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600 PSI T piston choices and recommendations.

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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600 PSI T piston choices and recommendations.

Unread postAuthor: boyntonstu » Sun Sep 06, 2009 7:13 am

Knowing what you have learned from experience, how would you go about building a T piston for a 3/4" or a 1/2" copper barrel?

Would the T size be 1" or 3/4"?

Threaded or soldered?

Would you use a hose adapter seat or copper tubing?

Would you use a screw/washer or a molded piston?

Epoxy, Bondo, or other material?

Is there a wear factor to consider?

Tapered seal to reduce dead space or flat seal?

There are so many variations out there and I would like to use an efficient proven design.

What really matters in the design that needs maximizing or minimizing?

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Unread postAuthor: Technician1002 » Sun Sep 06, 2009 9:28 am

For 600 PSI, I would use materials built for the job. Common soldered fittings are not up to handling 600 PSI and mechanical stresses of supporting a barrel, recoil, and piston impacts. I'm not sure the copper is up to the task either. I would move up to welded maluable iron and even avoid a cast iron T. If you do use those materials, may a recommend full body armor?

Most materials listed are not suitable for use at high pressure.

This is my opinion. It may be incorrect, but it's my opinion.
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Unread postAuthor: absinthe » Sun Sep 06, 2009 10:08 am

the thicker copper pipe (type A in AUS, 17g wall thickness) in a 3/4" pipe is rate to a max working pressure of 806 psi.

The normal water pipe (type B or the standard stuff, 19g wall thickness) in the same diameter is rated to 575 psi so go the thick walled copper and you will be fine :)

also i would think that all the brass fittings are rated at much higher than the pipe.

although all the ratings would be based on constant pressure not quick changes but with 200 psi of head room (useing the heavy pipe) you should be fine...

i have 2 copper guns made from standard copper pipe and i take them to 500 psi all the time (75psi below the max safe working pressure for the pipe) and have had no probs.. i use copper olive fittings with epoxy to help seal (no solder to weaken the pipe) and have a brass screw piston with a rubber seal and have had no problems
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Unread postAuthor: Hotwired » Sun Sep 06, 2009 1:02 pm

600psi hm?

We had a natter about copper pipe pressure a while back elsewhere.

Those would be UK standards of course but there's no reason for Amercian plumbing pipe to be significantly thinner.

So as far as proper working pressure is concerned you're fine.

I'd go one size up from the maximum barrel size you're using for the valve.

Soldering/threaded... You'll want an accessible section at the pilot side to allow fishing out of the piston as and when it malfunctions, not necessarily threads mind you. But properly soldered fittings should take 600psi.
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