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A Little Help for a Newb

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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A Little Help for a Newb

Unread postAuthor: surfbum » Fri Apr 13, 2007 8:21 pm

hey all, im pretty new here and i had a few questions that i hope you guys can help me with.

im throwing around the idea of creating a bazooka style cannon for scenario paintball use. I want the set up to be as small as possible, but still with a decent effective range.

the cannon will be run off regulated CO2, my main question is about valves.

before coming to this sight i thought the sprinkler valve or the manual ball valve was the only routes in terms of getting air from the compression chamber to the barrel, but ive seen a couple other systems including QEVs and piston valves here.

my main question is what type of valve system would work best for my application? and out of curiousity can someone explain how the QEV systems work? and lastly approximately what volume of gas would you need to get a standard projectile (potato, sabot of paintballs, nerf dart, etc.) to go about 100 yards assuming a regulated air pressure of about 125-140 psi?

thanks for the help all
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Unread postAuthor: spudthug » Fri Apr 13, 2007 8:24 pm

ur shooting this at people??? anyway a sprinkler valve would be best for a bazooka because QEVs and pistons are all 3 way valves...u want inline for a bazooka and ball valves are horrible but make sure u mod ur sprinkler....
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Unread postAuthor: keep_it_real » Fri Apr 13, 2007 8:24 pm

QEV's need only a small pressure difference to pilot. They have pretty good flow. A piston valve has very good flow. I would recommend it. I would make the chamber 40 cubic inches but thats a guess.

edit- spudthug- a barrel sealing coaxial is inline and I think it would look cooler than a sprinkler valve. Actually no, it would look much cooler. Anyway just a thought.
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Unread postAuthor: spudthug » Fri Apr 13, 2007 8:27 pm

keep it real he wants to build a bazooka that means inline so he cant use anything but sprinkler or ball valve


edit: yes but i think this is his first pneuamtic...i dont think he should be using pistons just yet
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Unread postAuthor: surfbum » Fri Apr 13, 2007 8:37 pm

dont underestimate my mechanical ability :D

difficulty of construction is not a factor, im a mechanical engineer with full access to a machine shop

you mentioned "barrel sealing coaxial" are you referring to this?: http://www.spudfiles.com/forums/3-piston-t313.html
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Unread postAuthor: spudthug » Fri Apr 13, 2007 8:47 pm

yes that is barrel sealing coaxial....although it would be cheaper and simpler to use a sprinkler valve then make a coaxial for a different design...if u want to u can do this but it may take alot of time....that is a kind of an over kill piston for a coaxial usually to be simple everyone uses endcaps and those work fine...

edit: tell me the demensions of your chamber and barrel and ill see if i cant find a piston u can use on this sight...if ur using 4 inch for the chamber, 3 inch endcaps work almost too perfect for coaxial pistons....
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Unread postAuthor: iPaintball » Fri Apr 13, 2007 8:57 pm

If you're planning on making a bazooka style launcher, try making a coaxial. For the chamber just use a 4' lentgh of 4" pvc, for the piston, use a 3" endcap, and for he sealing face, just attatch a rubber coupling onto the end of the barrel. You should also use a modified sprinkler valve to pilot the piston. If you want to add bazooka-style barrel flare, just attatch a 4" closet flange to the rear end,
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Unread postAuthor: surfbum » Fri Apr 13, 2007 8:59 pm

i just threw this diagram together using a QEV valve

would it work?
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Unread postAuthor: Scope » Fri Apr 13, 2007 9:02 pm

Look at judgement_arms L.A.W.

its basically the perfect paintball cannon...

im making a cannon much like that actualy
use 2 inch sch40 for a barrel because u want to use nerf rockets

if you use a 4 inch pvc as the outside peice i would recommend making it about 40 inches give or take... thats how long an AT4 is so it is a good length ergonomicaly.. it will also give you more then enough performance so you can regulate your gun down to legal usage!!
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Unread postAuthor: iPaintball » Fri Apr 13, 2007 9:02 pm

Actually, I like your setup better. you might want to make the chamber a little bigger though...
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Unread postAuthor: A-98 » Fri Apr 13, 2007 9:03 pm

negatory.

the barrel needs to be at a right angle to the chamber.

upload pics in a sec, to lazy to explain now

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Image
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Unread postAuthor: keep_it_real » Fri Apr 13, 2007 9:12 pm

You can't put the pilot valve and the co2 together like that. It might sorta work but the co2 will just go out the blow gun. Instead I would use a slide valve.
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Unread postAuthor: surfbum » Fri Apr 13, 2007 9:14 pm

ok, so same general design, but revised piping near the QEV (not drawn to scale)

this would be the correct layout and would function correctly?

what QEV would people suggest? with what size output/input?

thanks for all the help by the way
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Unread postAuthor: surfbum » Fri Apr 13, 2007 9:16 pm

keep_it_real wrote:You can't put the pilot valve and the co2 together like that. It might sorta work but the co2 will just go out the blow gun. Instead I would use a slide valve.


could i just put a ball valve inbetween the CO2 and the pilot valve that would get shutoff when the chamber filled? whats a slide valve?
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Unread postAuthor: keep_it_real » Fri Apr 13, 2007 10:44 pm

a slide valve will do exactly what you want. It pilots the valve when its back and lets air through to load the chamber when its forward.
go to http://www.mcmaster.com/ and look up sleeve valves (same as slide valve)
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