FIXED Cromotor v2 RUB, MAGNETS came UNGLUED!

Harold in CR said:
From lots of mechanical experience, that side cover IS cracked and useless. Try to fit that same bearing into that side cover. I would bet it will slip right in.

A ball bearing should turn freely after a few hours of spinning. If it feels "stiff" it could be NOT turning, and has definitely been spinning inside the case socket.

When the bike is running on the ground, as long as that case is ground out at the bearing, the entire magnet ring will be rubbing on the stator, BUT, not all at the same time, the weight of bike and rider will cause the stator to rub on the ground side of the stator, from the WEIGHT. Same as a flat tire is only flat on the ground side. :roll: It does NOT have to be oval shaped for this to happen.

Get another side cover, get BOTH new Japanese or German bearings and clean up those magnets with alcohol or something that won't attack the epoxy, and I would bet you are good to go, IF those magnets have not come loose from the friction heat from rubbing. THAT is the million dollar question.
Click to expand...

I asked in an earlier post for him to examine inside the bearing holes to look for cracks, if they are cracks that are of concern they will show up on the machined face, if they cannot be seen on the machined face then they are casting marks not cracks, the bearing will most likely still be a good fit and this is not the problem. It is easy to determine if this is a problem or not.

It should only take a couple of minutes to diagnose the problem, examine the holes, check the bearings and there fit and rotate the stator supported on its bearings and the answer will more than likely be known.
 
I don't care about the marks in the FACE of the bearing socket, I am seeing the POLISHED areas in the SIDES of the bearing socket, that show spinning of the bearing.
 
Harold in CR said:
I don't care about the marks in the FACE of the bearing socket, I am seeing the POLISHED areas in the SIDES of the bearing socket, that show spinning of the bearing.
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At least for this motor type I believe the polishing or burnishing is indeterminate. I took apart my brand new Cromotor V3 and the bore looks exactly like that. The factory may size the bores by pressing in a hardened, polished precision rod which leaves that type of finish.

I agree with your recommendations at a minimum, however. I think everyone has given solid advice. It would have been helpful if the OP had provided all the relevant info regarding the operating condition of his bike, his riding style, the fact he managed to flat spot a motorcycle rim, :shock: in the first post. It's like going on a treasure hunt with half the map missing, but your partner has that half in his back pocket.
 
Just an update. I was going to try and check the axle by e-beaches method. How do I get the bearing out of the wire side? What part of the bearing should I push on?

Since I had to press back on the bearing in the freewheel side, I decided to put my motor back together and also put the covers on differently, same side but different holes.

After putting everything back, the motor was very easy to turn, there was only a very faint scratch noise at one point of the turn (same exact point, about 10 to 20 degrees of rub), so unfortunately it is still rubbing. But the motor went from very hard to turn to very easy to turn with only a very slight scrape sound at a very small part of the turn. When it rubbed last, the motor was cooled off overnight, so I doubt it had to do with heat and expansion.

One other thing, I probably shouldn't even point this out as the noise is so low it is probably normal. You can hear a very slight rub sound from the bearing when turning it, but the bearing feels solid and smooth, with no play. The noise is so low most of you probably wouldn't even hear it. I figure the balls in there have to make a little bit of noise. I could have also damaged it when pulling it off with the gear puller.

I have different side covers with bearings coming to me. Do you think I should still try and check the stator/axle or should I just wait for the new covers and bearings?

How do I get this bearing out?

 
What is stopping you from just pulling the wire through the bearing? Connectors? Take them off and reattach them later. If you can't take them off, cut them off and reattach new ones later. Once the phase / hall wires are out of the way, put the side cover on a thick rag over a solid surface and tap out the bearing using a socket that is the same size as the bearing inner race.

If you really don't want to cut any connectors off, just put the bearing seats of the axle on the blocks and do your best to measure.

:D
 
If the cables have Anderson connectors on they are probably just clipped together and can be separated to allow them to fit through the bearing. Then knock the bearing out with the largest socket you can fit through the hole in the side plate.

Harold in CR said:
I don't care about the marks in the FACE of the bearing socket, I am seeing the POLISHED areas in the SIDES of the bearing socket, that show spinning of the bearing.
Click to expand...

