Date: Wed, 5 Dec 2007 13:15:03 -0800
Reply-To: Scott Daniel - Shazam <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Shazam <scottdaniel@TURBOVANS.COM>
Subject: Re: Sealed Bearings?
In-Reply-To: <HHEAJIOMDPBGGCKHACGJMENJCOAA.al_knoll@pacbell.net>
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Guess I missed the start of any sealed bearing thread.
I find that Prolong Synthetic spray grease gets right past those outer seals
and noticeably improves the smoothens of a sealed bearing.
Subaru timing belt guide rollers would be a good example of where I might
do this sometimes. Works like a champ.
I *never* used sealed car batteries. How ya gonna test each cell with a
hydrometer ?
What's a hydrometer ??
Old fashioned test device, before electronics. Nah, that couldn't be any
good anyway then !!
But I see zero reason to have a sealed battery, if it's a conventional
lead-acid type.
Scott
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Pensioner
Sent: Wednesday, December 05, 2007 1:09 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Sealed Bearings?
Most 'sealed' rolling bearings designed to run in an air environment are
'permanently lubricated'. That is to say the lubricant lasts for the life
of the bearing. (reread that sentence, it's catchy)
The 'seal', usually a clip-in, flexible disk with a hole in the middle for
the inner race, is designed to keep lubricant 'grease' in the bearing, not
really to keep other materials out. The sliding mating surface of the
'seal' is lubricated from within the bearing by a small amount of grease or
if it's a French bearing such as found on Citroens, a small amount of
'gras'. The tiny amount of grease at the seal/race junction keeps the seal
from being abraded by the shaft and as such weeps a bit of grease. If this
lubricant is not present at the junction the seal would quickly wear and
enlarge the clearance between the seal and the inner race. The bearing
would soon fail under these compromised seal conditions through loss of
lubricant. (end of life situation, accelerated by the loss of lubricant,
note the second sentence above)
This weeped grease catches external particle contaminants and prevents them
from migrating into the bearing itself and as such should be left in place.
If you periodically remove this grease, more grease migrates from inside the
bearing to the interface. Eventually such fastidious cleaning will cause
accelerated failure.
The seal is also effective at keeping water inside the bearing. So no
pressure washer or operation/submersion for this kind of bearing as the
invisible emulsification of the grease precipitates and end of life
situation as described above.
Much has been written about 'sealed bearings' in the Tribology literature
and a suitable search will reveal hours of potentially fascinating
discourse.
RVC What is the recommended 'sealed/maintenance free' Group 41 battery
among those gathered here together? My Delco Freedom is now applying for
AARB status.
pensioner