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Friction
Friction
Friction of roller bearings is low. Different types of friction may occur, depending on design and operating conditions.
You should make at least a rough calculation of the different types of friction. The following friction types are
involved:
• Rolling friction
• Kinetic friction
• Lubricant friction
It is advisable to determine the friction heat generated as to select the lubrication system, lubricant, and speed limit,
if any.
Friction torque estimate
The friction may be roughly calculated as follows
d
M R = µ · F · — [Nmm]
2
M R total friction moment [Nmm]
µ friction factor
2 2
+ Fa [N]
F resulting bearing load F = F Fr
d bore bearing bore diameter [ mm ]
The friction factors listed in the following table apply for the bearing types used:
Friction coefficients
Friction energy is calculated as follows:
Bearing design Friction factor µ
Deep groove ball bearings 0,0015
Angular contact ball bearings, single row 0.0020
Angular contact ball bearings, double row 0.0024
Four point bearings 0,0024
Cylindrical roller bearings 0.0013
Cylindrical roller bearings, cageless 0.0020
Axial cylindrical roller bearings 0,0040
Tapered roller bearings 0.0018
Double row spherical roller bearings 0.0020
NR =
. . . -4
MR n 1,047 10 [W]
NR total friction heat
M R estimated total friction moment [Nmm]
n operating speed [rpm]
If needed, determine the components of the roughly calculated friction moment separately. Split down into the following
components::
Load independent friction moment
M 0 = f 0
M 0 = f 0
. -7 . 2/3 . 3 .
10 (ν n) dm für ν n ≥ 2000 [Nmm]
. . 2/3 . 3 -7 .
160 (ν n) dm 10 für ν n < 2000 [Nmm]
M 0 load dependent friction moment [Nmm]
f 0
coefficent for bearing design and lubrication conditions
ν operating viscosity of the lubricating oil or of the basic
oil of the lubricating grease, respectively [mm 2 /s]
n speed [rpm]
D+d
d m reference diameter d m = ———
2
[mm]
Use the following values for factor f0 : If minimum oil lubrication is used (e. g. oil mist lubrication), multiply the factors
fo by 0.4 ... 0.6.