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Rolling Element BearingsTapered Roller Bearings

 prepared by

Wayne Book 

ME3180

Based on Shigley and MischkeDesign of Mechanical Elements

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Rolling Element Bearings

Outline• Bearing types and nomenclature

• Loads, life and failure modes

• Ball bearing selection criteria

• Tapered bearings

 – Induced thrust load

 – Selection

• Application and maintenance

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Roller Bearing Nomenclature(from Shigley)

Induced thrust

Applied 

radial force

Induced thrust is also transmitted

to cone and hence to shaft

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Calculating Tapered Bearing

Loads

Tex 

Frex 

FrA TA 

TB 

L1 L2 

(from charts) a

rexrBrA

rBrex

 yG

ex A

rA B

ex B

rB A

 F  F  F 

 F  L L F  L F  M 

T  K 

 F T 

T  K 

 F 

T 

0)(00

 ,47.0

 ,

47.0

:thrustcarriesaloneitif as

 bearingeachgConsiderin

211

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Effective Radial Loads

• For sizing bearing the effective radial load will be used.

• If the effective radial load is less than the actual radial

load, use the actual load

• Bearing A induces thrust on B and vice versa

 

  

 

 

  

 

rB

ex

 A

rA BrB

eB

rA

ex

 B

rB ArA

eA

 F 

T  K 

 F  K  F 

 F 

 F 

T  K 

 F  K  F 

 F 

47.04.0

max

47.04.0

max

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Example Table for Bearing Selection

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Example Selection Problem• Gear transmission as shown with small gear being helical

which generates thrust of 0.3 x tangential force

• Obtain radial loads assuming static equilibrium

• Use estimates of a=0 and K=1.5 to begin problem

• Seek life of 50,000 hours at 1000 rpm

•  Nominal shaft diameter = 1 in.

• Force angles on gear at 25 degrees

• Use identical tapered roller bearings

15” 

3” 6” 

300 lb

3” 10”  Tapered roller bearing

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Example Solution

AB C

D

15” 

3” 6” 

300 lb

3” 10” 

FrCFrB 

lbf   F 

 F  F  F  F  F 

lbf   F 

T  F  F  F  M 

rA

rDrC rBrA y

rD

exrDrC rB

6.193

0

8.186

5.1151030

mequilibriu byreactionsdetermine

FrD FrA 

lbf  T 

 F T 

ex

tC ex

1.76

3.0

Tex 

lbf   F 

lbf   F 

tB

rB

9.27125cos300

8.12625sin300

FrB FtB 

lbf   F  F 

lbf   F  F 

 F  F 

tC rC 

tBtC 

tBtC 

6.25325tan

8.5432

35.1

 mequilibriufor 

FrC 

FtC 

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Mounting Bearings with Thrust

Loading• Ideally the constraints are not redundant

• Consider the case where thrust can reverse

• Arrows show load transfer for either direction

• Thrust in either direction carried by left bearing

Force provided

 by retainer 

Right bearing floats

in housing

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Preload Arranged at One End of 

Shaft

• Controlled amounts of preload is useful to

eliminate clearance if improved accuracy is

needed.

Preload

adjustment

Preload

adjustment

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