamp) 2342
18 Tail (without clamp)
19 Rudder 322
20 Guy sticks, each 56 112
21 Propellers 837
22 Extra length of midrod at front 129
23 Wood bowsprit 132
24 Other things
25
26
27 Fuel (375 at starting flight) 200
28 Water (2100 at starting flight) + 616 in boiler 1400
29
30
31 Sundries unknown
32
33
Page 542
Sizes. Weight.
Parts.
m. ft. gr. lbs.
34 Total flying weight 13,370
35
36
37
38 Total area of support (not including tail) . . . sq. ft. 68
39 Total area of support in feet, divided by total flying weight in lbs.
40 Total area of horizontal tail . . . sq. ft. 6.94
41 Total area of rudder (vertical) . . . sq. ft. 7.64
42 Horse-power at brake . . . Horse-power by formula*
43
44 Lift at pendulum (during one minute absolute)
45 Lift at pendulum (during one minute in terms of wt.)
46 Minimum pressure with which wheels turn
47 Position of center of pressure of wings†
48
49
50 Curvature of wings
51 Root angle of wings, 10°
52 Tip angle of wings, 10°
53 Position of wings
54 How guyed
55
56
57
58 Position of tail
59 Angle of tail, 7° 30′
60 Co-efficient elasticity of tail
61 Position of rudder
62
63 Line of thrust, 1500
64 Center of gravity1 of whole
65 Center of gravity2
66 Center of pressure1 of whole estimate
67 Center of pressure2
68
69
70
71
72
Parts.
m. ft. gr. lbs.
34 Total flying weight 13,370
35
36
37
38 Total area of support (not including tail) . . . sq. ft. 68
39 Total area of support in feet, divided by total flying weight in lbs.
40 Total area of horizontal tail . . . sq. ft. 6.94
41 Total area of rudder (vertical) . . . sq. ft. 7.64
42 Horse-power at brake . . . Horse-power by formula*
43
44 Lift at pendulum (during one minute absolute)
45 Lift at pendulum (during one minute in terms of wt.)
46 Minimum pressure with which wheels turn
47 Position of center of pressure of wings†
48
49
50 Curvature of wings
51 Root angle of wings, 10°
52 Tip angle of wings, 10°
53 Position of wings
54 How guyed
55
56
57
58 Position of tail
59 Angle of tail, 7° 30′
60 Co-efficient elasticity of tail
61 Position of rudder
62
63 Line of thrust, 1500
64 Center of gravity1 of whole
65 Center of gravity2
66 Center of pressure1 of whole estimate
67 Center of pressure2
68
69
70
71
72
Page 543
Parts. Remarks.
1 Front end of midrod, 1611.5.
2 Front edge of F. W., 1609.7.
5 C. of P. on F. W., 1577.7.
8 Back edge of F. W., 1529.7.
11 Line through center of propellers, 1500.
15 C. of G., 1494.6.
18 Front edge of R. W., 1411.7.
21 C. of P. on R. W., 1379.7.
24 Rear end of midrod, 1360.3.
27 Rear end of R. W., 1331.7.
Footnotes.
* H.P = (Rev. × diam. × pitch ratio × thrust)/33000
† This is calculated on the assumption that the center of pressure on each wing or on pair of
wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from
front to rear, that for wings of usual size the rear wings have 2-3 of the efficiency per surface
of the front ones and that the tail proper bears no part of the weight; but if rear wing is
smaller or larger this efficiency is smaller or larger per unit of surface.
1 Front end of midrod, 1611.5.
2 Front edge of F. W., 1609.7.
5 C. of P. on F. W., 1577.7.
8 Back edge of F. W., 1529.7.
11 Line through center of propellers, 1500.
15 C. of G., 1494.6.
18 Front edge of R. W., 1411.7.
21 C. of P. on R. W., 1379.7.
24 Rear end of midrod, 1360.3.
27 Rear end of R. W., 1331.7.
Footnotes.
* H.P = (Rev. × diam. × pitch ratio × thrust)/33000
† This is calculated on the assumption that the center of pressure on each wing or on pair of
wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from
front to rear, that for wings of usual size the rear wings have 2-3 of the efficiency per surface
of the front ones and that the tail proper bears no part of the weight; but if rear wing is
smaller or larger this efficiency is smaller or larger per unit of surface.
Page 544
[p303]
DATA S HE E T No. 7.
We i g h t o f A e r o d r o m e N o . 5 , F l a t Wi n g s a n d P é n a u d R u d d e r. C e r t i f i e d t o
b y C h a s . M . M a n l y, J u l y 1 2 , 1 8 9 9 .
Sizes. Weight.
Parts.
m. ft. gr. lbs.
1 Frame, including everything of metal, permanent and undetachable,
such as bed-plate, cross-rods for the support of propellers, bearing 3050
points for gears, clutch, shafts, etc.
2 Engine 464
3 Pump, 334; pump shaft, with gear and eccentric and end rod, 55 389
4 Hull Covering, 264; apron 115; piece behind separator, 19 398
5 Gasoline and air tanks, 167, 165; air valve, 16 348
6 Smokestack, 310; piece to protect midrod, 63 373
7 Float, 275; drop piece for rudder, 57; guy-post, 18 350
8 Reel, fork and float, 128; steam gauge with pipe, 81 209
9 Wing clamps, 200; guy-post clamps, 32 232
10 Boiler, 764; burner, 170; counter, 95 1029
11 Rear extension to midrod 174
12 Separator and pipes to engine and pump 502
13 Exhaust pipe, 84 84
14 Front lower bearing point, 84; clutch post, 41 125
15 Rear bearing points, 146; extra strengtheners, 32 178
16
17 Wings (without clamp) (2180 in 1896) 2342
18 Tail (without clamp); part of rudder
19 Rudder reduced (No. 2 or new one, 299) 322
20 Guy sticks, each 56 112
21 Propellers (95 cms.; wood, 837; 95 cms. canvas, 548) 837
22 Extra length of midrod (front), 129 129
23 Wood bowsprit (complete), 132 132
24 Other things
25
26
27 Fuel (375 at starting flight) 200
28 Water (2100 at starting flight) + 616 in boiler 1400
29
30
31 Sundries unknown
32
33
DATA S HE E T No. 7.
We i g h t o f A e r o d r o m e N o . 5 , F l a t Wi n g s a n d P é n a u d R u d d e r. C e r t i f i e d t o
b y C h a s . M . M a n l y, J u l y 1 2 , 1 8 9 9 .
Sizes. Weight.
Parts.
m. ft. gr. lbs.
1 Frame, including everything of metal, permanent and undetachable,
such as bed-plate, cross-rods for the support of propellers, bearing 3050
points for gears, clutch, shafts, etc.
2 Engine 464
3 Pump, 334; pump shaft, with gear and eccentric and end rod, 55 389
4 Hull Covering, 264; apron 115; piece behind separator, 19 398
5 Gasoline and air tanks, 167, 165; air valve, 16 348
6 Smokestack, 310; piece to protect midrod, 63 373
7 Float, 275; drop piece for rudder, 57; guy-post, 18 350
8 Reel, fork and float, 128; steam gauge with pipe, 81 209
9 Wing clamps, 200; guy-post clamps, 32 232
10 Boiler, 764; burner, 170; counter, 95 1029
11 Rear extension to midrod 174
12 Separator and pipes to engine and pump 502
13 Exhaust pipe, 84 84
14 Front lower bearing point, 84; clutch post, 41 125
15 Rear bearing points, 146; extra strengtheners, 32 178
16
17 Wings (without clamp) (2180 in 1896) 2342
18 Tail (without clamp); part of rudder
19 Rudder reduced (No. 2 or new one, 299) 322
20 Guy sticks, each 56 112
21 Propellers (95 cms.; wood, 837; 95 cms. canvas, 548) 837
22 Extra length of midrod (front), 129 129
23 Wood bowsprit (complete), 132 132
24 Other things
25
26
27 Fuel (375 at starting flight) 200
28 Water (2100 at starting flight) + 616 in boiler 1400
29
30
31 Sundries unknown
32
33
Page 545
Sizes. Weight.
Parts.
m. ft. gr. lbs.
34 Total flying weight 13,379
35
36
37
38 Total area of support (not including tail) . . . sq. ft. 68
39 Total area of support in feet, divided by total flying weight in lbs.
40 Total area of horizontal tail . . . sq. ft. 6.94
41 Total area of rudder (vertical) . . . sq. ft. 7.64
42 Horse-power at brake . . . Horse-power by formula*
43
44 Lift at pendulum (during one minute absolute)
45 Lift at pendulum (during one minute in terms of wt.)
46 Minimum pressure with which wheels turn
47 Position of center of pressure of wings†
48
49
50 Curvature of wings, 1 in 12
51 Root angle of wings, 10°
52 Tip angle of wings, 10°
53 Position of wings
54 How guyed
55
56
57
58 Position of tail
59 Angle of tail, 7° 30′
60 Co-efficient elasticity of tail, 1240 grammes at center of rudder to
bring it to a horizontal; 490 grammes at point same distance from front
end of rudder as length of rudder of 1896, to bring to horizontal
61 Position of rudder
62
63 Line of thrust, 1500
64 Center of gravity1 of whole
65 Center of gravity2
66 Center of pressure1 of whole estimate
67 Center of pressure2
68
69
70
71
Parts.
m. ft. gr. lbs.
34 Total flying weight 13,379
35
36
37
38 Total area of support (not including tail) . . . sq. ft. 68
39 Total area of support in feet, divided by total flying weight in lbs.
40 Total area of horizontal tail . . . sq. ft. 6.94
41 Total area of rudder (vertical) . . . sq. ft. 7.64
42 Horse-power at brake . . . Horse-power by formula*
43
44 Lift at pendulum (during one minute absolute)
45 Lift at pendulum (during one minute in terms of wt.)
46 Minimum pressure with which wheels turn
47 Position of center of pressure of wings†
48
49
50 Curvature of wings, 1 in 12
51 Root angle of wings, 10°
52 Tip angle of wings, 10°
53 Position of wings
54 How guyed
55
56
57
58 Position of tail
59 Angle of tail, 7° 30′
60 Co-efficient elasticity of tail, 1240 grammes at center of rudder to
bring it to a horizontal; 490 grammes at point same distance from front
end of rudder as length of rudder of 1896, to bring to horizontal
61 Position of rudder
62
63 Line of thrust, 1500
64 Center of gravity1 of whole
65 Center of gravity2
66 Center of pressure1 of whole estimate
67 Center of pressure2
68
69
70
71
Page 546
Sizes. Weight.
Parts.
m. ft. gr. lbs.
72
Parts.
m. ft. gr. lbs.
72
Page 547
Parts. Remarks.
1 Front end of bowsprit, 1700.5. Front end of midrod 1611.5.
3 Front edge of F. W., 1609.7.
6 C. of P. on F. W., 1577.7.
9 Rear edge of F. W., 1529.7.
12 Line through center of propellers 1500.
16 Front edge of R. W., 1411.7.
19 C. of P. on R. W., 1379.7.
22 End of midrod, 1360.3.
25 Front end of rudder, 1343.5.
28 Back edge of R. W., 1331.7.
31 Center of rudder, 1288.
34 Back end of rudder, 1229.5.
Footnotes.
* H.P. = (Rev. × diam. × pitch ratio × thrust) /33000
† This is calculated on the assumption that the center of pressure on each wing or on a pair of
wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from the
front to the rear, that for wings of usual size the rear wing have 2-3 of the efficiency per
surface of the front ones and that the tail proper bears no part of the weight; but if rear wing
is smaller or larger this efficiency is smaller or larger per unit of surface.
1 Front end of bowsprit, 1700.5. Front end of midrod 1611.5.
3 Front edge of F. W., 1609.7.
6 C. of P. on F. W., 1577.7.
9 Rear edge of F. W., 1529.7.
12 Line through center of propellers 1500.
16 Front edge of R. W., 1411.7.
19 C. of P. on R. W., 1379.7.
22 End of midrod, 1360.3.
25 Front end of rudder, 1343.5.
28 Back edge of R. W., 1331.7.
31 Center of rudder, 1288.
34 Back end of rudder, 1229.5.
Footnotes.
* H.P. = (Rev. × diam. × pitch ratio × thrust) /33000
† This is calculated on the assumption that the center of pressure on each wing or on a pair of
wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from the
front to the rear, that for wings of usual size the rear wing have 2-3 of the efficiency per
surface of the front ones and that the tail proper bears no part of the weight; but if rear wing
is smaller or larger this efficiency is smaller or larger per unit of surface.
Page 548
[p304]
DATA S HE E T No. 8.
We i g h t o f A e r o d r o m e N o . 5 , F l a t Wi n g s a n d P é n a u d R u d d e r. C e r t i f i e d t o
b y C h a s . M . M a n l y, J u l y 1 9 , 1 8 9 9 .
Sizes. Weight.
Parts.
m. ft. gr. lbs.
1 Frame, including everything of metal, permanent and undetachable, such as
bed-plate, cross-rods for the support of propellers, bearing points for clutch, 3556
etc.
2 Engine, gears, shafts, etc. 476
3 Pump, pump shaft 389
4 Hull covering, 264; apron, 115; piece behind separator, 19 398
5 Gasoline and air tanks, 167, 165; air valve, 16 348
6 Smokestack, 310; piece to protect midrod, 63 373
7 Float, 275; drop piece for rudder, 57; guy-post, 18 350
8 Reel, fork and float, 128; steam gauge with pipe, 81 209
9 Wing clamps, 200; guy-post clamps, 32 232
10 Boiler, 800; burner, 170; counter, 95 1065
11 Rear extension to midrod 174
12 Separator and pipes to engine and pump 502
13 Exhaust pipe 84
14 Front lower bearing point, 84; clutch post, 41 125
15 Rear bearing points, 146; extra strengtheners, 32 178
16
17 Wings (without clamp) 2446
18 Tail (without clamp), part of rudder
19 Rudder 299
20 Guy sticks, each 56 112
21 Propellers, 95 cm. wood 837
22 Extra length of midrod 168
23 Wood bowsprit 78
24 Other things
25
26
27 Fuel (375 at starting flight) 200
28 Water (2100 at starting flight) + 616 in boiler 1400
29
30
31 Sundries unknown
32
33
DATA S HE E T No. 8.
We i g h t o f A e r o d r o m e N o . 5 , F l a t Wi n g s a n d P é n a u d R u d d e r. C e r t i f i e d t o
b y C h a s . M . M a n l y, J u l y 1 9 , 1 8 9 9 .
Sizes. Weight.
Parts.
m. ft. gr. lbs.
1 Frame, including everything of metal, permanent and undetachable, such as
bed-plate, cross-rods for the support of propellers, bearing points for clutch, 3556
etc.
2 Engine, gears, shafts, etc. 476
3 Pump, pump shaft 389
4 Hull covering, 264; apron, 115; piece behind separator, 19 398
5 Gasoline and air tanks, 167, 165; air valve, 16 348
6 Smokestack, 310; piece to protect midrod, 63 373
7 Float, 275; drop piece for rudder, 57; guy-post, 18 350
8 Reel, fork and float, 128; steam gauge with pipe, 81 209
9 Wing clamps, 200; guy-post clamps, 32 232
10 Boiler, 800; burner, 170; counter, 95 1065
11 Rear extension to midrod 174
12 Separator and pipes to engine and pump 502
13 Exhaust pipe 84
14 Front lower bearing point, 84; clutch post, 41 125
15 Rear bearing points, 146; extra strengtheners, 32 178
16
17 Wings (without clamp) 2446
18 Tail (without clamp), part of rudder
19 Rudder 299
20 Guy sticks, each 56 112
21 Propellers, 95 cm. wood 837
22 Extra length of midrod 168
23 Wood bowsprit 78
24 Other things
25
26
27 Fuel (375 at starting flight) 200
28 Water (2100 at starting flight) + 616 in boiler 1400
29
30
31 Sundries unknown
32
33
Page 549
Sizes. Weight.
Parts.
m. ft. gr. lbs.
34 Total flying weight
35
36
37
38 Total area of support (not including tail) . . . sq. ft. 68
39 Total area of support in feet, divided by total flying weight in lbs.
40 Total area of horizontal tail . . . sq. ft.
41 Total area of rudder (vertical) . . . sq. ft.
42 Horse-power at brake . . . Horse-power by formula*
43
44 Lift at pendulum (during one minute absolute)
45 Lift at pendulum (during one minute in terms of wt.)
46 Minimum pressure with which wheels turn
47 Position of center of pressure of wings†
48
49
50 Curvature of wings
51 Root angle of wings, 10°
52 Tip angle of wings, 10°
53 Position of wings
54 How guyed
55
56
57
58 Position of tail
59 Angle of tail, 5°
60 Co-efficient elasticity of tail, 200 grammes at center gives deflection to
horizontal
61 Position of rudder
62 Elasticity caused by two 1/2-inch rubber bands above and two 1/4-inch
bands, in tandem, below
63 Line of thrust, 1500
64 Center of gravity1 of whole
65 Center of gravity2
66 Center of pressure1 of whole estimate
67 Center of pressure2
68
69
70
71
Parts.
m. ft. gr. lbs.
