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Dead Space

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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Dead Space

Unread postAuthor: Marco321 » Fri Jun 08, 2007 5:52 am

Hey
I have done some searching i haven't found any solid decent facts or information about what exaclty dead space is. So can anyone help me by telling me what exactly it is, how it effects the performance and by how much. All i really know is that its cause my bends in the chamber.
Thanks
Marco
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Unread postAuthor: MrCrowley » Fri Jun 08, 2007 5:55 am

Dead space is the volume between your valve and projectile.
The bigger the space is the more the pressure in your chamber has to fill up to reach the projectile therefore wasting pressure and power in your shot.
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Unread postAuthor: Marco321 » Fri Jun 08, 2007 5:59 am

Oh ok, but i was reading somewhere it has to do with bends and stuff, or is that bends between the projectile and the valve?
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Unread postAuthor: MrCrowley » Fri Jun 08, 2007 6:06 am

That could be referring to how bends in your dead space or chamber area can slow down the air rushing through to your projectile but its usually nothing to worry about it performance wise.
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Unread postAuthor: Marco321 » Fri Jun 08, 2007 6:09 am

OK cool, i have about 15cm between the valve and the projectile, is that a problem. its so big because instead of buying a new barrel to fit my new valve i used a female thread then another male thread to go into my valve.
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Unread postAuthor: VH_man » Fri Jun 08, 2007 6:50 am

it should be fine....

its not like its going to kill you. might dcrease FPS like 20 FPS.....

do a GGDT simulation of it, theres a variable for dead space. it usually decreases 20 FPS per 6 inches of 2 inch pipe.
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Unread postAuthor: Marco321 » Fri Jun 08, 2007 7:04 am

Ok i have done one already, im not sure if i did the valve correctly, i did it based on what i saw on the internet and stuff. It estimates 150m/s
Here it is, any comments/corrections will be greatly appreciated.

Image

EDIT:
Forgot to mention modded sprinkler valve
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Unread postAuthor: spudthug » Fri Jun 08, 2007 9:14 am

no u did a chamber sealing valve.. put it on generic.
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Unread postAuthor: Freefall » Fri Jun 08, 2007 11:45 am

no u did a chamber sealing valve.. put it on generic.

Generic would be for ball valves or other non-pilot type valves.

Marco, what kind of valve are you using? Is your gun described in more detail in another thread?
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Unread postAuthor: Marco321 » Fri Jun 08, 2007 6:48 pm

Hey
Sorry for the lack of details about my gun, i forgot to link it to my guns thread. Here it is. The only thing i changed on the gun is a shorter hose between the valve and the blowgun

http://www.spudfiles.com/forums/viewtopic.php?p=91073#91073
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Unread postAuthor: boilingleadbath » Sun Jun 10, 2007 10:59 am

I think it's safe to presume that your 25mm valves are the same as our 1" valves, or at least very similar.

In which case, D Hall's <a href="http://www.thehalls-in-bfe.com/GGDT/library/valve_orbit1.html">website</a> has the valve information you need.
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Unread postAuthor: MrCrowley » Sun Jun 10, 2007 11:32 pm

boilingleadbath wrote:I think it's safe to presume that your 25mm valves are the same as our 1" valves, or at least very similar.

In which case, D Hall's <a href="http://www.thehalls-in-bfe.com/GGDT/library/valve_orbit1.html">website</a> has the valve information you need.


Yeah they're the same. Well work exactly the same and 25mm BSP = 1"NPT so it should have the same or very similar CV/opening time/flow etc.
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Unread postAuthor: Marco321 » Mon Jun 11, 2007 4:33 am

OK, thanks guys, you have helped heaps, and you answered a question i had about my valve and the ones on the GGDT website without me even asking lol.
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