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How far your piston should travel

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: SpudBlaster15 » Sun Jan 20, 2008 3:06 pm

Ah, ok, that makes sense. I had a slightly different vision of your configuration.

Because you have airflow entering from 2 opposing rectangular ports, it would be logical to model your setup as 2(l*w) as opposed to (l*w). So;

2l*2w = pi*r<sup>2</sup>
l = ((pi*r<sup>2</sup>)/2w)/2

Solving for your launcher (and making some assumptions), we get;

l = ((pi*(1.029/2)<sup>2</sup>)/2(2.067))/2
l = ~0.43"

So your piston should travel backwards ~0.43" for maximum flow.
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Unread postAuthor: jrrdw » Sun Jan 20, 2008 4:21 pm

So all most half an inch. There goes the d4 rule. My barrel bore being 1". Thanks for writing it all out, but I must tell you my math isn't that good. I mite as well be trying to translate the Chines language. I can't speak Chines. I was looking for a answer like this, common sense tells me 1/4" of the barrel diameter just isn't enough!
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