On Fri, 19 Sep 2014 17:30:41 -0700, wrote:

Years ago I was cleaning some bearings and was blowing the solvent out
with compressed air. I knew this was bad news but it was interesting
to really spin up up bearings. Anyway, I put this bearing on my index
finger and spun it up real good. The pitch of the whine from the
bearing rose higher and higher as the speed increased. Just when the
pitch got so high I couldn't hear it the outer race of the bearing
exploded and the balls went flying. I thought my finger was broken
but it just hurt like hell. Needless to say I bought new bearings.
Eric

I had something like that happen to me with ball bearing assembly. The
problem was that the balls were equally spaced around the bearing and
held in place by a plastic retainer affair. As long as the bearings
were equally spaced, everything worked just fine. However, if one
removes the plastic spacers, all the bearing fall to one end of the
bearing assembly, the whole thing falls apart. I managed to do that
with some solvent, which embrittled the plastic spacers when the
solvent dried out. When I spun the bearings at high speed using air
pressure, the plastic cracked and I had balls flying everywhere.

Blundering forward, I discussed the problem with a competitor (who is
conveniently located next to my office). He mentioned that he has had
problems using compressed air to clean CPU fans on MacBooks. When he
uses compressed air, and overspeeds the fans, they usually work when
he's done. A week or two later, the customer returns with complaints
about fan noise. I've seen this exactly once with a PC laptop CPU
fan. What seems to be happening is the high speed causes heating,
which then causes the dried out oil to reflow. Centrifugal force
redistributes the oil away from the main shaft bushing, where it again
dries out. That leaves the shaft dry and unlubricated. The reason I
haven't seen it much on PC laptops is that I usually lube the CPU fans
on laptops with "turbine oil" even if they seem to be working
normally. I can spin those all day long, and the oil will remain
fluid and functional. I learned long ago that this prevents return
visits and complaints.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558