High pitch whining noise FOC Helical Drive

Hello everyone, I am having this annoying high pitch whine whenever I hit 20mph on my eMTB after I get to about 25mph it will stop and be smooth again but I ride a lot in this middle range. My setup is 12s with FOC boxes @CarlCollins . 190kv 6374 from @torqueboards and 1:5 helical drives from @Nowind. Can anyone shed some light on how to eliminate this? My switching frequency is 30khz but it wasn’t any better at 20

Edit: sometimes it is very smooth into and out of the whining but other times the sound hits a brick wall and just stops on a dime

Link to video: https://youtu.be/_qZ143e7yH4

I’ve had something like this with one of my APS motors, the outer ring and a couple of the magnets had partly come loose and were creating a fairly ugly whine in a certain RPM range. Maybe try figure out if the noise is coming from a specific motor and if so, pull the motor apart so you can inspect the magnets inside the can


Yep, loose magnets are most likely. Check the windings as well

Edit: loktite 648 should take care of it

Damn. Ok. Luckily I got some green loctite sitting around so I will try to fix this tonight. Just put some loctite on the magnet and then place it in the can?

Is there a quality motor that doesn’t have this issue? I have seen way too many cases of loose magnets recently

I will mark it as a solution once I get it solved😉

image image @torqueboards what is the problem/ solution here? I can’t see any obvious loose magnet but this wear is all the way around both the stator and can

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@trdolan03 - You’ll probably have to send that one in. Consistency on one of our latest batch hasn’t been great on our 6380 Black. We have some new ones in production but won’t be done until next month. Send us an email and let me know your @trdolan03 so I can remember this issue.

I still haven’t isolated the actual high pitch noise specifically though.


@torqueboards This is a 6374.

@torqueboards , exemplary customer service! @Trdolan03 , that’s what you should do with the motor!

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I added a video link to the original post. Watch only from 40 seconds to the end

@torqueboards email sent

So the motor in the pictures is not longer on my board and I am running single drive atm. Still getting the whine but now at 25-28mph. @Nowind Could this be a function of the helical drives?

@Trdolan03 Please confirm is your setup is FOC or BLDC?

I’ve tried both and they both produce the same sound

@Trdolan03 If you are in FOC mode, try adjusting the frequency to 31K-35K using VESC tool

I tried 20k and 30k. I can try 35 tonight

No luck changing to 35k


Have you asked @torqueboards about it?

100% not, they sound (I mean they don’t sound :laughing:) equal no matter which speed.

This is for shure the motor. This whining sound reminds me on faulty APS 80mm motors which people posted. I know exactly how you feel now, chin up bro! I am also still searching for a reliable motor which holds longer than a few weeks, it’s really frustrating.

These motors in general are made for hobby RC models and not for human transport I think this is the main problem regarding safety and reliability.


let me know in case you found one… the problem is, when you think there is one long lasting motor they change something in production and the next who buy get shit again… how about your sk8? still goes strong or already gave up?

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