Monday, January 28, 2008

Transmission


Transmission in automotive is a device for transmitting power from the engine to the drive shaft, from which it is eventually carried to the wheels. The device must convert the power from the relatively fixed high angular velocity and low torque (turning force) of the engine crankshaft to the variable, usually lower speeds and higher torques needed at the wheels. The crankshaft is the part of the engine that converts the back-and-forth (reciprocating) motion of the engine piston into rotary motion.

Generally, car transmission converts the engine power by means of a system of gears, providing a variety of gear ratios between the engine and the wheels. When the vehicle is starting from rest, the transmission is placed in first, or low, gear in order to produce a high torque at a low wheel speed. As the car speeds up, the driver shifts or the automatic transmission is shifted into a higher gear. With each higher gear, the drive shaft turn faster but with less power and torque. As an example, consider a simple three-speed transmission. When the car starts from the rest in first gear, the gear ratio might be 3 to 1, this means that the crankshaft turn three times to turn the drive shaft once. After the car gains some speed, the transmission is shifted into the second gear, with a gear ratio say, 2 : 1. After a further increase in wheel speed, a shift is made into high, or third, gear. This is also called direct drive, because there is no gear reduction in the turn at the same speed as the crankshaft.

The next article about the two basic type of transmission are the manual type and the automatic transmission pada speed transmission.

1. Input shaft from engine
2. Layshaft
3. Idler
4. Output shaft
5. Gearshift lever, locks a gear wheel on the output shaft into place

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