SmartPie bearing play

[rcnicke]

Hello,

Trying to tighten the spokes the other day, to get a straight wheel, I realized that the problem was not the spokes.

There was a play in the bearings, in the "B" direction as shown in this post: http://goldenmotor.com/SMF/index.php?topic=4525.msg26150#msg26150

When I had the SM opened up for other reasons (http://goldenmotor.com/SMF/index.php?topic=4636.0), I cecked and noticed that the large bearing had about 0,8 degrees of play.

Even with the covers and the small bearing on, this was enough to make noticable play on the wheel.

I could only remove the motor covering on the stator side of the motor. The covering on the controller side of the motor won't come off, even with all the bolts removed. I also don't know how to remove the circlip without damaging it.
So my problems are:

1. How do I remove the controller-side motor covering?
2. How do I remove the circlip without damaging it?
3. What Do I do about the bearing?

[Bikemad]

1. How do I remove the controller-side motor covering?
2. How do I remove the circlip without damaging it?
3. What Do I do about the bearing?

1) I suspect the cover will be stuck with silicone sealant around the outer edge, like the opposite side was, but it may also be bonded to the outer race of the bearing using some form of locking compound to eliminate movement. It may be possible to remove the cover from the bearing by gently tapping around the end of the tubular section that fits over the bearing with a hammer and a soft drift inserted between the stator spokes from the other side, but this could actually cause damage to the bearing (known as burnelling) through the impact forces being transmitted through a very small surface area where the balls contact the inner and outer races.
Unless you are prepared to spend an absolute fortune on a very high quality replacement bearing, I recommend you do not disturb the bearing that is already fitted.

2) There is no need to remove the circlip as it is only fitted to ensure the stator can't move sideways along the axle.

3) Most single ball race bearings will have some amount of sideways twisting movement, but as the two bearings on the Smart Pie are fitted very close to each other on the axle, this slight amount of movement in the bearings will be significantly exaggerated when observed at the rim.
It is common engineering practice to eliminate bearing movement by applying a small amount of sideways force to preload the bearings:



GM use a wavy spring washer to eliminate any end play and compensate for slight differences in the machining process of the individual components, but if you apply a small amount of sideways force to the rim, the washer will simply compress.

Replacing this wavy washer with a solid washer of the correct thickness should remove most of the play under normal loads, although if enough load is exerted, the side covers will probably flex enough to allow the movement to become visible again.
If the washer used is too thick, the preload on the bearings can be excessive, causing the bearings to wear out much quicker than normal. 

I have noticeable movement on both my MPIII and my Smart Pie which has been there from new, but it is not enough to allow contact between any of the stationary and moving parts (the stator and magnets or the windings and the covers etc.) and it does not affect the operation of the wheel. If the play becomes bad enough to cause concern, I will rectify the problem then, but I am reluctant to pull it apart until I need to do so.

You know what they say, "If it ain't broke, don't fix it"!

Alan
 

[rcnicke]

Thanks for your thorough answer, Alan

1. Yeah, it might be stuck with silicone sealant, although there was no such thing on the other side.
2. Ok. Unless I wanted to remove the axle from the stator, which on second thought, I guess I don't.
3. Ok, I'll just accept the play as long as the stator and magnets don't rub. Noticed the wavy clips, had two of them.

I guess it ain't broke then. Good to hear!

Niklas

[thomab]

Hi,

I also have significant play on my bearings, I also have the SmartPie.

I'm almost certain I checked for play when I first received my SmartPie, and then it was fine.
After a couple of days my SmartPie broke down (see http://goldenmotor.com/SMF/index.php?topic=4604.15), and when I
finally fixed the problem and fitted the same wheel, I noticed the play. So I have a feeling that this problem occurred after some
biking time.

I'm not sure how big of a deal it is, but it is not very reassuring, and certainly would put more load on the bearings over time?
I tried to fix it, but was unsuccessful (don't have the right tools), so at the end of the day I mounted the wheel with the play anyway.

The bike works fine for now, hope it will continue this way

[Lollandster]

I just wanted to share my experience with bearing play too.
Thomab actually explains my situation almost down to the letter. There was no significant play when the motor was new, but now after a couple of months use there is significant play. I too had to open the motor (three times now because of breakdowns), but I don't think it is related.

The play on the motor is big enough that I feel it when riding. It also makes a audible "glonk" sound on every revolution. I managed to replicate this sound with the wheel off the bike by turning the axle so I know it is inside the wheel.

I made a short video trying to capture the movement. It is much more visible in real life, but if you look closely you can see what I am talking about. The force I'm applying to the side of the rim with my thumb at the end of the video is virtually nothing, I'm not forcing it sideways.
http://youtu.be/TnuJAHzQNus

For now I'm going to follow Bikemads tip: "If it ain't broke, don't fix it"

[Morgen 3Eman]

Hi Lollandster,

The play you are seeing is what I would expect from grade 100  bearings, or a size mismatch of the bearing to the seating surfaces.  By that I mean the bearing is loose on the shaft or in its housing. Sizing errors can be economically corrected by shimming or using bonding agents.  Layers of super glue are commonly used to snug up bearing clearances.

Regarding "if it ain'tbroke....., (Which I believe in)  : would you drive your car with a wheel that wobbled that much? 

I think buying grade 5-10 bearings will be much less costly than the medical bills from your crash. 

I'll shut up now. 

