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I've been building a 2WD robot for 3 months now and been switching the motors frequently and been running into the same issue - low torque.

I had these low RPM, high torque motors around and thought: Would having four motors (two high speed and two high torque) fix the issue? The high torque ones would help the robot get rolling and the high RPM will help increase the top speed. Would it work?

JRE
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8TILMATE
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  • Why aren't you considering gearing? You need torque and want high speed, so high power motor with correct gearing would solve it. But that is a mechanical solution to a mechancial problem. – Puffafish Apr 14 '23 at 09:20
  • WIth wound field motors you can use the same motor as either high torque or high speed, by controlling the field current. "Field weakening" is a traditional way to increase motor speed. Not so easy with permanent magnet motors. –  Apr 14 '23 at 13:51

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The high torque motors will help the robot to get rolling.

However, when you try to run the robot fast, they will act like brakes, and will start running in generator mode, back powering your motor controller, that might get damages and/or generating to high voltage destroying the motors.

So as long as you don't exceed the max RPM for the low RPM motors, you will probably be fine. But trying to get to the max RPM of your fast motors will be complicated (if you don't want to risk destroying anything)

Sandro
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  • And what if i simply disconnect them after accelerating and connecting them back when picking up speed? – 8TILMATE Apr 14 '23 at 09:19
  • disconnect them electrically or mechanically or both? Electrically only : you will still generate voltage, but no power : so no risk of overheating the motor, but you might still reach the breakdown voltage of the insulation of the motor windings. I expect it to work fine for rotation a bit faster than max RPM, but I have no idea what the breaking RPM/voltage will be). Mechanical only : it should be safe, but you will waste some power in making the high torque motors turn in the air for nothing. Both : its perfectly fine, but maybe not easy to do in practice – Sandro Apr 14 '23 at 09:26