[R-390] Cleaning Gears & Cams

[tfrobase]

The mass incorporated in the mechanical mechanism of an R-390 is rather
large to be effected in an ultrasonic bath for the period of 3-5 minutes.  

The goal is to leave it in just enough time for the detergent, excited by
the ultrasonic waves, to soften and remove the old grease and dirt without
effecting the paint and other markings.  As for stripping the anodizing off,
I am not sure, other than maybe couple of the gears that there is any.  The
major aluminum components in the R-390A use an iridite yellow chromate
finish which is conductive, unlike anodizing oxide which is an insulator.
Maybe it could strip the iridite off, but I have seen no indication.  I'll
try your aluminum foil test and give you a report ... Tom, N3LLL

-----Original Message-----
From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
On Behalf Of ToddRoberts2001 at aol.com
Sent: Saturday, November 19, 2005 5:34 PM
To: r-390 at mailman.qth.net
Subject: Re: [R-390] Cleaning Gears & Cams

In a message dated 11/19/2005 12:05:55 PM Eastern Standard Time,
chacuff at cableone.net writes:
Ultrasonic cleaning is a good way to go if you have one big enough to fit
something as large as the gear train in.  I wish I did....
I guess it gets the gunk in between the split gears..have you ever pulled a
pair apart after a cleaning to see what is left between them?
Cecil

I have been doing some research on ultrasonic cleaners. It seems they can
damage aluminum parts in a process called "embrittlement". A standard test
for ultrasonic cleaners is to immerse a piece of aluminum foil in the tank
for a few minutes - the foil will be peppered with pin-prick holes that were
blasted into the aluminum. If you leave the aluminum foil in the tank for 30
minutes it will be pulverized. Also have read it will strip the anodizing
right off of aluminum. Supposed to be okay for steel parts though. Also read
that ultrasonic cleaners will dull threads and dull the edges of sharp tools
like scissors. 
Not sure if it's worth the risk? Maybe safe if used for just a few minutes? 
Sounds like a great way to clean an R-390A geartrain but don't want to risk
damaging parts. Guess I will stick with using a kerosene soak and bath for
now until I know more. 73 Todd - WD4NGG
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