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Barrel Alignment and Piston Travel Distance

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: Blitz » Thu Jul 18, 2013 3:00 pm

Fair enough. :)

I'm ball parking figures for GGDT/HGDT, then I fine tune what I can. I just sometimes struggle figuring out things like flow coefficiency of whatever valve I use. But enough about me!
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Unread postAuthor: Technician1002 » Thu Jul 18, 2013 5:05 pm

I've been meaning to ask about this..
Hi All, my first Pneumatic launcher is well under way (a 3" Piston cannon Very Happy )

Is the 3 inch the OD of the piston, or the size of the valve seat? If this is measured by orifice size, it is huge.

If it is a 3 inch diameter, what is the diameter of the valve seat? I ask as this affects the performance of the valve. The closer the valve seat is to 3 inch, such as 2.5 inch, then the lower the pilot pressure has to be before the valve is unbalanced to start opening. As mentioned earlier, low pressure in the pilot when the valve opens is a good thing.

If the valve seat is 1.5 inch, it will be a slow opener unless a huge fast pilot valve is used. This is because the valve will start to open even when there is considerable pressure in the pilot, and as the chamber pressure drops, this pressure unless vented very fast will shove the valve back closed. A large diaphragm with a relatively small valve seat is exactly how truck air horns are built.

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