34 Total flying weight
35
36
37
38 Total area of support (not including tail) . . . sq. ft. 68
39 Total area of support in feet, divided by total flying weight in lbs.
40 Total area of horizontal tail . . . sq. ft.
41 Total area of rudder (vertical) . . . sq. ft.
42 Horse-power at brake . . . Horse-power by formula*
43
44 Lift at pendulum (during one minute absolute)
45 Lift at pendulum (during one minute in terms of wt.)
46 Minimum pressure with which wheels turn
47 Position of center of pressure of wings†
48
49
50 Curvature of wings
51 Root angle of wings, 10°
52 Tip angle of wings, 10°
53 Position of wings
54 How guyed
55
56
57
58 Position of tail
59 Angle of tail, 5°
60 Co-efficient elasticity of tail, 200 grammes at center gives deflection to
horizontal
61 Position of rudder
62 Elasticity caused by two 1/2-inch rubber bands above and two 1/4-inch
bands, in tandem, below
63 Line of thrust, 1500
64 Center of gravity1 of whole
65 Center of gravity2
66 Center of pressure1 of whole estimate
67 Center of pressure2
68
69
70
71
Page 550
Sizes. Weight.
Parts.
m. ft. gr. lbs.
72
Parts.
m. ft. gr. lbs.
72
Page 551
Parts. Remarks.
1 Front end of bowsprit, 1683.5.
2 C. of float, 1614.5.
5 Front end of midrod, 1611.5.
8 C. of reel and float, 1577.5.
11 Front edge of F. W., 1609.7.
14 C. of P. on F. W., 1577.7.
17 Rear edge of F. W., 1529.7.
20 Line through center of propellers, 1500.
24 C. of G., 1498.
27 Front edge of R. W., 1406.7.
30 C. of P. on R. W., 1374.7.
33 End of midrod, 1360.3.
36 Front end of rudder, 1343.5.
39 Back edge of R. W., 1326.7.
41 Center of rudder, 1288.
44 Back end of rudder, 1229.5.
47 N. B.—Distance between C. P. on F. W., and C. G. = 79.7. Distance between C. P. on R. W.
and C. G. = 123.3. If the mean C. P. is to be over the C. G. we should require an efficiency
for the rear wings of 64.6%.
Footnotes.
* H. P. = (Rev. × diam. × pitch ratio × thrust)/33000
† This is calculated on the assumption that the center of pressure on each wing or on pair of
wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from
front to rear, that for wings of usual size the rear wings have 2-3 of the efficiency per surface
of the front ones and that the tail proper bears no part of the weight; but if rear wing is
smaller or larger this efficiency is smaller or larger per unit of surface.
1 Front end of bowsprit, 1683.5.
2 C. of float, 1614.5.
5 Front end of midrod, 1611.5.
8 C. of reel and float, 1577.5.
11 Front edge of F. W., 1609.7.
14 C. of P. on F. W., 1577.7.
17 Rear edge of F. W., 1529.7.
20 Line through center of propellers, 1500.
24 C. of G., 1498.
27 Front edge of R. W., 1406.7.
30 C. of P. on R. W., 1374.7.
33 End of midrod, 1360.3.
36 Front end of rudder, 1343.5.
39 Back edge of R. W., 1326.7.
41 Center of rudder, 1288.
44 Back end of rudder, 1229.5.
47 N. B.—Distance between C. P. on F. W., and C. G. = 79.7. Distance between C. P. on R. W.
and C. G. = 123.3. If the mean C. P. is to be over the C. G. we should require an efficiency
for the rear wings of 64.6%.
Footnotes.
* H. P. = (Rev. × diam. × pitch ratio × thrust)/33000
† This is calculated on the assumption that the center of pressure on each wing or on pair of
wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from
front to rear, that for wings of usual size the rear wings have 2-3 of the efficiency per surface
of the front ones and that the tail proper bears no part of the weight; but if rear wing is
smaller or larger this efficiency is smaller or larger per unit of surface.
Page 552
[p305]
DATA S HE E T No. 9.
We i g h t o f A e r o d r o m e N o . 6 , F l a t Wi n g s a n d P é n a u d R u d d e r. C e r t i f i e d t o
b y C h a s . M . M a n l y, J u l y 2 7 , 1 8 9 9 .
Sizes. Weight.
Parts.
m. ft. gr. lbs.
1 Frame, including everything of metal, permanent and undetachable,
such as bed-plate, cross-rods for the support of propellers, bearing
2867
points for clutch. etc.
2 Engine, gears, shafts, etc.
3 Pump, 123; pump shaft, 49 172
4 Hull covering, including apron and piece behind separator 274
5 Gasoline and air tanks, 167, 174; air valve, 18 361
6 Smokestack, 319; counter, 95; burner, 170 584
7 Float 290
8 Reel, fork and float 128
9 Wing clamps, 188; guy-post clamps, 24 212
10 Boiler, 764; steam gauge and connections, 79 843
11 Front bearing point, 75; clutch post, 58; rear bearing points, 155 288
12 Separator and pipes leading to engine and pump 502
13 Drop piece and guy-post for rudder 75
14
15
16
17 Wings (without clamp), repaired 2123
18 Tail (without clamp)
19 Rudder 299
20 Guy sticks 106
21 Propellers 628
22 Extra length of midrod 377
23 Wood bowsprit 78
24 Other things (canvas keel, 36; rudder, 76) 112
25
26
27 Fuel (at starting flight) 175
28 Water (at starting flight) 1525
29
30
31 Sundries unknown
32
33
DATA S HE E T No. 9.
We i g h t o f A e r o d r o m e N o . 6 , F l a t Wi n g s a n d P é n a u d R u d d e r. C e r t i f i e d t o
b y C h a s . M . M a n l y, J u l y 2 7 , 1 8 9 9 .
Sizes. Weight.
Parts.
m. ft. gr. lbs.
1 Frame, including everything of metal, permanent and undetachable,
such as bed-plate, cross-rods for the support of propellers, bearing
2867
points for clutch. etc.
2 Engine, gears, shafts, etc.
3 Pump, 123; pump shaft, 49 172
4 Hull covering, including apron and piece behind separator 274
5 Gasoline and air tanks, 167, 174; air valve, 18 361
6 Smokestack, 319; counter, 95; burner, 170 584
7 Float 290
8 Reel, fork and float 128
9 Wing clamps, 188; guy-post clamps, 24 212
10 Boiler, 764; steam gauge and connections, 79 843
11 Front bearing point, 75; clutch post, 58; rear bearing points, 155 288
12 Separator and pipes leading to engine and pump 502
13 Drop piece and guy-post for rudder 75
14
15
16
17 Wings (without clamp), repaired 2123
18 Tail (without clamp)
19 Rudder 299
20 Guy sticks 106
21 Propellers 628
22 Extra length of midrod 377
23 Wood bowsprit 78
24 Other things (canvas keel, 36; rudder, 76) 112
25
26
27 Fuel (at starting flight) 175
28 Water (at starting flight) 1525
29
30
31 Sundries unknown
32
33
Page 553
Sizes. Weight.
Parts.
m. ft. gr. lbs.
34 Total flying weight 12,019
35
36
37
38 Total area of support (not including tail) . . . sq. ft. 54
39 Total area of support in feet, divided by total flying weight in lbs.
40 Total area of horizontal tail . . . sq. ft. 9.5
41 Total area of rudder (vertical) . . . sq. ft. 7.75
42 Horse-power at brake . . . Horse-power by formula*
43
44 Lift at pendulum (during one minute absolute)
45 Lift at pendulum (during one minute in terms of wt.)
46 Minimum pressure with which wheels turn
47 Position of center of pressure of wings†
48
49
50 Curvature of wings, 1 in 18
51 Root angle of wings, 10°
52 Tip angle of wings 10°
53 Position of wings.
54 How guyed.
55
56
57
58 Position of tail
59 Angle of tail, 5°
60 Co-efficient elasticity of tail, 200 grammes at center to deflect it to the
horizontal
61 Position of rudder
62
63 Line of thrust, 1500
64 Center of gravity1 of whole
65 Center of gravity2
66 Center of pressure1 of whole estimate
67 Center of pressure2
68
69
70
71
72
Parts.
m. ft. gr. lbs.
34 Total flying weight 12,019
35
36
37
38 Total area of support (not including tail) . . . sq. ft. 54
39 Total area of support in feet, divided by total flying weight in lbs.
40 Total area of horizontal tail . . . sq. ft. 9.5
41 Total area of rudder (vertical) . . . sq. ft. 7.75
42 Horse-power at brake . . . Horse-power by formula*
43
44 Lift at pendulum (during one minute absolute)
45 Lift at pendulum (during one minute in terms of wt.)
46 Minimum pressure with which wheels turn
47 Position of center of pressure of wings†
48
49
50 Curvature of wings, 1 in 18
51 Root angle of wings, 10°
52 Tip angle of wings 10°
53 Position of wings.
54 How guyed.
55
56
57
58 Position of tail
59 Angle of tail, 5°
60 Co-efficient elasticity of tail, 200 grammes at center to deflect it to the
horizontal
61 Position of rudder
62
63 Line of thrust, 1500
64 Center of gravity1 of whole
65 Center of gravity2
66 Center of pressure1 of whole estimate
67 Center of pressure2
68
69
70
71
72
Page 554
Parts. Remarks.
1 Front end of bowsprit, 1695.7. Weight 2867 includes Parts 2.
2 Front end of midrod, 1623.7.
5 C. of float, 1618.2.
8 Reel and float, 1576.7.
11 Front edge, F. W., 1595.8.
13 C. of P. on F. W., 1563.8.
16 Rear edge F. W., 1515.8.
19 Line through center of propellers, 1500.
23 C. of G., 1485.5.
26 Front edge of R. W., 1406.7.
29 C. of P. on R. W., 1374.7.
32 End of midrod, 1352.2.
35 Front end of rudder, 1333.9.
38 Rear edge of R. W., 1326.7.
40 Center of rudder, 1280.6.
43 Back end of rudder, 1219.9.
Footnotes.
* H. P. = (Rev. × diam. × pitch ratio × thrust)/33000
† This is calculated on the assumption that the center of pressure on each wing or on pair of
wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from
front to rear, that for wings of usual size the rear wings have 2-3 of the efficiency per surface
of the front ones and that the tail proper bears no part of the weight; but if the rear wing is
smaller or larger this efficiency is smaller or larger per unit of surface.
1 Front end of bowsprit, 1695.7. Weight 2867 includes Parts 2.
2 Front end of midrod, 1623.7.
5 C. of float, 1618.2.
8 Reel and float, 1576.7.
11 Front edge, F. W., 1595.8.
13 C. of P. on F. W., 1563.8.
16 Rear edge F. W., 1515.8.
19 Line through center of propellers, 1500.
23 C. of G., 1485.5.
26 Front edge of R. W., 1406.7.
29 C. of P. on R. W., 1374.7.
32 End of midrod, 1352.2.
35 Front end of rudder, 1333.9.
38 Rear edge of R. W., 1326.7.
40 Center of rudder, 1280.6.
43 Back end of rudder, 1219.9.
Footnotes.
* H. P. = (Rev. × diam. × pitch ratio × thrust)/33000
† This is calculated on the assumption that the center of pressure on each wing or on pair of
wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from
front to rear, that for wings of usual size the rear wings have 2-3 of the efficiency per surface
of the front ones and that the tail proper bears no part of the weight; but if the rear wing is
smaller or larger this efficiency is smaller or larger per unit of surface.
Page 555
[p306]
DATA S HE E T No. 10.
We i g h t o f A e r o d r o m e N o . 5 , F l a t Wi n g s a n d P é n a u d R u d d e r. C e r t i f i e d t o
b y C h a s . M . M a n l y, J u l y 2 7 , 1 8 9 9 .
Sizes. Weight.
Parts.
m. ft. gr. lbs.
1 Frame, including everything of metal, permanent and
undetachable, such as bed-plate, cross-rods for the support of
3342
propellers, gears, shafts, etc. (such as guy-wires and turn buckles,
26g).
2 Engine. 476
3 Pump, 301; pump shaft, 55; support to pump, 33. 389
4 Hull covering: front, 47; sides, 92; top 46; small side pieces, 44. 229
5 Gasoline and air tanks, 167, 165; air valve, 18; netting, 30; piece
400
rear of separator, 20.
6 Smokestack, 310; piece to protect midrod, 63. 373
7 Float, 290; drop piece for rudder, 57. 347
8 Reel, fork and float, 128; counter, 95. 223
9 Wing clamps, 202; guy-post clamps, 33. 235
10 Burner, 170; boiler 759. 929
11 Separator with tubes brazed to it. 513
12 Steam pipe, 87; steam gauge and connections, 81. 168
13 Exhaust pipe, 90; wooden plugs in nose of frame, 10 100
14 Upper front bearing point and clutch post. 136
15 Lower front bearing point, 84; lower rear bearing point, 146;
271
clutch, 41.
16
17 Wings (without clamp), front, 2 × 662; rear 2 × 605. 2534
18 Tail (without clamp).
19 Rudder. 299
20 Guy sticks 65; rear, 50. 114
21 Propellers, 100 cm. round ends, 30° blade. 757
22 Extra length of midrod, front, 174; rear, 227. 401
23 Wood bowsprit (heavy one). 130
24 Other things.
25
26
27 Fuel (390 at starting flight). 225
28 Water (2000 at starting flight). 1500
29
30 Lead on bowsprit to balance. 13
DATA S HE E T No. 10.
We i g h t o f A e r o d r o m e N o . 5 , F l a t Wi n g s a n d P é n a u d R u d d e r. C e r t i f i e d t o
b y C h a s . M . M a n l y, J u l y 2 7 , 1 8 9 9 .
Sizes. Weight.
Parts.
m. ft. gr. lbs.
1 Frame, including everything of metal, permanent and
undetachable, such as bed-plate, cross-rods for the support of
3342
propellers, gears, shafts, etc. (such as guy-wires and turn buckles,
26g).
2 Engine. 476
3 Pump, 301; pump shaft, 55; support to pump, 33. 389
4 Hull covering: front, 47; sides, 92; top 46; small side pieces, 44. 229
5 Gasoline and air tanks, 167, 165; air valve, 18; netting, 30; piece
400
rear of separator, 20.
6 Smokestack, 310; piece to protect midrod, 63. 373
7 Float, 290; drop piece for rudder, 57. 347
8 Reel, fork and float, 128; counter, 95. 223
9 Wing clamps, 202; guy-post clamps, 33. 235
10 Burner, 170; boiler 759. 929
11 Separator with tubes brazed to it. 513
12 Steam pipe, 87; steam gauge and connections, 81. 168
13 Exhaust pipe, 90; wooden plugs in nose of frame, 10 100
14 Upper front bearing point and clutch post. 136
15 Lower front bearing point, 84; lower rear bearing point, 146;
271
clutch, 41.
16
17 Wings (without clamp), front, 2 × 662; rear 2 × 605. 2534
18 Tail (without clamp).
19 Rudder. 299
20 Guy sticks 65; rear, 50. 114
21 Propellers, 100 cm. round ends, 30° blade. 757
22 Extra length of midrod, front, 174; rear, 227. 401
23 Wood bowsprit (heavy one). 130
24 Other things.
25
26
27 Fuel (390 at starting flight). 225
28 Water (2000 at starting flight). 1500
29
30 Lead on bowsprit to balance. 13
Page 556
Sizes. Weight.
Parts.
m. ft. gr. lbs.
31 Sundries unknown.
32
33
34 Total flying weight. 14,704 1 03
35
36
37
38 Total area of support (not including tail). . . . sq. ft. 68
39 Total area of support in feet, divided by total flying weight in lbs. 2.1935
40 Total area of horizontal tail. . . . sq. ft. 6.94
41 Total area of rudder (vertical). . . . sq. ft. 7.64
42 Horse-power at brake . . . Horse-power by formula*
43
44 Lift at pendulum (during one minute absolute).
45 Lift at pendulum (during one minute in terms of wt.).
46 Minimum pressure with which wheels turn.
47 Position of center of pressure of wings†.
48
49
50 Curvature of wings, 1 in 12, but about 1 in 11 now.
51 Root angle of wings, 10°.
52 Tip angle of wings 10°.
53 Position of wings.
54 How guyed.
55
56
57
58 Position of tail.
59 Angle of tail, 5° elevation at rear end.
60 Co-efficient elasticity of tail, 200 grammes at center to deflect it
to a horizontal.
