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GGDT chambersize projections

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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GGDT chambersize projections

Unread postAuthor: cheeseboy » Sat Dec 20, 2008 6:32 am

if you have read my topic on the high pressure solenoid valve, I am making a new pneumatic, I already have my barrel (0.75m of 10mm steel) and various other parts. I put the variables on ggdt to try and work out the optimal chamber size while retaining practicality, at 300psig (same as psi?) when I put in the chamber size from 1" diameter 1" length to 1"diameter 6" length it changes the fps from 761fps to 805fps making a difference of 44fps is it normal for the size of the chamber to make this little difference when the size is increased by 600% :?:
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Unread postAuthor: CasinoVanart » Sat Dec 20, 2008 6:37 am

Yup, unless you make the barrel somewhat fudgingly huge to accompany the abnormaly sized chamber :wink:
Increase the pressure, not the chamber size!
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Unread postAuthor: POLAND_SPUD » Sat Dec 20, 2008 6:47 am

yes it is normal to get little increase in power above a certain point...

at higher pressures a ratio of chamber to barrel volume should be smaller when compared to low pressures... (I assume that this is going to be your first high pressure gun??)

personally I use ratios bigger than 0.7 (at 250 - 500 psi)
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Unread postAuthor: cheeseboy » Sat Dec 20, 2008 8:17 am

awesome, this means I can make a Very aesthetically pleasing gun while still retaining power :D yes this is my first high pressure gun.
and its gonna rock :!: I am trying to design it after a dragunov svd
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