FS battle-hardened 6384 high pitched noise at certain rpm range

How-Tos & Esk8 mechanics
#21

I bought a board here on the forum that had same high pitched noise at certain rpm. It turned out that the motors were in very bad condition - lose shaft, bad bearings, lose cracked magnets, bend clip. I’m not sure what had caused the sound exactly since those motors are done, but there is most likely something lose in the motor. Disassembling and inspecting motors wouldn’t hurt if you have time for that.

3 Likes
#22

Mine have made that noise since day 1 - not saying it couldn’t be what you mentioned, but it’s also not necessarily bad

I think some are just louder than others

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#23

yeah I didnt cover the motor when I cut the shafts, im sure there is something in there.

I can try. I will update

i don’t think its necessarily bad, its just annoying.

1 Like
#24

My pinions are offset from the spur gear by alittle. I wonder if that changes the sound. Only one is offset alittle.

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#25

Second this. I posted several videos back when we did the first group buy, shortly after they launched. Mine had this loud squirl at 87-89% duty cycle

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#26

I have the same thing with a pair of 6374 motors.

It screams like hell at some rpm. Really annoying

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#27

I’ve had this on seperate sets of maytech motors before. Really strange

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#28

Same here. Chocked it up to being an harmonic imbalance in the motor. Mine sound no where as bad as OP’s does though. Could be more than just an imbalance. Or just an aggressive imbalance.

I’d pull it apart and check the inside.

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#29

I know this is an old thread, my brand new flipsky 6354 BH motors have the same resonating whistle at a certain rpm with belts and without. Drives me nuts.

It’s annoying enough to consider shelving these and buying a different brand motor.

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#30

It’s gotten better for me over time. It used to happen at a large range from like 29-35 mph, but now it happens only at 30mph and it goes away after that. It’s less harsh too. It might be worth getting new motors if you cant stand the noise at all, but it might get better

#31

It’s highly likely that where the phase wire bundles exit the stator, they wrap around the mount plate before being terminated and exiting through the mount plate. In this small section where they wrap, they are often free to wiggle around a little bit, and not twisted tightly or sealed together with a bonding agent. When these strands of wire can vibrate and hit each other as the magnetic fields inside the wire pulse on and off, they can make vibrating noises just exactly like this, mostly in narrow frequency ranges. This can also shorten the lifespan, as eventually the strands can weaken or shed their insulation.

To mitigate this, simply seal the windings with MG Chemicals 4228 Red Insulating Varnish or another sealant so the strands cannot vibrate around physically. Anywhere strands are free to move around, just put a little sealant on them.

4 Likes
#32

Make sure that the motors have not let the shaft slip at all. It is under a side load after all.

#33

I’ve found a solution to this.

Increase the size of the gap between the stator bell and rotor can.

This can be done by pulling the can out and adding a 0.5mm shim on the bottom of the shaft before reinserting.

You will need to remove shims on the front of the shaft

11 Likes
#34

Thanks guys, I’ll pull them apart and try your suggestions.

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#35

Can the shims be bought or just make them?

#36

Both, try RC hobby online stores for 10mm shims.

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#37

Great thanks again

#38

I haven’t tried adding a shim yet but do you think it’s caused by the bell housing being fully enclosed? Like air whistling through the small gap at a certain rpm speed?

I coated the windings at the entry point but still the same sound.

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#39

I fixed the whistle. I added epoxy to the end of the magnets on the outer lip as they had a scalloped area causing the noise.
They are quiet now.

Thanks for your help with it. :+1:

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#40

Got pics?

1 Like