My first piston cannon!

[hunter1992]

Well awile back I posted a piston I made for a cannon...Well Here is the cannon! It has a 3 inch diamator chamber by 3 feet long. The barrel was a scrap piece of 2 inch pipe i found so tell me if i need a longer barrel. I have pretty much no experience with air cannons so tell me what I need to do better next time.... I have shot it alot over the summer and I have been perfectly happy with it. Well the farthest shot I have recorded was about 400 yards. I don't know if thats far or not but it made me happy http://www.spudfiles.com/forums/piston-t7230.html


Google earth says this is 400 yards. It was a potato at I think 85 PSI.


Its ugly but im to lazy to paint it....

[jackssmirkingrevenge]

The barrel looks good for the chamber size, shame about the constriction at the breech and it looks like your pilot volume is far too big - any chance of an internal diagram?

One other thing, was it really wise to shoot with houses in your flight path? What was the projectile in question?

[rna_duelers]

JSR,some times you just have to accept that big pilot volumes happen in large piston cannons ok.*sounds like supporting parent*

Great cannon man,what was your ammo for that range?What pressure you run it at,just a few specs would be nice.Does look like its being restricted by the port of the valve though restricted alot.

[hunter1992]

Yah the pilot volume is way to big. I im going to cut it down soon. Yah I should have spent more time designing the breech. The gun goes from 3 inch to 2 inch all the way to 1 inch and back too 2 inch..... sounds like it would cause problems with air flow... The Projectile was just a potato. We were aiming for an empty field were the potato landed. There weren't any houses in any danger and considering the house that was shot over was my house I don't think we did anything wrong..

[jackssmirkingrevenge]

I accept that I'm a bit of a fascist on the issue of pilot volume, but I'm a big believer in efficiency - extracting the maximum performance from a given setup.

If you half your pilot volume, keeping the same pilot valve, then your pilot chamber pressure should drop twice as fast - that means faster valve opening time and great benefits in performance. If you're willing to live with not exploiting your launchers potential for maximum power, then that's fine with me - I just point people in the right direction, my two efficient euro cents, so to speak

edit:

The gun goes from 3 inch to 2 inch all the way to 1 inch and back too 2 inch..... Is that a problem with air flow??

A 2" port has 4 times the flow of a 1" port - in your case however, since your piston Tee is the same diameter as the barrel, this cannot be avoided.

Ideally in the case for a 2" barrel you should have used a 3" tee. Don't worry though, for a first effort you did very well, congratulations

[hunter1992]

Yah im just hesitating on cuting it down because the nipple for the ball valve had to be JB welded in to stop it from leaking.... Don't be afried to critize. main reason i posted was to find more improvments for next cannon I might have overlooked. Yah I thought about that but I had already made the piston before I even designed the gun and i about died when I saw the price for 3 inch fittings..

[jackssmirkingrevenge]

You could have gone for a one inch barrel and made it a foot longer, which would have given you higher velocity and longer range, though of course with a lighter projectile.

There weren't any houses in any danger and considering the house that was shot over was my house I don't think we did anything wrong..

If for some reason the shot fell short and you broke a window I'm sure your parents would have disagreed ah well, just be aware of your responsabilities and don't take any unnecessary risks.

[hunter1992]

Yah ill have to make a one inch barrel for it.

[jackssmirkingrevenge]

You can also try a 3/4" barrel for marbles and make it as long as you can, with that setup you'll get good velocity and penetration.

[MrCrowley]

Wow 400yards with a potato is quite a bit at 85psi.

Nonetheless it is very nice, nice and simple and gets the job done, good stuff.

[Maniac]

nice cannon yea 400 yards with a potato is pretty good at 85 psi

what is your piston made out of

also you seem to have an obsession with saying Yah every time you start a sentence no offense

[FORE!!!!]

he might be jamaican and was blazed when he thort the potato landed 400 yards away

[inonickname]

Try not to bump old topics man, this one was from '07

[FORE!!!!]

Try not to bump old topics man, this one was from '07

ooops i just google searched what the term bump means and my appologies ,i should probly look at the dates