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Clean Coaxial

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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Clean Coaxial

Unread postAuthor: noname » Fri Feb 23, 2007 1:27 pm

Well, lately everyone's been making "clean" guns; making the cannon, then leaving it unpainted, but using clear primer and cement. I decided to make my own.
It's just a basic coaxial, 1 1/4" and 1/2." The bushing in the front was cemented straight into the pipe.
We all know that diaphragms open extremely fast but have low flow, and piston open relatively slowly compared to diaphragms, but have high flow. This cannon has a piston with a diaphragm on the front, so it incorporates both the fast opening time of a diaphragm and the high flow of a piston. The diaphragm flexes back, allowing air to flow into the barrel, and then the piston is blown back, so air has tons of room to blast down the barrel.
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Attachments
Tim's new gun 036.jpg
Everything
Tim's new gun 039.jpg
A shot of the spring and the diaphragm/piston
Tim's new gun 040.jpg
Looking down the barrel through the chamber. The little barrel support is half of a clothespin.
Tim's new gun 040.jpg (32.95 KiB) Viewed 969 times
Tim's new gun 041.jpg
The whole thing.
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Unread postAuthor: joannaardway » Fri Feb 23, 2007 1:35 pm

You definately achieved the clean requirement - Kudos.

How well does your "revolutionary design" work?
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Novacastrian: How about use whatever the heck you can get your hands on?
frankrede: Well then I guess it won't matter when you decide to drink bleach because your out of kool-aid.
...I'm sorry, but that made my year.
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Unread postAuthor: Scope » Fri Feb 23, 2007 3:25 pm

Yea how does this hybrid valve work... Im building a coaxial... convince me to use it!

Its really nice dude... really really clean looking
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Unread postAuthor: LGM » Fri Feb 23, 2007 4:09 pm

I am deffinetly going to use that idea for a valve in my next cannon, but I am going to tweak it a bit.
Really nice clean gun.
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Unread postAuthor: noname » Fri Feb 23, 2007 5:57 pm

I experimented today with a regular piston and diaphragm, just to see how much of a difference it makes. I'd say the difference is about 50 fps, but I can't tell that much by sight.
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Unread postAuthor: jrrdw » Fri Feb 23, 2007 7:23 pm

Very good job! Question -- Just one barrel saport ? I'll guess at a distance, 175 yards with a spud for ammo, at 75/80 psi.
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Unread postAuthor: noname » Fri Feb 23, 2007 7:32 pm

When the cement cured, the barrel was crooked, so I stuck the clothespin in, and now it's straight.
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Unread postAuthor: Kobl » Sun Feb 25, 2007 2:51 pm

What kind of rubber did you use for the diaphragm? Also, did you use a 3/4" endcap or a short section of 1 inch pipe for the piston?phragm body?

-Butt
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Unread postAuthor: noname » Sun Feb 25, 2007 3:41 pm

The piston/diaphragm is a short piece of 1" SDR 21 with a 1/2" end cap JB Welded in, with the rubber JB WElded to the open end of the 1/2" cap. The rubber is just 1/16" red sheet rubber, you can get sheet rubber at almost any hardware store, check the flexibility first. The best kind of diaphragms are flexible but somewhat stiff, so they don't act like a rubber burst disc.
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