Bearings quality

macribs

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Jul 22, 2014
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Yesterday I met an overly excited kid when I got home, he had just gotten new bearings for his inlines.
When he spun the tiny wheels they just seemed to roll forever. He didn't remember the specs he got his from a friends internet bargain.
It was some special coating, or super smooth steel balls(?) inside. Didn't pay all that much attention really.

But it got me thinking, I've grown up with SKF bearings. From Sweden. Those went anywhere a bearing was needed. Now I realize it was probably most out of convenience more then anything else. Those where easy to buy. And you would always find the right size and price.

Are there any bearings manufacturer that stands out today? I mean for bigger bearings then to use on inlines for kids?
Have there been much milestones in the technology of bearings that past two decades? Who are the go to guys for bearings of highest quality for our e-bikes needs?

And would any of you know of bearings with a 100% tight seal that could prevent liquid to enter or exit via bearings?
 
Don't even think about putting oil in one of our motors. With the tight space tolerance the spinning flow is sure to erode and mess up the hall board. I thought you wanted/needed to run significant power anyway. The guys running oil are cyclist weight types only running modest power, which is why they haven't come to the realization that the exterior shell is too much of a heat bottleneck to leave unaddressed....but what do I know, I only run 27kw through my hubmotor.
 
Kiriakos GR said:
I've grown up too with SKF bearings, but in the latest years I lost faith that they are quality items, as I got signs of premature wear and actually two times.

By making the change at using KOYO / Japan, I did rediscover the sense of reliability in out times.
In my applications I am using sealed ones, which translates that lubrication stays on all the time, and therefore any premature damage is proof of poor manufacturing process or poor in quality metals.


Yeah my problem is that I haven't really been building, rebuilding or doing any service work work myself for some years due to real life, family and work situation. Barely had time to ride, and had no time in the garage. So I am afraid I am really outdated on the bearing part. And as found as I am of search engines, finding quality parts via them ain't easy - as almost every single manufacturer will claim they are the new wine, have some special edge or are just brilliant. So I think better to ask here, as here are a vast amount of expertise, experience and updated people, engineers, mechanical and technical gifted people and fellow enthusiasts.

When my son spun his new wheel of his new inline versus the old one the time before the new wheel stopped was so long it just felt that the new bearings made the tiny wheel spin forever. Of course it might be that any new bearing would be much better then the old ones, but he claimed that there was something special about them. And me being an old dude, outdated on more fields then I like to admit I really don't know for sure. So better to ask.


John In CR said:
Don't even think about putting oil in one of our motors. With the tight space tolerance the spinning flow is sure to erode and mess up the hall board. I thought you wanted/needed to run significant power anyway. The guys running oil are cyclist weight types only running modest power, which is why they haven't come to the realization that the exterior shell is too much of a heat bottleneck to leave unaddressed....but what do I know, I only run 27kw through my hubmotor.

Yes to big power, no to tiny rider weight or modest power. :D
I am still very much battling with the best possible solution for cooling - as there is a few steep and long hills here. But it seems other then various versions of liquid cooling, effective cooling will add even more masses, or remove critical masses [air vented covers] - which I think is real bad for our wet summers, salt water sprayed winter roads and general harsh weather. I am thinking getting motor soaked in salt water spraying/hosing down the bike in winter conditions that would be the worst possible scenario for motor to survive. And if there ever is anything Norwegian do excel in, it is spraying down winter roads with salt water to avoid icy roads.
[completely ignoring the massive corrosive attacks on vehicle caused by the salt water]

So I am still battling with oil filled, water cooled like Linukas does or trying out oil submerge/partly submerged motor. Think covering the halls with epoxy of some sort would work?
 
Are they ceramic bearings?
Steel is soft enough to create rolling resistance as the balls deform like a tyre, when compared to ceramic. It is so much tougher that you get a smaller contact area without this deformation.

The lubricants used also make a big difference. A good wedge of grease is never going to be as free flowing as a ptfe based liquid lubricant.

I can take the cheapest of bearings and make them run like the best by cleaning them out and using liquid lubes. Service intervals shorten but having to tap the brakes to stop catching up the lycra's freewheeling down hills tells me everything.