LoL in your opinion, not fact!
It would be nice if the op did infact take some of the advice and help he asked for and do some of the checks recommended to him and let us know what he found,
 
Video here on how to take a hub motor apart, its no a cromotor, but same sort of principle :
https://www.youtube.com/watch?v=lkGgAWHSayU
 
The castings look to be of poor quality, if they used Quality Control they would be rejected but if they were all like that some high up manager has probably over-ruled the proper decision to meet production targets. If is their 'normal' standard this puts enough doubt on the Cromotor production to consider not buying the motors.
 
I just replaced the axle in my HT3525 and also upgraded to 2RS bearings as well.

To remove, I used a 3 jaw puller with a 1/2" socket (but that's the size for my 6203 (iirc) bearing). A little heat and WD-40 on the cover (avoiding the bearing) will help.

You might not be able to use a puller with such a large diameter motor though. I just happen to have drilled holes in my cover that were perfect for this. As for what surface to press on, when removing a bearing it is OK to press on the inner race since you will be ditching the bearing afterwards.

For installing, I use the old bearing and a mallet to tap it in place. The old bearing, lined up right, will transfer the impact to the outer race.
 
MAGICPIE3FOCUSPOWER said:
Waauww I would expect more quality for the high price you have paid for the motor :shock:
Hmmmmm.......Cromotor is design in which country?
Click to expand...

Croatia i believe. Made in China
 
I worked on my motor some more and found something interesting. I really need your advice here.

First, I got new side covers with bearings in them. Put them on the motor and I did not hear or feel any rubbing. However...

I then dismantled my motor and noticed something interesting. The magnets that are all around the side of the motor case, some of them shifted up to a 1/4 inch. While pushing out the stator the stator pushed some of them out of alignment. I would say about 6 magnets together all moved about 1/4 inch. I was able to push them back with an allen key, so they are able to slide around. I needed to push somewhat hard to slide them back into place.

What I do not know here is if the magnets should be this loose? It seems that possibly they are held to motor case by magnetic force only.

Maybe this is normal, maybe the magnetic force is all that is needed to keep them tight against the motor case.

However, if this is not normal is it possible that I killed the epoxy by heating up the motor too hot and what is actually rubbing is magnets being pulled off the motor? Something just doesn't add up here. Something else I noticed is that the epoxy that held the temp sensor to the stator completely got hard and basically fell off completely. I was able to turn the pieces of this epoxy to dust like a crumb by just squeezing them in my hand.

What doesn't make sense is if the magnets are supposed to be epoxied and not shift around, then how was I able to use the motor for so long with the magnets like this? I do know that even if the magnets pulled off the motor case while spinning, it wouldn't get jammed up because the tolerances are too small between the stator and the magnets for this to happen. Being that it seems all my magnets are able to shift around, it must be normal.

Right now I have the stator on my milling machine clamped down by the bearings, the stator looks straight to me, however, I just did a prelinary check as I'm working on it now and will get my dial indicator to check for perfect roundness. But so far the stator looks round and the axle isn't bent.
 
Wow you may well have seriously overheated that motor! The crumbling epoxy for your temp gauge is a clue. All magnets should be glued in to the can/hub casing. Some cheaper outrunners have dramas with magnets being loose but that's manufacturing issues. The magnets need to be glued as during use they are attracted/repelled even more to the stator as that becomes electrically magnetised. If they aren't glued or the glue fails, the magnets may be pulled towards the stator and rub as in your case. TBH I hadn't even considered this option before.

If the epoxy holding the magnets is stuffed, then you'll have to re-epoxy all the magnets. If you don't, more will come loose and cause that nasty scraping noise. I must admit I haven't seen magnets coming off a hub motor like that before but obviously it's happened here.

Use a decent quality high temp epoxy- JB Weld, Devcon etc. Clean all traces of the old epoxy off and only use a small amount per magnet- you want them as flush to the hub casing as possible.

Make sure you don't flip any magnets over as well when re-attaching!
 
By the way, do you know what sort of temps you were running?
 
Gregory said:
I think Ypedal may have a video about re-gluing magnets on the rotor.
Click to expand...

Thanks, I found the video and watched it. Interesting. I notice even though his magnets came loose they were still stuck on there really good like mine. So it seems obvious that my magnets unglued as I can move them around. Unless of course I broke them loose by pushing out the stator. Sometimes when pushing out the stator it goes off center a lot maybe cranking down on that gear puller was able to break them loose, I just honestly don't know.

You can see from the original pictures I took of the motor opened, the magnets were all lined up correctly. I have not run the motor since then, I only put the motor back together and took it apart. I'm going to think pushing out the stator shouldn't break the magnets loose, even if the stator is pushed out at a bad angle.

