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While each Pack can have variations on the rules, most of them are pretty standardized. The cars must weigh a maximum of 5 ounces and they have to be made out of the wood, nails and wheels that came in the kit. You can add things to the build, like detailing bits, ballast weights and paint, but the basics must remain. There are also some dimensions that are listed to insure that the car fits on the standard four-lane track.
I tried to teach my son about a variety of physics and engineering principles. There are three primary concepts—you want to maximize the potential energy of the car’s weight at the top of the track. You want to minimize friction in the wheels and axles. You also want to make sure the car has as little aerodynamic drag as possible.
With those tenets in mind, we carved a shape like a Bonneville streamliner, we polished the axles and wheels with a mixture of sandpaper and polish and we added ballast weights to bring the car as close to the maximum as we could.
To make the most of the potential energy, we positioned the weight as far back as we could, which made the center of gravity right around the rear axle.
