No Subject

[Phil and Judy Rose <pjrose@servtech.com>]

>
>Date: Wed, 26 Nov 1997 10:20:02
>From: Mike Arman <armanmik@n-jcenter.com>
>Subject: bomb recharge procedure???
>
>Let's think about the bomb for a moment: Essentially it is a metal sphere
>with a rubber diaphragm in the middle. One side has pentosin in it, the
>other has nitrogen at 2,000 psi or so. Failure mode is that after a few
>years the nitrogen diffuses through the diaphragm, and pressure assist is
>lost. The diaphragm itself MAY not be torn or defective, and if there were
>a way to replace (recharge) the nitrogen, the bomb would be OK again (per
>Citroen "recharge" comments earlier).
>
>Oh, how I would like to see the following procedure:
>
>Bomb recharge, first time:
>
>	1. Release pressure in bomb by pumping brake pedal as needed.
>
>	2. Remove bomb from car, clean well.
>
>	3. Drill 1/4" hole at location X, screw/braze/otherwise attach high
>pressure schrader (tire valve) fitting in place.
>
>	4. Charge bomb to 2,000 psi, close valve/screw/whatever.

[snip]

>The keys here seem to be the installation of a valve to replace the
>nitrogen, and the procedures for handling 2,000 psi nitrogen. The valve
>would have to be installed in such a way that the diaphragm would not be
>damaged, and in such a position that the valve could be accessed without
>removing the bomb from the car. Handling nitrogen at 2,000 psi is not a
>major problem - think welding tanks. Nitrogen in tanks is available from
>the local industrial gasses supplier or welding shops, this CAN'T be that
>difficult!!!
>
>Food for thought?????????

Yes, definitely food for thought. I've been having similar thoughts over
the past week as I need _two_ bomb replacements (one will be under
warranty). I'm sure others have speculated much on this issue.

I imagine that Audi had also given that approach some thought, but one
reason it's not done probably has to do with the difficulty of engineering
a small valve for recharging at 2000 psi. While that pressure is routinely
available and handled well by gas cylinders and their valves, the valves
are pretty beefy hunks of brass. Something along the lines of a Schraeder
valve would be pretty ambitious for that pressure. Might need monthly
recharging. :-( Does Citroen actually produce a rechagable system for such
pressures?

Hard to believe that--nowadays--a more suitable synthetic rubber membrane
with lower permeability towards nitrogen is not available. Actually it most
likely is available, but the market for long-life pressure accumulators
probably just doesn't justify the development cost.

BTW, anyone give some thought as to the ultimate fate of all that nitrogen
that dissipates through the membrane and dissolves in our Pentosin. Somehow
our Audis manage to avoid a severe case of the "bends". Or _do_ they? Maybe
rack failure has something to do with nitrogen outgassing...?

Phil
'91 200q
'89 100

         **********************************************
         *  Phil & Judy Rose     E-mail:              *
         *                       pjrose@servtech.com  *
         **********************************************