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piston too powerfull

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piston too powerfull

Unread postAuthor: chrissilvermancs » Sun Mar 22, 2009 4:10 pm

I'm think my piston is too powerful lately i have only doing 50psi shots but i got this new bumper on and i decided to go to my max 110psi. i haven't shot it with that much psi sense summer. it shot but the second the piston hit the bottom it bent the whole valve cracking the part that connects to the tank I'm going to replace it but what can i do to prevent this.

as u can see in the pictures it was not a problem of not enough cement it literary snapped the PVC.
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the piston
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Unread postAuthor: jonnyboy » 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.
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Unread postAuthor: psycix » 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
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.
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Unread postAuthor: starman » 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.
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Unread postAuthor: chrissilvermancs » Sun Mar 22, 2009 9:50 pm

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.
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Unread postAuthor: starman » Sun Mar 22, 2009 10:23 pm

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.


Even without a barrel, it's still a stress point. I predict a straped down barrel would have prevented this.
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Unread postAuthor: mark.f » 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. :)
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Unread postAuthor: psycix » 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.
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Unread postAuthor: chrissilvermancs » Mon Mar 23, 2009 7:27 pm

is there anyway i could use a lathe and put the same type of threads on a meal L as the pvc type because thats a easy way to do it and i know a hardware store that has a lathe.
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Unread postAuthor: psycix » 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.
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Unread postAuthor: jrrdw » 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.
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