How to calculate the RPMs needed to make a spincast lquid parabolic dish?

  1. Greetings,

    Anyone know how to calculate the revolutions per minute needed to create a liquid parabola of given diameter and depth?

    Thanks
     
  2. jcsd
  3. Andy Resnick

    Andy Resnick 5,815
    Science Advisor
    Education Advisor

    A good accounting can be found here:
    http://en.wikipedia.org/wiki/Liquid_mirror

    AFAIK, the main problem is getting a motor that can run at low constant speed without any high-frequency jitter.
     
  4. If I have done the math correctly, it seems the wider the radius is the fewer RPMs that are needed? Is that correct? That is the opposite for what I was thinking.
     
  5. Andy Resnick

    Andy Resnick 5,815
    Science Advisor
    Education Advisor

    The larger the radius, the slower angular speed needed to generate the same profile... IIRC that's correct. Those large mirrors turn *very* slowly.
     
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