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My Semi questions...

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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My Semi questions...

Unread postAuthor: Lockednloaded » Sat May 22, 2010 7:05 pm

I'm building a semi automatic pretty soon, not all the parts are in yet. I have ordered the QEV, the 3-way valve, and the air cylinder. I just need to go to homedepot and buy the parts for the loading mech. I will use two semi trimmed tees with the stops bored out. A piece of pipe will slide all the way through. It will have a full bore hole at the loading port and a bunch of smaller holes where the QEV attaches. To make sure the whole unit is sealed, the air ram will be housed inside an air tight compartment behind the loading mech. I have drawn up a crude design on sketch up, hope its alright.

Image

It will be using a 3/4" QEV so i plan to use 3/4" CPVC for paintballs. I was wondering if anyone had found any marbles that fit into this type of pipe?
If I use paintballs, would the air ram pop them?
what kind of stop could i make that would not pop paintballs, but will not let them fall out when the gun is tilted.
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Unread postAuthor: POLAND_SPUD » Sat May 22, 2010 11:23 pm

the ram doesn't have to be in an air tight compartment... just built a small piston with an oring that is screwed on the tip of the rod

of course that solves one thing, but also creates another problem - the piston has to be ideally centred or else it won't not move smoothly and/or can block

what kind of stop could i make that would not pop paintballs
foam maybe ??
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Unread postAuthor: michaelgohjs » Sun May 23, 2010 1:40 am

emm.. can you explain how the 3 way valve works?..
i dont understand y do you need to fix it to the barrel also
(i m very noob please be patient with me)
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Unread postAuthor: POLAND_SPUD » Sun May 23, 2010 6:44 am

you'll find all the info you need here > http://www.spudfiles.com/forums/directi ... 20438.html
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Unread postAuthor: Lockednloaded » Sun May 23, 2010 10:35 am

POLAND_SPUD wrote:
Lockednloaded wrote:what kind of stop could i make that would not pop paintballs

foam maybe ??


Sorry, I was unclear there, I'm talking about a hop-up or an o-ring detent that would not pop paintballs, but would not allow them to fall out of the barrel. It doesn't have to increase accuracy like a hop up would, it just has to allow me to aim downward.
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Unread postAuthor: Gun Freak » Sun May 23, 2010 10:38 am

You can use a dent detent, just make a little dimple in the inside of the barrel big enough to stop the paintball but small enough not to pop it. Hubb has more info in the Hubb Library.
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Unread postAuthor: Lockednloaded » Sun May 23, 2010 11:13 am

how would i make a dent in CPVC? i know you just tap copper pipe with a nail lightly to make one. maybe i could just put a few layers of electrical tape.
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Unread postAuthor: Gun Freak » Sun May 23, 2010 11:50 am

That would work too, isn't CPVC similar to PVC? Dents are easy to make in plastic pipes but they wear down.
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Unread postAuthor: Lockednloaded » Sun May 23, 2010 5:39 pm

dents in PVC? never seen it before. I may just cut an o-ring groove and make it go through the pipe at one point.
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Unread postAuthor: Gun Freak » Sun May 23, 2010 6:36 pm

That would work too, just try to make the o-ring go in as least as possible but still keeping the projectile from rolling out.
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Unread postAuthor: grock » Sun May 23, 2010 10:55 pm

you could try heating the pipe a little bit, then making the dent with something metal, the problem might be keeping the shape of the rest of the barrel.

also, depending on sizing, you might want to make some kind of bar that goes across the bottom of the barrel so that the paintballs dont go down in the direction of the qev
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Unread postAuthor: Lockednloaded » Mon May 24, 2010 11:40 am

ok, maybe i can worry about ammo falling out once i get all of the parts, 2-7 business days my @ss....
Has anyone ever found any paintball caliber re-usable, spherical ammo? I think there is such thing as solid rubber "paintballs" but i would also like a marble ammo for destruction and they are extremely expensive
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Unread postAuthor: POLAND_SPUD » Mon May 24, 2010 12:06 pm

First of all, don't assume that you can reuse ammo as in 90% of cases you won't find it
Secondly, the larger calibre you choose the more air and a larger gun you need... what is more, this has a direct effect on mag capacity
Finally, the larger the diam of ammo the higher the cost

So in conclusion - you want to keep the calibre as small as possible...

ball bearings are probably the best ammo you can find... I am guessing that lead balls would be even better but I haven't tested them

I spent a lot of time modelling different calibres and my conclusion is ->
for a handheld semiauto launcher the best calibre is around 9.65 - 12.7 mm

(note how mass changes as the diam. increases 8.731mm bbs weight 2.65g while 12.7mm 8.4g)
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Unread postAuthor: Lockednloaded » Mon May 24, 2010 1:05 pm

I think i could find bright yellow rubber balls fairly easily. As far as calibre vs. mag capacity is concerned, a paintball hopper could be added for more shots, so that is not much of an issue. as for calibre vs. power, A 3/4" QEV with about 7" of 1" galvanized pipe should give me a pretty solid velocity. These are just assumptions made from experience, but you have more of that and a design program.

By the way, does anyone know the actual ID of 3/4" CPVC?
and would 50 cal paintballs fit well in 1/2" PVC?
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Unread postAuthor: the unit » Tue May 25, 2010 4:13 pm

http://www.badlandspaintball.com/reball.html

these are an example of reusable paintballs, they are made from a kind of rubber, there are other cheaper imitation brands
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