Faulty freewheel on cold mornings

[Sector]

Winter mornings seem to disgree with the geared brushless hub motor in the front wheel of my old Ezee Chopper. Sometimes when I turn the twistgrip I can hear the motor running but the wheel doesn't turn.

It only happens below about 3 degC. Above 5 degC the problem mostly disappears.

I'm guessing that the freewheel has become a little sticky and reluctant to engage. Has anyone had this before in Ezee Sprint or Chopper motors or other hub motors? What's the remedy?

I suppose I'll need to take the cover off the motor and have a look. Are there any tricks to pulling this motor apart? How does the freewheel work, and can it be cleaned or refurbished?

 

[flecc]

I doubt if there are any special tricks for stripping the motor once the side plate is off, just watch out for any shims on the shaft ends. The Chopper uses the Sprint motor of course, but I'm not very familiar with it's internals so I don't know the freewheel position for certain. It's probably a ball and ramp type and with grease congealing in it when cold, it could be preventing the locking. There's a photo below of the Sprint motor when withdrawn from the hub and the freewheel is probably just behind the front plate there. I can't properly see the removal arrangement in that photo, but it looks like it could have a circlip on the shaft for releasing the gearwheel assembly:

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[Sector]

Stripdown

It was easy to open up the motor. I didn't need to disconnect the supply cable. I took out the cover plate screws, tapped the blade of a sharp knife into the joint between the coverplate and the casing, going round and round so that it lifted evenly. then lifted the cover off. I lifted out the windings. There were shims on the opposite side, thanks for the reminder.

The first photo shows the view inside the casing. The rotor with the ring gear runs on what appears to be a ball bearing, but this the overrun clutch. It certainly looks big enough for the job.

I was able to reproduce the fault. Most of the time the ring gear could not be turned backwards, but occasionally the clutch failed to lock.

The clutch is marked BB35-K-P and SX8. I've looked this up on the web and equivalents seem to require oil lubrication rather than grease, if they need any attention at all.

I was able to prise off the brown plastic seal, and I'm hoping it will pop back into place whem necessary. It is shown inverted in the photo.

I don't plan to dismantle any further as this would mean disturbing the press fits, so I only have access to one side of the clutch. I don't want to dunk the whole lot in degreaser because there is another bearing beyond the clutch, which I can't protect.

The maintenance instructions warn against putting anything too slippy, like EP grease, into the clutch. I suppose WD40 might also be a bad idea to try to flush it out. They just recommend 68 grade oil for our ambient temperatures.

I'm thinking of placing the casing with the exposed side of the clutch at the bottom and spraying upwards into the clutch with a solvent of some sort, maybe switch cleaner, then relubricating with oil. Any comments or improvments on this?

I also took some pictures of the hall effect sensors side of the windings. This is not relevant to the current problem, but might be useful to someone later. The sensors are marked S41 523LF.

 

[Sector]

Another photo

Here is a photo of the planet gears, just for the record. The shims are also visible on the shaft.

 

[flecc]

Thanks for the photos, they'll be useful for others as you say.

Spraying with a solvent and draining, then oiling should work if done with care, though even thinning with fresh oil might be sufficient to allow the clutch to function reliably.
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[Sector]

Oiled and reassembled

I've trickled about 3cc of clean oil (multigrade car engine oil) into the clutch. The brown plastic cover ring clipped nicely back into place. I've reassembled and done a short test ride. There is no sign of the freewheel slipping so far, but I'll need to do a few cold morning rides to really check it out.

 

[flecc]

That's great, best of luck with it, I think the fresh oil will do the trick.
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