Page 853 - Rollingbearings

Design considerations
2 Determine the maximum misalignment Fig. 12
– Estimate the misalignment β of the Example application
housing seats based on speciied
tolerances.
– Where additional effects need to be
considered, advanced simulation or
tests may be required.

3 Check the permissible axial
displacement
Check the permissible axial displacement
in both directions, depending on the bear-
ing used (ig. 11):
– open bearing with a cage
– full complement bearing with a retain-
ing ring
– sealed bearing L = 3 000

s req < s – β k B
1
1
Symbols
or Veriication of axial displacement:
B bearing width [mm]
s req < s – β k B C red reduction of radial clearance as a 1 Required axial displacement
1
2
result of an axial displacement from a s req = α L ΔT
Where s req is too large, consider Offset centred position [mm] s req = 12 × 10 –6 × 3 000 × (90 – 20)
mounting, page 852. k misalignment factor (product table, = 2,5 mm
1
page 856) 2 Max misalignment
4 Check the internal clearance L shaft length between the bearings Input provided: 0,46°
– Determine the clearance reduction [mm] 3 Checking the permissible axial
caused by axial displacement. s 1 axial displacement limit in bearings displacement
with a cage or in full complement s req < s – β k B
1
1
bearings when displacing away from 2,5 < 15,2 – 0,46 × 0,123 × 82 ≈ 10,5
k s 2
2 req
C red = ———– the retaining ring [mm] (ig. 11) † okay
B
s 2 axial displacement limit in sealed and 4 Checking the internal clearance
– Determine the amount of clearance full complement bearings when dis-
k s 2
2 req
reduction from other effects and evalu- placing toward the seal or retaining C red = ———–
ate the residual clearance (Selecting ring respectively [mm] (ig. 11) B
initial internal clearance, page 183). s req required axial displacement from a
centred position [mm]
0,095 × 2,5 2
α thermal coeficient of expansion [°C –1 ] C red = —————– ≈ 0,007
= 12 × 10 –6 for steel 82
β misalignment [°]
ΔT temperature difference [°C] Min internal clearance when the bearing 10
is displaced:
Calculation example 170 – 7 = 163 μm
Application (ig. 12) Determine the clearance reduction
• Bearing C 3040 caused by other effects (e g interference
– d = 200 mm it, temperature difference between inner
– D = 310 mm and outer rings) and evaluate the residual
– B = 82 mm clearance (Selecting initial internal clear-
– Normal clearance: min 170 μm ance, page 183)
– s = 15,2 mm
1
– k = 0,123
1
– k = 0,095
2
• Shaft length L = 3 000 mm
• Temperature range for the shaft: 20 to
90 °C (70 to 195 °F)
• Max misalignment: 0,46°

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