In this installment of Intern’s Corner, our brand spankin’ new Make: Labs intern, Daniel Spangler, shares the details (and gives of a video tour) of his badass internal combustion cannon with interchangeable barrels. We haven’t broken it to him yet, but to keep us happy, he’s going to have to help each of us make one. Welcome aboard, Dan! -Gareth
My interest in cannons started back in high school, when an attempt to make a hydrogen converter went horribly wrong, shattering the florescent bulb in my garage and singeing my eyebrows off. After changing my pants, I looked at what was left and thought, “Hmmmmmm…”
The rest is history. I soon cobbled together a suitable cannon-ish device that could propel small 3/4-inch dowels through about five layers of cardboard, and that was fun, but I had to do more — it always had to be bigger, louder, more reliable, and more powerful. So I kept building. I would build some for me, some for friends, and they kept growing in size and complexity… ’til I achieved what you see here.
This is my advance combustion cannon. It utilizes two BBQ piezoelectric igniters to touch off the propane/air mixture inside the 3-foot-long by 4-inch-diameter combustion chamber. A special metering system using an air regulator, two ball valves, and a specific length of steel pipe ensures that the correct amount of fuel is injected into the combustion chamber. You operate it by tuning the regulator to the specified 90 psi, opening the first ball valve to allow the steel pipe to be pressurized, then after closing the first valve, you open the second one to discharge the gas in the steel pipe into the combustion chamber. From there, a computer fan mounted inside the combustion chamber mixes the air and fuel to create clean, thorough combustion. I have two interchangeable barrels for this cannon. One is a sleeved 3-inch barrel that’s perfect for shooting soda cans, the other is a 6-foot-long 2 1/2-inch bore barrel that launches tennis balls far enough so you can’t see where they land. This cannon is really fun. It fires almost every time, and shooting empty cans is a safe and entertaining way to show it off.
Now you may be wondering, “What’s your next step?” Well, I have been working on plans for a multi-barrel, belt-fed, fully automatic gatling cannon that utilizes a special spud-gun cannon shell that I’ve designed. I haven’t really gone anywhere with it since i didn’t have the funds for the tools, but now that I’ve joined the ranks of the Make: Labs Engineering Interns, anything is possible. We shall see…
[Photo by Gregory Hayes]