50 BULLETIN 173, U. S. NATIONAL MUSEUM 



HIRAM MAXIM PUMPING ENGINE, 1874 



U.S.N.M. no. 308683; original patent model; transferred from the United States 

 Patent OflSce; not illustrated. 



This model was submitted with the application for the patent 

 issued to Hiram S. Maxim, of New York, N. Y., December 22, 1874, 

 no. 158105. 



This model represents a steam engine, pump, and gas-fired boiler, 

 equipped with automatic valves for maintaining the proper level of 

 water in the boiler and for holding a steady pressure in the boiler by 

 starting or stopping the burner. The combination is a steam-pump- 

 ing unit intended to function automatically without the services of an 

 attendant. 



The engine is supported upon the boiler and consists of a rectangu- 

 lar bed, which serves as the pump suction chamber, upon which is the 

 vertical pump cylinder and the pedestal that supports the flywheel and 

 crankshaft journals and the oscillating steam cylinder. Within the 

 base of the pedestal is a feed-water heater through which the exhaust 

 from the engine passes. A float-operated, weighted, pin valve admits 

 water to the boiler from the discharge pipe of the pump when the level 

 in the boiler falls. The boiler is a cylindrical shell type with com- 

 bustion chamber formed by water legs in the shape of a truncated 

 cone. A ring burner for gas or kerosene is located in a cylindrical 

 firepot within the combustion chamber. The fuel valve to the burner 

 is held open by a spring and is closed by the pressure within the 

 boiler exerted upon a diaphragm and lever. A hole through the valve 

 permits a small pilot flame to burn at all times. 



THOMPSON AND HUNT STEAM ENGINE, c. 1875 

 Plate 13, Fiquke 2 

 U.S.N.M. no. 309e45; model; gift of N. C. Hunt; photograph no. 19922. 



This is a model of the widely used and very successful "Buckeye" 

 engine developed by J. W. Thompson and Nathan Hunt about 1875. 

 It was one of the first of the high-speed, variable cut-oJff ("auto- 

 matic") engines of the modern type. 



The engine is a horizontal, overhung crank engine with cross-head 

 guides cast within a skeleton cylindrical projection of the cylinder. 

 The valve is a hollow-piston slide valve, taking steam at the center 

 and passing it through the hollow center of the valve to ports through 

 the walls of the valve. A sleevelike cut-off valve operates within the 

 main valve to close the ports. The main valve is operated by a fixed 

 eccentric on the crankshaft and the cut-off valve by a shifting eccen- 

 tric, the position of which is varied by a centrifugal governor of the 

 Thompson and Hunt type (see below). 



