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GB Co-ax

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: cwazy1 » Sat Oct 27, 2007 10:20 pm

So what do you guys think about my new planned cannon??

24" of 4" abs as the chamber.

on the barrel side

4" coupling
4"-3" bushing
3"-1.5" bushing
26" of 1.5" sdr21 pushed all the way into the 1.5" modded bushing

on the other side

4" female adapter
4" male adapt
4"-3" bushing
3"-1.5" bushing
1.5"-1" bushing
1"-1/2" threaded bushing
1/2"-1/4" threaded bushing
small 1/4" nipple
1/4" tee

on one side of the tee

1/2" ball valve

on the other side

1/4" nipple
1/4" tee

on one side of the tee

scherader valve

on the other side

1-100psi gauge
----------------------------------------------------------

i know that abs is not pressure rated, which is fine because im only going to take this cannon up to 60psi and no more. not going pvc end of story..hahah

----------------------------------------------------------

the piston that im going to use is a 3" end cap with 2 layers of pond liner as the sealing face and i'll stick some type of thick rubber as the bumper.

----------------------------------------------------------

when i ggdt this, it comes up with around 350 fps and when i range calc this, i get a max of 170m, does this sound reasonable??

----------------------------------------------------------

so im using the 1/2" ball valve as the pilot valve that is going to pilot around 20inches cube, should i go with a 3/4" or 1" ball valve instead?? im not doing a sprinkler valve, too $$ and is too large for my simple design.

------------------------------------------------------------

what do you guys think?? i want this to look like one large tube, very retro and simple. comments and etc welcome!
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Unread postAuthor: hi » Sat Oct 27, 2007 10:30 pm

what do you guys think


i think your going to die...

seriously though, i can understand not having access to large pvc pipe, as i am not able to get anything about 2'', but even i wouldnt make a pneumatic out of ABS. it would probably be safe for 60 psi, but i still wouldnt try it.

make a combustion, it would be more powerful with the given chamber and barrel, and not to mention safer.
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Unread postAuthor: st.croixsurfer » Sat Oct 27, 2007 10:40 pm

dont be an arogant fool dont use abs its not pressure rated for a reason
:twisted:
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Unread postAuthor: Novacastrian » Sat Oct 27, 2007 10:48 pm

hi wrote:
what do you guys think


i think your going to die...

seriously though, i can understand not having access to large pvc pipe, as i am not able to get anything about 2'', but even i wouldnt make a pneumatic out of ABS. it would probably be safe for 60 psi, but i still wouldnt try it.

make a combustion, it would be more powerful with the given chamber and barrel, and not to mention safer.


Don't combustions pressure spike over 65psi, if so i would reccomend a pneumo if one at all.
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Unread postAuthor: Marco321 » Sat Oct 27, 2007 10:50 pm

Novacastrian wrote:
hi wrote:
what do you guys think


i think your going to die...

seriously though, i can understand not having access to large pvc pipe, as i am not able to get anything about 2'', but even i wouldnt make a pneumatic out of ABS. it would probably be safe for 60 psi, but i still wouldnt try it.

make a combustion, it would be more powerful with the given chamber and barrel, and not to mention safer.


Don't combustions pressure spike over 65psi, if so i would reccomend a pneumo if one at all.


That is correct, but a combustion is very quick burst of pressure, but a pneumatic is constant pressure for an extended period of time, even 30 seconds is a very long time compared to a combustion reaction.


EDIT: IF you don't want to use PVC, why not use iron pipe? its cheap and strong.
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Unread postAuthor: cwazy1 » Sat Oct 27, 2007 10:58 pm

hi: yeah i have acess to 4" pipe, but i have to buy a 20 foot stick at 38 dollars. i already have a propane combustion, i havent posted it yet.

croix: hahahahha

marco: well i want it to be thick and short (chose like) and iron pipe is heavy as sh!t...but the only reason behind me not using pvc is that i cant get shorter lengths of it and seriously, 20 feet is too long..lol
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Unread postAuthor: MrCrowley » Sat Oct 27, 2007 11:18 pm

I would not recommend using ABS in a pneumatic, full stop. Not only is this a pneumatic, you are using it at 60psi and with 4" piston valve.

Don't do it man, just find some PVC from a plumbing merchant, they should sell off-cuts to you.
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Unread postAuthor: cwazy1 » Sat Oct 27, 2007 11:24 pm

ahh fine fine, i wont use abs then..

whta are cut offs??
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Unread postAuthor: Novacastrian » Sat Oct 27, 2007 11:30 pm

cwazy1 wrote:ahh fine fine, i wont use abs then..

whta are cut offs??


The piece of pipe left over after they have cut a full length up :wink:
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Unread postAuthor: cwazy1 » Sat Oct 27, 2007 11:36 pm

oh, gottcha.

anyone wanna ship me a 2' section of 4" pvc?? hahahha
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Unread postAuthor: MrCrowley » Sun Oct 28, 2007 12:00 am

Just go to a plumbing merchant, if lucky you will get it trade price (save some bucks) and then ask for any 4" off cuts, they should sell you the off-cuts by the foot.
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Unread postAuthor: unisonmind » Sun Oct 28, 2007 12:00 am

are you in the U.S.?
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Unread postAuthor: spudgunnerwryyyyy » Sun Oct 28, 2007 12:06 am

Yeah go with Mr. Crowley's idea because plumbing wholesalers are abundant in the us and if you happen to have a contractor friend all the better. Although they might not have your length you will almost always be able to buy four inch pipe.
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Unread postAuthor: cwazy1 » Sun Oct 28, 2007 12:53 am

ohh yeah i can easily get 4" pipe, its just that not many places have cut offs or small sections, but i'll take a look,

but im hoping BC has some cut offs and i can get soem from him.

other than the pipe, what do you guys think about my design??
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Unread postAuthor: LikimysCrotchus5 » Sun Oct 28, 2007 10:04 am

Well we all know that abs is bad for pressure rated but i have to tell you i know a guy who made one from abs. This was a guy who helped me get started with this hobby and he recommended that i use abs as a chamber. When i went to the hardware store they told me abs is not pressure rated and then i went with pvc. I am trying to look for the video on youtube where the comment is. Ill get it soon.

Well i couldnt find the comment but i found a how to video i remeber he made.

http://www.youtube.com/watch?v=7wUimvZctks

If you watch it he says that he used a 3 inch ABS pipe for the chamber
:roll:
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