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Potential Energy Stored in latex rubber

  1. Dec 8, 2015 #1
    I am looking for a simple number which is the potential energy that can be stored in rubber. ( Joules per gram or something similar ) I know there are a number of forms of rubber and I keep reading numerous articles on how to calculate the energy content of a rubber band.
    Can anyone just tell me the number for typical rubber available commercially ??
    I am building a rubber band "vehicle" and I am starting off with a test bed of one band approx 3m long made up of say 50 strands which will run as a model airplane would but driving the rear wheel. I can pretty much work out frictional losses through the drive system and what horsepower I need to get up to certain speeds but before I run the test vehicle on the road I would be interested to compare the theoretical number against that actually achieved.
    There must also be a optimum diameter for the band itself expressed as a ratio to the length which I am trying to find out from the modelling world but if anyone has that number I would be grateful to hear it.

    Thanks
    Simon
     
  2. jcsd
  3. Dec 9, 2015 #2
    You can just measure it.
    If you know the force F (weight), and the change in length x, you can compute the Hooke's constant k.
    F = -kx

    From there you can compute energy: E = 0.5*kx^2

    Energy per mass is just E/m. If you want a maximum, hang more and more weight from a rubber band, until it breaks.
    Hope this helps.
     
  4. Dec 9, 2015 #3
    Rubber typically doesn't follow Hooke's law. The observed rheological behavior of rubber is highly non-linear. You need to read some papers on the theory of rubber elasticity. Google Mooney-Rivlin equation.

    Chet
     
  5. Dec 10, 2015 #4
    It might not be linear, but you might be able to approximate. Plot weight vs stretch distance.
     
  6. Dec 20, 2015 #5

    CWatters

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    Don't use rubber bands. Google FAI competition rubber as used for model aircraft. Ditto lubricant. As i recall rubber improves as it is "run in".
     
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