I used to recon many bearings, working as a lucas service agent. The best bearing was a lightly oiled one, but we had to pack them with grease as it forms a physical barrier to dirt ingress.


Don't try this at home:
Take a sealed bearing and pop the covers off. Degrease fully. Add a light liquid lube. Now hold the bearing by pinching the middle tube, and taking an airline to the balls you can get the bearing spinning in your hands. Greased won't do this at all. The bearing should spin up with a sound like a jet about to take off. They fully weight up in your hand, making moving them about difficult. Then you drop them..... Much wheel spinning and sparks follow as the outer race grinds away looking for grip. Then they leave at a great pace... But only after practicing with the best oils. We found silicone spray adequate, but ptfe is so smooth even a gecko can't hold on to the stuff.
 
Ceramic bearings? What do you know - I am old :D
Never heard of ceramic bearings, will they withstand abuse from a fat ass riders - wouldn't like em ceramic rollers to turn to dust due to rider weight issues ;)
What you reckon life span would be compared to steel rollers?
Half the life time? How are those ceramic bearings priced compared to steel?
Easy to find ceramic bearings in all possible sizes?

Will do some reading about the ptfe lubrication tonite. Never crossed my mind to use anything else then proper gooey grease.
Can ptfe be added to all types of closed bearings, and if so what is the expected life time reduced by?
 
Bearings are a durability issue, not an efficiency issue. A bearing would have to be totally destroyed to cause a speed or efficiency difference detectable even by sensitive instruments. Dissipate even a watt or two into a bearing and it will get pretty warm. In practice, they never do unless they're grossly overtightened.

The time it takes for a wheel to spin down after having a joule or so of energy imparted to it to spin it up is not meaningful to a bicycle's performance, even if a very slick-running bearing is aesthetically satisfying. It just doesn't matter. In the real world, bearing seals are more important than bearing drag, and effective seals cause drag. Good bearings are those that last a long time in their operating conditions, not the ones that spin most freely.

Look at it this way: If you're losing a kilowatt to aero drag, 200W to rolling resistance, and 5 watts to all the bearings in your bike combined, what technical enhancements deserve your attention? If you want to conserve small amounts of power easily, check your tire pressure before every ride, or tuck your pants into your socks. The difference between awful bearings and excellent bearings is only a fraction of a negligible amount of your total power budget.

If you use knobby tires, that's a much bigger energy sink. If you use thick tubes or any kind of tire liners, that's a much bigger energy sink. If you ride in loose-fitting clothing, that's a much bigger energy sink. If you have suspension, that's a much bigger energy sink. If you use an 11 tooth sprocket, even that's a much bigger energy sink. Don't fuss over the bearings; just make sure they are copiously lubricated and correctly adjusted.
 
Well pointed out chalo. It is too easy to get caught up in the little things.
I guess me loosing 40 lbs of dead weight will add significantly more impact to efficiency then any other minor tweaks. :mrgreen:
But it is easier to hunt for the solutions that will let us carry on without sacrifices.

Still this video will make your head spin.[/pun]

[youtube]q4Tc1U1Tg34[/youtube]
 
Ceramic bearings hit the bike market with far-fetched claims a few years ago. To make them seem to live up to the hype, the manufacturers fit them with looser-running, less effective seals. That's the whole observable difference, and a pretty cynical ploy in my opinion.

I have a road bike with 1980s Sachs drum brake hubs that have labyrinth (non-contact) seals on the bearings. When that bike is in the work stand, even a small fan running across the workshop will get the wheels spinning. The bearings are regular cup and cone type with 1/4" balls and grease lubrication.
 
Macribs,

Build yourself a pair of Lebowski controllers for high quality sensorless operation, and then you can forget about the only fragile things in a hubbie, the hall legs and their wiring. Then double the surface area of the outer shell and add blades to increase the velocity and flow over the outer surfaces. Add some ridges to the interior to ensure the oil will spin up well and coat the stator with only a 1/3rd fill for very minor oil drips from a tiny weep hole and tube, which is necessary to relieve pressure and vacuum from temp changes that would otherwise force the oil out even through the wiring.

