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4" Piston Cannon pls

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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4" Piston Cannon pls

Unread postAuthor: cwazy1 » Wed Nov 21, 2007 11:39 pm

This is my first coaxial piston cannon.

4" chamber that is 1.5' in length.
1.5" sdr21 GB barrel cut flush (16")
The piston is a 3" end cap with some pond liner on the sealing face.
Using some cut up socks as a bumper.
I am pioleting with a 1/2" ball valve
Filling with co2 from a quick connect.
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Unread postAuthor: fatcat » Wed Nov 21, 2007 11:40 pm

Im confused. What is that a pic of?
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Unread postAuthor: cwazy1 » Wed Nov 21, 2007 11:41 pm

^^^ thats just sad.
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Unread postAuthor: hi » Wed Nov 21, 2007 11:42 pm

its a coaxial. looks good to me. i would have made it bigger, but thats ok, it still looks good.
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Unread postAuthor: Hubb » Wed Nov 21, 2007 11:43 pm

That looks like a pic of the cannon and the fill station.
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Unread postAuthor: cwazy1 » Wed Nov 21, 2007 11:45 pm

yup exactly. i also would have made it bigger but when i built it, i was planning on pumping it up with a hand pump and too large of a chamber meant too much pumping.
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Unread postAuthor: MrCrowley » Wed Nov 21, 2007 11:45 pm

fatcat wrote:Im confused. What is that a pic of?


A coaxial pneumatic cannon.
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Unread postAuthor: benstern » Thu Nov 22, 2007 12:05 am

May I ask why in the hell you thought it would be ok to use ABS as a chamber in a pneumatic gun and then power it with CO2?
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Unread postAuthor: MrCrowley » Thu Nov 22, 2007 12:08 am

You sure it's ABS? Since the fill and pilot setup is painted black, so could the PVC pipe if that's what it is.

Is that a clean out cap or a plug?

It's all pressure rated right?
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Unread postAuthor: Hubb » Thu Nov 22, 2007 12:08 am

benstern wrote:May I ask why in the hell you thought it would be ok to use ABS as a chamber in a pneumatic gun and then power it with CO2?


Because he's cwazy(1)! :lol:

Edit: To answer MrCrowley, that is a cleanout.
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Unread postAuthor: MrCrowley » Thu Nov 22, 2007 12:17 am

Aren't cleanouts non-pressure rated?

Forgive me but i'm not familiar with all American fittings being in NZ and all. :P
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Unread postAuthor: Hubb » Thu Nov 22, 2007 12:20 am

Cleanouts are not pressure rated, or, at least, I've never seen a pressure rated one.

BTW: What I'm calling a cleanout is the combination of the adapter and the plug. That's how we called it when I worked at a hardware store.
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Unread postAuthor: cwazy1 » Thu Nov 22, 2007 12:56 am

ahh, about time soemone brings up the topic about abs/pvc.

yes it is abs.

i know

i am aware

im only going to 60psi

so its okay.
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Unread postAuthor: Hubb » Thu Nov 22, 2007 12:58 am

cwazy1 wrote:...so its okay.


Is it?
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Unread postAuthor: cwazy1 » Thu Nov 22, 2007 12:59 am

hubb017 wrote:
cwazy1 wrote:...so its okay.


Is it?


yeah, im pretty sure it is. if you search some stuff on this forum about ppl trying and seeing what psi abs will explode at, you will notice that its over 100psi. plus, even if it does decide to blow, it'll "rip" instead of fragmenting into small pieces. using these observations, i can say that it is safe to use at my set psi, 60.

i just dont see why ppl still dont use abs even for low pressure apps in the spudding community. i know it isnt rated for pressure but its not like ppl havent done tests/experiments to find the burst pressure of the stuff? plus, if you average these results from ppl's tests, you get an "average" answer to the limit of abs' bursting pressure. (assuming that all abs pipe is made usign the same form and etc. etc. ) so what im saying here is that we have somewhat labeled abs as a no no for pneumatics, while true for high pressure it can go badly but cant pvc also fail? why must we say that if there is no pre-determined pressure rating that the pipe is unusable for any pressure at all?? arent we humans? cant we find out the pressure limit ourselves and "evolve"..no one said that we can use pvc/abs/etc etc pipe as a form of a propulsion device?

so back to my case, in addition to the the above, combustion cannons produce at least 60psi and can even get to 80psi sometimes during the ignition of the propellant. i know that its a fraction of a sec and yes its true, so why cant it hold pressure for a couple of seconds?
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Last edited by cwazy1 on Thu Nov 22, 2007 1:13 am, edited 2 times in total.

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