Pinewood derby
Encyclopedia
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.
, 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.
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".
The Scout is given a block of wood made of pine
with two notches for wheel
s, 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 bandsaw or Dremel
carving tool for major shaping. Decal
s 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, and 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
, and also in a 2009 episode
of South Park
. The quest for a fast car supports a cottage industry that supplies modified wheels, axles, and blocks as well as videos and instruction books. While a pinewood derby car kit costs around $4, a set of modified wheels and axles can sell for more than ten times that amount. These aftermarket
items are legal under some Pack rules since the parts originally came from an official Boy Scouts of America (BSA) kit. Complete cars can be purchased on eBay
and elsewhere for around $100 to $200. Although these cars violate the spirit of the event, if not the rules, enforcement can be difficult.
Model manufacturer Revell
was licensed by the BSA to produce pinewood derby kits with a release in December 2009.
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.
As the popularity of the pinewood derby grew, other organizations adopted the concept. Pinewood derby is a registered trademark of the BSA, so most use different names. Each derby has slightly different rules for making and racing their cars.
The forces propelling a pinewood derby car are gravity and inertia
, the opposing forces are friction
and air drag. Therefore, car modifications are aimed at maximizing the potential energy
in the car design and minimizing the air drag and the friction that occurs when the wheel spins on the axle, contacts the axle head or car body, or contacts the track guide rail. Friction due to air drag 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 wheels 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.
Another consideration is the track itself. A track that is mostly sloped, with little flat at the end, can really allow cars with minimal mass in their wheels to shine. However, a track with a steep slope and then a long flat section can penalize such cars due to the quick loss of energy they experience once they have reached the bottom, when all potential energy has been transferred to kinetic and rotational energy. Such cars will take a lead on the downslope, but may be passed by cars with more energy "stored" away as rotational energy on the flat.
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.
Boy Scouts of America
The Boy Scouts of America is one of the largest youth organizations in the United States, with over 4.5 million youth members in its age-related divisions...
. Cub Scouts, with the help of parents, build their own cars from wood, usually from kits containing a block of pine
Pine
Pines are trees in the genus Pinus ,in the family Pinaceae. They make up the monotypic subfamily Pinoideae. There are about 115 species of pine, although different authorities accept between 105 and 125 species.-Etymology:...
, plastic wheels
Wheel
A wheel is a device that allows heavy objects to be moved easily through rotating on an axle through its center, facilitating movement or transportation while supporting a load, or performing labor in machines. Common examples found in transport applications. A wheel, together with an axle,...
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
Reader's Digest
Reader's Digest is a general interest family magazine, published ten times annually. Formerly based in Chappaqua, New York, its headquarters is now in New York City. It was founded in 1922, by DeWitt Wallace and Lila Bell Wallace...
. Similar Cub Scouting events include the raingutter regatta
Raingutter regatta
The raingutter regatta is a racing event for Cub Scouts in the Boy Scouts of America that is the sailboat equivalent of the pinewood derby. The sailboat kit consists of a seven-inch long balsa wood hull, a 6-1/2 inch mast, plastic sail, plastic rudder, and metal keel. Within the basic design...
with boats and the space derby
Space derby
The space derby is a racing event for Cub Scouts in the Boy Scouts of America that is similar to the pinewood derby car race. Cub Scouts race miniature balsa wood rockets that are propelled by a rubber band and propeller.-Construction:The space derby kit consists of a balsa wood block, propeller...
using rubber band powered rockets.
Origins
Cubmaster Don Murphy organized the first pinewood derby, held on May 15, 1953, in Manhattan Beach, CaliforniaManhattan Beach, California
Manhattan Beach is the wealthiest beachfront city located in southwestern Los Angeles County, California, USA. The city is on the Pacific coast, south of El Segundo, and north of Hermosa Beach. Manhattan Beach is the home of both beach and indoor volleyball, and surfing. During the winter, the...
, by Pack 280c
Los Angeles Area Council
Founded in 1915, the Los Angeles Area Council serves most of the City of Los Angeles as well as several other cities in the greater Los Angeles area. It is one of five Boy Scouts of America councils in Los Angeles County, California. Since its founding in 1915, the Los Angeles Area Council has...
. Murphy's son was too young to participate in the popular Soap Box Derby
Soap Box Derby
The Soap Box Derby is a youth soapbox car racing program which has been run in the United States since 1934. World Championship finals are held each July at Derby Downs in Akron, Ohio...
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.
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".
Construction
Pine
Pines are trees in the genus Pinus ,in the family Pinaceae. They make up the monotypic subfamily Pinoideae. There are about 115 species of pine, although different authorities accept between 105 and 125 species.-Etymology:...
with two notches for wheel
Wheel
A wheel is a device that allows heavy objects to be moved easily through rotating on an axle through its center, facilitating movement or transportation while supporting a load, or performing labor in machines. Common examples found in transport applications. A wheel, together with an axle,...
s, four plastic
Plastic
A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...
wheels and four nails
Nail (engineering)
In woodworking and construction, a nail is a pin-shaped, sharp object of hard metal or alloy used as a fastener. Formerly wrought iron, today's nails are typically made of steel, often dipped or coated to prevent corrosion in harsh conditions or improve adhesion...
