Differential (mechanical device): Difference between revisions

{{Use dmy dates|date=AprilJuly 2024}}

[[File:ChartDriveDetail.JPG|thumb|upright|Planetary differential used to drive a [[chart recorder]] {{ca|c. 1961}}. The motors drive the Sun and annular gears, while the output is taken from the planet gear carrier. This gives 3 different speeds depending on which motors are on.]]

Non-automotive uses of differentials include performing [[Analog signal|analogue]] [[arithmetic]]. Two of the differential's three shafts are made to rotate through angles that represent (are proportional to) two numbers, and the angle of the third shaft's rotation represents the sum or difference of the two input numbers. The earliest known use of a differential gear is in the Antikythera mechanism, c. 80&nbsp;BCE, which used a differential gear to control a small sphere representing the Moon from the difference between the Sun and Moon position pointers. The ball was painted black and white in hemispheres, and graphically showed the phase of the Moon at a particular point in time.<ref name="Wright-Reconsidered" /> An [[equation clock]] that used a differential for addition was made in 1720. In the 20th century, large assemblies of many differentials were used as [[Analog computer|analogue computers]], calculating, for example, the direction in which a gun should be aimed.<ref>{{cite AV media |title=Basic Mechanisms in Fire Control Computers, Part 1, Shafts Gears Cams and Differentials, posted as 'U.S. Navy Vintage Fire Control Computers' |medium=Training Film |url=https://www.youtube.com/watch?v=mQhmmTX5f9Y&list=PLF1A5EC36E8EDF711 |archive-url=https://ghostarchive.org/varchive/youtube/20211118/mQhmmTX5f9Y| archive-date=18 November 2021 |url-status=live |date=1953 |access-date=20 September 2021 |time=37 seconds |publisher=U.S. Navy |id=MN-6783a |access-date=20 September 2021 }}{{cbignore}}</ref>