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• # Motor sizing help

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

1. ### Skella83New 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

2.
3. ### s.weinbergWell-Known MemberEngineeringClicks 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. ### Skella83New Member

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Aug 2021
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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.

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