Spudtech Forum

Originaly posted by corncob909,
will this work- (i guess the chamber size isn't gonna matter much if the piston valve doesn't even work...) please go to my site posted below then go to the new development page, it has my wonderful drawing of the plans for a supah type valve... i would just like to know whether this will work or not before i buy some of the parts from mcmaster. Also, would using a sanitary tee for the piston housing (one with the curved top port thingy) affect performance?

ok well here's the site - http://corncob909.tripod.com/

thanks in advance for your input

Originaly posted by mta,
I looked at your valve. If it works it will really make for a powerful gun. As for chamber size and what not.. how many cubic inches of chamber are you prepared to deal with? What size barrel? 3" or something smaller? How long a barrel are you willing to deal with? There's a great program called GGDT (Gas Gun Design Tool) that lets you try various barrel and chamber configurations and see the effect on muzzle velocity.

http://www1.iwvisp.com/thehalls/paintball/ggdt.html

Originaly posted by corncob909,
thanks, im glad to hear that it should work, but as for GGDT, i have the program but im not sure what i should enter in for the valve data (type, cv, open/close time, and dwell time), anyone able to help me out here? (incase this affects the valve data- im using a 1 inch pneumatically controlled sprinkler valve to release the pressure behind the piston.)

thanks for you help

Originaly posted by mta,
Assuming your 3" piston works properly, the valve data for GGDT sould be something like.. generic valve. Cv = 100 open/close time = 25 ms dwell time = 1000 ms

The above figures are just an educated guess. If your valve works well, the numbers should be in the ballpark.

Originaly posted by corncob909,
with a tennis ball! is this correct or am i just dreaming... :-)

Originaly posted by corncob909,
with a tennis ball! is this correct or am i just dreaming... :-) i put a 400.55 cubic inch chamber and a 2.5 inch barrel that is 110 inches

Originaly posted by andeh,
The tennis ball coaxial I was going to build would have fired 800+ FPS at 100 PSI and 10 foot barrel.

Originaly posted by mta,
With a ten foot barrel and 350 cu. in chamber and a good 3" piston valve you'd be pushing 800 fps with a 58 gram tennis ball at 100 psi of air.

Of course if your valve sucks, you won't do nearly as well.

My ten foot gun (2" barrel) pushes an 83 gram projectile at 640+ fps, and the valve Cv is only 43. Your valve should have a Cv of around 100.