We had tons of ideas, but the one that seemed most feasible, and had the least probability of causing mortal injury, was this. We created a red bull launching mortar system. The cans are launched and a parachute deploys to bring them down to the eager people below safely. I was the one in charge of construction, so the rest of the team acted as consultants for this round. I was also able to recruit a few people from here at Squidfoo for help.
Our first task was creating the cannon itself. It is a fairly simple pneumatic cannon. There’s an empty propane tank for a compression chamber, then a solenoid valve going to the barrel. We chose to lay the propane tank on its side and set it on some wheels to allow for a perfect aiming mechanism. You can rotate the barrel up and down very easily. [Andrew Mitzel] put in several hours of hard work getting that rotating mechanism to work just right.
After that, [Tony Sherwood] and I came up with a design that would function as a sabot as well as a removable harness for the cans. The barrel is 3″ wide, so the cans needed some help making a seal. [Tony] happened to have a makerbot replicator with him, so we printed out perfectly sized bits, including our hackaday logo for the bottom. I added an LED in the hackaday logo just in case you were to fire these after dark. You can find the files for our logo on thingiverse. You can find the can top/bottom on [Tony’s] account (updated link coming as soon as he uploads them).
The only rule to this section of the contest was to utilize the bullduino they sent out. We used it as our safety system. You have to push specific pads at the same time to arm the device. Once armed, you can fire only if you depress both the thumb button and the trigger. After about 15 seconds, they bullduino automatically disarms itself.
As you can see in the video, this sucker really shoots the cans well. The parachutes deploy and the wind can carry the cans pretty far. Of course, if the wind is blowing back at the cannon, they can drift all the way back too. We ended up deciding to fire some rounds without parachutes just for fun. It easily covered the distance of a football field.
We’re working on something completely un-safe with it, stay tuned.
Interestingly, the only problem I’ve run into in this entire process is the fact that the public domain music I chose has legal issues on youtube. Apparently WMG owns every performance of “Ride of the Valkyries” that is out there. Jerks.
Here’s a Vimeo link just incase the music ends up being an issue.