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semi auto idea help

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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semi auto idea help

Unread postAuthor: Major Collins » Sun Jan 10, 2010 10:10 am

ok for my semi auto piston valved design i came up with this...

Image

(ok a few things ... first i think i need the regulator and ball valve to swap positions , second its not to scale (obviously) and third i got lazy towards the end ... you can tell haha )

soo would this work and so how can i improve it ?

and i think only the pro-er people will understand this design lol
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 10, 2010 10:16 am

You can make it a lot simpler along the lines discussed here.

No need for a secondary chamber, regulator or ball valve, all you need is for a spring to reset the piston. Pressing the blowgun momentarily will fire the piston but once the pilot is reclosed the piston will reseal, allowing you further shots.
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Unread postAuthor: JDP12 » Sun Jan 10, 2010 10:37 am

Yea... You have a lot of exces parts there. Do what jsr said
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Unread postAuthor: Major Collins » Sun Jan 10, 2010 11:00 am

but will there be enough flow or suction or whatever to work against the piston to pull it back open with a spring pushing back on it?( it obviously does lol but can i get a picture or a little more detail of this?)
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Unread postAuthor: JDP12 » Sun Jan 10, 2010 11:06 am

Yes. The chamber air will open the valve unless you have an insanely strong sprin in there. But your design is still much too complex.

Look at mine in JSRs thread, or his. Verysimple concepts. Albeit he coulnt get his to work and I need some more money before I can test mine, they are still good examples
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 10, 2010 11:21 am

JDP12 wrote:Look at mine in JSR's thread, or his. Very simple concepts. Albeit he couldn't get his to work and I need some more money before I can test mine, they are still good examples


Granted, but it was only at high pressure, at 100 psi the valve was working perfectly well:

[youtube]http://youtube.com/watch?v=xKq4ktpplMA[/youtube]

Major Collins wrote:can i get a picture or a little more detail of this?)


Only 'cause it's a lazy sunday afternoon, here you go:
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Unread postAuthor: MrCrowley » Sun Jan 10, 2010 4:26 pm

It would work but you would either need;

a) crazy high pressures
or
b) a crazy sized primary chamber

...for this to be even worth it. If you are shooting something like 6mm BB's, let's say, and your primary chamber is 2" x 12" long piece of metal pipe. If you have that charged to 800PSI, and your secondary chamber is, let's say, a 1" x 6" chamber, with pressure regulated down to 350PSI or so, then this cannon might be worth the hassle but I don't see it working well on large bores without the cannon being pretty big.

A lot of new members like this idea, and a lot of them post this idea in many different forms thinking that having a second or third shot is really the most important thing. You'll find with spudding (on large bore cannons) that you don't want a second or third shot that is slightly less powerful, you either want about 5-10 decent powered shots, or just one very powerful one.

It's just not a very practical idea. You think that because you have this extra shot or two the cannon is portable, unfortunately you've had to build the cannon so bloody big that it no longer is.

What diameter barrel do you plan on using? Maybe we can help you with ideas.
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Unread postAuthor: Major Collins » Sun Jan 10, 2010 10:57 pm

i was using it for air rifle pellets no more big bore lol im downsizing from marbles ummm i was thinking of using 400 psi in the primary chamber an it being regulated to 100 or 120 .For the ideas ^^^^ up there how strong do i need my spring looks like fairly weak so the piston can be replaced? am i right?
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Unread postAuthor: MrCrowley » Sun Jan 10, 2010 11:15 pm

If you still want to go with your original idea, get a paintball CO2 tank and make that the primary chamber and regulate that to a smaller secondary chamber.

Instead of regulating down to a 100PSI charged secondary chamber, it might be better to just make some sort of semi-auto hammer valve* directly fed by the 800PSI charged paintball CO2 tank. A small volume burst of high pressure CO2 might be better than a high volume burst of low pressure CO2 or air.

*Check anything that JSR has built over the last few years, definitely some interesting designs you should check out if you choose to take this design path.
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Last edited by MrCrowley on Sun Jan 10, 2010 11:18 pm, edited 1 time in total.
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 10, 2010 11:16 pm

Major Collins wrote:i was using it for air rifle pellets no more big bore lol im downsizing from marbles ummm i was thinking of using 400 psi in the primary chamber an it being regulated to 100 or 120 .For the ideas ^^^^ up there how strong do i need my spring looks like fairly weak so the piston can be replaced? am i right?


You might want to consider using a blowgun directly as a valve, at 400 psi you'll get decent power with a long barrel and with some ingenuity you could make a spring loaded mechanism which opens the blowgun turning it into a hammer valve, definitely no need for primary and secondary chambers then.
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