[R-390] Y2K Manual Question

Roger Ruszkowski flowertime01 at wmconnect.com
Mon Jul 15 19:44:25 EDT 2013


Don,

I think your post is correct.

We would like a little coat of something on the metal.
It is better that some replaceable renewable stuff be on the
surface  to oxidize and get attacked by nature rather than 
the metal its self.  Better that we have some additional lube
in the gears. A clean gear train is not a high friction device 
but a little lube will help more than running bear metal on
bear metal..

As gears wear, the lube will hold worm loose bits
in place just out of the line of friction and keep them from
getting back into pressure points and producing more wear.

Some of the dry lube gun stuff is considered a good choice for lube.
It is thought to collect less dust over time.

But hands down the  Mobile-1 is the 2013 lube of choice.

Its not what we think is good in an R390. It is what
science tells us about rubbing to chunks of metal together
lots and lots of times.


Roger.


-----Original Message-----
From: Don Reaves <donreaves at gmail.com>
To: R-390 List <r-390 at mailman.qth.net>
Sent: Mon, Jul 15, 2013 5:29 pm
Subject: [R-390] Y2K Manual Question


In the y2k manual, there is mention of two lubricants for the gear train
and slug racks.
One is MIL-G-7421, which is a grease and is easily identified on the net.
But the other is MIL-L-7970, which is likely a typo and should be numerals
7870.  MIL-L-7970 is a specification for mahogany plywood, whereas
MIL-L-7870 is a general purpose, stable at low temp., instrument oil with
anti-oxidation properties.  That part number is superseded by part number
MIL-PRF-7870.  7870[D] seems to be the last available revision and Royco
lists that oil as commercial part 363.  Anyone disagree with my conclusion
that 7870 is the proper citation?

The reason I ask is I am engaged in a discussion with a friend about the
merits of not applying any lubrication to the R-390A gear train after
cleaning up a dirty mechanism.  He likes dry, I like a little Mobile-1.  I
was reading through the TMs on the subject and discovered the mention of
these two specific lubricants and wondered what they were.

Don
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