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  • Motor sizing help

    Discussion in 'The main mechanical design forum' started by Skella83, Aug 7, 2021.

    1. Skella83

      Skella83 New Member

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      I have a human gyroscope ride like the pic attached and would like to power it with a motor.

      At the moment it's a manual machine and you turn the wheel to rotate the ride. I haven't measured the force required to turn the wheel yet but I'm guestimating it's approx 20kg. The radius of the wheel is approx 20cm and I would like it to rotate at 60rpm.

      How do I go about sizing the motor and ensuring the motor has enough torque? Once I know how to calculate it I can take proper measurements of the forces needed to rotate the wheel.

      Any help appreciated

      [​IMG]
       
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    3. s.weinberg

      s.weinberg Well-Known Member EngineeringClicks Expert

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      20 kg at 20cm (assuming you're pulling one side of the wheel only) is a bit under 40 N-m, or roughly 30 lb-ft. That's the estimated torque you need to generate at 60 RPM.

      With a gearbox, you can trade off speed for torque, or vice versa, but you'll lose a bit. The type of gears in your gearbox will be the major determining factor as to the efficiency.
       
    4. Skella83

      Skella83 New Member

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      That's also what I worked it out to be. My next problem is I want to attach the motor directly to the shaft. Ie direct drive. How do I work out the force required? I coukd physically measure the force required using a pull scale when doing it from 20cm from center of shaft. I.e if I were to be using a pulley. But I can't physically measure the force directly from the spindle using a pull scale. I know the weight of the part of machin weighs approx 250kg. Plus say a max of 100kg for a rider.
       
    5. s.weinberg

      s.weinberg Well-Known Member EngineeringClicks Expert

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      I'm not sure I understand - A 40 N-m motor at 60 RPM coupled directly to the shaft would be equivalent to turning a 20cm radius wheel with 20kg of force at 60 RPM. I'm not sure what you're trying to calculate
       

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