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My ammo

Unread postPosted: Sun Sep 11, 2011 8:42 pm
Author: stuffbuilder
Just made some new ammo for my 2.5" air cannon: 90 calorie soda cans filled with concrete! They fit pretty good and certainly have some weight to them. Thoughts?

Unread postPosted: Sun Sep 11, 2011 8:44 pm
Author: jsefcik
Ummm are you shootin them using a piston valve cannon?

might be too heavy, thats alot of weight to shoot, i thought of the same thing but using regualr cola cans, but it didnt wanna break the housing of my piston cannon

Unread postPosted: Sun Sep 11, 2011 8:49 pm
Author: jrrdw
stuffbuilder wrote:Thoughts?


I think you should show the cannon, target and any damage you do with your "ammo". :D

Unread postPosted: Sun Sep 11, 2011 9:02 pm
Author: stuffbuilder
I will be shooting them with a piston valve gun, but unfortunately that gun doesn't work right now due to a bad piston seal (its a chamber-sealing valve). Given that college dorms don't allow potato guns, it will probably be awhile before the gun can be fixed.

And I had been planning on using regular cans, but they're just a bit bigger than a 2.5" barrel

Re: My ammo

Unread postPosted: Sun Sep 11, 2011 9:07 pm
Author: velocity3x
stuffbuilder wrote:90 calorie soda cans filled with concrete! Thoughts?


My guess is that the projectile weighs about 590 grams. Unless your cannon is metal construction using high pressure, I wouldn't expect much other than heavy recoil and broken parts. Hope it works for you.

Unread postPosted: Sun Sep 11, 2011 9:18 pm
Author: stuffbuilder
Its all schedule 40 PVC. If the cans are too heavy the barrel will probably just pop off the elbow coming from the valve (it isn't glued). And there is space around the cans that air can leak through

Unread postPosted: Sun Sep 11, 2011 9:33 pm
Author: Moonbogg
I don't get why piston housings break from heavy projectiles. Shouldn't the housing be able to withstand the full potential of the piston and chamber pressure? I mean, you should be able to plug the barrel, vent the pilot and the housing shouldn't break. At least that makes sense to me, I don't know.
Anyways, id love to see your ammo fly. I might be shooting some soda cans in the near future myself.

Unread postPosted: Sun Sep 11, 2011 9:50 pm
Author: jsefcik
I would like to do it, but dont wanna damage my piston or housing


I will be shooting them with a piston valve gun, but unfortunately that gun doesn't work right now due to a bad piston seal (its a chamber-sealing valve). Given that college dorms don't allow potato guns, it will probably be awhile before the gun can be fixed.

And I had been planning on using regular cans, but they're just a bit bigger than a 2.5" barrel


why are you worried about ammo ,if you cant shoot it anyways?

Unread postPosted: Sun Sep 11, 2011 9:52 pm
Author: DYI
Moonbogg, the issue with piston housings breaking isn't caused by internal pressure, but by dynamic loading on the housing from the recoil. This is, of course, particularly hard on tee valves. If the barrel was more securely fastened than we tend to bother with, it wouldn't be so much of a problem.

Unread postPosted: Sun Sep 11, 2011 9:55 pm
Author: jsefcik
DYI wrote:Moonbogg, the issue with piston housings breaking isn't caused by internal pressure, but by dynamic loading on the housing from the recoil. This is, of course, particularly hard on tee valves. If the barrel was more securely fastened than we tend to bother with, it wouldn't be so much of a problem.



so is it dangerous to shoot soda cans filled with concrete then?

Unread postPosted: Sun Sep 11, 2011 10:21 pm
Author: Moonbogg
DYI wrote:Moonbogg, the issue with piston housings breaking isn't caused by internal pressure, but by dynamic loading on the housing from the recoil. This is, of course, particularly hard on tee valves. If the barrel was more securely fastened than we tend to bother with, it wouldn't be so much of a problem.


Oh I got it now. I thought it was from the piston's kinetic energy when exposed to the full pressure of the chamber while using a heavy projectile. The recoil thing makes perfect sense of course. Like you said, it would be better to take some load off of the housing's joint with the chamber for heavier projectiles.

EDIT: For a PVC cannon in an over under design I would say it may be unwise to shoot soda cans filled with concrete, yes.

Unread postPosted: Mon Sep 12, 2011 2:53 pm
Author: jsefcik
Moonbogg wrote:
DYI wrote:Moonbogg, the issue with piston housings breaking isn't caused by internal pressure, but by dynamic loading on the housing from the recoil. This is, of course, particularly hard on tee valves. If the barrel was more securely fastened than we tend to bother with, it wouldn't be so much of a problem.


Oh I got it now. I thought it was from the piston's kinetic energy when exposed to the full pressure of the chamber while using a heavy projectile. The recoil thing makes perfect sense of course. Like you said, it would be better to take some load off of the housing's joint with the chamber for heavier projectiles.

EDIT: For a PVC cannon in an over under design I would say it may be unwise to shoot soda cans filled with concrete, yes.




more less dont shoot cans filled with concrete then!!! :D :D

Unread postPosted: Mon Sep 12, 2011 3:48 pm
Author: stuffbuilder
the issue with piston housings breaking isn't caused by internal pressure, but by dynamic loading on the housing from the recoil


I'll have to keep that in mind. Right now all the recoil would just go through the elbow and into the valve, but I can probably secure the barrel to the gun frame somehow to avoid that.

Unread postPosted: Mon Sep 12, 2011 3:52 pm
Author: mattyzip77
start off using filled tennis balls, use sand or whatever to fill themand see how that works first. A soda can filled with concrete seems way too heavy to me. Something is bound to break, and hopefully its not your skull!!!

Unread postPosted: Mon Sep 12, 2011 4:31 pm
Author: stuffbuilder
At first I was going to use sand, but there was some leftover concrete from a home improvement project that we needed to get rid of, so I used that instead. But to be completely honest, the gun has never fired. I had finished putting the piston in, but when I went to fill it up with air, it all leaked out through crappy O-ring grooves. School started before I could fix it.