TTFN,
Dennis

[Lollandster]

Its free medical here in Norway so thats not going to cost, but still...
If this might turn in to a potential hospital visit then I'm all about fixing it. Could you give me some more information on where I may find this mismatched bearing?

[rcnicke]

The play on the motor is big enough that I feel it when riding. It also makes a audible "glonk" sound on every revolution. I managed to replicate this sound with the wheel off the bike by turning the axle so I know it is inside the wheel.

That's is the exact behavior of mine too, down to the "glonk" sound. Definately noticable when riding. I actually think the brake pads more or less keeps the thing in place when a too big side force is applied. I'd also be intrerested in where to find higher grade replacements bearings.

[Morgen 3Eman]

Hi Lollandster

All I can suggest is to closely observe the movement to find out where it occurs.   With the movement I saw on the video, it seems it would be a very large and easy to find.  I have no idea what you will have to do to get a clear view of the bearing,  but once you can see inner and outer races, you can determine if the inner and outer races are moving relative to each other, or if the inner bearing race is moving relative to the shaft, or if the outer race is moving in its seating area. 

Could the "glonk" be the stator rubbing against the rotor at one spot?  It sure looks like the whole assembly is out of round or not concentric.  It also looks like the movement is in the smaller diameter bearing, which if true would mean the bearing would be less expensive.

As far as gettting replacement bearings, I must admit that I have no experience in buying bearings in Norway.  But in the US, I just shop online at a local bearing distributor web site.  They have pricing for differing grades so I can determine the cost/value of a particular selection.  If you get access to the bearing, you should see a part number etched into it, and that will be what you need to get an exact replacement.

I hope I was helpful.

TTFN,
Dennis

[Lollandster]

I opened up the wheel trying to find the corporate. I even made a video of it.
I found the bad bearing and it's all bad news.

The bad bearing was the biggest one marked 6812RS my local distributor had a the bearing (the european number is 61812), but they wanted ~1200NOK (~200USD) for that one bearing.
The "glonk" noise was as you suspected, Dennis, the stator rubbing against the rotor. It was actually one of the hall sensors that hit the magnet ring. This means that unless I do something about the problem something might break. I think that ball bearing is going to get even worse if I don't replace it.

EDIT: There is actually a whole lot of play in the small 6202RS bearing too. I need to replace them both.

I ordered some cheap bearings from ebay to save money. They probably won't last long, but what am I to do? 6812 2RS and 6202 2RS

[Morgen 3Eman]

I took a look at the web, and in the US that 6812 bearing is available for about $25!

With the amount of play I saw in your video, there must be a ball missing in the assembly. 

I just cannot understand why GM keeps ruining their brilliant design work by using  such low quality components and workmanship.  They seem eager to keep screwing us to cut build cost by pennies, while not recognizing the huge dollar value a reputation for high quality brings.  Is it possible that  GM actually stands for Ghastly Management?  General Motors used to go by that moniker.  Come to think of it, they too had gorgeous designs compromised by horrible build quality.  I loved driving my Cadillac, but came to hate owning it because of all the build quality related problems. 

Good luck with your Pie rebuild.  Please keep us posted on your progress.

TTFN,
Dennis

[atcspaul]

great video lollandster. would also like to see more of how you get old bearings out and new in when you replace them.

[Andlier]

I'm yet another Smart Pie customer from Norway :-) I can tell you that I too have the bearing play that is discussed in this topic. I noticed it when I first assembled the bike and it has been the same since. The play has not increased noticeably over the 300-400 km I've been using the Smart Pie, at least not that I can tell. If it turns out that the bearings are of low quality I really hope that golden motor take actions to fix this in new Smart Pies. And also that they are willing to send out replacement bearings to Smart Pie customers that has problems with bearing play (given the high price when purchasing single high quality bearings locally).

[Lollandster]

I'm yet another Smart Pie customer from Norway :-)

We are not few. I can count 8: daijulie, jan-norway, Cornelius, karen, havard Samotholt, you and me. Probably mostly MagicPies since the SmartPie is so new, but there is no denying the popularity GoldenMotor has in Norway.

I can tell you that I too have the bearing play that is discussed in this topic. I noticed it when I first assembled the bike and it has been the same since. The play has not increased noticeably over the 300-400 km I've been using the Smart Pie, at least not that I can tell. If it turns out that the bearings are of low quality I really hope that golden motor take actions to fix this in new Smart Pies. And also that they are willing to send out replacement bearings to Smart Pie customers that has problems with bearing play (given the high price when purchasing single high quality bearings locally).

I hope so too, but I wouldn't hold my breath. I'll let you know if the new bearings I ordered fix the problem. The small one I ordered looks nice and comes from USA, but the big one is Chinese and probably not much better than the original. I'll have to wait and see.

[Lollandster]

I received the bearings today. Changing them wasn't very hard at all, the bearing had plenty of tolerance and could easily be knocked out with a hammer, no need for a hydraulic press. The new bearings went in just as easily. Unfortunately the difference between the new bearings and the old ones was minimal. The knocking sound disappeared and the play was reduced, but there was some play. I also took Alans advice and installed a solid washer to give the bearing additional preload. I didn't find a washer in the right size, but I made one from a 1mm lead sheet I had (soft enough to cut with normal scissors). That extra washer offset my wheel slightly (about 0.5mm) so I had to adjust the break caliper. Now the play is less than when the SmartPie was new. I haven't tried it on the road yet, but I believe the small play that's left wont be noticeable.