Motor spinning but not driving wheel

[davell]

Hello, after some advise please. I have a 250 watt hub motor. A problem has been developing where sometimes the motor is running but not transferring power to the wheel. Is this likely to be the clutch mechanism? Is it possible to fix this?
Here’s a video showing what I mean if this helps.

New video by Dave Ellis

photos.app.goo.gl

 

[vfr400]

The clutch is sticking. You might see why when you open the motor. Clutches are cheap and easy to replace once you can see which type you need.

 

[davell]

Thanks. It’s a ShengYi 36v motor Type: DGWH2S. Looks like a dismantling job then.

 

[Scorpio]

Hi, I think the easy option would be to strip the motor and replace the whole clutch unit once you know what type you need.
I had a similar problem last year (my clutch was locked solid - yours is the opposite and never engages), you might be able to soak yours in solvent (degreaser, petrol, turps...) to free it then oil it and refit.
If not it is possible to dismantle a clutch so you can free the stuck parts but it's not a quick job, I found it educational ...
https://www.pedelecs.co.uk/forum/threads/kemp-starley-dutch-town-bike-out-of-hibernation.37181/post-554543

 

[davell]

Well, I stripped down the motor and found than the left side motor bearing was seized solid. Both bearings now replaced as I bought replacements a while ago but never got round to fitting them. The clutch seems to work as it should. Reassembled and just done a 20 mile test ride and the problem seems to be fixed. I can’t get my head around how a seized bearing would cause these symptoms.
When reassembling there is a washer and nut that goes against the side of the motor and keeps the motor internals together (as pic). Any idea how tight this should be against the motor casing/bearing? I’m guessing it should be slack as tightening it stops the spindle from turning. I currently have it finger tight and then loosened about a quarter turn.

 

[Scorpio]

Sounds like a good result on the bearings / clutch

The nut and washer are either very a different setup to the ones I've seen or something is not right.
On mine there is a washer between the nut and the wheel, the washer is smaller diameter than the casing so there's no contact between the casing and the nut/washer when the nut is tightened up fully. You also need to make sure the washer does not rub on the outside of the bearing.

 

[vfr400]

That looks about right. The bearing has an inner and outer race. Whatever is immediately next to it must only tiuch the inner race, obviously.

I can't see any way the clutch can be affected by the bearings, except maybe if a bearing collapsed, which would put a high upward load on the gears.