SpudFiles

I'll be making a gun that uses about 100-150psi what is the best type of rubber to use? (fyi: I want to make one of the pistons with the screw through the rubber) I wont be able to repair it as It will be sealed and It uses a 3/4" pvc barrel (sch 40). Thanks

I know that rubber pipe caps are real thick and probably will work good

If you cut out a perfect circle it works as a piston it's self. You can get thoes in the ABS section.

Yeah find something metal that's the diameter you need like a copper coupling and sharpen it up then punch out the cap with a mallet.

A sharpened steel pipe makes uber sweet pistons!

Or, if you have access to a drill press you can use a circle cutter and make great circles.

And destroy the edge of the rubber!

Or... you can just get a gasket cutter!

Anyways, that's not the point. He asked what type of rubber, and we're sitting around here yelling about different ways to cut it.

I suggest neoprene, of a relatively harder composition that the stuff you see at the hardware store. I've still got a bit left of my first 4x36" piece of 70A shore durometer neoprene, and I use it all the time for random sealing jobs. Keeps air back at 150 PSI in my copper gun... should work for you.

Personally, I'm a big fan of 30A.

Just a question, how thick should it be approximately(metric and imperial please)

I like 1/8" or about ~3.2mm thick.

I would try 30A, and actually I've had incidences with the 70A where it had to seal against an uneven sealing face, (a small marble coaxial), and I thought to myself, <I>this would be easier if the neoprene was softer</I>. But, with a little work smoothing the surface, or even just stepping up the pressure to around 150 PSI, you get it to seal. I probably should order some 30A, (well, maybe a little stiffer than that), with the parts I gotta order in a few weeks or so for my hybrid.