That year I had plenty of time to prepare for the Fourth. I bought lots of finned missiles, dumped out the piddling payloads, and packed them with flash powder. We had discovered that Bondo, normally used for filling dents in cars, worked excellently to cap the ends of cardboard tubes to make M80-like devices, and I had a bag of such things, along with a bag of rockets and bags of commercial items. I used my chest for the first time since the Fourth I had constructed it for many years before. The back of Scott's truck was loaded with three chests of fireworks as we headed out to the sand plant. Laurence and his friend printed up flyers again, advertising their “3RD ANNUAL 4TH OF JULY PARTY ON THE BEACH”.
We found that the sand plant was even more dilapidated; by now about half of it had collapsed. Some wreckage in the collapsed part was arranged into a sort of shed and the bar was set up in it. Those who had payed the gate donation were given cups to identify them. Because we had had many fireworks stolen the year before, we dug a large pit to put the chests in. On the windward side of the pit we put up a barrier made with scraps of plywood. Around the rest we put a rope barricade, leaving some room inside to set up the rocket and mortar tubes and a platform to launch spinning things from. These precautions proved wise; hundreds of people showed up, many of them driving all the way to the site in 4-wheelers. Later in the night they began driving around, roaming over the dunes, creating a scene that strongly reminded me of the outlaw bands swarming about the petrochemical plant in The Road Warrior.
Scott walked around holding a 300-string of firecrackers from one end, waving it as lit firecrackers dripped off and produced a sort of strobe effect on him. For a while he had an enormous flash powder bomb projecting ludicrously out of his shirt pocket. He had also rolled up some 300-strings into tight bundles. One would expect these to go off rather fast, perhaps in a few seconds, since all the fuses were packed together. In fact, they all went off in less than a second, creating an incredible barrage of sound like the tearing of a cosmic piece of cloth.
One of his other impressive items was an F100-0 engine taped on a long stick with a huge flash powder payload, making it a ridiculously powerful sort of skyrocket. The “-0” means that there is no delay between when the engine finishes thrusting and when the 'load goes off. An F100 is made to produce a tremendous thrust for less than a second, so the net result was a bellowing roar as the rocket leapt out of the tube and, having insufficient guidance, streaked down the range parallel to the ground. It shot a dazzling red flame out of its nozzle before its flight was abruptly terminated by a thunderous report that rolled among the dunes. The cheers from the crowd were long and vigorous.
They had five tubes set up for the Festival Balls, and the synchronized bursts lit up the sky spectacularly. Later, as they had the year before, they began holding the tubes as the shells lofted. Laurence went a bit further and held his tube with one hand. People did other somewhat risky things as the night wore on; I watched Laurence examine the rather volatile contents of his chest with a road flare that dripped flaming bits on the 'works.
Luke had an 8mm movie camera to record the festivities. He may have gotten some good scenes when we set off our annual Ground Illumination flare. It lit up the surrealistic spectacle of hundreds of partiers gathered 'round the bonfire and bar, with the 4-wheelers competing nearby to see who could climb the steepest dune.
We made sure we only used cardboard tubes to launch rockets from. Of course Laurence's rockets blew them in half once again, but at least there was no plastic flying. When an engine came to life deep in a tube, the inside briefly glowed and flickered like an atomic cannon before the rocket burst forth.
The largest item we had was a piece of carpet tube about a foot (30 cm) long full of flash powder. Actually, many years before when we were still playing with blasting powder I had found three different sizes of tube that fit inside each other and glued them together, making an extremely strong casing. The sound it made seemed loud enough to echo across the bay, and it left a fair sized crater.
We ended by blowing up the fire with one of Scott's more powerful devices. It was even better than the year before. This time the pulverized coals formed a mushroom cloud with an incandescent head, like an atomic bomb. As its brilliance faded, a vast cloud of sparks streamed up into the sky.
By then we had reached the wee hours of the morning, and we decided to spend the night at the site. We got a bit of sleep as an owl kept us company from its perch on the sand plant's one remaining tank.