. 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
Whittling
Whittling is the art of carving shapes typically out of raw wood or bone with a knife.Whittling is typically performed with a light, small-bladed knife, usually a pocket knife. Specialised whittling knives are available as well...
with a hand knife or a bandsaw or Dremel
Dremel
Dremel is a brand of power tools known primarily for their rotary tools. The tools were originally developed by Albert J. Dremel, who founded the Dremel Company in 1932 in Racine, Wisconsin. In 1993, the company was purchased by Robert Bosch GmbH, and today it is a division of the Robert Bosch Tool...
carving tool for major shaping. Decal
Decal
A decal or transfer is a plastic, cloth, paper or ceramic substrate that has printed on it a pattern or image that can be moved to another surface upon contact, usually with the aid of heat or water. The word is short for decalcomania...
s 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
Richard Petty
Richard Lee Petty is a former NASCAR driver who raced in the Strictly Stock/Grand National Era and the NASCAR Winston Cup Series...
's 1970 Plymouth Superbird
Plymouth Superbird
The short-lived Plymouth Road Runner Superbird was a highly modified version of the Plymouth Road Runner with well known graphics and horn. It was the factory's follow up stock car racing design for the 1970 season to the Dodge Charger Daytona of 1969, and incorporated many engineering changes and...
, 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, and 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
Down and Derby
Down and Derby is a 2005 comedy film about a Cub Scouts' pinewood derby race. The cars in the race are meant to be built from kits by Cub Scouts with appropriate adult supervision, but in Down and Derby the fathers of four Scouts take over the project from their kids, and get carried away by their...
, and also in a 2009 episode
Pinewood Derby (South Park)
"Pinewood Derby" is the sixth episode of the thirteenth season of the American animated television series South Park, and the 187th overall episode of the series. It originally aired on Comedy Central in the United States on April 15, 2009 and in the United Kingdom on April 17, 2009...
of South Park
South Park
South Park is an American animated television series created by Trey Parker and Matt Stone for the Comedy Central television network. Intended for mature audiences, the show has become famous for its crude language, surreal, satirical, and dark humor that lampoons a wide range of topics...
. The quest for a fast car supports a cottage industry that supplies modified wheels, axles, and blocks as well as videos and instruction books. While a pinewood derby car kit costs around $4, a set of modified wheels and axles can sell for more than ten times that amount. These aftermarket
Aftermarket (automotive)
The automotive aftermarket is the secondary market of the automotive industry, concerned with the manufacturing, remanufacturing, distribution, retailing, and installation of all vehicle parts, chemicals, tools, equipment and accessories for light and heavy vehicles, after the sale of the...
items are legal under some Pack rules since the parts originally came from an official Boy Scouts of America (BSA) kit. Complete cars can be purchased on eBay
EBay
eBay Inc. is an American internet consumer-to-consumer corporation that manages eBay.com, an online auction and shopping website in which people and businesses buy and sell a broad variety of goods and services worldwide...
and elsewhere for around $100 to $200. Although these cars violate the spirit of the event, if not the rules, enforcement can be difficult.
Revell
Revell is the brand name today of two manufacturers of scale plastic models. The original US company merged with another, Monogram, but now trades only under the Revell name. European Revell Germany separated from the US company in 2006.-Early history:...
was licensed by the BSA to produce pinewood derby kits with a release in December 2009.
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
Trophy
A trophy is a reward for a specific achievement, and serves as recognition or evidence of merit. Trophies are most often awarded for sporting events, from youth sports to professional level athletics...
. 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.
Other races
- AwanaAwanaAWANA is an international evangelical nonprofit organization founded in 1950, headquartered in Streamwood, Illinois...
has the Awana Grand Prix. - Christian Service BrigadeChristian Service BrigadeChristian Service Brigade is a non-denominational Christian organization for men and boys in the United States and Canada. Often referred to as "Brigade," it is organized according to a model historically similar to that of international Boys Brigade and Scouting organizations...
uses the name Shape N Race Derby. - Royal AmbassadorsSouthern Baptist ConventionThe Southern Baptist Convention is a United States-based Christian denomination. It is the world's largest Baptist denomination and the largest Protestant body in the United States, with over 16 million members...
have RA Racers. - Royal RangersRoyal RangersRoyal Rangers is a worldwide ministry of the Assemblies of God and is designed to provide youth with challenging activities while providing them with Christian instruction. Royal Rangers International is open to participation of both boys and girls, while the US only allows boy participation in...
