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

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Piston in copper and brass updated 05/03/08 Damage pics

Unread postAuthor: Gippeto » Sat Mar 08, 2008 3:16 pm

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]
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Attachments
Piston close up.jpg
Exploded_view.jpg
Completed Cu gun.jpg
New sights.jpg
New sights, ready to mount.
New fill setup.jpg
New fill setup. Seals when finger tight. (no wrenches)
Check valve parts.jpg
A commercially available check valve with a few mods.
Hammer-piston and piston.jpg
Finished the hammer piston. I will be testing and comparing the two for performance soon.
plywood exit hole.jpg
The exit side. 3/4" spruce plywood. Shot at a range of 5 yards. 1/2 ounce fishing weight/hot glue ammo @ 400psi
Beer can exploding.jpg
Just because its a cool shot.
Beer can exploding.jpg (13.63 KiB) Viewed 7245 times
Destroyed can.jpg
Beer can filled with water and shot with 1/2 ounce fishing weight/hot glue ammo @ 400psi. 5 yard range.
Steel plate shots.jpg
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.
Mold and Ammo.jpg
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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Unread postAuthor: jackssmirkingrevenge » Sat Mar 08, 2008 3:29 pm

Looking very good and just the sort of project that would benefit from higher pressures, bring on the damage pics :)
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Unread postAuthor: MrCrowley » Sat Mar 08, 2008 3:53 pm

Very nice, looks great. Let us know how the performance is :)
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Unread postAuthor: Antonio » Sat Mar 08, 2008 5:24 pm

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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Unread postAuthor: FordGtMan » Sat Mar 08, 2008 5:32 pm

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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Unread postAuthor: Antonio » Sat Mar 08, 2008 5:37 pm

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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naamloos.JPG
is this the key??
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Unread postAuthor: DYI » Sat Mar 08, 2008 5:44 pm

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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Unread postAuthor: Hawkeye » Sat Mar 08, 2008 5:47 pm

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.

Talk about running before you walk. ;)
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Unread postAuthor: Gippeto » Sat Mar 08, 2008 6:05 pm

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.
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Attachments
Piston valve 2.JPG
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Unread postAuthor: bluerussetboy » Sat Mar 08, 2008 7:40 pm

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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Unread postAuthor: Antonio » Sat Mar 08, 2008 9:26 pm

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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Unread postAuthor: MrCrowley » Sat Mar 08, 2008 9:35 pm

@ant

<A HREF="http://www.spudfiles.com/forums/how-to-make-a-pneumatic-cannon-with-a-2-piston-valve-t10381.html">Read</a>
<A HREF="http://www.spudfiles.com/forums/piston-valves-explained-visually-t8157.html">Read</a>

:)
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Unread postAuthor: Sticky_Tape » Sat Mar 08, 2008 10:27 pm

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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Unread postAuthor: Novacastrian » Sat Mar 08, 2008 11:00 pm

Ant, look at <a href="http://www.spudfiles.com/forums/the-hammer-shotgun-t13253.html">this thread</a>
Lovely gun Gippeto, nice work :)
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Unread postAuthor: jon_89 » Sat Mar 08, 2008 11:14 pm

Nice gun. What is your piston made from?
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