Five main parts of a good design:
- Maximize momentum. Have a car that is as close to 5.0 ounces as possible, without going over. Place most of the weight in the rear of the car, so it has the farthest distance to travel downhill (i..e, weight at the front of the car will have a few inches less downhill travel).
- Aerodynamic shape. The difference between a square front and sloped front may provide a negligible advantage, but every advantage counts!
- Axle and wheel preparation. Make the axles as smooth and polished as possible. Ensure the wheel running surface is flat and without any burs.
- Lubrication. Use only dry graphite as as lubricant. Apply some right before race time to ensure the axles stay as lubricated as possible.
- Axle alignment. If the car doesn't roll straight, it may cause zig-zagging on the track, which slows it. The axles should be exactly perpendicular to the side of the car, to help ensure straight tracking.
More resources:
- See the Boy's Life guide for building a fast Pinewood Derby Car
- Watch this video to learn the science behind what makes a Derby car faster: