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Torque estimate ?

  1. Feb 16, 2008 #1
    Guys, I have a solar panel screwed onto a shaft which connects directly to a servo motor shaft. How much should the torque rating of the servo be to be able to rotate it ? I mean an estimate of the minimum torque required. The panel weighs 0.8kg plus a few grams for the solar panel holder (made of perspex). No gears are used.

    Thank you.
  2. jcsd
  3. Feb 16, 2008 #2


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    Science Advisor

    You'll need an estimate of either the radius of gyration or the moment of inertia about the rotating axis. You will also have to either assume or specify a rate of angular acceleration about that axis.
  4. Feb 17, 2008 #3
    I would need the servo shaft to rotate a total of 135 degrees, rotating a few degrees every half an hour for eight hours (It will operate like a stepper, stepping during each hour). The speed of rotation is not important, as long as it rotates. The panel's length is 32cm and height is 18 cm. It is a sun tracker.

    There will also be another servo to rotate the round base.

    Pls see diagram attached below.

    Does this help ?

    Attached Files:

  5. Feb 17, 2008 #4


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    Staff: Mentor

    If the collector is balanced, and with the angular velocity being small, the torque required from the motor is tiny. I'd look into a telescope clock drive (if they still make them). Otherwise, you can get a stepper-motor upgrade kit, but they are more expensive than one that just plugs in and runs at the clock rate.
  6. Feb 17, 2008 #5
    How tiny ? The panel weighs 0.8kg. Is this servo sufficient (3.40 kg-cm torque) ?


    What about the servo at the bottom (there will be some bearings below the base) ? It seems like the top would be a bit heavy. The whole frame will be made of perspex.
    Last edited by a moderator: Apr 23, 2017
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