Rolling Bearing Friction |
Rolling bearings are called anti-friction bearing. They have high loading
capacity and exhibit very low rolling friction torques. The friction torques
are similar or lower than ideally designed plain bearing operating under conditions of thick film
lubrication. Rolling bearing have low starting torques
The coefficient of friction in rolling bearings relates to the type of bearing,
the speed of rotation, the load, the amount and viscosity of the lubrication, the
friction of the seals, etc etc.
The bearing friction torque Mr = F . f . (d/2)
The bearing friction torque Mr = F . fm . (Dm/2) (friction values below marked with ***)
- Mr = Friction torque (Nmm)
- F = Radial (or axial load) (N)
- f = coefficient of friction of rolling bearing .
- fm = coefficient of friction of rolling bearing based on mean diameter
- d = Diameter of the bore of the bearing (Shaft diameter)(mm)
- D = Outside diameter of the bearing (mm)
- Dm = (d+D)/2 (mm)
These values relate to running bearings without seals and with optimimum lubrication..
The start-up friction values will be higher -up to twice the values quoted below..
- Single row ball bearing (radial Load) ..f = 0,0015
- Angular contact ball bearing (single row) ..f = 0,0020
- Angular contact ball bearing (double row) ..f = 0,0024
- Self aligning ball bearing (radial load) ..f = 0,0010
- Cylindrical roller bearings with cage ..f = 0,0011
- Cylindrical roller bearings full complement ..f = 0,0020
- Thrust ball bearing (axial load) ..f = 0,0013
- Spherical roller bearing (radial Load) ..f = 0,0018
- Taper roller bearings ..f = 0,0018
- Needle roller bearings-with cage ..fm = 0,003
- Needle roller ball bearings-full Complement ..fm = 0,005
- Combined needle roller bearings ..fm = 0,004
- Axial Needle roller ball bearings ..fm = 0,0035
- Axial Cylindrical roller bearings ..fm = 0,0035
The seal friction should also be included if seals are fitted.
A reasonable average value for a first estimate would be 0.001.
More accurate values for bearing rolling friction are
found in the suppliers technical literature..(see links below)