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Re: compressor fittings

To: Douglas Shook <shook@usc.edu>
Subject: Re: compressor fittings
From: Scott Hall <sch8489@garnet.acns.fsu.edu>
Date: Sun, 16 Sep 2001 02:01:31 -0400 (EDT)
On Sat, 15 Sep 2001, Douglas Shook wrote:

> I have never seen a fitting like what you have
> described, I am surprised that a rubber o-ring could
> survive the temperature.  

I've been marvelling at that very thing.  especially considering your
problems.  and this thing is *in* the pump head essentially.  at first I
thought it was metal or composite, but it stretches right on and off the
copper pipe I've been trying to get into the pump.

> Is the female fitting on the head threaded into the
> head?  

nope, cast right in as near as I can tell.

> Could it be removed and replaced with a normal
> 1/2" female compression fitting?

no, but I was thinking maybe I'd try to fit a separate plug adapter into
the female thread, then put a compression fitting onto that.  the area
around the female fitting is flat enough that I think it'd work, let the
flat seal with a washer or something.  thing about that is the thread of
the female fitting--nobody seems to know what it is.  it's very coarse,
and to boot there aren't very many of them, maybe 3/8" or so.  I'm
starting to worry it's like the screw that come on my jack handle--when I
tried to get a replacement nobody could identify the thread and the
fastener supply house said it was probably some unique thread the far-east
jack company used.  if it comes down to it I might try to get a plug made
up; I don't see why a machine shop couldn't copy the thread.

> If not, could you drill it and tap it out for a
> compression fitting?

which was what I was thinking...but that would probably require me taking
the head off and that'd be the point where I think the owner should screw
it up on his own...  if it needs a gasket replaced, or if the tap is
off, etc...

> Failing this, I would be tempted to braze a standard
> 1/2" female fitting to the existing fitting if it
> cannot be removed (assuming it is bronze, brass, cast
> iron, etc.).
> 
> If it is aluminum, it gets more complex, but still
> might be "doable."

it is, in fact, aluminum.  or at least a magnet won't stick to it and it's
somewhat corroded so I suspect it isn't stainless.

> I did a quick search on "dental air compressors" and
> came up with a few urls -- maybe something here could
> help:
> 
> The search came up with several dozen hits.

this thing is probably close to 20 years old.  it's got a horozontal tank
and the pump is one unit that looks very much like what I imagine an old
air-cooled bmw boxer motorcycle engine would look if it were a six.  the
pump runs the length of the tank.  I didn't see anything quite like it on
those pages, but man, how 'bout the puma and champion compressors? 

> Don't you hate it, though, when this happens? 

yes.  very much.

> I have done very similar things trying to help somebody, then
> realized 1/2 through that it has become a much bigger
> job than I expected, or wanted, but once you drill the
> hole in the bottom of the boat, you don't have much
> choice but to fix it or keep on bailing.  ;)

that may be the most perfect analogy for these projects I've yet heard.
;-)

this same guy's honda vf700 is *still* in my garage.  the vf is the v4
series--you know, the one with the carbs crammed together so that you need
your fingers to grow a foot and several extra joints and become as thin
as pencils to get to the carbs, after you remove the insanely fastened
bodywork?  he let the tank rust through whereupon it dropped massive
chunks of rust into said carbs.  I *hate* honda v4 carb setups.  then
there were the wiring problems, the battery that exploded and dissolved
most of the stuff near it (like the battery cables), the freakish shaft
drive problems, the...

this thing made it into my garage one fall morning with the diagnosis:
"won't start, think the battery's dead."

the only way to get that thing gone (I thought) was to fix it, one surreal
problem at a time.  I should have known better once I got the seat off 
and saw (the remains of) the battery, but noooooooo, I took it in...

it's done now, but it's still in my garage, waiting...

scott

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