Hub motor grinding sound

[Ykick]

I opened up the hub motor. Just as I thought, after seeing a couple of other people with this problem, there are visible marks of the stator rubbing against the rotor magnets. Since this only happens after the motor is warmed up, I don't understand... why/how it happens?

The included thread link up above just mentioned bearings, but I don't see how they can be the problem.

If the cover's not flexing it's almost certainly the bearings. In fact, when the bearing remains in the cover when you pull it apart, that often goes with this trouble.

The cracks look weird but I've seen surface cracks look like that before and they didn't go all the way through and compromise structural integrity.

Definitely, drive the bearing out with a punch and see how it goes?

 

[kentlim26]

if the Covered properly, There should be smooth rotate forward and backward. I have this problem before, I didn't closed them properly, so it rub against the magnets . it feels like a rubbing against something?? please take it out again, and cover them. It cannot be too hard knot , I will use a wooden knot in the center when closing hub motor cover. It has to be done properly, and try again.. - does it rotated smoothly. ? When is rub against the magnet, is feels like a braking roughly. The motor look very NEW copper wire, very nice.

 

[speedmd]

Cover looks like it has casting flow lines to me. Slightly cold material, and or mold will do this with most stuff. Most likely a loose bearing or bent axle/ shaft causing the rub. Like the idea of the wooden (knot ? ) dowel used to line things up better and maintain center as it slams together.

 

[e-beach]

...... Since this only happens after the motor is warmed up, I don't understand... why/how it happens?

Hot stator, cold riding conditions. The cool / cold of your riding conditions kept the hub at it's original size or a bit smaller do contraction of the hub metal in the cold. That combined with your stator heating up and expanding. Between the two your magnets and stator started to rub.

Could be your barrings are toast, but it could be that you got a hub motor with close tolerances from the factory and the cold hub and warm stator did you in.

I have seen motor parts put on a lathe and turned down a bit to give a smooth surface. Cost of turning your stator might be cost prohibitive though. Your local machinist could give you an answer to that question.
.

 

[999zip999]

Ykick I think the bearing is suppost to stay in the cover. As a press fit.

 

[Ykick]

Ykick I think the bearing is suppost to stay in the cover. As a press fit.

Yes, I think my comment is wrong or at least non-conclusive. I've only pulled one motor apart to date and the bad bearing just happened to remain in the cover while the good bearing remained on the shaft.

It was very hard to tell the bearing was bad - it didn't feel loose with finger pressure but under loaded condition the bearing was indeed loose. The only "sensation" I noticed was it spun real easy, too easy, like it had been dry.

 

[999zip999]

Moved

 

[999zip999]

Removed

 

[mateusleo]

I'll give it a shot:

You said that the noise only comes up when the motor is warmed up. Well, the thing is that the heat in the stator(i dont know is the right name is stator, i mean the center of the motor, with the copper wires and stuff) is higher than in the covers, because the first has no contact with the atmosphere and the latter does, which implies in a considerable temperature diference between those parts. If the stator is in a higher temperature, it will expand more than the covers and that may result in the touch of the parts and noise. Thats my theory.

 

[999zip999]

Skedge Sky I guess I jumped your thread hope you don't mine. As I have a clunk clunk noise I think from the bearing but it run till the phase wire got cut and had to take apart and a must have look see.

 

[Skedgy Sky]

Skedge Sky I guess I jumped your thread hope you don't mine. As I have a clunk clunk noise I think from the bearing but it run till the phase wire got cut and had to take apart and a must have look see.

I partially do mind as it appears the noises you describe seem to be different than mine along with having a burnt phase wire.

In reply to all the people who have replied:

-I have done jumps, hit potholes, etc, but the "cracks" are not actual cracks in the side covers.
-I hammered the bearing on BOTH side covers to see if they would come out. Both bearings stayed in place IN the side cover.
-Axle appears straight

I took the other side cover off:


Axle appears straight.


Rotor turned 90 degrees, axle still appears straight.


Bearing on the rotor side:


Bearing on the stator side (as shown in video below):



Now.... this:

http://www.youtube.com/watch?v=65H-jegN9_Q
Could it be possible that the rubbing is caused by a crooked side cover, and not the bearing?
..the stator expands when it becomes hot and the portion of the side cover closer to the stator forces the rotor to be closer on that side, which causes the already slightly bigger rotor (due to heating) to rub against the rotor magnets at those parts?
What can be done to solve this?

 

[999zip999]

The bearing just looks rusted in on the side cover and the cover looks like it could be warped or bearing. Maybe you bent the axle ? Yes my noise is more of a clunk and not a swissh likes yours. The phase wires problem just started last night. Just put the other motor on so no hurry.

 

[John in CR]

Did you turn the bearings with your finger to feel if they are bad? A bad bearing might do that. Those bearings don't even look like they're fully seated to me.

For future reference it's good to mark your covers and rotor ring, so they can be reassembled in the same position. I use a center punch and put 1 dimple on the cover and ring on one side, and 2 on the other.

 

[speedmd]

Warm up the covers and the bearings will most likely pop out very easily. They look like its time anyway and when you are this far apart it is something that should be done if it has some miles. If made correctly it should be a mild press fit and if tight, heat the covers slightly 150 -180f to make things go back together easy and soften any locking compound that may be residual and preventing the bearing up from bottoming in the pocket.

Would be great if you had a inspection window you could feeler gauge the gap while rotating the covers to help find most centered/ original home position. It should be marked some where.

