Is It Okay To Backdrive a LEGO Power Functions Motor?

[ExeSandbox]

I am really curious about this, and I haven't seen a lot written about this either. 

Is it okay to backdrive a LEGO PF Motor? Backdrive as in forcing it to turn with your hands. Will it damage the motor in some way? What about PF Servos too, is it okay to force it to turn with your hands?

Because there are some LEGO Technic Power Functions Remote Control sets that have the wheels sort of "locked up" by the motor, and you can only move it with the battery box/remote control. But if you try and roll the vehicle manually, thus backdriving the motor, will it cause harm to the PF Motor? (or Servo)

Thanks a lot! 

[allanp]

I don't know for sure but to be on the safe side I would limit the speed and torque to what the motor delivers when powered. So if the motor runs at 400 rpm, don't spin it faster than that. You can easily spin it way faster if you push a model along and the drive train is strong. This may lead to the motor generating voltages which the internal components wasn't designed for. And if it delivers a maximum one unit of torque when powered and stalled, don't apply any more torque than that. It's VERY easy to exceed this amount of torque when turning directly by hand. The gears inside have tiny teeth and sit on thin plastic pegs. They are more than strong enough for normal use, but they are still small bits of plastic.

[kungpo]

Noting that the little motor that comes with the solar educational set can be a motor or generator, one would imagine it would be fine - plus wouldn't create more power than it can take? Although @Allanp is right in so far as not stressing the internal components of the motor.

[Berthil]

Also PF motor is a generator. Attach a PF LED to it and drive by hand (not too fast as mentioned earlier) and LED should light up.

[m00se]

I don't know specifically for the PF servo, but normally servo's really don't like that.

[dr_spock]

I think you may be limited to 180 degrees of motion with the servo motor. 

 

[mocbuild101]

Quote

Is It Okay To Backdrive a LEGO Power Functions Motor?

Yes, Lego motors are very well designed, and they will be more than strong enough to handle any reasonable* amount of stress.

*In other words, they'll be fine unless you're purposely trying to break them...

[ExeSandbox]

18 hours ago, allanp said:

I don't know for sure but to be on the safe side I would limit the speed and torque to what the motor delivers when powered. So if the motor runs at 400 rpm, don't spin it faster than that. You can easily spin it way faster if you push a model along and the drive train is strong. This may lead to the motor generating voltages which the internal components wasn't designed for. And if it delivers a maximum one unit of torque when powered and stalled, don't apply any more torque than that. It's VERY easy to exceed this amount of torque when turning directly by hand. The gears inside have tiny teeth and sit on thin plastic pegs. They are more than strong enough for normal use, but they are still small bits of plastic.

Thanks a lot for the information! It's really helpful. 

3 hours ago, mocbuild101 said:

Yes, Lego motors are very well designed, and they will be more than strong enough to handle any reasonable* amount of stress.

*In other words, they'll be fine unless you're purposely trying to break them...

Well, that's good to know. 

[sirslayer]

If any reason to fear is the ribbon cable to the PF motors. I seen them get chewed up by gears or the XL motor hanging off its cable after a crash are scenario to avoid!!