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Double Shot (High Pressure Mini)

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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Unread postAuthor: Novacastrian » Sun Nov 04, 2007 8:32 pm

Well guys the Double shot has been modded.
I have increased the chamber size to approx 4ci (increase of 1.5ci), Re-positioned the scrhader to the chamber wall (it sits in the middle of the piston travel). It is now piloted by a blowgun since the scrhader didn't have the necessary flow for fast activation.
Also has a pressure gauge :)
It quite happily punches nails through 6mm Polycarbonate at 100psi. I still gotta buy a shock pump for higher pressures though.

First shot after the mods- ammo hits bin, bounces under door (3/4" gap), off wall, into the waiting back of my Father :roll:
Lucky he is a tough old bugger :lol:
I can't wait to crank this baby up to say 350psi :twisted:
Image
Image
First pic also shows the old chamber.
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Unread postAuthor: jackssmirkingrevenge » Mon Nov 05, 2007 2:11 am

Doesn't look half as clean as it used but I'm guessing it's more comfortable to fire now ;) get yuorself that shock pump, you'll know the difference :D
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Unread postAuthor: wannabie » Mon Nov 05, 2007 2:20 am

careful don't let me drool on it :P i think it looks even better then it did before :D
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Unread postAuthor: Solar » Mon Nov 05, 2007 3:20 am

Nice. You should be careful with the schraeder valves at anything higher than they are rated for. A threaded quick release paintball style input would be better if you have the meat to cut threads into. Your triggering mechanism is probably only 150psi as well. Clippard makes a 300psi stem valve that would be better.

Here is a pic of my latest machined piston valve. Rated for 1200 psi with buna-N o rings and positive force triggering.


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Unread postAuthor: Hubb » Mon Nov 05, 2007 3:27 am

Solar, are you trying to show that off? This is the second thread I've seen it in. Well, I'll compliment it. I wish I had the resources to do so. :wink:
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Unread postAuthor: Solar » Mon Nov 05, 2007 3:32 am

haha, sorry, but yeah... I didn't expect to see such an interest in higher pressure valves on here and I just finished assembling the first of fifty that I have machined for use with my launcher. Besides, the sheer volume of posts here make themselves obscure within moments it seems.
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Unread postAuthor: jackssmirkingrevenge » Mon Nov 05, 2007 3:46 am

Nice. You should be careful with the schraeder valves at anything higher than they are rated for.


I regularly use schrader valves taken from car or bicycle inner tubes at 400 psi or so - 10 times their normal working pressure - never had one fail on me so far.

Oh and Novacastrian, watch out for the old man :D
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Unread postAuthor: Solar » Mon Nov 05, 2007 4:17 am

wow, that surprises me. haha, I still wouldn't want to be anywhere near one that actually blew. That valve needle would hurt.
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Unread postAuthor: jackssmirkingrevenge » Mon Nov 05, 2007 4:30 am

Solar wrote:That valve needle would hurt.


Since it wouldn't be blown out of a barrel, I doubt it would come out with significant force - in any case, given the way it's constructed, the pressure required to blow it would have to be ridiculously high assuming the structural integrity of the stem isn't compromised.
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Unread postAuthor: Solar » Mon Nov 05, 2007 5:01 am

Shouldn't be too hard to find what ridiculously high would be using a 3000psi source. :-) I guess a threaded in shraeder would be fairly brutish, but if it taken from an old tire, wouldn't the inner tube rubber be the weak link?
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Unread postAuthor: jackssmirkingrevenge » Mon Nov 05, 2007 5:05 am

What I do is strip off the rubber from the stem like this, cut a few ridges in the brass with a file then epoxy it in place.
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Unread postAuthor: Novacastrian » Mon Nov 05, 2007 5:47 am

I strip the rubber then thread the stem (m6)
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Unread postAuthor: Novacastrian » Mon Nov 05, 2007 6:03 am

Solar wrote:Nice. You should be careful with the schraeder valves at anything higher than they are rated for. A threaded quick release paintball style input would be better if you have the meat to cut threads into. Your triggering mechanism is probably only 150psi as well. Clippard makes a 300psi stem valve that would be better.

Here is a pic of my latest machined piston valve. Rated for 1200 psi with buna-N o rings and positive force triggering.


Image


rory@eclipselauncher.com


Hey nice piston, can i ask what "positive force triggering" entails?
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Unread postAuthor: jackssmirkingrevenge » Mon Nov 05, 2007 6:05 am

Novacastrian wrote:can i ask what "positive force triggering" entails?


I'm guessing a hammer that's either spring-loaded or solenoid powered?
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Unread postAuthor: Solar » Mon Nov 05, 2007 5:41 pm

Positive force is:

The firing pistons use their difference in surface area with the ballast pressure to shift the piston rod and open the main valve.

This way the launcher won't misfire if there is an accidental discharge from the valve assembly or air ballast as can happen with exhaust valves.
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