61 Position of rudder.
62
63 Line of thrust, 1500.
64 Center of gravity1 of whole, 1498.
65 Center of gravity2.
66 Center of pressure1 of whole estimate.
67 Center of pressure2.
68
69
Parts.
m. ft. gr. lbs.
31 Sundries unknown.
32
33
34 Total flying weight. 14,704 1 03
35
36
37
38 Total area of support (not including tail). . . . sq. ft. 68
39 Total area of support in feet, divided by total flying weight in lbs. 2.1935
40 Total area of horizontal tail. . . . sq. ft. 6.94
41 Total area of rudder (vertical). . . . sq. ft. 7.64
42 Horse-power at brake . . . Horse-power by formula*
43
44 Lift at pendulum (during one minute absolute).
45 Lift at pendulum (during one minute in terms of wt.).
46 Minimum pressure with which wheels turn.
47 Position of center of pressure of wings†.
48
49
50 Curvature of wings, 1 in 12, but about 1 in 11 now.
51 Root angle of wings, 10°.
52 Tip angle of wings 10°.
53 Position of wings.
54 How guyed.
55
56
57
58 Position of tail.
59 Angle of tail, 5° elevation at rear end.
60 Co-efficient elasticity of tail, 200 grammes at center to deflect it
to a horizontal.
61 Position of rudder.
62
63 Line of thrust, 1500.
64 Center of gravity1 of whole, 1498.
65 Center of gravity2.
66 Center of pressure1 of whole estimate.
67 Center of pressure2.
68
69
Page 557
Sizes. Weight.
Parts.
m. ft. gr. lbs.
70
71
72
Parts.
m. ft. gr. lbs.
70
71
72
Page 558
Parts. Remarks.
1 Thirteen grammes of lead on end of bowsprit.
2 End of bowsprit, 1708.
4 C. of float, 1622.
6 Front end of midrod, 1619.
9 Reel and float, 1601.5.
12 Front edge of F. W., 1609.7.
15 C. of P. on F. W., 1577.7.
17 Rear edge of F. W., 1529.7.
20 Line through center of propellers, 1500
24 C. of G., 1498.
27 Front edge of R. W., 1404.7.
30 C. of P. on R. W., 1372.7.
33 End of midrod, 1350.3.
36 Front end of rudder, 1333.5.
39 Back edge of R. W., 1324.7.
41 Centre of rudder, 1279.5.
44 Rear end of rudder, 1222.
47 Distance between C. P. on F. W. and C. G., = 79.7. Distance between C. P. on R. W., and C.
G. = 125.3. If the mean C. P. is to be over the C. G. we should require an efficiency of 63.6
for the rear wings.
Footnotes.
* H. P. = (Rev. × diam. × pitch ratio × thrust)/33000
† This is calculated on the assumption that the center of pressure on each wing or on pair of
wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from
front to rear, that for wings of usual size the rear wings have 2-3 of the efficiency per surface
of the front ones and that the tail proper bears no part of the weight: but if the rear wing is
smaller or larger this efficiency is smaller or larger per unit of surface.
1 Thirteen grammes of lead on end of bowsprit.
2 End of bowsprit, 1708.
4 C. of float, 1622.
6 Front end of midrod, 1619.
9 Reel and float, 1601.5.
12 Front edge of F. W., 1609.7.
15 C. of P. on F. W., 1577.7.
17 Rear edge of F. W., 1529.7.
20 Line through center of propellers, 1500
24 C. of G., 1498.
27 Front edge of R. W., 1404.7.
30 C. of P. on R. W., 1372.7.
33 End of midrod, 1350.3.
36 Front end of rudder, 1333.5.
39 Back edge of R. W., 1324.7.
41 Centre of rudder, 1279.5.
44 Rear end of rudder, 1222.
47 Distance between C. P. on F. W. and C. G., = 79.7. Distance between C. P. on R. W., and C.
G. = 125.3. If the mean C. P. is to be over the C. G. we should require an efficiency of 63.6
for the rear wings.
Footnotes.
* H. P. = (Rev. × diam. × pitch ratio × thrust)/33000
† This is calculated on the assumption that the center of pressure on each wing or on pair of
wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from
front to rear, that for wings of usual size the rear wings have 2-3 of the efficiency per surface
of the front ones and that the tail proper bears no part of the weight: but if the rear wing is
smaller or larger this efficiency is smaller or larger per unit of surface.
Page 559
[p307]
DATA S HE E T No. 11.
We i g h t o f A e r o d r o m e N o . 5 , S u p e r p o s e d Wi n g s a n d P é n a u d R u d d e r.
C e r t i f i e d t o b y C h a s . M . M a n l y, A u g u s t 3 , 1 8 9 9 .
Sizes. Weight.
Parts.
m. ft. gr. lbs.
1 Frame, including everything of metal, permanent and undetachable,
such as bed-plate, cross-rods for the support of propellers, bearing 3556
points for clutch, etc.
2 Engine, complete 476
3 Pump, 301; pump shaft, 55; support to pump, 33 389
4 Hull covering, 276; apron, 117; piece behind separator 393
5 Gasoline and air tanks, 167, 165; air valve, 17 349
6 Smokestack and piece to protect midrod 385
7 Float, 290; drop piece for rudder, 57; guy-post and clamp, 17 364
8 Reel, fork and float, 128; steam gauge with pipe, 81 209
9 Wing claps, 202; guy-post clamps, 33 235
10 Boiler, 775; burner, 171; counter, 100 1046
11 Rear extension to midrod 227
12 Separator and pipes to engine and pump 513
13 Exhaust pipe 90
14 Front lower bearing points, 84; clutch post, 41 125
15 Rear bearing points, 146; extra strengtheners, 32 178
16
17 Wings (without clamp)
18 Tail (without clamp), part of rudder
19 Rudder 309
20 Guy sticks, each 60 120
21 Propellers, 100 cm. round end 757
22 Extra length of midrod, front 174
23 Wood bowsprit 130
24 Other things, 248 grammes of lead on end of bowsprit 248
25
26
27 Fuel (at starting flight)
28 Water (at starting flight)
29
30
31 Sundries unknown
32
33
DATA S HE E T No. 11.
We i g h t o f A e r o d r o m e N o . 5 , S u p e r p o s e d Wi n g s a n d P é n a u d R u d d e r.
C e r t i f i e d t o b y C h a s . M . M a n l y, A u g u s t 3 , 1 8 9 9 .
Sizes. Weight.
Parts.
m. ft. gr. lbs.
1 Frame, including everything of metal, permanent and undetachable,
such as bed-plate, cross-rods for the support of propellers, bearing 3556
points for clutch, etc.
2 Engine, complete 476
3 Pump, 301; pump shaft, 55; support to pump, 33 389
4 Hull covering, 276; apron, 117; piece behind separator 393
5 Gasoline and air tanks, 167, 165; air valve, 17 349
6 Smokestack and piece to protect midrod 385
7 Float, 290; drop piece for rudder, 57; guy-post and clamp, 17 364
8 Reel, fork and float, 128; steam gauge with pipe, 81 209
9 Wing claps, 202; guy-post clamps, 33 235
10 Boiler, 775; burner, 171; counter, 100 1046
11 Rear extension to midrod 227
12 Separator and pipes to engine and pump 513
13 Exhaust pipe 90
14 Front lower bearing points, 84; clutch post, 41 125
15 Rear bearing points, 146; extra strengtheners, 32 178
16
17 Wings (without clamp)
18 Tail (without clamp), part of rudder
19 Rudder 309
20 Guy sticks, each 60 120
21 Propellers, 100 cm. round end 757
22 Extra length of midrod, front 174
23 Wood bowsprit 130
24 Other things, 248 grammes of lead on end of bowsprit 248
25
26
27 Fuel (at starting flight)
28 Water (at starting flight)
29
30
31 Sundries unknown
32
33
Page 560
Sizes. Weight.
Parts.
m. ft. gr. lbs.
34 Total flying weight 14,354
35
36
37
38 Total area of support (not including tail) . . . sq. ft. 87.5
39 Total area of support in feet, divided by total flying weight in lbs. 2.75
40 Total area of horizontal tail. . . . sq. ft. 6.94
41 Total area of rudder (vertical). . . . sq. ft. 7.64
42 Horse-power at brake . . . Horse-power by formula*
43
44 Lift at pendulum (during one minute absolute)
45 Lift at pendulum (during one minute in terms of wt.)
46 Minimum pressure with which wheels turn
47 Position of center of pressure of wings†
48
49
50 Curvature of wings, 1 in 11
51 Root angle of wings, 10°
52 Tip angle of wings, 10°
53 Position of wings
54 How guyed
55
56
57
58 Position of tail
59 Angle of tail
60 Co-efficient elasticity of tail, 200 grammes at center gives deflection
of 5°
61 Position rudder
62 Elasticity caused by rubber bands
63 Line of thrust, 1500
64 Center of gravity1 of whole
65 Center of gravity2
66 Center of pressure1 of whole estimate
67 Center of pressure2
68
69
70
71
72
Parts.
m. ft. gr. lbs.
34 Total flying weight 14,354
35
36
37
38 Total area of support (not including tail) . . . sq. ft. 87.5
39 Total area of support in feet, divided by total flying weight in lbs. 2.75
40 Total area of horizontal tail. . . . sq. ft. 6.94
41 Total area of rudder (vertical). . . . sq. ft. 7.64
42 Horse-power at brake . . . Horse-power by formula*
43
44 Lift at pendulum (during one minute absolute)
45 Lift at pendulum (during one minute in terms of wt.)
46 Minimum pressure with which wheels turn
47 Position of center of pressure of wings†
48
49
50 Curvature of wings, 1 in 11
51 Root angle of wings, 10°
52 Tip angle of wings, 10°
53 Position of wings
54 How guyed
55
56
57
58 Position of tail
59 Angle of tail
60 Co-efficient elasticity of tail, 200 grammes at center gives deflection
of 5°
61 Position rudder
62 Elasticity caused by rubber bands
63 Line of thrust, 1500
64 Center of gravity1 of whole
65 Center of gravity2
66 Center of pressure1 of whole estimate
67 Center of pressure2
68
69
70
71
72
Page 561
Parts. Remarks.
1 C. P. on F. W., 1577.7.
2 Line through center of propellers, 1500.
6 C. of G., 1498.
8 C. P. on R. W., 1372.7.
Footnotes.
* H. P. = (Rev. × diam. × pitch ratio × thrust) /33000
† This is calculated on the assumption that the center of pressure on each wing or on pair of
wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from
front to rear, that for wings of usual size the rear wings have 2-3 of the efficiency per surface
of the front ones and that the tail proper bears no part of the weight; but if rear wing is
smaller or larger this efficiency is smaller or larger per unit of surface.
1 C. P. on F. W., 1577.7.
2 Line through center of propellers, 1500.
6 C. of G., 1498.
8 C. P. on R. W., 1372.7.
Footnotes.
* H. P. = (Rev. × diam. × pitch ratio × thrust) /33000
† This is calculated on the assumption that the center of pressure on each wing or on pair of
wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from
front to rear, that for wings of usual size the rear wings have 2-3 of the efficiency per surface
of the front ones and that the tail proper bears no part of the weight; but if rear wing is
smaller or larger this efficiency is smaller or larger per unit of surface.
Page 562
[p308]
DATA S HE E T No. 12.
We i g h t o f A e r o d r o m e , O n e - Q u a r t e r M o d e l . C e r t i f i e d t o b y C h a s . M .
M a n l y, J u n e 11 , 1 9 0 1 .
Sizes. Weight.
Parts.
m. ft. gr. lbs.
1 Frame, including everything of metal, permanent and undetachable,
such as bed-plate, cross-rods for the support of propellers, bearing 3245
points for clutch, etc.
2 Engine, bed plates and sparkers 4549 10
3 Gears, shafts, etc. 1662
4
5
6
7 Floats, front, 212; rear, 220 432
8 Reel, float and cord, 142 142
9 Wing clamps, 86 and 97; rudder clamp and post 183
10 Carburetor and fuel 737
11 Spark coil, 1512; holders, 110 1622
12 Battery 1627
13 Primary connections
14 Secondary connections
15 Guy-post clamps, each 13 26
16
17 Wings (without clamp), new flat wings 2634
18 Tail (without clamp), Pénaud rudder 353
19 Rudder, wind vane 88
20 Guy sticks 30
21 Propellers, 585 each 1170
22 Extra length of midrod, front, 125; rear, 225 350
23 Wood bowsprit 75
24 Other Things
25 Counter 110
26 Guy-post clamp and post for rudder 16
27
28
29 Drop piece for rudder 53
30
31 Sundries unknown
32
33
DATA S HE E T No. 12.
We i g h t o f A e r o d r o m e , O n e - Q u a r t e r M o d e l . C e r t i f i e d t o b y C h a s . M .
M a n l y, J u n e 11 , 1 9 0 1 .
Sizes. Weight.
Parts.
m. ft. gr. lbs.
1 Frame, including everything of metal, permanent and undetachable,
such as bed-plate, cross-rods for the support of propellers, bearing 3245
points for clutch, etc.
2 Engine, bed plates and sparkers 4549 10
3 Gears, shafts, etc. 1662
4
5
6
7 Floats, front, 212; rear, 220 432
8 Reel, float and cord, 142 142
9 Wing clamps, 86 and 97; rudder clamp and post 183
10 Carburetor and fuel 737
11 Spark coil, 1512; holders, 110 1622
12 Battery 1627
13 Primary connections
14 Secondary connections
15 Guy-post clamps, each 13 26
16
17 Wings (without clamp), new flat wings 2634
18 Tail (without clamp), Pénaud rudder 353
19 Rudder, wind vane 88
20 Guy sticks 30
21 Propellers, 585 each 1170
22 Extra length of midrod, front, 125; rear, 225 350
23 Wood bowsprit 75
24 Other Things
25 Counter 110
26 Guy-post clamp and post for rudder 16
27
28
29 Drop piece for rudder 53
30
31 Sundries unknown
32
33
Page 563
Sizes. Weight.
Parts.
m. ft. gr. lbs.
34 Total flying weight 19,104
35
36
37
38 Total area of support (not including tail) . . . sq. ft. 61.41
39 Total area of support in feet, divided by total flying weight in lbs. 1.46
40 Total area of horizontal tail. . . . sq. ft. 6
41 Total area of rudder (vertical). . . . sq. ft. 6
42 Horse-power at brake 1.5 at 750 R. P. M.
43 Engine gave 2.01 H. P. on brake at 900 R. P. M.
44 Lift at pendulum (during one minute absolute)
45 Lift at pendulum (during one minute in terms of wt.)
46 Minimum pressure with which wheels turn
47 Position of center of pressure of wings†
48
49
50 Curvature of wings, 1 in 20-1/2
51 Root angle of wings, 10°
52 Tip angle of wings, 10°
53 Position of wings: C. P. F. W., 157.82; C. P. R. W., 1386.9
54 How guyed
55 Position of tail
56 Angle of tail, 5°
57 Co-efficient elasticity of tail, 200 at center depresses to horizontal
58 Position of rudder (center), 1292.9
59
60 Line of thrust, 1500, through center of propellers
61 Center of gravity1 of whole, 1503.7
62 Center of gravity2, 2497.5
63 Center of pressure1 of whole estimate, 1503.7
64 Center of pressure2, 2513.2
65 Center of clutch post, 1515.4
66 Center of coil, 1555.3
67 Center front float, 16.45
68 Center rear float, 1372.6
69 Center wind vane rudder, 1435.6
70 Center Pénaud rudder, 1292.9
71 Rear end Pénaud rudder, 1215.9
72 Front end of Bowsprit, 1707.2
Parts.
m. ft. gr. lbs.
34 Total flying weight 19,104
35
36
37
38 Total area of support (not including tail) . . . sq. ft. 61.41
39 Total area of support in feet, divided by total flying weight in lbs. 1.46
40 Total area of horizontal tail. . . . sq. ft. 6
41 Total area of rudder (vertical). . . . sq. ft. 6
42 Horse-power at brake 1.5 at 750 R. P. M.
43 Engine gave 2.01 H. P. on brake at 900 R. P. M.
44 Lift at pendulum (during one minute absolute)
45 Lift at pendulum (during one minute in terms of wt.)
46 Minimum pressure with which wheels turn
47 Position of center of pressure of wings†
48
49
50 Curvature of wings, 1 in 20-1/2
51 Root angle of wings, 10°
52 Tip angle of wings, 10°
53 Position of wings: C. P. F. W., 157.82; C. P. R. W., 1386.9
54 How guyed
55 Position of tail
56 Angle of tail, 5°
57 Co-efficient elasticity of tail, 200 at center depresses to horizontal
58 Position of rudder (center), 1292.9
59
60 Line of thrust, 1500, through center of propellers
61 Center of gravity1 of whole, 1503.7
62 Center of gravity2, 2497.5
63 Center of pressure1 of whole estimate, 1503.7
64 Center of pressure2, 2513.2
65 Center of clutch post, 1515.4
66 Center of coil, 1555.3
67 Center front float, 16.45
68 Center rear float, 1372.6
69 Center wind vane rudder, 1435.6
70 Center Pénaud rudder, 1292.9
71 Rear end Pénaud rudder, 1215.9
72 Front end of Bowsprit, 1707.2
Page 564
Footnotes.