Forget other forms of liquid cooling, because they don't get the liquid close enough to the source of the heat, and the temperatures are so much lower than in an ICE. Sure it can move extra heat, but it's simply not worth the trouble, because it only benefits continuous operation and protects the motor very little from short spikes in temperature at the copper. Simply adding significant surface area to the shell inside and out offers the similar improvement without the complexity or weight, while still keeping the motor sealed, and without the complexity or weight.

Personally, for an all weather all terrain bike I'll get the motor out of the wheel. The potential power of our motors can't truly be unleashed when limited to wheel rpm anyway. I'd add an extra layer of protective coating to the stator and really open the motor up for tremendous air flow using my bladed approach. Then fab a fiberglass housing with a screened and filtered air intake positioned to minimize road spray and debris getting to it, but gain some positive pressure from an air dam. The output port of the housing would look similar to any centrifugal fan, and would point down and rearward so the exterior air flow compliments the fan output. This would make the motor also a full fledged centrifugal fan, and the hundreds of cfm of high velocity turbulent flow directly where it is needed flowing through the motor will keep it nice and cool while protecting it from anything short of full submersion.
 
I love cup and cone. Sealed just don't do it for me. An open cup and cone can be washed out easily with a spray can of lube, and the amount of binding controlled throughout the bearings life with careful adjustment. Which is far too much trouble compared to sealed alternatives, but I do enjoy it, so it is worthwhile. You don't need specialist equipment to tell the difference when I service bearings.

I can't think of the last time I bought a cup and cone item that was not overtightened at factory. Generally killing them. Which is the most common reason I use for returning new bikes.

Pedals let me down. Is there a special tool to hold the cone while I nip the locknut? From new they always need a service, and are nipped up well. I end up needing threadlock to reassemble them though. So just got some sealed bearing pedals. Which with that bikes sealed BB requires far to much effort to just turn the crank. If I add the sealed bearing idle gears to my derailleur I don't think I will be able to live with it. There will be drag equal to the power required to move the bike if I have 11 sealed bearings in the drive train.


I don't suggest people remove the covers and wash out the grease with pfte spray, but I don't suggest they don't either. On a non-assisted bike I do it every time. The video posted says it all.

You can buy ceramic bearings loose to fit to your own cup&cone bikes, but just getting it right with normal steel balls is good enough for me.
 
Chalo has hit the nail on the head.

It's a low-performance electric motor, not a scanning electron microscope or gas turbine. Bog-standard industrial bearings of good quality are what's required. Precision or ceramic aren't.

Ceramic bearings can operate at higher speed (around 15%) than steel balls due to their lower mass, but the increased stiffness of the balls puts more stress on the races, reducing load capacity.

As far as I know, no common bearing shield is intended to be provide an oil-tight seal, which is a shame. However, shields rated to prevent ingress in harsh environments ought to do better than most at stopping oil passing through the bearing.
 
John many good tips here.

Lebowski's well I kind of hoped I wouldn't have to go that route. I am clumsy with soldering. Not much experience. And doing a complete controller build will also be time consuming for me as it would involve much trial and error. Zombiess did make something for the Lebowskies, but not the complete controller?
Is anyone making em ready made?

So far my understanding have been that sensorless have few if any advantages compared to the gains of Halls. I will try to read up on that, maybe this weekend.

For cooling I saw that the transmagnetic motor had some hefty covers. Is it something like this you mean?

transmag_10.jpg


If you got any pics of your setup feel free to share. I agree that the copper will not have the best possible cooling with water/radiator as you say, but I think I have a work around. Been used for high power turbo engines - after a hard run if you turn off your car it will still run a few minutes to ensure turbo is properly cooled before it stops. Forcing the radiator fan and pump to continue working say after running up a steep hill, and you stop at the top. That would mean heat build up while stopped. Controlling the pump and fan with software takes care of that, set values and forget about it.If you stop for red light, after hard acceleration the circulation pump and radiator fan would still work to remove heat from the motor even if bike does not move.

