sound of small knocks when I accelerate

Robi_Cuba

1 mW
Joined
Nov 7, 2020
Messages
10
Hello everyone, I have a 17-inch 3000w Brushless motor that makes a sound of small knocks when I accelerate, in the magnets there is a 10 cm area that you can see that the core hits with the magnets ...
Does anyone know what could be the problem? I already changed the bearings and the problem still continues.
 
If the magnets are being scraped *only* when higher current is being applied, and not at no-load (like spinning full throttle with wheel off ground), then the magnets may not be glued to the rotor there, so when the motor pulls on them hard enough, they pull away from that spot and are able to scrape the stator laminations.
 
When the wheel is in the air, a blow is felt only when I change the gear, when I test it on the ground in 1st gear it hits for x km / h and then it stops doing it, then when I change the gear it continues to hit without stopping, the The last test I did was to try to accelerate as slow as possible and I managed to put the third gear without hitting
 
What does "change gear" mean?

Are you changing motor settings or controls?

Or are you changing gears on the pedal-only drivetrain?

Is the motor controlled by a throttle, or do you have to pedal to make the motor spin?

If the former, do the sounds occur when not moving any pedal drivetrain parts?

If the latter, pull the chain off the pedals in front and tie it out of the way so it can't accidentally get caught in anything, then retry. This will eliminate any pedal drivetrain sounds from any motor sounds, so you can isolate the problems.


If you get sounds only from the pedal drivetrain, then you have something in the pedal drivetrain that is rubbing or catching on something, and you'd have to visually look for where that is and re-align it to fix the problem.
 
I thank everyone who answered me, but I asked in the wrong part of the forum, I have an electric motorcycle not an electric bike, excuse me 🤦🏻‍♂️
 
Hello everyone, I have a 17-inch 3000w Brushless motor that makes a sound of small knocks when I accelerate, in the magnets there is a 10 cm area that you can see that the core hits with the magnets ...
Does anyone know what could be the problem? I already changed the bearings and the problem still continues.
 
No problem. I moved this thread to the motorcycle forum for you.

I also merged your new thread for the same thing with this existing thread, because its' rude to abandon those already trying to help you, and start over like that.


We still need to know what you mean by "changing gears". You said it is a 17" 3000w motor, which implies the motor is in the wheel, so there would be no gears to shift.

If you don't have a motor in the wheel, then perhaps you can post complete details on your setup so we can help you figure out where the problem might be, or at least some ways to help you narrow it down.
 
I have an electric racing motorcycle, with 2 lithium batteries of 72v x 35ah in parallel, the controller is Yuyangking YKZ120150fb 3 speed, the Motor is YUMAmotor 3000w 17 inch.
later I will post more details, photos and videos of the problem
 

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this is the video link with the problem

[youtube]4WGkts9_XLg[/youtube]
 

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replace the bearings with good ones. SKF with DU seals (the brown/reddish seals) and a C3 rating.

also make sure the cover plate that holds 1 of the bearings is mated with clean surfaces on both sides and the rim runs freely when the cover plate is bolted down, rotate the cover in 90 degree intervals if you hear/feel rubbing.
 
flippy said:
replace the bearings with good ones. SKF with DU seals (the brown/reddish seals) and a C3 rating.

also make sure the cover plate that holds 1 of the bearings is mated with clean surfaces on both sides and the rim runs freely when the cover plate is bolted down, rotate the cover in 90 degree intervals if you hear/feel rubbing.

I already changed them and the noise continues
 
then your outer rim is probably bent from hitting a curb or pothole.
 
I already measured it and it's perfect...
i think i will never find out the problem 😥
 

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unless you can perfectly center the rim and turn it without the stator you cant see the bend. it does not have to be misshaped. it can simply be offset. the room between the stator and magnets is generally just 1mm or less. you need to put the rim and the stator separately on a lathe and turn them to see what is bent. you need a large caliper to see the bent portion, a simple ruler will not work as the measurements are too small.

if you have the stator on the lathe you might want to take 0.5mm off while you are at it as its the best and cheapest solution, fixing the rim is very hard. you will lose some efficiency but not much. and its cheaper then buying a whole new motor. unless you were planning to upgrade to a heavy QS motor anyways to make it as fast as it looks.

ps: never use the metal seals for motors. use the DU (brown) seals. the metal ones dont protect against incoming water or crap nearly enough.
 
I was measuring the diameter and the rim does not seem to be hit, then I tried to put the cap on and I noticed that in part where the core hits with the magnets there is a small unevenness
 

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"small" is enough to cause issues...
 
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