bearing

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bearing,

machine part designed to reduce frictionfriction,
resistance offered to the movement of one body past another body with which it is in contact. In certain situations friction is desired. Without friction the wheels of a locomotive could not "grip" the rails nor could power be transmitted by belts.
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 between moving parts or to support moving loads. There are two main kinds of bearings: the antifriction type, such as the roller bearing and the ball bearing, operating on the principle of rolling friction; and the plain, or sliding, type, such as the journal bearing and the thrust bearing, employing the principle of sliding friction. Roller bearings are either cylindrical or tapered (conical), depending upon the application; they overcome frictional resistance by a rolling contact and are suited to large, heavy assemblies. Ball bearings are usually found in light precision machinery where high speeds are maintained, friction being reduced by the rolling action of the hard steel balls. In both types the balls or rollers are caged in an angular grooved track, called a race, and the bearings are held in place by a frame, commonly called a pillow block or plummer block. Ball bearings or roller bearings reduce friction more than sliding bearings do. Other advantages of antifriction bearings include ability to operate at high speeds and easy lubrication.

A journal bearing usually consists of a split cylindrical shell of hard, strong metal held in a rigid support and an inner cylindrical part of soft metal, which holds a rotating shaft, or journal. A self-aligning journal bearing has a spherically shaped support that turns in a socket to adjust to movements of the shaft. Slight misalignment of the shaft can be accommodated in the ordinary journal bearing by wearing of the soft bearing material, often an alloy of tin or lead. Less frequently used are aluminum alloys, steel, cast iron, or a thin layer of silver covered with a thin coating of a soft bearing material. Ideally, a film of lubricant, normally oil, separates journal and bearing so that contact is prevented (see lubricationlubrication,
introduction of a substance between the contact surfaces of moving parts to reduce friction and to dissipate heat. A lubricant may be oil, grease, graphite, or any substance—gas, liquid, semisolid, or solid—that permits free action of mechanical devices
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). Bearings that are not split are called bushings.

A thrust bearing supports an axial load on a shaft, i.e., a force directed along a shaft's length. It may be a plate at the end of a shaft or a plate against which the collar on the shaft pushes. Large thrust bearings, such as those used to transmit the motive force of a ship's propeller from the shaft to the hull, have blocks that are separated from the collar on the shaft by wedge-shaped spaces filled with oil. Graphite bearings are used in high-temperature situations. Certain plastics make satisfactory self-lubricating bearings for low speeds and light loads and, if additionally lubricated, work at higher speeds and carry greater loads. Rubber and a naturally oily wood, lignum vitae, are used in water-lubricated bearings. Watches and other precision instruments have glass or sapphire pivot bearings. In gas-lubricated bearings a film of gas separates the bearings from the moving machine parts. Magnetic bearings employ magnetic repulsion to separate journal from bearing, reducing friction still further.

Bearing

 

in navigation, the angle between the meridian plane of the observer and the vertical plane passing through the point of observation and the observed object. The bearing angle is the same as the azimuth. Bearings are designated as true, magnetic, or compass bearings, depending on the type of meridian from which they are reckoned.

There are several systems for taking bearings. In the circular method, lines of position are stated in degrees clockwise from the northerly meridian. In the semicircular method, lines of position can be read clockwise in degrees from the northerly and southerly meridians. The quadrant method states lines of position in terms of quadrants; that is, the bearing angle is read with respect to the northerly and southerly meridian clockwise and counterclockwise between the limits of 0° and 90°. The rhumb method is also used, in which bearings are taken by dividing the circle of the compass into 32 rhumbs and reading from the northerly meridian.


Bearing

 

a shaft or axle support that fixes the position of a rotating or rocking part of a mechanism relative to the other parts. Bearings are classified according to the direction of loading as radial, taking loads perpendicular to the axis of the shaft; thrust, taking loads directed along the axis of the shaft; and radial-thrust, taking composite loads, mostly radial (thrust-radial bearings, taking mainly axial loads, are used less frequently). Bearings are also distinguished according to the type of friction as rolling-contact (the more common) and plain types.

bearing

[′ber·iŋ]
(civil engineering)
That portion of a beam, truss, or other structural member which rests on the supports.
(mechanical engineering)
A machine part that supports another part which rotates, slides, or oscillates in or on it.
(mining engineering)
The direction of a mine drivage, usually given in terms of the horizontal angle turned off a datum direction, such as the true north and south line.
(navigation)
The horizontal direction from one terrestrial point to another; basically synonymous with azimuth.

bearing

bearing, 4
1. A bearer.
2. That portion of a beam, truss, or other structural member which rests on the supports.
3. The support for a shaft, axle, or trunnion.
4. In surveying, the horizontal angle between a line and a reference meridian adjacent to the quadrant in which the line lies.

bearing

bearing
bearing
Spherical roller thrust bearing.
i. The horizontal angle at a given point measured clock-wise from a specific reference datum to a second point. The bearing can be true, magnetic, relative, or grid, depending on the selected datum.
ii. A surface that supports and reduces friction between two moving points.

bearing

1. a support, guide, or locating piece for a rotating or reciprocating mechanical part
2. the angular direction of a line, point, or course measured from true north or south (true bearing), magnetic north or south (magnetic bearing), or one's own position
3. the position or direction, as of a ship, fixed with reference to two or more known points
References in classic literature ?
The doctor watched him with a smile; and, while Joe went on, he took the bearings, and found that the missionary's grave lay in twenty-two degrees twenty-three minutes east longitude, and four degrees fifty-five minutes north latitude.
It might have been fanciful to suppose that under their outer bearing there was something of the shamed air of two cheats who were linked together by concealed handcuffs; but, not so, to suppose that they were haggardly weary of one another, of themselves, and of all this world.
A negro accompanied him, bearing a bucket of water and a flask of wine.
None of them had ever seen a person bearing a title of nobility before, and none had been expecting to see one now, consequently the title came upon them as a kind of pile-driving surprise and caught them unprepared.
A warrior approached bearing the arms, ornaments, and full accouterments of his kind.
They spoke of a daughter, a wanderer they knew not where, bearing dishonor along with her, and leaving shame and affliction to bring their gray heads to the grave.
Such was the fate of Major Henry Vanderburgh, one of the best and worthiest leaders of the American Fur Company, who by his manly bearing and dauntless courage is said to have made himself universally popular among the bold-hearted rovers of the wilderness.
But if you have sighted it on the expected bearing, then that Landfall is good.
And laughter-loving Venus answered, "Proud Diomed, the son of Tydeus, wounded me because I was bearing my dear son Aeneas, whom I love best of all mankind, out of the fight.
In order, doubtless, to give a show of variety, Poe was then publishing some of his known works in his journal over noms de plume, and as no other writings whatever can be traced to any person bearing the name of "A.
The same spirit of legislation prevailed with respect to their bearing arms and their gymnastic exercises; for the poor are excused if they have no arms, but the rich are fined; the same method takes place if they do not attend their gymnastic exercises, there is no penalty on one, but there is on the other: the consequence of which is, that the fear of this penalty induces the rich to keep the one and attend the other, while the poor do neither.
Then her eyelids drooped again; she thought that all was over, that they had executed her during her swoon, and that the misshapen spirit which had presided over her destiny, had laid hold of her and was bearing her away.