Accelerator The pedal at a driver’s feet that adjusts a car’s speed by controlling the amount of fuel that enters the engine. Also called the gas pedal. Alternator A device powered by a car’s engine, that produces electrical power for the car. Axle The bar or shaft on which the wheels of a car revolve. Battery The power source that enables a car to start. The battery contains plates of lead immersed in acid and produces the strong current needed to turn the starter motor. Camshaft A rotating device in a car’s engine that opens and closes its valves, letting air and fuel in and exhaust gases out. Chassis The structural framework of a car, to which other parts, such as the engine and wheel axle, are attached. Crankshaft A device that turns the up-and-down movement of pistons into rotating motion. Via the gears, this motion turns the wheels of the car. Cylinder The engine part inside which the pistons move up and down. The more cylinders there are inside a car’s engine, the more power the car has. Dashboard A panel in front of the driver’s seat with dials that show fuel levels and speed as well as controls for headlights, heating and windscreen wipers. Disc brakes A combination of pads and discs on the inside of a car’s wheels. When the driver pushes the brake pedal, the pads grip the discs, slowing the wheels down. The force of the driver’s foot increases pressure on fluid inside the brake cylinders which, in turn, forces pistons to push the brake pads against the disc. Drive shaft A spinning shaft, connected to the crankshaft in an internal combustion engine, that drives another part of the vehicle. This includes the wheels of a car, but also the propeller of a ship or the caterpillar tracks of a bulldozer. Drum brakes A system in which pads, called “shoes”, are pushed against a drum in a car’s wheel to slow it down. Drum brakes are used on the rear wheels of older cars and on all hand brakes. Exhaust Waste gases produced by an engine. An exhaust pipe takes fumes away from the engine and out of the car. Four-wheel drive In a four-wheel drive (4WD) vehicle, all four wheels are driven directly by the engine. A long drive shaft connects the rear wheels to the engine, while a device called a differential makes the two rear wheels turn at different speeds when going round corners (the outer one turns faster). Gears A set of cogs that links the engine to the wheels. In a low gear, the wheels turn much slower than the crankshaft. Low gears allow the engine to turn at high speed, even though the wheels are turning at low speed. To change gear, the driver first pushes the clutch, which disconnects the gears from the engine, before moving the gear stick. Hand brake A lever that operates the rear brakes, used when a car is stationary. Internal combustion engine An engine that converts energy from fuel into movement. Fuel and air are ignited inside cylinders, causing repeated explosions that drive pistons. The pistons turn the crankshaft, which powers the wheels. Most engines work on a four-stroke cycle. Pedals A set of pedals at a driver’s feet, pressed in order to change gear (clutch), brake (brake), or accelerate (accelerator or gas pedal). Radiator A device that keeps a car’s engine cool. Water is pumped around channels where it is heated by the engine. The hot water then carries heat from the engine to the radiator, where it is lost to the air. Spark plug An electrical device that ignites the fuel inside the cylinders of an engine. Steering wheel A wheel used to steer a car. It is connected to the wheels by a column attached to a rack and pinion. The pinion (a cog) connects with the rack (a toothed bar) shifting it left or right. Suspension A system of springs and shock absorbers attached to the wheels to ensure a car rolls smoothly. Springs take the force of jolts, while shock absorbers dampen the movement of the springs. Tyre A covering around a wheel made of cords and wires encased in rubber, and filled with compressed air.