3 phase short, any potential issues?

[harrisonh]

I was playing around with a Q75 motor while lacing it up.

I shorted the 3 motor phases (with a razor blade), and then forcefully turned the wheel.
It was cool to feel how much mechanical resistance there was.

However, I then turned the wheel harder/faster, and suddenly felt some "slippping".

Is it possible I damaged something?

My thoughts are:
1) gears slipped because too much torque?
2) too much current causing magnet demagnetization?

I plugged in a battery and controller, and it still "works" though...

 

[amberwolf]

There is usually a roller/ramp clutch inside typical geared hubmotors. This only transfers torque in one direction, so when the wheel is rolled forward, it doesn't spin the motor, only the gearing up to the clutch.

When the wheel is rolled backward, then it engages the clutch and spins hte gearing and the motor. If the motor is locked up (shorted phases), then it can be a fair bit of force multiplied by the gearing, and it could be possible to slip the clutch rollers on the clutch surface. This probably doesn't damage the clutch, but it causes a bit of wear in the slipped areas. If it was repeated enough it could cause enough wear to allow the clutch to slip during motor operation.

FWIW, years ago I broke a clutch in a Fusin geared motor from too sudden an application of motor torque, it actually cracked the clutch core from one of the roller ramps on out to the outside edge. The motor would run, and without a load on the wheel (in the air) it could still spin the wheel, but not as fast as it should, and any load on the wheel would keep it from spinning, though you could hear the motor running fine inside it. :/

 

[harrisonh]

There is usually a roller/ramp clutch inside typical geared hubmotors. This only transfers torque in one direction, so when the wheel is rolled forward, it doesn't spin the motor, only the gearing up to the clutch.

When the wheel is rolled backward, then it engages the clutch and spins hte gearing and the motor. If the motor is locked up (shorted phases), then it can be a fair bit of force multiplied by the gearing, and it could be possible to slip the clutch rollers on the clutch surface. This probably doesn't damage the clutch, but it causes a bit of wear in the slipped areas. If it was repeated enough it could cause enough wear to allow the clutch to slip during motor operation.

FWIW, years ago I broke a clutch in a Fusin geared motor from too sudden an application of motor torque, it actually cracked the clutch core from one of the roller ramps on out to the outside edge. The motor would run, and without a load on the wheel (in the air) it could still spin the wheel, but not as fast as it should, and any load on the wheel would keep it from spinning, though you could hear the motor running fine inside it. :/

That makes a lot of sense. I will see if there are any problems while runnign later.
I can still apply decent amount of force during my 3phase short braking..so I'm hoping it will be okay during normal riding.