* H.P. = (Rev. × diam. × pitch ratio × thrust)/33000
† This is calculated on the assumption that the center of pressure on each wing or on pair of
wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from
front to rear, that for wings of usual size the rear wing have 2-3 of the efficiency per surface
of the front ones and that the tail proper bears no part of the weight; but if rear wing is
smaller or larger this efficiency is smaller or larger per unit of surface.
* H.P. = (Rev. × diam. × pitch ratio × thrust)/33000
† This is calculated on the assumption that the center of pressure on each wing or on pair of
wings at a motion of 2000 feet per minute is in ordinary curved wings 2-5 the way from
front to rear, that for wings of usual size the rear wing have 2-3 of the efficiency per surface
of the front ones and that the tail proper bears no part of the weight; but if rear wing is
smaller or larger this efficiency is smaller or larger per unit of surface.
Page 565
◊
INDEX
A
Abbreviations and symbols for points on aerodrome … 14, 15
Accidents, in launching large aerodrome … 126, 184, 185, 265–281
― loss of model aerodrome … 17, 94, 154
Aeolipiles, alcohol … 55, 56, 59, 60, 65, 66, 112
Aerial navigation, report of Board of Ordnance on … 276, 279
Aerodrome, balancing of … 45–52, 81, 90, 109, 134, 211, 212
― construction of … 53–80, 164–187, 234–250
― definition of word … iii
― dimensions of (see aerodrome models and data sheets).
― eighth-size model … 133, 134, 154
― engines (see engines and motors).
― experiments with models … 6–14, 16–24, 133–155
― field trials (see trials).
― first flight of model, May 6, 1896 … 2, 3, 107, 108, 117
― first trial of a “flying machine” in free air … 97
― flight (see also trials).
― ― first model, May 6, 1896 … 2, 3, 107, 117
― ― large machine (1903) … 126, 127, 255–282
― ― photographs of … 108, 259, 260
― large … 126, 127, 129, 130, 156, 183, 225, 255–282
― ― construction of … 164–187, 234–250
― ― launching apparatus for … 156–163, 183
― ― shop tests … 251–254
― ― trials (1903) … 126, 181, 255–282
― ― weight of … 277
― launching apparatus for models … 92–122, 133, 134
― ― ― ― large aerodrome … 156–163, 183
INDEX
A
Abbreviations and symbols for points on aerodrome … 14, 15
Accidents, in launching large aerodrome … 126, 184, 185, 265–281
― loss of model aerodrome … 17, 94, 154
Aeolipiles, alcohol … 55, 56, 59, 60, 65, 66, 112
Aerial navigation, report of Board of Ordnance on … 276, 279
Aerodrome, balancing of … 45–52, 81, 90, 109, 134, 211, 212
― construction of … 53–80, 164–187, 234–250
― definition of word … iii
― dimensions of (see aerodrome models and data sheets).
― eighth-size model … 133, 134, 154
― engines (see engines and motors).
― experiments with models … 6–14, 16–24, 133–155
― field trials (see trials).
― first flight of model, May 6, 1896 … 2, 3, 107, 108, 117
― first trial of a “flying machine” in free air … 97
― flight (see also trials).
― ― first model, May 6, 1896 … 2, 3, 107, 117
― ― large machine (1903) … 126, 127, 255–282
― ― photographs of … 108, 259, 260
― large … 126, 127, 129, 130, 156, 183, 225, 255–282
― ― construction of … 164–187, 234–250
― ― launching apparatus for … 156–163, 183
― ― shop tests … 251–254
― ― trials (1903) … 126, 181, 255–282
― ― weight of … 277
― launching apparatus for models … 92–122, 133, 134
― ― ― ― large aerodrome … 156–163, 183
Page 566
― man-carrying (see also aerodrome large) … 123, 125, 129, 130, 151, 153, 156–187, 234–250,
255, 282.
― model, descriptions of (see also data sheets).
― ― ― ― No. 0 … 21, 30, 31, 36, 38, 40, 53, 55, 75
― ― ― ― Nos. 1, 2, 3 … 28, 29, 38, 40, 53
― ― ― ― No. 4 … 53, 62–67, 69, 70, 72, 75–79, 81–83, 86, 92–109, 120
― ― ― ― No. 5 … 26, 64–66, 69, 70, 75–79, 81, 82–84, 86, 88, 89, 90, 92–109, 110–122, 130,
131, 134, 135–155, 158, 174, 188, 189, 208–210, 231, 257, 281.
― ― ― ― No. 6 … 49, 61, 62, 78–81, 89, 90, 92–109, 110–122, 130, 131, 134, 158, 174, 188,
193, 208, 210, 231, 257, 281.
― ― ― ― rubber pull … 11–20
― ― eighth-size … 133, 134, 154
― ― frames of … 39, 53–80, 90, 112, 119, 129
― ― launching apparatus for … 92–112, 134
― ― quarter-size … 158, 159, 170, 226–233, 234, 255, 257–261, 281
― ― results from … 17, 129
― ― steam driven (see also Nos. 5, 6) … 122, 164, 165, 224, 281
― ― trials, of Nos. 0, 1, 2, 3 (1892) … 29, 53
― ― ― ― Nos. 4, 5, 6 (1893) … 63, 92–106
― ― ― ― Nos. 5, 6 (1896) … 2, 79, 106–109
― ― ― ― No. 6 (1898) … 61
― ― ― ― Nos. 5, 6 (1899) … 49, 79, 135–155, 231, 257
― ― ― ― Nos. 30, 31, and others … 6–14, 17, 19
― motors (see engines and motors).
― quarter-size models (see aerodrome models).
― rubber-power models … 5, 8–24, 44
― weights of (see weight and data sheets).
Aerodromics, science of … iii, 7
Aerodynamics … 7, 30, 43, 44, 80, 91, 99
― experiments in … 1, 6, 7, 19, 21, 32, 41, 80, 98, 128, 150, 153
Aeronaut (see also aviator) … 130
Air, compressed … 11, 24, 25, 26, 68, 112
― liquid … 154
― resistance of … 6, 8, 9, 142, 165–167
Air-chamber … 64, 68, 69, 98, 112, 113
Air-cooled engine … 226
255, 282.
― model, descriptions of (see also data sheets).
― ― ― ― No. 0 … 21, 30, 31, 36, 38, 40, 53, 55, 75
― ― ― ― Nos. 1, 2, 3 … 28, 29, 38, 40, 53
― ― ― ― No. 4 … 53, 62–67, 69, 70, 72, 75–79, 81–83, 86, 92–109, 120
― ― ― ― No. 5 … 26, 64–66, 69, 70, 75–79, 81, 82–84, 86, 88, 89, 90, 92–109, 110–122, 130,
131, 134, 135–155, 158, 174, 188, 189, 208–210, 231, 257, 281.
― ― ― ― No. 6 … 49, 61, 62, 78–81, 89, 90, 92–109, 110–122, 130, 131, 134, 158, 174, 188,
193, 208, 210, 231, 257, 281.
― ― ― ― rubber pull … 11–20
― ― eighth-size … 133, 134, 154
― ― frames of … 39, 53–80, 90, 112, 119, 129
― ― launching apparatus for … 92–112, 134
― ― quarter-size … 158, 159, 170, 226–233, 234, 255, 257–261, 281
― ― results from … 17, 129
― ― steam driven (see also Nos. 5, 6) … 122, 164, 165, 224, 281
― ― trials, of Nos. 0, 1, 2, 3 (1892) … 29, 53
― ― ― ― Nos. 4, 5, 6 (1893) … 63, 92–106
― ― ― ― Nos. 5, 6 (1896) … 2, 79, 106–109
― ― ― ― No. 6 (1898) … 61
― ― ― ― Nos. 5, 6 (1899) … 49, 79, 135–155, 231, 257
― ― ― ― Nos. 30, 31, and others … 6–14, 17, 19
― motors (see engines and motors).
― quarter-size models (see aerodrome models).
― rubber-power models … 5, 8–24, 44
― weights of (see weight and data sheets).
Aerodromics, science of … iii, 7
Aerodynamics … 7, 30, 43, 44, 80, 91, 99
― experiments in … 1, 6, 7, 19, 21, 32, 41, 80, 98, 128, 150, 153
Aeronaut (see also aviator) … 130
Air, compressed … 11, 24, 25, 26, 68, 112
― liquid … 154
― resistance of … 6, 8, 9, 142, 165–167
Air-chamber … 64, 68, 69, 98, 112, 113
Air-cooled engine … 226
Page 567
Alcohol and hydrocarbons, use of, as fuel … 24, 25, 35, 55, 57, 66, 72, 73
Alcohol aeolipiles … 55, 56, 60, 66, 69, 112
Allegheny Observatory, experiments at … 11, 13, 31, 150
Allotment, Government, for man-carrying aerodrome … 124–126, 132, 278
Aluminum-bronze, use of … 114, 116, 173, 174
Aluminum in engine construction … 32, 114, 243, 252
― sheathing of hull … 69
― wires … 84
Aneroid barometer for determining height … 186
Anemometer cups … 143
Angle, diedral, of wings … 45, 82, 89
― of inclination … 41, 43, 83, 99, 100
― ― rotation … 61
― ― wings, root angle … 83, 89, 91, 97, 98, 100, 101, 103
Area, relation to weight and power … 43, 44, 64, 90, 99, 101
― supporting (see also surface) … 82, 87–89, 91, 93
Asbestos, use of … 35, 63, 67
Associated Press statement to … 266, 280
Aviator, equilibrium of … 161, 169, 253
― weight of … 130, 210, 256
Aviator’s car … 185–187, 214, 251, 252
― jacket … 273
― seat … 185
― wheel … 214, 216, 265, 266, 272
B
Bagging or pocketing of wings … 84, 86, 100, 195, 203
Balance (see also equilibrium) … 82, 165
Balancing of aerodrome … 45–52, 81, 90, 109, 134, 211, 258
― ― engine … 246, 247
― ― wings and rudder … 211, 255
Ball-bearings on launching car … 160, 175, 177, 252, 253
Bamboo ribs for wings … 200
Barometer, aneroid … 186
Barus, Dr Carl, boiler experiments by … 58, 70–75, 93–95
Batteries, electric … 11, 24, 26, 27, 162, 212, 220–222, 237, 240, 241, 257, 262, 263
Bearings, ball, on aerodrome and launching car … 160, 175, 177, 252, 253
Alcohol aeolipiles … 55, 56, 60, 66, 69, 112
Allegheny Observatory, experiments at … 11, 13, 31, 150
Allotment, Government, for man-carrying aerodrome … 124–126, 132, 278
Aluminum-bronze, use of … 114, 116, 173, 174
Aluminum in engine construction … 32, 114, 243, 252
― sheathing of hull … 69
― wires … 84
Aneroid barometer for determining height … 186
Anemometer cups … 143
Angle, diedral, of wings … 45, 82, 89
― of inclination … 41, 43, 83, 99, 100
― ― rotation … 61
― ― wings, root angle … 83, 89, 91, 97, 98, 100, 101, 103
Area, relation to weight and power … 43, 44, 64, 90, 99, 101
― supporting (see also surface) … 82, 87–89, 91, 93
Asbestos, use of … 35, 63, 67
Associated Press statement to … 266, 280
Aviator, equilibrium of … 161, 169, 253
― weight of … 130, 210, 256
Aviator’s car … 185–187, 214, 251, 252
― jacket … 273
― seat … 185
― wheel … 214, 216, 265, 266, 272
B
Bagging or pocketing of wings … 84, 86, 100, 195, 203
Balance (see also equilibrium) … 82, 165
Balancing of aerodrome … 45–52, 81, 90, 109, 134, 211, 258
― ― engine … 246, 247
― ― wings and rudder … 211, 255
Ball-bearings on launching car … 160, 175, 177, 252, 253
Bamboo ribs for wings … 200
Barometer, aneroid … 186
Barus, Dr Carl, boiler experiments by … 58, 70–75, 93–95
Batteries, electric … 11, 24, 26, 27, 162, 212, 220–222, 237, 240, 241, 257, 262, 263
Bearings, ball, on aerodrome and launching car … 160, 175, 177, 252, 253
Page 568
― bronze, on model aerodromes … 177
Bedplates … 116, 168, 175, 273
“Beehive” boilers (see boilers).
Bell Alexander Graham … 4, 96, 102–104, 106, 108
Bessemer steel guy wires … 172
Bevel gears … 174, 177, 241
Bird-wings, construction of … 7, 188, 200, 201
Birds, soaring, study of … 7, 9, 88, 287
Blazer, S. M., engineer … 126
“Bleeder,” feed tube for burner … 67, 113
Blériot aeroplane of Langley type … 283
Blower for artificial wind … 61, 97, 225
Board of Ordnance and Fortification … 124, 126, 132, 250, 255, 271, 276, 278, 279, 280
Boat, house … 92, 93, 136, 148, 149, 156–163, 269
Body, construction of (see also hull) … 32, 60
Boiler, “Beehive” type … 34, 39
― coil of … 34–39, 70, 71, 113–116
― development of … 55–59, 65, 68, 70–75, 102, 114–116
― pressure … 58, 59, 63, 68, 69, 101, 102
― report on, by Dr. Barus … 70–75
― serpollet type … 56, 57
― spray type … 70
― tests of … 70–75, 135
― tubing of … 70–75, 114, 141
― water-tube type of … 34, 35, 70–75, 114
Bolometer, development of … 123
Brake, horse-power … 28, 37, 58, 61, 64–69, 117, 223, 224, 230, 233
― Prony … 38, 61, 65, 66, 117, 179, 222, 228, 233, 249
Brass, use of … 54, 63, 113, 180
Brazing … 117, 173, 175, 235, 236
Bronze, aluminum … 114, 116, 171, 173, 177, 234, 237–240
Burners, Bunsen type … 35, 68, 72, 113
― gasoline … 56, 60, 61, 62, 65, 67, 68, 70–75, 112–116, 149
― shield for … 60, 67, 95, 115
Bushing, cast-iron … 114–117, 121
Buzzard, American, and “John Crow,” study of … 285
Bedplates … 116, 168, 175, 273
“Beehive” boilers (see boilers).
Bell Alexander Graham … 4, 96, 102–104, 106, 108
Bessemer steel guy wires … 172
Bevel gears … 174, 177, 241
Bird-wings, construction of … 7, 188, 200, 201
Birds, soaring, study of … 7, 9, 88, 287
Blazer, S. M., engineer … 126
“Bleeder,” feed tube for burner … 67, 113
Blériot aeroplane of Langley type … 283
Blower for artificial wind … 61, 97, 225
Board of Ordnance and Fortification … 124, 126, 132, 250, 255, 271, 276, 278, 279, 280
Boat, house … 92, 93, 136, 148, 149, 156–163, 269
Body, construction of (see also hull) … 32, 60
Boiler, “Beehive” type … 34, 39
― coil of … 34–39, 70, 71, 113–116
― development of … 55–59, 65, 68, 70–75, 102, 114–116
― pressure … 58, 59, 63, 68, 69, 101, 102
― report on, by Dr. Barus … 70–75
― serpollet type … 56, 57
― spray type … 70
― tests of … 70–75, 135
― tubing of … 70–75, 114, 141
― water-tube type of … 34, 35, 70–75, 114
Bolometer, development of … 123
Brake, horse-power … 28, 37, 58, 61, 64–69, 117, 223, 224, 230, 233
― Prony … 38, 61, 65, 66, 117, 179, 222, 228, 233, 249
Brass, use of … 54, 63, 113, 180
Brazing … 117, 173, 175, 235, 236
Bronze, aluminum … 114, 116, 171, 173, 177, 234, 237–240
Burners, Bunsen type … 35, 68, 72, 113
― gasoline … 56, 60, 61, 62, 65, 67, 68, 70–75, 112–116, 149
― shield for … 60, 67, 95, 115
Bushing, cast-iron … 114–117, 121
Buzzard, American, and “John Crow,” study of … 285
Page 569
C
Cameras, telephoto … 260, 261, 273
“Canvas-covered” propellers … 84, 178
Car, aviator’s … 185–187, 214, 251, 252
― launching (see launching apparatus).
