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Micro metal gear motor does not rotate freely when not powered

Hi, I’ve bought the pololu 6V High-Power (HP) Micro Metal Gearmotors with a gear ratio of 1000:0. I’ve noticed that I can’t turn the shaft of the motor with my hands or even pliers when the motor is not powered. I’m thinking this might be because of the friction in the gears but I’m not sure. Could someone tell me why the i cannot rotate the shaft even when theres no power being sent to the motor?

Hello.

We would not expect you to be able to turn the output shaft of one of our 1000:1 Micro Metal Gearmotors manually, and in general I would not recommend attempting to do so since the stress could damage the gears.

The static friction of the gears is a factor with this, but the mechanical resistance of an unpowered motor is primarily caused by its cogging torque. Cogging torque depends on the strength of the motor’s permanent magnets and is amplified by the gear ratio, so even though a tiny motor like this does not have that much cogging toque by itself, when you try to manually turn the output shaft on your motor it is multiplied by 1000.

- Patrick

Okay thanks!! I have another question, do you know what the typical value (or range of value) for this cogging torque is?

Thanks

We have not characterized the cogging torque for our gearmotors.

- Patrick