[Milsurplus] Dynamotor Lubrication

[Clare Owens]

Hi Ken,

I run the dynamotor at low speed while flushing the bearings using 5V or so
for a 24V dynamotor.  Can take a pretty healthy 5V supply.  Seems to help
mix up the solvent and old grease.  I've also squirted some light model
railroad lube into the bearings, closed them up and run the dynos for a few
minutes at about half voltage to mix things up.  That works pretty well too.

OK, here comes the heresy:  I bought three or four tubes of SHC-100 (had to
buy the minimum $ worth) back in about 1996.  I lubed one dynamotor with it
- lovely red stuff - and put the tubes on the shelf for later.  A few months
later I discovered it was separating into nice red oil and some soapy stuff
and consequently leaking all over the shelf.  I put the tubes into a plastic
bag and watched the oil flow out slowly over several more months until the
drying of the soapy stuff was very evident.  Then I threw the whole mess
out.  Maybe SHC-100 is OK for bearings that are used often but I won't be
using it any more for my dynamotors, which aren't used much at all so far.
I have two synthetic greases that have been on the shelf for three or more
years and have not separated at all, Chemplex 940 (online ordered) and
Valvoline Synpower Synthetic Grease (from Advance Auto Parts).  I have only
used the Chemplex - it is a silicone/lithium grease and is specifically said
to be for high temperature bearings and is safe for most materials.  The
Synpower is a lot stiffer and is for high stress bearings in cars  I bought
it to see what it is like and to see if it would separate.

I don't see dynamotor bearings as being under a particularly heavy
mechanical load but they are high speed and the whole assembly will run
quite hot after running at full load.  I've run the 940 lubed dynos at no
load for several hours at a time and have only seen a slight warming of the
bearing covers, which could be from conducted armature heat anyway.

If I ever get this equipment in operation we'll see.  Come to think of it,
the Dynamotor in that DC-3's BC-348 is lubed with 940 and should be getting
some hours of use...

In any case I want to cast my vote for the best sounding dynamotor for the
PE-94/98 dynos used for the SCR-522/542.  Smoothness!  And having four
commutators also adds to the coolness factor.

Clare


On Fri, Apr 1, 2011 at 3:45 PM, Ken Kinderman <t47ecdab at gmail.com> wrote:

> Hello everyone,
>
> Finally getting around to collecting all my DM-32's,DY-8's etc. to check
> the
> brushes and lube the bearings.
>
>
> Opening the bearing cap at the end of the shafts reveals a kind of shield
> over the actual balls themselves. I can pick out the old grease with a
> toothpick, but can't get between the balls.
>
> Question: is this the limit of the access to the bearing? Seems like there
> could be a lot of crud on the inner side of the bearing that I could be
> missing.
>
> I am flushing the bearing carefully with mineral spirits while keeping the
> dynamotor shaft horizonatal so as not to let the dilute crud fall into the
> commutator.
>
> Is this the best that can be done? Or is there a secret to getting deeper?
>
> Using Mobil SHC-100.
>
> Thanks,
>
> Ken
> W2EWL
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