Carbon, energy developed by the use of … 27
Carbonic-acid gas as motive power … 11, 24, 26, 28, 29, 39, 53, 54
― liquid … 24, 28
― ― freezing of … 28–29
― ― latent heat of … 28
Carburetor, development of, suitable type of … 224, 225, 239, 240, 248, 249, 251, 253, 259
Carpenter, Frank G., witnesses flights … 108
Cast-iron, use of (see also iron) … 114–117, 121, 234–236, 240
“Cast-off” apparatus … 96, 110
Center of gravity … 10, 13–16, 45–52, 61, 64, 80, 91, 103, 143, 144, 150, 209, 210
― ― ― in relation to pressure … 10, 11, 15, 46, 48, 64, 98, 99, 101, 103
― ― pressure … 7, 10, 11, 13, 15, 45–52, 78, 80, 84, 87, 88, 90, 91, 200, 209, 210
― ― ― formulæ for … 49, 87, 88, 90
― ― wings and tail … 16
― ― rotation … 62
― ― thrust … 62
Centrifugal pump … 241, 248
Charcoal, as fuel … 57
China silk (see silk).
Chopawamsic Island, Potomac River … 93, 135, 153, 183, 256
Chronograph attachments … 162, 163, 229
Circulating pump … 114, 244
Clamps, wing … 82, 89, 145, 183
Coast and Geodetic Survey … 93, 145, 256
Coefficient of elasticity … 146
Coil, spark (see sparking devices).
Compressed air … 24, 25–26, 68, 112, 113
Condenser, steam … 65
Construction and tests of large engine … 234–250
Construction of frame and engines … 53–80
― ― ― of large aerodrome … 164–187
Cameras, telephoto … 260, 261, 273
“Canvas-covered” propellers … 84, 178
Car, aviator’s … 185–187, 214, 251, 252
― launching (see launching apparatus).
Carbon, energy developed by the use of … 27
Carbonic-acid gas as motive power … 11, 24, 26, 28, 29, 39, 53, 54
― liquid … 24, 28
― ― freezing of … 28–29
― ― latent heat of … 28
Carburetor, development of, suitable type of … 224, 225, 239, 240, 248, 249, 251, 253, 259
Carpenter, Frank G., witnesses flights … 108
Cast-iron, use of (see also iron) … 114–117, 121, 234–236, 240
“Cast-off” apparatus … 96, 110
Center of gravity … 10, 13–16, 45–52, 61, 64, 80, 91, 103, 143, 144, 150, 209, 210
― ― ― in relation to pressure … 10, 11, 15, 46, 48, 64, 98, 99, 101, 103
― ― pressure … 7, 10, 11, 13, 15, 45–52, 78, 80, 84, 87, 88, 90, 91, 200, 209, 210
― ― ― formulæ for … 49, 87, 88, 90
― ― wings and tail … 16
― ― rotation … 62
― ― thrust … 62
Centrifugal pump … 241, 248
Charcoal, as fuel … 57
China silk (see silk).
Chopawamsic Island, Potomac River … 93, 135, 153, 183, 256
Chronograph attachments … 162, 163, 229
Circulating pump … 114, 244
Clamps, wing … 82, 89, 145, 183
Coast and Geodetic Survey … 93, 145, 256
Coefficient of elasticity … 146
Coil, spark (see sparking devices).
Compressed air … 24, 25–26, 68, 112, 113
Condenser, steam … 65
Construction and tests of large engine … 234–250
Construction of frame and engines … 53–80
― ― ― of large aerodrome … 164–187
Page 570
― ― supporting surfaces … 188–206
Control, equilibrium and … 77, 78, 119, 207–217
― gyroscopic … 78, 211
Cooling systems, (see water and air cooling).
Copper, use of … 27, 39, 63, 72, 112–115, 162
Copper tubing … 35, 56, 57, 59, 112, 115, 140, 141, 248
Counter, speed … 62, 120, 185, 243, 249
― ― propellers … 178
Covering for tail … 86, 103
― ― wings … 54, 63, 77, 81, 86, 88, 90, 148, 194, 195, 205
Crank bell … 110
― starting … 244
Crank-pin … 237–239, 243–247
Crank-shaft … 237, 239, 244–246, 250
Cube, law of the … 129, 130, 222, 244, 249
Currie, Rolla P., report on American Buzzard … 289
Curved surfaces (see also wing curvature) … 18, 44, 47, 99
Cylinders (see also engines, cylinders).
― aluminum in construction of … 114
― brass in construction of … 54
― steel tubes in … 116, 121, 234, 235, 239, 240
― construction of … 112, 114, 116, 121, 212, 213, 232, 235, 239, 240, 246
― five, engine … 245, 246, 250, 255
― high-pressure … 33
― low-pressure … 33
― multiple, engine … 226
― oscillating … 33, 38
― tests of (see also engine tests) … 55
― walls of … 239
― weight of … 246, 247, 250
D
Daniell, on energy in storage batteries … 27
Data sheets … 297
Definitions of terms and symbols … 14, 15
Deflection, absence of … 269
de Lucy, on sustaining surfaces … 19
Control, equilibrium and … 77, 78, 119, 207–217
― gyroscopic … 78, 211
Cooling systems, (see water and air cooling).
Copper, use of … 27, 39, 63, 72, 112–115, 162
Copper tubing … 35, 56, 57, 59, 112, 115, 140, 141, 248
Counter, speed … 62, 120, 185, 243, 249
― ― propellers … 178
Covering for tail … 86, 103
― ― wings … 54, 63, 77, 81, 86, 88, 90, 148, 194, 195, 205
Crank bell … 110
― starting … 244
Crank-pin … 237–239, 243–247
Crank-shaft … 237, 239, 244–246, 250
Cube, law of the … 129, 130, 222, 244, 249
Currie, Rolla P., report on American Buzzard … 289
Curved surfaces (see also wing curvature) … 18, 44, 47, 99
Cylinders (see also engines, cylinders).
― aluminum in construction of … 114
― brass in construction of … 54
― steel tubes in … 116, 121, 234, 235, 239, 240
― construction of … 112, 114, 116, 121, 212, 213, 232, 235, 239, 240, 246
― five, engine … 245, 246, 250, 255
― high-pressure … 33
― low-pressure … 33
― multiple, engine … 226
― oscillating … 33, 38
― tests of (see also engine tests) … 55
― walls of … 239
― weight of … 246, 247, 250
D
Daniell, on energy in storage batteries … 27
Data sheets … 297
Definitions of terms and symbols … 14, 15
Deflection, absence of … 269
de Lucy, on sustaining surfaces … 19
Page 571
Diedral angle of wings … 45, 82, 83, 85, 89, 96, 146
Dimensions (see aerodrome descriptions and data sheets).
Distance of flights … 103, 107–109, 135–155, 258
Distortion of wings … 82–84, 91, 98, 105
Dry batteries … 262
Duration of flights (see also time) … 103, 107, 108, 137, 145, 148, 258
Dynamometer, use of … 222, 228, 229, 230, 242, 247, 249
E
Eagle quill and spruce rib, comparative strength of … 201
Early steam motors and other models … 30–40
Efficiency of wings … 87, 89, 91, 144, 192, 193
Eighth-size models … 133, 134, 154
Elastic limit of rubber … 9, 22, 23
Elasticity of tail … 78, 90, 144, 152
― coefficient of … 51, 144, 146
Electric batteries … 24, 26, 27, 212, 262, 263
― circuits … 70, 212, 220–223, 237, 241, 257
Electricity as motive power … 24, 26–28
Energy in foot pounds (see also lift) … 23–27
Engine (see also motors) … 112–116, 179, 180, 222–225, 226–233, 234–250, 281
― American builders … 131, 180, 219, 228
― air-cooled … 226
― automobile … 219
― balancing of … 246, 247
― carbonic-acid gas … 24, 26–29
― compressed air … 11, 24–26, 68, 112
― construction of, and frames … 53–79, 114, 116, 219, 223–233
― ― ― ― tests … 234–250
― contract for … 126
― cylinders of … 33, 38, 54, 112, 114–116, 121, 212, 213, 232, 235–239, 246, 250, 255
― description of one-horse-power … 37, 116
― electric … 24, 26–28
― European builders … 131, 140, 219, 234
― experimental … 218–225
― five-cylinder … 224, 232, 234–250, 255
― gas (see also gasoline) … 26, 28, 131, 133
Dimensions (see aerodrome descriptions and data sheets).
Distance of flights … 103, 107–109, 135–155, 258
Distortion of wings … 82–84, 91, 98, 105
Dry batteries … 262
Duration of flights (see also time) … 103, 107, 108, 137, 145, 148, 258
Dynamometer, use of … 222, 228, 229, 230, 242, 247, 249
E
Eagle quill and spruce rib, comparative strength of … 201
Early steam motors and other models … 30–40
Efficiency of wings … 87, 89, 91, 144, 192, 193
Eighth-size models … 133, 134, 154
Elastic limit of rubber … 9, 22, 23
Elasticity of tail … 78, 90, 144, 152
― coefficient of … 51, 144, 146
Electric batteries … 24, 26, 27, 212, 262, 263
― circuits … 70, 212, 220–223, 237, 241, 257
Electricity as motive power … 24, 26–28
Energy in foot pounds (see also lift) … 23–27
Engine (see also motors) … 112–116, 179, 180, 222–225, 226–233, 234–250, 281
― American builders … 131, 180, 219, 228
― air-cooled … 226
― automobile … 219
― balancing of … 246, 247
― carbonic-acid gas … 24, 26–29
― compressed air … 11, 24–26, 68, 112
― construction of, and frames … 53–79, 114, 116, 219, 223–233
― ― ― ― tests … 234–250
― contract for … 126
― cylinders of … 33, 38, 54, 112, 114–116, 121, 212, 213, 232, 235–239, 246, 250, 255
― description of one-horse-power … 37, 116
― electric … 24, 26–28
― European builders … 131, 140, 219, 234
― experimental … 218–225
― five-cylinder … 224, 232, 234–250, 255
― gas (see also gasoline) … 26, 28, 131, 133
Page 572
― gasoline … 24, 37, 65, 125, 131, 179, 210, 218, 219, 224, 277
― gunpowder … 24, 25
― horse-power (see also brake, horse-power) … 37, 58, 116, 233
― hot-water … 24, 25, 68
― large, construction and tests of … 133, 234–250, 281, 282
― ― weight of … 247, 250, 256
― Manly … 219–225
― multiple cylinder … 226
― oscillating … 33, 38
― radiator … 252
― steam … 24, 30–40, 64, 69, 116, 120
― ― dimensions of … 116
― Stringfellow … 30, 31
― tests … 37, 55, 61, 69, 102, 133, 148, 234–250, 281, 282
― water-cooled … 220, 235, 236, 241, 247, 248, 252
― weight of … 116, 126, 130, 209, 247, 250
Equilibrium, maintenance of … 6, 31, 45, 51, 144, 213–216
― of aviator … 161, 169, 213, 253
― and control … 77, 78, 119, 207–217
― lateral, and longitudinal stability … 31, 45–52
Evaporation, rate of gasoline … 65, 66
Evaporators … 37, 65, 67, 114, 148
F
“Factor of safety” … 111, 186
Feathers, pliability of … 188, 200
― toy-propeller, blades made of … 8
Feed, gravity … 239
Fibre insulation … 241, 257
Field trials, eighth-size … 133, 134, 154
― ― large and quarto size models … 126, 158, 170, 181, 226–234, 255–282
― ― models Nos. 0, 1, 2, 3 … 29, 53
― ― ― Nos. 4, 5, 6 … 63, 92–106
― ― ― Nos. 5, 6, 2 … 61, 79, 135–155, 231, 257
Fire-proofing preparation … 148
First flight of heavier than air machine … 107, 108
First trial of a flying-machine in free air … 97
― gunpowder … 24, 25
― horse-power (see also brake, horse-power) … 37, 58, 116, 233
― hot-water … 24, 25, 68
― large, construction and tests of … 133, 234–250, 281, 282
― ― weight of … 247, 250, 256
― Manly … 219–225
― multiple cylinder … 226
― oscillating … 33, 38
― radiator … 252
― steam … 24, 30–40, 64, 69, 116, 120
― ― dimensions of … 116
― Stringfellow … 30, 31
― tests … 37, 55, 61, 69, 102, 133, 148, 234–250, 281, 282
― water-cooled … 220, 235, 236, 241, 247, 248, 252
― weight of … 116, 126, 130, 209, 247, 250
Equilibrium, maintenance of … 6, 31, 45, 51, 144, 213–216
― of aviator … 161, 169, 213, 253
― and control … 77, 78, 119, 207–217
― lateral, and longitudinal stability … 31, 45–52
Evaporation, rate of gasoline … 65, 66
Evaporators … 37, 65, 67, 114, 148
F
“Factor of safety” … 111, 186
Feathers, pliability of … 188, 200
― toy-propeller, blades made of … 8
Feed, gravity … 239
Fibre insulation … 241, 257
Field trials, eighth-size … 133, 134, 154
― ― large and quarto size models … 126, 158, 170, 181, 226–234, 255–282
― ― models Nos. 0, 1, 2, 3 … 29, 53
― ― ― Nos. 4, 5, 6 … 63, 92–106
― ― ― Nos. 5, 6, 2 … 61, 79, 135–155, 231, 257
Fire-proofing preparation … 148
First flight of heavier than air machine … 107, 108
First trial of a flying-machine in free air … 97
Page 573
Flexure of wings … 82–84, 91, 98, 105
Flight (see aerodrome and aerodrome model flights).
― bird, study of … 7
― of large machine … 126, 181, 255–282
― ― May 6, 1896 … 2, 3, 107–108
― ― models Nos. 4, 5, 6 … 2, 63, 79, 92–109, 135–155
― ― quarter size model … 259
― ― rubber-driven models … 16–20
― ― quarter-size models … 158, 170, 226–233, 243, 255, 257–261, 281
Floating the models … 64, 68, 69, 99, 103, 119, 120
Fly-wheels of engine … 242, 243, 247, 252
Flying aerodrome model as a kite … 133, 154, 155
Flying-weight of aerodromes (see also data sheets) … 15, 62, 63, 76, 77, 81, 89, 91, 148, 247, 250,
256
Foot-pounds, definition of … 15
― energy in (see also horse-power) … 22, 27, 62
Force-pump … 57
Formulæ:
― area … 19
― center of pressure … 49, 87, 88, 90, 101
― drift … 41, 43
― efficiency … 47
― Harting’s … 19
― horse-power … 15, 62
― lift or weight … 41, 43, 62
― Manly’s, for changing center of pressure … 51
― Maxim’s, for horse-power … 15
― resistance … 41
― soaring speed … 91
― tandem wing … 87
― work (see also horse-power) … 18, 23, 27, 62
Frame, construction of, model … 39, 53–80, 90, 112, 119, 129
― ― ― large aerodrome … 164–187, 253
― main … 165–168, 170
― resistance of … 165–167
― testing of … 79
Flight (see aerodrome and aerodrome model flights).
― bird, study of … 7
― of large machine … 126, 181, 255–282
― ― May 6, 1896 … 2, 3, 107–108
― ― models Nos. 4, 5, 6 … 2, 63, 79, 92–109, 135–155
― ― quarter size model … 259
― ― rubber-driven models … 16–20
― ― quarter-size models … 158, 170, 226–233, 243, 255, 257–261, 281
Floating the models … 64, 68, 69, 99, 103, 119, 120
Fly-wheels of engine … 242, 243, 247, 252
Flying aerodrome model as a kite … 133, 154, 155
Flying-weight of aerodromes (see also data sheets) … 15, 62, 63, 76, 77, 81, 89, 91, 148, 247, 250,
256
Foot-pounds, definition of … 15
― energy in (see also horse-power) … 22, 27, 62
Force-pump … 57
Formulæ:
― area … 19
― center of pressure … 49, 87, 88, 90, 101
― drift … 41, 43
― efficiency … 47
― Harting’s … 19
― horse-power … 15, 62
― lift or weight … 41, 43, 62
― Manly’s, for changing center of pressure … 51
― Maxim’s, for horse-power … 15
― resistance … 41
― soaring speed … 91
― tandem wing … 87
― work (see also horse-power) … 18, 23, 27, 62
Frame, construction of, model … 39, 53–80, 90, 112, 119, 129
― ― ― large aerodrome … 164–187, 253
― main … 165–168, 170
― resistance of … 165–167
― testing of … 79
Page 574
― transverse … 77, 165, 174–178
― work … 118
French academy, communication to … 3
Fuel, alcohol and hydrocarbon … 24, 25, 35, 55, 57, 66, 72, 73
― carbon … 27
― carbonic acid gas … 11, 24, 26, 28, 29, 39, 53, 54
― charcoal … 57
― gas … 26, 28, 37
― gasoline … 24, 25, 36, 37, 65–68, 112, 125, 224, 248, 259
― quantity of … 68
Fuel-tank … 36, 65, 67, 68, 112, 113
Funds for experiments … 124–126, 132, 257, 278, 279, 281
G
Gaertner, Mr., instrument maker … 93, 95
Gas, carbonic-acid … 24, 26, 28, 36, 68, 113
Gas-burners … 35, 55, 60, 65, 70–75, 112, 113
Gas-engine (see also engines, gas and gasoline) … 26, 28, 37
― Five cylinder … 224, 234–250, 255
― large … 234–250, 277
― model … 26–28, 65, 131, 133, 232–234
Gasoline-burners … 56, 60, 62, 65, 67, 68, 70–75, 112–116, 149
Gasoline-engines … 24, 37, 65, 125, 131, 179, 210, 218–225, 232–234, 248, 259, 277
Gasoline-evaporator … 37, 65, 148
Gears … 114, 117, 136, 137, 168, 174, 175, 177, 237, 241
Gibson, Captain, recorder … 250
Goldbeater’s skin, for wings … 77
Goode, G. Brown … 97
Government allotment (see also Board of Ordnance and Fortification) … 124–126, 132, 279
Gravity, center of … 10, 13–16, 45–52, 61, 64, 80, 91, 98, 101, 103, 143, 144, 150, 209, 210
Gravity-feed … 239
Guiding (see equilibrium and control; sustaining surfaces; and rudder).
