• Date JoinedAug 29, 2007
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erniehatt1 year ago
Not sure if this is still open, for discussion.
One thing I would like to know, when the piston is retracted, what gap should there be between the piston and barrel, I am thinking about 8mm, is that enough.
Mattrox4 years ago
Hi Just want to know what you think of my new instructable
Here's the link:
hollowpoint4 years ago
back again, after hours of mowing my dads lawn i obtained enough money to start building my pneumatic cannon. i decided to make a 3in. (75mm <- did i convert those units correctly?) porting piston valve cannon, the piston housing is a 4in (100mm) tee. the piston is a 3in (75mm) coupling with a metal plate with neoprene rubber on the end ( the 3in coupling fits very snugly inside of 4in PVC pipe) the pressure chamber is 4in (100mm) pvc pipe (i havent decided on the length yet) with the top portion of the tee / the end that leads to the barrel i put a 3in(75mm) clean-out adapter so that i could change barrel sizes with ease by having the barrels fitted with a threaded male adapter ( i also applied the same concept to the pressure chamber) even if its still a work in progress how wold you rate this cannon?
please tell me where i can get pvc
MrCrowley (author)  Hades di Angelo5 years ago
plumbing store/hardware store. do some research
Mattrox5 years ago
Hiya again I was thinking of running the main chamber at 200PSI and Having a 5 Shot magazine added to the bolt action.  On a scale of 1-10 how would rate this airgun With the main valve a ball valve and it running on 200 PSI? 
MrCrowley (author)  Mattrox5 years ago
PVC wont handle 200PSI safely, even if the rating is 260PSI. I'd only trust 15mm PVC and 200PSI.

Give me more details:

Chamber size and diameter
Barrel size and diameter
Ball valve size
Material of cannon - pvc or metal

I don't think you understand how unnecessarily big this cannon will be for the performance you'll get. Don't expect any 400m shots with golf balls, you'd be lucky if you got 250m.
Mattrox5 years ago
It ain't pneumatic but it's still Awesome. <a href=""></a>
MrCrowley (author)  Mattrox5 years ago
yeah I was one of the moderators who judged that contest
Mattrox5 years ago
(removed by author or community request)
MrCrowley (author)  Mattrox5 years ago

No offence, but these kind of cannons can be quite pointless, let me explain:

You want multiple shots so you don't have to keep refilling the chamber, well your main chamber is so big, it takes far longer to fill. Also, say you fill your big chamber to 100PSI, fill the second chamber, that drops to about 90PSI, next shot is at about, 80PSI, next shot at about 70PSI...not exact numbers, but im just showing you how fast the pressure drops.

With a ball valve, which is slow to open, you already are looking at pretty bad performance without a super long barrel.

Then you also have a small chamber, so you're looking at a small chamber, slow opening valve, short barreled, low pressured multiple shot launcher.

I don't know about you, but this doesn't sound very good to me. Plus it will be bulky, heavy and just plain huge.

It would work on small scale, say the main chamber is 1" pipe, 12" long, pressurized to 800PSI with CO2, and the secondary chamber is 3/4" pipe, 6" long and your valve is a hammer valve, piston valve or some sort and your barrel is like 12" or 6mm pipe...then it would be an alright launcher.

But it just doesn't work so well on a large scale.

Why do you need it to be multiple shot anyway?

qballcat5 years ago
can i ask you..Mr. crowley..WHAT went on in your head?
cheeseboy6 years ago
hey are you Mr. Crowley from spudfiles!
MrCrowley (author)  cheeseboy6 years ago
Yes I am! Cool huh?
hell yeah!