Stored in a small box with the branding 'Thermobile' on it. A plastic chassis connects two wheels, one bigger one made of plastic and a smaller one made of brass. Around them is a loop of nitinol- a shape memory alloy- that has been 'trained' to straighten when heated up.

Illustrate another example of the huge variety of heat engines. Demonstrate the action of a much simpler heat engine, and show what unites all heat engines: a heat differential.

• 'Thermobile' Heat engine
• Cup of hot water (~60ºC)
• Lab stand and clamp (Optional)

Dip the bottom edge of the brass wheel into the cup of hot water (this demo requires an approximate 35ºC temperature difference across the wheels to run), give the wheel a spin, and it should continue on it's own.

It may be helpful to mount the thermobile on a lab stand so that the demo may be more easily shown.

This simple engine works using a more complicated principle: the shape memory effect. When the wire is bent around a wheel and heated, it will exert a force attempting to straighten itself out. Once the wheel is given a spin, a temperature asymmetry will cause more force to be exerted on one side of the thermobile, so it continues to spin.