Some plans for building soap box racers include such styles as stock cars, super stock cars and scotties. Available from the All-American Soap Box Derby (AASBD), the international governing body of soap box racing, these plans comply with all rules for building cars raced in sanctioned events. However, there are hundreds of other designs for both chassis and body.
While some plans call for a metal frame, modern soap box cars are still usually at least partially wooden. However, most follow AASBD rules for wheel and axle types, construction and maximum weight, depending on division. They are modeled after the wooden first soap box racers, built from crates used to ship soap, which had four wheels and no motor or sophisticated steering system. Known as “gravity racers,” their speed depends on a sloping course and a push start.
Body decorations on homemade soap racers can vary widely as long as the car meets safety requirements and maximum racing weight. However, kit cars have evolved a streamlined design constructed on a wooden chassis with regulation axles and wheels. Stock cars built according to AASBD standards are designed for drivers ages 7 to 13, who are up to 5 feet 3 inches tall and weigh 125 pounds, for a combined racing weight of 200 pounds. Super stock cars are built for drivers ages 9 to 18, up to 6 feet tall and weighing 150 pounds, for a combined weight of 240 pounds. Scotties, cars raced in the Masters division at 255 pounds, are built for drivers 10 to 20 years old, up to 6 feet tall and weighing 160 pounds.