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Torque or rpm

  1. Oct 29, 2012 #1
    hi .. ...
    i am entering a sumobot competition..weight limitation 1kg..dimensions 150mm*150mm...what is more important
    torque or rpm...say i have 10 rpm motors with 38kg torque ...and ..60 rpm motors with 20 kg torque...which should i go for...due to the size limitation ..i can go only for 2 motors...any comment is appreciated... Wink
  2. jcsd
  3. Oct 29, 2012 #2
    Every single things are not perfect. They will come with pros and cons. With this kind of competition, I would go for TORQUE.

    Put it this way, just imagine a big truck can carry a load that heavier than its weight. Even it move at low rpm but still can pull its load with high torque.

    In your case, you are about to build a sumo robot, I suggest you go for a motor that has a higher torque than rpm itself.

    Just my humble opinions.
  4. Oct 29, 2012 #3
    thanks a lot...
  5. Oct 29, 2012 #4


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    Science Advisor

    If you gear down the 60 rpm motor to 10rpm, it will give you 6 times the torque it had at 60 rpm. What matters is power = torque x angular velocity. In your example the 60 rpm motor has much more power, so it can potentially create more torque at the same angular velocity.
  6. Oct 29, 2012 #5


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    Homework Helper

    Assuming you can gear the motors, then you're looking for power that is geared down so that the geared down and multiplied torque is at a maximum. See if you can get the specific motor performance curves for the two motors you're considering.

    Note that electrical motors usually produce peak power at 1/2 the maximum no load rpm, but will generate more torque at lower rpms than higher rpms. Link to article that explains this:


    You'll need to decide on a trade off of speed versus the torque after gearing reduction of your bot when choosing the motor and the gearing.
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