NO. 



3 LANGLEY MEMOIR ON MECHANICAL FLIGHT 31 



power 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 30x4.8 

 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.' With a smaller angle even better results 

 could be obtained, but as the difficulties of guidance increase as the angle di- 

 minishes, 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. 



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 " O "—IN POUNDS AND OUNCES. 



Estimated Actual 



lbs. oz. lbs. oz. 



Engines 4 4 1 



Boilers and Burners 8 1\ 13 14 



Pumps and Attachments 1 10 



Steering Apparatus 6 



Frame of Hull and Braces, including bowsprit and tail tube.. 7 7 S 11 



Oil tank covering and pipes 13 



Shafts, ball bearings (2:1) and wooden propellers (1:7).... 1 14 3 8 



Wings (5:4) and guys (0:9) 4 5 13 



Tail 1 5 2 2 



Jacket at prow 4 



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 con- 

 struction was a feature which could never be wholly eliminated.) 



1 See footnote on page 32. 



