Simple heat engine

• '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.