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Audi bomb recharge procedures

I've noticed a bit of traffic on the subject of the Audi bomb and
finding a suitable replacement.  In late 1997 I developed a simple and
inexpensive procedure to retrofit the bomb with a high pressure
schraeder valve so that the bomb could always be recharged with nitrogen
gas.  Russ Sutherland uses this procedure as well.  I'm happy to report
that all of the bombs I have retrofitted with valves are still operating
nearly two years later.  Here is the original post.

>Good news Audi fans--the audi bomb can be turned into a rechargeable
>unit--for only $15 in parts and nitrogen charging fee (mine ran
>$20--mostly because of the time it took him to set up all the
>adapters--yours could be even cheaper).
>Here's how to do it.
>1.  Drill a 1/8" pilot hole in the top of the bomb, about half way
>between the edge of the top stub fitting and the rounded shoulder of
>bomb.  This is a very critical maneuver since you don't want to
>the bladder inside--which is usually fully inflated due to no gas
>pressure in the bomb to resist it.  The casing is about 1/4" thick so
>ease up on the dril and go very slow at the end.  The bladder is pretty

>thick so it will take a little damage, but don't press your luck.
>2.  Take the dull end of another slightly smaller drill and push it
>the hole to apply pressure to the bladder--this will start to push out
>the Pentosin inside the bladder.  Keep pushing inward until all of the
>fluid is out and the bladder no longer comes back up (it will tend to
>collapse and partially invert itself.  Now you are ready to drill a
>larger hole so that you can install a high pressure schraeder valve.
>3.  I used a standard sized schraeder valve (same size as an automobile

>tire valve).  You can buy them with various threadings on the insertion

>end of the valve.  Mine had a 1/8" pipe thread.  So I drilled a 5/16th
>inch hole through my pilot hole, then inserted a small cylindrical
>magnet to pull out the metal filings.
>4.  Thread the hole with a 1/8 pipe thread tap, and then remove any
>additional filings.
>5. I used epoxy (JB Weld is the strongest) as a thread sealer.
>I first cleaned up the cutting oil residue so that the epoxy would make

>a good seal on the threaded hole.  Then I roughed up the metal surface
around the hole and on the bomb surface around the hole so that the
excess epoxy would have plenty
>of grip.
>6.  After letting the epoxy set for 24 hours, I took my accumulator to
>my nearest heavy equipment dealer.  Heavy equipment companies usually
>have nitrogen charging equipment for charging the larger hydraulic
>accumulators that are used in big equipment.  I had him charge it to
>1150 psi (Bentley says between 1120 and 1180 psi.  The rule of thumb
>accumulators is 1/2 the working hydraulic pressure.
>7.  I got my high pressure schraeder valve at a hydraulic controls
supply house in
>Salt Lake City.  They cost between $10 and $12 dollars each.  It wasn't
easy finding one--I had to really search around until I found someone
who carried them.
>So, go out a get those bombs fixed and save yourself a lot of $$$.
>Hope that helps,  Joel Skousen
>Joel M. Skousen         <mailto:jskousen@enol.com>
>Joel Skousen Designs    WebSite: <http://www.xsw.com/securehome>
>290 W. 580 S.           Telephone:  (801) 224-4746
>Orem, Ut 84058