And "luckily" we are "blessed" with about 340-350 days a year with air temps well below 20 degrees. So basically that would like have your radiator mounted inside your refrigerator. :lol:

Both pump and fan is easy to run without stealing noticeable range from the batteries. If you think of the efficiency of the electro motor it is really not a hole lot of heat we need to remove. Haven't done the math yet but it is not much of a problem for liquid cooling to remove that kind of heat. The devil is in the details. As always. As a custom water block for motor means hard time consuming work first hand to get it working - then set it and forget. Motor temp will not be on your mind ever.

If you have pics of your idea for cooling that would be great. I will look into that as well. They devil with water cooling is that I would have to take motor to bits to get a 3D sketch of stator to get a heat block made that fits great and works well. If I can avoid all that PIA with another cooling solution that might very well be the winner.
 
Skate bearings are fast for several reasons. One, they are Loose. The allowances are greater and they have much play built in. Two, they are dry (no grease) and use a tiny bit of oil. Three, they have non contact shields, and not sealed.

Ceramics with seals or grease will be much slower. Dry (with light oil), and non contact shields they are super fast spinning. 30,000 plus rpm no problem with very little heat build up.

If you want reliability and power handling you want a tight bearing with a top notch rubber coated steel seal and packed with high temp water proof grease. It will take a few hours to run in, but will last.
 
For hub motor applications, two conditions exist which make how the bearing is "prep'éd" more important than "country of origin".
They are;
The relatively low RPM's they operate.
The lack of dedicated oil seals.
Prep'íng the bearing;
Remove both seals carefully with a scribe tool and clean out the factory installed grease with brake cleaner and pack the brg. with a quality water-resistant grease.
Without a bearing packing tool, the grease is best worked in with the palms in a mannor that can be best described as "ä kid making farting noises".
The Idea here is to leave no void for water to enter and start mixing with the grease.
There is some debate as to this technique in higher speed applications due to "cavitation effect", but that is a non-issue for hub motor use.

As a side note:
Are Japanese , Swedish and German bearings of better quality than Chinese bearings? The answer is no doubt!
are Chinese bearings good enough quality for hub motor use? Again, the answer is yes.
The are millions of Chinese machines out there and their bearings survive much harsher enviourments than our hub motors see. Rear whl. brg.s on dirt bikes come to mind.

BTW, there is no faster way to damage a new bearing than to "spin it up" with compressed air. Oil or no oil, a very bad idea!
 
Moto, how big a bearing are you packing with your palms?
About 75% full is right. You don't fill it. Filling leads to escape, and escape leads to picking up dirt around the seals, which damages them.

Spinning up old bearings with air is fun. It can also destroy them there and then. Dropping them on concrete certainly does, as its no different to taking a grinder to them. I don't suggest it as a means to test them, It's a means to test your lubrication choices. It's a workshop game, like airline archery
 
friendly1uk said:
Moto, how big a bearing are you packing with your palms?
About 75% full is right. You don't fill it. Filling leads to escape, and escape leads to picking up dirt around the seals, which damages them.
Your 75% rule only applies the bearings turning very high RPM, when the forces of centrifugal, pressure and heat come into play.
Granted, an over-heated hub motor can get hot enough to melt grease, but at that point, one's motor is likely going the have bigger problems.
Far and away, the most destructive element to the bearings in our application is water.
The best way of combating water ingress is to fill the cavity. In fact, until relatively recently, when seal(external) technology developed true "water-proof"seals, applications where water contamination is a "fact of life" relies on periodically injecting fresh grease, forcing the old out, keeping the cavity full and refreshing the grease at the same time. Some systems provide a relief valve for the purpose of allowing the old grease to escape. But most simply allow the old grease to ooze past the external seals. Grease on the outside of the seals, attracting dirt or not, does no harm. It is after all, on the outside.

The advice of this retired motorcycle and turf equipment mechanic is as follows;

If you ride in seasonal harsh condition, such as snow, snow melt, salt, etc., replace the bearings at the end of the season.
If you hub motors are ever used in water approaching the level of the axle, replace the bearings right way.
I say replace because removing bearings without damaging them can be tricky. Most often, the easiest way to remove them is to drive them out from the back side. BUT, the drift(punch) force can only be applied to the outside race, never to the inside race. If this can be done, the brg. can be reused.
A bearing that fits in the boss should require some force to install. For us, that means a socket or driver sized to contact the outside race only. If the bearing "drops in", some Loctite Bearing and Stud "locker"should be used.

