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The "Pinewood Derby" is a racing event for Cub Scouts in the Boy Scouts of America. Cub Scouts, with the help of parents, build their own cars from wood, usually from kits containing a block of pine, plastic wheels and metal axles. With the popularity of the pinewood derby, other organizations have developed similar events and a small industry has developed to provide tracks, timers, scales and other products. The pinewood derby was selected as part of "America's 100 Best" in 2006 as "a celebrated rite of spring" by Reader's Digest. Similar Cub Scouting events include the raingutter regatta with boats and the space derby using rubber band powered rockets.

ORIGINS
Cubmaster Don Murphy organized the first pinewood derby, held on May 15, 1953 in Manhattan Beach, California by Pack 280c. Murphy's son was too young to participate in the popular Soap Box Derby races, so he came up with the idea of racing miniature wood cars. The cars had the same gravity-powered concept as the full-size Soap Box Derby cars, but were much smaller and easier to build. After Don Murphy's first race in 1953 the Los Angeles County Department of Recreation copied the pinewood derby with Murphy's permission. Don Murphy died July 1 2008, at age 90 of pneumonia.

In the 1980s, the design of the block was changed from a cutout block, consistent with a 1940's style front-engined Indy 500 car, to a solid block. The tires were also changed from narrow, hard plastic, to wider "slicks".

A video game version of the pinewood derby was released by ImaginEngine in September 2008.

CONSTRUCTION
The Scout is given a block of wood made of pine with two notches for wheels, four plastic wheels and four nails. The finished car must use all nine pieces, must not exceed a certain weight (usually five ounces), must not exceed a certain length and must fit on the track used by that particular scout pack.

Blocks can be whittled with a hand knife or a band saw or Dremel carving tool for major shaping. Decals can be bought at scout shops or hobby shops. It is also possible to use standard model decals to replicate actual racing cars such as Richard Petty's 1970 Plymouth Superbird, shown at right. The original style is based on open wheel cars, however, fender or body kits are available, or wheels can simply be placed outboard of the body.

Other than the previous basic design rules, the Cub Scout is able to carve and decorate the car as he chooses. Many Cub Scouts also add weights to the final design to bring the car to the maximum allowable weight.Coins, glue in lead pieces, or melted lead are common ways to add weight. Cars typically vary from unfinished blocks to whimsical objects, to accurate replicas of actual cars. The fastest cars tend to resemble low doorstops, with weight at the rear. Graphite is usually the only lubricant allowed, and it often helps to polish the provided nails.

The idea behind the pinewood derby is for the parent, usually the father, but occasionally the mother or grandparent, to spend time helping the child design, carve, paint, add weights, and tune the final car. However, it is often the case that the parent takes over the construction of the car, an aspect of the event that was lampooned in the 2005 film Down and Derby.

COMPETITION
The track usually has two to six lanes and slopes down to the ground, since the cars are powered by gravity. Tracks may be owned by the pack or rented. The race is run in heats, giving every car the chance to run on each lane. The racers can be grouped with others from the same rank (Tiger Cubs, Wolf Cubs, Bear Cubs, etc.), or can compete against the pack as a whole.

The first, second, and third place winners usually receive ribbons, medals or trophies. Some packs also award on the basis of car design. The first place race winners get to advance to the district level, then each of the district-wide race winners get to race each other from across the entire council.

CAR MODIFICATIONS
The force propelling a pinewood derby car is gravity and the only opposing force is friction, therefore car modifications are aimed at minimizing the friction that occurs when the wheel spins on the axle, contacts the axle head or car body, or contacts the track guide rail.[9] Friction due to wind resistance is a minor, although not insignificant, factor. The wheel tread can be sanded or lathed and the inner surface of the hub can be coned to minimize the contact area between the hub and body. Polishing the wheel, especially the inner hub, with a plastic polish can also reduce friction. Often one front wheel is raised slightly so that it does not contact the track and add to the rolling resistance. Axles are filed or lathed to remove the burr and crimp marks and polished smooth. More extensive modifications involve tapering the axle head and cutting a notch to minimize the wheel-to-axle contact area. Note that packs can establish additional rules for what, if any, modifications are allowed. In some areas, no changes can be made to the axles or wheels.

A second consideration is the rotational energy stored in the wheels. The pinewood derby car converts gravitational potential energy into translational kinetic energy (speed) plus rotational energy. Heavier wheel have a greater moment of inertia and their spinning takes away energy that would otherwise contribute to the speed of the car. A standard wheel has a mass of 3.6 g, but this can be reduced to as little as 1 g by removing material from the inside of the wheel. A raised wheel can reduce the rotational energy up to one-quarter, but this advantage is less with a bumpy track.

A proper lubricant, typically graphite powder, is essential. Wheel alignment is important both to minimize wheel contact with the axle head and body as well as to limit the contact between the wheels and guide rail as the car travels down the track. The center of mass of a typical car is low and slightly ahead of the rear axle, which helps the car track straight as well as providing a slight advantage due to the additional gravitational potential energy