Simple Heat Engines

Turbine Convection Color Candle

Available here: 
From MOMA: BUY NOW Convection Color Candle 

Turbine Convection Color Candle: a simple heat engine by designer Achille Castiglioni- rotational motion resulting from the convection of hot air due to the candle flame of a tea light. All moving parts of thin stainless steel with semitransparent colored panels. Energy transfer: chemical bonds to heat to kinetic energy of the rising air to rotational kinetic energy of the turbine. 

Curie Point Heat Engine

This DIY project is pretty easy to build. One half of one of these inexpensive magnetic necklace clasps will work well for the heated magnet. 
From Amazon: BUY NOW: magnets for curie point engine

A full engine is available from my friends at Grand Illusions Ltd: 
From GI LTD: BUY NOW: Curie Engine 

Curie Point Heat Engine: when the magnet on the end of the wire heats up to a particular temperature (the Curie point) its magnetic field is temporarily lost until it cools. This engine design uses a second magnet to pull the swinging magnet back into the heat source once the magnetic field is reestablished. Repetition of this process creates mechanical motion as long as the heat source is fueled.