Thermal Expansion Materials

[Chantry]

Hi

To start off, im a product designer by trade so im sorry if this question is reminiscent of GCSE physics. My project needs to rotate a large but reletavly free moving shaft (about 2in diameter) with temperature. I would like to achieve around 15degrees of rotation with a heat range of around 200 degrees (60-260C). This is for a third world environment so I cant use exotic materials.

My idea is to wind a strip of material around the shaft and fit it to a stationary block. The heat will cause the material to expand, and will cause the shaft to rotate. The more windings I have around the shaft, the more rotation I can expect to achieve.

Does all of this sound plausible?
Is a material like copper the best for this purpose, or something like aluminium?
How do I work out the expansion of a metal with heat?

Thank you!

James

[MacFromOK]

Are you aware that applications of this type (thermometers, thermostats, etc.) are generally made from bi-metal strips (two metals with different expansion rates) in order to achieve the desired rotational movement?

Not sure how well (or if) a single metal will work for this, as the coil may just expand in diameter.

Perhaps some of the other members will comment.

[ChipUser]

Take a look at the properties of Nitinol wire. It may sound exotic but you won't need much to do what you want. It is also known as Flexinol (I think that's a trade name).

[Chantry]

Both bi-metals and Nitinol are both very helpful leads, thank you.

[tekwiz]

A bimetal strip can be made by simply riveting two strips of different metals together. A little research will show you which of the common metals would be the most suitable.

BTW: A single metal strip won't work, as any motion will be microscopic.