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Using tap washers to build a 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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Using tap washers to build a piston

Unread postAuthor: evilvet » Sat Jun 18, 2011 2:52 am

Evening all

I am building my first barrel sealing pneumatic, small scale compared to many here. It will be low pressure job, no more than 80psi using PN18 PVC just as a learning curve for me.

It so happens that the chosen T-fittings happen to match I/D almost exactly with some old tap washers lying about in the shed. I have cut a length of 5mm brass tube that fits snugly over the valve stems, filled the tube with Tarzan's Grip and pushed in the tap washers. The result is a nice looking little piston about 40mm long that slides smoothly in the Tee.

Did I just waste an hour or so or is this baby likely to hold up ?

Comments appreciated.
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Unread postAuthor: jrrdw » Sat Jun 18, 2011 5:30 am

I've never used "Tarzan's Grip" before but if it sets up solid and has any kind of tensile strength chances are it will hold. What did you use for the sealing face? The tap washer?

I would be more concerned about the seal between the barrel and washer then the piston holding up. They have been used before but I think they are sketchy at best.
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Unread postAuthor: jhalek90 » Sat Jun 18, 2011 7:37 am

if that dose not work for you, hardware stores carry a rubber cork that will fit into your pipe, for around $0.50 USD (50 cent piston! yay!)
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POLAND_SPUD wrote:Anything is possible with the proper 3-way valve.
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Unread postAuthor: evilvet » Sat Jun 18, 2011 9:52 pm

jrrdw wrote:I've never used "Tarzan's Grip" ..snip..I would be more concerned about the seal between the barrel and washer


Sorry, Oz product. Tarzans Grip is a urethane one part glue, bonds most metals pretty well.
As to the sealing face I omitted to explain I glued two small O-rings on the face of the washer, they squash up nicely and get a snug seal.
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Attachments
Piston1.jpg
Piston overview
Piston2.jpg
Sealing face
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Unread postAuthor: jackssmirkingrevenge » Sun Jun 19, 2011 1:19 am

I'm not too fond of sealing faces held only by adhesive, unless it's a really thick sealing face cast into the piston. You might find it will come off after a few shots.
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