Grinding noise in hub motor

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Cyclomania

10 kW
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May 22, 2022
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In one of my builds I have this weird grinding noise. The same as in this video. It only arises at the start when I throttle hard or go up a steep hill.


Any idea what the issue is when this particular grinding noise arises?
 
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According to the description of the controller it will switch back to squarewave if there is an issue with the hall sensors. Do you have a multimeter to check the halls?

Another way to test my theory is to disconnect the hall plug and see if the motor becomes louder or stays the same.
 
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eee291 said:
According to the description of the controller it will switch back to squarewave if there is an issue with the hall sensors. Do you have a multimeter to check the halls?

Another way to test my theory is to disconnect the hall plug and see if the motor becomes louder or stays the same.
Click to expand...
The hall plug is the one with the fiva cables going from motor to controller right? The other three are the phase wires?
 
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Testing halls is pretty universal between most motors.

Red probe strays on positive and the black probe goes to blue, green, yellow.
Move the motor slowly each time to make sure it goes from 0-5v.
From my experience broken hall sensors have multiple failure modes, they can either be stuck between 5v or 0v all the time, or still cycle some small voltage like 1.3v instead of 4.5v.
 
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eee291 said:
Testing halls is pretty universal between most motors.

Red probe strays on positive and the black probe goes to blue, green, yellow.
Move the motor slowly each time to make sure it goes from 0-5v.
From my experience broken hall sensors have multiple failure modes, they can either be stuck between 5v or 0v all the time, or still cycle some small voltage like 1.3v instead of 4.5v.
Click to expand...
Ok but before I put time into this. Could this really happen because of broken halls? This grinding noise? Broken halls, would that not make the whole motor caput and not turning forward at all?

Or could this sound arise from broken halls as well?
 
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The motor will keep spinning with broken sensors as this particular controller has a sensorless function.
I don't really hear a grinding noise to me it sounds like noise is caused by resonance at certain rpm.
If you actually hear a grinding noise you might as well open the motor as there could be rust build up which eventually could seize the motor permanently.
 
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Try the hub motor loaded
See if the bearings are tight or loose
Try a different controller
Open up the motor and see if the gears arent broken, or magnets arent broken or cracked, or rust inside
See if the sound is the same sensored or unsensored, do you have the sensor cables and phase cables in the right order.

Could just be harmonics, I find sound changes over time with wear and tear and age and abuse/mods of controller
 
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calab said:
Try the hub motor loaded
See if the bearings are tight or loose
Try a different controller
Open up the motor and see if the gears arent broken, or magnets arent broken or cracked, or rust inside
See if the sound is the same sensored or unsensored, do you have the sensor cables and phase cables in the right order.

Could just be harmonics, I find sound changes over time with wear and tear and age and abuse/mods of controller.
Click to expand...

It sounds like this. Not sure if this is something people would just ignore and keep on biking?

But it is a bit annoying as you can imagine.

Normal with a worn motor?

Video Unavailable

This video is unavailable.
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It is basically working pretty well except for this.
 
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eee291 said:
Like I mentioned earlier, it's using square wave instead of sine wave.
Click to expand...
I am going to check the hall sensors with the grin test instruction later today 👍.
I have tested it also when blue and green phase wires are switched, and Yellow and green Halls are switched. As in this video:
But it gave rise to the same sound sound during riding.
 
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If one of the halls is broken then it doesn't matter if you switch the wires around. It will only run in sensorless mode. If you want to reverse motor direction then you can touch the learn wires together for a few seconds.
 
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eee291 said:
If one of the halls is broken then it doesn't matter if you switch the wires around. It will only run in sensorless mode. If you want to reverse motor direction then you can touch the learn wires together for a few seconds.
Click to expand...
I have now tested the hall sensors. The red and black looks normal when I probe between them. But as I understand it from Grin's test manual it should switch between 0 and five when the wheel is turned backwards when I probe between ground and colored cables. My halls, when I have the black probe in ground and the red one in yellow, green and blue, are stuck at 4,94. And when I turn the wheel backwards nothing changes. They are stuck at 4,94 all three.

Does this mean my halls are broken then? And what should I do from here in that case?
 
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TNT30 said:
Does this mean my halls are broken then? And what should I do from here in that case?
Click to expand...
The only thing left is to open the motor up, or ignore the noise and continue riding it sensorless.
You might find an obvious culprit as to why the halls failed, it could be rusty water, a chafed wire at the axle or inside the motor etc.
 
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eee291 said:
The only thing left is to open the motor up, or ignore the noise and continue riding it sensorless.
You might find an obvious culprit as to why the halls failed, it could be rusty water, a chafed wire at the axle or inside the motor etc.
Click to expand...
So now we can conclude that it is something wrong with the phase wires correct? Since they did not respond to the turning back wheel?
 
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eee291 said:
The only thing left is to open the motor up, or ignore the noise and continue riding it sensorless.
You might find an obvious culprit as to why the halls failed, it could be rusty water, a chafed wire at the axle or inside the motor etc.
Click to expand...
Do you think this will be lots of work and that it is easier to just change the motor wheel? Or would it be fairly easy to conclude what is wrong when the motor is opened up do you think? I know this is relative but anyway.

I have opened a few motors and fixed them but those were BB02b-mid drives. Not sure if this would go as smoothly.
 
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TNT30 said:
So now we can conclude that it is something wrong with the phase wires correct? Since they did not respond to the turning back wheel?
Click to expand...
Phase wires are the 3 thick ones, and they are needed to run the motor, they are fine since it still works in sensorless mode.
The issue seems to be only with the sensors.
TNT30 said:
Do you think this will be lots of work and that it is easier to just change the motor wheel?
Click to expand...
Of course, it's "easy" to just replace the motor. It's your call.
I've opened over a dozen hub motors, it's not that bad unless it has no removable side cover.
 
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