Date: Sat, 19 Sep 2015 14:54:32 -0400
Reply-To: David Beierl <dbeierl@ATTGLOBAL.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Beierl <dbeierl@ATTGLOBAL.NET>
Subject: Re: Friday LVC: lubing old electric motors
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At 08:25 PM 9/18/2015, Edward Maglott wrote:
>This seems like a good question for David B. and
>others on this list. I like to fix old things
>up and use them or repurpose them. Old fans
>are one of those things. Usually they are AC
>fans you plug in to the wall, but this probably
>also applies to the DC fans in our vanagons. I
>can take them apart and get to the bearings,
>which are usually just a metal shaft in a metal
>bushing. I clean up the surfaces and lube them
>with some handy oil but this fix usually only
>lasts a little while. What is the best lube to
>use for this situation to get the most "revive
>time" between service intervals? I assume the
>bearing is actually worn and not fitting
>correctly and can never really be right again. Ideas?
>Edward
If the bushing is worn you'll know because it
will chatter, which is to say the shaft will roll
around the enlarged opening instead of rotating
smoothly in it. It will emit a mechanical shriek
of agony that on something more powerful than a
CPU fan will freeze your blood. This tends to
happen to sleeve-bearing computer fans after a
longish time, and to your average Black &
Decker-grade "Skilsaw" or similar after what
seems like about an hour of use. Short of
replacing the bushing (which on the power tool
you probably can) you can only pump the oil to
it, a drop or three before each use if
necessary. Computer fans will probably keep
going for months after you peel off the label and
flood the bearing, then stick the label back
down. 30-wt non-detergent oil for the saw,
machine oil or 10-wt non-detergent for the fans
(10-wt non-detergent for the saw, light machine
oil for the fans if they're not chattering).
Otherwise, the bearing has either gotten dry or
the lube has stiffened up or foreign material has
gotten in. Most "permanently" lubricated sleeve
bearings are porous sintered bronze permeated
with oil (the ones on the Bosch blower motors are
sintered steel, apparently). Ideally you soak
them in hot oil (?180F?) for half an hour. When
that's not practical, do the best you can. I've
gotten years of service from seized Bosch heater
blowers (that had not been cooked by leaving them
powered) by working them free with multiple
changes of Marvel Mystery Oil which has some
solvent in it, then running them unloaded on the
bench for a couple days with frequent attention
-- soak up the oil, add new, examine the
rag. Once the MMO starts coming back the same
color it went it, shift to name-brand sewing
machine oil (which is simply a high-grade light
machine oil). On the Bosch blower in particular
there are large felt pads pressed against the
bearings as oil reservoirs. Similar may or may
not be present on other motors. Next Bosch
blower I look at I'll think about re-oiling it
after freeing it up by suspending the end of the
motor in hot oil. The back end where that's more
practical (open frame, no protruding shaft) is
also the bearing that takes the beating on those
blowers from whatever grit is in the air
stream. Adding a cap to it seems advisable.
Yrs,
d
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