Diary of a Pyro

Copyright © 1988 - 2005 John H. DuBois III

Chapter Five

In my second year of high school I started out in two of the same classes as Scott. We both had to take Experimental Science again, and we both had metalshop. However, Scott wasn't in Experimental Science for long. We had a different instructor that year, who we called “Hendy”. Hendy never gave lectures as far as I can recall; he didn't pay much attention at all to the class. He usually sat at his desk and talked to a student for the entire period. The idea was that we were supposed to be carrying out experiments on our own. Scott and I tried to think of some experiment that would be interesting and ended up planning one that at least faintly reflected our interests. It involved burning candles at various heights in a closed jar. It was actually rather boring and we didn't spend much time on it; instead we ended up demonstrating the danger inherent in the autonomy that Hendy granted to us. We were aided in this by the fortuitous site of our table; it happened to be next to a large unlocked cabinet full of chemicals.

Scott would often surreptitiously explore the cabinet while I wrote up my part of our next order to Pyro-Sonics or some such. One day he found a roll of magnesium, like the one Bill played with at St. Francis. For some reason (perhaps I dared him to, or maybe just to have fun) he took a length of magnesium from the roll, held it under the table, and ignited it. I thought it was hilarious; a brilliant glare washing the floor, smoke drifting up from the edges of the table, and Hendy not noticing a thing. Scott repeated this exercise several times before his luck ran out. Hendy uncharacteristically stopped talking to his student of the day and looked around the classroom; it's possible that he had smelled the smoke. He saw what Scott was doing, interrogated him, and sent him off to the office. That was Scott's last day in the class; it was even more boring from then on.

We did have fun in metalshop, though. After learning how to form, solder, and spot weld pieces of sheet metal, I decided to make the Mark III tennis ball cannon. Steel soda cans were beginning to disappear by that time, but a search through the grocery store showed that Hawaiian Punch still used them. Instead of taping the cans together, I soldered bands of sheet metal around the ends of each pair. Also, I made a pair of square tubular handles out of heavy guage metal. I used four cans so that I could place them correctly, and bolted them to the bands between the first and second, and the third and fourth cans, thus making it a device that one could hold and fire.

Just as important, I did away with what I now saw as the crude pyromechanical sparker. Though this was long before disposable piezoelectric lighters, my sister had found an expensive piezo lighter on a beach and had given to to me. It finally broke after a great deal of use. I removed the piezoelectric unit from it and mounted it inside the rear handle at the top, with the button projecting out like a trigger. I fed the high-voltage wire from it up through a small hole in the cannon, and relied on the metal of the handle and cans for the return electrical path.

I also made a small hole in the middle of the bottom of the rear can so that I could press the nozzle of a spray bottle full of combustible liquid against it and inject a mist of fuel. This proved to be a much more effective method of charging the cannon than squirting a stream of fluid in the open end. Finally, I wrapped the barrel with foam padding to insulate it. Like engines, tennis ball cannons work much better after they have warmed up (in the case of a TBC, from having been fired a few times); it helps vaporize the fuel, but they cool off quickly. Of course I realized that the heat might melt the insulation and eventually it did, so I removed it.

The Mark III worked beautifully. After seeing it in action Scott made an identical device. We found that acetone and denatured alcohol worked best as fuel. I had tried them with the old cannons, but they are more powerful solvents than lighter fluid and had a tendency to dissolve the adhesive on the tape that bound the cans together. The only problem we ever had was that when the cannons were cold the piezo sparker often was not strong enough to ignite the insufficiently vaporized fuel, so we brought matches with us to start them off. The handheld nature of this model made it quite versatile. Naturally we had battles with them, and also had fun shooting at frisbees and similar things in flight. They were quite durable and lasted a long time despite the abuse we gave them.

While still in metalshop, I came up with a design for a Mark IV TBC which incorporated a plunger and four valves to quickly change the air in the cannon. Scott improved this by suggesting I use a butterfly valve instead, and lending his experience with piston rings. The design had various problems, though, so we never built it.

The only time I ever injured myself with my cannon was when I idly stuffed a ball in it and put the muzzle over the handle to the door of my workshop, to see if it would be strong enough to push the door the rest of the way open. As usual I put the back of the cannon against my shoulder to fire it. Unfortunately I had incorrectly judged the power of the cannon and the inertia of the door; the recoil slammed the edge of the rear can into my shoulder hard enough to cut it. I was quite impressed by the power. After several years of service, I finally destroyed my cannon by wedging a beer bottle a bit too tightly in the end. It blew clean in two; I was left holding a handle attached one part of it in each hand. Fortunately I was not injured.

Scott's lasted longer. One day we were on one of the high school fields taking turns firing at an X-shaped boomerang-like thing that I had around, when a police officer came along and confiscated the cannon, no doubt for his own use or that of his children. He didn't tell us what law we were supposed to have violated.

Having the fuels sitting around in spray bottles induced us to play with them in other ways. We would often set a large metal can on the floor in the center of my room, spray some fuel on it, and ignite it. Then we'd sit there and spray acetone or alcohol at it to keep it lit. Since the stream of liquid wasn't moving very fast and was highly combustible, the flame travelled partway up it. Though it never got near the nozzle it would have been dangerous if it had since the spray bottle was full of fuel vapors mixed with air. If there was any slight crack in the seal with vapors leaking out of it we could have ended up in a very bad situation. We were having too much fun to worry about that, though. After a few minutes of flaming the room got very hot; we called it our “instant space heater” and didn't concern ourselves with the toxic combustion byproducts that were no doubt being created in prodigious quanties in the confined space of my room.

Since pipe parts were so expensive, I decided to see if I could produce things to fill with powder in metalshop. I rolled and cut some pieces of heavy gauge sheet metal and soldered them into odd forms. Some were shaped like long prisms, some like pyramids, and some like diamonds. I polished them to make them look good. As I was doing this, our metalshop instructor Mr. Snow came over to observe my work. He asked what I was making. He was a fairly “with it” person, so any unlikely answer would probably get me in trouble. Laurence, who had started out in metalshop with us, had already been kicked out for making a throwing star. Fortunately, the creative recesses of my mind rose to the occasion and after only a moment's hesitation I told Snowee that I was making Christmas tree ornaments. This was particularly plausible since it was approaching that time of year, and Snowee congratulated me on my ingenuity. Unfortunately the soldered joints were not very strong so the containers did not work well for my true purposes.

I think that's the only time I ever managed to trick Snowee regarding the nefarious devices I made in his class. Scott once started to make a tennis ball cannon completely out of sheet metal (using no soda cans.) He rolled a piece of metal into a tube for the barrel and soldered another piece onto the bottom. When Snowee asked what it was, Scott told him it was a vase. Snowee didn't buy that. I don't remember whether it was for that reason or due to technical difficulties that Scott never finished the cannon. I tried making a similar one but couldn't get the seam on the inside to be smooth enough to form a gastight fit against the tennis ball. I didn't have much better luck with my “testing chamber”. I spot welded together a small box from sheet metal, about ten inches (25 cm) square. My idea was to have something that I could test very small explosives in in my workshop. Actually, the true genesis of the idea was simply a lack of any other project at the time in metalshop; I didn't expect it to be particularly useful. In fact, when I was done and brought it home, just for the hell of it I decided to test it with something more powerful than it was designed for, and put a cob in it. I lit the fuse, slid the door of the chamber shut, and left the workshop. When I came back there was nothing but a mass of mangled sheet metal left. I hadn't really expected that; I found it rather humorous.

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