NOT hub motor bearings - corrosion inside motor... need help

[DarthSensate]

My year and a half old GM motor seems to have really slow bearings. I noted this when I was installing it last year and assumed that this was just cogging or some other drag from the magnets and coils in the motor. It was completely usable at the time and I rode it for a year with no trouble.

Now the bike is on my bench and when I spin the front wheel it struggles to make a complete rotation. The rotation is smooth but there is a A LOT of drag. (The brakes are not rubbing) It reminds me of in-line skates from wally world with ABEC 1-3 VS. ABEC 9 bearings.

I was always dissatisfied with the bearings and would now like to open the motor and press the bearings out and replace them.

Please advise. I need to know how to identify or measure the bearings in this motor and order matching bearings with high grade bearings.

Thanks for your assistance.


(EDIT: subject changed. I originally thought that the issue was bearings but later found that there was significant corrosion inside the motor housing affecting tollerances between the magnets and stator arms.)

 

[TPA]

You need three dimensions to order bearings.

1. The outside diameter
2. The inside diameter
3. The thickness

Bearings are typically made so that each of these three dimensions fall exactly on a nice round number.

for metric that means the od might be 25mm for example and the id might be, say 8mm and the thickness 8mm. All you need to do is measure with something that gets reasonably close, and you can assume that if it looks like it might measure 25mm, then it probably is.

Then you go to a place that sells high quality bearings like boca or acer and locate a bearing of that same size.

 

[dnmun]

you will need a bearing puller to get it off the shaft and a press with the long sleeve to press a new one on. do you have the skills? if you can do that, then after you get it off, take it to a bearing shop and they will know what it is. bearing have universal size numbers on the seal usually.

if you aren't familar with them and don't have a long puller, then call around to various machine shops or even farm implement repair guys, sometimes there are rebuild shops for alternators and starters who would be able to do it too.

bearings don't usually get tighter with wear, they get looser. so if yours is tighter, maybe just pulling the seal off and squeezing some grease in might help without replacing it. be gentle with the seal, use a sharp pin hook pick to reach between the seal and the axle to get behind it to pull it off. you don't wanna tear up the seal.

 

[spinningmagnets]

You may need to rent a bearing puller. I've actually very carefully destroyed bearings to remove them with a diamond-point chisel working from the ID edge towards the center.

And when you re-install the new ones (depending on many factors) it "may" be helpful to heat up the hub and chill the bearing before trying to press them together.

 

[DarthSensate]

Thank you for the info.

Searching GM's forums, it looks like their hub motors use "common" 6202 skate/scooter bearings. ( BORE 15MM, OD 35MM, WIDTH 11MM )

I intend to check this out by direct by measurement, but, if they are, do any of you have experience with 6202 skate bearings in terms of durability and reliability? brand names?

 

[dnmun]

if you are asking these questions, and thinking it is a skateboard bearing, you need to take it to someone who can tell if they really are bad bearings.

 

[DarthSensate]

if you are asking these questions, and thinking it is a skateboard bearing, you need to take it to someone who can tell if they really are bad bearings.

I already stated I was going to verify the bearings directly. I've seen plenty of garbage bearings that are not worn out show the same high rolling resistance.
I HATE it when threads are abandoned before resolution. Forums are for sharing information. So I am posting what I find as I find it and would welcome further discussion. Hopefully I will learn from those who have already experienced similar situations.

Correction to my previous post. I think I wrote 6062 bearings instead of the correct number, 6202. If anyone has any good experience with durable bearing manufacturers or brands, I would love to hear it. I would trust a consensus on this forum over some guy at a skate shop anyday.

 

[TPA]

You can get those bearings for very cheap...like less than $1 each but you will end up the same way. The opposite end of that spectrum is full ceramic bearings for $60 each.

A good compromise is the hybrid bearing like these at $25 each:

http://www.vxb.com/page/bearings/PROD/AB/Kit7546

I have not personally used them so maybe someone else can chime in there.