Gun-metal … 174
Gunpowder … 24, 25
Guy-posts … 184, 189, 199, 266, 267, 268, 270, 274, 275
Guying, early systems of … 81, 84–91
― wire … 81, 84–90, 99, 164–173, 189, 191, 196, 199, 264, 266
― work … 118
French academy, communication to … 3
Fuel, alcohol and hydrocarbon … 24, 25, 35, 55, 57, 66, 72, 73
― carbon … 27
― carbonic acid gas … 11, 24, 26, 28, 29, 39, 53, 54
― charcoal … 57
― gas … 26, 28, 37
― gasoline … 24, 25, 36, 37, 65–68, 112, 125, 224, 248, 259
― quantity of … 68
Fuel-tank … 36, 65, 67, 68, 112, 113
Funds for experiments … 124–126, 132, 257, 278, 279, 281
G
Gaertner, Mr., instrument maker … 93, 95
Gas, carbonic-acid … 24, 26, 28, 36, 68, 113
Gas-burners … 35, 55, 60, 65, 70–75, 112, 113
Gas-engine (see also engines, gas and gasoline) … 26, 28, 37
― Five cylinder … 224, 234–250, 255
― large … 234–250, 277
― model … 26–28, 65, 131, 133, 232–234
Gasoline-burners … 56, 60, 62, 65, 67, 68, 70–75, 112–116, 149
Gasoline-engines … 24, 37, 65, 125, 131, 179, 210, 218–225, 232–234, 248, 259, 277
Gasoline-evaporator … 37, 65, 148
Gears … 114, 117, 136, 137, 168, 174, 175, 177, 237, 241
Gibson, Captain, recorder … 250
Goldbeater’s skin, for wings … 77
Goode, G. Brown … 97
Government allotment (see also Board of Ordnance and Fortification) … 124–126, 132, 279
Gravity, center of … 10, 13–16, 45–52, 61, 64, 80, 91, 98, 101, 103, 143, 144, 150, 209, 210
Gravity-feed … 239
Guiding (see equilibrium and control; sustaining surfaces; and rudder).
Gun-metal … 174
Gunpowder … 24, 25
Guy-posts … 184, 189, 199, 266, 267, 268, 270, 274, 275
Guying, early systems of … 81, 84–91
― wire … 81, 84–90, 99, 164–173, 189, 191, 196, 199, 264, 266
Page 575
Gyroscopic control … 78, 211
H
Harting’s formula … 19
Head resistance … 142, 165–167
Heating apparatus (see burners).
Herring, A. M., assistant … 104
Hewitt, Mr., at rescue of Mr. Manly … 273
Hodgkin’s fund, aid from … 257
Holmes, W. H. … 286, 289
Horizontal flight, velocity required to sustain … 1, 16–19, 43, 91
― rudder … 8
Horse-power, exerted by rubber … 9, 22
― Maxim’s formula … 15
― required to sustain flight … 1
― developed … 28, 37, 55, 58, 64–69, 117, 179, 223, 233, 249
Hot-water engine … 24, 25
House-boat and launching apparatus … 92–109, 110–122, 148, 149, 156, 163, 269
Huffaker, E. C. … 44, 46
Hull, construction of … 30, 32, 36, 53, 60, 69, 75, 112, 118–121
― forms of … 30, 31, 32, 38, 60, 69
― resistance … 49, 69
― steel tubes for … 39, 69, 75, 112, 118, 120
I
Ignition (see electric batteries and circuits).
Indian rubber for power (see also rubber) … 21, 40
Internal work of the wind … 6, 42
Inclination, angle of … 41, 43, 83, 99, 100
Insulation … 144, 241, 257
Iron, use of … 63, 64, 114–117, 234, 236, 240
J
Jacket, cork, aviator’s … 273
― water … 220, 234, 236, 241, 247, 252
“John Crow” (bird of Jamaica), study of … 285
K
Kite, model flown as … 133, 154, 155
L
H
Harting’s formula … 19
Head resistance … 142, 165–167
Heating apparatus (see burners).
Herring, A. M., assistant … 104
Hewitt, Mr., at rescue of Mr. Manly … 273
Hodgkin’s fund, aid from … 257
Holmes, W. H. … 286, 289
Horizontal flight, velocity required to sustain … 1, 16–19, 43, 91
― rudder … 8
Horse-power, exerted by rubber … 9, 22
― Maxim’s formula … 15
― required to sustain flight … 1
― developed … 28, 37, 55, 58, 64–69, 117, 179, 223, 233, 249
Hot-water engine … 24, 25
House-boat and launching apparatus … 92–109, 110–122, 148, 149, 156, 163, 269
Huffaker, E. C. … 44, 46
Hull, construction of … 30, 32, 36, 53, 60, 69, 75, 112, 118–121
― forms of … 30, 31, 32, 38, 60, 69
― resistance … 49, 69
― steel tubes for … 39, 69, 75, 112, 118, 120
I
Ignition (see electric batteries and circuits).
Indian rubber for power (see also rubber) … 21, 40
Internal work of the wind … 6, 42
Inclination, angle of … 41, 43, 83, 99, 100
Insulation … 144, 241, 257
Iron, use of … 63, 64, 114–117, 234, 236, 240
J
Jacket, cork, aviator’s … 273
― water … 220, 234, 236, 241, 247, 252
“John Crow” (bird of Jamaica), study of … 285
K
Kite, model flown as … 133, 154, 155
L
Page 576
Langley. S. P. … 3, 4, 9, 18, 76–79, 93, 95, 102–108, 112, 123–126, 128, 131, 133, 135, 153, 156,
161, 179, 183, 184, 188, 211, 212, 219, 223, 230, 231, 257, 266–268, 270, 271, 287, 280, 281
― statement of … 124, 280
― letter of instructions from (see appendix).
― study of “John Crow” bird (see appendix).
― aerodrome, War Department report on … 277, 278, 279
“Langley type” of aerodrome … 77, 164, 208, 244, 266, 276, 278–281
― ― ― rudder … 77, 86
Lateral stability … 45–52, 97
Launching, difficulties of … 10, 11, 12, 92, 94, 96, 99
― methods of … 13, 94–97, 110
― of large machine … 265–267, 271–272, 276, 282
Launching-apparatus … 92–122, 134, 149, 156–163, 183, 185, 231, 257, 261, 265–267, 270, 272,
276, 282
― overhead … 5, 92–122, 133–135, 139, 142, 143, 145, 151, 152, 154, 156–163
― underneath … 134, 135, 145–147, 151, 152, 154, 156–163, 183
― weakness of … 265, 276, 282
Launching-car … 158, 159, 183, 184, 255, 258, 262, 266–268, 271, 272, 274, 277
Launching speed (see also velocity) … 135, 161, 162
Law of the cube … 129, 130
Lewis, Captain I. N. … 250
Lift of propellers (see also pendulum tests) … 61, 62, 66, 69, 77, 94, 99, 102, 105, 107, 151, 189,
192
Lilienthal, Otto, on efficiency of curves … 44
Lineal velocity … 1, 43, 110, 166
Liquid air … 154
Longitudinal stability … 45–52
Lubrication … 113, 177, 234, 239, 240
M
McDonald, Mr. … 266, 271, 272
McKinley, President William … 123, 124
Macomb, Major M. M., report of … 276–278
Maltby, Mr., machinist … 93–95, 102, 106
Man-carrying machine … 123, 125, 129, 130, 151, 153, 156–187, 234–250, 255–282
Manly, C. M., assistant in charge of experiments … 123, 129, 218–224, 265, 266, 268, 272, 276,
278
― ― ― engine … 219–225
161, 179, 183, 184, 188, 211, 212, 219, 223, 230, 231, 257, 266–268, 270, 271, 287, 280, 281
― statement of … 124, 280
― letter of instructions from (see appendix).
― study of “John Crow” bird (see appendix).
― aerodrome, War Department report on … 277, 278, 279
“Langley type” of aerodrome … 77, 164, 208, 244, 266, 276, 278–281
― ― ― rudder … 77, 86
Lateral stability … 45–52, 97
Launching, difficulties of … 10, 11, 12, 92, 94, 96, 99
― methods of … 13, 94–97, 110
― of large machine … 265–267, 271–272, 276, 282
Launching-apparatus … 92–122, 134, 149, 156–163, 183, 185, 231, 257, 261, 265–267, 270, 272,
276, 282
― overhead … 5, 92–122, 133–135, 139, 142, 143, 145, 151, 152, 154, 156–163
― underneath … 134, 135, 145–147, 151, 152, 154, 156–163, 183
― weakness of … 265, 276, 282
Launching-car … 158, 159, 183, 184, 255, 258, 262, 266–268, 271, 272, 274, 277
Launching speed (see also velocity) … 135, 161, 162
Law of the cube … 129, 130
Lewis, Captain I. N. … 250
Lift of propellers (see also pendulum tests) … 61, 62, 66, 69, 77, 94, 99, 102, 105, 107, 151, 189,
192
Lilienthal, Otto, on efficiency of curves … 44
Lineal velocity … 1, 43, 110, 166
Liquid air … 154
Longitudinal stability … 45–52
Lubrication … 113, 177, 234, 239, 240
M
McDonald, Mr. … 266, 271, 272
McKinley, President William … 123, 124
Macomb, Major M. M., report of … 276–278
Maltby, Mr., machinist … 93–95, 102, 106
Man-carrying machine … 123, 125, 129, 130, 151, 153, 156–187, 234–250, 255–282
Manly, C. M., assistant in charge of experiments … 123, 129, 218–224, 265, 266, 268, 272, 276,
278
― ― ― engine … 219–225
Page 577
― ― ― formula … 51
― John M., description of flight, by … 260–261
Maxim’s formula for horse-power … 15
Mechanical flight … 2–4
― ― theory of … 1
― ― Dr. Bell on … 4
― ― Mr. Langley on … 3–4
Mica, use of … 63, 72, 115, 257
Models (see also aerodrome model description and trials).
― experiments with … 1, 133–155
― ― ― small … 6–14, 17, 19
― flight of (see trials).
― launching of (see also launching apparatus) … 92–122, 133, 134
― rubber-driven … 5, 8–24, 76
― steam-driven (see also Nos. 4, 5, 6) … 134, 135
― steam, motor, and other … 30–40
Motive power (see also engines, electricity, and fuel) … 8, 11, 21–29, 118
― discussion of … 11
Motors, available (see also engines) … 11, 21–29, 278
― carbonic acid gas … 11, 24, 26, 28, 29, 39, 53, 54
― compressed air … 11, 24, 25, 26, 68, 112, 113
― construction of early types of … 30–40
― electrical … 24, 26, 27, 212, 262, 263
― gas … 26, 28, 37, 131, 137
― gasoline … 24, 37, 65, 125, 131, 179, 210, 218, 219, 224, 277
― gunpowder … 24, 25
― hot-water … 24, 25, 68
― rubber … 5, 8–24, 76
― steam … 24, 25, 30–40
― weight of (see also weight of engines) … 116, 126, 130, 209, 247, 250
Mount Whitney, observations on … 123
N
Nash, Dr. F. S. … 276
National Museum, models in … 282
Needle-valve … 56, 57, 113
Nitric acid, use of … 71
― John M., description of flight, by … 260–261
Maxim’s formula for horse-power … 15
Mechanical flight … 2–4
― ― theory of … 1
― ― Dr. Bell on … 4
― ― Mr. Langley on … 3–4
Mica, use of … 63, 72, 115, 257
Models (see also aerodrome model description and trials).
― experiments with … 1, 133–155
― ― ― small … 6–14, 17, 19
― flight of (see trials).
― launching of (see also launching apparatus) … 92–122, 133, 134
― rubber-driven … 5, 8–24, 76
― steam-driven (see also Nos. 4, 5, 6) … 134, 135
― steam, motor, and other … 30–40
Motive power (see also engines, electricity, and fuel) … 8, 11, 21–29, 118
― discussion of … 11
Motors, available (see also engines) … 11, 21–29, 278
― carbonic acid gas … 11, 24, 26, 28, 29, 39, 53, 54
― compressed air … 11, 24, 25, 26, 68, 112, 113
― construction of early types of … 30–40
― electrical … 24, 26, 27, 212, 262, 263
― gas … 26, 28, 37, 131, 137
― gasoline … 24, 37, 65, 125, 131, 179, 210, 218, 219, 224, 277
― gunpowder … 24, 25
― hot-water … 24, 25, 68
― rubber … 5, 8–24, 76
― steam … 24, 25, 30–40
― weight of (see also weight of engines) … 116, 126, 130, 209, 247, 250
Mount Whitney, observations on … 123
N
Nash, Dr. F. S. … 276
National Museum, models in … 282
Needle-valve … 56, 57, 113
Nitric acid, use of … 71
Page 578
Nomenclature of parts of aerodrome … 14, 15
O
Oiling systems … 113, 177, 234, 239, 240
Open wind, experiments in … 42, 99, 257, 271, 272
Ordinance and Fortification (see Board of).
Oxygen, necessity of … 72
P
Paper covering for rudder … 86, 103
Pénaud, Alphonse, toy aeroplane designed by … 7–9, 21, 22, 40
― tail or rudder … 8, 12, 13, 50, 51, 79, 82, 107, 122, 139–147, 151, 152, 153, 209, 211, 213, 214,
216, 253, 264, 270–272
“Pendulum” test for lift … 60, 61, 66, 94, 131, 135, 211, 212, 214, 232
Percaline for wing covering … 194, 195
Pinion (see gears).
Piston (see engines and cylinders).
Pitch of propellers … 63, 69, 76, 94, 181
Plane (see also wings and surfaces).
― dropper … 150
― surface, angle of inclination of … 6, 8, 41–45, 61, 83, 97, 99, 100
― velocity required to sustain … 1, 43, 110, 166
Pocketing of wings … 84, 86, 100, 195, 203
Potomac River, location of tests on … 93
Power (see also steam, fuel, and electricity).
― development of … 8, 39
― formula for … 62
― generating apparatus … 112, 125
― relation to area and weight … 43
Power-gauge (see dynamometer).
Powell, Major G. H., recorder … 250, 267, 276
Press, attitude of … 127, 268
― report to, Mr. Langley’s … 280
― ― ― Mr. Manly’s … 266–267
Pressure, center of … 7, 10, 11, 13, 15, 45–52, 64, 78, 80, 84, 87, 88, 90, 91, 200, 209, 210
― ― ― rules for locating … 49, 87, 88, 90, 101
― ― ― and center of gravity … 10, 11, 15, 46, 48, 64, 98–101, 103
― steam … 24, 30–40, 53–59, 63–75, 101, 114, 117, 134, 135, 137, 141, 142, 149, 150
O
Oiling systems … 113, 177, 234, 239, 240
Open wind, experiments in … 42, 99, 257, 271, 272
Ordinance and Fortification (see Board of).
Oxygen, necessity of … 72
P
Paper covering for rudder … 86, 103
Pénaud, Alphonse, toy aeroplane designed by … 7–9, 21, 22, 40
― tail or rudder … 8, 12, 13, 50, 51, 79, 82, 107, 122, 139–147, 151, 152, 153, 209, 211, 213, 214,
216, 253, 264, 270–272
“Pendulum” test for lift … 60, 61, 66, 94, 131, 135, 211, 212, 214, 232
Percaline for wing covering … 194, 195
Pinion (see gears).
