Soapbox (car) - AbsoluteAstronomy.com

A gravity racer is a motorless vehicle capable of holding a driver (usually a child) built for the purpose of racing or recreation. They are propelled by gravity and can achieve speeds upwards of 112 km/h (70 miles per hour).

Soapbox cars

Originally, soapbox cars were built from wooden soap (or orange) crates and rollerskate wheels, but have grown more sophisticated over time, with materials like aluminum, fiberglass

Fiberglass

Glass fiber is a material consisting of numerous extremely fine fibers of glass.Glassmakers throughout history have experimented with glass fibers, but mass manufacture of glass fiber was only made possible with the invention of finer machine tooling...

and even CFRP being utilized.

In the United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

a soapbox car has been called a buggy, trolley, cart. It is currently popularly called a go-cart, although that now more often refers to a similar vehicle with a motor

Kart racing

Kart racing or karting is a variant of open-wheel motorsport with small, open, four-wheeled vehicles called karts, go-karts, or gearbox/shifter karts depending on the design. They are usually raced on scaled-down circuits...

, spelt "go kart". In Scotland and northern England it has also been called a bogie, cartie/cairtie, guider or piler. In Wales it is often referred to as a gambo.

In addition to being built by children, there are organised competitions and races ("soapbox or billycart derby") that often engage the enthusiasm of adults. However, these things are usually entered into in a spirit of fun rather than serious competition. Often they will be fund-raisers for charity

Charitable organization

A charitable organization is a type of non-profit organization . It differs from other types of NPOs in that it centers on philanthropic goals A charitable organization is a type of non-profit organization (NPO). It differs from other types of NPOs in that it centers on philanthropic goals A...

. Many, but not all, events impose the following rules:

The car must have no motor
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...
The car must have at least 4 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
The car may have to have some type of brake
Brake
A brake is a mechanical device which inhibits motion. Its opposite component is a clutch. The rest of this article is dedicated to various types of vehicular brakes....

s
The driver must wear a helmet
Helmet
A helmet is a form of protective gear worn on the head to protect it from injuries.Ceremonial or symbolic helmets without protective function are sometimes used. The oldest known use of helmets was by Assyrian soldiers in 900BC, who wore thick leather or bronze helmets to protect the head from...
A push at the top is allowed for extra speed

Soapbox cars weigh an average of 150 pounds (68 kg) and reach top speeds of 20 to 30 mph (32.2 to 48.3 km/h). Many cities have permanent tracks where drivers compete for prizes.

Construction

A typical soap-box cart is usually made of steel

Steel

Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

, and has 4 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, arranged as a fixed rear axle

Axle

An axle is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to its surroundings, with the wheels rotating around the axle. In the former case, bearings or bushings are provided at the mounting points where the axle...

, and a steerable front beam axle - usually with a very simple single central pivot. A seat is arranged at the back, and perhaps the seat area is enclosed, as in the original soap-box design. More sophisticated designs might employ a fully enclosed body. The types of wheels employed vary according to what can be obtained easily - wheels from baby carriages, pushchairs, prams, and discarded bicycle

Bicycle

A bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....

s being common. Ready-made wheels are also available from hardware suppliers. Steering is typically actuated using a rope connected to the ends of the steerable beam (which can then double as a useful manual pulling device).

More sophisticated steering methods are sometimes seen. Brake

Brake

A brake is a mechanical device which inhibits motion. Its opposite component is a clutch. The rest of this article is dedicated to various types of vehicular brakes....

s are also not commonly used, though some soap-box cart racing contests require these. Often a simple friction brake operated by a lever which bears on one of the tires, which will be of dubious effectiveness, is all that is required under the rules.

Soapbox carts are unpowered, and are either pushed by willing helpers, or are run down a suitable slope. Races will usually take place downhill and the most efficient and skillfully driven cart will win - gravity applying equally to all.

Soap-box carts also make great construction projects for children, requiring only an intuitive sense of engineering

Engineering

Engineering is the discipline, art, skill and profession of acquiring and applying scientific, mathematical, economic, social, and practical knowledge, in order to design and build structures, machines, devices, systems, materials and processes that safely realize improvements to the lives of...

, and a few basic construction skills. There are also predesigned kits available, though for many this defeats the purpose of the exercise.

Recently, more advanced soapboxes are beginning to emerge. These, intended for competition in the major soapbox races, are sometimes made of carbon fibre and feature a monocoque

Monocoque

Monocoque is a construction technique that supports structural load by using an object's external skin, as opposed to using an internal frame or truss that is then covered with a non-load-bearing skin or coachwork...

design, although most use a more traditional chassis

Chassis

A chassis consists of an internal framework that supports a man-made object. It is analogous to an animal's skeleton. An example of a chassis is the underpart of a motor vehicle, consisting of the frame with the wheels and machinery.- Vehicles :In the case of vehicles, the term chassis means the...

or spaceframe design with bodywork made from materials such as plywood

Plywood

Plywood is a type of manufactured timber made from thin sheets of wood veneer. It is one of the most widely used wood products. It is flexible, inexpensive, workable, re-usable, and can usually be locally manufactured...

, corrugated plastic

Corrugated plastic

Corrugated plastic or corriboard - also known under the tradenames of Coroplast, IntePro, Correx, Twinplast, Corriflute or Corflute - refers to a wide range of extruded twinwall plastic-sheet products produced from high-impact polypropylene resin with a similar make-up to corrugated fiberboard. It...

or similar. Examples of such soapboxes include the Lotus 119c and the Formula Gravity VXR Nimbus..

