A gravity racer is a non-motor vehicle driven on a sloping road – either against the clock or against a competitor. It is usually made of wood. Mostly, it is built for recreation.
Propelled by gravity, the vehicle can achieve speeds over 70 miles per hour. To steer the vehicle, one must use both feet and hands simultaneously. A gravity racer derives its energy entirely from the force of gravity (minus starting push) – that is in effect equal for any combination of course and racer design. However, performance could be greatly influenced by the combined impact of different forms of drag, moment of inertia of the wheels, and the driver’s skill in choosing optimal lines.
Originally, gravity racer cars were built from roller-skate wheels & wooden soap/apple crates, but over time, they have grown more sophisticated with materials like fibreglass, aluminium, etc.
An Interesting DIY Activity
Building a gravity racer is an interesting and fairly simple task, provided all the materials needed are available. Wooden plank/sheet timber, hammer, split pin, screwdriver, brakes (bike brakes could be used), trolley wheels, ropes, wood screws, drill and electric jigsaw are the basic requirements. Once all the materials are gathered, you can start building the racer.
The following are the steps to be followed:
- cutting the chassis plank to its optimal size
- clipping the axle planks to the requisite length
- making the pivot
- binding the rear/back side axle planks
- placing/fastening the driver seat
- building the steering, &
- sliding the wheels onto the axles and securing them
One could find a detailed pictorial description of the same on http://www.wikihow.com/Make-a-Gravity-Racer#Design_It_Yourself.2C_For_Fun_sub.
Generally, wooden gravity racers are for kids’ recreational purposes and are a fun sport. The racers are, therefore, made of wood to render them a lightweight body, which helps kids easily manoeuvre the vehicle. Even otherwise, if it was meant for adults, wood is still preferred over steel. Metal is typically used within competitive circuits.
Driven by Competitive Spirit
Though majorly a popular hobby among kids, there are proper competitions and races called soapbox/billycart derby conducted. However, these events are usually fun contests and cannot be viewed as regular sporting events. Usually, such racing tournaments are a part of fund-raisers or conducted for charitable reasons. Many such events impose certain rules that need to be kept in mind while building the gravity racer, so that the machine serves the purpose.
These rules are:
- There must be no motor in the car
- The car must have 4 wheels at least
- Some types of brakes must be in use
- A helmet is a must for the driver
- For speed, a push at the top is allowed
Gravity racers weigh 150 pounds on an average and attain top speeds of in the 20-30 mph range. Many cities have dedicated tracks where people compete for prizes. Gravity racer carts are unpowered. Whether running down a suitable slope or pushed by willing helpers, skill has a major role to play in the race’s outcome.