This Instructable will describe a model Stirling cycle engine I built. More importantly, it will list design criteria, materials of construction, and tips so that you can build one of your own design.
This type engine is called a low temperature difference (LTD) Stirling engine, and there are several ways to build one, some of which are described in other Instructables on this site.
Step 1: What is a Stirling cycle engine?
The Stirling cycle engine was invented by Robert Stirling in 1816, so it has been around for a while. It is a heat engine, and is based upon a cycle of heating, then cooling, of a gas (usually air) contained within the engine. Since a Stirling engine is air tight, during the heating phase the air pressure inside increases, and during the cooling phase the pressure decreases. A displacer connected to the crankshaft moves the internal air from hot side to cold side of a cylinder. The change in pressure drives a power piston, which is also connected to the crankshaft. Since there are two stages, hot and cold, it is a two cycle engine
This diagram shows the concept of a traditional LTD Stirling cycle engine. The components of the engine described in this Instructable are arranged differently, but the concept is the same.