Piston in copper and brass updated 05/03/08 Damage pics

Cannons powered by pneumatic pressure (compressed gas) using a valve or other release.
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Gippeto
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The stirrup pump I built has been driving me up the wall. Significant pressure just sitting there with nothing finished to use it in.

So, I got the copper gun bug too. Picked up the last of the brass fittings friday morning, and got it working. Still want to add a stock from an old break-barrel, and I'm not happy with the rear sight yet.

I have also started a Hammer-piston(I'm about half done) to try in this. :)

Will try to get some more pics and maybe a vid sunday.

Quick specs :

Barrel 1/2" x 36" type M
Chamber 3/4" x 14" type M
Piston is a floating o-ring type machined from nylon (hammer piston is similar)


Youtube

http://www.youtube.com:80/watch?v=7FBsQ ... ture=email
[/b]
Attachments
Exploded_view.jpg
Piston close up.jpg
Completed Cu gun.jpg
Finished the hammer piston. I will be testing and comparing the two for performance soon.
Finished the hammer piston. I will be testing and comparing the two for performance soon.
A commercially available check valve with a few mods.
A commercially available check valve with a few mods.
New fill setup. Seals when finger tight. (no wrenches)
New fill setup. Seals when finger tight. (no wrenches)
New sights, ready to mount.
New sights, ready to mount.
Showing two different impacts and pieces I was able to find. Also unfired round for comparison. Shots were @ 400psi and 2 yards range. 1/2 ounce fishing weight/hot glue ammo.
Showing two different impacts and pieces I was able to find. Also unfired round for comparison. Shots were @ 400psi and 2 yards range. 1/2 ounce fishing weight/hot glue ammo.
Beer can filled with water and shot with 1/2 ounce fishing weight/hot glue ammo @ 400psi. 5 yard range.
Beer can filled with water and shot with 1/2 ounce fishing weight/hot glue ammo @ 400psi. 5 yard range.
Just because its a cool shot.
Just because its a cool shot.
Beer can exploding.jpg (13.63 KiB) Viewed 11558 times
The exit side. 3/4" spruce plywood. Shot at a range of 5 yards. 1/2 ounce fishing weight/hot glue ammo @ 400psi
The exit side. 3/4" spruce plywood. Shot at a range of 5 yards. 1/2 ounce fishing weight/hot glue ammo @ 400psi
Slug mold and ammo.
Slug mold and ammo.
Last edited by Gippeto on Sat Jun 21, 2008 1:00 am, edited 8 times in total.
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jackssmirkingrevenge
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Looking very good and just the sort of project that would benefit from higher pressures, bring on the damage pics :)
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MrCrowley
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Very nice, looks great. Let us know how the performance is :)
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Antonio
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Hey nice job! I tried making one as well but still didn get the concept of a piston. Does the diagram show the same setup as your piston?
Image

What I dont get is how the pressure pipe is from the bottom with ur setup and while the piston can still open? I mean in the picture I put here it makes sense that the pressure is from the front and equal to the back pressure on the other side.
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FordGtMan
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Lol Ant, you can figure out how to make semi auto bb guns but cant figure out how a piston worked?
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Antonio
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FordGtMan wrote:Lol Ant, you can figure out how to make semi auto bb guns but cant figure out how a piston worked?
It may sound stupid but I dont get how the air supply can come perpendicular to the piston and still open the piston when the pressure drops behind the piston. I never really went into this business, but I heard it has powerfull potential.
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is this the key??
is this the key??
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DYI
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The piston is filled from behind, not on top. Does that clear things up? It's just a simple barrel sealing piston valve.
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Hawkeye
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The barrel extends back to at least the middle of the T and the piston is pushed forward to meet it. When the piston moves back the air follows a path back and then "around the corner" and out the barrel.
Remember the barrel is smaller in diameter so there is considerable area for the piston surface outside the barrel to have air push against it.

Study the diagrams on the sticky.

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Gippeto
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Ant, your diagram is of a chamber sealing piston. As mentioned, this is a barrel sealing piston.

Hawkeye described its workings.

I'll put up a paint drawing that I have of my marshmallow gun. Have a look, and I'll walk you through it if it's still unclear.
Attachments
Piston valve 2.JPG
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bluerussetboy
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very nice, very nice.
the lines of copper launchers are smooth and the pressures used are amazing.
i hope this project turns out better than expected.
this is making me feel lazy. i really need to to get off my ass and put together my copper launcher, but the skiing this year is phenomenal. :)
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Antonio
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Ah k so the barrel sticks a bit backwards so that the piston also has a surface area at the front. I have been looking at Jacks piston pictures but never understood how it really worked. But when the barrel is partly inside the chamber I get it. Thnx Gippeto and Hawkeye!
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MrCrowley
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@ant

<A HREF="http://www.spudfiles.com/forums/how-to- ... l">Read</a>
<A HREF="http://www.spudfiles.com/forums/piston- ... l">Read</a>

:)
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Sticky_Tape
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Can somebody tell me how the hell you download ggdt I did everything the website says but the damn thing won't work.
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Novacastrian
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Ant, look at <a href="http://www.spudfiles.com/forums/the-ham ... html">this thread</a>
Lovely gun Gippeto, nice work :)
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jon_89
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Nice gun. What is your piston made from?
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