History
There are many claims to the invention of the differential gear but it is possible that it was known, at least in some places, in ancient times. Some historical milestones of the differential include:
- 1050 BC–771 BC: The Book of Song (which itself was written between 502 and 557 A.D.) makes the assertion that the South Pointing Chariot, which may have used a differential gear, was invented during the Western Zhou Dynasty in China.
- 150 - 100 BC: Hypothesized use, now discredited, in the Greek Antikythera mechanism
- 30 BC - 20 BC: Differential gear systems possibly used in China
- 227–239 AD: Despite doubts from fellow ministers at court, Ma Jun from the Kingdom of Wei in China invents the first historically verifiable South Pointing Chariot, which provided cardinal direction as a non-magnetic, mechanized compass. Some such chariots may have used differential gears.
- 658, 666 AD: two Chinese Buddhist monks and engineers create South Pointing Chariots for Emperor Tenji of Japan.
- 1027, 1107 AD: Documented Chinese reproductions of the South Pointing Chariot by Yan Su and then Wu Deren, which described in detail the mechanical functions and gear ratios of the device much more so than earlier Chinese records.
- 1720: Joseph Williamson uses a differential gear in a clock.
- 1810: Rudolph Ackermann of Germany invents a four-wheel steering system for carriages, which some later writers mistakenly report as a differential.
- 1827: modern automotive differential patented by watchmaker Onésiphore Pecqueur (1792–1852) of the Conservatoire des Arts et Métiers in France for use on a steam cart. (Sources: Britannica Online and)
- 1832: Richard Roberts of England patents 'gear of compensation', a differential for road locomotives.
- 1874: Aveling and Porter of Rochester, Kent list a crane locomotive in their catalogue fitted with their patent differential gear on the rear axle.
- 1876: James Starley of Coventry invents chain-drive differential for use on bicycles; invention later used on automobiles by Karl Benz.
- 1897: first use of differential on an Australian steam car by David Shearer.
- 1958: Vernon Gleasman patents the Torsen dual-drive differential, a type of limited slip differential that relies solely on the action of gearing instead of a combination of clutches and gears.
Note: The Antikythera mechanism (150 BC–100 BC), discovered on an ancient shipwreck near the Greek island of Antikythera, was once suggested to have employed a differential gear. This has since been disproved. Other possible uses of differentials prior to Joseph Williamson's clock of 1720 are hypothetical.
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