ROLLING CONTACT BEARINGS PPT

Question 1

In rolling contact bearings, the contact between the bearing surfaces is rolling instead of sliding as in sliding contact bearings.

It is an outstanding advantage of a rolling contact bearing over a sliding bearing that it has a low starting friction.

Due to this low friction offered by rolling contact bearings, these are called ______________.

Answer 1

antifriction bearings

Question 2

The _________________ consist of an inner race which is
mounted on the shaft or journal and an outer race which is carried by the housing or casing.

In between the inner and outer race, there are balls or rollers.

A number of balls or rollers are used and these are held at proper distances by retainers so that they do not touch each other.

The ___________ are used for light loads and the roller bearings are used for heavier loads.

Answer 2

ball and roller bearings

Question 3

The __________ are thin strips and is usually in two parts which are assembled after the balls have been properly spaced.

Answer 3

retainers

Question 4

During assembly of this bearing, the races are offset and the maximum number of balls are placed between the races.

The races are then centred and the balls are symmetrically located by the use of a retainer or cage.

The deep groove ball bearings are used due to their high load carrying capacity and suitability for high running speeds.

The load carrying capacity of a ball bearing is related to the size and number of the balls.

Answer 4

Single row deep groove bearing

Question 5

These bearings have notches in the inner and outer races which permit more balls to be inserted than in a deep groove
ball bearings.

The notches do not extend to the bottom of the race way
and therefore the balls inserted through the notches must be
forced in position.

Since this type of bearing contains larger number of balls
than a corresponding unnotched one, it has a larger radial load capacity; but the filling notches reduce the allowable thrust load.

Answer 5

Filling notch bearing

Question 6

These bearings have one side of the outer race cut away to
permit the insertion of more balls than in a deep groove
bearing but without having a notch cut into both races.

______________ are so named because the line through the areas carrying the load makes an angle with the plane of the face of the bearing.

This permits the bearing to carry a relatively large axial load
in one direction while also carrying a relatively large radial
load.

The _________________ are usually used in pairs so that
thrust loads may be carried in either direction.

Answer 6

Angular contact bearing

Question 7

These bearings may be made with radial or angular contact
between the balls and races.

The ______________ is appreciably narrower than two single row bearings.

The load capacity of such bearings is slightly less than twice that of a single row bearing.

Answer 7

Double row bearing

Question 8

These bearings permit shaft deflections within 2-3 degrees.

It may be noted that normal clearance in a ball bearing are
too small to accommodate any appreciable misalignment of
the shaft relative to the housing.

If the unit is assembled with shaft misalignment present,
then the bearing will be subjected to a load that may be in excess of the design value and premature failure may occur.

Answer 8

Self-aligning bearing

Question 9

In an ___________________, the outside diameter of the outer race is ground to a spherical surface which fits in a mating spherical surface in a housing.

Answer 9

externally self-aligning bearing

Question 10

In case of_________________, the inner surface of the outer race is ground to a spherical surface.

Answer 10

internally self-aligning bearing

Question 11

The ______________ has a capacity 30 to 40 per cent over the light series.

Answer 11

medium series

Question 12

The ____________ has 20 to 30 per cent capacity over the medium series. This series is not used extensively in industrial applications.

Answer 12

heavy series

Question 13

The ___________________ are used for carrying thrust loads
exclusively and at speeds below 2000 rpm.

At high speeds, centrifugal force causes the balls to be forced out of the races.

Therefore at high speeds, it is recommended that angular contact ball bearings should be used in place of ____________.

Answer 13

thrust ball bearings

Question 14

These bearings have short rollers guided in a cage. These bearings are relatively rigid against radial motion and have the lowest coefficient of friction of any form of heavy duty rolling-contact bearings. Such type of bearings are used in high speed service.

Answer 14

Cylindrical roller bearings

Question 15

These bearings are self-aligning bearings. The self-aligning feature is achieved by grinding one of the races in the form of sphere. These bearings can normally tolerate angular
misalignment in the order of ± 1.5° and when used with a double row of rollers, these can carry thrust loads in either direction.

Answer 15

Spherical roller bearings

Question 16

These bearings are relatively slender and completely fill the space so that neither a cage nor a retainer is needed. These bearings are used when heavy loads are to be carried with an oscillatory motion, e.g. piston pin bearings in heavy duty diesel engines, where the reversal of motion tends to keep the rollers in correct alignment.

Answer 16

Needle roller bearings

Question 17

The rollers and race ways of these bearings are truncated cones whose elements intersect at a common point. Such type of bearings can carry both radial and thrust loads. These bearings are available in various combinations as double row bearings and with different cone angles for use with different relative magnitudes of radial and thrust loads.

Answer 17

Tapered roller bearings

Question 18

The load carried by a non-rotating bearing is called a

Answer 18

static load

Question 19

The _______________ rating is defined as the static radial load (in case of radial ball or roller bearings) or axial load (in case of thrust ball or roller bearings) which corresponds to a total permanent deformation of the ball (or roller) and race, at the most heavily stressed contact, equal to 0.0001 times the ball (or roller) diameter.

Answer 19

basic static load

Question 20

The _________________ may be defined as the static radial load (in case of radial ball or roller bearings) or axial load (in case of thrust ball or roller bearings) which, if applied, would cause the same total permanent deformation at the most heavily stressed ball (or roller) and race contact as that which occurs under the actual conditions of loading.

Answer 20

static equivalent load

Question 21

The _____ of an individual ball (or roller) bearing may be defined as the number of revolutions (or hours at some given constant speed) which the bearing runs before the first evidence of fatigue develops in the material of one of the rings or any of the rolling elements.

Answer 21

life

Question 22

The __________ of a group of apparently identical ball or roller bearings is defined as the number of revolutions (or hours at some given constant speed) that 90 per cent of a group of bearings will complete or exceed before the first evidence of fatigue develops (i.e. only 10 per cent of a group of bearings fail due to fatigue).

Answer 22

rating life

Question 23

The term _____________ is also used to denote the rating life. It has been found that the life which 50 per cent of a group of bearings will complete or exceed is approximately 5 times the life which 90 per cent of the bearings will complete or exceed.

Answer 23

minimum life

Question 24

The ________________________ is defined as the constant stationary radial load (in case of radial ball or roller bearings) or constant axial load (in case of thrust ball or roller bearings) which a group of apparently identical bearings with stationary outer ring can endure for a rating life of one million revolutions (which is equivalent to 500 hours of operation at 33.3 rpm) with only 10 per cent failure.

Answer 24

basic dynamic load rating

Question 25

The ______________________ may be defined as the constant
stationary radial load (in case of radial ball or roller bearings) or
axial load (in case of thrust ball or roller bearings) which, if applied to a bearing with rotating inner ring and stationary outer ring, would give the same life as that which the bearing will attain under the actual conditions of load and rotation.

Answer 25

dynamic equivalent load

Question 26

The ______________ is defined as the ratio of the number of bearings which have successfully completed L million revolutions to the total number of bearings under test.

Answer 26

reliability (R)