Older Abit AI7 homebuilt acting oddly - Page 3

 
On Sun, 06 Jan 2008 00:07:07 -0500  'kony'
wrote this on alt.comp.periphs.mainboard.abit:


Well, I hear what you say and also Andrew's previous comments but
it is the case that my fans run very nicely after the treatment with
graphite and oil.

In view of your comments, I'm stuck to know what to use in future!

 On Sun, 06 Jan 2008 12:47:02 +0000, abit.user


I don't doubt that they do work ok for now, but the bearing
has small pores into which the oil will seep (if it's not
clogged by solids like graphite) which is good as it means
more retention in the bearing and if the bearing where to
start drying out it still has more reserve oil in it, and
over the long term it should be worse to have solids
clogging the pores IF it has any effect at all.  These are
not new ideas to the PC/fan world, the basics of lubrication
have been around and extensively tested for 100 years and
more - though also in the PC/fan industry the worlds most
respected fan manufacturers do not put graphite in their
bearing lube which should say enough by itself, since
graphite isn't especially rare or expensive.

If you wanted to mix something into the oil, mix some
synthetic grease in, just enough that the drop-point of the
grease is below the ambient temp.  It's not really necessary
that it be synthetic, but it does tend to remain more stable
given some heat and time.

The thinner base oil will then seep into the bearing more
with the thicker portion remaining more around the thrust
bearing helping to keep all the lube where it does the most
good instead of running out.  In certain situations (like
some power supplies that come with cheap 120mm sleeve
bearing fans in them, or video card fans) using such a lube,
preemptively rather than waiting till the bearing is worn
down, can add quite a bit longer interval between subsequent
servicing... though ideally it's better to just replace any
marginal video card fans as they are often pretty poor even
in their best condition, turning too fast and wobbling too
much on too narrow a bearing in a horizontal position.

 
On Sun, 06 Jan 2008 08:35:00 -0500  'kony'
wrote this on alt.comp.periphs.mainboard.abit:


Thanks kony, I'll keep your comments for the next time I
do some lubrication. Much appreciated.

 On Sat, 5 Jan 2008 23:48:19 +0100 (CET), Andrew Smallshaw


Ball bearings have some play in them to rotate, and once
worn onto the point of noise, even more play.  They ride on
a film of grease.  Adding oil reduces the film strength
allowing the bearings to move around more (in directions
they weren't supposed to be moving).

That's the rationale, but I also see it in practice.
Perhaps all ball bearing fans won't get noisier but IMO once
one is noisey it won't be improved long term with oil while
a sleeve bearing fan's life may be extended multiple times
it's original lifespan (if it weren't relubed).  This mostly
pertains to the low quality sleeve bearing fans found in
PCs, not the higher quality ones like Papst or Panaflo.





The oil viscosity to use depends on the tolerances.  A brand
new fan which isn't likely to need relubed yet (except some
very poor ones) will have tighter tolerance and a medium
weight instead of thin oil would be called for.  With tight
fitting parts a very thick oil might not fully wick into the
bearingway but this situation is gone once the fan has worn.

Once a fan has worn the bearing, especially onto the point
of making noise or not turning properly there is a lot of
play in it, a larger gap that needs thicker, heavier weight
oil.  Thin oil will slop, be pumped out of the bearing much
faster due to the elliptical wear pattern in the bearing and
simply due to gravity because of the lower film strength.
Thin oil can work, but will not reduce fan wobble as much so
the fan wears faster and will need to be reapplied much more
often.  I would see thin oil as another emergency measure to
keep the fan running till a replacement can be found.  

The situation changes when dealing with different kinds of
fan bearings not seen in PC fans.  With larger fans such as
in a HVAC unit you will find much larger bearings and the
fans are typically relubed preventatively instead of after
the bearing is shot, and the bearing cup has a felt or
equivalent matting to hold the lubricant.  In that case the
lubricant has to be thin enough to flow through the matting.
Since a PC fan's reservoir has no such matting but only
gravity to assist it, the thicker the oil the more it will
stay where it's supposed to.

 
[SNIP]

Don't they use sintered metal bearings in fans any more?