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Nitinol Windmill


A chassis connects two wheels of equal size. Around them is a loop of nitinol- a shape memory alloy- that has been 'trained' to straighten when heated up. The top wheel has a propeller attached.


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.


  • Nitinol windmill
  • Cup of nearly boiling water


This works off a temperature gradient across the Nitinol wire, and boiling water (or close to, ~90ºC) is usually good enough for a room temperature environment. Submerge the bottom wheel into the boiling water (just enough to cover the wire) and give the blades a small flick to start it.


The one with tape on its supporting beam doesn't work as well. There is also a cup near the windmills that has tearing to indicate the maximum filling line.

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.

Demo room information

Location —-
Maker Unknown
Current State Working
demonstrations/4_thermodynamics/4f_entropy_and_the_second_law/nitinol_windmill/start.txt · Last modified: 2019/04/17 19:30 by demoroom