Cannon

Who doesn't like cannons?

Cannon History

When I was a wee lad I built a Spud Gun with my dad following the 2012 Make Magazine article: Night Lighter. Freshman year of college I put an air pressure powered cannon in a hat for an assignment to "create a toy" under the premise that it was a (albeit overpowered) confetti cannon.

It was cool, but having to refill the tank via pump every time tested my patience and made the destructive nature of the device less fun. Due to the professor’s enthusiasm about the final product I ended up giving the device to her. In turn, she gave me a C. How lovely!

My senior year of college I had far too much time on my hands and decided to build an automated cannon on a gimbal with the eventual goal of mounting a camera to it and having automated face tracking and blasting. The camera/tracking step never ended up happening but here’s an overview of the cannon itself.

Cannon V2

The basis of an air cannon is quite simple. Fill a pressure chamber with air (30-300 psi) then release the pressure through a valve to push your projectile out of the barrel. The genius innovation I made on this iteration was to include the compressor in the cannon itself to allow automated tank refills.

The internals:

• Air compressor
• Solenoid
• Pressure sensor
• Relay board for Compressor + Solenoid
• 2x Nema17 Stepper Motors
• 2x Stepper Driver boards (A4988) and corresponding passive components
• Arduino Nano for control
• RaspberryPi for vision

Internals

I would love to be able to show my CAD models but they're all in Solidworks and Dassault no longer considers me a student and therefore wants $4k upfront and $1.3k/year after that. Enrolling in community college and paying the student rate would be cheaper. This is a good time for a Fusion 360 plug. Great CAD software. Solidworks sucks. Dassault if you're reading, I'm willing to remove this holistically scathing review of your product in exchange for free Solidworks.

Rant aside-here are the demos I assume you've been waiting for.

Control Demo

Targeting Demo

Blasting Demo

Practicality Demo

Learnings

Solenoids may not be the tool for the job. While this solenoid matches the rating of my compressor to 150psi, projectile velocity seems to decrease after about 70psi. This is likely due to a slower opening of the valve at high pressures resulting in a delayed release of air volume and therefore a relative decreased pressure behind the projectile at time of launch. Future iterations will require a rethink.