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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
Comments: To: Edward Maglott <emaglott3@gmail.com>
In-Reply-To:  <CABToOY+p5L3991Qei8ogtroBTTrAQVp6OBzj1yy9LXLFNQYDqw@mail.g
              mail.com>
Content-Type: text/plain; charset="iso-8859-1"; format=flowed

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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