Recorded the pulsed whining of my geared hub. Normal, needs grease, or worse?

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saucerful

10 mW
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May 26, 2022
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Shengyi SX1 hub motor with baserunner and V3 cycle analyst, ~3k miles on it. Pulsed whining noise especially audible at lower power (< 200 watts), both low and high speeds. No sound pedaling with motor off.

Recording here-- indoors, but the same sound I'm hearing on the road (louder in recording).

1) Is this normal sound for a geared hub motor? Honestly can't remember what it was like new.

2) Is this a PWM duty cycle sound? Is it exacerbated by the fact that I have a 52 V battery, fast wind motor, 20" wheel? I changed a bunch of the CA feedback settings and there are no flags being raised for any kind of limiting-- noise persists.

3) Online it is advised to lubricate the planetary gears. Before I try, I'd like to know whether this type of noise is likely to be fixed by that?

Thanks!
 
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What size wheel and what winding did you get?

Most geared hub motors sound like crap at very low load / low speed.
It wouldn't be a bad idea to check the existing lubrication..

How's it sound with the throttle engaged?
 
saucerful said:
Is this normal sound for a geared hub motor?
Click to expand...
Geared hub motors in general will usually produce some gear noise, some more than others. The Shengyi SX, however, has helical cut gears so should be quieter. The hub could be lacking lubricant or possibly have a bearing failure, causing gear(s) to improperly mesh.

Have you contacted Grin? If not, I would strongly encourage contacting them before you decide to open the hub.
 
@neptronix throttle and pedal assist are sounding similar. It's a 20" wheel with fast wind motor (9.8 rpm / V), 52 V battery.

@Papa I just contacted Grin, I was posting here as a sanity check on whether this was even a problem so appreciate your suggestion.

Thank you both!
 

SX1-SX2 - Grin Kits - Product Info

These geared motors fit somewhere in between the tiny G31’s and the more powerful eZee hubs in terms of size and power, and are a highly recommended all-around motor for most conversion jobs. They have a single stage helical planetary gearing to keep the noise down and have been among our most...
ebikes.ca ebikes.ca

"Key Features​

  • Totally Silent Drive: The helical cut gear system of the SX1 and SX2 motors has the same "smooth as silk" feeling that you've gotten used to with the Bafang G3XX series or any direct drive hub motor......"
 
To me that sounds completely mechanical.

Does the sound occur on the same spot at every wheel rotation?

Or does it occur at some specific multiple (like your motor's gear ratio)?

If it only happens when powered and not when unpowered, set the controller to spin the motor in reverse (which won't spin the wheel if it's an internally-clutched/freewheeling geared hubmotor, just the motor itself).

If it does not make the sound when the motor spins backwards, then it is being caused by whatever is between the motor clutch and the wheel hub shell. (whichever part is not spun by the motor because of the clutch)


Also, try spinning the wheel, by hand, backwards. If it makes the sound then, then it's something that is only spun when the clutch is engaged.
 
3k miles. planetary gears and bearings. double heck the planetary plate size. took me a while to get the right one from amazon. the 500 watt motors are most common size. my 350 watt was smaller and hard to find. first, do an autopsy. pop the bearing seals and clean and lube them. check gear condition and scrape all the crap out from between gear teeth.
 
I have the motor open. I don't see any stripping of the planet gears, ring gear seems good too, and bearings seem OK:

1746146910146.png1746146966595.png1746146977268.png

But I think there is another issue with one of the planet gears. Check out this video.

One gear moves with less resistance and mkaes a faint noise. I'm guesing at decent power this translates into the noise I posted above. But I can't tell what's wrong. Plenty of grease no?

What is the problem and how can I fix? How can I take it apart? This is what the other side of the carrier looks like:

1746147441137.png
 
Maybe you have an eccentric gear in the set. Swapping in a new set of gears would address that, even if it didn't solve it.
 
Did the motor make thse noises when new?
How much batt amps + volts you running on it?
What's your terrain like?

I'm wondering if you overheated it very slightly which made one of the gears funny shaped if it didn't do this new.
 
Honestly I can't remember what it did when new! I don't think it made this noise but I was so happy to get it running and often its windy and I'm playing music on a speaker...

52 V battery, never more than 750 W (15 A), usually more like 5-10. The terrain is very hilly, occasionally a little gravel. I've never seen the temp over 75 C.

