In any case, the event went spectacularly well. Last Saturday evening (after dinner, so there was no food involved aside from some root beer floats), we gathered in the parking lot of the church where we set up a ramp for our pinewood derby. The sun was going down and the weather was great, so we expected there would be no launch holds. And there wasn't.
We started with the "gravity" portion of the evening. There were about a dozen racers who all brought their cars and put them down the track. As we didn't bring any paper to keep track of the brackets, our Elders Quorum President basically wandered around, attempting to keep the winners and losers in his head, and asked everybody "how many times have you lost?!" It was hilarious. Nobody really cared. We just wanted to have a good time. It was an evening without the kids (though some people didn't get that memo, but it was fine ...) and it was our time to do Stupid Guy Stuff.
My car was a beautiful green car (we had a leftover can of spray paint from last year) that I molded into an aerodynamic wonder. My ultimate goal was to keep it on the track. I was inclined to put wings on the side, but I was worried about impinging on the space of the car I was racing, so I couldn't do that directly. Nevertheless, after stumbling around in the garage looking for leftover hardware that I could put to good use, I came across some brackets that would do a perfect job. I bent them slightly and then carved grooves in the side of the car to mount them. The intent was not only to provide some control over air flow, but also to weigh the car down.
I drilled the hole in the back of the car to just the right diameter for the booster I had purchased (the smallest booster I could get from the hobby shop), and then drilled a front hole so that the engine could back-vent, as engines of that size normally do in order to pop a parachute out of a hobby rocket. (Later that I discovered that you can actually buy rockets that don't back-vent, but whatever.)
After assembling the car, I found that it was still too light -- about an ounce below 5 ounces -- to meaningfully compete in the "gravity" races (even though there were no rules, specifically about the weight). So, I pondered what to do. Standing in my kitchen, I looked across the room where the kids had some Legos scattered on the floor, and it hit me that I should mount a Lego dude onboard to give the ride some style. After final assembly, I concluded that the Lego dude would participate only in the "gravity" races, as we didn't want any casualties during the "powered" races.
The end result was pretty impressive:
During the races, though, my little Lego dude couldn't really compete. He was able to beat the balloon-propelled car and a few others that had some obvious mechanical limitations, but even so, he went down in style. His protective dome even got scuffed a little bit after his first race when he skittered across the asphalt of the parking lot.
With twelve cars, the ultimate winner was a guy who ended up racing several cars of his, and he took both first and second place. Nobody was upset, we were just anxious for the next phase of the races to begin. We decided it would be best to lay the track flat for this phase of the evening, and some guys attempted to split some wires so that both rocket-powered cars could be launched with one starter, but that didn't work, so it was down to two guys pushing two different buttons.
The first successful race was with two cars that were made from a kit. They looked nearly identical, and had very big engines in them. I immediately noticed that neither of them had holes to manage the back-venting. After the typical count-down, the two cars zipped down the track and bounced off the end cushion. Immediately thereafter, the back-vent from the engines caused a secondary burst of fire, ejected the rocket engine from the back of the cars, and threw fire into the face of a bystander! Check out the video:
After the smoke dissipated, we determined she was all right. We learned to stand further away and be prepared for the secondary blast.
Soon it was my turn. One time, I went up against a guy who had a toy helicopter motor mounted in his car to make the wheels spin like mad. I put my car down, sans Lego dude, and fully expected my car to smoke the guy. Not so! Much to my surprise, the littlest engine I could get from the hobby shop was a very small engine indeed. I got smoked! It was so embarrassing. Here I am, an aerospace engineer who works for NASA, and my car got smoked! By a non-rocket-propelled vehicle! How horrid! Some of the by-standers saw the whole thing and were stunned, as well. In fact, I think it even got tweeted to President Obama, who was tempted to give me a bailout.
Happily, another fellow who was there had the same size engines I had, but with higher thrust ratings. So, time for a rematch. And this time, I cleaned his clock. He wasn't even halfway down the track before I passed the finish line! It was impressive. To make it even more impressive, my car stayed on the track!
Indeed, every race my car participated in stayed on the track, which was not the case for every other rocket-powered car there (and some of the non-rocket-powered ones, too). My goal accomplished, we moved on to more fun stuff.
We moved the track over to the grass and raised the end. With our rocket-powered cars, you can imagine the end result of that!
At first, we raised it only about a foot. Then we came to our senses and realized that if we were going to intentionally launch cars into the air, we should do it right, so we raised the end of the track up to about a 45 degree angle. What followed was awe-inspiring. With the sun now down and it quickly getting dark, we watched as a streak of fire screamed up the track and arced into the night. It was a true thing of beauty. This was then punctuated by a secondary flash of light from the back-venting that would fire like a rifle shot in some random direction, the result of the car tumbling into the distance.
Check it out:
It was a great night. As we all departed, we were conspiring about how to make the event even better next year. I look forward to it, with visions of winged cars and really big engines in my mind ...