Air Cannon Design Help

[Spenyescer]

Hello everyone!

For my university senior design project, my team has been tasked with developing a ballistic launched image recording system. I need some design suggestions on constructing a pneumatic launcher system that can launch a 1.5 lb projectile to a minimum of 80 ft in height and 300-700 ft in range with 300-1000 ft being the optimal range. The projectile itself is going to be a 2 to 4 inch diameter mortar shell looking projectile that is going to have video camera and GPS/sensor module internals. I believe that my team has settled on using a pneumatic launcher system to fire our projectile utilizing either a sprinkler solenoid or QEV trigger system. Additionally, we need to be able to change our launch angle as necessary to meet any added launch requirements, so my team envisions utilizing some sort of pressure rated flexible hose so that the muzzle can rotate anywhere from 0 to 90 degrees, or the entire system will be statically mounted on a pivot that can be aligned from 0 to 90 degrees. I guess the primary information that we need help with is how large should we make our air reservoir tank that will store the air to launch the projectile so that enough force is delivered to meet our projectile flight requirements? Also, how long should our muzzle be since we already know its diameter will be in the 2 to 4 inch range. I know that this may be a lot but general design tips or help would go a long way for us and would be greatly appreciated since none of us have any pneumatic gun building experience.

Cheers!
Spencer

[Moonbogg]

What's your budget?

[Spenyescer]

Great question! I can't believe that I forgot that part, but our total project budget is $3k. We have set some initial budget plans: $1,200 for the projectile components, $1,200 for the launcher system, and $600 reserve for safety equipment, buying replacement parts, etc.. So, I would say that below $1,200 is what we have planned for, but maybe the maximum we would be comfortable spending is $1,500.

[Moonbogg]

Download GGDT (gas gun design tool) and use it to model the cannon's performance. Look around in the pneumatic cannon section for design ideas. I'd imagine a piston cannon would be a good choice. Air is thick and soupy, so a large enough piston is needed to avoid choking the thing off, maybe around 2 1/2"? I only have experience with combustions, but have a look around at the many examples and use GGDT. You may be able to avoid using PVC with a budget like that. PVC turns to shrapnel when it fails even at lower pressures like the pressures you will likely be using.

[Solar]

Absolutely avoid PVC for this project. Moonbog is also correct regarding the piston size. (and use of a piston valve). Sprinkler valves are usually only rated up to 150psi or 200psi for brass versions. While you can certainly launch heavy rounds at 150psi you need to move a lot of air in a short amount of time so you will want a piston as close to your barrel bore size as possible. Check out the Eclipse net launcher in the cannon showcase. That system can launch an 8lb. round at 150psi and drag a net along for the ride. We haven't tested range with an aerodynamic round yet but it utilizes a very large piston valve that uses air pressure to open fast versus bleeding air to open.