Rolling-Element Bearings Calculation and selection using SKF Bearing Catalogue
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Principle of the Rolling-Element Bearings is very old.
This picture shows the principle of a Rolling-Element Bearing of today.
This picture shows how the people in ancient Mesopotamia moved huge stones.
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Modern Rolling Bearings
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• Outer ring
• Inner ring
• Rolling Elements
– Balls & Cage
– Rollers & Cage
Industrial revolution
• Development of modern Bearing
• Better material and better manufacturing methods resulted in better bearings
• Big need for rolling bearings
• Sewing machines’ and bicycle manufactures the biggest bearing consumers
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The diagram shows statistics of patents applications for bicycle bearings in England
This picture shows a drawing from a French patent of 1802.
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Tapered rollerThrust bearing(konisktaxialrullager)
Thrustball bearing(axialkullager)
Sven Wingquist and the Self-aligning ball bearing
• Maintenance engineer at Gamelstadensfabriker
• Frequent failures in deep groove ball bearings
• Reason: misaligning of the shafts of belt transmissions
• Invented a new bearing to accept missaligning
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Drawing of the Swedish patent number 25406 from 1907 by Sven Wingquist.Self-aligning ball bearing (Sfäriskt kullager)
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The Spherical roller bearing
• Development period: from 1919 to 1935
• Invented by Arvid Palmgren
• SKF’s research budget was bigger the research budget of whole Royal Technical Institute in Stockholm
• SKF calculations theory become world standard in 1947. (developed by Palmgren and mathematic Prof. G. Lundberg from RTI)
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Bearings are divided in two groups dependent on rolling elements.
Ball Bearings & Roller Bearings
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Stress concentration
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Loads and bearing types
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3
2
2
210
)11
(
578,0
RR
F
p
L
RRF
p
)11
(
564,0 210
Maximum contact pressure
For two spheres For two Cylinders
Low load
Ball bearings
Middle sized loads;
Ball or roller bearings
High load
Roller bearings
Bearings are also divided in two groups dependent on load direction.
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Radial load
Radial bearings
(radiallager) Example
Axial loadThrust bearings
(axiallager)
Example
Three groups of Rolling Element Bearing (Rolling Bearings)
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1. Radial Ball Bearings
Deep groove
ball bearing
Self-aligning
ball bearing
Angular contact
ball bearing
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2. Radial Roller Bearings
Cylindrical Roller Bearing & Spherical Roller Bearing
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Tapered Roller Bearing & Needle Roller Bearing
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3. Thrust (axial) BearingsShaft washer, Housing washer, Rolling element, and cage
Shaft
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Thrust ball bearing, Cylindrical roller thrust bearing & Spherical roller thrust bearing
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Use of bearings
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Selecting bearing size using the life equations
(SKF p. 64-65)
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L10 = basic rating life (at 90% reliability),
millions of revolutions
L10h = basic rating life (at 90% reliability),
operating hours
p = exponent of the life equation
p = 3 for ball bearings
p = 10/3 for roller bearings
n = rotational speed, rpm
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p
SKFnmhP
C
naaL
60
10000001
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Example: Self-aligning ball bearing (SKF p. 544)
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Sample problem:
Unsealed bearing: use SKF lubricating grease LGMT 2
c = 0,2
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SKF 6214 (SKF p. 330)
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SKF 6214 (SKF p. 331)
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(SKF p. 316)
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(diagram 1-4, SKF p. 66-69)
But first, we have to follow some steps:
Step 1: required kinematic Viscosity
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Step 2: Actual viscosity
SKF greases – LGMT 2(Table 4, SKF p.250)
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Diagram with logarithmic scale on y-axis
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Step 3:
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Step 4: to find factor for different levels of contaminations(Table 4, SKF p. 74)
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p
SKFnaahP
C
naaL
60
10000001
hours435752347
763
125060
100000050L
3
mh10
,
,
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hours26145347
763
125060
10000003L
3
mh10
,
,
Tolerances required for mounting and running of the bearings
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Tolerances and fits
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International Tolerance Grades or IT Grades
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Run-outs
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Total run-outs
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