Shoudl I try to disassemble the stack with the planet gear? How would I do that? there is a thin black horseshoe shape thing that seems to be holding the gear on?
 
neptronix said:
I'm wondering if you overheated it very slightly which made one of the gears funny shaped if it didn't do this new.
Click to expand...
Given the way the torque is transferred thru the plastic, it'd be much more likely to deform teeth (which would probably then be damaged by the sun/ring teeth) than the gear itself into eccentricity.

The planets are "trapped" between the sun and ring, with the gear shaft a pivot to spin on given those forces, to transfer the sun torque to the ring (and thence to the shell). The hub shell axle bearings on either end provide support that prevents compressively loading the gears; they should only see rotational transfer forces on the teeth (and a pivot force proportional to the difference in sun to ring, I think; sorry I don't know the math or physics, just feeling it in my hands and seeing it in my head in my wierd way).

I can imagine a scenario in which a really hard jump down from one surface to another, where that planet is at the bottom of the set and directly vertically impacted between ring and sun, could be damaged in some way (crack, etc) but that would also require a lot of play in that side's axle/cover bearing, which you would be able to see and feel as wiggle in the entire wheel. Or some other gross mechanical failure that allows the hub shell with ring gear to move vertically relative to the shaft / sun by external forces.


It'd be more likely that one gear had a manufacturing problem, or installation problem, or bearing problem on it's shaft, if that gear is not spinning like the others do; if it has play in it that the others don't.
 
saucerful said:
Shoudl I try to disassemble the stack with the planet gear? How would I do that? there is a thin black horseshoe shape thing that seems to be holding the gear on?
Click to expand...
Those are "circlips"; (also called snap rings) you can buy cheap tools with interchangeable tips for different sizes and types, but the cheap ones have lots of play and suck. https://www.harborfreight.com/snap-ring-pliers-with-interchangeable-heads-63845.html
1746159662972.png
I have two dedicated-type/size tools (mine don't look like these, but it gives the idea) https://www.amazon.com/Tusk-Heavy-Duty-Circlip-Plier/dp/B09RTL54WW
1746159686281.png

that I don't recall their origins but are very old that work much better despite their worn state, but they don't fit most fo the ones I need to take off or put on, so I fiddle with the cheap one and do those jobs wtih it.

If you are very careful and have the dexterity for it, you can often use two jeweler's flatblad screwdrivers to hold the pinholes and pull them apart (outside an axle or rod) or push them together (inside a tube or cylinder) and then work the circlip off, but if you don't have it all just right you get to find out why mechanics call them "jesus" clips....because you'll be saying "jesus where the **** did it go!?" ;)

I have once or twice ;) used a big flatblade screwdriver ot fit in the gap between the pinholed ends and twisted, to get it far enough apart to stick a thinner flatblade under it and pop it up on to the shaft itself to then slide off, but that trick does not always work, it often results in breaking the circlip or damaging the groove it fits in, and the pieces sometimes fly toward your eye as if delberately aimed by malicious gremlins. :/
 
At the point you're at I would suggest a proper regrease and reassembly, making note of all the parts you would need for a rebuild. Then a test run.
I wouldn't take apart the planetary gear assembly unless you know that you're getting a new gear assembly (actually I probably would, though that would be opening another can of worms.)
New bearings and seals would also be a good idea if you're replacing the gear assembly, .
 
Thanks all!

gromike said:
At the point you're at I would suggest a proper regrease and reassembly, making note of all the parts you would need for a rebuild. Then a test run.
I wouldn't take apart the planetary gear assembly unless you know that you're getting a new gear assembly (actually I probably would, though that would be opening another can of worms.)
New bearings and seals would also be a good idea if you're replacing the gear assembly, .
Click to expand...

I don't have a replacement set of planet gears and I think your cautious approach makes sense and I should pause while I'm ahead. I believe I've located the cause of the sound and it does not appear to be something that will cause significant damage to keep riding on. I've emailed Grin for assistance...
 
marty said:
Agree
Click to expand...
Alright I'm doing it but I have a concern...

I tapped with a mallet to get the motor out. In the process, the bearing cartridge on the gear side came out. I don't see/feel any damage, and I plan to do more service on this motor soon (after hearing back from grin, getting the right tools/parts, etc). Can I just reseat the cartridge or does the fact that it fell out mean I damaged it/something is wrong so I shouldn't reuse it?

Thanks all.
 
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