..... If the piston seals that well with the pipe it slides in, you may have a sealing face issue. How soft is the rubber? Is the piece of pipe inside the "T" square, flat, and clean?

The rubber is just a rubber seal I got at Home Depot. It is 0.0625" thick and seems soft to me.....

The facing ...

Well.... Actually the piston doesn't slide when the pilot side is sealed. The felt seal around the piston and the vacuum hold it in place. When it was just in the housing, it would slide under its own weight. I was trying to make it a smooth and slippery fit. I can re-apply the felt seal and get a ...

Donna know.....

Well.... Actually the piston doesn't slide when the pilot side is sealed. The felt seal around the piston and the vacuum hold it in place. When it was just in the housing, it would slide under its own weight. I was trying to make it a smooth and slippery fit. I can re-apply the felt seal and get a ...

Sounds like the piston is bouncing closed without the added back pressure of the projectile. ie. recompressing pilot volume combined with rapid depressurization of the chamber, is reversing the direction of piston travel.

The piston should not slide under its own weight.

What are you using for ...

deleted....

Sounds like the piston is bouncing closed without the added back pressure of the projectile. ie. recompressing pilot volume combined with rapid depressurization of the chamber, is reversing the direction of piston travel.

The piston should not slide under its own weight.

What are you using for ...

.....but whatever you do, don't load it then cover the muzzle with your hand! Especially with a faulty piston. It may just be a marshmallow, but Technician puts them through car doors. I never found out exactly what the problem was, but what is the piston made of?.


I always cover the muzzle ...

I could come up with a spring but I don't know if that is my problem. I will try it if need be.

The one I am basing it on works down to 20 lbs PSI and I have been playing at 40-60 PSI today. I am running with a constant connection to my air compressor.

Maybe I need a larger chamber or flow from ...

I am sorry....

When I "dry fire" the gun, the piston will re-seal the barrel every time and "semi-auto" but when I put in ammo and fire it, the piston won't seal the barrel. I have to place my hand over the end of the barrel and build up pressure and release for the piston the seat.

Barry

Actually from what I've heard, you can actually tap plastics like PVC with only the metal fitting threads, you just wrench it on and it creates threads itself. Note, I haven't actually ever tried this as I believe you wont get straight threads but it might help save some money. :roll:

I am new to ...

Guys,

Just played with my first build..... a cannon very similar to http://www.spudfiles.com/forums/my-second-generation-piston-valve-cannon-t20966.html

It is for shooting marshmallows in the yard with my son. We have been having a blast tonight with it. However, I have one problem....

It will ...

Mr Gadget,

THANKS..... I was getting there eventually.... I really appreciate the details. Really helped the process. Will let you know how things go.....

Thanks again,

Barry

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