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! :-)

There is a 3/4-27 UNS thread listed.

On Sat, 8 Oct 2005 06:51:12 -0400, "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! :-)




That'll be 3/4 Gas thread


Mark Rand
RTFM

I'm guessing pipe thread, possiblly NPT. 3/4" pipe thread isn't 3/4"
in diameter, though. Look on a thread chart that has the actual major
and minor diameters.

it is 1/2 NPS (Nation pipe straight ) i have bp
"DOC" wrote in message
...
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! :-)

Thanks to everyone who helped out on this.

The short answer seems to be that there IS a 3/4-27 thread.

The longer answer goes like this...

I took a harder look at "Machinery's Handbook" and there are more
threads than you'll ever want to deal with.

They show a 3/4-27 UNS thread and suggest that UNS not be used unless
other threads "do not meet requirements". I don't know what's so special
about this CO2 cylinder but...

It isn't metric. The closest metric pitch is .09 and 27 TPI comes out as
..094
( 25.4/27) And 27 is the correct # (Using thread gauge.)

It isn't NTP. While NTP does have a 27 TPI, it's down at the 1/16" size.


Now all I have to do is find or make a 3/4-27 tap! :-)

DOC



wrote in message
. ..
it is 1/2 NPS (Nation pipe straight ) i have bp
"DOC" wrote in message
...
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! :-)

DOC wrote:
....
Now all I have to do is find or make a 3/4-27 tap! :-)
....

Do a good job: the vapor pressure of CO2 at room temp is about 800 psi,
IIRC. You don't want your home made fitting popping off! Bob

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."

They look like inflators for life vests or rafts. That's about the
only thing I can think of with that small a capacity. The thread is
probably British, but might be something proprietary if it's
ex-military.

You might want to rethink your power source. Figure out how many cubic
feet of gas you're going to get out of the volume of liquid CO2 that's
contained in those cylinders. It probably isn't as much as you'd like.

Stan
Stan

xray wrote:
On 9 Oct 2005 14:48:12 -0700, wrote:


They look like inflators for life vests or rafts.


Maybe the printing on them saying, "Cylinder CO2 Life Jacket", gave you
some hint of that.


Hey, givem a break! I bet 9 out of 10 folks here who looked at the photo
missed seeing those words there until you pointed it out to us. I know I
did.

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

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