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ball piston?

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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ball piston?

Unread postAuthor: pyromaniac » Sun Jul 01, 2007 7:07 pm

i remember a topic on haveing a ball piston. Well today at ym family ruinion my cousins brought lacross sticks and a ball. i began to think. would the rubber be enough for a seal? Its a kind of hard rubber though are racquet(sp?) balls rubber too if so are they a lighter(i dont know a term for like a softer rubber).

If so then you could have a ball as your piston
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Unread postAuthor: hi » Sun Jul 01, 2007 7:17 pm

i would imagine you could, i see no reasone why you couldnt. it would have to be an absolute perfect fit though.
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Unread postAuthor: goathunter » Sun Jul 01, 2007 7:22 pm

Hmm, big bouncy balls ought to do it for smaller pipe.I've seen some as big as 2".That would do the trick.
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Unread postAuthor: hi » Sun Jul 01, 2007 7:26 pm

i think bouncy balls are to hard. maybe like a gasket glued onto the seal face.
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Unread postAuthor: potatoflinger » Sun Jul 01, 2007 7:30 pm

Or you could use epoxy to fasten the ball to the front of a piece of pipe and use the ball as the seal for the piston, because it's round shape would make it a perfect piston seal for different sized barrels, but you could have a pipe that is the perfect size for a piston.
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Unread postAuthor: goathunter » Sun Jul 01, 2007 7:52 pm

You could actually seal the face off with a flat piece of plastic if you wanted to.Hardness of the material has very little to do with the seal.It mainly depends on the flatness of the sealing face.The only thing soft rubber does is warp slightly to make up for the inaccuracy of the cut on the sealing face.For my pistons I use hard gasket material.Slightly harder than a bouncy ball.Those pistons seal off just fine.

I like potatoflinger's idea. Although I'd cut the ball in half on the seam to reduce weight and allow a greater area for the epoxy.
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Unread postAuthor: pyromaniac » Sun Jul 01, 2007 9:43 pm

potatoflinger wrote:Or you could use epoxy to fasten the ball to the front of a piece of pipe and use the ball as the seal for the piston, because it's round shape would make it a perfect piston seal for different sized barrels, but you could have a pipe that is the perfect size for a piston.


this is what i meant use the ball as the sealing face its rubber but i dont know if its to tough to seal.
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Unread postAuthor: paaiyan » Sun Jul 01, 2007 9:48 pm

goathunter wrote:You could actually seal the face off with a flat piece of plastic if you wanted to.Hardness of the material has very little to do with the seal.It mainly depends on the flatness of the sealing face.The only thing soft rubber does is warp slightly to make up for the inaccuracy of the cut on the sealing face.For my pistons I use hard gasket material.Slightly harder than a bouncy ball.Those pistons seal off just fine.

I like potatoflinger's idea. Although I'd cut the ball in half on the seam to reduce weight and allow a greater area for the epoxy.


But if you cut it in half I would think it would have a tendency to not stay aligned properly, i.e. it would flip around so it wouldn't seal.
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Unread postAuthor: goathunter » Mon Jul 02, 2007 8:00 am

Flinger,was talking about attaching it to a piece of pipe.That would keep it all aligned.The ball would only be the sealing face.Definitely, you couldn't cut the ball in half and have it act independently as a piston.I'm building a new coaxial,I might try a bouncy ball or big plastic ball as the piston.
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Unread postAuthor: paaiyan » Mon Jul 02, 2007 8:18 am

goathunter wrote:Flinger,was talking about attaching it to a piece of pipe.That would keep it all aligned.The ball would only be the sealing face.Definitely, you couldn't cut the ball in half and have it act independently as a piston.I'm building a new coaxial,I might try a bouncy ball or big plastic ball as the piston.


Ah, I see what I missed. I suppose it should work quite well in that situation, assuming it's the proper size to seal. I do wonder how much friction a bouncy ball would put on the sides of the chamber preventing it from moving as quickly as it shoudl though.
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Unread postAuthor: Hawkeye » Mon Jul 02, 2007 8:36 am

There was a guy who came on here and explained why a ball works as a piston and why it is the best option . Think of how little of the ball actually touches the walls of the cylinder compared to even a short regular piston.
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Unread postAuthor: goathunter » Mon Jul 02, 2007 8:43 am

I do wonder how much friction a bouncy ball would put on the sides of the chamber preventing it from moving as quickly as it shoudl though.

I would think it'd tend to roll a bit.I'll try it in my 1 1/2" coaxial.


There was a guy who came on here and explained why a ball works as a piston and why it is the best option . Think of how little of the ball actually touches the walls of the cylinder compared to even a short regular piston.

That's what I was thinking.I wonder who thought the ball piston up?It'd be nice to see how it worked.They've been using them in check valves forever.So it should work out nicely.The only thing I'm a little worried about is how well the ball will move back.If I leave the gun connected and use it like that the ball may not reseal very fast.Since the air will escape all around the ball.
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Unread postAuthor: spud yeti » Mon Jul 02, 2007 9:05 am

I will go try this piston on my coaxial just now. I think it has some good potential!

I'm a little worried about is how well the ball will move back

I think it should move back well provided it is a good fitting ball in the tube. The only thing Im thinking is maybe the ball spins in the tube?
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Unread postAuthor: pyromaniac » Mon Jul 02, 2007 12:18 pm

One of my questions hasent been aswered yet. abotu how hard a rubber could be to seal. A lacrosse ball is a rather tough rubber. Could a mouse ball work as a piston so it seems the rubber on that is softer.(or however you say it.)
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Unread postAuthor: rednecktatertosser » Mon Jul 02, 2007 12:25 pm

I dont think the hardness of the rubber matters on a seal, just so long as the sealing face is flat and they seat against each other properly
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