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The club activities of the NJ Chapter of BMW CCA, although diverse, are thoroughly automotive. Some years ago our club president, whose children were involved in Cub Scouting and Pinewood Derby, thought that our club would be interested in an adult participation event. Boy, were we ever! We didn't have to pretend that our kids made the cars. I built a 2-lane track that is easily portable and works smoothly, and I have been making somewhat "different" entries for our annual competition. These are pictures of 4 of my pinewood derby cars.
The latest entry is modeled after the BMW LMR LeMans racer. Like my other cars, it has full-width wheelhouses. The spoiler was made from pieces of a polystyrene mailing tube. The decals are homemade, done with clear mailing labels and a laser printer. Our club has made slight alterations to Pinewood rules; we allow less than 3/8" clearance along the sides of the car, although 3/8" is still required under the middle of the car. The headlights are stick-on items found in craft stores, right next to stick-on eyeballs.
The white sedan is modeled after my own '71 2002. The trim is done with a felt-tip pen, and the windows are just black paint. The bulk of the model required that I hollow it out just to bring it down to regulation weight, as with some of the other models. The open roadster uses a 1939 BMW 328 Mille Miglia as prototype. It has seats, steering wheel, and a gearshift lever.
The walnut car is my own design, carved from a solid block of black walnut. There has been some dispute that it is not really legal, since it isn't made of pine. The rules require that you use the materials in the kit; it doesn't say you cannot add to it. At least it is finished in clear lacquer, so there is no doubt about the woodgrain. I would think that once a model is painted, you cannot tell what it was made from.
It is interesting to note that only one of these cars ever won a trophy. It shows that we have a keen competition, and that, for all the preparation, results always have a large random element to them.
Below is a picture of my Pinewood 2000 entry. It incorporates rear weight bias, streamlining, and shaved wheels to reduce rotational moments of inertia. It took 4th place!
Below is my most recent Pinewood Derby entry. Over the years, various refinements have enhanced its performance, and it was a first place winner in 2007.
One of the most important tweaks is weight in the rear. The idea is that the car starts nose down, so the back of the car is higher, and will fall further than the front. This increases the potential energy of weight at the rear of the car more than the front. Since this is all that propels the car, this makes all the difference compared to a car with more centrally placed weight. This car not only has a slab of lead molded into the rear of the body, but the rest of the car is little more than a stick. The more weight you remove from the front of the car, the more you can put in back.
It is important that the center of mass be in front of the rear axle, so the nose doesn’t pop up, so the rear axle should be as far to the rear as possible. It also seems that moving the axles further apart increase the stability and prevents wiggling.
Shaving the wheels, if rules permit, will lighten the wheels and decrease rotational moments of inertia. This means that less energy will be stored in the rotating wheel masses like flywheels, as the car moves, and the car will accelerate more quickly.
Last Modified May 7, 2000