 

[Ypedal]

Most chinese hub motors are " loose fit " extreemely sloppy fitting bearings, a few taps and they drop off like flies. on rare occasions i've had to use a gear puller to yank one off but they usually stay in the motor covers and you can wack them out using a proper size socket. Getting them back on is also easy, find a nice flat piece of something and hammer them in flat and straight ( take your time getting them started in the right way, if they are not parallel pop them out and start again.. if you wedge one in wrong it's a PITA to get them out.

no fancy tools or machine shop required for 90 % of hubs i've taken apart ( like.. dozens of them )

 

[Chris_Faherty]

I've replaced bearings on a Chrystalyte 5 series hub. It may be similar to your hub. It is done with only removing the covers.

Here's how I do it (for Chrystalyte hub)..

1) Remove cover screws from both covers.
2) Support the wheel flat on top of an open 5 gal bucket or tire changing stand.
3) Tap axle with a plastic hammer or piece of wood & hammer. Careful not to damage the end. You just need to break the sealant seal on the opposite cover. Flip over and do the other cover's seal. You just need to tap until you get 1/8" or so of gap.
4) Carefully and evenly pry a cover off. Take care to not damage any wiring.

Avoid removing the motor guts. Very strong magnets and you can easily crush fingers if you are not using a fixture.

The bearing can be easily removed with a puller. I use this one http://pitposse.com/whbereset.html which is a kit containing several size collets. You can find this type in many places. Probably cycle gear has it, or you can get a smaller set with fewer collets.

I suggest you go to a local bearing shop to get quality bearings. They can help you choose a set to make you happy. Personally I went with a Chinese set which is distributed in the USA under the brand Peer. The bearing shop convinced me that it was a decent bearing, and it's also inexpensive.

I went with a 2RS double sealed bearing. This has more drag than an unsealed or shielded bearing. You may go with a shielded bearing if you want less drag.

Anyways back to the steps.

5) Pop out the bearing. Press or tap in new bearing. One of my covers had a loose fit with the bearing, as the original bearing showed signs of spinning. I chose to use Loctite retaining compound for my bearing to cover interface. This also is available at a bearing shop.

6) Clean up old sealant. For sealant I use "The Right Stuff" which is a Permatex product. Its an RTV with some rubber mixed in, and good for high temperatures. It is pretty strong for an RTV and it gives you a lot of working time. I just smear it on very thin to the hub surface.

7) Put the covers back on one side at a time. Line up the screw holes and seat it evenly. Torque the screws appropriately for that fastener size.

 

[Reid Welch]

The answers have been given already. Have just now come across this thread.
Have relatively little pracical experience re: ball bearing replacement.

Have, however, a fun story of "KYYADAWYADI".


ca. 1975. Rebuilding a ca. 1923 Duo Art reproducing piano's air pump.
Its four pump arms use a total number of eight ball bearing, a quality feature of the time (so they thought),
that would give super service, better than plain bearings made of graphite-greased piano bushing cloth (which are dead silent.

Silence and free-running are the requisite in a reproducer piano pump. No thumps or "rrrr-rrrr" sounds are wanted.

The Duo-Art bearings, even after careful cleaning and greasing, made a rolling-ball kind of noise. Old and not that quiet from day one.
"New Departure" brand or some such. Obsolete part numbers. Take samples to local bearing shop. "Man, these are wierd shite!
Use these from the size-equivalent book. Expensive bearings of several buck per copy (costly for then".

They were of the type called "self aligning bearings" That is, an "SA" bearing can gimbal slightly for use in particular applications where the shaft and journal do not run square, all of the time (which condition obtains in a Duo-Art player pump.

Installation, no problem. Service: bearings were quiet but failed within a few hours of operation. Sounded like a coffee mill.

Replaced bearings two more times with the same TYPE, but differing brands. Same coffee mill noises soon resulted.

Cause of the trouble? SA bearings cannot take any degree of end thrust for very long before they begin to go South.
The D-A pump, by nature was a reciprocating pump of four bellows. The bearings were simple pivots. These SA bearings,
unlike the loose cup and cone original bearings, which, -probably were never all that silent, would start out perfectly quiet enough.
Then their gimabaling action, in the actual service of pumping action, soon failed in god awful ways of groans and squeaks.

