The Stirling Engine is an External Combustion Engine (the heat source is outside the engine) and can use any available source of adequate heat or cold. It is a classic illustration of converting heat energy into mechanical work using a thermodynamic cycle similar to the well-known Carnot cycle. In this case, however, the engine needs two pistons, a small power piston and a larger "displacement piston" that also stores heat energy. This Sterling engine operates off a burning alcohol lamp that runs a piston. It is an excellent 'toy' for hobbyists or as a serious demonstration model for work or classrooms. All units are tested before shipping.