BTW, It would seem obvious from this discussion that our hub motors would benefit greatly from external seals(to keep contaminates out, not the grease in). But I suspect the engineers decided the width required would be better used for something else, like....stator width.
 
motomech said:
BTW, It would seem obvious from this discussion that our hub motors would benefit greatly from external seals(to keep contaminates out, not the grease in).
Actually, BMCs have external double lipped oil seals. They work well at keeping out poo, but without a vent hole in the case, moisture gets sucked in anyway as the motor cools.
 
motomech said:
BTW, It would seem obvious from this discussion that our hub motors would benefit greatly from external seals(to keep contaminates out, not the grease in). But I suspect the engineers decided the width required would be better used for something else, like....stator width.

Mine have external seals in addition to the sealed bearings. In fact, going back to 2008, all of the hubmotor factories I've dealt with directly put axle seals on their hubmotors. It's just one of the things that separates quality from the common stuff that's assembled from the lowest cost generic parts. You just have to find the ones who build for use in China, not only for export.
 
Good to know. Anyone who plans to ride in wet weather would do well to make sure their motors come with external seals
My experience is limited to Q100's, MXUS geared and Ezee geared motors, none of which come with ext. seals.
Not a concern for me here in the desert.
 
An important idea for all to understand within this discussion is hydrodynamic lubrication and friction.

https://www.youtube.com/watch?v=KGgIvDNDuYc I highly recommend watching these videos, and taking time to understand the ideas presented.
https://www.youtube.com/watch?v=mK-iz_xfEI4
 
Some things are definitely lost in translation lol

Moto, I have seen many bearing covers of the size we are talking about worn away by dirt in vehicular use. That little bit that comes out is constantly stirred, so anything picked up will find it's way through stirring and heat cycling. 100% fill with nipples for displacement works for exposed bearings, but 75% should be ample with side covers, as most will be displaced to where it is needed. I'm interested in free running so 100% fill is not going to interest me in any event. I know what the book says and what works.

The idea a dunked bearing needs changing right away could only come from a mechanic. It is an instant presumption of ingress. Even this is not the end of the world though. Greased and oiled metal parts don't allow the water to touch them. Water getting in easily will likely get out easily. He is over reacting. Lots of our motors have been dunked I'm sure. Nobody changed the bearings I will wager.


You can see clearly see the bearings in my cup&cone front wheel. No sign of grease though. Just clean looking balls in clean looking races that water just beads upon and runs off. They salt heavily here, so it seems an open bearing that washes itself out is working better than a sealed that can perceivably trap water inside. Old tech beating the new again.
 
Kiriakos GR said:
bowlofsalad said:
An important idea for all to understand within this discussion is hydrodynamic lubrication and friction.

No I will skip this lesson, MAXTOR hard drives and their hydro bearings after all this years did not have manage to be recorded by the history as amazing innovation.

Yeah, friction is a silly idea to be concerned with when motion is involved.

Hydro bearings do not use hydrodynamic lubrication? Please elaborate. Is there a reason you made this post or did you simply feel the dire need to lament about how maxtors genius has gone ignored for some reason? I ask because surely you are making a suggestion that is an alternative to using lubricated (hydrodynamic) bearings?

Just to say this in another way, you must know of a mythical source of wildly better bearings that do not use hydrodynamic lubrication, and now you are going to share them with us so we use them in our electric bicycles because why else would you have made this post? There are only two possibilities I see here. I won't label option A, but option B is you are going to various threads and writing several incomplete posts. Where are the goods?
 
friendly1uk said:
Some things are definitely lost in translation lol

Moto, I have seen many bearing covers of the size we are talking about worn away by dirt in vehicular use. That little bit that comes out is constantly stirred, so anything picked up will find it's way through stirring and heat cycling. 100% fill with nipples for displacement works for exposed bearings, but 75% should be ample with side covers, as most will be displaced to where it is needed. I'm interested in free running so 100% fill is not going to interest me in any event. I know what the book says and what works.

