CHAPTER IX 



THE QUARTER-SIZE MODEL AERODROME 



Owing to the very considerable changes which constructional reasons neces- 

 sitated in the relative positions of the center of pressure, center of gravity, 

 and line of thrust from those which theoretical considerations pointed to as be- 

 ing 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 aero- 

 drome 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 en- 

 gine developing one and a half horse-power on the Prony brake for five min- 

 utes without diminution in power caused by overheating. While it was desired 

 if possible to get an engine which would come within the given weight and de- 

 velop 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 live minutes. The only engine builder who could be found willing to under- 

 take 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 mak- 

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