I did notice one of my magnets was cracked and separated, I was able to push it back together. Although Y-pedal says that this messes up the polarity or something.

I'm thinking maybe I should get new magnets if that is even possible. With all the trouble here I am thinking my motor is perhaps FUBAR.

Do you think maybe I should just put it back together and ride it again? It seems with the new covers nothing was rubbing.

EDIT: one thing that is interesting he said is that he was able to ride home, however when he gave throttle there was no grip so the magnets spun internally. Is it possible from the video in my first post that the noise you are hearing is actually the magnets spinning internally? That would explain a lot.

Maybe, my loss of power is actually the magnets all spinning internally and that is why during hard acceleration from a stop I was noticing a rubbing noise. When my motor got some speed going I was able to go top speed without rubbing because the magnets were strong enough not to move.

What I don't understand is that, what happens to the magnets exactly if the epoxy failed? Will they really just spin around the inside of the motor?

The other thing is once the epoxy failed, why does it seem that when my motor heats up it is more likely to lose power from the start or going up a hill from a stop. Basically, it seems the magnets are more likely to spin the hotter the motor is. Once that epoxy fails, wouldn't it just spin freely? Or possibly the epoxy cold is acting as a rough surface so the magnets are less likely to spin around?

Here is what I described some weeks ago, this is actually from page 1 post. To me this seems like the magnets are all spinning inside the case.
http://endless-sphere.com/forums/viewtopic.php?p=914862#p914862

What seems to be happening is as the motor heats up it somehow loses power so that if I give it full throttle from stop or moving slowly the motor won't propel me forward and just make a buzzing sound. Easiest way is if I am stopped on a hill, if I go to give it throttle the motor just buzzes and doesn't have enough power to turn.

once I get moving, I can give full throttle and it works normally.
Click to expand...

EDITED Again: Found a very similar problem from someone else. He has all the same symptoms. Here is the first post, then the next page it is discussed a lot.
It seems his issues get worse with heat or doing a steep climb.
http://endless-sphere.com/forums/viewtopic.php?p=761805#p761805



What do you think? If the magnets are spinning inside the case, does that mean they are also rubbing the stator?

[youtube]qrSRQTln6wQ[/youtube]
 
It could be magnets spinning... or just pulling away from the iron backing and hitting the stator.

The magnets stick well to the hub/can/rotor or whatever you want to call it because it is a steel ring (this enhances the overall effect of the motor rather than having them in an aluminium can).

They still need to be epoxied.

You could have experienced power loss due to the magnets becoming demagnetised from high heat...

I would epxoxy any loose magnets back in and try it out. Or buy an new one and send the old one to me! :twisted:
 
Maybe, my loss of power is actually the magnets all spinning internally and that is why during hard acceleration from a stop I was noticing a rubbing noise. When my motor got some speed going I was able to go top speed without rubbing because the magnets were strong enough not to move.

What do you think?
--------------------------
Exactly how it goes, Offroader.
 
Tench said:
This sounds to me like the magnets are all slipping around the magnet ring, when the motor gets warm the epoxy is softer and they are being driven around by the motor forces.
I see this as the only explanation that would make that noise without the wheel rotating.
Sooner or later they will smash and pile up jamming the motor completely!
Click to expand...

From page 1 of this thread, this was my first thought as the motor made that screeching sound without the wheel turning, I have heard an X5 do this too but only by applying full power with the wheel stalled, in that instance and this one the power applied is probably way beyond the design power so the manufacturing cant be blamed.
When they are being used beyond their design parameters it would make sense to do some uprating to the axles, bearings and it would seem the epoxy too.
 
I assume that the epoxy they may have used can't hold up to high heat?

When I initially had the problem was the first day I used the motor on a 90degree hot day, and definitely overheated it a lot more compared to other days.
 
This is how I measured my axle :shock: . It was within .003" or .08 millimeters.

I am not sure if you guys are going to think I was crazy to do this setup or smart. What you have to know is that the bearings are different heights. Also, if you don't clamp down on the bearings the entire strator will easily roll around, there was no easy way to rotate it unless you clamp it down.

It worked well, giving me less than .003" going around the whole strator.

 
I'll go back to what I was thinking before. I had trouble seeing how the stator was supported in your photo. If you have it supported on both sides, with 0.003" run out, then your axle is not bent, at least from the bearing journals inward.
 
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