This is one from earlier this spring. Over the holidays when we were in Wichita, we cut out the basic shape for Quinn's Pinewood Derby car on Grandpa's band saw. We kept the shape simple. At home we finished it up with some chiseling, sanding, drilling, and painting.
We drilled holes in the back for cylindrical weights, and filled the holes with epoxy, then smoothed them with putty. We recessed the bottom of the car and screwed flat weights underneath. The car has to weigh not more than 5.0 oz, and getting as close to that but not over is critical for a winning car -- which probably means that 5.09 oz. is the weight to target. We took the car to Playmakers and used the digital shoe scale to get the weight to 5.1 oz. We had some small screws in the bottom we planned to remove to bring it down to exactly 5.0 oz at the official weigh-in, held the night before the race. Unfortunately, on the official scale we were only at 4.9 oz. We had brought some extra little screws I could have added to the bottom to get it up to 5.0 (we even had pre-drilled holes), but at that time, for some reason I just didn't bother. In hindsight, I sort of wish I had, since we'd gone to the effort to polish and dry-lube the axles; I should have added that extra 0.15 oz.
It was fun to build. Quinn did much of the sanding, and most of the painting. I got to use the power tools and chisel.
The car did pretty well, making through first series of races and into the top six. Here, Quinn's car wins another heat:
On the polished aluminum track, the cars were fast, and the time-difference between winning cars was often down to less than 0.01 seconds. Quinn's car came in 6th overall. The overall winner is that red car second from the right.
The race was run fairly, and in good fun, which made it a good experience. We've thought we might do cub scouts again for the sole purpose of making next year's winning car. But I don't think we will.
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