Animated Engines, Single Cylinder Stirling

Animated Engines, Single Cylinder Stirling: "This type of Stirling engine, known as the beta configuration3, features just one cylinder with a hot end and a cool end. The working gas is transferred from one end of the cylinder to the other by a device called a displacer (here illustrated in blue). The displacer resembles a large piston, except that it has a smaller diameter than the cylinder, thus its motion does not change the volume of gas in the cylinder - it merely transfers the gas around within the cylinder."

Helge: Take a look at the animation on the site.