From the Braver Institute
“We did make an oxy/acetylenepowered potato cannon once at my old truck repair garage. It caved in the door of a pickup truck,” was my reply. I ignored the jab at my age.
The first potato cannon I had ever seen was made from PVC pipe and was fueled by hairspray. A potato was jammed in the end of it and ignition was provided by a flint and wheel lighter from a Coleman lantern. It was a vegetable bazooka. It would launch a potato a hundred feet or so.
Not being one to leave well enough alone, I decided that the potato cannon could be improved. During downtime at the shop I enlisted the help of the other guys and we set about building a better cannon.
The hairspray used to propel the potato was volatile enough but over time it would gum things up due to its adhesive qualities. We needed to use a fuel that would burn clean and leave no residue.
Since this was a heavy truck repair garage we had a wide variety of tools and equipment at our disposal. We could have used starting fluid, but it is too expensive and possibly too volatile. Instead we opted for acetylene—one of the gases used with welding torches.
Anything called a cannon is usually (by its very nature) a potentially dangerous thing, so safety was mostly one of our highest concerns. Of course we couldn’t use such a highly flammable gas with PVC pipe so we opted for steel. We also didn’t want to be anywhere near the thing when it was ignited. There was no way you were going to get any of us to hold it, so we had to devise another ignition system.
We welded the pipe that would be the barrel of the cannon to a large, heavy steel plate. We welded a nut with the same threading as a spark plug over what would be considered the touch hole (the place where a fuse would go). With a spark plug ignition system we could control our potato launch from a distance. We used fifty feet or so of wire and connected it to a battery, a switch, and an ignition coil (since a battery alone is not enough to get a spark plug to do its thing).
We released what we thought would be a suitable amount of acetylene into the pipe and then stuffed a potato inside. We aimed the cannon toward the woods behind the shop and ran our ignition wire inside, where we could observe in relative safety. When contact was made with the battery, the cannon made a noise similar to the handheld one and with similar results. We hadn’t expected this.
We decided that we needed to introduce oxygen into the mix. Pure oxygen mixed with a fuel like acetylene is extremely volatile.
We set the cannon up as before and returned to the garage. Upon ignition there was a cannon-worthy BOOM! The potato shot toward the trees with such speed that we could not follow it with our eyes. It also had so much force that the potato caved in the door of a junk pickup truck that was sitting at the edge of the woods and smashed itself into indiscernible bits.
An impressive show indeed.
Since this cannon obviously had enough power to make it to the trees, we needed to have a better idea of just how far it would throw a potato. Firing it horizontally over the ground was out of the question since the tree line was the greatest distance over open ground that we had.
Our only option was straight up.
We placed the cannon in the middle of our parking lot. Being a heavy truck repair garage the parking lot was really big, so we had a lot of area for the inevitable returning to earth of our launched potato.
This time when we touched the cannon off it bounced and danced around on the ground since it couldn’t simply recoil backward as it did when it was set up horizontally. Once again we were not able to follow the potato with our eyes, we had to take it on faith that it was well on its way toward outer space. I’m joking about that of course, but we were starting to think that maybe it was at least entering the stratosphere.
We waited for what seemed to be an eternity for it to come down, and we were almost ready to resign ourselves to the idea that it may have drifted off into the woods, or it may have blown apart completely. After nearly thirty seconds (it’s a lot longer than it seems) there was dull thud across the parking lot.
Upon investigation we found a wet spot and the skin of a potato.
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