Hub motor assembly problem

I recently ordered a DD hub motor from aliexpress from some reputable seller.
His method to pass customs clearance in my country (Israel) was to send the coil and the magnets and casing in separate shipments so it's not really possible to see it's meant for an ebike.
Moving on, I received the parts two days ago and I tried to replicate the assembly process from some video of a QS motor factory.
Everything pretty much went well, I installed the "disc" side of the casing onto the magnet ring, then I inserted the motor axle inside the bearing of the casing and it popped right in, at that time I started to suspect something wasn't right because part of the coil touched the magnets, the coil wasn't in the exact middle of the magnet ring.
I hoped that installing the cassette side cover would align the coil the way it should be.
So I tried installing the casing onto the axle, it took ALOT of force, I was really scared that I was gonna damage the bearings or something but I saw that it was spinning freely so I didn't worry about that.
I bolted the casing, everything seemed to go well until I wanted to test the motor, I didn't have a bike to mount it on yet so I took a wrench and tried spinning the axle while the motor was in place (I don't have a controller and battery yet because they're still on their way, this was the only way that came to mind), but the axle didn't move at all. after removing the bolts and giving a few love taps to the side cover it popped up a bit, then the axle was able to spin freely (with reasonable resistance from the magnets) as it (probably) should. I tried reinstalling the side cover ten times now, but whenever I started to tighten the bolts (I did like a quarter turn on each bolt and then moved onto the one next to it until it was locked tight) I felt friction inside the motor and it was harder and harder to spin the axle until when I really tightened the bolts the axle was supposedly locked in place from the friction between the coil and the magnets touching. I tried bolting the case on with and without washers for like 100 times, I really don't know what to do.
This is my first post and probably like the third time on this website, I don't even know if this the appropriate forum for posts like these.
Sorry for any bad English, I'm also pretty much of an Ebike noob.

If the covers are on the wrong sides, and the motor isn't a symmetrical design, then this could cause what you see.


If there are bolts in the disc brake holes, and they stick out inside the cover (which they can with no disc mounted), they might push on the axle core when tight.


If the rotor and covers are not really well-centered, meanign they are out of round, where the edges/lips of the covers don't center the cover on the rotor the same regardless of how the covers are turned vs the rotor, and the rotor is not centered either, this can also cause it. This you can "fix" by turning the covers one bolt hole at a time vs the rotor, and rebolting it down, until it eventually ends up centered. As long as the covers and rotor were actually originally fit together ok at the factory, anyway--if they weren't, and never did work together, it won't fix it.


If the manufacturer somehow sent a rotor (and maybe covers) meant for a narrower stator, that could also cause it. Not much to do to fix that, but you can measure the widths of everything to see if this is the case.

Similarly, wrong covers for the correct rotor/stator, could do that. (meaning, the bolt edges don't go far enough in toward the rotor, so it's bending the covers down onto the coils, etc).

SInce they were shipped separately, you have no way of knowing if they ever even assembled that rotor and stator and covers together.

amberwolf said:

If the covers are on the wrong sides, and the motor isn't a symmetrical design, then this could cause what you see.


If there are bolts in the disc brake holes, and they stick out inside the cover (which they can with no disc mounted), they might push on the axle core when tight.


If the rotor and covers are not really well-centered, meanign they are out of round, where the edges/lips of the covers don't center the cover on the rotor the same regardless of how the covers are turned vs the rotor, and the rotor is not centered either, this can also cause it. This you can "fix" by turning the covers one bolt hole at a time vs the rotor, and rebolting it down, until it eventually ends up centered. As long as the covers and rotor were actually originally fit together ok at the factory, anyway--if they weren't, and never did work together, it won't fix it.


If the manufacturer somehow sent a rotor (and maybe covers) meant for a narrower stator, that could also cause it. Not much to do to fix that, but you can measure the widths of everything to see if this is the case.

Similarly, wrong covers for the correct rotor/stator, could do that. (meaning, the bolt edges don't go far enough in toward the rotor, so it's bending the covers down onto the coils, etc).

SInce they were shipped separately, you have no way of knowing if they ever even assembled that rotor and stator and covers together.

Click to expand...

The motor was assembled at the factory, I could tell because when i got the covers and the magnets the paint around the bolt holes was already worn off.
My guess is the manufacturer must've taken the motor and disassembled it because of his "special" shipping method, meaning that it was in fact assembled already at the factory like you said, I just hope that they tested it.
The covers are not on the wrong sides, I put them that way the phase wires stick out of the freewheel cassette side. (it was also assembled this way in the store picture, so I figured that's the correct way to do it.)

THe only other thing I can think of then would be the rotor is not symmetrical, and is installed on teh stator backwards.

If it has different gaps on each side, vs the magnets, it might cause that issue.If you can't see or measure any differences from one side to the other, then that's probably not it.

YOu'd have to pull the covers off and the stator out, and put it back in the other way, then covers back on, to fix that.

Other than that, I can only suggest swapping covers anyway, if they can be, just to see if it makes it work correctly.

I'm with AW, and you have the stator in backward, especially since wires typically come out the left side of the motor, so your chain can't tear up the wiring harness. It may not just be the covers swapped though, since the rotor could be backward too. It's quite common for the magnets to have more space on one side of the magnet backing ring than the other in which case there's only one correct way.

Sorry for not being so active, I did find out the covers are on the wrong side, but now I can't get them out!
I have tried following someones advice to remove the bolts on the cover and bang the axle on the floor until it pops loose, it showed little to no progress (and I pissed off the whole building).
I tried to do something another guys advice to try and unbolt the disc side cover and try to twist it until it pops loose, no success either.
Later I found out there was another picture on the store page where the cables are seen coming out from the other side, I have no idea why the seller would upload such a misleading photo.
Anything I can do?

Try a three jaw puller to get the covers off the axles. Then figure out which way to orient the motor core into the magnet ring, and which side to put the covers on. It will take a bit of thinking to get it right, but if you look close at the dish of the wheel, and the core, you can figure it out. Then the disk side cover goes on the left, gears on right. Or if a front motor, just disk to the left, always.