DD hub motor growls at lower speeds

[Blueshift]

I notice when i am not at full throttle the motor kinda has a more growling noise. I can also feel a bit of a growling vibration at lower throttle. It is a tiny sequence of quick little chug chug chugs. Is this normal and should i worry? Another way of putting it is it makes a suddle grinding sound and feeling at low throttle. (for lack of a better word) The little chugs are pretty even but once in a while I notice one that's a tad stronger. Any advice is always appreciated.

Motor= 500w amped-bikes

[nebriancent]

have found one of 3 things can cause this
1 over driving the motor current / voltage can make it cog/growl a bit more
2 high and or infinite resistance to and or from hall sensor(s) (is it more pronounced when its wet outside? clean connectors.. check for recessed pins in connectors)
3 bad crimp or recessed pin on phase wires (again check connectors)

[neptronix]

9C/MXUS motors ( like the ampedbikes DD ) are pretty grunty at low RPM, sound like tiny little gas engines, really.
Then there's the resonance at around um.. 20mph?

Maybe you ought to record the sound..

[amberwolf]

Often my 9C on CrazyBike2 makes growling noises at various speeds. 15MPH and 20MPH primarily, but at other speeds too depending on load. At startup from a stop it can be particularly nasty sounding, and sometimes during regen braking it will do it if the battery pack is fairly discharged.

If there is little or no load, like I am cruising rather than accelrating, there is no real noise from the motor.

[dogman]

If it's not running funny at all speeds, it's normal. At slow speeds under heavy load, you actually hear the vibration casued as the current shifts the pull from one magnet to the other. It gets louder the more load the motor is pulling. It gets louder if you pump up the wattage too.

I think of it as the sound of making heat in a motor. So to the extent you can, you can ride more efficient if you ride so you hear that noise less.

[Ykick]

Based on recent experience, the usual 9C growl diminished significantly after I re-laced my motor into a eyelet rim using 13/14ga butted stainless spokes. It's still there but much less than with the cheap Chinese rim and poor quality 13ga spokes.