An engineering approach to assess friction torque in generally loaded four-point contact slewing bearings

This manuscript presents a tool for the estimation of the friction torque in four-point contact slewing bearings. A normalised expression for the friction torque is obtained that depends on three design parameters (osculation ratio, initial contact angle and preload of the balls) and the external loading system defined by three components (axial force, radial force and tilting moment). The authors perform normalised friction torque simulations for combinations of those six variables established upon a DoE. The load distribution problem is solved prior to the friction torque calculation, which considers rigid rings. The simulations do not consider the effects coming from the seals, the spacers or the cage. By interpolating friction torque results from the simulations, a sufficiently populated number of data points is obtained to generate friction torque maps. Assuming some simplifications, the friction torque maps allow both customers and manufacturers to estimate the friction torque in a practical way.