which type of valve?

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Postby watermelon » Thu Jul 31, 2003 3:28 pm

i was just wondering which sort of piston valve is best and why.


a free flaoting piston like the one at this site:
http://www.geocities.com/spudguns_uk/50 ... on_gun.htm

or a supah type valve like the one here:
http://www.spudtech.com/forum/showpost. ... postid=219

if i made the barrel and chamber exactly the same size which would perform better?
watermelon
 
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Postby mta » Thu Jul 31, 2003 3:48 pm

There is no clear answer as to which is better. One is coaxial and the other is a right angle valve. The coaxial can open faster because the piston has a shorter travel distance and less air to dump. A typical right angle piston might have to travel 4 or 5 times farther than a coaxial piston to allow the same airflow.

In a coaxial, however, the air must make a 180 degree turn, as opposed to the 90 degree turn in the other design. So supah style valves probably have greater airflow.

Any piston valve is difficult to make. If I were going to use one I'd probably buy a Supah. At least I'd be assured the thing would work.

The valves I use are like the coaxial piston in your first link, but instead of a piston they have a thin diaphragm. It's easy to make (well.. with a little practice it's easy... the first one can be a pain), cheap, and performance is excellent (Cv = 21 for 1.5" , Cv = 43 for 2"). Here's a link:

http://mywebpages.comcast.net/glenshind ... ternal.gif

The guy at spudzooka.net might even have a few 1.5" diaphragms left to sell.. buying one saves you the aggravation of making one.

Whatever you go with, use something better than a ball valve or blowgun to dump the air behind the piston/diaphragm.
mta
 
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Postby watermelon » Thu Jul 31, 2003 4:01 pm

i have already made a free floating piston. it was made out of a shampoo bottle filled with hotglue and wrpped in tape. it worked great. i dont see why everyone seems to make fancy pistons with O-rings.

air does have to turn 180 in the supah valve.

the only advantage i can see of the supah valve is that it allows you to have a much bigger chamber due to not have the barrel running through it. but id image its actuates slower and its harder to make.
watermelon
 
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Postby corncob909 » Thu Jul 31, 2003 11:26 pm

it is definitely harder to construct a supah-type-piston valve, yet it is believed to have a higher cv, correct me if im wrong, but i agree they are pretty equal and they both have there advantages and disagvantages, but for its ease of construction i would say thats one big advantage for the "free floating" piston valve
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