On the outside, tether cars look a lot like the vehicles that break land-speed records. The cars are narrow and most of the engine parts are enclosed inside the body of the racer. They're comprised of parts similar to a full-size car, including a combustion engine, exhaust pipe, air intake, flywheel, gearbox, driveshaft and wheels. The racers also have a tailskid, located in the back that stabilizes the vehicles at top speeds. The cars are typically about one to two feet (30.5 to 61 centimeters) long, and weigh anywhere from two to six pounds (0.9 to 2.7 kilograms).
In the international competitions, there are five different engine sizes that compete. The smallest is the 1.5 cubic centimeter (cc) engine, which has a top speed over 65 miles per hour (104.6 kilometers per hour). The other engine sizes are the 2.5cc, 3.5cc, 5cc and 10cc classes. The 10cc engine class cars are capable of producing speeds over 200 miles per hour (321.9 kilometers per hour) [source: Macropoulos]. These two-cylinder engines typically run on a fuel mixture of 80 percent methanol and 20 percent castor oil and are capable of producing engine speeds up to 45,000 revolutions per minute.
Drivers can spend hours modifying the cars to squeeze just a little more speed -- perhaps a half a mile per hour more -- out of the engines. In fact, making adjustments and changes to the engine are a huge part of the hobby. One of the main components contributing to the car's speed is the tuning pipe. The tuning pipe not only acts as the exhaust pipe, but it also helps to propel the car. The pipe's design sucks out any unspent fuel in the engine, shoots it to the back of the pipe where it becomes vaporized, and then forces part of it back into the engine. The vaporized fuel gives more power to the engine and helps it reach its top speed, but this effect only kicks in after the car reaches 100 miles per hour (160.9 kilometers per hour).
With cars regularly achieving speeds well over 100 miles per hour (160.9 kilometers per hour), the tracks they race on have to be specially built to accommodate the tether cars and protect the people watching the races. Go on to the next page to learn about tether car races.