[Milsurplus] Re: [armyradios] Dynamotor brushes

[Clare Owens]

Well, I ended up driving it out.  I tried heating it with my heat gun
and pressing on it, tapping on it then just drove it out.  Finding
that I have not 4 but 8 sets of the DM-28 LV brushes plus one extra
helped me make the decision to drive it.  It's been running for about
3/4 hour now on my bench and seems to be doing fine.  I searched the
drawer of #6 screws and found 3 end cap safety wire screws and one
very similar so I can attach the caps properly.  Not the best looking
unit but someday it'll be inside a radio where it won't show.

If anyone is desperate for a set of the LV brushes I could spare a
couple of sets.

I have liked to work on small DC motors ever since my father showed me
how when I was quite young.  I showed our three children and soon
it'll be time to show the grandchildren.  I have lots more dynamotors
that could use a tune up after 60+ years.

Thanks for all of the suggestions.

Clare  N2RJB

On Sun, Mar 30, 2008 at 3:11 PM, Brooke Clarke <brooke at pacific.net> wrote:
>
>
>
>
>
>
> 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