[Milsurplus] Re: [armyradios] Dynamotor brushes

[J Forster]

It occurred to me there are other ways to get a stuck brush out, if the brush is
expendable. Driving it out requires removal of the armature or removal of the
brush holder assembly from the machine frame.

Method one is to drill the brush out radially inwards using a twist drill somewhat
smaller than the brush minimum dimension. Since graphite is pretty soft, I think
this could be done by holding the drill in a pin vise and rotating it by hand.
You'd want to put a stop on the drill to prevent commutator damage.   Once the
hole is done, the stresses might be relieved enough that the brush would come out,
or you might have to break it out with a small tool, like a screwdriver.

Another way would be to saw off the inside end of the brush next to the
commutator, if there is enough of a gap, then push the remaining part inwards and
repeat. Like slicing off a salami. A fine saw, like a cut down X-Acto Razor Saw
might work well.

FWIW,
-John



Clare Owens wrote:

> 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