Differential (mechanical device)

A common use of differentials is in motor vehicles, to allow the wheels at each end of a drive axle to rotate at different speeds while cornering.

However, for improved cornering abilities, many vehicles use a differential, which allows the two wheels to rotate at different speeds.

The functions of this design are to change the axis of rotation by 90 degrees (from the propshaft to the half-shafts) and provide a reduction in the gear ratio.

[citation needed] An advantage of the epicyclic design is its relatively compact width (when viewed along the axis of its input shaft).

[citation needed] A spur-gear differential has equal-sized spur gears at each end, each of which is connected to an output shaft.

The pinion pairs only mesh for the part of their length between the two spur gears, and rotate in opposite directions.

Uses of spur-gear differentials include the Oldsmobile Toronado American front-wheel drive car.

An undesirable side-effect of a regular ("open") differential is that it can send most of the power to the wheel with the lesser traction (grip).

[11] In order to avoid this situation, various designs of limited-slip differentials are used to limit the difference in power sent to each of the wheels.

The ball was painted black and white in hemispheres, and graphically showed the phase of the Moon at a particular point in time.

In the 20th century, large assemblies of many differentials were used as analogue computers, calculating, for example, the direction in which a gun should be aimed.

It is widely thought that a differential mechanism responded to any difference between the speeds of rotation of the two wheels of the chariot, and turned the pointer appropriately.