Rear hub motor wobble, axle or housing?

[c111jp]

I did a stupid thing... I have this style of rear hub motor. Has 500w stamped on it but I see same motor being sold as 500-1500w usually. Been using it for 9 000km - 2 years without any problems (bought it used, not sure how much it did before but it was nearly new).

I wanted to upgrade phase wires since they are very very thin so I went to open up the motor. I took the freewheel side cover off with relative ease. Actually almost too easy, bearing should bite a bit stronger to the axle than that in my opinion (bearing stayed in housing at least). I've removed stator along with 1 cover still attached out of rotor. Since hall and phase wires are on the disc side I had to try and take other cover off. Didn't seem like it will go as easy as other side. I don't have puller of correct size so I've put a nut on the axle, mounted stator / housing in the vice so that housing's edge is on the flat but stator can move freely and gave axle a couple of whacks. Axle or bearing didn't budge even the slightest and since the bearings / axle has virtually no free play and still seem good, I decided wires are good enough for now and gave up on the idea.

I've cleaned, greased and sealed up motor with a bit of RTV since it had quite bit of rust on the stator / magnets. I've replaced rim, spokes (12 to 14 gauge) and freewheel with new DNP 7-speed 11-28T since the 14T was too short.

Upon wheel building I noticed motor itself is wobbling a bit. I managed to get the new rim trued almost perfectly, but the motor itself is wobbling along with the freewheel and disc of course. It's not insane amount but it's more than it should. It's enough to move the chain back and forth a bit. It's very obvious if I spin motor full speed in the air along with whole bike shaking. I am 95% sure it didn't wobble before.

My question is, what is more likely to be bent on these, axle or housing? The thing is, visually axle looks straight and if i spin axle alone, there is no signs of it being bent and when I do so there is no jumping of freewheel or anything (I can spin it very slow though). Axle is 14mm. Housing is alu but seems pretty strong. Honestly, both seem to be pretty tough and those couple of punches that didn't even move a bearing don't seem like it would be enough to bend anything. Otherwise it would've surely bent on some of the jumps of the curb or over nasty holes I had. So I'm a bit puzzled here. Anyone's thoughts?

 

[AGS]

This fella had a similar problem:

It’s not a good idea to smash the unprotected end of the axle against a concrete floor, so don’t copy him. If you do have to resort to violence when you take it apart for inspection then at least put the nut on the end of the axle to protect the threads.

Here is another one:

These guys are working against the clock, so don’t have time to be gentle or they will be fired for being too slow.

 

[amberwolf]

If the covers were not marked along with the rotor before removal, to know their original positions, then if they were not machined correctly installing them in different rotational positions from original could cause what you see.

To test this you can mark the covers and rotor, then try rotating one cover by one screw position and retest. If it doesn't change, repeat until you are back to the original position. Then try the other cover the same way. If neither changes you can increment one cover one position, then try the other cover in each position, then increment the first cove, then retry the other cover, etc.

FWIW, sealing the motor up at the cover edges won't usually keep water out. The water more typically gets in via the bearings and the wiring. It only takes a tiny bit to get in even as just humidity to eventually rust unprotected steel. (see ebikes.ca's blog page, some years back there is a post about water ingress and testing, and there are some threads about it here, too).

 

[c111jp]

This fella had a similar problem:

It’s not a good idea to smash the unprotected end of the axle against a concrete floor, so don’t copy him. If you do have to resort to violence when you take it apart for inspection then at least put the nut on the end of the axle to protect the threads.

Here is another one:

These guys are working against the clock, so don’t have time to be gentle or they will be fired for being too slow.

Not a bad idea if in pinch, with all precautions taken of course. But honestly mine is stuck so strong that it doesn't seem like this would work.

If the covers were not marked along with the rotor before removal, to know their original positions, then if they were not machined correctly installing them in different rotational positions from original could cause what you see.

To test this you can mark the covers and rotor, then try rotating one cover by one screw position and retest. If it doesn't change, repeat until you are back to the original position. Then try the other cover the same way. If neither changes you can increment one cover one position, then try the other cover in each position, then increment the first cove, then retry the other cover, etc.

FWIW, sealing the motor up at the cover edges won't usually keep water out. The water more typically gets in via the bearings and the wiring. It only takes a tiny bit to get in even as just humidity to eventually rust unprotected steel. (see ebikes.ca's blog page, some years back there is a post about water ingress and testing, and there are some threads about it here, too).

That's what I was thinking since I didn't mark anything. But then again that would mean they need to match every single one in the factory and that just doesn't seem cost effective compared to just producing housings that are balanced and up to spec to begin with.

Anyway, I took it apart and seems like disk side cover (the one that took the hits) is slightly bent. I've played with it until I could clock it into position where it wobbles the least and then re-trued wheel. Not perfect, but way better than it was. Now I have problems with grind / noises under certain load and throttle. Seems like something with halls but not sure anymore. Will start another thread.

As for sealing, I did seal wiring holes in axle and everything else but I removed RTV when I opened it up to minimize chances of it sitting wrong. Instead, I greased everything up.

 

[amberwolf]

That's what I was thinking since I didn't mark anything. But then again that would mean they need to match every single one in the factory and that just doesn't seem cost effective compared to just producing housings that are balanced and up to spec to begin with.

You'd think so....but it isn't uncommon for this problem to happen when covers are installed differently than they were at the factory. I don't know the specific order of machining processes they use, but I suspect there is some order of operations that causes this problem that wouldn't if they did it differently.