DOC wrote:

I recently picked up some CO2 cylinders which I want to use as the
power source for small combat robots. Think flipper, hammer...

Couple pics he
http://www3.sympatico.ca/doc/co21.jpg
http://www3.sympatico.ca/doc/co22.jpg

I make the external thread out to be 3/4-27. That's something
I've never heard of! Proprietary?

The things are made by the Walter Kidde Company Limited and, although
unused, say "Made in England 1958", "Part No. WKA25533"

Can't find anything on the web.

Any idea what kind of fitting this is?

Tanks,
DOC

Small pun intended! :-)




Forgive me for sounding like a spoilsport, DOC, but high pressure gasses
can become serious dangers.

I've probably told this tale here before, but it seems appropriate to
tell it to you. I lost a SCUBA diving buddy back around 1960 when he
used a cast iron 3/4" NPT to 1/2" NPT reducing bushing to adapt a SCUBA
valve onto a CO2 fire extinguisher bottle. He likely would have been OK
with a brass or steel bushing, but cast iron wasn't up to the task and
the threads sheared off while he was filling the tank. The 1800 psi air
blew the valve up through his chin and into his brain.

Whatever you do, If those 47 year old tanks haven't been recently
tested, they, and whatever adaptors you end up with to mate with those
threads, should damn well be recertified by a qualified place before you
fill them with CO2. That should include hydrostatic testing in a vessel
which will measure the "expansion and contraction" of the tank. Fire
extinguisher shops have that kind of equipment, that's where we used to
take out SCUBA tanks.

Just my .02, but if it was me I'd consider retiring those antique tanks
and buying some new paintball gun cylinders for your combat robot, the
fittings for those are readily available, and they're made to stand up
to the rigors of being bumped and dropped by the paintball players.

HTH,

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."