====== Thermobile ======

{{tag> heat_engine thermodynamics shape_memory_effect nitinol unlocated}}

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===== Description =====

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. 

===== Purpose =====

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.

===== Apparatus =====

  * 'Thermobile' Heat engine
  * Cup of hot water (~60ºC)
  * [[equipment:lab_stands:start|Lab stand and clamp]] (Optional)

===== Setup =====

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. 

===== Notes =====

This simple engine works using a more complicated principle: the [[wp>Shape-memory_alloy|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. 

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| **Location** | C3 |
| **Maker** | Unknown |
| **Current State** | Working |
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