The year after that I finally made another tennis ball cannon. I searched though grocery stores and found that as I had feared there were no soft drinks still packaged in steel cans. Then I roamed the aisles of Liquor Barn. I had almost given up when I got to the “International Beer” section, where I was delighted to find that there was exactly one brand that was still steel-canned, South Pacific Export Lager from Papua New Guinea. I gave a six-pack to my brother and mother to drink. However, by the time I was ready to begin construction, I was beginning to feel that I didn't want to just make another Mark III. The Mark IV that I had never built still seemed impractical, but I was sure I could come up with some improvement. At the very least, I thought I would make the barrel out of steel tubing.
A visit to Orchard Supply was disappointing. I had hoped that I would be lucky enough to find some light steel tubing just the right size for a tennis ball. Not only did I not find that, there wasn't anything close. A piece of ordinary pipe of the required dimensions would have been ridiculously heavy. As I stood looking at the plethora of plumbing parts, wondering what on Earth I would do, my eyes fell on the plastic pipe section. I began to feel a change of mindset coming over me. The thought of a plastic cannon had never before passed through my head. Surely it would melt or explode? But, as I considered it, it occurred to me that the combustion in a cannon was of such short duration (not even long enough, as I well remembered, to ignite a fuse) that it might not melt after all. Also, though PVC pipe is quite brittle, ABS (used for drain pipes and vents) is a light, strong, and shock resistant plastic. I surveyed the various ABS parts available and went home to plan.
The new design I came up with for the Mark IV started with a chamber made from a two foot (60 cm) section of three inch (7 cm) ABS pipe. I glued cleanout adapters to both ends so that I could screw plugs into them, and drilled a hole in the rear plug to spray fuel in. The hole was the size of the spray bottle nozzle. I bolted a washer over the hole inside the cap, so that when a spray bottle was put into the hole it was correctly centered to spray though the small hole in the washer. This eliminated a problem that occurred with the Mark III: if the nozzle wasn't aligned correctly it would spray fuel all over the bottom of the cannon. The chamber was too large for 2½″ (6cm) tennis balls; I couldn't find ABS pipe in that size. Therefore, this model had a separate barrel inside the forward part of the combustion chamber. To form the barrel I cut a hole of the correct size in the forward plug and epoxied a can into it in such a way that it would fit back into the chamber. I was initially going to use one of the beer cans, but at the last moment discovered that a solvent can I just finished was exactly the same diameter. It was 50% longer than a beer can, giving a greater length for accelleration. The large chamber also provided extra power. The forward plug could be unscrewed to repair the barrel, and the rear plug unscrewed to air out the cannon after firing much more effectively than was possible with earlier designs.
I made handles by sliding bicycle grips over pieces of ½″ (1¼cm) steel pipe (I needed the extra strength of metal here), and screwed them into pipe nuts that I bolted to the chamber. Next to the rear handle I put my trigger. A few years before I had found in a surplus catalog some large 20,000 volt piezo sparking units that were intended to light gas ranges, and had bought some in anticipation of the day when I'd make another TBC. I fit one into the long part of a PVC tee, connected it to a mini lawnmower spark plug which I put into the tap part of the tee, and fastened the tee to a hole in the chamber in such a way that the spark plug stuck in where it could ignite the fuel mix.
The result of all this looked rather impressive: large black chamber with black rubber handles bolted on, 2½″ muzzle that showed polished steel on its inside with a fluorescent green tennis ball lurking in its depths, and a contrasting white tee sticking out with a huge black-bordered red button on one end mounted near the rear handle. It worked very well too. The ignition system was powerful enough that it didn't need a match to start it the first time, and it only required one shot to warm up. It never got hot enough to harm the plastic parts as long as I was careful to not let residual fuel keep burning. It was also very durable and extremely powerful; when I fired it inside the windows rattled and outside the ball sailed off into the distance. A bit of experimention on an extra ABS part showed that using acetone fuel would be a very bad idea, but denatured alcohol, which worked almost as well, didn't affect it at all. I finally had a TBC that was hassle-free and pure fun.