pneumatics or motors?

[JamesCH95]

Originally Posted by DavisDad

Thanks James for the heads-up. Compressed air limits are:

• Max supply pressure = 60 psig
• Solenoid Cv = 0.35
• Compressor capacity = 1.05 SCFM (says CFM in the rules ???)

My pressure required at the cannon will be less than 10 PSI = 50 PSIG dP. If I'm doing the air Cv calc right, I get between a bit over 10 SCFM.

I'm also looking at high pressure blower feasibility (~ 8 PSIG). Any thoughts on that legality?

My math says that filling that volume chamber (8in diameter, 8in length, right cylinder) at 10CFM will result in an exit velocity of less than 0.5ft/s. No doubt this equation is simplistic, but it shows that the idea is two orders of magnitude off of what I consider a good exit velocity (50ft/s is what we're 'shooting' for) and I would abandon the idea as unfeasible, pneumatic component legality aside.

Hope this helps guide your design decision.

Using a fan or blower may work, and I don't *think* it would be illegal (I AM NOT THE GDC), but I don't think that it will efficiently transfer kinetic energy to the ball. I spent most of my junior year of college building and running turbo-machinery experiments, so this is a 'semi-expert' opinion, take it for what its worth. A decent, maximized, blower efficiency is usually around 80%, and I bet you won't be operating near this over a shot cycle given that the ball is accelerating away and therefore your flow rate is changing rapidly. I don't think the work of sizing motors, blower, housings, and a lunch tube to work optimally will be worth all of the inevitable efficiency sacrifices you'll be making.