Re: bomb recharge procedure???

[Eric Maxon <emaxon@megsinet.net>]

Phil and Judy Rose wrote:

> >Date: Mon, 1 Dec 1997 00:46:13 -0800 (PST)
> >From: Orin Eman <orin@WOLFENET.com>
> >Subject: Re: bomb recharge procedure???
> >
> >> >Anyway, when folks talk of the bomb being at 2000 psi I guess that
> means
> >> >its _initial_ pressure; and that new bombs are shipped dry (empty
> of
> >> >hydraulic fluid) at first? If so, the "membrane" needs to be
> pretty rigid
> >> >to be able to retain that initial nitrogen charge against merely
> >> >atmospheric pressure (?). I hadn't thought about that before this
> thread.
> >> the "membrane" needs to be flexible enough to stretch to the
> opposite
> >> wall until a sufficient quantity of incompressible fluid (hopefully
>
> >> pentosin) is pumped into the empty side of the chamber...
> >
> >The natural shape of the diaphragm is probably close to that of the
> >wall and in the 'dry' state, pressed agains the wall.  Only the
> >section against the hydraulic oil inlet may be taking the full
> pressure
> >unsupported.  I say may because it will undoubtably be reinforced
> >in this area and may well have a metal insert at this point.
> >(The picture in the Bosch automotive handbook shows what it
> >calls a 'plug' at this point.)
> >
> >The Bosch automotive handbook also notes "the pressure variation
> >between  the initial gas pressure and the maximum operating pressure
> >should not exceed 1:8 for diaphragm accumulators".
> >Or, to paraphrase a little, dry, the gas pressure is considerably
> >less than the system operating pressure.
>
> So the arrangment is actually more like a sphere within a sphere? Hmm,
> I
> had naively assumed that the membrane divided the accumulator into
> more-or-less equal volumes. Does the Bosch handbook state the initial
> pressure?
> Also, what _is_ the nominal value (or range) of "operating pressure"?
>
> Phil
>
>          **********************************************
>          *  Phil & Judy Rose     E-mail:              *
>          *                       pjrose@servtech.com  *
>          **********************************************

   I missed most of this thread, but refilling, or in any way attempting
to repair a dead "bomb" seems ludicrous to me.

warning... commercial message comming up...
I sell them for $250, NEW.  (manufactured by Lemforder Metallwaren of W.
Germany.)
end commercial message.

So your bomb is dead... Where do you think the gas went??  Unless you're
talking about a 20 year old Citroen that's been rusting away in some
junk yard for 20 years, the gas most likely leaked through the thin
septum/inner sphere into the hydraulic system, not through the thick
metal outer shell of the sphere.  Even if you have the equipment and
wherewithall to cut the bomb open, weld it shut properly, weld a gas
fitting onto it, and fill it with gas, where the hell are you going to
get a new septum?

When these babies fail, they usually still have plenty of gas pressure
inside, but they don't work right because the check valves are clogged
with dirt.  The valve body is "permanently" assembled-- another can of
worms.

I still have a couple of bombs here with stuck check valves, and will
someday attempt to flush the valves with my Bosch K-Jetronic fuel
injector tester/cleaner-- If this doesn't work, I'll throw them away.
If you want to spend $400 on this machine, you can try it too-- or just
get a new bomb for $250!  (oops.. more commercialism.)

Provided the check valves work properly, here's your shopping list for
repairing a depressurized bomb:

Used MIG welding outfit, with filled nitrogen tank and lines:
$1000-$1500
Lots of practice using above:   6 months of spare time (pricele$$)
Crash course in conversational German:  $250
Round trip extreme bargain airfare to German city of your choice: $400
Rental of appropriate car in Germany for 1 week: $1000 (hmmm...maybe an
S4?)
Food and lodging in Germany for 1 week:  $200 (sausages, beer, and the
back seat of the S4)
Wining and dining of Lemforder executive:  $500
Replacement parts for your dead bomb:  Free (see above)

Okay... now you're ready to begin : )

Good luck!

Eric Maxon "The Manicured Mechanic"
Chicago, IL
('86 5000cs, '84 4000s, '82 4000s, '84 VW GTI, '80 VW Scirocco)