SpudFiles

I want to use a pencil eraser for a piston because it fits tightly but I don't know if it will hold up to 400 psi without the barrel becoming a cookie cutter. I couldn't find any rubber stopper that would fit well at the hardware store either, so what do you think?
:occasion5:

you could add something to the barrel to increase its wall thickness but a rubber would still get cut up bad or put the seal on the barrel just have a flat hard piston

Ok, I might find something to put around the barrel, but my barrel is to wide to integrate a seal onto it and have a hard piston. There wouldn't be a lot of room around it for the air to flow.

At 400psi, with multiple uses, your piston will probably get torn apart. Erasers, after all, are designed to do so.

I'd model the forces on the eraser with some weights and see what happens.

I already did, but without weights. Just the force of my hands got a circle etched into the front of the eraser. I'm thinking cast epoxy now with some neoprene on it but will the rubber stay on if I just epoxy it?

Heck no, is wont last 200 psi, I already have a thread about this. What i did was use a vinyal keychain and use the chamber to cut the piston out, like JSR.

I sharpened a piece of the chamber and punched some neoprene out then put it at the bottom of a section of the chamber pipe. Then I lubed it and put in the epoxy. It is curing right now so I'll take it out tomorrow. Should the epoxy be good enough to hold on the neoprene? It's Loctite 5 minute epoxy.

So you cast an epoxy piston, seems like way more work than nessacery, sudt use a keychain thats like a 1/4 inch thick

I have another pengun on the way. I'll try a solid rubber piston in that one.
Pick the first one or the second one:
The schrader can be hidden or not. Either way, the front part of the pen would need to be removed in order to fire it.

I took the piston out of the mold today, it was tough but it came out. The rubber on the face came off. The epoxy was not enough to keep it on. A solid rubber piston is in order.

what i did for my pen guns is i used contact adhesive to stick it to the piston and it seems to stay alright

use super glue or rubber cement that you get in tire repair kits to hold rubber down, epoxy just wont stick to rubber

Are you sure super glue will hold it cause it's not servicable.

test it with a scrap bit of rubber and some wast epoxy and see if you think it is strong enough

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