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Will this design work?

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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Will this design work?

Unread postAuthor: dilweed » Mon Jun 22, 2009 6:55 am

Hello,I will be leaving for my family cabin in Montana this Friday instead of being cooped up in darn ol' london, so I will have plenty of space and time to build a more powerful air gun. The following drawing is my first attempt at creating a piston valve air gun. Please add constructive criticism, tell me if it would work. Basically its a piston valve actuated by a burst disk. Hope my drawings clear enough! lol.
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Unread postAuthor: spudtyrrant » Mon Jun 22, 2009 7:09 am

ummm yeah but you have to know a little about both valves before you try it first of all shrapnel from your burst disk can be very dangerous at close range sometimes they will imbed themselves in a target(so towards your face or body isn't a good idea). but if you really want to have a hammer actuate it i would make a push button valve put it in place of the burst disk. what i would do is get rid of the spring and make one that uses a normal pilot but thats just me :wink: ps: there is no need for the equalization port
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Unread postAuthor: dilweed » Mon Jun 22, 2009 7:13 am

thanks but my mechanism to actuate it is a little different now. you have a threaded endcap filled with dried glue. you pull back the hammer behind it, pull the trigger, and the needle on the hammer puntures a small hole in the cap. This releases a small stream of air, not to explode the cap. When shot, unscrew cap, screw in new one etc.
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Unread postAuthor: inonickname » Mon Jun 22, 2009 7:19 am

If you're going to go to the trouble of using individual burst disks for each round then why not use a burst disk as a main valve?

Porting a piston with a burst disk will give no performance increase compared to say a QEV.

Edit: By the way, the scale of your gun is massively out of whack.
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Unread postAuthor: dilweed » Mon Jun 22, 2009 7:21 am

I know its unscaled.

But Im building this for power AND looks, so I want it looking like a real fire arm.
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Unread postAuthor: inonickname » Mon Jun 22, 2009 7:31 am

Exactly. A hammer valve to port it will work just as well depending on size.

As a note for the scale, the barrel needs to extend well over the chamber port.
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Unread postAuthor: spudtyrrant » Mon Jun 22, 2009 7:31 am

dilweed wrote:I know its unscaled.

But Im building this for power AND looks, so I want it looking like a real fire arm.

well what kind of ammo do you plan on shooting if it's small you could just make a hammer valve and if its large you could just go with a burst disk for the main valve like inonickname suggested it wouldn't be that hard to make it look like a real firearm if you used a hammer valve it would be more difficult but still possible with a burst disk so i don't see the problem
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Unread postAuthor: dilweed » Mon Jun 22, 2009 7:33 am

Im planing on making it 30 - 40 cal, use 180 or more psi and want at least 50 ft/lbs from it. I also plan on shooting it up to 25 yards and want it to be capable of shooting into plywood.
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Unread postAuthor: spudtyrrant » Mon Jun 22, 2009 10:26 am

dilweed wrote:Im planing on making it 30 - 40 cal, use 180 or more psi and want at least 50 ft/lbs from it. I also plan on shooting it up to 25 yards and want it to be capable of shooting into plywood.
using 20mm chamber 25cm long and a 10mm barrel 120cm long and this valve http://www.spudfiles.com/forums/self-closing-piston-valve-brass-fittings-t17609.html at 180psi ggdt predicts 71ft pounds and 500fps with an 8g projectile more than enought to accomplish what you want
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Unread postAuthor: dilweed » Tue Jun 23, 2009 8:50 am

Thankyou very much.
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