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I'm trying to figure out what would happen if a really high speed motor - which has enough power to drive a car, but very high RPM & very low torque - tries to move a car. Does it get stuck because of static friction?

Conversely, can anything "bad" (not normal car control/operation) happen if the torque is too high? E.g. wheel slipping?

Whatever the answers, I'd love a short explanation providing some insight. For reference this question came about because I am designing a mobile robot platform with DC motors.

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High RPM/low torque is what gearboxes were invented for. You reduce the speed and increse the torque. Yes, if the peak torque of the motor is too low, the car won't move. A nice quick tutorial on DC motors is here, showing the peak torque is at 0 RPM, but that may still not be enough. It sounds like you are thinking that torque is a constant, but that is not true. Yes, if the torque is too high, the wheels might spin, or the axle might break.

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  • $\begingroup$ Is there any way to quantify torque being "too high"? I know that I can approximately figure out static friction using various material properties, the weight of my car, etc. But how about too much torque? $\endgroup$
    – JDS
    Commented Feb 18, 2015 at 17:13
  • $\begingroup$ Torque being too high is shown by excessive acceleration (maybe you bump into things before you can steer) or by wheels slipping. It sounds like you are thinking the motor has a fixed torque output, but for a robot (or a car) you usually have some control over it like a throttle. If the gear ratio is low enough that you can make so much torque that the wheels spin, you just don't use so much throttle. Also if the gear ratio is that low you will hit max speed (where there is no torque) very quickly. $\endgroup$ Commented Feb 18, 2015 at 17:46

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