Piston (see engines and cylinders).
Pitch of propellers … 63, 69, 76, 94, 181
Plane (see also wings and surfaces).
― dropper … 150
― surface, angle of inclination of … 6, 8, 41–45, 61, 83, 97, 99, 100
― velocity required to sustain … 1, 43, 110, 166
Pocketing of wings … 84, 86, 100, 195, 203
Potomac River, location of tests on … 93
Power (see also steam, fuel, and electricity).
― development of … 8, 39
― formula for … 62
― generating apparatus … 112, 125
― relation to area and weight … 43
Power-gauge (see dynamometer).
Powell, Major G. H., recorder … 250, 267, 276
Press, attitude of … 127, 268
― report to, Mr. Langley’s … 280
― ― ― Mr. Manly’s … 266–267
Pressure, center of … 7, 10, 11, 13, 15, 45–52, 64, 78, 80, 84, 87, 88, 90, 91, 200, 209, 210
― ― ― rules for locating … 49, 87, 88, 90, 101
― ― ― and center of gravity … 10, 11, 15, 46, 48, 64, 98–101, 103
― steam … 24, 30–40, 53–59, 63–75, 101, 114, 117, 134, 135, 137, 141, 142, 149, 150
Page 579
Pressure-gauge … 114
Prony-brake … 38, 61, 65, 66, 117, 179, 222, 228, 233, 249
Propellers … 7, 8, 11, 13, 22, 40, 68, 69, 94, 95, 102, 103, 108, 109, 118, 119, 136, 139, 143, 145,
149, 178–184, 258, 261, 262, 268, 272, 277
― construction of … 63, 76, 98, 100, 178–184
― early forms of … 7, 8, 11, 22, 33
― lift of … 61, 62, 66, 69, 77, 94, 102, 105, 107, 131, 148, 151, 189, 192
― pitch of … 63, 69, 76, 118, 181
― position of … 39, 63
― shafts of … 39, 117, 175–177, 242
― slip of … 107, 109
― speed of (see also revolutions per minute) … 61, 91, 94, 99, 107, 114, 134, 264, 272
― tests of (see pendulum, lift, and thrust).
― thrust of … 47, 62, 94, 119, 148, 154, 161, 174
― toy … 7, 8, 9, 21, 22
Pumps … 36, 37, 57, 59, 65, 68, 71, 75, 114, 115, 141, 241
― centrifugal … 241, 248
― circulating … 114, 244
― double-acting … 68, 114
― force … 57
Q
Quantico, Va., flights at … 64, 66, 79, 93, 147, 255, 269
Quarter-size model … 158, 159, 170, 226–233, 243, 255, 257–261, 281
Quill, eagle’s, and spruce rib compared … 200, 201
R
Radiator (see also engine, water-cooled) … 252
Randolph, Gen. W. F. … 276, 277
Record of flights (see also data sheets) … 2, 3, 17, 107, 117, 135–155, 255–282
Reed, R. L., chief carpenter … 93–95, 102, 106, 266, 271, 272, 275
Reel attached to float … 119, 120
Relation of area to weight and power … 43, 44, 64, 81, 89, 90, 99
Reservoir (see air-chamber and tank).
Resistance, air … 6, 8, 9, 142
― of frame and guy-wires … 165–167
Revolutions of engine and propellers per minute (see also speed) … 33, 58, 63, 65, 66, 102, 109,
115, 249, 252
Prony-brake … 38, 61, 65, 66, 117, 179, 222, 228, 233, 249
Propellers … 7, 8, 11, 13, 22, 40, 68, 69, 94, 95, 102, 103, 108, 109, 118, 119, 136, 139, 143, 145,
149, 178–184, 258, 261, 262, 268, 272, 277
― construction of … 63, 76, 98, 100, 178–184
― early forms of … 7, 8, 11, 22, 33
― lift of … 61, 62, 66, 69, 77, 94, 102, 105, 107, 131, 148, 151, 189, 192
― pitch of … 63, 69, 76, 118, 181
― position of … 39, 63
― shafts of … 39, 117, 175–177, 242
― slip of … 107, 109
― speed of (see also revolutions per minute) … 61, 91, 94, 99, 107, 114, 134, 264, 272
― tests of (see pendulum, lift, and thrust).
― thrust of … 47, 62, 94, 119, 148, 154, 161, 174
― toy … 7, 8, 9, 21, 22
Pumps … 36, 37, 57, 59, 65, 68, 71, 75, 114, 115, 141, 241
― centrifugal … 241, 248
― circulating … 114, 244
― double-acting … 68, 114
― force … 57
Q
Quantico, Va., flights at … 64, 66, 79, 93, 147, 255, 269
Quarter-size model … 158, 159, 170, 226–233, 243, 255, 257–261, 281
Quill, eagle’s, and spruce rib compared … 200, 201
R
Radiator (see also engine, water-cooled) … 252
Randolph, Gen. W. F. … 276, 277
Record of flights (see also data sheets) … 2, 3, 17, 107, 117, 135–155, 255–282
Reed, R. L., chief carpenter … 93–95, 102, 106, 266, 271, 272, 275
Reel attached to float … 119, 120
Relation of area to weight and power … 43, 44, 64, 81, 89, 90, 99
Reservoir (see air-chamber and tank).
Resistance, air … 6, 8, 9, 142
― of frame and guy-wires … 165–167
Revolutions of engine and propellers per minute (see also speed) … 33, 58, 63, 65, 66, 102, 109,
115, 249, 252
Page 580
Rib, spruce and eagle’s quill, compared … 200, 201
Ribs, construction of … 37, 80, 81, 86, 89, 188, 194–206, 263, 264
Ridgway, Robert, on American Buzzard … 301
Root-angle of wings … 82, 83, 91, 98, 100, 101, 103
Rotation, angle of … 61
― center of … 62
Rubber as a source of power … 5, 8–24, 44, 76
― elastic limit of … 9, 22
― “fatigue” of … 23
― horse-power produced by … 9, 22, 23
― springs … 2, 185
― insulation … 144, 241
Rubber-driven models … 5, 8–22
Rubber-pull and rubber-twisted models … 16–24
Rudder (see also tail) … 8, 9, 77, 80–91, 122, 136, 207–217, 255, 272, 275
― horizontal … 8
― Pénaud’s … 8, 12, 13, 50, 79, 87, 107, 122, 139–147, 151, 209, 211, 213, 214, 216, 253, 270–
272, 275
― vertical evolution of … 81, 82, 86, 97, 101, 106
Rudder-tail (see tail-rudder).
S
Sanding-tests of wings … 84, 85, 89, 99, 190–204
“Separator,” evolution of, for dry steam … 58, 59, 65, 68, 114, 142
Serpollet-type boilers … 56, 57
Shafts, main, construction of … 117
― propeller … 39, 117, 175–177, 242
Sharp, Archibald, on balancing of engines … 246
Sheathing, aluminum … 69
― mica … 63, 72, 115
Shop tests … 40, 218, 251–254
Silk wing-covering … 54, 63, 81, 86–88, 90, 148, 194, 195, 205
Sliding tail designed … 16, 84
Smillie, Thomas W., photographer … 260, 267, 271, 273
Smithsonian Institution … 1, 6, 17, 18, 31, 42, 124–126, 171, 174, 176, 179, 257, 260, 271, 276,
280–281
Smoke-stack … 60, 67, 74, 78
Ribs, construction of … 37, 80, 81, 86, 89, 188, 194–206, 263, 264
Ridgway, Robert, on American Buzzard … 301
Root-angle of wings … 82, 83, 91, 98, 100, 101, 103
Rotation, angle of … 61
― center of … 62
Rubber as a source of power … 5, 8–24, 44, 76
― elastic limit of … 9, 22
― “fatigue” of … 23
― horse-power produced by … 9, 22, 23
― springs … 2, 185
― insulation … 144, 241
Rubber-driven models … 5, 8–22
Rubber-pull and rubber-twisted models … 16–24
Rudder (see also tail) … 8, 9, 77, 80–91, 122, 136, 207–217, 255, 272, 275
― horizontal … 8
― Pénaud’s … 8, 12, 13, 50, 79, 87, 107, 122, 139–147, 151, 209, 211, 213, 214, 216, 253, 270–
272, 275
― vertical evolution of … 81, 82, 86, 97, 101, 106
Rudder-tail (see tail-rudder).
S
Sanding-tests of wings … 84, 85, 89, 99, 190–204
“Separator,” evolution of, for dry steam … 58, 59, 65, 68, 114, 142
Serpollet-type boilers … 56, 57
Shafts, main, construction of … 117
― propeller … 39, 117, 175–177, 242
Sharp, Archibald, on balancing of engines … 246
Sheathing, aluminum … 69
― mica … 63, 72, 115
Shop tests … 40, 218, 251–254
Silk wing-covering … 54, 63, 81, 86–88, 90, 148, 194, 195, 205
Sliding tail designed … 16, 84
Smillie, Thomas W., photographer … 260, 267, 271, 273
Smithsonian Institution … 1, 6, 17, 18, 31, 42, 124–126, 171, 174, 176, 179, 257, 260, 271, 276,
280–281
Smoke-stack … 60, 67, 74, 78
Page 581
Soaring birds, study of (see also appendix) … 7, 9, 88
Soaring-speed … 32, 41, 69
Sparking devices (see electric batteries and circuits).
Specific gravity … 120
Speed attained (see also velocity) … 31, 32, 41, 55, 61, 91, 99, 107, 114, 134, 161, 264
Speed-counter … 62, 120, 185, 243, 249, 252
Spokes, wire … 243
Spruce guy-sticks and frames … 85–87, 90
― ribs compared with quills … 200, 201
St. Louis Exposition tests … 249
Stability, lateral and longitudinal … 45–52, 77
Starter on launching-car … 94, 95
Starting-crank on launching-car … 243, 244
Steam, dry, production of … 58
Steam-chest … 117
Steam-engine … 24, 30–40, 64, 69, 116, 120
Steam-gauge … 114
― construction of frames and … 53–80
Steam-generating apparatus … 114–116
Steam-motors and other models … 30–40, 134, 135
Steam-pressure … 24, 30–40, 53–59, 63–70, 101, 102, 114, 117, 134, 135, 137, 141, 142, 149, 150
Steel, use of … 69, 112, 116, 119, 121, 172, 174, 234, 277
― tubes, for hull … 39, 69, 75, 112, 118, 120
Steering apparatus (see also equilibrium and control) … 214–216, 265, 266, 272
― ― automatic … 30, 77, 211, 216
Steering wheel … 214, 216, 265, 266, 272
Storage batteries (see batteries, electrical).
Stringfellow engine … 30, 31
Superposed wings … 13, 14, 17, 138, 153, 193, 231
Supporting surfaces … 11, 44, 77, 81, 99, 188–206
Supports for propellers … 112
― ― wings and tails … 36, 69
Surfaces (see also planes and wings).
― covering for … 77, 81, 86, 87, 90, 148, 194, 195
― curved … 44, 46
― plane, observations on velocity of … 1
Soaring-speed … 32, 41, 69
Sparking devices (see electric batteries and circuits).
Specific gravity … 120
Speed attained (see also velocity) … 31, 32, 41, 55, 61, 91, 99, 107, 114, 134, 161, 264
Speed-counter … 62, 120, 185, 243, 249, 252
Spokes, wire … 243
Spruce guy-sticks and frames … 85–87, 90
― ribs compared with quills … 200, 201
St. Louis Exposition tests … 249
Stability, lateral and longitudinal … 45–52, 77
Starter on launching-car … 94, 95
Starting-crank on launching-car … 243, 244
Steam, dry, production of … 58
Steam-chest … 117
Steam-engine … 24, 30–40, 64, 69, 116, 120
Steam-gauge … 114
― construction of frames and … 53–80
Steam-generating apparatus … 114–116
Steam-motors and other models … 30–40, 134, 135
Steam-pressure … 24, 30–40, 53–59, 63–70, 101, 102, 114, 117, 134, 135, 137, 141, 142, 149, 150
Steel, use of … 69, 112, 116, 119, 121, 172, 174, 234, 277
― tubes, for hull … 39, 69, 75, 112, 118, 120
Steering apparatus (see also equilibrium and control) … 214–216, 265, 266, 272
― ― automatic … 30, 77, 211, 216
Steering wheel … 214, 216, 265, 266, 272
Storage batteries (see batteries, electrical).
Stringfellow engine … 30, 31
Superposed wings … 13, 14, 17, 138, 153, 193, 231
Supporting surfaces … 11, 44, 77, 81, 99, 188–206
Supports for propellers … 112
― ― wings and tails … 36, 69
Surfaces (see also planes and wings).
― covering for … 77, 81, 86, 87, 90, 148, 194, 195
― curved … 44, 46
― plane, observations on velocity of … 1
Page 582
― rigid … 6, 46
― supporting … 11 44, 77, 93, 99 188–206
― sustaining … 1, 5, 41–44, 80–91, 99
― ― and guiding … 5, 80–91
Surgeons’ tape, used for mending ribs … 264
Sustaining surface … 1, 5, 41–44, 80–91, 99
― ― de Lucy on … 19
Symbols … 14, 15
Synchronizing mechanism … 108, 121, 136, 137
T
Table, turn … 156, 165, 166
― whirling … 1, 5, 6, 7, 11, 13, 31, 42, 165, 166, 178, 189–194
Tachometer … 62, 120, 185, 243, 249, 252
Tail … 8, 9, 70, 77, 80, 91, 99, 207–217
― adjustment of … 16, 84
― connections of … 84, 213–216
― covering … 86 103
― Pénaud … 12, 13, 50, 79, 107, 122, 139–147, 151–153, 209, 211, 213, 214, 215
― sliding … 16, 84
― use as guiding and sustaining surface … 80
Tail-rudder … 77, 86, 87, 119, 152, 153
― Langley … 77, 86
Tank, air … 64, 68, 69, 112, 114
― fuel … 36, 65–68, 112, 113
― water … 252
Telephoto camera … 260, 261, 273
Tests (see also engine tests, trials, and flights).
― boilers … 70–75, 135
― construction and … 234–250
― cylinder … 55
― engine … 37, 55, 61, 69, 102, 133, 135, 148, 234–250, 251–254, 281
― experimental engine … 1902–1904 … 250
― frame … 79
― power … 61, 62, 69, 102
― resistance … 165–167
― sanding, of wings … 84, 85, 89, 90, 190–204
― supporting … 11 44, 77, 93, 99 188–206
― sustaining … 1, 5, 41–44, 80–91, 99
― ― and guiding … 5, 80–91
Surgeons’ tape, used for mending ribs … 264
Sustaining surface … 1, 5, 41–44, 80–91, 99
― ― de Lucy on … 19
Symbols … 14, 15
Synchronizing mechanism … 108, 121, 136, 137
T
Table, turn … 156, 165, 166
― whirling … 1, 5, 6, 7, 11, 13, 31, 42, 165, 166, 178, 189–194
Tachometer … 62, 120, 185, 243, 249, 252
Tail … 8, 9, 70, 77, 80, 91, 99, 207–217
― adjustment of … 16, 84
― connections of … 84, 213–216
― covering … 86 103
― Pénaud … 12, 13, 50, 79, 107, 122, 139–147, 151–153, 209, 211, 213, 214, 215
― sliding … 16, 84
― use as guiding and sustaining surface … 80
Tail-rudder … 77, 86, 87, 119, 152, 153
― Langley … 77, 86
Tank, air … 64, 68, 69, 112, 114
― fuel … 36, 65–68, 112, 113
― water … 252
Telephoto camera … 260, 261, 273
Tests (see also engine tests, trials, and flights).
