Bearings quality

[amberwolf]

If you've never researched it, how do you know whether they are superior or not? Just because a company used something and then stopped doesn't mean that thing is bad, just that they aren't using it. If you don't research *why*, then you don't know they are bad or good or indifferent.

Maybe they stopped using them because they cost more? Or the ones they wanted became unavailable? Or they changed engineers on design teams, and the new ones didn't know why they were used so they went with a different kind? Or maybe their marketing department didn't have any idea what tehy were talking about, and they weren't even the kind of part they said they were?

All of those reasons (and many more) have probably been true of one component or another in various companies over the years.

Unless you research them you wouldn't know.



Now, that said, a little (very little) research:

http://en.wikipedia.org/wiki/Fluid_bearing

* In fluid static, hydrostatic and many gas or air bearings, the fluid is pumped in through an orifice or through a porous material.
* In fluid-dynamic bearings, the bearing rotation sucks the fluid on to the inner surface of the bearing, forming a lubricating wedge under or around the shaft.

Hydrostatic bearings rely on an external pump. The power required by that pump contributes to system energy loss, just as bearing friction otherwise would. Better seals can reduce leak rates and pumping power, but may increase friction.

Hydrodynamic bearings rely on bearing motion to suck fluid into the bearing, and may have high friction and short life at speeds lower than design, or during starts and stops. An external pump or secondary bearing may be used for startup and shutdown to prevent damage to the hydrodynamic bearing. A secondary bearing may have high friction and short operating life, but good overall service life if bearing starts and stops are infrequent.

So, best guess is that with computers set to common powersaving standards, which tend to spin drives down when not in use, tehy were having a lot of bearing failures and drives that didn't spin up anymore because of the frequent starts and stops.

That also implies it would be a bad idea to use this type of bearing on vehicles like ours, as they would almost never be at any constant speed for very long, and would see even more frequent stops/starts *under load*, and would probalby have a high failure rate.



There's some more info here:
http://www.hardwaresecrets.com/article/The-Truth-About-Fluid-Dynamic-Bearing-FDB-Fans/1807
that may give some other data.



Another two minutes research also finds that at least most, perhaps all, of the PC harddisk industry uses FDB in their drives now. So if Maxtor stopped advertising it, it was possibly because everyone else changed over and now theirs was no longer unique. Marketing only cares about unique stuff--why bother wasting ad space to cry out things everyone has?
http://www.silentpcreview.com/Recommended_Hard_Drives

 

[Punx0r]

Surely no one is considering a fluid bearing as suitable for a bicycle hubmotor???

One issue with oil/grease and water is that though they may not mix normally, combined with mechanical agitation (like a rotating bearing) they will readily form an emulsion, which has poor lubricating properties and can cause corrosion.

 

[speedmd]

If you ride in rivers, ponds and creeks, consider swapping out the bearings for stainless steel ones. They are good quality these days and save much headaches when riding into the deep stuff. Make sure your wire connections are well sealed.

 

[amberwolf]

Then why are you providing advice about things outside your knowledge, especially if you are unwilling to even do an extremely minimal amount of research before making a statement?



As far as Maxtor goes, if you look at what I posted above, you'll see that the rest of the industry followed them and changed *their* bearings to the same kind. As to why? I don't know because I didn't find an article that stated one way or the other, but I would guess based on than the wikipedia info on NRRO for precision and noise reduction for customer satisfaction that those are the reasons.

 

[Offroader]

I'm considering replacing the bearings in my cromotor. I can feel very slight grind when spinning the motor bearing attached to only the side cover on my finger. I'm not sure if this even matters?

I was wondering if angular contact bearings are worth the extra money over the normal bearings?

Thanks.

 

[Chalo]

I was wondering if angular contact bearings are worth the extra money over the normal bearings?

No.

 

[zerodish]

I found a bunch of ceramic Conrad type bearings in the road about 4 years ago. Don't remember the brand other than they were manufactured for a skate board company. They had been run over so I took them apart. I put 44 balls in my loose bearing pedals and have been riding them dry every since. Also I went to the NASA technical servers and read every thing about ceramic bearings. Use silicon nitride balls with steel races. Silicon nitride bearings fail safe. I have had one fail a chip comes off smooth just like a flint arrow head. This was very hard to see it was so small and impossible to photograph. A silicon carbide ball will split in half. Silicon nitride balls work fine and will last about twice as long a steel balls in a cup and cone design. However this is not their biggest advantage. Like I said I'm running them without lubricant. Cups and cones also last longer because there is less rust I recommend getting bearings you can rebuild and replace the balls one by one as they fail. https://www.flickr.com/photos/63373992@N07/8729102705/in/photolist-eW6NEi-cXjTy7-eimW7M-fraX88-nB8wTA

 

[Offroader]

Could anyone explain how this type of bearing as shown in the picture is different than the typical bearing with black rubber?

My cromotor has this type of bearing on one side, but I want to order replacements with the normal black rubber. Are there any differences?

 

[bowlofsalad]

Could anyone explain how this type of bearing as shown in the picture is different than the typical bearing with black rubber?

My cromotor has this type of bearing on one side, but I want to order replacements with the normal black rubber. Are there any differences?

I could be mistaken, but those look to be shielded bearings, the Z at the end of the number signifies shielded bearings. Shields are bearing covers that do not come in contact with one of the races. The idea is to get the shield very close to the race to inhibit some things from coming in but generate no drag, but it's like putting a screen door on a submarine in many situations.

Cartridge bearings have numbers and letters that identify them, the numbers specify the dimensions, the letters specify the shield/seal. Researching subjects like shields and seals and their varieties might help give some education on the subject.

I'd look for 6205 2RSH bearings, if I am reading that number right.

http://evolution.skf.com/new-sealing-solutions-for-deep-groove-ball-bearings/ This article may help explain a few things.

 

[Punx0r]

Have a look here: http://www.gobearings.com/shields.htm

What you have would be a bog-standard metal shield (Z). I believe the black plastic shields are usually just be plastic version of the Z type seal. The D-type seals look interesting.

 

[Chalo]

Metal shielded bearings have the suffix -ZZ, as in 6004-ZZ. Rubber sealed bearings have the suffix -2RS. Often the bearings used in a component that has one exposed and one sheltered side to the bearings will have a rubber seal on the outside and a metal shield on the inside. Those are designated by the suffix -ZRS.

 

[Offroader]

Thanks guys. Do you have any recommendation on what I should use?

The cromotor has one shielded and one rubber sealed. I have an extra pair of side covers probably from an older cromotor and it had both rubber sealed.

What would you suggest I use?

 

[Chalo]

If you have the choice, use rubber sealed bearings. VXB and The Big Bearing Store are both good online sources.

Enduro bearings are available from bike shops and are especially for bikes, featuring a quantity of grease that would be an overfill of an electric motor bearing.

 

[Offroader]

Thanks Chalo I'm going to order my self some SKF 6204 2rs and 6205 2rs. They are like $8 and $6 dollars each, a few dollars more than the Chinese bearings but I figure they probably have better quality control.

It seems like all my Chinese bearings get a bit grindy, not sure if that will actually lead to any measurable differences like you mentioned earlier.

http://intechbearing.com/products/6204-2rs-skf-sealed-radial-ball-bearing?utm_medium=cpc&utm_source=googlepla&variant=1073463521&gclid=Cj0KEQjw-OCqBRDXmIWvveLE3_cBEiQAZWfImRUhbb5WXIY0hTQ0GH4bHwStQwb8XpCMU1H7Vh-4UiAaAhsC8P8HAQ