Balls free or balls in cages?

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Capt Slog
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Balls free or balls in cages?

Postby Capt Slog » Thu Feb 28, 2013 15:20 pm

I'm taking about wheel bearings here.

At the moment my bike has the cup and cone bearings that I recall as a lad. Just as I did then, I fill the cup with a bit of grease, 'stick' the balls back in, put it all together and adjust.

It's just that I've seen these on the net and in bikes shops....

Image

Are these interchangeable with the free ball type cup and cone (assuming all the diameters are correct) or is one type of hub only meant for one arrangement?

Is there any advantage with the caged type bearing? (other than speed of rebuild possibly). It's just always seemed wrong to have the neighbouring balls rubbing together (this thread would go down well in Bottom Bracket :lol: ) and the caged system looks more correct.
"Dinosaur" "... horrible human being", BR Mod.

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RPD Steve
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Re: Balls free or balls in cages?

Postby RPD Steve » Thu Feb 28, 2013 16:47 pm

I would advise that you stick with loose balls. Though on 1st thought it may make sense that more balls = more drag, its not quite as simple as that. It may be true that less balls = less drag felt when spinning by hand, but that 'static' drag is only due to movement through the grease, seals rubbing and any strain losses (where energy is lost though the bearing races and balls 'squishing' into a rugby ball shape and back again as they rotate under load) caused by the pre-load applied, which on cup/cone is next to nothing.

As you load the bearings up however, by sitting on the bike, cornering putting bending loads on the axle, your 'dynamic' drag is much greater due to increased strain losses explained above, caused by the increased load when riding rather than holding a wheel. The more balls in a system the less each deform and the less energy is lost overall. Likewise wear on the overall system is reduced as the point load at each ball is reduced.

A reduced number of caged balls is used when it is 'fit for purpose' i.e. when someone has done the sums that they will support the load needed for the life needed. The cage is just to keep the balls evenly distributed around the bearing. This can also be achieved by using balls so sized and a number so that they completely fill the bearing.

That's why you can often get people going 'look how good my wheels spin', but it may mean nothing in reality.

And all of the above energy losses are tiny, and I'm not saying they are of an order you would notice, but from an engineering point of view thats how i see it... Sorry for the essay and I hope you wake up soon lol

thecycleclinic
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Re: Balls free or balls in cages?

Postby thecycleclinic » Thu Feb 28, 2013 22:03 pm

Also buy grade 25 or grade 10 stainless loose balls. Those cheap caged balls on ebay are probably grade 300 or worse. The higher the grade number the less round the balls are and this is not good. You will get longer bearing life with good quality balls. Just buy replacing the balls in a cheap hub with good one you can have a very smooth and durable hub.
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proto
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Re: Balls free or balls in cages?

Postby proto » Fri Mar 01, 2013 07:44 am

Personally I'd avoid stainless steel balls, they are relatively soft. Chrome steel balls will give much better service if maintained, i.e. lubricated, oiled, greased etc

All that RPD says is correct. The load bearing capacity of a bearing is determined by the number and size of the balls. The bigger and more of them the better. Removing the cage allows more balls to be fitted.

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Capt Slog
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Re: Balls free or balls in cages?

Postby Capt Slog » Fri Mar 01, 2013 10:17 am

Thank you all for the useful replies.

New balls please!
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