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Pneumatic rifle thingy finished... for now

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Pneumatic rifle thingy finished... for now

Unread postAuthor: saefroch » Fri May 07, 2010 6:57 pm

At 4' 9" long, it is somewhat unwieldy, but I am slowly getting comfortable with the size.

Specs:
Chamber: 18" long 3/4" galvanized steel NPT nipple
Barrel: 3' long 1/4" seamless stainless steel pipe
Firing valve: 3/4" tee piston valve- seals into 1/2"-3/8" galvanized steel bushing
Pilot valve: 1/2" ball valve- coefficient of kinetic friction drastically reduced

I utilized a few minor innovations/good ideas in this gun. Firstly, I soldered the schrader valve into a 1/4"-1/8" brass bushing. This attachment system works great, except I got overzealous and fried the rubber inside that makes the seal. No matter, with the firing mechanism, I do not rely on that making any sort of seal. There is a metering system that sits behing the pilot valve and also forms the stock that is used for firing, and also is pre-pressurized to kick the piston out of the stop that it always gets somewhat stuck in. The piston has a rear seal and two washers to brace the gasket rubber that forms the rear seal, thus eliminating any leakage from the chamber into the pilot.

EDIT: With the gun fully assembled the balance point on the gun is really close to the tee, so holding it like a rifle is actually quite easy and comfy :shock:

Damage pics and videos to follow. I have done some practice shots, but none with good ammunition yet.

Image
Schrader valve soldered into bushing

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Dismantled, piston valve lined up with parts

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Full gun assembled, sorry for the blur

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Priming/metering assembly

As you have probably guessed, I plan to adapt this into a low-mix piston hybrid. More modifications will follow, mostly due to suggestions and problems. Will post a thumbnail later tonight.

I will be adding more to this original post as I get a chance to take damage pics and vids.

Suggestions welcome!
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Last edited by saefroch on Tue May 18, 2010 8:22 pm, edited 6 times in total.
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Unread postAuthor: mark.f » Fri May 07, 2010 7:48 pm

Looks good, I assume you got your piston working well then?

Also, it looks like a dinosaur got ahold of that bushing/schrader assembly. :lol:
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Unread postAuthor: saefroch » Fri May 07, 2010 7:51 pm

Yeah, piston works pretty good but I still need to replace the sealing head every so often (washers too but they're good for like 15 shots now), takes a beating at 250 psi. A dinosaur? Just a pianist (I credit my massive grip strength to the piano) with a nice pair of pliers :twisted:
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Unread postAuthor: Crna Legija » Fri May 07, 2010 9:06 pm

veary nice but is the pipe comeing out of the second tee part of your pilot
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Unread postAuthor: saefroch » Fri May 07, 2010 9:17 pm

... is that a question? That random pipe is the stock actually, I chopped off the bottom threads because they got melted during from non-spudfiles discussible activites and were tearing up my clothing. That answer your question?
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Unread postAuthor: Crna Legija » Fri May 07, 2010 9:46 pm

not realy i ask if it is a part of your pilot volume
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Unread postAuthor: Gaderelguitarist » Fri May 07, 2010 10:03 pm

I credit my massive grip strength to the piano


And not something else that starts with "p"? :wink:

All things inappropriate aside, I'm glad you got your piston working, and am even more glad to hear that you'll be upgrading this into a hybrid.

From the pictures it looks as though the thing is crooked, starting at the main ball valve. A trick of the camera, I'm sure.
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Unread postAuthor: saefroch » Fri May 07, 2010 10:10 pm

In response to the first query, no it is NOT a part of my pilot volume. I inject about 160 psi into the volume between the two ball valves, flick open the forward one which produces a pressure spike enough to dislodge my piston and force it into the locked position with minimal barrel leak. Then I continue to pressurize until I reach the desire pressure, I then close the red-handles ball valve- my primary pilot- and open the rear ball valve, venting a lot of very cold air at my right leg. I can then disconnect the schrader connection and carry it around despite the fact that the rubber inside the schrader valve is fried. So the air from the red ball valve back is open at at atmospheric pressure, so the pilot volume just runs through there when fired.

EDIT: So the function of the schrader valve is not to be a valve, just a connection. It also leaves the gun as a fully closed system, which means I can finally pick it up and walk around without worrying about a tiny inaudible leak robbing me of firing power. That volume will also be my propane meter when I go hybrid.

Actually, it is crooked, but what you see is a trick of the camera indeed, the barrel fittings are crooked a little bit, what amounts to maybe a quarter of an inch off by then end of the barrel, but since it is crooked all the way down, a simple sight mounted on the barrel will fix any aiming issues.

Any questions?
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Unread postAuthor: Sch120PVC » Sat Jul 09, 2011 12:11 pm

Good design.....it would look even better with a good paint job and some accessories like laser attachment or sight! By the way wht is the performance on this desing???
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Unread postAuthor: MathiasDK » Wed Jul 13, 2011 2:16 pm

Why is there 2 Ball valves on your gun?
Sorry if its a lame question, but my english isn't that good.
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Unread postAuthor: far_cry » Wed Jul 13, 2011 3:07 pm

MathiasDK wrote:Why is there 2 Ball valves on your gun?
Sorry if its a lame question, but my english isn't that good.


when he fill it with air pressure ,he closed the rear one and open the red one , so can air go into the chamber ,then he closed the red one and open the rear one so can he use the red one to pilot the piston valve
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Unread postAuthor: MathiasDK » Thu Jul 14, 2011 8:32 am

far_cry wrote:
MathiasDK wrote:Why is there 2 Ball valves on your gun?
Sorry if its a lame question, but my english isn't that good.


when he fill it with air pressure ,he closed the rear one and open the red one , so can air go into the chamber ,then he closed the red one and open the rear one so can he use the red one to pilot the piston valve


does it have to be built with 2, or Can u make one with 1 Ball valve
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Unread postAuthor: saefroch » Thu Jul 14, 2011 2:35 pm

You could build it with one ball valve. I just opted for two, it seemed easier at the time. I still like the design.
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