A gear, or gearwheel, is a rotating machine part with teeth that mesh with another toothed part to transmit rotational motion and torque between shafts. Gears were developed independently in more than one ancient civilization rather than by a single inventor: the earliest surviving physical gears come from Warring States-period China in the 4th century BC, while in Greece Aristotle described geared windlasses around 330 BC and the sophisticated Antikythera mechanism used gearing to calculate astronomical positions in the 2nd or 1st century BC. Centuries later the Chinese engineer Ma Jun used differential gearing in a south-pointing chariot, showing the technology continued to develop independently in East Asia as well.
Facts
YearSourced to the subject's own accountEarliest surviving physical gears are from 4th-century BC China (Warring States period), preserved at the Luoyang Museum in Henan Province; Aristotle independently describes toothed gearing in windlasses in Greece around 330 BC. SignificanceSourced to the subject's own accountConverts torque and rotational speed between shafts of different sizes, the founding mechanism behind clocks, mills, vehicle transmissions and almost all later machinery. 1 Gear
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1. Gear (Wikipedia)
WikipediaHistory section, ancient-Greece paragraph, Wikipedia article Gear
Aristotle mentions gears around 330 BC, as wheel drives in windlasses.
opening description, Wikipedia article Gear
Most commonly, gears and gear trains can be used to trade torque for rotational speed between two axles or other rotating parts or to change the axis of rotation or to invert the sense of rotation.
Associated With: Gearbox, Introductory section, transmission paragraph
Most vehicles have a transmission or "gearbox" containing a set of gears that can be meshed in multiple configurations.
Associated With: Windmill, Materials section, image caption
Wooden gears of a historic windmill
Associated With: South-Pointing Chariot, History section, Ma Jun south-pointing chariot sentence
The Chinese engineer Ma Jun (c. 200-265) described a south-pointing chariot. A set of differential gears connected to the wheels and to a pointer on top of the chariot kept the direction of the latter unchanged as the chariot turned.
Associated With: The Wheel, Lead section, opening definition sentence
A gear or gearwheel, also called a toothed wheel, or cog is a rotating machine part typically used to transmit rotational motion or torque by means of a series of teeth that engage with compatible teeth of another gear or other part.
In Field: Mechanical Engineering, Categories
Gears
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Wikipedia contributors, Wikimedia FoundationAssociated With: The Wheel, History section, technological applications sentenceQuote, Associated With: The Wheel, History section, technological applications sentence
The invention of the wheel has also been important for technology in general, important applications including the water wheel, the cogwheel (see also antikythera mechanism), the spinning wheel, and the astrolabe or torquetum.
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