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Old 08 August 2008, 11:38   #21
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Originally Posted by jyasaki View Post
I don't think so. My take is that the BB simply creates a reserve of grease (albeit small) that is slightly pressurized so that any grease loss is compensated for (i.e grease loss is replaced by grease rather than air.) It *may* tend to keep water out, but I don't think that was a primary design criterium. The grease is supposedly held at a 1.5 to 2 psi pressure, which will be overcome in very little water depth. So, probably not really useful in stopping an inflow of water at realistic launching depths.

Lets see: 14.7psi at the surface, twice that at 33 feet, so 2 psi would be applied at 4.5 feet. Deeper than I would have guessed, but that assumes the 2 psi part is right. The spring in mine are pretty wimpy.

jky
I suppose if the grease is always at the seal (and under some pressure) and water does manage to get through the seal, it's not going to get to the bearings that easily as the grease at the seal and a good bit back towards the bearings will be static anyway (ie not getting churned round with the bearings). I still don't see any way for grease to get from outer to inner bearing in my hub as the bearings are in the way and I doubt grease could get past. Outer bearings have always been absolutely fine as the "savers" are topped up. Maybe I need to look at a new axle with hub that allows grease to pass from outer to inner so inner is always greased well!
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Old 08 August 2008, 11:40   #22
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Originally Posted by Bigmuz7 View Post
Those look interesting, they say its a zinc alloy I'd never of thought that would have been hard enough to be used in a bearing, yet they say you could get 5 times more life out of them ? Err I think they want to patent that then, cos thats quite a claim

5 times - that's a whole 10 weeks in my case :-)

I assume that you can't get stainless bearings? Maybe it's too hard to manufacture to required precision.. I suppose it would stop the rust but could equally still get destroyed if race is not 100% full of grease... I'm not a materials expert
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Old 09 August 2008, 07:10   #23
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dont forget that after a long journey the bearings get quite hot and putting a boat trailer straight in the water will cause the bearings and grease to cool down fast which can then suck water back through the seal owing to contraction ,even seen that happen with bearing savers with deep water launches,
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Old 10 August 2008, 05:52   #24
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Quote:
Originally Posted by jyasaki View Post
I don't think so. My take is that the BB simply creates a reserve of grease (albeit small) that is slightly pressurized so that any grease loss is compensated for (i.e grease loss is replaced by grease rather than air.) It *may* tend to keep water out, but I don't think that was a primary design criterium. The grease is supposedly held at a 1.5 to 2 psi pressure, which will be overcome in very little water depth. So, probably not really useful in stopping an inflow of water at realistic launching depths.

Lets see: 14.7psi at the surface, twice that at 33 feet, so 2 psi would be applied at 4.5 feet. Deeper than I would have guessed, but that assumes the 2 psi part is right. The spring in mine are pretty wimpy.

jky
That will be 1.5 t0 2 psi over ambiant pressure as it is maintained by a spring, so it will still be 1.5 to 20 psi over when under pressure from the water.
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Old 10 August 2008, 19:01   #25
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Originally Posted by m chappelow View Post
dont forget that after a long journey the bearings get quite hot and putting a boat trailer straight in the water will cause the bearings and grease to cool down fast which can then suck water back through the seal owing to contraction ,even seen that happen with bearing savers with deep water launches,
Yes agreed - in my case however, boat rested overnight before launching so everything was cool.
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Old 11 August 2008, 01:09   #26
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That will be 1.5 t0 2 psi over ambiant pressure as it is maintained by a spring, so it will still be 1.5 to 20 psi over when under pressure from the water.
That doesn't sound right

The spring is mechanical so will press at a set rate linked to its compression more compression more force and any external forces will overcome the spring or increase the pressure as it can't adjust its self i.e. water on one side of the plate or even your finger
1.5-2.0 psi is very low, your cold water tap is normally 30-40 psi
If you walk into water with a pair of waders on think of the pressure on your lower leg

The above could be crap but may not be

Jim
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Old 11 August 2008, 07:53   #27
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That doesn't sound right
Yes it is. The water will press in all directions and onto the same surfaces just as the air does. It's the pressure differential across the seal that's significant. I suppose, if being pedantic, because the buddies piston will move inwards by a small amount the spring pressure will reduce a little but I doubt it is worth considering.
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