156 BULLETIN 173, U. S. NATIONAL MUSEUM 



nected to craiil^s on the same shaft. An automatic intake valve in 

 the right hand or pump cylinder, a lift valve, operated by push rod 

 and cam, between the cylinders, and a similar exhaust valve in the 

 working cylinder are shown. In operation, the combustible mixture 

 is drawn into the pump cylinder by the back stroke of the pump 

 piston. The mixture is compressed during the forward stroke, near 

 the end of which the valve between the two cylinders opens and the 

 compressed mixture enters the work cylinder, where it is immediately 

 ignited and performs work during the outstrike of the piston. The 

 exhaust valve of the work cylinder is open during the return stroke 

 of the work piston, and the spent gases are expelled. Both pistons 

 make their strokes together, i. e., there is no angular distance between 

 the cranks. 



OTTO GAS ENGINE, 1882 



Plate 32, Figutje 2 



U.S.N.M. no. 309556 ; original ; purchased from the Otto Engine Works ; photo- 

 graph no. 10498A. 



This engine, serial no. 554, was built by Schleicher, Schum & Co., 

 of Philadelphia, in 1882. It was used at Princeton University in 

 the mechanical laboratories to 1928, when it was procured for the 

 Museum by the Otto Engine Works. 



This is a 4-horsepower, flame-ignition, 4-stroke cycle, horizontal 

 gas engine, the same as the first of the type introduced into the United 

 States in 1878. In appearance it resembles a horizontal steam en- 

 gine, with cross head, connecting rod, crankshaft, and flywheel. It 

 is, however, single acting. A lay shaft driven by bevel gearing from 

 the crankshaft extends the whole length of the engine and performs 

 many duties. A small belt from the lay shaft operates the lubri- 

 cators, bevel gears drive the ball governor, cams on the lay shaft 

 through a crank and lever operate the exhaust valve on the opposite 

 side of the cylinder, and the shaft ends in a crank that operates the 

 slide valve across the end of the cylinder. The slide valve acts as 

 gas and air intake and ignition valve. The intake picks up a charge 

 of gas, exposes it momentarily to a flame that burns continuously 

 outside the engine, and carries the little quantity of burning gas to 

 a passage in the head of the engine to ignite the compressed explosive, 

 mixture in the cylinder. 



In the operation of the engine, air and gas are drawn into the 

 cylinder through the slide valve by the backstroke of the piston, the 

 valve closes, and the mixture is compressed on the forward stroke; 

 near the end of the stroke the compressed mixture is ignited, and 

 the combustion drives the piston back; on the next forward stroke 

 the exhaust valve opens, and the gases of combustion are expelled ; the 

 exhaust valve closes just before the end of the stroke, and the cycle is 

 repeated. 



