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Gas operated Semi

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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Gas operated Semi

Unread postAuthor: Suppressive Fire » Wed May 30, 2007 3:44 pm

Just had couple quick question about the right way to do this. What is the most effective way to make a gas operated closed bolt gun? Has anyone ever made on before? What kind of reliability can I expect from this system? Is there a better way that is more effiecent or reliable to cycle a bolt? The bolt must travel about 5-6in.
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Unread postAuthor: iknowmy3tables » Wed May 30, 2007 3:50 pm

uh their is no offical or best way i think, this is fairly new soil so all we can do is brainstorm.

I believe one way is to use a piston powered by the fill of the chammber or for some reason you could use a pressure switch and a electric drive
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Unread postAuthor: VH_man » Wed May 30, 2007 4:11 pm

i say just use two valves. one that fires the gun, and another that makes the bolt go back. make sure that it takes longer for the valve that makes the bolt go back to actuate than the one that fires it.
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Unread postAuthor: Suppressive Fire » Wed May 30, 2007 6:57 pm

The plan that I have is...

The gun will be gravity mag fed and will eject "spent casings" down. On either side there will be a piston that draw air from the barrel once the projectile clears the gas draw ports which are about 3in down the 36in barrel. I plan on drilling holes and using a 1/8in pipe tap to attach fittings so if it doesn't work then I can plug the holes with 1/8 threaded plugs. The other idea that I had was to have a contact switch in one of the draw ports so when the port receives pressure it depresses a switch which will in turn actuate a solenoid and the rams will cycle the bolt which will reseat via a spring.
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Unread postAuthor: VH_man » Wed May 30, 2007 7:12 pm

it might work, just dont count on it. if it works, im stealing it for my airsoft rifle........
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Unread postAuthor: Suppressive Fire » Wed May 30, 2007 7:23 pm

I'll let you guys know how it turns out. Too bad gas operation is already patented. Just remember who thought it up in the spudding world first! Thanks guys
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Unread postAuthor: iknowmy3tables » Thu May 31, 2007 3:17 pm

it probaly wont work, gas operation has been thought of and attempted many times but I've never seen a successful gun. you see the whole thing about gas operation is just not very applicable for most spud gun designs.

for starters gas operated guns are designed to delay bolts and have locking bolts instead of normal blowback where energy is loss and the stronger rounds have high chance of hot gases escaping. so gas operation was made to stop the bolt from opening early

second gas operation is used on guns that already have a existing blowback force which a believe a small amount of that is used in assisting the bolt's return. an inline connection to the barrel which is in almost all existing spud guns will not have a blowback force if anything it has a blow forward force including bolt actions.

finally the amount of excess gas in a spud gun is nothing compared to a real gun where force and velocity is always improved with a longer barrels and a perfect sized barrel length is so long that its very very impractical, unlike our guns that can obtain a somewhat perfect C:B ratio. this huge excess of gas on real guns make them loud, and practical for gas operation

the way you must power this long bolt is buy taping gas from the chamber filling chamber. the energy from the pressurizing chamber is easier, more practical to deal with, and more reliable for spud guns.
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Unread postAuthor: fastcannonman » Thu May 31, 2007 3:37 pm

i would just say two valves probley, and it might work. try it and if it doesn't work then tell me :)
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Unread postAuthor: iknowmy3tables » Thu May 31, 2007 3:58 pm

what no, Suppressive do you really want to have two valve arn't you trying for a semi that would need some expensive pneumatic logic valve to do both on a stroke and I don't see how the crap that works out ethier
I said use a piston that is powered by the pressurization of the chamber. when chamber fills up pneumatic piston pushes bolt simple, reliable, easy, and acts automatically when the chamber fills
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Unread postAuthor: goathunter » Thu May 31, 2007 4:01 pm

The easiest way would be to have a air piston that extends when pressurized than have it contract when no pressure is seen(or the other way around).Like 3tables said,have it connected to your chamber and it will open and close as you tank is filled.
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Unread postAuthor: jackssmirkingrevenge » Thu May 31, 2007 4:37 pm

at pneumatic pressures, forget gas operation and think direct blowback
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Unread postAuthor: iknowmy3tables » Thu May 31, 2007 4:48 pm

i don't think that will work this time jack, I belive with what he is planning the bolt is too long. he needs a very strong long bolt system.

edit: wait thats it :!: the perfection for for blowback design. imagine what if there were no spring in your blowback system and it was returned pneumatically. the piston pushing the bolt would be dumped with the air release. then you don't worry about the blowback overcoming the spring's growth in force as the bolt moves back and you could focus more on a dely that dosn't have an expontial growth of force be a decay like a good delay should have, an easy one is roller dely
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Unread postAuthor: VH_man » Thu May 31, 2007 6:15 pm

i gotta say, just make a blow-foward bolt. its simple, easy, and it works.......... sure its not as accurate, but youre not building a sniper rifle! its a potato cannon.........
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Unread postAuthor: Suppressive Fire » Thu May 31, 2007 6:43 pm

Actually I am designing a closed bolt system. I had a massive brainstorm while eating lunch today but I still have to work the details out. Any suggestions are great.
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Unread postAuthor: VH_man » Thu May 31, 2007 6:51 pm

well, in that case........

the only idea i have for you is to channel some pressure off the barrel and make a piston move back when air is dumped into the barrel. should work. im pretty sure thats how GBB's work (dont own one, dont know).

if it works, post it! i really want to see it.
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