SpudFiles

After a hiatus from the hobby of at least 6 years, I brought up this potato gun I built when I was a kid in middle school while I was having a beer with a few buddies. It got me thinking about how much I miss senselessly destroying objects with a pneumatic cannon. The swat gun has been laying in the tree line where it came apart for longer than I'd like to admit, and with my current knowledge in fabrication and pneumatics plus a little more financial stability, I think I could blow my old cannon out of the water. I'm planning on 40 feet of 4" air chamber with a higher flowing valve and higher pressure capabilities, as well as (possibly?) a barrel as long as 40 feet. Plans are to start acquiring parts as soon as possible and to have it done by late spring. Looking forward to contributing as a slightly more knowledgeable member than I was in the past
It's good to be back fellas.
-Alex

Skip the 4" PVC - you've graduated to metal chambers by now! Use 2X 40lb propane tanks and a homemade piston valve or a balanced spool valve like techs!

I was just doing some math and 30 feet of 4" in a unique configuration I have had in my head for a few years seems the most fiscally responsible and easiest to work with, seeing my compressor is only capable of ~150 psi, I don't see any reason to go with steel tanks. As far as updating my old piston valve design, I have a few ideas I'm going to incorporate. I'm interested to see if anything I have planned is off the beaten path from what is common in the world of spud guns these days. I'm FAR out of the loop. I was considering high density foam encased in fiberglass, sanded smooth and coated in some sort of smooth enamel for a piston. I have a few other ideas as far as the valve are considered but until I draw it up I won't run on too much.

I'll look forward to seeing where this goes!

I'm surprised I recognize as many members as I do! there are some veterans around here.
The old cannon was typically operated in the 40-50 psi range and very rarely over. I want to triple that and average 120 psi with an equivalent chamber volume, longer barrel and more efficient valve.

Welcome back ! Oh years go past so fast.. I've been here nearly 10 years and before that on spudtech and I'm still reading this forum every day !

It's been 6 years? WOW....Welcome back. Looking forward to the next edition...

I'm with mobile chernobyl on this one, I reckon you could use some smaller metal tanks but instead make a large low-mix hybrid

I'm FAR out of the loop

Not a whole lot has changed. Piston valves were common when you were last here but they're probably much more so now. As MC mentioned, technician1001 introduced us to a useful balanced piston design that I can't quite recall the name of. Might be worth looking in to though. There are probably a lot more hybrid cannons now, though they are still built fairly rarely. Probably a dozen or so piston hybrid cannons though, don't think there were any of those back in 2008.

I haven't played around with PVC for some time now, probably because as I get older I become less inclined to stand next to a pressurized plastic chamber! Of course, they can be made completely safe but they are also very fragile as you found out with SWAT

Perhaps you could try for some long-distance records. With a barrel similar to that of SWAT, you shouldn't have any trouble fitting some tracking device in the projectile.

Wecome back to the fray!

MrCrowley wrote:As MC mentioned, technician1001 introduced us to a useful balanced piston design that I can't quite recall the name of.

QDV.

Perhaps you could try for some long-distance records. With a barrel similar to that of SWAT, you shouldn't have any trouble fitting some tracking device in the projectile.

Have a read http://www.spudfiles.com/spud-cannon-re ... 22491.html

Due to the pull resistance at higher pressure on a QDV due to seating of the o rings, unless you use a sizable slide hammer to knock it open, I do not recommend an un piloted QDV in a 4 inch size. You might not be able to pull it at pressure. I have on the other hand toyed with piloting a larger QDV with a smaller trigger one by using a T to inject the initiating blast between the projectile and piston. I can point to a video that shows an adult having to pull a 2 inch twice to trigger it because too little force was used the first time.

You can hear it fail to fire on the first try.
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schmanman wrote:I was just doing some math and 30 feet of 4" in a unique configuration I have had in my head for a few years seems the most fiscally responsible and easiest to work with, seeing my compressor is only capable of ~150 psi, I don't see any reason to go with steel tanks.

The main reason to use steel tanks in a low-pressure pneumatic is, after you leave it sitting for years you won't have an 'oh-god-is-it-going-to-blow-up' moment when you decide to dust it off again

UV exposure and cold weather also become irrelevant.