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1. INTRODUCTION
A bearing is a device to permit constrained relative motion
between two parts,
typically rotation or linear movement. Bearings may be
classified broadly accordingto the motions they allow and according
to their principle of operation.
Common motions include linear /axial and rotary /radial . A
linear allows motion along
a straight line , for example a drawer being pulled out and
pushed in. A rotary bearing
or thrust bearing allows motion about a center, such as a wheel
on a shaft or a shaft
through a housing. Common kinds of rotary motion include both
one-direction
rotation and oscillation where the motion only goes through part
of a revolution.
Other kinds of bearings include spherical bearings such as ball
joints which are usedin car suspensions and some computer mice
.
1.1 Types of Bearings
1. Solid lubricated bearings.
2. Fluid lubricated bearings.
a) Liquid lubricated bearing. b) Gas lubricated bearing.
3. Magnetic bearings.
1.2 Types of solid lubricated bearings:
Ball Bearings
http://en.wikipedia.org/wiki/Linearhttp://en.wikipedia.org/wiki/Axialhttp://en.wikipedia.org/wiki/Rotaryhttp://en.wikipedia.org/wiki/Radialhttp://en.wikipedia.org/wiki/Straight_linehttp://en.wikipedia.org/wiki/Thrust_bearinghttp://en.wikipedia.org/wiki/Wheelhttp://en.wikipedia.org/wiki/Shafthttp://en.wikipedia.org/wiki/Spherical_bearinghttp://en.wikipedia.org/wiki/Ball_jointhttp://en.wikipedia.org/wiki/Computer_mousehttp://en.wikipedia.org/wiki/Linearhttp://en.wikipedia.org/wiki/Axialhttp://en.wikipedia.org/wiki/Rotaryhttp://en.wikipedia.org/wiki/Radialhttp://en.wikipedia.org/wiki/Straight_linehttp://en.wikipedia.org/wiki/Thrust_bearinghttp://en.wikipedia.org/wiki/Wheelhttp://en.wikipedia.org/wiki/Shafthttp://en.wikipedia.org/wiki/Spherical_bearinghttp://en.wikipedia.org/wiki/Ball_jointhttp://en.wikipedia.org/wiki/Computer_mouse
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Ball bearings, as shown above, are probably the most common type
of bearing. They
are found in everything from inline skates to hard drives. These
bearings can handle
both radial and thrust loads, and are usually found in
applications where the load is
relatively small.
In a ball bearing, the load is transmitted from the outer race
to the ball, and from the
ball to the inner race. Since the ball is a sphere, it only
contacts the inner and outer
race at a very small point, which helps it spin very smoothly.
But it also means that
there is not very much contact area holding that load, so if the
bearing is overloaded,
the balls can deform or squish, ruining the bearing.
Roller Bearings
Roller bearings like the one illustrated below are used in
applications like conveyer
belt rollers, where they must hold heavy radial loads. In these
bearings, the roller is a
cylinder, so the contact between the inner and outer race is not
a point but a line. This
spreads the load out over a larger area, allowing the bearing to
handle much greater
loads than a ball bearing. However, this type of bearing is not
designed to handle
much thrust loading.
A variation of this type of bearing, called a needle bearing,
uses cylinders with a verysmall diameter. This allows the bearing
to fit into tight places
http://science.howstuffworks.com/hard-disk.htmhttp://science.howstuffworks.com/hard-disk.htm
