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So, I am going to attempt my first piston valve.

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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So, I am going to attempt my first piston valve.

Unread postAuthor: Intel Xeon » Mon May 14, 2007 9:35 pm

I was wondering if i could get some feedback as to whether I am going to blow myself up or not.

Parts:

2" Tee, socket

2"x1" Bushing Spigot x Socket

2" Plug, slip

Hot Glue (for attaching things, and piston itself)

1/8" Neoprene sheet

2" Elbow (to mount the chamber)

4" compression spring

Blowgun

1/4" npt Coupler (male)

2" pipe (obviously)

Rotary tool, Drill with bit set, primer and cement, two part epoxy)



Is there anything missing?
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Unread postAuthor: Velocity » Mon May 14, 2007 9:47 pm

Well if I were you...

I would use a 2" x 1.5" bushing instead of the 2" x 1"... it is just as easy to build, and will yield 2.25X the power.

Instead of using a 2" plug, use a small piece of 2" pipe, a 2" female adapter, and a 2" threaded plug. You can tap a hole into the 2" threaded plug to attach a pilot valve, or you could just buy a 2" x 3/4" bushing and attach your pilot valve to that. This way, you can access the piston if it breaks or isn't working properly (and considering that it is your first piston valve, it will have some initial problems; everyone's does)

You do not need the spring; just fill from the pilot side of the valve. It just as easy, and it will seal the piston against the barrel port more reliably.

Cut a washer of the neoprene rubber, and attach it to the barrel port. Also attach a circular piece to the front of the piston. This will ensure a very good seal; I use this technique on most of my piston valves.

A blowgun might not be able to pilot the piston valve (considering that it does not have o-rings). I would also buy a 1/4" ball valve, because that WILL be able to pilot a valve of this size.

You do not need epoxy; the hot glue should suffice for both the piston and gluing the washer of neoprene rubber against the barrel port. Do not buy the epoxy with the intent of sealing up any leaks; if a piston valve leaks, it is probably a good idea to start over (unless its from a threaded porting, because then you can just use Teflon tape), because with such forces involved, you do not want to rely of epoxy for safety.

If you have any specific questions, feel free to PM me; I am glad to help.

EDIT: Forgot to mention... a good bumper is necessary, especially for larger piston valves such as this one. I personally have found that a few short strips of air tubing glued to the back of the piston work wonders when done correctly.
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Last edited by Velocity on Mon May 14, 2007 9:55 pm, edited 1 time in total.
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Unread postAuthor: keep_it_real » Mon May 14, 2007 9:51 pm

I was wondering if i could get some feedback as to whether I am going to blow myself up or not.


In that case you'll need a bumper (was that what the spring was for?). Some people use half a tennis ball. Maybe a piece of tubing...
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Unread postAuthor: jrrdw » Mon May 14, 2007 9:51 pm

Yea, the blue print. To go along with the menu. Some thought out details on how you plan on building it.
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Unread postAuthor: Intel Xeon » Mon May 14, 2007 10:05 pm

I see the sense in the threaded cap, Rmich. Thanks for the info all of you.
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