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Re: Nerf Pocket Vortex cannon: Questions from a new builder
Posted: Thu Jul 10, 2008 11:54 pm
by STHORNE
Thom wrote:I'm looking to build a cannon to fire Nerf Pocket Vortex footballs. The targets will be people, so obviously it has to be reasonably weak.
You might want to re-phrase that lol.
sounds like a neat project though
Posted: Fri Jul 11, 2008 7:37 am
by socoj2
Use Chamber Seal.
And a really light piston
Posted: Fri Jul 11, 2008 8:25 am
by Thom
Thank you, socoj2!
By "really light", I assume you mean the weight of the poppet? I guess I'll fiddle around with it.
Posted: Fri Jul 11, 2008 8:45 am
by socoj2
yeah GGDT ask you for a Piston weight. since the QEV only has a diaphragm and weight is negligible. use something light.
Posted: Fri Jul 11, 2008 12:57 pm
by psycix
I believe there were some standard values for things like QEV's and sprinklers. Either by giving the right values as piston valves or as entering it simply as a "generic valve"
Posted: Fri Jul 11, 2008 10:06 pm
by Thom
Hmm. At 60 psi, GGDT is telling me that using a 3/4" QEV (The biggest I see on McMaster) would basically cut the power in half. Whereas a 2" barrel-seal piston valve with "default" params should get 306 ft/s, a .75" QEV with 7.84 Cv and .1g piston mass maxes out at about 180. I don't really need the extra power, but I'd much rather just downsize it and save myself some pumping. Is this drop expected? I guess I did cut the valve size in less than half. I don't have an intuitive sense of these things yet.
EDIT: Could I seal a piston valve with the bike pump if I used a very small hole in the piston?