[R-390] Gear lube suggestions

[Bob Camp]

Hi

In order for an oil to not degrade at all you need to have two things going on:

1) The oil does not cross link (polymerize) in the environment
2) No dirt at all in the environment 

The first one is a lot easier than the second one. 

Practically you need one more feature

3) It does not evaporate

A lot of the stuff that meets rule 1, fails rule 3 (it's a light weight oil with a low(er) vapor pressure).

Bob

On Jul 16, 2013, at 9:19 PM, Gary Pewitt <garypewitt at centurytel.net> wrote:

> Since the unavailability of whale oil, which was totally non gumming, the only substitute is Jojoba oil, which is also non gumming.  It's really good stuff.
> 
> 
> On 7/15/2013 9:28 PM, Roger Ruszkowski wrote:
>> 
>> 
>> 
>> -----Original Message-----
>> From: Charles P. Steinmetz <charles_steinmetz at lavabit.com>
>> To: 390 list <r-390 at mailman.qth.net>
>> Sent: Mon, Jul 15, 2013 8:12 pm
>> Subject: Re: [R-390] Y2K Manual Question
>> 
>> 
>> Don wrote:
>> 
>>> 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  That part number is superseded by part number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?
>> Good detective work!
>> 
>>> He likes dry, I like a little Mobile-1
>> I have used both light oil and dry graphite with good success (when I
>> use graphite, I apply it dry, not in a solvent carrier -- I found
>> that the graphite left after the solvent evaporated did not lubricate
>> nearly as well as graphite applied dry).  The primary application for
>> graphite is in very dusty locations (sandstorms, etc.), where the
>> dust can get caught in oil to form an abrasive paste.  This may be
>> why your friend doesn't use oil.  If so, he should consider keeping
>> the radio room cleaner (if dust getting caught in the oil is really a
>> problem for him) or using graphite.  You can get by with an
>> unlubricated gear train, but it is not the preferred solution.  (I
>> have only once or twice seen a 390/390A used by a ham or SWL where
>> dust in the oil was a problem, out of several hundred units.)
>> 
>> When using oil, the lubricity demands are not high -- the tuning
>> mechanism is very lightly loaded -- so you don't need extreme
>> pressure or high-speed additives.  The most important criterion is
>> that it be non-gumming over long periods of time and at somewhat
>> elevated temperature.  Second is some corrosion inhibitor, given the
>> different metals used in the gear train.  I'm sure there are many
>> oils that fit this description.  I've been using and recommending
>> Mobil 1 for 390/390A gear trains (and many other uses) since the
>> mid-'70s and it is well-proven.
>> 
>> I have generally avoided grease of any sort, because until very
>> recently there weren't any that were as gum-resistant as a fine light
>> synthetic oil.  There are some specialized greases available today
>> that meet the requirement (e.g., some of the DuPont Krytox products),
>> although the ones that do are quite expensive and I see no benefit
>> generally to grease over light oil.
>> 
>> Best regards,
>> 
>> Charles
>> 
>> 
>> Amen,
>> 
>> Good stuff Charles
>> 
>> Roger
>> 
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> 
> 
> -- 
> Gary Pewitt   N9ZSV
> 1500 French Prairie Rd
> Booneville, AR  72927
> 
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