FIXED Cromotor v2 RUB, MAGNETS came UNGLUED!

I was riding the bike today and all of a sudden after riding up some steps which I always ride up, my cromotor makes some kind of grinding noise. I think there is a slight loss of power, but it isn't a great loss of power.

I can still hit 40MPH.

It seems to do the grinding noise on hard acceleration, either at speed or stopped.

I have a video of the grinding noise it is making.

What do you think it could be or what should I check?

[youtube]ctJJpqrbCZE[/youtube]

Goto AutoZone, get a three arm puller tool, check out the inside.

Odd thing, so I took the bike out after some hours when it was completely cooled down and it stopped making the noise.

However, after a test drive it seems like there is a slight interval noise every quarter of a second, like three times in a row when I do hard acceleration. Almost sounds like a brake rub but it doesn't make the sound when I lift the back wheel off. It is a thisssss, thissss, thisss noise if that makes sense.

To me it seems like the motor is 5-10% less powerful now, but this could just be me.

I am just stumped here. I thought it may have been my controller.

What would cause that grinding noise and then when I take the bike out 4 hours later it is completely gone.

Open it and find out.

Could be broken off magnet, bad hall sensor, or bad bearing.

Opening it up isn't a bad idea. However, I read that opening it up will void the warranty. I am not sure if it is still under warranty as I bought it like 8 months ago. I will have to check this out.

Took the bike out for a short ride this morning and it didn't make any noises at all.

Then after driving for a bit or after the motor started to heat up again I heard the slight scraping sound during acceleration, it was only 1 scrape as opposed to 3. I bet if I drive longer I would get the 3 scrapes. If I then really drove it for a long time I may get the grinding again.

Something is definitely caused by the heat.

I am trying to find out about the warranty before opening it up and checking inside.

I can't watch your video right now, but the additional info your last post provided me with makes me think the stator is rubbing the magnets.

The very first hub I bought had this problem. It would be fine, but when it heated up.. something changed inside and I found that the stator was rubbing against the rotor (magnets).

http://endless-sphere.com/forums/viewtopic.php?f=2&t=47408

There was one other forum member somewhere which had this problem.
I'll take a look at the video when I get home, but I've got video and photos of my issue in my thread for you to compare against.

If that's mechanical, the motor is toast because that made noise for almost half a rotation, that does not sound like a stator hitting magnets. That sounds like a controller losing sync / bad phase connection to me. What kind of noise does it make if you lock the back wheel and give it throttle, if it makes noise, it's probably not mechanical.

What power level and controller are you running?

zombiess said:

If that's mechanical, the motor is toast because that made noise for almost half a rotation, that does not sound like a stator hitting magnets. That sounds like a controller losing sync / bad phase connection to me. What kind of noise does it make if you lock the back wheel and give it throttle, if it makes noise, it's probably not mechanical.

What power level and controller are you running?

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zombies good point about making the noise when the motor is completely stopped, as why would it be making a noise if it isn't turning and rubbing on anything. I believe it made the grinding noise when completely stopped.

I will have to see if I can get it to grind like that again by using the motor for a long time and heating it up. It doesn't do it anymore since the motor has cooled off.

To me that grinding noise I believe does sound like a phase/hall problem more than a rub. I also think I may have a very slight rub when the motor heats up but that may have always been there and I never noticed it until recently when I am looking for noises. It may be a brake/caliper rub also but I have those problems a lot and it sounds a bit different.

I'm running 72 volts 60 battery amps. Or about 4000 watts through it.

I just got my gear puller today and have not yet opened the motor but I have been thinking about what the problem may be.

I think what it could be is at first possibly one of the windings slightly rubs the side of the motor case. That is probably why I hear the slight scratching when the motor starts to heat up.

Then as the motor gets super hot it seems that possibly more of the winding wire is touching the case and it is shorting against the case and this causes the grinding noise and loss of power.

Does this make sense?

I've been following your issues with the Cromotor with much interest. Please post up some photos of what you find inside. Inquiring minds want to know!

Hugechainring said:

I've been following your issues with the Cromotor with much interest. Please post up some photos of what you find inside. Inquiring minds want to know!

Click to expand...

Sure will, I am also very interested on what I will find.

The thing is I have a feeling that I will find nothing. My reasoning is that the motor works well most of the time, so it must be pretty flawless inside.
The noise only starts when the motor is like 130c or higher and it goes away fairly quickly on cool down.

The best I can find is possibly very minor scratch marks on the case someplace. But who knows what I will find.

I had a similar noise on my X5 one day after wiring a new controller in. Sorta sounded like an ice engine revving up. Still hit good speed but seem to have lost some torque.

Turns out it was a dodgy connection on one of the phase or hall connecters. (I'm not sure wich as I unplugged and replugged them all)

You might have jostled something loose riding up the stairs and heat makes the connection worse. It is worth unplugging everything and checking the connectors before cracking the motor open.