 

[John in CR]

Check the bearings before removing them, so you know definitively whether one or both are bad, since they're quite likely to get damaged banging them out. If not notably bad, then the motor is toast, which to me it is anyway since many of the stator lams are shorted at the ends. I'm curious whether the bearings are even bad enough to let the motor rub, because that side cover looks bad to me. There's no way I'd trust my life to one that looked like that, but I ride around and 50 and even 60 mph.
I've had bad bearings before with no rubbing of the stator, so at least one has to be quite bad for that to happen.

John

 

[Skedgy Sky]

Check the bearings before removing them, so you know definitively whether one or both are bad, since they're quite likely to get damaged banging them out. If not notably bad, then the motor is toast

I spun the side cover by the bearing using my finger and they spin just fine. I couldn't possibly have gotten bad bearings... the whole cover never appeared to spin perfectly from the beginning. Can it be just that the side cover wasn't manufactured perfectly centered on the bearing or the side cover isn't circular and is slightly warped (like I show in the video up above)? Again, I've had this problem since the beginning when I first bought the motor.

 

[John in CR]

I wouldn't waste any time or money on it. Look at these stator lams from your previous picture.


Many of those are almost certainly shorted together. Check for continuity with a multimeter if you don't believe me. What looks to me what happened is that the machined holes for the bearings were too small, or too cold that day or whatever, and the bearings weren't fully seated. Then the side covers were bolted on anyway, putting lateral stress on the covers. Then you go jumping and hitting potholes, but aluminum doesn't perform well when the metal is under stress, and that cause all those small fractures. Finally the sides lost enough integrity that the rotor ring is enough off center that when the stator expands when warm that it starts rubbing the magnets. Now you have a significant portion of laminations that are shorted, which is increase iron losses and heat a lot, and you have side covers that look like they lack structural integrity. Either of those is catastrophic enough to write off the motor.

It's early May, get yourself a new and better motor. If a new motor has an alignment issue when new, return it for a refund, and don't buy that brand ever again, because they obviously don't inspect their motors before sending them out the door. For a motor factory, it's inexcusable not to spin up each and every motor to make sure they run and spin perfectly.

John

 

[e-beach]

@ John in CR,

Ok, I am definitely not clear on the concept of shorted motor lamination's. I can see by the pictures what you mean by "shorted" but I don't understand the importance of keeping them separated.

Can you elaborate a bit?

Thanks!

 

[John in CR]

@ John in CR,
Ok, I am definitely not clear on the concept of shorted motor lamination's. I can see by the pictures what you mean by "shorted" but I don't understand the importance of keeping them separated.
Can you elaborate a bit?
Thanks!

They are electrically separate laminations to reduce eddy currents in the stator steel. A block of steel would just be a heater, so some shorted lams would be something in between. Common motor lams are already too thick AFAIC and are a big part of the relatively low efficiency, so shorting a bunch of them together is that much worse. Farfle ended up with some shorted lams just in in one spot on his double wide magpie motor, and if I recall that ultimately lead to it's failure.

 

[speedmd]

Would agree with John in CR. It would be very difficult to scrape out the shorting slivers of iron and re apply something like the original oxide coating to insulate between lams.

When you knock out the old bearings it should show that they were not fully seated as it appears from your photos. If so, John in CR analysis is spot on.

 

[e-beach]

Separate laminations to reduce eddy currents in the stator steel. A block of steel would just be a heater, so some shorted lams would be something in between. Common motor lams are already too thick AFAIC and are a big part of the relatively low efficiency, so shorting a bunch of them together is that much worse. Farfle ended up with some shorted lams just in in one spot on his double wide magpie motor, and if I recall that ultimately lead to it's failure.

Do you think that there would be any value in having the stator turned on a lathe to reduce the overall diameter a few thousands, cleaning it carefully with a magnet and then spraying it with a suitable lacquer?

 

[eBikeJunkie]

I am now having this same issue as well. Pretty much identical motor and issues. Was there ever a solution, or did you scrap and just get another motor?

Thanks!

 

[Skedgy Sky]

I am now having this same issue as well. Pretty much identical motor and issues. Was there ever a solution, or did you scrap and just get another motor?

Thanks!

Can you give more details on your issue? Do you have a video of the problem? Pictures? I'd like to see!

I contacted the amazon seller and they replied back saying they'll contact vender to get a replacement, although I'd have to pay shipping both ways I think. ($30 each way) I asked some questions and waiting for another reply.

John in CR's posts taught me something about the stator laminations today. Thanks.
Although, it seems I still continue to not understand when you say the bearings aren't fully sealed. I believe the "rust looking stuff" around the bearing is really adhesive. It doesn't feel like rust and the bearing spins fine as shown here: http://www.youtube.com/watch?v=MzsA3kAYPo8

 

[e-beach]

......
John in CR's posts taught me something about the stator laminations today. Thanks. ........

+1

 

[John in CR]

e-beach,
I have no idea if a lathe would work, but you'd increase the magnetic gap in the process, a bad thing. I wouldn't ride on a wheel with covers like that even if I didn't consider my time too valuable to mess with a what seems like a dead motor. If you have the tools and inclination, then include turning yourself up a new set of covers, and then you might have something.

SS,
The bearing isn't flush with the cover, and that's what makes me think they're not fully seated. If they are, then maybe they're the wrong bearing and that caused the problem. Since you spun the bearing with your finger and there wasn't readily apparent looseness to allow the rotor to get off center and rub, then the problem has to be that one or both side covers have lost some of their structural integrity. The rotor ring and the stator obviously haven't changed size, so if there's no slop in the bearings, the covers are shot, which is what it looked like to me in that initial picture of the inside. I've never seen any covers like that.

John