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I'm starting my second pneumatic cannon and it is a pen gun type thing. My problem is the piston won't seal onto the barrel. I used wd40 but it didn't help much. The barrel is a piece of an arrow shaft. The chamber is aluminum pipe. and the piston is a little piece of round plastic that fit in the chamber well. It has a bit of red rubber glued on the end of it. I've never posted on spudfiles before, so I might not get the photo attachment thing right.

Usually a piston will leak if the barrel or sealing face isn't squared up correctly. You could also try using grease on the piston rather than wd40; it usually seals a little better.

How did you make the barrel removable?


<edit: 2k posts. Yeehaw wasted time

Yeehaw wasted time

As Fnord said, make sure its all square and clean, if the barrel isn't clean where the piston rests it probably won't seal.

WD40 and rubber seals are a bad idea, in fact most lubricants tend to make the problem worse. How about a solid rubber piston? Easy to cut with a section of sharpened chamber tubing.

Fnord wrote:<edit: 2k posts. Yeehaw wasted time

Fnord wrote:Usually a piston will leak if the barrel or sealing face isn't squared up correctly. You could also try using grease on the piston rather than wd40; it usually seals a little better.

How did you make the barrel removable?


<edit: 2k posts. Yeehaw wasted time

The barrel is not actually removable, I had to un-glue it. I guess I'll try solid rubber.

is the barrel properly centred? some advice on how to guarantee it here: http://www.spudfiles.com/forums/epoxy-c ... t8916.html

sometimes when you go up to higher pressures, the rubber will compress onto the barrel and make a seal, it has worked for me

Thanks for the help. I made a hot glue piston and I have epoxyed evereything together now, I just have to wait for it to dry.