Gravity racer

A gravity racer or soapbox is a motorless vehicle which is raced on a downhill road either against the clock or against another competitor. Although most are built for the purpose of recreation, some gravity racing teams take the sport more seriously and compete to win. They are propelled by gravity and can achieve speeds upwards of 112 km/h (70 miles per hour).

Originally, gravity racer cars were built from wooden soap (or apple) crates and rollerskate wheels, but have grown more sophisticated over time, with materials like aluminium, fiberglass and even CFRP being used.

In the United Kingdom a gravity racer car has been called a buggy, trolley, cart. It is currently popularly called a soapbox. 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 Australia they are called billy-carts.

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 are usually entered into in a spirit of fun rather than serious competition. Often they will be fund-raisers for charity. Many, but not all, events impose the following rules:

Soapbox cars weigh an average of 150 pounds (68 kg) and reach top speeds of 20 to 30 mph (30 to 50 km/h). Many cities have permanent tracks where drivers compete for prizes.

A typical Gravity racer cart is usually made of steel, and has 4 wheels, arranged as a fixed rear axle, and a steerable front beam axle - usually with a very simple single central . 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 bicycles 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).

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