Philon of Byzantium was one of the first who used gears in water raising devices. He said that the direction of rotation is reversed when one gear wheel drives another gear wheel. Aristotle mentions gears around 330 BC, (wheel drives in windlasses). Its time of construction is now estimated between 150 and 100 BC. The earliest preserved gears in Europe were found in the Antikythera mechanism an example of a very early and intricate geared device, designed to calculate astronomical positions. The earliest examples of gears date from the 4th century BC in China (Zhan Guo times – Late East Zhou dynasty), which have been preserved at the Luoyang Museum of Henan Province, China. ![]() įurthermore, a gear can mesh with a linear toothed part, called a rack, producing movement in a straight line instead of rotation (movement in a circle). Sometimes a CVT is referred to as an "infinitely variable transmission". 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 (CVT). In transmissions with multiple gear ratios-such as bicycles, motorcycles, and cars-the term "gear" (e.g.,e "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 diameters of the gears are measured at a point between the root and tips of the gear teeth called the pitch circle.Ī gear may also be known informally as a cog. The ratio of the output rotational speed to the input rotational speed is equal to the inverse of the ratio of the diameter of the output gear to that of the input gear ω out⁄ ω in = ( dia out⁄ dia in) -1 = dia in⁄ dia out. The ratio of the output torque to the input torque is equal to the ratio of the diameter of the output gear to that of the input gear τ out⁄ τ in = dia out⁄ dia in. Meshing gears of different diameters produce three changes - (i) a change in torque, creating a mechanical advantage, (ii) an inverse change in rotational speed and (iii) a change in the sense of the rotation, a clockwise rotation becoming an anti-clockwise one and vice-versa. The basic principle behind the operation of gears is analogous to the basic principle of levers. The teeth on the two meshing gears all have the same shape. While doing so, they can change the torque and rotational speed being transmitted (in inverse proportion) and also change the rotational axis of the power being transmitted. ![]() Two intermeshing spur gears rotating at different velocity due to differing gear ratioĪ 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 rotational power. For other uses, see Cogwheel (disambiguation). ![]() For the video game, see Geared (video game).
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