466 POPULAR SCIENCE MONTHLY 



upon the engines began here in August, 1900, in the immediate care 

 of Mr. Manly. These engines were to be of nearly double the power 

 first estimated and of little more weight, but this increased power and 

 the strain caused by it demanded a renewal of the frame as first built, 

 in a stronger and consequently in a heavier form, and the following 

 sixteen months were spent in such a reconstruction simultaneously 

 with the work on the engines. 



The flying weight of the machine complete, with that of the 

 aeronaut, was 830 pounds; its sustaining surface, 1,040 square feet. 

 It, therefore, was provided with slightly greater sustaining surface 

 and materially greater relative horsepower than the model subse- 

 quently described which flew successfully. The brake horsepower of 

 the engine was 52; the engine itself, without cooling water, or fuel, 

 weighed approximately 1 kilogram to the horsepower. The entire 

 power plant, including cooling water, carburetor, battery, etc., weighed 

 materially less than 5 pounds to the horsepower. Engines for both 

 the large machine and the quarter-size model were completed before 

 the close of 1901, and they were immediately put in their respective 

 frames and tests of them and their power-transmission appliances were 

 begun. 



It is well here to call attention to the fact that although an engine 

 may develop sufficent power for the allotted weight, yet it is not at 

 all certain that it will be suitable for use on a machine which is 

 necessarily as light as one for traversing the air, for it would be im- 

 possible to use, for instance, a single cylinder gasoline engine in a 

 flying machine unless it had connected to it prohibitively heavy fly- 

 wheels. These facts being recognized, the engines built in the Smith- 

 sonian shops were provided with five cylinders, and it was found upon 

 test that the turning effect received from them was most uniform, and 

 that, by suitable balancing of rotating and reciprocating parts, they 

 could be made to work so that there was practically no vibration, even 

 when used in the very light frames of the aerodromes. 



The engine is not all the apparatus connected with the development 

 and delivery of power, for obviously there must be shafts, bearings,, 

 and in the present case there were also gars; and all of these parts 

 must necessarily be phenomenally light, while all of the materials must 

 be capable of withstanding repeated and constant strains far beyond 

 their elastic limit. It is also evident to any one having familiarity 

 with such constructions that it is most difficult to keep the various 

 bearings, shafts, gears, etc., in proper alignment without adding ex- 

 cessive weight, and also that when these various parts once get out of 

 alignment when subject to strain, the disasters which are caused 

 render them unfit for further use. 



The engines themselves were successfully completed before the close 



