J^gQ BULLETIN 173, U. S. NATIONAL MUSEUM 



RIDER HOT-AIR ENGINE, 1871 



Plate 35, Figuee 2 



U.S.N.M. no. 308714, original patent model ; transferred from the United States 

 Patent Office ; photograph no. 39028. 



This model was submitted with the application for Patenc no. 

 111088, issued to Alexander K. Rider, of New York, N. Y., January 

 17, 1871, reissued August 24, 1880, no 9353. 



This engine consists of a power piston and a transfer pision cu 

 connected with valves and passages that the cold air is received and 

 compressed in the same cylinder in which the hot air performs its 

 work. Its simple construction is an improvement on the John Erics- 

 son hot-air engines of 1855-1858. 



A vertical cylinder contains two independent pistons with suitable 

 valves that permit cold air to be drawn into the cylinder, compressed, 

 circulated between heated furnace walls, expanded under a power 

 piston and then exhausted. The upper piston is equipped with two 

 spring-closed intake valves that open on the upstroke of the piston 

 allowing air to fill the cylinder between the upper and lower pistons. 

 This air is then compressed on the downstroke of the upper piston 

 until the pressure is sufficient to open a valve in a passage leading to 

 a heated space surrounding the furnace. The heated and compressed 

 air then passes into the cylinder below the lower piston where it 

 expands, performing work against the piston. 



OTTO CALORIC ENGINE, 1875 



U.S.N.M. no. 30S684 ; original patent model ; transferred from the United States 

 Patent Office ; not illustrated. 



This wooden model (incomplete) was submitted with the applica- 

 tion for Patent no. 145123, issued to Nicolaus Otto, of Deutz, Ger- 

 many, December 2, 1873. 



In this engine hot gases were admitted to the cylinder above the 

 piston during one-third of the downstroke. The remainder of the 

 stroke dilated the confined gases and rendered a great portion of the 

 heat of the gases latent. The remaining portion of the heat was 

 absorbed by the water-cooled cylinder surfaces and the piston was 

 returned by the pressure of the atmosphere. The piston is so con- 

 nected to the crankshaft that the upward stroke was much slower 

 than the downward stroke to permit the heat that was rendered latent 

 on the downstroke and that was liberated during the upstroke to be 

 absorbed by the cooled surfaces of the cylinder. 



