1206 CE: Al-Jazari invented the segmental gear as part of a water-lifting device. 1221 CE The geared astrolabe was built in Isfahan showing the position of the moon in the zodiac and its phase, and the number of days since new moon. 13th–14th centuries: The worm gear was invented as part of a roller cotton gin in the Indian subcontinent. 1386 CE: The Salisbury Cathedral clock: it is the world's oldest still working geared mechanical clock.Differential gears may have been used in some of the Chinese south-pointing chariots, but the first verifiable use of differential gears was by the British clock maker Joseph Williamson in 1720.Įxamples of early gear applications include: The worm gear was invented in the Indian subcontinent, for use in roller cotton gins, some time during the 13th–14th centuries. The segmental gear, which receives/communicates reciprocating motion from/to a cogwheel, consisting of a sector of a circular gear/ring having cogs on the periphery, was invented by Arab engineer Al-Jazari in 1206.
įurthermore, a gear can mesh with a linear toothed part, called a rack, producing translation instead of rotation. The term describes similar devices, even when the gear ratio is continuous rather than discrete, or when the device does not actually contain gears, as in a continuously variable transmission. In transmissions with multiple gear ratios-such as bicycles, motorcycles, and cars-the term "gear" (e.g., "first gear") refers to a gear ratio rather than an actual physical gear. An advantage of gears is that the teeth of a gear prevent slippage. The gears in a transmission are analogous to the wheels in a crossed, belt pulley system. Two or more meshing gears, working in a sequence, are called a gear train or a transmission. The teeth on the two meshing gears all have the same shape. The rotational speeds, and the torques, of two meshing gears differ in proportion to their diameters. Gears of different sizes produce a change in torque, creating a mechanical advantage, through their gear ratio, and thus may be considered a simple machine.
Geared devices can change the speed, torque, and direction of a power source. A gear may also be known informally as a cog. The basic principle behind the operation of gears is analogous to the basic principle of levers. Oil mill in Storkensohn ( Haut-Rhin), France.Ī gear is a rotating circular machine part having cut teeth or, in the case of a cogwheel or gearwheel, inserted teeth (called cogs), which mesh with another (compatible) toothed part to transmit (convert) torque and speed. Cast iron mortise wheel with wooden cogs (powered by an external water wheel) meshing with a cast iron gear wheel, connected to a pulley with drive belt.
0 kommentar(er)
