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 Post Posted: Sun Jul 13, 2003 10:00 pm 
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Originaly posted by beartracker89,
NT


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 Post subject: here's how
 Post Posted: Sun Jul 13, 2003 10:00 pm 
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Originaly posted by Bartman007,
First off, there is coaxial gun simply means that the barrel extends through the length of the air/combustion chamber, thereby shortening the length of the gun. All diaphragm based pneumatics that I know of are coaxial based guns. X-Inventions has a great page here explaining how both a piston and diaphragm valve work. Most (home-made) piston based guns are coaxial based too, while the Supah-Valve is an exception, it isn't homemade =)

Peace,
-Bartman007


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 Post subject: Valves
 Post Posted: Mon Jul 14, 2003 5:00 am 
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Originaly posted by mta,
Piston and diaphragm valves work on the same principle. The difference is in the thickness. A diaphragm is basically a thin disk, while a piston is more like a cylinder.


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 Post subject: additional info
 Post Posted: Mon Jul 14, 2003 8:00 pm 
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Originaly posted by MarvinTheRobot,
the diaphram is the most efficent because you are moving a light object with large surface area, which allows faster fireing, but the accual diaphram will need to be custem by you, because no one sells them (they are hard to make and maintain)



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 Post subject: I Beg to Differ.
 Post Posted: Mon Jul 14, 2003 8:00 pm 
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Originaly posted by Bartman007,
The piston design is far more efficient. With the piston in it's open position you have larger openning for the air to rush through. I'm sure that if the diaphragm design was more efficient then Joel would be selling diaphragm based Supah Valves rather than piston based Supah Vavles.
All of the Pneumatic veterans please chime in because I am still a pneumatics rookie.

Peace,
-Bartman007


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 Post Posted: Mon Jul 14, 2003 9:00 pm 
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Originaly posted by andeh,
the way his valve is, only a piston COULD work... and I have no idea which is better, but I'm trying to make a floating diaphragm as we speak...


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 Post subject: Ahem...Piston..
 Post Posted: Mon Jul 14, 2003 10:00 pm 
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Originaly posted by GisMo,
A piston does, indeed allow MUCH greater airflow, although it is a tad tougher to design a piston valve...If you scoll down..i posted pics to the PISTON vavle I made.


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 Post Posted: Mon Jul 14, 2003 11:00 pm 
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Originaly posted by andeh,


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 Post Posted: Tue Jul 15, 2003 8:00 am 
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Originaly posted by mta,
There is no reason that a good diaphragm valve could not equal or surpass the best piston valve. They operate on the same principle. A diaphragm has the advantage of being lighter, so it can open faster than a heavier piston. Diaphragms are also a lot simpler, cheaper, and easier to make. Mine cost about a buck a piece.

One factor that is over looked when comparing these valves is the orientation (coaxial vs. right angle) and its effect on piston/diaphragm travel distance. The shorter the distance, the faster it opens. Let's compare a 2" right angle piston valve to a 2" coaxial diaphragm valve.

In the piston valve, the air must flow through a 2" pipe on the side of the cylinder. The piston must move a distance equal to the ID of that pipe before the valve is fully open. 2" sch40 has an ID of 2.049". 2.049" is the minimum distance the piston must travel before the valve is fully open.

In a 2" coaxial diaphragm valve, all the air must flow out the 2" barrel. The valve can be considered fully open when the area the air is pinched through is equal to the area of the 2" pipe. 2" sch40 ID = 2.049", area = 3.3 sq. in. On my valve, I put a modified coupler over the breech end of the barrel to act as a sort of valve seat. The ID of the coupler is 4.5", and the circumference is 14.14". The diaphragm needs to move only .233" before it's fully open.

The right angle piston must move 2.049" to open, the coaxial diaphragm needs to move only .223". The difference in the amount of air that must be dumped behind the diaphragm/piston corresponds to the difference in travel distance. The piston travels nine times further than the diaphragm, and has nine times as much air behind it needing to be dumped. Bottom line.. coaxial valves open faster.

Does my 2" diaphragm out perform a 2" supah valve? Probably not. It's a very crude design, while the supah is a highly refined design. But until somebody posts actual numbers on a Supah based gun, we'll never know. My 2" valve has a flow coefficient (Cv) of 43, and an opening time of < 10ms. I wish I had a supah based gun for a day so I could determine the valve's Cv.


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 Post Posted: Tue Jul 15, 2003 3:00 pm 
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Originaly posted by andeh,
their own stuff LOL.


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