Stirling Engine
  The Stirling Hot Air Engine has always seemed to be on the verge of becoming commercially successful, starting with its invention by the Scottish clergyman Robert Stirling in 1819. This example, probably from the early part of the 20th century, is at Kenyon College.

   The engine has two cylinders, a large one in the front and a smaller one at the rear. A light, loosely fitting piston made of low thermal conductivity material is contained in the larger cylinder, which is connected to the smaller cylinder at their lower ends. The bottom of the large cylinder is heated and the top is cooled. The top of the smaller cylinder is open to the atmosphere. 

   At the start of the cycle, the small piston is down and the large piston is up. The air in the large cylinder is heated and expands, and drives the small piston up. The crank on the flywheel pushes the large piston down and part of the air rushes around this loosely-fitting piston, where it is cooled and pulls the piston up. Flywheel action then sends the small piston to the bottom of its travel and the cycle begins again.
 

   One of the early Sterling engines is shown at the left. It was photographed in 1978 at the museum at the Department of Natural Philosophy at Glasgow University. 

   The connection between the two cylinders is the horizontal pipe just visible below the bottom of the flywheel.
 
 

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   The Stirling Engine at the left is in the Jack Judson Collection at the Magic Lantern Collection in San Antonio, Texas.

The fan below uses a Stirling Engine to drive the blades. It is marked "The Lake Breeze Motor. Eight patents issued and pending in the United States and in foreign countries. Made for the Texas Hotel Supply Company of Houston, Texas". It used an alcohol burner built into the base and is ca. 1910. The mechanism used to convert the reciprocating motion of the engine to the rotary motion of the fan can be seen in the right-hand picture. The device is in the Jack Judson Collection at the Magic Lantern Collection in San Antonio, Texas.

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