I still didn't open the motor as it has been working OK during the cooler summer weather. I figure I won't see anything if I open it because it works normal most of the time.

However, today it hit 90 F degrees outside and I noticed when the motor was only around 120c, it had a noticeable loss of power.

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.

I am thinking it is a electrical connection issue more than a rubbing issue, that seems to be slowly getting worse.

Sounds like a bad hall or phase connection. Spin the motor by hand, any rubbing?

Loss of some power as a motor heats up is normal, but I suspect you are experiencing a much larger loss than what is normal.

Just an update, the motor got worse I think.

I was riding today and heard a slight rub in the rear. This time it was a different kind of noise, almost like the tire was rubbing against something. So I checked the bike and saw that the tire was not hitting anything.

With the bike flipped around and spinning the tire on the bike it was definitely rubbing something. The tire was also harder to turn. I looked closely and figured maybe the brakes are somehow rubbing.

I drove the bike home and took the brake caliper off the bike and that didn't do anything. The rear tire is hard to spin. It doesn't spin freely and almost seems to bind more at a certain point in the rotation. I can't see anything wrong though.

I disconnected the halls and that did not do anything.

I am not sure how freely the cromotor should spin. If I take the tire and try to spin it hard, it will only turn about 1/2 a turn before stopping. Taking the pedal and rotating it takes some force to spin the rear wheel. I tested my 1000watt golden motor and that spins much more freely. But the cromotor is bigger so maybe there is a lot more resistance?

Completely disconnect the phase wires from the controller and see if it's still hard to turn? If no, you may now have a controller problem.

Motors that lose Hall signal sync may eventually blow controller FETs and short causing the wheel hard to turn when connected to controller.

Is your controller connected to your motor when you spin the wheel? Hand spinning the wheel with the halls disconnected won't do anything but hand spinning the wheel with the phase wires disconnected might tell you if your phase wires are either shorted in the controller or the wheel. They also might be out of phase causing the over heating in the first place. Are you sure you have the proper phase wire Hall wire combo?

Disconnect the phase wires and spin the wheel again and see if it still seems to have a problem. If you are still cogging, then inspect your wires for shorts. If the wires look clean then use your multi meter to check if any of your phase wires are shorted to the axle. (one probe to a phase wire and one probe to the axle. )

Let us know how that goes.

Disconnected phase and hall wires. Doesn't make any difference, the wheel is still hard to turn.

I checked to see if phase wires were shorted to the axle and there seems to be no short.

Could a bad bearing cause this to happen? To me it feels more like something major is rubbing. I can't help but keep checking to see if the tire or motor case is somehow rubbing on something. I think I can even hear a very slight grind/rub sound.

The other thing is that even with this rubbing, I can drive and do top speed without problems. However, I am pushing 4300 watts. But this tells me if the phase or hall wires had issues I don't think this would be possible. I shorted the phase wires on my 1000 watt goldenmotor and the feel you get is kind of different, it is more uniform through the spin. This seems more like there are certain spots which seem to rub more than others. But again, it is hard to tell.

Couldn't I just short my phase wires and see how it feels with them shorted? I don't know if this is safe or not, but it would rule out a shorting of the phase wires.

I guess I'm going to have to open it up at this point as I can't drive it like this. What ever is causing is most likely going to put a lot more strain on the motor. when I pedal with my hand with the wheel upside down I have to put a surprising amount of force to turn the wheel.

If I pedal the bike as fast as I can with my hands and stop, the wheel will only spin maybe a couple of times than stop suddenly. I really don't know how easily or freely the cromotor spins normally as I never messed with it because my bike is over 115lbs.

What I find interesting is that the motor seems to have a lot of issues, I would think they are all related here but I just do not know. I had some scratching sound at the beginning of my troubles but that sound is gone. This problem today is different than my original grinding sound.

Just pull it apart already! Sounds like you've definitely got mechanical issues if with everything disconnected you're still finding it difficult to turn by hand. You're only going to do more damage by continuing to ride with it hurt.

Yeah! We want carnage!
Post photos of anything suspect. There's been much speculation already. Go for the gear puller. It's certainly not going to get better without some attention.

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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!

So I finally opened the motor.

It looks like obvious rubbing on all of the magnets. There was also fine dust on the magnets and the stator where the rubbing would have taken place.

What I found to be interesting is the side cover that holds the freewheel. I saw on another thread that someone had the same issue, it looks to be stress cracks inside the cover?

I wish I had another cromotor to compare it to.

This is the only conclusive damage I could find, but will a few cracks really cause all these issues? The side covers still feel solid.



Please look at my pictures and let me know what you think, you can click on the picture and blow it up and to look at more as I took 22 pictures in total. Please let me know what you think and is this fixable?

How would I go about fixing this?







Does that look like stress cracks in the case or was that part of the manufacturing?


The magnets looked scratched up, how bad does it look?




Metal filings between the laminations, can this cause a short and be a problem?


This side cover looks fine with no cracks.

I can't tell if it's oval, but damn those are some serious cracks.