Fix: replace again with a NON self aligning modern bearing of the same shaft OD and hole OD as per original, but full-filled races
and not loose balls in screw-cap cups. The pump worked quietly and lasted, so far as I know, to this day.

Moral learned: replace like with like when possible. Quality does count, but even more so: use a type that the maker knows can give service.
The higher the quality the bearing, in general, the better service life.

The venerable cup and cone bearing which we do not see in hub motors, remains, in my opinion,
the ideal bearing for general bicycle work. They will last and last, if kept clean and greased,
and, usually, have no "seals" to make any drag, and can be pumped-trough with fresh oil or grease to eject
water and grit: two of the three main causes of bearing death.

General crapola trivia: Plain bearings are the only silent bearings.
Plain bearings require to be self aligning, or to be factory line-reamed just so.
Plain bearings do not wear out.
There is a reason why crankshaft main bearings used to be almost never ever of the ball or roller type.
What is that technical reason?

Ball bearings rock. They roll. They are good and often mandated for bike hubs (though the first bikes used plain-pain bearings.

Nothing is new. Everything but a properly fitted and ideally operated plain bearing, eventually dies.
there is about no more severe service for a ball bearing than what we get when we have, as we must, ball bearings
in a hub motor. Cheap chinese bearings are cheap. Agreed: a brand name that's known to be reliable is always worth the extra cost.

Never forget Aunt Barbara's advice re: luncheon loaf: "You get what you pay for".

And keep away from Duo-Art suction pumps. They are not nice to work on, over and over and over again.

 

[DarthSensate]

Thank you very much for all of your information!
Very informative. I love the story of the bearing issues on the piano air pumps. You can't get enough personal experience stories to really arrive at an understanding of technology, or anything for that matter. And that was a beautifully detailed description! Was that your experience or siting someone elses?

I removed the bolts from the plates on the motor housing.
I was able to spin each plate on the bearings without completely removing the plate from the motor. They spun perfectly with no slop. There was not significant drag when the plates were spinning free of the motor housing. So, I think the bearings are just fine.

I reassembled the motor and spun it by hand out of the forks, and noticed that the drag had re-appeared. I placed the wheel in the forks loose and slowly turned the wheel through 360 degrees. There was a noticeable very soft scrapping noise from ~270-360 degrees of rotation and HUGE friction on the wheel at this point.

So I need to actually pull the plates and inspect the rotor for issues.
Any thoughts on what I should look for that would cause drag only on one quarter of a full rotation?

As always, thank you for any advise you may have.

 

[dnmun]

magnets are rubbing on the stator.

 

[DarthSensate]

magnets are rubbing on the stator.

That's what I was guessing, but wouldn't the stator have to be deformed as well for it to ONLY rub at one spot in the rotation? Otherwise the friction should be uniform around the full rotation of the stator?

 

[dnmun]

i figured if the bearing is gone, then it torques over under the magnet's strength and binds up. you will see scratches on the magnet when you open it if that is the case. hopefully they aren't loose.

 

[Chris_Faherty]

I usually inspect bearings for any play by trying to rock the inner race. If I feel any play at all I swap them out. Though have you tried wiggling the mounted wheel to check for play? If the play is bad enough to cause binding, it surely would be noticeable by wiggling the mounted wheel side to side.

Just want to be sure to emphasize again to be very careful when installing the stator into the hub. Be sure to never get yourself (fingers etc) in between the stator and magnets as they will attract with incredible force.

 

[DarthSensate]

I'll check the bearings again. But there was no slop in them when I was spinning the plates back four posts ago. The bearings appeared to be spinning freely and solid.

 

[DarthSensate]

Pulled the plates completely off the bearings this time.

There is serious surface corrosion around the entire hub coating all the magnets.
The surface of the stator arms don't look good either.
The corrosion appear to radiate out from the axle. I'm guessing more moisture than I would have guessed got in through the axle.

