44 BULLETIN 173, U. S. NATIONAL MUSEUM 



The engine represented is one in which the crankshaft is located 

 close to the top of the vertical cylinder and is driven by a return con- 

 necting rod from the cross head, which is above the shaft. It is 

 designed to utilize all the limited height available within a boat below 

 the paddle shaft. 



Peculiarities of the engine are the use of two piston rods, one on 

 either side of the crank throw, and the location of the cylinder so 

 that its axis does not pass through the center of the crankshaft. The 

 piston rods terminate in a cross head that works in vertical cylin- 

 drical guides from which a connecting rod returns to the crank lo- 

 cated just above the cylinder. 



The patent also describes the Maudslay and Field "Siamese" en- 

 gine, a double, return-connecting rod engine; and a method of con- 

 trolling the expansion valves of the two cylinders simultaneously and 

 without stopping the engine. This last was effected by changing the 

 position of a pair of spiral cams (snail cams), which operated the 

 expansion valves. 



U.S.N.M. no. 309353, original patent model, transferred from the 

 United States Patent Office, is a duplicate model of this engine. 



LOPER STEAM ENGINE, 1845 



U.S.N.M. no. 251297; original patent model; transferred from the United States 

 Patent OflBce; not illustrated. 



This operating model was submitted with the application for the 

 patent issued to R. F. Loper, of Philadelphia, Pa., November 26, 

 1845, Patent no. 4289. 



The engine was designed to drive two parallel crankshafts in op- 

 posite directions at the same speed, for the purpose of turning screw 

 propellers of the "inventor's and others' design", for the propulsion 

 of ships. 



The single horizontal cylinder of the engine is located a short dis- 

 tance from one end of a long rectangular bed frame. At each end of 

 the frame is a crankshaft connected by its connecting rod to the 

 cross head, which moves in guides near the middle of the frame. A 

 third vibrating rod pivoted on the cross-head pin at the side of the 

 cross head extends the entire length of the engine and connects the two 

 crankshafts for the purpose of keeping them in their proper relative 

 and opposed positions. 



BENSON STEAM ENGINE, 1847 



U.S.N.M. no. 309197; original patent model; transferred from the United States 

 Patent Office ; not illustrated. 



This model was part of the application for the patent issued to 

 Benjamin S. Benson, July 10, 1847, no. 5185. 



