gear

—gearless, adj.

/gear/, n.

1. Mach.

a. a part, as a disk, wheel, or section of a shaft, having cut teeth of such form, size, and spacing that they mesh with teeth in another part to transmit or receive force and motion.

b. an assembly of such parts.

c. one of several possible arrangements of such parts in a mechanism, as an automobile transmission, for affording different relations of torque and speed between the driving and the driven machinery, or for permitting the driven machinery to run in either direction: first gear; reverse gear.

d. a mechanism or group of parts performing one function or serving one purpose in a complex machine: steering gear.

2. implements, tools, or apparatus, esp. as used for a particular occupation or activity; paraphernalia: fishing gear.

3. a harness, esp. of horses.

4. Naut.

a. the lines, tackles, etc., of a particular sail or spar.

b. the personal tools, clothing, and other possessions of a sailor.

5. portable items of personal property, including clothing; possessions: The campers keep all their gear in footlockers.

6. wearing apparel; clothing: The fashion pages of the Sunday paper are featuring the latest fall gear.

7. armor or arms.

8. in gear,

a. Mach. in the state in which gears are connected or meshed: The car is in gear.

b. in proper or active working order; functioning continuously without trouble: Every department in this company must be in gear at all times.

9. in or into high gear, in or into a state of utmost speed, activity, or efficiency: Military rearmament moved into high gear.

10. out of gear, Mach. in the state in which gears are not connected or meshed: The engine is out of gear.

11. shift or switch gears, to change one's attitude, course of action, methods, etc., in an abrupt, dramatic, or unexpected manner: In the middle of the second act the play shifts gears from comedy to tragedy.

v.t.

12. to provide with or connect by gearing.

13. to put in or into gear.

14. to provide with gear; supply; equip.

15. to prepare, adjust, or adapt to a particular situation, person, etc., in order to bring about satisfactory results: The producers geared their output to seasonal demands.

v.i.

16. to fit exactly, as one part of gearing into another; come into or be in gear.

17. gear down,

a. Auto. to shift the transmission of a vehicle to a lower gear: The truck driver geared down at the top of the hill.

b. to reduce in scope or intensity: With less income you'll have to gear down your spending habits.

18. gear up,

a. to make or get ready for a future event or situation: Insiders say the senator is gearing up to run for governor.

b. to get or put on equipment or clothing for a particular purpose: The hikers geared up for the long trek down the mountain.

c. to arouse or excite, as with enthusiasm or expectation: The employees were geared up for a hard battle with management over working hours.

adj.

19. Slang. great; wonderful.

[1150-1200; ME gere < ON gervi, gørvi; akin to OE gearwe equipment]

Syn. 2. equipment, outfit, tackle, rig.

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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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▪ mechanics

 machine component consisting of a toothed wheel attached to a rotating shaft. Gears operate in pairs to transmit and modify rotary motion and torque (turning force) without slip, the teeth of one gear engaging the teeth on a mating gear. If the teeth on a pair of mating gears are arranged on circles, i.e., if the gears are toothed wheels, the ratios of the rotary speeds and torques of the shafts are constant. If the teeth are arranged on noncircular bodies the speed and torque ratios vary.

      Most gears are circular. To transmit motion smoothly and with a nonvarying speed ratio at every instant, the contacting surfaces of gear teeth must be carefully shaped to a specific profile. If the smaller of a gear pair (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 as a speed increaser and a torque reducer. If the driven gear has twice as many teeth as the pinion, for example, the torque of the driven gear is twice the pinion torque, whereas the pinion speed is twice the speed of the driven gear.

      The shafts that gears connect must be relatively close, but they may have practically any spatial relationship with respect to one another; they may be parallel or nonparallel and intersecting or nonintersecting. For each of these arrangements of the shafts, gears having appropriate capabilities can be made. Parallel shafts can be connected by gears with teeth that are straight lengthwise and parallel to the shaft axes (spur gears) or by gears with twisted, screwlike teeth (helical gears). Intersecting shafts are connected by gears with tapered teeth arranged on truncated cones (bevel gears). Nonparallel, nonintersecting shafts are usually connected by a worm and gear. The worm resembles a screw, and the gear resembles a quarter section of a long nut that has been bent around a cylinder. The commonest angle between nonparallel shafts, either intersecting or nonintersecting, is a right angle (90°).

      Because it is basically a screw, a worm gear may have only one thread (tooth), whereas to maintain continuous contact with parallel shaft gears (spur and helical), the pinion must have at least five teeth. For this reason, to obtain a large speed ratio in a single gear pair, a worm and gear are well suited. If the shafts must be parallel, it may be necessary to use several gear pairs in series (a train) to obtain a large ratio. See also differential gear.

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