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Custom Aluminum Pneumatic Build

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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Unread postAuthor: gyrotech » Thu May 23, 2013 8:58 am

I will use heavy projectiles in the future. That's for sure. Golf balls are just so easy to come by for regular shooting.
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Unread postAuthor: mobile chernobyl » Thu May 23, 2013 10:24 am

Turn it into a piston hybrid then it might be fun! :D

Jokes aside - amazing work!
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Unread postAuthor: gyrotech » Thu May 23, 2013 6:28 pm

jackssmirkingrevenge wrote:Have a play with GGDT: http://www.thehalls-in-bfe.com/GGDT/

I figure that you probably won't see much reduction in performance if you chop the chamber in half, unless you're firing a reallly heavy projectile.


Played around with GGDT. Seems your absolutely right...

I'm still unsure if I'll cut it down. According to my calculations my air compressor will have it full in under 3 minutes. I have made the front of the piston valve so that I could interchange barrels, and perhaps take advantage of large bores for tennis balls or who knows what...

Decisions decisions...
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Unread postAuthor: jackssmirkingrevenge » Thu May 23, 2013 11:29 pm

As long as you're not pumping it by hand, I wouldn't be too worried. Nothing wrong with overkill unless pumping effort or noise is an issue :)
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Unread postAuthor: gyrotech » Sat May 25, 2013 3:23 pm

Update: She's coming along!

So Yes, I did end up cutting down the chamber.

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Unread postAuthor: jackssmirkingrevenge » Sun May 26, 2013 2:12 am

Looking good!

Have you thought about how it will be used, will it be hand held, shoulder fired?

[youtube]http://www.youtube.com/watch?v=X_pYB0fW6i8[/youtube]
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Unread postAuthor: gyrotech » Sun May 26, 2013 6:21 am

I'm thinking tripod with hand screw adjustment. Like a long range cannon.
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Unread postAuthor: velocity3x » Sun May 26, 2013 8:42 am

gyrotech wrote:I'm thinking tripod with hand screw adjustment. Like a long range cannon.

You might consider a muzzle brake as it will become an ill bread monster with increases in operating pressures.
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Unread postAuthor: jackssmirkingrevenge » Sun May 26, 2013 2:27 pm

Something like a recoilless rifle then :)

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Unread postAuthor: gyrotech » Sun May 26, 2013 3:28 pm

Yes :) exactly! Good pic!
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Unread postAuthor: gyrotech » Sat Jun 01, 2013 11:49 pm

Progress:
-Fitted the barrel. Which is a sleeved fit. The end cap with bolts hold the barrel in.
-Reworked the chamber-valve supports
-Finished the piston valve
-Cut gasket for piston side of valve
-Tested low pressure and holds air

Next:
-hydrostatic pressure testing at 350 psi to affirm safety of unit

-build new piston with check valve, so that air can flow past, and into chamber, but virtually no air can flow the opposite direction. My thought is this will improve the efficiency of the gun. The piston is a nice slip fit, but I made troughs to let air flow past when filling. I made them to big and it has lost some efficiency for sure.

-build trip-pod and firing device

Operating pressure planned to be 150-245 psi. 250 PSI blow off valve on the chamber. Depending on what I have to charge with at time of firing.

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Unread postAuthor: gyrotech » Sat Jun 01, 2013 11:54 pm

GGDT predictions. 150-245PSI with a 45 gram golf ball.

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Unread postAuthor: jackssmirkingrevenge » Sun Jun 02, 2013 4:35 am

Nice, looking forward to seeing this in action!

By the way since it's barrel sealing you can reduce the dead volume on GGDT to zero. Well technically since the projectile is spherical, it would be 0.7 cubic inches.
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Unread postAuthor: gyrotech » Sun Jun 09, 2013 9:01 am

Ended up changing the material of the piston to UHMW. Came out a lot lighter than the dense Acetal. Added in a make shift check valve.

The piston is such a nice fit, even without orings very little air can leak past. I'm happy with the end result. Should be very efficient.

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Hydrostatic testing at 150% max operating pressure: Pass.

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Testing next weekend.
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Unread postAuthor: finland66 » Sun Jun 09, 2013 9:18 am

Very very nice cannon :D
I like that piston
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