Problem with electric motor with brushes

[mtl_slo 0]

When I try to run it really slowly or when I accelerate slowly the car starts working with strange sound and as if gearing would be worn. So I checked all the gearing and they are perfect, then took out the motor and when I tried to turn it with hand I could feel that it is not turning nicely, but it turns than on some point there is as something is stopping it and so on. When I run it fast there is no problem with it and turns ok.

Does this mean that I have to change brushes or is something else wrong?

[94eg! 834]

When I try to run it really slowly or when I accelerate slowly the car starts working with strange sound and as if gearing would be worn. So I checked all the gearing and they are perfect, then took out the motor and when I tried to turn it with hand I could feel that it is not turning nicely, but it turns than on some point there is as something is stopping it and so on. When I run it fast there is no problem with it and turns ok.

Does this mean that I have to change brushes or is something else wrong?

Electric motors make lots of interesting noises at low voltages/loads. If you have an Electronic speed contol, that is the sound generated by the transitors (called fets) switching the power on & off more slowly which then becomes more audible. At high throttle angles, the sound frequency becomes so high pitched, you cannot hear it (it's masked by gear noise).

As for the difficulty turning the rotor shaft, that is normal. It's called cogging. It's the internal magnetic field pulling against the different segments of the rotor. In fact...a motor with a greater cogging effect will make more power than the same motor with weaker magnets. This is why some pro racers & motor builders used to buy magnet zappers. They then could recharge their magnets every time they rebuilt the motor. Motor magnets will slowly loose their "gauss" with heat cycles & age.

[mtl_slo 0]

Electric motors make lots of interesting noises at low voltages/loads. If you have an Electronic speed contol, that is the sound generated by the transitors (called fets) switching the power on & off more slowly which then becomes more audible. At high throttle angles, the sound frequency becomes so high pitched, you cannot hear it (it's masked by gear noise).

As for the difficulty turning the rotor shaft, that is normal. It's called cogging. It's the internal magnetic field pulling against the different segments of the rotor. In fact...a motor with a greater cogging effect will make more power than the same motor with weaker magnets. This is why some pro racers & motor builders used to buy magnet zappers. They then could recharge their magnets every time they rebuilt the motor. Motor magnets will slowly loose their "gauss" with heat cycles & age.

Interesting information. Though, when the motor was new, it was turning nicely, without ''stopping'' on some point. So shouldn't be this cogging effect present also in new motor?

Do you need some special comm lathe or professional (electricians use them for large motors) comm lathe would be fine?

And which comm lathe would be ok for cutting original Tamiya TT-01 Mabuchi motor, LRP Runner Special 4 and Technigold RX540-VZ? What are approximat costs of these?

Also one other question. When you cut the comm, do you always have to use new brushes?

[sosidge 624]

Interesting information. Though, when the motor was new, it was turning nicely, without ''stopping'' on some point. So shouldn't be this cogging effect present also in new motor?

Do you need some special comm lathe or professional (electricians use them for large motors) comm lathe would be fine?

And which comm lathe would be ok for cutting original Tamiya TT-01 Mabuchi motor, LRP Runner Special 4 and Technigold RX540-VZ? What are approximat costs of these?

Also one other question. When you cut the comm, do you always have to use new brushes?

It sounds more likely that there is some debris in the motor, try and flush it out with motor cleaner or strip the motor down.

Sealed can motors are not designed to have the comm cut (20-odd years ago they did make comm lathes that would work on some sealed motors, not a Mabuchi 540 though). Comm lathes for rebuildable motors are all very similar in design. Normally the brushes will need replacing as well, heavily worn brushes might work but the motor will not be at its best.