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Plastic bag pistons?

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: tghhs » Thu Apr 02, 2009 1:51 am

yeah thanks guys, i did use epoxy for a previous piston but it's just to expensive for me, im only 16.

@ psycix, yeah the wood is for a servicable cap and yeah it's still airtight, yeah i'm not sure i'd be able to u screws through the pipe and cap, just coz of my skill. the clamp is pretty damm tough! the piston is very sturdy and it's defenetly lighter than a epoxy piston. also thanks.

yeah i'll keep u guys updated on how it all turns out, ohh and it took about 17-20 bags maby more, but i did sand alot of the ends because my mould had a largh lump in the end.

also i used extra virgin oil when melting it, shame i can't eat it, but the silicon just peeled of so i might try again with a different lube
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Unread postAuthor: jackssmirkingrevenge » Thu Apr 02, 2009 2:05 am

Biopyro wrote:I know how much you love it, but when I've used epoxy glue, it's often quite brittle. Admittedly this is cheap epoxy and in thin layers, but is it like this when scaled up too?

Quality epoxy makes a difference, and yes it will shatter when given a hard shock. Interestingly enough though, you can mitigate this by altering the proportion of the components, if you add less hardener it will harden but will still be a bit flexible.

Also, epoxy sticks to PVC when casting doesn't it?

Not if you lube the PVC properly, I've used anything from automotive grease to butter for this purpose :wink:

It has a higher friction coefficient and density.

Good design and lube can keep weight and friction down, you can make relatively complex shapes easily to retain strength while reducing weight, like so

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