Rubber Band Engine
To demonstrate the Feynman rubber band engine.
Rubber band engine (rotor in refrigerator), variac and heater.
Rubber bands form the spokes of a well-balanced wheel. When heated, the rubber bands contract, moving the center of mass of the wheel so that it is out of balance, causing the wheel to rotate.
George Calingaert, A Simple Demonstration of the Carnot Cycle, Journal of Chemical Education, August 1952, pp. 405-406.