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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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Unread postAuthor: Darkerweb12 » Thu May 31, 2007 6:52 pm

Dude, I've been brainstorming semi/full-auto designs since half-way through the school year in my *second* lunch... It's not an easy thing to think up, but I think I have a design, but unfortunatly, not cash monies to build it with... I think I'm gonna do a very small mock up with hotglue and straws to see if my theories will work...
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Unread postAuthor: VH_man » Thu May 31, 2007 6:56 pm

haha. post the glue/straw mockup. you might get the ghetto award.........
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Unread postAuthor: Suppressive Fire » Thu May 31, 2007 7:49 pm

I'm giong to try drawing gas from the barrel first. If that doesn't work then I'll hook the piston up so when Its extended and under pressure the bolt is closed. The piston will be attached to the pilot chamber (If I use a tee valve, the HEAR is more promising by the minute) so when its dumped a spring will return the bolt and close the piston.
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Unread postAuthor: iknowmy3tables » Thu May 31, 2007 8:31 pm

if you want to test the gas operation attach some piston to an existing spudgun's barrel, make it inline with the barrel, aim the gun down and se how much weight it can lift and how far, but piston from chammber has been done sucessfully and with that decent amout of force in the chammber it's bound to be reliable.

you should also look at jack's blowback concepts, and this http://boltsniper.com/BS-8/BS8.htm
just good stuff to consider, I am on a similar jorney to make a new automatic so good stuff.

also add a spring to asist the feed just because it will make it more reliable, I would know being the creator of deus ex machina

finally this is my 500th post :occasion9: :wav:
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Unread postAuthor: jackssmirkingrevenge » Fri Jun 01, 2007 3:55 am

Why do you need a closed bolt? Pistols using pressures hundreds of times greater than spudguns use direct blowback, hell the swiss even made a 20mm rifle that worked on the same principle. Closed bolt sounds too overkill in my opinion.
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Unread postAuthor: iknowmy3tables » Fri Jun 01, 2007 7:58 am

closed bolt conserves power, and even then they have to be delayed. i belive with the guns I have seen blowbacks/recoil with long bolt have often been unreliable and uneffective
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Unread postAuthor: From_Hamsterdam » Fri Jun 01, 2007 11:44 am

the deus ex machina could be made semi auto by turning the bolt in to a blow forward bolt that is pulled back with springs when pressure is not applied.

http://www.spudfiles.com/forums/deus-ex-machina-t7864.html
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Unread postAuthor: Suppressive Fire » Fri Jun 01, 2007 2:24 pm

That was my second thoery if you were reading my previous post only with the closed bolt.

Anyway I plan on biulding a 1/2 to 1/4 scale version to test all my theories. I'll definaltly post results if I get any
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Unread postAuthor: VH_man » Fri Jun 01, 2007 2:40 pm

i reccomend K&S precision brass tubing for all moving parts that dont have to be (completely) airtight but that still need to move. remember also that for each size, the next biggest and the next smallest size will fit perfectly in the first size, leaving a little bit of blow-by, but definetly enough to create gas-rams. i actually made a blow-foward bolt for a nerf gun with K&S brass tubing, and it still works fine, however the shell ejection system didnt actually work so well. if i ever get it to work i will post it.
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Unread postAuthor: iknowmy3tables » Fri Jun 01, 2007 3:48 pm

i don't know how well brass tubing will fit a larger caliber guns, sounds expensive.

the deus ex machina could be made semi auto by turning the bolt in to a blow forward bolt that is pulled back with springs when pressure is not applied.

I doubt it, normal blow-forward bolts are not air tight or else it would have trouble on the return motion, they are used on guns with short bolts and minimal resistance, the deus ex machina bolt is long, and has a lot of resistance especially on the return where you need a nice swift pull to get the shell to eject or else without momentum its pretty hard. when you add all that force on a blow-forward bolt the thing may hardly have any power left and probebly wont work period
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