SpudFiles

I would suggest you go here:
http://www.spudfiles.com/forums/search.html

Or straight to the Pneumatic Cannon Showcase section and look through cannons which have similar design features to yours, such as a 3/4" piston housing in a tee. Then you can see how other people did it

ok thanks.

and if i screw it in the side... would teflon tape hold it?

If by hold it you mean hold pressure, then yes teflon tape works great for that. Just make sure you drill a hole small enough that the threads dig into the pvc and leave grooves, it should take some effort to thread in the first time. I would suggest a threaded schrader valve like this one:



Why is there an o-ring between the washer and the 3/4" pipe on the left of the piston?

to seal the back so all pressure is going out the barrel. is that not needed?

ps. i already have the threaded schrader. thnx for comfirmation

Well based on your drawing i assumed that you are using one of the conical reducers, not a reducing bushing, and that it would slip over the section of 3/4" pipe that would extend slightly out of the tee. In that case an o-ring would not be necessary, but if it is a bushing that is pushed into the tee then yes its very important.

thanks i understand. so i'll use a 3/4 x1/2 bushing with o ring... is the washer needed or not

Hey guys,
I redesigned it this morning without the stock or anything so its a close up. I'll post it later, because I'm at school now lol. Spudfiles isn't blocked!

ok so heres the new scan of my final drawing-

i have the same problem... im thinking a little rubber gasket would do the trick

How exactly are you making the sealing surface that the piston pushes against to seal the barrel off? I'm in the middle of designing a gun of my own, and this is where I'm stuck

Neoprene gasket should work, then again I also am working on a piston valve. Points to Gun Freak for actually getting up and doing it, Im still "thinking" about it.

Mine's almost done. All I got to do is get the neoprene washer and put it on my piston, which I made (it's hot glue around a wine cork) then I have to glue the rest together. Most parts are already glued.