SpudFiles

Well, I don't know what I can get to seal my piston right, it has to seal against a odd surface.What can I do Mabey my design isn't right,all I can do now is change the piston and nothing else.

What are you using as the sealing face? Yea, your sealing area is weird, but because of the "funnel" shape of the bushing I would think that it would center. What are you using to fill the cannon? Secondly, your equilization point may be to big for your air source.

Well after seeing what you have, you could make a new piston with the head sticking slightly inside the barrel and a round rubber washer or big oring rite around the bottem of the inserted part that slides into the barrel. Use the end of the barrel as a guide when building the new piston. Maby??

the barrel should stick out of the bushing

I am going to have to experiment with sealing faces I think.I won't put an equilization point because the piston dosn't fit prfectly inside the larger pvc(about 1mm of play).This will also held to seal the piston.What should I use washers or o rings?

I am making a valve almost identical to this one, except chamber sealing. I am using, for the main seal, a "toilet shank ring" or something like that. I've found it fits perfectly with the funnel shape of the bushing. As for the rear end of the piston, I am using a disassembled "test plug." In between is a "cast iron adapter" fitting (PVC), which is just a touch smalller than normal 2" pipe I will post a picture of my prototype piston if wanted.

Thanks,you just gave me a few ideas,I'll be sure to test some of those 'toilet washers'.