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3" pressure-rated PVC

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: dimwell » Sun Sep 06, 2009 1:56 pm

c11man wrote:lol you bought the plans? how much did you pay for that?


As I said before: A friend of mine bought the plans, then commissioned me to build the thing. I had to improvise, so I'm now looking for ways to improve the design.

FWIW, here's the current build:
Image

its a OK desighn i guess, to make it better move the sprinker to right behind the barrel, get a way bigger chamber ( same volume as barrel or slightly bigger, and dont guess, do the math).


My current plans are to move the valve to be behind the barrel. I'll probably shorten the barrel, as well. I'm also going to cut the threaded nipples to reduce the space between components and knock out some dead space.

in my opinion plans for spudguns are genarly worthless


Whether it's a formal plan with step-by-step instructions, or a loose design in your head, plans are rarely worthless. This being my first gun, I learned a lot just from looking at the plans.
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Unread postAuthor: Technician1002 » Sun Sep 06, 2009 8:34 pm

c11man wrote:
and with a sprinkler vavle i dont think a .3:1 ratio would be very good. a sprinkler valve just isnt crazy efficent like the QDV


I've seen many flow restricted cannons still blowing lots of hiss through a valve long after the projectile has left. The high efficiency valves actually do better with a larger chamber than a sprinkler valve simply because they can deliver the volume of air in less time during the launch.

A restrictive flow valve requires longer time to vent the chamber. The more restrictive the valve is, the shorter the barrel should be, because the maximum velocity is reached in less distance.

Extra chamber provides little to no extra speed. With a long barrel and restrictive valve, extra chamber just ensures the projectile doesn't slow down in the barrel. A shorter barrel is more efficient.
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