Table of contents
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.
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Radial deflection of various radial bearings of bore diameter d = 50 mm δr = radial deflection Fr = radial load |
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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 |
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Radial cylindrical roller bearings, radial displacement δr = radial displacement Fr = radial load |
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Axial cylindrical roller bearing, axial displacement δa = axial displacement Fa = axial load FaV = axial preload force |
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Factor Kc
|
Bearing series |
Factor Kc |
Series |
Factor Kc |
|---|---|---|---|
|
SL1818 |
12,8 |
K811, 811, |
36,7 |
|
SL1829, SL1830, SL1923 |
16 |
K893, 893, |
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.