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My first pneumatic piston air cannon.....sadly doesnt work

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: LikimysCrotchus5 » Thu Sep 20, 2007 6:06 pm

Well i was asking about the sheet pvc at first because i wanted to get that but homedepot didnt have it so then i had to get sheet metal. I was just wondering so for me next piston i can use it and it would be easier to cut.
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Unread postAuthor: CannonCreator » Thu Sep 20, 2007 6:13 pm

I couldn't find Sheet PVC so i had to use sheet metal


Sheet pvc is really easy to make yourself. This is spuddins site adn he shows how to make sheet pvc http://www.freewebs.com/spuddin/pvcsheet.htm

After you do it a few times you can get it bassically perfectly flat. Hope this helps!
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Unread postAuthor: LikimysCrotchus5 » Thu Sep 20, 2007 7:35 pm

Thx that really does help now i dont have to look for it no more and i got some extra 3 inch pvc thx for the info.
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Unread postAuthor: jackssmirkingrevenge » Sun Sep 23, 2007 3:05 am

This seems to be your problem, the blue line indicates the outline that the rubber disk should have to be effective.
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Unread postAuthor: dongfang » Sun Sep 23, 2007 4:17 am

Hi,

There are a few things I don´t understand about that valve:

Which end of the rod is which? The one called "The sealing part of the barrel" in the image captions, perfectly round with 4 visible metal squares in it, does that seal against the barrel?

And does "The bumper", not perfectly round, sit in the back (breech end) part of the tee?

If that is the case, I see a problem: "The sealing part of the barrel" should seal perfectly against the barrel, but not necessarily against the sides of the tee. "The bumper", also called the opener piston, should seal against the sides of the tee. Its works like a piston that pulls "The sealing part of the barrel" away from the barrel, opening the valve. So, as a piston, it should be perfectly round, and seal against the cylinder wall (the tee).

OR did I get something mixed up?

PS: Since you do not cement the piston on any PVC, you could use some other plastic than PVC for a redo. For example, I have seen some thick, inexpensive chopping boards of some other semi-soft plastic here. They would be perfect, I believe.

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Unread postAuthor: LikimysCrotchus5 » Sun Sep 23, 2007 12:27 pm

Dongfang - The sealing part of the psiton is the inner tube
Image

The bumper is the part is the mousepad.
Image

I made it so that the bumper ditd at the back part of the T but im not sure if i left too much space for air to flow into the chamber. I think what your saying could be the problem but im not sure if i understand what you're saying about the piston sealing against the sides of the sides of the T but i think i know what you're saying. Also i dont understand what your saying in the PS section of your post.

PS: Jack i did get bigger washers too.
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Unread postAuthor: dongfang » Sun Sep 23, 2007 12:35 pm

Hi,

OK I think I got the two of your disks reversed in my thinking about the valve. OK, so the fat disk, which is not quite round, goes against the barrel, while the perfectly round one is the opener piston. That should work.

In the PS, I mean: You don´t need PVC for a new disk. You could use other plastics too, for example a disk cut from a plastic chopping board. These are more or less unbreakable, and have a good hardness, I believe.

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