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

How-Tos & Esk8 mechanics
#1

I finished my diy board a few months ago with boardnamics helical cut gear drives and flipsky battle hardened 6384 motors. I’m using a xenith v1 with 76 amps max per side.
Shortly after completing the build I began to notice a really loud high pitched noise at certain speeds. I assumed at first that it was resonation within the gearbox and I took everything apart to clean and test. I found that both motors make the really high pitched sound at a specific rpm. I recorded it with gears, but it also happens without any gear interactions. its exclusive to the motors themselves. Does anyone have ideas on what it could be. Could it be some debris within the motor, or a messed up bearing?

I don’t think its dangerous. it just makes it really uncomfortable to ride. I feel bad riding around my neighborhood or near people. Its really irritating, much more so than just the gears.

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[EU] 2 x 6374 ( 140-190kv ) Wanted ( Preferably New, Unused.. )
Most silent gear drive or other solutions...
#2

Are you sure you have your backlash set correctly on the gear drives?

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#3

I think that some motors just sing… I have never had two sets of motors sound the same. My first set of flipsky had a super high pitched sound at higher rpms. I did everything I could to try to fix it with no avail. Same thing with different escs. Every setup has its own unique sound.

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#4

That shouldn’t be the problem.

The strange thing to me is that both motors do it at the same RPM… or at least that’s how I read the text. If it were bearings it would be a very strange coincidence if the sound was at the exact same RPM.

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#5

Is this 12s?

#6

This sort of high pitch noise is vibration. Usually due to 2 things

1:motor ain’t properly designed for sustain certain voltage ranges
2:loose or cracked magnet

#7

yes

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#8

it happens when I spin the motors alone as well, the gears dont matter really

#9

it isnt a whole lot of voltage or current. It happens at less than 30 mph and my board goes 41 at full 12s voltage. in that video, i have the throttle barely up, maybe 15% throttle. not much current at all. i think it has to be resonance somewhere in the motor.

#10

it is very similar rpm ranges yes, but I tested both motors individually and they both do it, its definitely not just one motor.

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#11

my old battle hardened 6374s made no abnormal noises at all. its strange and unfortunate that these ones do using then same esc.

#12

Hm well, that being said, my FS motors have a resonance at super high rpm as well, similar to yours, but not as loud. I don’t go that fast and can’t hear it under load though

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#13

Mine sing to high glory in the midrange. If I cruise at that speed I get paranoid of pitbulls jumping fences and chasing me down . The last chase still gives me nightmares at high speed

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#14

I think @jack.luis can confirm this is a fairly normal sound for flipsky motors

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#15

I have m1s and FS 6374s and it sounds normal to me, make sure your backlash isn’t too tight.

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#16

My m1s are queit compared to the AT drives. Same motors on belt drive are quiet. Its definatley the AT drives that resonate at a certain frequency that kinda hurts your ears but it goes away when you go faster or slower. I was thinking I need mo grease

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#17

both motors do it regardless of whether or not there are gears. the motor spinning alone makes that higher pitched grinding type sound at a certain rpm range

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#18

Tom said my board sounds like a laser beam

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#19

I got the same thing. My guess is when I cut down the shaft to fit the gear drives some metal shavings got into the motor and that’s the cause :man_shrugging:

#20

can you look from the side to see if the can is expanding during this event? Should be very obvious if so