my 9c motor started to make noise

arar1971 · Apr 22, 2014

hello,
I have a 9c 7x9 front wheel motor and I build a 14s (52v nominal) 10ah lipo pack.last couple rides, my 9c motor started to make noise like brrrr or grrrr and sometimes and when on hard load or on start up at a steep hill, a metallic ( like a pan scratching noise). also When I am carrying the bike (pushing with human power) to my apartment or parking, I hear a noise like a rubber friction. what it can be?
speed, acceleration,disc callipers everything is Ok.

dogman dan · Apr 22, 2014

Two possibilities are most common, and I suspect you might have both.

Under a heavy load, a 9c motor may growl. Some growl more than others, as the actual wires inside the winding vibrate a little. A tighter wound one will growl less, sometimes a 9c motor will growl a lot under load. The covers make a great bell, that amplifies it. That's pretty much normal, and you can ignore it. If you want to ride more economical, work the throttle to hear less noise. I tended to use growling as a signal to pedal hard for a few feet when dirt riding. They growl louder the more watts you give them. At 3000w, they can growl real loud.

When you push the bike, it makes noise then? If so then...

The scraping noise sounds more like it might be the freewheel. It varies from motor to motor, whether you really need a spacer under the freewheel. Sometimes when you first ride it, the freewheel screws just a hair tighter on the threads, and then the freewheel can contact the cover, and either make a scrape noise, or even lock up against the cover.

Lastly, it's possible some insulating paper in the motor is not installed tight, and it could be scraping the motor cover from the inside. This one is very unlikely, but still possible.

If the bike resists but is noiseless when you push it, then it's likely you are just feeling the magnetic resistance normal for a direct drive motor.

arar1971 · Apr 22, 2014

dogman said:
Two possibilities are most common, and I suspect you might have both.

Under a heavy load, a 9c motor may growl. Some growl more than others, as the actual wires inside the winding vibrate a little. A tighter wound one will growl less, sometimes a 9c motor will growl a lot under load. The covers make a great bell, that amplifies it. That's pretty much normal, and you can ignore it. If you want to ride more economical, work the throttle to hear less noise. I tended to use growling as a signal to pedal hard for a few feet when dirt riding. They growl louder the more watts you give them. At 3000w, they can growl real loud.

When you push the bike, it makes noise then? If so then...

The scraping noise sounds more like it might be the freewheel. It varies from motor to motor, whether you really need a spacer under the freewheel. Sometimes when you first ride it, the freewheel screws just a hair tighter on the threads, and then the freewheel can contact the cover, and either make a scrape noise, or even lock up against the cover.

Lastly, it's possible some insulating paper in the motor is not installed tight, and it could be scraping the motor cover from the inside. This one is very unlikely, but still possible.

If the bike resists but is noiseless when you push it, then it's likely you are just feeling the magnetic resistance normal for a direct drive motor.

Thanks Dogman. You are always my candle in the darkness. thanks for your helps.
then do you recommend me to open the hub and check it?

dogman dan · Apr 22, 2014

Only if

It makes the scraping noise when just pushing the bike, AND, you don't have a rubbing freewheel.

If you don't have the freewheel spacer, then it could still be the cover rubbing on a dropout, or even the derailleur. Eliminate all that, then open up if you must.

Something rubbing inside is pretty rare. But it could be a loose zip tie, some insulating paper normally held down by the zip tie, or even a wonky stator that rubs the magnets.

Personally, I'd ignore it if it's inside the motor. None of it affects function much.

It could also be your bearings. I've not had much trouble with them, but a bad bearing can allow the stator to move enough to scrape.

Lift the tire off the ground, and try to wiggle it. If it moves a lot, then it's the bearings.

arar1971 · Apr 22, 2014

dogman said:
Only if

It makes the scraping noise when just pushing the bike, AND, you don't have a rubbing freewheel.

If you don't have the freewheel spacer, then it could still be the cover rubbing on a dropout, or even the derailleur. Eliminate all that, then open up if you must.

Something rubbing inside is pretty rare. But it could be a loose zip tie, some insulating paper normally held down by the zip tie, or even a wonky stator that rubs the magnets.

Personally, I'd ignore it if it's inside the motor. None of it affects function much.

It could also be your bearings. I've not had much trouble with them, but a bad bearing can allow the stator to move enough to scrape.

Lift the tire off the ground, and try to wiggle it. If it moves a lot, then it's the bearings.

but it is a front motor.

d8veh · Apr 24, 2014

Be aware that electric problems with the hall or phase wires can make the motor make grinding sounds, so double check that all connectors are tight before dismantling the motor.

If it's a scraping noise, it's more likely a mechanical fault

dogman dan · Apr 24, 2014

Well I was not told a front motor. So we now know it's not the freewheel. :mrgreen:

I have had front motor covers that were just able to rub the fork itself, or it could be a bearing fault if the wheel has lots of play from side to side.

I still have no clue if you are talking about one noise, a scraping, or two. The second being the normal motor growl.

my 9c motor started to make noise

arar1971

100 mW

dogman dan

1 PW

arar1971

100 mW

dogman dan

1 PW

arar1971

100 mW

d8veh

1 GW

dogman dan

1 PW

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