David Jenkins
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| posted on 20/11/08 at 12:47 PM |
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How good's the seal on sealed bearings?
I have a little project that I'm currently thinking about, and I'd like a bit of info from those "people who know useful
stuff".
* I want to make a cover that will rotate, with a stationary shaft going through the middle.
* I do not want any dirt, dust or water to go through the gap where the cover meets the shaft.
* The shaft and cover will be unlubricated.
I originally thought of some kind of rotary seal, but realised that being unlubricated in a dirty environment would mean that the seal wouldn't
last very long.
Then I thought about those ball bearings that have plastic or metal seals on each side - the outer race could be held by the cover, and the shaft can
go onto the fixed shaft. This would give extra support, which would be a bonus.
The only thing is - how good are those seals? Do they come in different grades?
All info gratefully received!
cheers,
David
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02GF74
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| posted on 20/11/08 at 12:56 PM |
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What do you define as "dirty envronment"?
I had a set of sealed jockey wheels (those ickel wheels on the rear gear shifter on moutnain bike) and they didn't last too long; less then the
standard jobbies.
Water got in and seized the bearings.
If you look up the seal specification e.g. on RS, then maybe that would give some info.
Oh, just another thought. The bottom bracket on bikes is a sealed affair that can see mud, water etc. and they last quite a long time, several 000s
miles.
I suspect my jockey wheels were not as well sealed; can't recall if they had metal or rubber seals.
[Edited on 20/11/08 by 02GF74]
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Bob C
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| posted on 20/11/08 at 01:08 PM |
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Similar (same) question; I want to make a little gearbox, would a sealed bearing stop oil leaks? (bearing to housing & bearing to shaft can be
loctited)
BTW the metal seal ones are described as "shielded" rather than "sealed"
[Edited on 20/11/08 by Bob C]
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dinosaurjuice
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| posted on 20/11/08 at 01:20 PM |
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how big does this seal need to be?
i would be looking at valve stem seals, possibly off a tractor/truck if car ones too small.
or motorbike fork dust seals are fairly good.
i cant see how the seal on a bearing will be any better than just a normal seal.
Wil
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RickRick
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| posted on 20/11/08 at 04:20 PM |
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i know bearings we use for rc car racing, rubber sealed, ptfe sealed, and metal sheilded. none of which are water tight or dust proof, but do keep a
lot of gunk out, however running them without seals they last only a couple of months due to the dust that gets in
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r1_pete
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| posted on 20/11/08 at 04:51 PM |
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Try THESE guys, very helpfull and all bearings have online specifications.....
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Mix
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| posted on 20/11/08 at 04:58 PM |
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Hi
Might be worth looking at how prop shafts on boats are sealed ......... or if you want to think out of the box ...... air bearings.
Regards Mick
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David Jenkins
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| posted on 20/11/08 at 07:18 PM |
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Dirty environment = front wheel hub. Loads of dust, mud, and occasional spraying with water.
How big? = 8mm dia internal fixed shaft, don't care about the outside of the seal/bearing as long as it's not too big.
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flak monkey
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| posted on 20/11/08 at 09:17 PM |
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Rubber sealed bearings are pretty good. The metal ones are more for higher temps or high speeds, but they still have very good seals.
From SKF you would be looking for RS1 seals (which are the plain rubber seals) or RSH seals which are the full contact seals and ideal for dusty and
wet environments. These letters are found at the end of the brg description e.g. 607-2RSH
David 
Sera
http://www.motosera.com
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paulf
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| posted on 20/11/08 at 09:40 PM |
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As above , I work in a food factory and machinery gets pressure washed each day, the rubber sealed bearings last well unless directly jet
washed.Sometimes we have fitted plastic shields to avoid direct jet washing.
The same bearings could be used to retain oil in a gearbox and infact often are on light machinery gearboxes.
Paul
quote:
Originally posted by flak monkey
Rubber sealed bearings are pretty good. The metal ones are more for higher temps or high speeds, but they still have very good seals.
From SKF you would be looking for RS1 seals (which are the plain rubber seals) or RSH seals which are the full contact seals and ideal for dusty and
wet environments. These letters are found at the end of the brg description e.g. 607-2RSH
David
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David Jenkins
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| posted on 20/11/08 at 10:08 PM |
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Thanks! Exactly what I needed to know!
(I've always said that there is always someone who knows stuff on this site...) 
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DarrenW
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| posted on 21/11/08 at 10:28 AM |
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What type do you need? I have a few 61905's with seal on one side, shield on other (ID25, OD42 x 9mm thick) and also a few 6203's sealed
both sides (ID17, OD40 x 12 thick) that you can have to try.
Also have some small 626Z's but they are shield both sides (ID6, OD 19 x 5mm thick) - probs no good. Ideal for drawer runners.
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DarrenW
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| posted on 21/11/08 at 10:32 AM |
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i should have said the science behind bearing maunfacture ican be quite daunting. Even when bearings are sealed there are different spec seals used
and also they can be manufactured with varying torque to rotate specs which indicates how hard the seal contacts the bearing faces (and other factors
too deep for discussion).
The 61905's i have are quite tight, you can feel the red seals in good contact. the 6203's are blue seals and feel less tight.
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