Thermal Engine

The stiring engine was invented by Rev Robert Stirling in 1816.
The engine works on a very basic principal.
When air or gas is heated it expands, conversly when cooled it contracts.
This pressure differential can drive a power piston to extract the work.
The trick is how do you heat and cool air very quickly?
By using a large piston to shuttle the air between the hot and cold plates fast heating and cooling cycles are possible. Heat is transferred form the hot plate to the cold plate. The pressure differential disapates as the two plates equalise in tempreture.
As long as the tempreture difference is maintained then the engine will run.
This engine has two pistons, a smaller drive piston to extract power and a larger piston to displace the air between the hot and cold regions. Connected by push rods and linkages to a crankshaft the pistons are ninety degrees out of phase.
This engine can run on a very small tempreture difference, the power produced however is small.