

224 SMITHSONIAN' CONTRIBUTIONS TO KNOWLEDGE VOL. 27 



It will Ito 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 thai a duplicate was to be 

 supplied, if desired, immediately upon the completion and 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 ex- 

 ceed 040 pounds in weight, with a supporting surface of 900 square feet. But 

 it was found thai 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 pro- 

 vide 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 

 \ lower 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 he 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 un- 

 suitable, 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 irregular- 

 ity of action of the engine which at times injured not only the transmission 

 shafts, gears, and frame, hut the engine itself by the serious pounding which 

 occurred. A form was next tried in which t lie 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 mate- 

 rial, which was saturated with gasoline and the surplus drawn off before start- 

 ing the engine. Some of these tanks were provided with a jacket through which 