use a different kit with an original style narrow wheel, adjustable screw axle and wooden dowel axle housing. - Scouts CanadaScouts CanadaScouts Canada is a Canadian Scouting association that, in affiliation with the French-language Association des Scouts du Canada, is a member of the World Organization of the Scout Movement...
has the kub kar rally for Cub Scouts, beaver buggies for Beaver Scouts, and scout express trucks for Scouts. - Valve cover racingValve cover racingValve cover racing is a competitive event similar to the Pinewood derby, but vehicles are made from a valve cover from an internal combustion car engine, rather than of wood blocks,...
is an event at some car shows using vehicles made from valve covers. - Woodcar Independent Racing LeagueWoodcar Independent Racing LeagueWoodcar Independent Racing League is an independent racing league for pinewood car builders.Pinewood car racing was popularized by the well known Boy Scout sanctioned Pinewood Derby. Unlike the Scout races, WIRL races are open to people of all ages and participants are not required to be a member...
open to anyone of any age - YMCAYMCAThe Young Men's Christian Association is a worldwide organization of more than 45 million members from 125 national federations affiliated through the World Alliance of YMCAs...
chule cars use the same kit as the Royal Rangers. - BSA has recently added an 18-wheeler category to Pinewood Derby, similar to scout express trucks from Scouts Canada.
Car modifications
Inertia
Inertia is the resistance of any physical object to a change in its state of motion or rest, or the tendency of an object to resist any change in its motion. It is proportional to an object's mass. The principle of inertia is one of the fundamental principles of classical physics which are used to...
, the opposing forces are friction
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...
and air drag. Therefore, car modifications are aimed at maximizing the potential energy
Potential energy
In physics, potential energy is the energy stored in a body or in a system due to its position in a force field or due to its configuration. The SI unit of measure for energy and work is the Joule...
in the car design and minimizing the air drag and the friction that occurs when the wheel spins on the axle, contacts the axle head or car body, or contacts the track guide rail. Friction due to air drag is a minor, although not insignificant, factor. The wheel tread
Tread
The tread of a tire or track refers to the rubber on its circumference that makes contact with the road. As tires are used, the tread is worn off, limiting its effectiveness in providing traction. A worn tire tread can often be retreaded. The word tread is often used incorrectly to refer to the...
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
Rolling resistance
Rolling resistance, sometimes called rolling friction or rolling drag, is the resistance that occurs when a round object such as a ball or tire rolls on a flat surface, in steady velocity straight line motion. It is caused mainly by the deformation of the object, the deformation of the surface, or...
. 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
Rotational energy
The rotational energy or angular kinetic energy is the kinetic energy due to the rotation of an object and is part of its total kinetic energy...
stored in the wheels. The pinewood derby car converts gravitational potential energy
Potential energy
In physics, potential energy is the energy stored in a body or in a system due to its position in a force field or due to its configuration. The SI unit of measure for energy and work is the Joule...
into translational kinetic energy
Kinetic energy
The kinetic energy of an object is the energy which it possesses due to its motion.It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes...
(speed) plus rotational energy. Heavier wheels have a greater moment of inertia
Moment of inertia
In classical mechanics, moment of inertia, also called mass moment of inertia, rotational inertia, polar moment of inertia of mass, or the angular mass, is a measure of an object's resistance to changes to its rotation. It is the inertia of a rotating body with respect to its rotation...
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.
Another consideration is the track itself. A track that is mostly sloped, with little flat at the end, can really allow cars with minimal mass in their wheels to shine. However, a track with a steep slope and then a long flat section can penalize such cars due to the quick loss of energy they experience once they have reached the bottom, when all potential energy has been transferred to kinetic and rotational energy. Such cars will take a lead on the downslope, but may be passed by cars with more energy "stored" away as rotational energy on the flat.
A proper lubricant, typically graphite
Graphite
The mineral graphite is one of the allotropes of carbon. It was named by Abraham Gottlob Werner in 1789 from the Ancient Greek γράφω , "to draw/write", for its use in pencils, where it is commonly called lead . Unlike diamond , graphite is an electrical conductor, a semimetal...
powder, is essential. Wheel alignment
Wheel alignment
Wheel alignment sometimes referred to as tracking, is part of standard automobile maintenance that consists of adjusting the angles of the wheels so that they are set to the car maker's specification. The purpose of these adjustments is to reduce tire wear, and to ensure that vehicle travel is...
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
Center of mass
In physics, the center of mass or barycenter of a system is the average location of all of its mass. In the case of a rigid body, the position of the center of mass is fixed in relation to the body...
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.
External links
- How to Conduct a Pinewood Derby, an official training guide from BSA
- Pinewood Derby, from the U.S. Scouting Service ProjectU.S. Scouting Service ProjectThe U.S. Scouting Service Project is one of the largest online collections of Scouting resource and reference materials. USSSP is organized as a non-profit corporation founded in 1998 named "The U.S. Scouting Service Project, Inc." and is maintained by volunteer Scouters...