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Unread 30-09-2006, 16:41
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Re: Optimizing Air Cannon Range

Your cannon is honking when you fire it? If so, I suspect your fancy rainbird valve isn't working as well as you think. I'm actually surprised it's even sealing particulary well, since the one I used for my ping-pong ball cannon refused to seal with air without heavy modifications.

At any rate, you probably need to make the whole air system more efficient. 10' of 1" tubing is going to restrict a lot of your air flow. Chances are that your t-shirt will be mostly down your barrel before any of the air from te storage tank gets to the valve. Secondly, your valve needs to open rapidly and completely. Right now, it sounds like it's mostly opening, and the are rusing past the membrane inside is making it vibrate and disrupt the airflow. You can either switch to a butterfly valve actuated with a pneumatic piston, or modify your solenoid valve. I sealed up the hole in the membrane, and pressurized the top chamber seperately. I also put a spring inside the valve to push the membrane up and out of the way more completely.

That's all assuming you want to improve your design. Your other option is to simply throw more PSI at everything, and hope nothing explodes and injures you. Seriously. Your tubing and valve there are only meant to work with water, which is fairly incompressible. Filling up that 1" tube with compressed air is an accident waiting to happen. Especially since it sounds like the only pressure control in your system is the 120 psi relief valve on the compressor.

At any rate, efficiency is more fun. My ping-pong cannon was about 1' long, total. The air chamber was 4" of 1.5" PVC, and the barrel was about 3" long. It still launched balls farther than the huge monstrosities other teams built with 2 foot long barrels and 2'x3" air chambers. Unfortunately, the goal was accuracy, and that's a bit hard with a cannon that shoots things 30' on 20 psi.
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