http://www.spudfiles.com/forums/files/thumbs/t_my_ideal_pistonvalve_177.jpg That design works for a coaxial valve with air entering from all sides, but falls short with air entering from only one side. You would want to modify it for single side air flow if used in a T. What if there was an input o...

thanks. I'll ask some questions, but this is likely far above my head.

I decided to ask here because who else would know better about pneumatics? I want to build a vortex cannon; it fires nothing except a concentrated vortex of air. They exist as cheap novelty toys, like thus: http://upload.wikimedia.org/wikipedia/commons/thumb/f/f5/Airzooka.jpg/220px-Airzooka.jpg but ...