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Posted: Sun Mar 22, 2009 4:10 pm
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Posted: Sun Mar 22, 2009 4:16 pm
Use a larger bumper , like half a nerf football. Your piston weight looks a little beefy. Try and get it as light as possible.
Posted: Sun Mar 22, 2009 7:17 pm
This may not be the piston, but recoil problems.
I assume your cannon is over-under style?
I assume you haven't made a barrel support? (Strap the barrel down to the chamber with a distance-keep-block in between)
The recoil flexes the barrel, and that creates A LOT of force on the part where the barrel attaches to the chamber: the elbows.
Also your piston should be as light as possible.
http://www.spudfiles.com/spud_wiki/index.php/Over/under
I assume your cannon is over-under style?
I assume you haven't made a barrel support? (Strap the barrel down to the chamber with a distance-keep-block in between)
The recoil flexes the barrel, and that creates A LOT of force on the part where the barrel attaches to the chamber: the elbows.
Also your piston should be as light as possible.
http://www.spudfiles.com/spud_wiki/index.php/Over/under
Recoil puts a lot of stress on the elbows, barrel supports clamping the chamber and barrel together are recommended to reinforce the launcher and keep the barrel steady.
Posted: Sun Mar 22, 2009 8:28 pm
Chris, there's those tiny pics again. Post your photos in the 800 x 600 size range. Spudfiles will format it for you and then clicking on it will allow us to pull up the even larger pic.
A barrel support and clamp would probably have prevented this breakage. The tendency with an over and under like this is for the compressed air to try to push the barrel up and this very broken spot becomes a major stress bearing point.
A barrel support and clamp would probably have prevented this breakage. The tendency with an over and under like this is for the compressed air to try to push the barrel up and this very broken spot becomes a major stress bearing point.
Posted: Sun Mar 22, 2009 9:50 pm
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Posted: Sun Mar 22, 2009 10:23 pm
Even without a barrel, it's still a stress point. I predict a straped down barrel would have prevented this.chrissilvermancs wrote:but theres your problem there was not a barrel on it it was just the recoil of the piston and the air coming out i think. but i will try to strap it still.
Posted: Sun Mar 22, 2009 11:25 pm
It's actually worse without a barrel, because even if you did have a barrel support, it wouldn't do anything. 
Posted: Mon Mar 23, 2009 5:55 am
Air also has mass, and when that gets accelerated ALOT, it takes a lot of force. And what is the counterpart of that force? Yep, recoil.
Posted: Mon Mar 23, 2009 7:27 pm
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Posted: Tue Mar 24, 2009 12:38 pm
You could. But then the PVC threads would probably fail instead of the elbow (or L-piece as you call it)
Just make sure to support your barrel.
Just make sure to support your barrel.
Posted: Tue Mar 24, 2009 12:51 pm
All over and unders have the disadvantage of the joining elbow being the weak point. A gusset/barrel support would have stopped this from happening.