need help with penumatic crusher

[fidgety]

I am making a penumatic crusher it will be a tube of pvc that is connected my compressor at one end and capped at the other the capped end will have a hole in it allowing air to escape inside the tube there will be a metal cylinder that crushes the thing

[Freefall]

This may help.
http://www.penny-arcade.com/comic/2002/10/11

So, you've got a capped tube with a hole in the end with a thing inside that crushes the thing. Do I have that right?

Maybe you could re-phrase your help request in some form that makes a little bit of sense?

[shadowscion]

So what's the question again?

[TurboSuper]

So you just want to push air behind a piston until it crushes whatever is on the other side?

Sounds simple enough, what exactly do you need help with?

[fidgety]

sorry I didn't have enough time to really complete my topic.
but here is what i am trying to do:
I am trying to create a piston in essence that slams down on a object
using compressed air to push the piston I hope to reach crushing power of in excess of 100 pounds per inch I am having difficulty attaning a seal for my piston please help

[GalFisk]

O-rings will work.

[fullmetaljacket]

Can't you simply build a pneumatic cannon with a short fat barrel? Have someone machine a nice solid metal slug that is a tight enough fit for the piston, perhaps with grooves for o-rings as GalFisk suggested.

[fidgety]

the problem is that I have no way of machining apart from dremel tools.
So i'm pretty much sunk. Also should I drill a hole in the lower part of the barrel to keep the air on the object compression side of the slug from equalizing the pressure and causing the slug to go nowhere?

[fullmetaljacket]

find the biggest metal rod you can get your hands on and wrap it with duct tape till it fits the barrel

Alternatively, fill a soup/coffe/whatever-fits-your-barrel can with concrete and use that as the "crusher".

Are you planning to close the tube at both ends (which will probably mean the destruction of the cap at the crushing end)? In that case, a vent hole is a good idea

[fidgety]

thanks