gear (redirected from moving up a gear)

gear, toothed wheel, cylinder, or cone that transmits motion from one part of a machine to another; it is one of the oldest means of transmitting motion. When the teeth of two gears are meshed, turning one gear will cause the other to rotate. In most cases both gears are mounted on shafts so that when one shaft turns, the other also rotates. By meshing two gears of different diameters, a variation in both speed and torque between the two shafts is obtained; the smaller gear in this case is called the pinion. A spur gear consists of a wheel with straight teeth mounted radially either on the inner circumference (internal spur gear) or outer circumference (external spur gear) of the wheel. Two meshed spur gears are used to transmit motion between parallel shafts. A rack and pinion consists of a pinion engaging and transferring motion to or from a special kind of spur gear, called a rack, consisting of a series of teeth in a straight line on a flat surface. The rack and pinion changes linear motion into rotary motion, or vice versa. A helical gear is similar to a spur gear, but its teeth are twisted instead of straight. Helical gears can be used to transmit motion between shafts that do not intersect and are at any angle with respect to each other. A bevel gear has straight or curved teeth on a conical surface near its rim. Bevel gears are used to transmit rotary motion between shafts that are not parallel and that would intersect at an angle if extended. Hypoid gears are special bevel gears used in the differential of an automobile to connect the drive shaft to the rear axle. A worm gear, meshed with a threaded cylinder, or worm, that resembles a screw, is used to transmit motion between perpendicular, nonintersecting shafts. See transmission.

Bibliography

See D. W. Dudley, ed., Gear Handbook (1962); H. J. Watson, Modern Gear Production (1970); R. J. Drago, Fundamentals of Gear Design (1988).

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gear

Machine component consisting of a toothed wheel attached to a rotating shaft. Gears operate in pairs, the teeth of one engaging the teeth of a second, to transmit and modify rotary motion and torque. To transmit motion smoothly, the contacting surfaces of gear teeth must be carefully shaped to a specific profile. The smaller of a gear pair is often known as the pinion. If the pinion is on the driving shaft, the pair acts to reduce speed and to amplify torque; if the pinion is on the driven shaft, the pair acts to increase speed and reduce torque.

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gear

1. a toothed wheel that engages with another toothed wheel or with a rack in order to change the speed or direction of transmitted motion

2. a mechanism for transmitting motion by gears, esp for a specific purpose

3. the engagement or specific ratio of a system of gears

4. Nautical all equipment or appurtenances belonging to a certain vessel, sailor, etc.

5. short for landing gear

6. a less common word for harness

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gear [gir]

(design engineering)

A toothed machine element used to transmit motion between rotating shafts when the center distance of the shafts is not too large.

(mechanical engineering)

A mechanism performing a specific function in a machine.

An adjustment device of the transmission in a motor vehicle which determines mechanical advantage, relative speed, and direction of travel.

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Gear

A machine element used to transmit motion between rotating shafts when the center distance of the shafts is not too large. Toothed gears provide a positive drive, maintaining exact velocity ratios between driving and driven shafts, a factor that may be lacking in the case of friction gearing which is subject to slippage.

The application of gears for power transmission between shafts falls into three general categories: those with parallel shafts, those for shafts with intersecting axes, and those whose shafts are neither parallel nor intersecting but skew.