Turning torque calculation

The calculation of the torque Mr, detailed below is based on theoretical and empirical knowledge. The torque is affected by the rolling friction coefficient, the rolling elements, spacers, seals, load distribution and the load.

Some other factors affecting the torque are:

  • The out-of-flatness including the slope of the upper and lower companion structure.
  • The grease filling and the type of grease.
  • The lubrication of the lip seals and the seal preload.
  • The variation in the bearing‘s clearance resulting from installation.

The torque calculated is, of course, subject to certain fluctuations, which can be estimated with approx. ± 25%.

  1. Starting Torque Mr

    Ball bearing slewing rings



    Roller bearing slewing rings



  2. Power of Inertia PBeh.



Specially designed bearings with reduced torque can be supplied. Please contact us regarding the applications for such bearings

In order to assess the total moment necessary for rotating the bearing, the acceleration power of all the individual masses must still be configured as a product using the squared distance of their centres of gravity from the axis of rotation. The strength of the wind, which may possibly act upon the bearing, and any component parts under slope must also be taken into account.

Symbols used

Fa      = axial load [kN]
Fr = radial load [kN]
Mk = resulting tilting moment [kNm]
DL = bearing race diameter [m]
µ = friction coefficient  
ω = angular velocity  
ω = [s-1]
n = number of bearing revolutions per minute [min-1]
η = drive efficiency  
 
Various friction coefficients
 
µ = 0.008 for Type KD 210 (Type 13 und 21, normal bearings)
  = 0.006 for Type KD 210 (Type 110)
  = 0.004 for Type KD 320
  = 0.006 for Type KD 600
  = 0.003 for Type KD 700
  = 0.004 for Type KD 800
  = 0.003 for Type RD 900

 

For precision bearings, bearings without clearance and preloaded bearings, the turning torque calculation has to be performed by Rothe Erde.