Why Does Cars Have Gearbox?

Topics: Manual transmission, Gear ratio, Torque Pages: 3 (949 words) Published: November 30, 2011
Why do many cars have a gearbox?
Gearbox is an enclosed system of assembled gears that transmits mechanical energy from a prime mover to an output device. A gearbox can also change the speed, direction, or torque of mechanical energy.[1] Gearbox was invented in the 19th century and it is still being widely used today. In the early age and in some part of the world, gearbox is also known as transmission. Merriam-Webster defines transmission as: an assembly of parts including the speed-changing gears and the propeller shaft by which the power is transmitted from an engine to a live axle. In other words, transmission refers to the gearbox that uses gears and gear trains to provide speed and torque conversions from a rotating power source to another device [2]. A car transmission has a number of gears that can be put together in different combinations, to create different gear ratios; or even to change the direction of rotation so the wheels can go in reverse, although the motor keeps turning the same way. Why does a car need a gearbox?

From the fundamental of an engine, it is known that the pistons drive the main crank in the engine so that it spins. Idling, it spins around 900rpm (revolution per minute) and when the foot is pressed on the gas at maximum, it can reach 7,500rpm or even higher in certain cars. It is unrealistic to connect a set of wheels to the end of the crank because the speed is too high and too variable, and the user will have to stall the engine every time to stand still which is quite a difficult task. Gears are circular and have a form like ‘teeth’ which interlock with another gear to transmit power to and from the other gear. When two gears are meshed, one will be getting power from another source and transmitting it to the other gear. The ‘altered’ power will be available at the 2nd gear. Now when the two gears are meshed, one would be smaller in size and other one larger. If the larger gear often called helical gear gets...
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