114 SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE VOL. 1/ 



This constitutes the heat-generating portion of the machine, and with it it 

 is prohable thai 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 L90mm. 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 en- 

 ters 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 t he other side of the 

 midrod there is a small steam dome 4:2 mm. in diameter with a semi-spherical 

 top rising to a height of 70mm. above the top of the sphere. From this dome 

 two steam pipes are led off, one to the engine and the other to (he 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, hut 

 only after numerous devices involving less weight had failed, a pump driven 

 from the engine shaft was designed and used. In the early experiments vari- 

 ous types of pumps were tried in which the valves were opened and closed au- 

 tomatically by the pressure of the water. It was found, however, thai with the 

 mixture of steam and water to be handled, the valves could not he depended 

 upon to open and close properly at the high speeds at which it was necessary to 

 run the engine. In Aerodrome No. 5, therefore, a double-acting pump witli 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 23mm. with a 

 piston stroke of 20mm. 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 IS 

 mm. in diameter and also lined with a cast-iron bushing 1.25 mm. thick. The 

 aluminum bronze shells of both cylinders are 0.75mm. in thickness. The valve 

 i< a simple piston valve 35mm. 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 p pe 1 cm. outside diameter. The ports 



