Conventional Automobile Gear Box:

A conventional gear box of an automobile uses compound gear train. For different gear engagement, it might use sliding mesh arrangement, constant mesh arrangement or synchromesh arrangement. We might restrict ourselves to the gear train. It can be clarify better with the help of an example.

A sliding mesh type gear box having four forward speeds has following gear ratios:

Top gear = 1

Third gear = 1.38

Second gear = 2.24

First gear = 4

Reverse gear = 4.2

Estimate number of teeth on several gears. The minimum number of teeth on the pinion must not be less than 18. The gear box must have minimum size and variation in the ratios must be as small as possible.