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What makes a good two inch 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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Unread postAuthor: john bunsenburner » Mon Oct 27, 2008 5:02 pm

and what did you use to make it air tight? neoprene or rubber?
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Unread postAuthor: iisthemuffin » Mon Oct 27, 2008 5:04 pm

To seal the barrel i used a 2 inch rubber washer that i bought from lowes. Im not sure what exactly the "rubber" is though.
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Unread postAuthor: john bunsenburner » Tue Oct 28, 2008 11:00 am

rubber is either synthetic or natural, natural rubber is the stuff use in condoms, ballons and car tires. both are equally good natural rubber is a tad more expensive and as you might think it is pretty darn strong(a condom can fit up to 18Liters of air before tearing)
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Unread postAuthor: psycix » Wed Oct 29, 2008 4:22 pm

markfh11q wrote:Nonsense. Both me and Velocity have used 1-7/8" PVC rod for pistons before, with very good performance.

Very good performance, sure, but reduce the weight and the performance gets even better.

john bunsenburner wrote:I guess you could use a metal pipe with two enc caps filled with foam, this is strong, light and there is no problem with preasure

Metal and light usually doesn't match. Maybe use aluminum instead, or, go PVC.
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Unread postAuthor: john bunsenburner » Wed Oct 29, 2008 4:59 pm

a pvc pipe has a lower pressure rating at higher pipe width than for example copper, i guess the pvc is heavyer!
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Unread postAuthor: iisthemuffin » Wed Oct 29, 2008 5:28 pm

It doesnt really matter what the pressure rating is. As long as it is sturdy it wont hurt anything. Ive got part of a pill bottle on my piston and it works jsut fine.

A metal pipe with end caps would be MUCH too heavy to actuate at a decent rate.

And yes a piece of pvc is probably heavier than copper but seeing as how pvc is less expensive and will work for what i want it for, it is perfect.

Also, i will not be pumping a PVC cannon past the pipes pressure rating so im sure a nsf-pw end cap will hold up just fine.
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Unread postAuthor: john bunsenburner » Thu Oct 30, 2008 11:37 am

here pvc is acctually more expensive than copper becuase it cant be recycled and is like hyper taxed!
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Unread postAuthor: POLAND_SPUD » Thu Oct 30, 2008 12:39 pm

@ john bunsenburnerfor your first gun I advise you to order that 1/2" QEV.... that should suit your needs and it I assume it will cost you as much as making a piston valve....

you might try to ask them if they have 3/4" QEVs... last time I ordered stuff from them they had them... ( but it wasn't mentioned on their website )

EDIT sorry for going offtopic... I've thought that bunsenburner started this thread
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