[ARC5] Re: [armyradios] Dynamotor brushes

[Brooke Clarke]

Hi Clare:

I have had good luck using Kroil penetrating oil on metal parts that have been 
stuck and it might work here.  Sure is worth a try.

Some chemicals that are handy:
http://www.prc68.com/I/FlashlightPat.shtml#CF

Have Fun,

Brooke Clarke
http://www.prc68.com/P/Prod.html  Products I make and sell
http://www.prc68.com/Alpha.shtml  All my web pages listed based on html name
http://www.PRC68.com
http://www.precisionclock.com
http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Web Cam


Clare Owens wrote:
> I'm in the process of fixing up the DM-28 dynamotors I bought at the
> CC-AWA Conference a week ago.  One of them was essentially unused and
> the grease softened up nicely with some light oil.  It ran fine for
> 1/2 hour last night, no trouble at all.  But the other one has seen a
> lot of wear, lots of carbon powder in the housing, rough feeling
> bearings and one LV brush is stuck tight.. Really tight.  I have
> removed the LV end bell and while I was cleaning the bearings I
> removed the brush holder and applied motor cleaner then soaked the
> holder in Acetone and now have applied a lot of force in both
> directions with no results except a little chipping.  I guess I'll
> have to destroy it to get it out.
> 
> The good news is that I just looked in my box of very old brushes and
> I have an envelope of unused spares for all four brushes.  The part
> numbers on the envelopes match the parts list numbers for the brushes
> for the DM-28 for the BC-348-H anyway.  This one was from an "O" but
> should be the same, no?
> 
> But before I destroy this brush, does anybody have any other method to try?
> 
> Also this brings up the question:  Why are they so specific about the
> positive and negative polarities of the brushes?  They have different
> part numbers, there are plus and minus signs molded into the housings,
> etc.
> 
> What difference could polarity make in a graphite brush?
> 
> Also, I just have to comment on the high quality of design and
> manufacturing of these units.  The dynamotor innards I have seen over
> the years all have been remarkable examples of how to build a device
> that would work well under harsh conditions and last for many, many
> years.  They make the insides of most of my modern electric tools look
> like junk.
> 
> Thanks,
> 
> Clare  N2RJB
> 
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