CATALOG OF THE aiECHANICAL COLLECTIONS IJQ 



The engine consists of two "equilibrium" cylinders placed in line 

 end to end and a short distance apart. Within each cylinder is a 

 hollow equilibrium piston, both connected by a long piston of rela- 

 tively small diameter, called the working piston, which passes 

 through airtight stuffing boxes in the heads of the equilibrium cyl- 

 inders. The cylinders are connected to a heater and to a water- 

 cooled chamber, through suitable valves and passages, so that both 

 ends of one equilibrium cylinder are simultaneously in communi- 

 cation with the cooler. The pressure being higher in the heater than 

 in the cooler, the eiFect is to force the working piston out of the 

 cylinder in communication with the heater into the other. The 

 equilibrium pistons move with the work piston and circulate the air 

 in the cylinders to the heater or cooler and back to the respective 

 cylinders, maintaining a constant pressure in each cylinder through- 

 out the stroke. When the piston has completed its stroke the valves 

 are reversed and a continuous motion is produced. This engine in- 

 cludes the regenerator or "heat deposit vessel", which was a feature 

 of most of Ericsson's engines. In this construction it is a vessel filled 

 with disks of wire cloth, which are heated by the hot air passing from 

 the cylinders to the cooler and, in turn, give up this heat to the air 

 passing from the cooler to the heater. 



CRANE HOT-AIR ENGINE, 1865 



U.S.N.M. no. 308670; original patent model; transferred from the United States 

 Patent Office ; not illustrated. 



This model was submitted with the application for the Patent no. 

 46084, issued to Moses G. Crane, of Newton, Mass., January 31, 1865. 



This engine consists of one vertical work cylinder and two pump 

 or air-transfer cylinders connected to two furnaces. In operation 

 two separate quantities of air are used repeatedly. One quantity of 

 air is circulated between one furnace and the upper end of the work 

 cylinder by one of the air pumps, while the other charge of air is 

 supplied from the other furnace to the lower end of the work cyl- 

 inder. In each case the air is heated in the furnace, transferred 

 to the work cylinder, allowed to expand doing work against the pis- 

 ton, and is then returned to the furnace by the pump, to be reheated. 

 The pump pistons and valves are actuated by slotted bell cranks 

 on the ends of the engine crankshaft. 



