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Pneumatic AT4

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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Pneumatic AT4

Unread postAuthor: Cpt Obvious » Tue Feb 14, 2012 2:10 am

So I had just finished finalizing the plans of a combustion type RPG for use in airsoft or paintball (with the metered shell idea given to me so well by JSR) and realized I would never be allowed to use it other than in my backyard. Any sponsored or even semi-official event would want nothing to do with it because they say that the BATF would classify it as a firearm and a liability.

So I've temporarily shelved the combustion type for later and moved on to compression. I've known and seen several examples of compression type launchers built and operated inside the spent canister of an AT4. Being a real canister is a few hundred dollars, I'm going to build a pneumatic cannon completely in line which will be put into a piece of 4" ABS with all the triggers and gauges and safetys and dressed up to look just like one.

I decided on the simple 12v solenoid valve instead of the modified sprinkler valve because I'm pretty sure the large sprinkler valve would not fit inside the body. Plus I think the electrical solenoid would be less likely to fire accidentally because a simple switch could disconnect the trigger.

I'm also fairly certain I would not be able to use a Palmers stabilizer because the line in is on the side of the stabilizer. So I'm going to use some other kind of low pressure adjustable paintball regulator.
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Unread postAuthor: Crna Legija » Tue Feb 14, 2012 2:20 am

what size is your '' simple 12v solenoid valve'' also sprinkler valves are electronically triggers as standard.
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Unread postAuthor: Cpt Obvious » Tue Feb 14, 2012 9:14 am

I have a 1" solenoid now, i'm looking for a 1.5", and if i used the sprinkler valve i would modify it to use a blowgun so no it would be a mechanical trigger as opposed to an electrical one.
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Unread postAuthor: jackssmirkingrevenge » Tue Feb 14, 2012 11:08 am

You can still use pneumatic cartridges ;) though these would be rather more complex to make than a simple combustion.

Some ideas from another thread, to built the cartridge:

Image

... or make it valveless - the cartridge is just an tube with a connector at one end to your air source, and a detent to keep the projectile in place until enough pressure develops to pop it like a champagne cork ;)

Image

There are only some times of projectiles the above would work well with though, so it depends what you want to use it for.
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Unread postAuthor: Cpt Obvious » Tue Feb 14, 2012 11:26 am

I like the idea of the cartridge, but I will try to see if i can build one first before I commit to the design. How would I pull the piston back to release the air stored behind it?

I considered the valveless design because of its simplicity. But it seems like it would waste quite a bit of air, and I want to be able to adjust the FPS of my projectile to meet different field specifications for these types. And I think in order to do that I would have to have different sizes of detents and make them exchangeable, which seems to defeat the purpose of the simplicity of a valveless.

Also if i decided to use a modified sprinkler valve (which I would prefer because of their speed) would it fit inside a 4" pipe? or would I need to cut a large hole to let it sit out of the side as opposed to a small one for the blowgun?
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Unread postAuthor: jackssmirkingrevenge » Tue Feb 14, 2012 2:23 pm

Cpt Obvious wrote:I like the idea of the cartridge, but I will try to see if i can build one first before I commit to the design. How would I pull the piston back to release the air stored behind it?


Schrader. It's the fill valve and pilot valve ;)

I considered the valveless design because of its simplicity. But it seems like it would waste quite a bit of air


Not really - because it's the "ultimate" valve (zero opening time, instant full flow) you need a lot less air to get the same performance you would from any other type of valve.

and I want to be able to adjust the FPS of my projectile to meet different field specifications for these types. And I think in order to do that I would have to have different sizes of detents and make them exchangeable, which seems to defeat the purpose of the simplicity of a valveless.


With a bit of ingenuity you can make an adjustable detent :)

Also if i decided to use a modified sprinkler valve (which I would prefer because of their speed) would it fit inside a 4" pipe? or would I need to cut a large hole to let it sit out of the side as opposed to a small one for the blowgun?


http://www.amazon.com/Rain-Bird-Sprinkl ... B00002N8NN

Product Dimensions: 3 x 5 x 5 inches
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Unread postAuthor: Cpt Obvious » Tue Feb 14, 2012 3:44 pm

*facepalm* didn't read the design of the cartridge close enough apparently.
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Unread postAuthor: biged » Wed Feb 15, 2012 6:30 pm

Couple pictures of 2" and 3" toolie pistons.
Image
Pressure tested to 800 psi.

Really long 2.5" piston for an M9 bazooka I never finished.
Image

///ed///
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Unread postAuthor: Cpt Obvious » Thu Feb 16, 2012 8:45 pm

Another question, My regulator from the Co2 tank into the compression chamber needs to be inline if possible, which is why I'm trying not to use a Palmers stabilizer. My goal psi is between 75 and 100 if possible, but I can't seem to find any regulator that would work for that.

Is there any reg out there that anyone knows of? Or will I have to just use a palmers and have a remote air line?
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Unread postAuthor: jackssmirkingrevenge » Fri Feb 17, 2012 1:31 am

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Unread postAuthor: Petitlu » Fri Feb 17, 2012 2:23 am

http://www.ebay.com/itm/CO2-Adjuster-Re ... 4247wt_952

regulator placed on my PAC two caliber

Image
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Unread postAuthor: Cpt Obvious » Fri Feb 17, 2012 10:48 am

perfect, just what I was looking for
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Unread postAuthor: Cpt Obvious » Fri Feb 17, 2012 10:52 am

yours would be preferable JSM but it won't fit US tanks, i'll find one that does though

edit: aw crap double post
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Unread postAuthor: Lazyboy » Fri Feb 17, 2012 10:06 pm

I asked the supplier (of the regulator JSR linked to) what is the maximum inlet pressure and got this reply.

normally the co2 cylinder contain wiht 50-70kg/cm2 liquid state co2
the regulator can take up to 1500 psi MAX which is 105.5 kg/cm2
it is more that enough for all the cylinder in the world
thanks
- aqualabsexpress

Could be good for a lot of projects and cheap

Petitlu is that a regulator or a flow control valve
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Unread postAuthor: killerbanjo » Fri Feb 17, 2012 11:12 pm

Check out these, they look like you can screw a paintball tank right into them
8)

With a guage but ugly
[url]http://www.ebay.co.uk/itm/CO2-Simple-Regulator-Diffuser-Adjuster-VALVE-tube-crs-/270720473558?pt=UK_Pet_Supplies_Fish&hash=item3f083299d6#ht_4974wt_1152
[/url]
Without one and good looking

[url]http://www.ebay.co.uk/itm/UP-Plant-Aquarium-Simple-Co2-Regulator-A128-/160441955554?pt=UK_Pet_Supplies_Fish&hash=item255b15f4e2#ht_3446wt_1008
[/url]

Or an even nice one made for paintball, low pressure though

http://www.ebay.co.uk/itm/170691170358?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649#ht_3321wt_968
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