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| Gippeto |
 Posted: 03/08/2008 14:16 PM Post subject: Piston in copper and brass updated 05/03/08 Damage pics |
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Colonel
Joined: 19 Jan 2008
Posts: 705
1746.17 Spud Bux
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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=7FBsQZ3sv-k&feature=email
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| Just because its a cool shot. |
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| 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. |
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| Beer can filled with water and shot with 1/2 ounce fishing weight/hot glue ammo @ 400psi. 5 yard range. |
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| The exit side. 3/4" spruce plywood. Shot at a range of 5 yards. 1/2 ounce fishing weight/hot glue ammo @ 400psi |
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| Finished the hammer piston. I will be testing and comparing the two for performance soon. |
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| A commercially available check valve with a few mods. |
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| New fill setup. Seals when finger tight. (no wrenches) |
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| New sights, ready to mount. |
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Last edited by Gippeto on 06/21/2008 0:00 AM; edited 8 times in total |
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| jackssmirkingrevenge |
| Posted: 03/08/2008 14:29 PM Post subject: |
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space monkey
Joined: 15 Mar 2007
Posts: 7050
11306.91 Spud Bux
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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 |
| Posted: 03/08/2008 14:53 PM Post subject: |
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Blizzard of Ozz
Joined: 23 Jun 2006
Posts: 6187
3319.40 Spud Bux
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| Very nice, looks great. Let us know how the performance is
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| Antonio |
| Posted: 03/08/2008 16:24 PM Post subject: |
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Captain of Industry
Joined: 13 Aug 2006
Posts: 495
24.52 Spud Bux
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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?
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 |
| Posted: 03/08/2008 16:32 PM Post subject: |
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1st Lieutenant
Joined: 25 Oct 2007
Posts: 289
276.38 Spud Bux
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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 |
| Posted: 03/08/2008 16:37 PM Post subject: |
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Captain of Industry
Joined: 13 Aug 2006
Posts: 495
24.52 Spud Bux
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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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| DYI |
| Posted: 03/08/2008 16:44 PM Post subject: |
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Rear Brigadier
Joined: 07 Jul 2007
Posts: 2308
1164.60 Spud Bux
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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 |
| Posted: 03/08/2008 16:47 PM Post subject: |
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Major
Joined: 21 Jan 2007
Posts: 358
997.37 Spud Bux
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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.
Talk about running before you walk. 
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| Gippeto |
| Posted: 03/08/2008 17:05 PM Post subject: |
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Colonel
Joined: 19 Jan 2008
Posts: 705
1746.17 Spud Bux
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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.
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| bluerussetboy |
| Posted: 03/08/2008 18:40 PM Post subject: |
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1st Lieutenant
Joined: 02 Nov 2007
Posts: 269
554.77 Spud Bux
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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 |
| Posted: 03/08/2008 20:26 PM Post subject: |
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Captain of Industry
Joined: 13 Aug 2006
Posts: 495
24.52 Spud Bux
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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 |
| Posted: 03/08/2008 20:35 PM Post subject: |
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Blizzard of Ozz
Joined: 23 Jun 2006
Posts: 6187
3319.40 Spud Bux
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| Sticky_Tape |
| Posted: 03/08/2008 21:27 PM Post subject: |
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Brigadier General
Joined: 31 Jan 2008
Posts: 929
1165.85 Spud Bux
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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 |
| Posted: 03/08/2008 22:00 PM Post subject: |
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Bloody Aussie
Joined: 11 Aug 2007
Posts: 1622
116.11 Spud Bux
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| jon_89 |
| Posted: 03/08/2008 22:14 PM Post subject: |
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Lieutenant Colonel
Joined: 11 Apr 2007
Posts: 477
642.41 Spud Bux
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| Nice gun. What is your piston made from?
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