In Australia billy carts tend to conform, even in the 21st century, to a more traditional or rudimentary specification often being constructed informally by juveniles from found or inexpensive materials with minimal adult input and used without safety equipment. However even when construction of vehicles is more formally organised, such as for the annual Blacktown and District Cub Scout Billy Cart Derby at Rooty Hill, NSW

Rooty Hill, New South Wales

Rooty Hill is a suburb of Sydney, in the state of New South Wales, Australia. Rooty Hill is located 42 kilometres west of the Sydney central business district, in the local government area of the City of Blacktown and is part of the Greater Western Sydney region.-History:Rooty Hill was named after...

the vehicle is still constructed to a deliberately relatively unsophisticated design, although safety is a consideration.

In Indonesia, billy carts are also known as 'gokar'. They are raced in different regions as a community social activity. The form of the cart is similar to the Australian one however the wheels are often motor cycle wheel bearings.

Electric soapboxes are a new development and are in fact not soapboxes at all. This, as they are electrically powered.

History of soapbox races

In 1933, Dayton Daily News newspaper photographer Myron Scott

Myron Scott

Myron E. Scott was the creator of the All-American Soap Box Derby. He is also credited with naming Chevrolet's sports car, the Corvette. Scott was born in Camden, Ohio...

of Dayton

Dayton, Ohio

Dayton is the 6th largest city in the U.S. state of Ohio and the county seat of Montgomery County, the fifth most populous county in the state. The population was 141,527 at the 2010 census. The Dayton Metropolitan Statistical Area had a population of 841,502 in the 2010 census...

, Ohio

Ohio

Ohio is a Midwestern state in the United States. The 34th largest state by area in the U.S.,it is the 7th‑most populous with over 11.5 million residents, containing several major American cities and seven metropolitan areas with populations of 500,000 or more.The state's capital is Columbus...

had covered a race of boy-built cars in his home community and was so taken with the idea that he acquired rights to the event; the national-scale 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...

grew out of this idea. In 1934, Scott had managed to persuade fifty cities across the United States to hold soap box car races and send a champion each to Dayton for a major race, later held in Akron

Akron, Ohio

Akron , is the fifth largest city in the U.S. state of Ohio and the county seat of Summit County. It is located in the Great Lakes region approximately south of Lake Erie along the Little Cuyahoga River. As of the 2010 census, the city had a population of 199,110. The Akron Metropolitan...

. Scott later went on to work for Chevrolet

Chevrolet

Chevrolet , also known as Chevy , is a brand of vehicle produced by General Motors Company . Founded by Louis Chevrolet and ousted GM founder William C. Durant on November 3, 1911, General Motors acquired Chevrolet in 1918...

.

In the UK, soap box derbies have recently become more popular, brought to the masses by large events such as the Red Bull

Red Bull

Red Bull is an energy drink sold by the Austrian Red Bull GmbH, created in 1987 by the Austrian entrepreneur Dietrich Mateschitz. In terms of market share, Red Bull is the most popular energy drink in the world, with 3 billion cans sold each year. Dietrich Mateschitz was inspired by an already...

race and that held between 2000 and 2004 at the Goodwood Festival of Speed

Goodwood Festival of Speed

The Goodwood Festival of Speed, commonly abbreviated as FoS and referred within the United Kingdom as simply the Festival of Speed, is an annual hill climb featuring historic motor racing vehicles that is held in the grounds of Goodwood House, West Sussex, England.Typically held in late June or...

. Now, many small hilly communities organize their own races, such as the Catterline Cartie Challenge

Catterline Cartie Challenge

The Catterline Cartie Challenge is a competition for home made soapbox carts held annually in Catterline, near Stonehaven, Scotland...

in Scotland and the Belchford Downhill Challenge in Lincolnshire.

Physics considerations

A gravity racer obtains its energy solely from the force of gravity (assuming no starting push is permitted), which is effectively equal for any combination of racer design and course. However, performance can be greatly affected by the combined effects of various forms of drag and also the 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...

of the wheels, and also of course by the skill of the driver in choosing optimal lines. Drag breaks down into aerodynamic drag and 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...

. The latter can be minimised by careful attention to the wheel bearing

Bearing (mechanical)

A bearing is a device to allow constrained relative motion between two or more parts, typically rotation or linear movement. Bearings may be classified broadly according to the motions they allow and according to their principle of operation as well as by the directions of applied loads they can...

s, tyre sizes and pressures, and brakes (to avoid parasitic brake drag). High tyre pressures and narrower tyres will typically lower the tyre contact rolling resistance, usually at the expense of grip. Larger wheels have lower rolling resistance than small ones, and rolling resistance is also proportional to overall weight. If permitted, a 3-wheeler design will have 25% less rotational inertia than a 4-wheeler, all else being equal. Aerodynamic drag can be minimised by designing a fully enclosed body that reduces the drag coefficient

Drag coefficient

In fluid dynamics, the drag coefficient is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment such as air or water. It is used in the drag equation, where a lower drag coefficient indicates the object will have less aerodynamic or...

, but given that this can be a highly technical thing to achieve especially for the amateur builder, and given that some aerodynamic drag is inevitable, a heavier cart will always do better than a lighter one with the same drag coefficient - its terminal velocity

Terminal velocity

In fluid dynamics an object is moving at its terminal velocity if its speed is constant due to the restraining force exerted by the fluid through which it is moving....

will be higher. For this reason there are usually class weight limits in most controlled forms of the sport. Since some of 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...

due to gravity must be converted to the 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...

of the rotating wheels, a vehicle with lighter wheels will accelerate faster than one with heavier wheels. If a race is started on some form of ramp, having a tail-heavy car can also improve final acceleration, as the effective height of the centre of gravity of the vehicle is raised.

External links

"The Object at Hand," Smithsonian Magazine, May 1995

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Soapbox cars

Construction

History of soapbox races

Physics considerations

See also

External links