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Rigidity

Roller bearings are more rigid than ball bearings

The rigidity of a rolling bearing is dependent on the bearing type, size and operating clearance. The rigidity increases with the number of rolling elements supporting the load. Due to the line contact between the rolling elements and raceways, it is higher in roller bearings than in ball bearings. ➤ Figure shows typical characteristic curves for the radial deflection of various bearings with the same bore diameter.

Radial deflection of various radial bearings of bore diameter d = 50 mm

δr =  radial deflection

Fr =  radial load

Calculation of the radial or axial displacement

Progressive deflection rate

Rolling bearings have a progressive deflection rate. The displacement values for needle and cylindrical roller bearings can be determined using approximation equations ➤ Equation and ➤ Equation.

The equations are valid for bearings without misalignment and with a rigid surrounding structure. In axial bearings, a concentrically acting load is assumed.

Radial displacement


Axial displacement


Rigidity parameter


Legend

cs N0,84/μm

Rigidity parameter

d mm

Bearing bore diameter

δr μm

Radial displacement between shaft axis and centre of bore ➤ Figure

δa μm

Axial displacement between shaft locating washer and housing locating washer ➤ Figure

s μm

Radial operating clearance of fitted, unloaded bearing

Fr N

Radial load

Fa N

Axial load

FaV N

Axial preload force

Kc -

Factor for determining the rigidity parameter ➤ Table

Radial cylindrical roller bearings, radial displacement

δr =  radial displacement

Fr =  radial load

Axial cylindrical roller bearing, axial displacement

δa =  axial displacement

Fa =  axial load

FaV =  axial preload force


Factor Kc

Bearing series

Factor

Kc

Series

Factor

Kc

SL1818

12,8

K811, 811,
K812, 812

36,7

SL1829, SL1830, SL1923

16

K893, 893,
K894, 894

59,7

SL1850, SL0148, SL0248, SL0249

29,2

NJ2..-E

11,1

NA48

24,9

NJ3..-E

11,3

NA49

23,5

NJ22..-E

15,4

NA69

37,3

NJ23..-E

16,9

NKIS

21,3

NU10

9,5

NKI

4,4 · B0,8/d0,2

NU19

11,3

HK, BK

4,2 · C0,8/d0,2

NN30..-AS-K

18,6

This simplified calculation cannot be applied to other bearing types. The displacement and rigidity at the operating point can be determined using the calculation program BEARINX.