― boilers … 70–75, 135
― construction and … 234–250
― cylinder … 55
― engine … 37, 55, 61, 69, 102, 133, 135, 148, 234–250, 251–254, 281
― experimental engine … 1902–1904 … 250
― frame … 79
― power … 61, 62, 69, 102
― resistance … 165–167
― sanding, of wings … 84, 85, 89, 90, 190–204
Page 583
― shop, of large machine … 40, 218, 251–254
― St. Louis Exposition … 249
― whirling-table … 1, 5, 6, 7, 11, 13, 31, 42, 165–166, 178, 189–194
― wing … 84, 85, 89, 99, 190–204
Testing ground (see also Quantico) … 64, 66, 92, 93, 255, 256, 277, 280
Thrust, center of … 62
― propeller … 47, 62, 94, 119, 148, 154, 161, 174
Thrust-recording devices … 229, 230
Thurston, R. H. … 128, 129
Time of flights … 103, 107, 108, 109, 137, 145, 148, 258
Torque … 222, 242
Toy aeroplanes … 7, 9, 21, 22, 40
Transmission (see also shaft and gears) … 117, 175–177, 242
Transverse frame … 77, 165, 174–178
Trials, first … 97
― (1891) … 17
― (1892) … 53, 92
― (1893) … 65, 93–96
― (1894) … 65, 96–100
― (1895) … 101–106
― (1896) … 2, 79, 106–109
― (1897) … 123–125
― (1898) … 61
― (1899) … 79, 135–155
― (1903) … 126, 181, 255–282
Tubes in hull construction … 69, 112, 116, 119, 120, 172, 174, 234, 277
Turn-table … 156, 165, 166
Turnbuckle (see also guying) … 170, 171, 172
V
Valve-chest … 114, 213
Valves … 114, 117, 213
― exhaust … 237
― mechanically operated … 114, 213
― motion … 112, 114, 115, 213
― needle … 56, 57, 113, 212
Vaporization … 37, 67, 148, 149
― St. Louis Exposition … 249
― whirling-table … 1, 5, 6, 7, 11, 13, 31, 42, 165–166, 178, 189–194
― wing … 84, 85, 89, 99, 190–204
Testing ground (see also Quantico) … 64, 66, 92, 93, 255, 256, 277, 280
Thrust, center of … 62
― propeller … 47, 62, 94, 119, 148, 154, 161, 174
Thrust-recording devices … 229, 230
Thurston, R. H. … 128, 129
Time of flights … 103, 107, 108, 109, 137, 145, 148, 258
Torque … 222, 242
Toy aeroplanes … 7, 9, 21, 22, 40
Transmission (see also shaft and gears) … 117, 175–177, 242
Transverse frame … 77, 165, 174–178
Trials, first … 97
― (1891) … 17
― (1892) … 53, 92
― (1893) … 65, 93–96
― (1894) … 65, 96–100
― (1895) … 101–106
― (1896) … 2, 79, 106–109
― (1897) … 123–125
― (1898) … 61
― (1899) … 79, 135–155
― (1903) … 126, 181, 255–282
Tubes in hull construction … 69, 112, 116, 119, 120, 172, 174, 234, 277
Turn-table … 156, 165, 166
Turnbuckle (see also guying) … 170, 171, 172
V
Valve-chest … 114, 213
Valves … 114, 117, 213
― exhaust … 237
― mechanically operated … 114, 213
― motion … 112, 114, 115, 213
― needle … 56, 57, 113, 212
Vaporization … 37, 67, 148, 149
Page 584
Varnish, collodion … 192
― not affected by ammonia … 198
― pyroxelene … 86
― water-proof … 263, 264
Velocity … 18, 31, 32, 55, 91, 99, 107, 109, 114, 134, 150, 161, 166, 185, 264, 265
― initial … 100, 110, 150, 163
― required to sustain plane … 1, 43, 110, 166
Vertical rudder … 81, 82, 86, 97, 101, 106
Vulcanite, use of … 257
W
War Department, allotment … 124–126, 132, 278, 279
― ― Board of Ordnance and Fortification … 124–126
― ― ― ― ― ― ― Report of … 276–280
Washington Evening Star, report of … 274
Watches, stop, for timing flight … 109
Water, cooling, for engine … 235, 236, 241, 247, 248, 252
Water-engine, hot … 24, 25
Water-jacket … 220, 234, 236
Water-proof varnish … 263, 264
Water-tank … 252
Watkins J. E. … 39
Weight (see also data sheets).
― flying, of aerodrome … 15, 38, 62, 63, 76, 77, 81, 89, 90, 91, 101, 109, 116, 148, 206, 247, 250,
256, 277
― of aerodrome … 31, 38, 40, 53, 62, 63, 116, 126, 130, 206, 256
― ― covering for wings … 194
― ― parts of aerodrome … 31, 63, 116, 190, 250
― ― engine … 116, 117, 126, 130, 156, 209, 247, 250, 277
― per horse-power … 31, 126
― relation to area and power … 43, 44, 64, 81, 89, 90, 96
― total, with aviator … 256
Wellner, Georg … 44, 47
Wheel, fly … 242, 243, 247, 252
― steering … 214–216, 265, 266, 272
Whirling-table … 1, 5, 6, 7, 11, 13, 31, 42, 165–166, 178, 189–194
Widewater, Va., experimental grounds (1903) … 255, 256, 277, 280
― not affected by ammonia … 198
― pyroxelene … 86
― water-proof … 263, 264
Velocity … 18, 31, 32, 55, 91, 99, 107, 109, 114, 134, 150, 161, 166, 185, 264, 265
― initial … 100, 110, 150, 163
― required to sustain plane … 1, 43, 110, 166
Vertical rudder … 81, 82, 86, 97, 101, 106
Vulcanite, use of … 257
W
War Department, allotment … 124–126, 132, 278, 279
― ― Board of Ordnance and Fortification … 124–126
― ― ― ― ― ― ― Report of … 276–280
Washington Evening Star, report of … 274
Watches, stop, for timing flight … 109
Water, cooling, for engine … 235, 236, 241, 247, 248, 252
Water-engine, hot … 24, 25
Water-jacket … 220, 234, 236
Water-proof varnish … 263, 264
Water-tank … 252
Watkins J. E. … 39
Weight (see also data sheets).
― flying, of aerodrome … 15, 38, 62, 63, 76, 77, 81, 89, 90, 91, 101, 109, 116, 148, 206, 247, 250,
256, 277
― of aerodrome … 31, 38, 40, 53, 62, 63, 116, 126, 130, 206, 256
― ― covering for wings … 194
― ― parts of aerodrome … 31, 63, 116, 190, 250
― ― engine … 116, 117, 126, 130, 156, 209, 247, 250, 277
― per horse-power … 31, 126
― relation to area and power … 43, 44, 64, 81, 89, 90, 96
― total, with aviator … 256
Wellner, Georg … 44, 47
Wheel, fly … 242, 243, 247, 252
― steering … 214–216, 265, 266, 272
Whirling-table … 1, 5, 6, 7, 11, 13, 31, 42, 165–166, 178, 189–194
Widewater, Va., experimental grounds (1903) … 255, 256, 277, 280
Page 585
Wind, artificial … 42, 61
― difficulties of launching in … 94, 99, 265, 271, 272, 276, 282
― experiments in … 42, 61, 99, 257, 271
― internal work of the … 6, 42
― open … 42, 99, 257, 271, 272
Wind-shield for burners … 60, 67, 95, 115
Wind-vane rudder … 136
Wing-clamps … 82, 89, 145, 183
Wings, adjustment of, for center of gravity … 16
― angle of … 45, 61, 82, 83, 89, 91, 97, 98, 100, 101, 103
― arrangement of … 45–47, 77, 86, 89, 194, 255
― bagging of … 84, 86, 100, 195, 203
― bird, construction of … 7, 188, 200, 201
― boxes for … 263, 264
― construction of … 7, 70, 80, 81, 87, 90, 91, 99, 105, 119, 121, 138, 188–206
― covering of, cloth … 195, 199, 204, 205
― ― ― goldbeater’s skin … 77
― ― ― paper … 86
― ― ― silk … 54, 63, 81, 86–88, 90, 148, 194, 195, 205
― ― ― weight of … 194
― curvature of … 18, 44, 46, 47, 86, 87, 90, 99, 112
― distortion of … 82, 83, 84, 91, 98, 105
― double tier … 13, 14, 17, 138, 193, 231
― efficiency of … 46, 87, 89, 91, 144, 192, 193
― flexure of (see distortion of).
― pocketing of … 84, 86, 100, 195 203
― quills and spruce ribs compared … 200, 201
― ribs of … 37, 80, 81, 86, 89, 188, 194–206
― single tier … 17, 142, 146, 147–151, 153, 192, 193, 231
― superposed … 13, 14, 17, 138, 153, 193, 231
― surface of … 9, 69, 81, 99
― tandem efficiency of … 46, 87
― two sets of … 13, 77, 106, 138, 231
― weight of … 190, 196
Wire guying … 81, 84–91, 99, 164–173, 189, 191, 195, 196, 199, 264, 266
― resistance … 165–167
― difficulties of launching in … 94, 99, 265, 271, 272, 276, 282
― experiments in … 42, 61, 99, 257, 271
― internal work of the … 6, 42
― open … 42, 99, 257, 271, 272
Wind-shield for burners … 60, 67, 95, 115
Wind-vane rudder … 136
Wing-clamps … 82, 89, 145, 183
Wings, adjustment of, for center of gravity … 16
― angle of … 45, 61, 82, 83, 89, 91, 97, 98, 100, 101, 103
― arrangement of … 45–47, 77, 86, 89, 194, 255
― bagging of … 84, 86, 100, 195, 203
― bird, construction of … 7, 188, 200, 201
― boxes for … 263, 264
― construction of … 7, 70, 80, 81, 87, 90, 91, 99, 105, 119, 121, 138, 188–206
― covering of, cloth … 195, 199, 204, 205
― ― ― goldbeater’s skin … 77
― ― ― paper … 86
― ― ― silk … 54, 63, 81, 86–88, 90, 148, 194, 195, 205
― ― ― weight of … 194
― curvature of … 18, 44, 46, 47, 86, 87, 90, 99, 112
― distortion of … 82, 83, 84, 91, 98, 105
― double tier … 13, 14, 17, 138, 193, 231
― efficiency of … 46, 87, 89, 91, 144, 192, 193
― flexure of (see distortion of).
― pocketing of … 84, 86, 100, 195 203
― quills and spruce ribs compared … 200, 201
― ribs of … 37, 80, 81, 86, 89, 188, 194–206
― single tier … 17, 142, 146, 147–151, 153, 192, 193, 231
― superposed … 13, 14, 17, 138, 153, 193, 231
― surface of … 9, 69, 81, 99
― tandem efficiency of … 46, 87
― two sets of … 13, 77, 106, 138, 231
― weight of … 190, 196
Wire guying … 81, 84–91, 99, 164–173, 189, 191, 195, 196, 199, 264, 266
― resistance … 165–167
Page 586
― spokes … 243
Wooden guy sticks … 63, 81, 85
― ribs … 37, 80, 81, 86, 89, 188, 194–206, 263, 264
Wrecking of large machine … 126, 184, 265–281
Z
Zinc, energy developed from … 27, 241
Zoological Park cameras … 260, 261, 273
Wooden guy sticks … 63, 81, 85
― ribs … 37, 80, 81, 86, 89, 188, 194–206, 263, 264
Wrecking of large machine … 126, 184, 265–281
Z
Zinc, energy developed from … 27, 241
Zoological Park cameras … 260, 261, 273
Page 587
◊ CONTENTS
TRANSCRIBER'S NOTE
Original spelling and grammar have been generally retained, with some exceptions noted
below.
Original printed page numbers are shown in the right margin like "p052".
Original small capitals LOOK LIKE THIS.
Footnotes have been renumbered and moved from the ends of pages to the ends of the
appropriate sections, which are: Advertisement (page iii); Part I; and Part II, up to just ahead of
the Data Sheets—which have their own footnotes, which were neither moved nor renumbered.
Illustrations are moved from inside paragraphs to between paragraphs. The symbol "lgr", in a
caption to an illustration, links to a larger image—these are available only in the html edition.
The transcriber created the cover image by editing the title page image, and hereby assigns it to
the public domain.
Pages 16–18. Page 16 ended after "with another one, No. 31, also shown" (i.e. in the middle
of a sentence). This was followed by Plates 1–4, & then by page 17, which contained two data
tables, & then page 18, which continued the original paragraph. The transcriber has closed the
paragraph, and moved the Plates and tables to follow it.
Pages 31–32. The footnote on page 31 said only "See footnote on page 32." The footnote on
page 32 had no anchor in the text. Therefore, to simplify, the page 31 footnote has been
eliminated, and its anchor is linked directly to the page 32 footnote. Pages 46–47. The footnote
on page 47 had no anchor in the text. However, the footnote on page 46 said only "See
Footnote page 47". Therefore, the footnote anchor on page 46 has been linked directly to the
footnote on page 47, eliminating the page 46 footnote.
Page 63. The large table was split into two tables, repeating the first column in each part.
Page 140. The paragraph for June 23 originally ended "dotted line in Plate". The transcriber
has inserted " 34.", as a guess.
Pages 190–192. The wide tables were split into two, repeating the first column in each part.
Page 193. The wide tables were transposed, row for column.
Page 201. The wide table was split into two.
Pages 297–308, Data Sheets. Remarks originally situated in the tables are appended below
each Data Sheet. The units of measurement were originally spelled out—m. = Metres ; ft. =
Feet ; gr. = Grammes ; and lbs. = Pounds. In the footnotes to the Data Sheets, in the phrases
"curved wings 2-5 the way", and "rear wings have 2-3 of the efficiency", the hyphen seems to
mean division, like "/". This usage occurs also in the caption to Plate 85, in "SCALE 1 1-16
INCH TO STATUTE MILE".
Page 299. Item 41, "7 75" changed to "7.75".
INDEX. The original index was structured in a way not suitable for this ebook. The white
space on the printed page substituted for words not repeated. Thus, under "Balancing of
aerodrome, … ", were indented entries for "engine", "wings and rudder", &c. This spacing has
been rendered herein as a horizontal bar "―", one for each word to be understood as repeated.
So in this case, two bars, meaning "Balancing of". Moreover, page numbers referenced by
index entries were right-justified and preceded by dotted leaders. Herein, the leaders have been
suggested by horizontal ellipsis "…".
Estimating from Internet Archive's stated scanning rate of 400 ppi, the pages were about 6.2
by 9.2 inches. Body text was printed in 9 point type, with 3 point leading, and footnotes were
TRANSCRIBER'S NOTE
Original spelling and grammar have been generally retained, with some exceptions noted
below.
Original printed page numbers are shown in the right margin like "p052".
Original small capitals LOOK LIKE THIS.
Footnotes have been renumbered and moved from the ends of pages to the ends of the
appropriate sections, which are: Advertisement (page iii); Part I; and Part II, up to just ahead of
the Data Sheets—which have their own footnotes, which were neither moved nor renumbered.
Illustrations are moved from inside paragraphs to between paragraphs. The symbol "lgr", in a
caption to an illustration, links to a larger image—these are available only in the html edition.
The transcriber created the cover image by editing the title page image, and hereby assigns it to
the public domain.
Pages 16–18. Page 16 ended after "with another one, No. 31, also shown" (i.e. in the middle
of a sentence). This was followed by Plates 1–4, & then by page 17, which contained two data
tables, & then page 18, which continued the original paragraph. The transcriber has closed the
paragraph, and moved the Plates and tables to follow it.
Pages 31–32. The footnote on page 31 said only "See footnote on page 32." The footnote on
page 32 had no anchor in the text. Therefore, to simplify, the page 31 footnote has been
eliminated, and its anchor is linked directly to the page 32 footnote. Pages 46–47. The footnote
on page 47 had no anchor in the text. However, the footnote on page 46 said only "See
Footnote page 47". Therefore, the footnote anchor on page 46 has been linked directly to the
footnote on page 47, eliminating the page 46 footnote.
Page 63. The large table was split into two tables, repeating the first column in each part.
Page 140. The paragraph for June 23 originally ended "dotted line in Plate". The transcriber
has inserted " 34.", as a guess.
Pages 190–192. The wide tables were split into two, repeating the first column in each part.
Page 193. The wide tables were transposed, row for column.
Page 201. The wide table was split into two.
Pages 297–308, Data Sheets. Remarks originally situated in the tables are appended below
each Data Sheet. The units of measurement were originally spelled out—m. = Metres ; ft. =
Feet ; gr. = Grammes ; and lbs. = Pounds. In the footnotes to the Data Sheets, in the phrases
"curved wings 2-5 the way", and "rear wings have 2-3 of the efficiency", the hyphen seems to
mean division, like "/". This usage occurs also in the caption to Plate 85, in "SCALE 1 1-16
INCH TO STATUTE MILE".
Page 299. Item 41, "7 75" changed to "7.75".
INDEX. The original index was structured in a way not suitable for this ebook. The white
space on the printed page substituted for words not repeated. Thus, under "Balancing of
aerodrome, … ", were indented entries for "engine", "wings and rudder", &c. This spacing has
been rendered herein as a horizontal bar "―", one for each word to be understood as repeated.
So in this case, two bars, meaning "Balancing of". Moreover, page numbers referenced by
index entries were right-justified and preceded by dotted leaders. Herein, the leaders have been
suggested by horizontal ellipsis "…".
Estimating from Internet Archive's stated scanning rate of 400 ppi, the pages were about 6.2
by 9.2 inches. Body text was printed in 9 point type, with 3 point leading, and footnotes were
Page 588
printed in 5.4 point type.
Page 589
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