Rockin' the Pinewood Derby
Since our first middle-of-the-road foray in Pinewood Derby, the Boy and I have gotten our collective sh - ahh, stuff - together and have rocked it pretty hard. In our second year, we entered two cars - a family car and the Boy's car. Out of a field of 87 cars, the family car wound up 12th overall, and 2nd in the "Friends and Family" division. Poe's car placed as high as 2nd place overall.
He'd actually won 1st in his den, but since he was going to get the 2nd in Pack trophy, they gave the 1st in Den trophy to the next fastest kid in his Den. Nevertheless, this was a considerable improvement over the year before, but we figured we could do better.
This year, our two entries were faster - but so was the whole field. This time around, the family car placed 5th overall (in a field of 105 cars), and 1st in the "Friends and Family" division. But Poe's car ended up 6th overall - earning him a 1st in his Den, but we still missed the coveted 1st in Pack trophy. I was closing in on Dad's mastery, but wasn't quite there yet.
Next year, I believe I have all the tools to make it happen. The next three sections summarize what I've learned about the art of winning in the Pinewood Derby.
Weight
Your car can only be 5 ounces. That's not just an upper limit, it's a lower limit too - if you're car isn't exactly 5 ounces, you're ripping yourself off. The car's energy comes from weight and gravity - you want the most weight you can get, and make sure gravity is pulling it down for as long as possible. But to make sure you have all the weight you can, you first need a scale.
Get a scale that measures down to 1 gram increments. If you play your cards right, and butter Mom up, you can use her kitchen scale (or have her buy one) that will work for your purposes. Or check out Amazon or eBay - you can easily pick one up for less than $30.
Then there's the weight itself - lead will do, but tungsten has a greater density - more weight in less area. This is important when it comes to precise placement of weight in the car, which brings us to...
Weight Balance
Next, you want to put as much of that weight as you can as far away from the starting line as possible while still keeping it in front of the rear axle. This means you want a short tail on the car. The further that mass can roll down before the track straightens out, the better. But you don't want it behind the axle or you risk popping a wheelie, which can cause your tail to drag on the track, losing speed, or worse, leaving the track all together. In short, you want the center of gravity of the car around 3/4 to 1 inch in front of the rear axle. You should be able to balance the car - with the wheels on - on a pencil placed just in front of the rear wheels.
To get the most mass at that crucial point, you need to minimize the amount of wood weight and maximize the amount of added metal weights. That means a lean, mean body design that includes only enough wood to attach the axles, act as a front bumper (for the starting pin), and attach your weights. My fastest car body weighed less than .9 ounces - and less than 1.5 ounces with the wheels on - which meant I was able to add over 3.5 ounces of tungsten weights in the critical center of gravity area.
Reduce Friction
Once you've maximized all that power, you don't want to lose it to bad wheels and axles. You need to make sure the axles are smooth and the wheels are smooth and straight. I won't get into the mechanics of doing it, because there are plenty of sites out there that explain that. Just know you need to do it.
Then, once the car's assembled and your wheels and axles are straight, it's graphite time. The critical task here is making sure the wheels and axles are properly lubricated and broken in. You need to not only put the graphite on but make sure it's really worked in there so that by the time you hit the track, you're at maximum performance. You'll notice the cars that haven't been broken in - their times will get consistently better as the race goes on. A broken-in car starts off great and remains good throughout the race.
The best trick I've found for this involves graphite and a Dremel tool with the cotton wheel attachment. Sprinkle liberal amounts of graphite on the axle by the inner part of the wheel hub. Then, with the Dremel spinning at the slowest speed, lightly touch the cotton wheel to your car's wheel (taking car to spin it in the same direction it will roll when it races). Repeat several more times, so the car's wheel is spinning very fast. It's important that you don't hold the Dremel to it continuously, because it will melt your wheel! It's important to just get your car's wheel spinning rapidly and keep it spinning while the graphite works its way down the hub. Do this for at least a minute or two per wheel.
This is the one critical area where I may have failed with Poe's car this last year. The Family car got the full graphite treatment, but I did that one first and felt like I'd tired of the routine by the time I got to Poe's, and didn't pack as much graphite in. The proof came in the actual races - the Family car, with a full load of graphite, produced the most consistent times of any car in the race - each time in each heat was within 6/1000 of a second. When Poe's car ran, it started off with one of the fastest times I've ever seen, but quickly dropped off, and in the final heat, was almost 5/100 of a second slower.
That number may not seem significant, but the standings are figured by average time in six heats. If his car had maintained the pace set in the first race to within 6/1000 like the other car did, he'd have easily taken first.
Conclusion
I can't guarantee a 1st place finish, but if you account for three things: weight, weight balance, and friction reduction - you can count on being highly competitive.