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My second pneumatic (This one didnt blow up)

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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My second pneumatic (This one didnt blow up)

Unread postAuthor: GrafixBoy » Sat Sep 29, 2007 6:32 pm

This is my second try at a pneumatic. This one is all steel. I had a bucket of pipe fitting parts so it was like putting together a puzzle without knowing if all the pieces are there. I wish I could say there was a "plan" when I built it but there wasnt. This is what I had available. The barrel is 1"X24"

It shot a 6 inch nipple wrapped in tape about 50 or 60 yards at about 50psi. There are some leaks but i dont know where they are coming from because i cant hear them. When you put the air in, when its full will it stop or keep compressing it in there? I have a pressure gauge on it and when it gets to about 100 psi i stop. I dont know how much I can put in there. Ever since that death trap I made last time blew apart on me (it wasnt steel) Ive been kinda "gun shy".

I know a ball valve isnt the best thing to be using but its what I had. Please give me your thoughts.
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Unread postAuthor: iPaintball » Sat Sep 29, 2007 6:37 pm

Sweet cannon dude. I love it when you can make entire guns from spare parts! When using larger diameter pipe nipples like that, it works better to use pipe thread paste or silicone.
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Unread postAuthor: Novacastrian » Sat Sep 29, 2007 6:40 pm

Use soapy water to detect leaks, mix some detergent with water and put it in a spray bottle, pressurise the gun and spray the water onto the joints, bubbles will tell you were your leaks are.
As for the gun it looks sick nuts :P I'm thinking that it would be a tad on the heavy side though! At least it will last forever.
Good luck with finding those pesky leaks.
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Unread postAuthor: e1337 » Sat Sep 29, 2007 6:41 pm

Im not sure how you can have leaks on threads when you have teflon tape in them. Try submerging in water (aka pool) and retape the treads that have bubbles coming out. As for advice, I would make a barrel-sealing piston and take it up to 150psi.

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Unread postAuthor: DYI » Sat Sep 29, 2007 6:43 pm

That looks fairly interesting, but if you insist on using a slow valve, you should use a longer barrel (preferably smoothbore, not steel). What is the chamber volume on it? If you have the means, you should take it up to about 300-500 psi if you want fairly decent performance with a short barrel. What is the point of that union on the end of the chamber? Is it used as a safety valve?

PVC guns can be safe, but in my opinion, they require a higher level of skill, and are always slightly more prone to disasters. Turbohacker's dad lost an eye to a relatively well made PVC pneumatic yesterday, when the regulator failed, or something.
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Unread postAuthor: LikimysCrotchus5 » Sat Sep 29, 2007 6:47 pm

well first things first, if you have leaks try to fill it and then shut it of you compressor and listen closely. Then make sure you used teflon tape on each of your threads, and dont be shy on your threads, tape them good. then rescrew them once you apply tefon tape to them. There is also some kind of glue or something you can put on threads so they dont leak. I saw this at Ace hardware and my dad told me that it does the same thing as teflon tape. But just use teflon tape to be sure. And you can pump it enought to 300 psi +. So dont be shy. Once there are no more leaks, fill it up. You can get alot of power out of that. :wink:
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Unread postAuthor: noob of noobs » Sat Sep 29, 2007 6:55 pm

Major improvement! Everything looks good, except that if I were you, I'd both replace the valve, and make all the parts larger or equal to the barrel's diameter, just since it's more efficient. Also, I'd recommend shortening the distance between the barrel and valve to cut down on dead space that'll probably decrease power. I'm not sure how galvanized steel reacts with water, so I'm not sure submerging it in water would be all that wise. A good ear can probably do the trick.
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Unread postAuthor: DYI » Sat Sep 29, 2007 7:00 pm

I have found that for 2" steel joints, you should use at least 60" of teflon tape for a good seal. Don't be shy with it. If you can, you could dunk the whole launcher in a tub of water or some other clear liquid to detect leaks easily.
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Unread postAuthor: GrafixBoy » Sat Sep 29, 2007 7:37 pm

DYI wrote:What is the chamber volume on it?

What is the point of that union on the end of the chamber? Is it used as a safety valve?

Haha. My brain cant calculate volume. but they are 3" in diameter. I cant remember the length. The union on the end of the chamber is what i had to use to cap off the end. There is a threaded cap piece screwed into that. Pardon me if I dont know the proper terminology of these parts.
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Unread postAuthor: DYI » Sat Sep 29, 2007 8:24 pm

Are you sure those parts aren't 2" and not 3"? They look awfully small for 3" pipe and fittings.
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Unread postAuthor: GrafixBoy » Sat Sep 29, 2007 8:51 pm

i think they are 2" my bad
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Unread postAuthor: iknowmy3tables » Sat Sep 29, 2007 9:01 pm

man that is crazy you got the coupler thats just there for no reason and the union used as an end cap,
heck I'd probably come with a similar result since I don't have any NPT taps n dies
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Unread postAuthor: GrafixBoy » Sat Sep 29, 2007 9:23 pm

iknowmy3tables wrote:man that is crazy you got the coupler thats just there for no reason and the union used as an end cap,
heck I'd probably come with a similar result since I don't have any NPT taps n dies

i used what i had. didnt buy anything
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Unread postAuthor: frankrede » Sat Sep 29, 2007 10:22 pm

Want any thing that resembles performance to come of it?
I say you throw in some dry ice and hot water into the chamber via the union and wait a while then blast away.
that should help with your dead space and short barrel.
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Unread postAuthor: nivekatoz » Wed Oct 03, 2007 6:07 pm

That thing must weigh a ton.....Try to use sch 80 aluminum pipe
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