Explain the construction, working and application of overdrive.

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written 8.3 years ago by

teamques10 ★ 67k

An overdrive is a mechanism that allows an automobile to cruise at sustained speed with reduced engine RPM, leading to better fuel economy, lower noise, and lower wear.
It is mounted at the rear end of the gearbox.
The gear ratio provided by an overdrive unit is 30% more than the direct top gear.
The unit consists of an epicyclic gear train.
The planet carrier is connected to the output shaft of the gear box.
When the sun gear is locked to the output shaft of the gear box, the planet carrier rotates about the sun gear.
The ring gear rotates more slowly than planet gear thus giving more ratio than the direct drive.
Overdrive is used in some sports cars and luxury cars.

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