The idea a dunked bearing needs changing right away could only come from a mechanic. It is an instant presumption of ingress. Even this is not the end of the world though. Greased and oiled metal parts don't allow the water to touch them. Water getting in easily will likely get out easily. He is over reacting. Lots of our motors have been dunked I'm sure. Nobody changed the bearings I will wager.


You can see clearly see the bearings in my cup&cone front wheel. No sign of grease though. Just clean looking balls in clean looking races that water just beads upon and runs off. They salt heavily here, so it seems an open bearing that washes itself out is working better than a sealed that can perceivably trap water inside. Old tech beating the new again.


Some years ago we did some water skipping with snowmobiles across a lake. Needless to say one finally sunk.
We removed the exhaust pipe, spark plugs and just kept pulling the cord to turn engine over until their was no more coming out of the top or exhaust. This particular snowmobile had a few more runs across the lake without sinking and got placed in summer storage. Next winter during the first few trips several bearings was ruined. One bearing on the secondary clutch axle I think it was was so ruined it didn't turn hardly at all, with the result that the bearing bottom (the part that is pressed to the axle) did the spinning rather then the bearing itself. Leaving a rather big shaving in the axle and color changes in the metal from the extended heat build up.

I have never seen so many bearings go in so sort amount of time in any vehicle before. The only conclusion I can draw is that the snowmobile had been submerged under water. Water had entered the bearings and probably still trapped in there when stored for the summer, and when winter came the grease mixed with water froze or whatever causing the bearings to lock up.

After that I would consider either changing or at least reclean and regrease bearings that have been hosed with water or submerged.
After all, a bearing is not a costly part - changing an entire axle is. Not to mention a PIA job.
 
Kiriakos GR said:
Regarding ebike motor I am going to use one very recently developed Mid-drive motor, which is still unknown to the market.
This using a larger needle bearing instead of ball bearing, and I do have much more confidence that this is a much better over all product and design.


Needle bearings? I think it was said once that those where created to withstand greater RPM then regular bearings. Hence why they are commonly used inside a motor. If that is correct I can't tell, as I am purely a self thought hobby mechanic with no proper schooling. But that was what I once was told from an engineer.

Might be a good choice for your mid drive if that engineer was correct.

So to the important part, share some news on that secret motor of yours.....details pls.
 
macribs said:
Some years ago we did some water skipping with snowmobiles across a lake. Needless to say one finally sunk.
We removed the exhaust pipe, spark plugs and just kept pulling the cord to turn engine over until their was no more coming out of the top or exhaust. This particular snowmobile had a few more runs across the lake without sinking and got placed in summer storage. Next winter during the first few trips several bearings was ruined. One bearing on the secondary clutch axle I think it was was so ruined it didn't turn hardly at all, with the result that the bearing bottom (the part that is pressed to the axle) did the spinning rather then the bearing itself. Leaving a rather big shaving in the axle and color changes in the metal from the extended heat build up.

I have never seen so many bearings go in so sort amount of time in any vehicle before. The only conclusion I can draw is that the snowmobile had been submerged under water. Water had entered the bearings and probably still trapped in there when stored for the summer, and when winter came the grease mixed with water froze or whatever causing the bearings to lock up.

After that I would consider either changing or at least reclean and regrease bearings that have been hosed with water or submerged.
After all, a bearing is not a costly part - changing an entire axle is. Not to mention a PIA job.

I used to deal with jet skis many years ago, both recreational and racing, and we ran marine grease anywhere grease was required. Given the sort of abuse they took and the number of times engines got fully submerged and filled with water(salt and fresh water), the only issues were with those that did not use marine grease and good quality oils and who did not run their ski for awhile after all the water had been removed, to heat the engine up nicely and make sure any residual moisture had been removed. We tried things like swapping the driveshaft bearing housings from grease to oil, gun drilling the steel driveshafts or swapping to alloy driveshafts. Yes, they spun up easier and for longer on the bench but performance improvement on the water was not measurable.

EDIT: It made no difference if the bearings were open, sealed or needle roller.
 
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