What can I use to clean/disolve the magnets and stator? Naval jelly, PB Blaster or Liquid Wrench and a clean cloth? The motor still runs but I am guessing the corrosion is causing the increased friction; the bearings themselves still seam fine.

What SHOULD I have been doing to prevent this damage?

 

[icecube57]

Have you tried turning the and screwing it down in a different spot? I had to mark my motor after I heard a weird noise after my temp probe project. (a butt splice fount itself in the motor and it was scraping) Magnet pulled it in there. I gave the motor cover a turn until all the screw holes lined up perfectly straight without an angle and torqued it down and presto it spun like a champ. If any of your screws are going in slanted thet will be a good indication that the cover isnt seating correctly.

 

[DarthSensate]

Have you tried turning the and screwing it down in a different spot? I had to mark my motor after I heard a weird noise after my temp probe project. (a butt splice fount itself in the motor and it was scraping) Magnet pulled it in there. I gave the motor cover a turn until all the screw holes lined up perfectly straight without an angle and torqued it down and presto it spun like a champ. If any of your screws are going in slanted thet will be a good indication that the cover isnt seating correctly.

I'll make sure I follow that procedure when I reassemble it.

I cleaned the magnets and outside surface of the stator with Naval Jelly. They are nice and smooth now.
The motor sat all winter on the bike in my garage and it appears that condensation must have collected inside the motor and caused corrosion on the lower portion of the stator. The magnets had a significant rough spot/ridge of corrosion where I am guessing they sat in proximity to the bottom end of the stator. This explains why the friction was only present through ~90 degrees of rotation.
Hope fully I haven't damaged the wiring and this clears the problem.

How do I prevent this kind corrosion in the future?

Is there something I can coat the stator and magnets with to shield from water? Machine oil? Wax like used on wood shop power equipment?

 

[icecube57]

I was wondering the same thing. I noticed that my GM doesnt have any varnish on the windings. But it doesn seem to have melted off either. Its not collected or slung anywhere. I do smell it. I just dont see it. My windings arent charred,dull brown or crusty. Thank God! I wonder is this something I should worry about. The windings should have thin insulation on the wires itself. Maybe thats enough. But Its defintely nothing like the X% where it looks gooped on like a blind man painted it on.

 

[DarthSensate]

A couple thoughts came up here at work with my fellow technogeeks and motor heads...

Packing the inside of the stator with dessicant packs and a retaining wire to hold the packs in place???

Coating the stator and hub wall with "Slick50" or equivalent and running the motor to temperature for 30 minutes???

I am going to at least use forma-gasket around the plates and bolt holes and then pack the bearings with a lot of bearing grease this time.

 

[TPA]

There are products, such as rust ban, that spray or brush on like oil then dry to a slightly tacky finish. It can be easily be removed if it does not work. I do not know if it is electrically conductive.

 

[DarthSensate]

There are products, such as rust ban

I checked on the Exxon site for Rust Ban 343 and 392.
http://www.exxon.com/USA-English/Lubes/PDS/NAUSENINDEXRust-Ban_343_392.asp
Flash point is 190 and 71 degrees Celsius respectively. The temperature range for 343 looks good for use in the motor without a spark igniting the material.
I couldn't find any specs on conductivity for it though.

There seems to be some favorable properties for light machine/sewing machine oil inside electric motors as lubrication and rust inhibitor. Can anyone vouch for light machine oil in a 500W motor?

 

[dnmun]

the water came in through where the axle bearing is. on the 9 continentsmotors i got from jason at ebikekit.com there is a seal on the axle to keep water out of the hub. the goldenmotor and the rayben and aotema did not have the axle seal.

the motor will get hot enuff when in use to keep it dry, maybe. i doubt if it was just condensation. a reason to ride year round, keep it hot and dry.

don't spray anything in there because it may damage the varnish or the hall sensors. nothing loose like desiccants either, and make sure the magnets don't secretly pick up a small piece of metal while you have it open. that is bad.