Need help with material expansion question

[Tawaffles]

Hi

To start off, I am a product designer by trade so I am 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 can't 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

 

[Achy47]

Hi James,

Thank you for your question. Your idea of using thermal expansion to rotate a shaft is definitely plausible and has been used in various applications before. The key to making this work is choosing the right material and understanding its thermal expansion properties.

In your case, copper or aluminum would both be good options as they have high thermal conductivity and relatively large coefficients of thermal expansion. This means that they will expand significantly with changes in temperature, allowing for a greater degree of rotation. However, aluminum may be a better choice for a third world environment as it is more readily available and less expensive than copper.

To calculate the expansion of a metal with heat, you can use the following formula: ΔL = αLΔT, where ΔL is the change in length, α is the coefficient of thermal expansion, L is the original length, and ΔT is the change in temperature. It is important to note that the coefficient of thermal expansion can vary for different types of copper or aluminum, so it is best to consult a material properties database for the specific type you plan to use.

Another factor to consider is the design of the strip of material and how it will be wound around the shaft. You will need to ensure that the material is securely attached to the stationary block and that the winding is tight enough to provide sufficient torque to rotate the shaft. You may also want to consider using multiple strips of material for added strength and stability.

Overall, your idea is definitely feasible and with careful consideration of material properties and design, you should be able to achieve the desired rotation with temperature. Good luck with your project!