Slewing bearings are often made with gear teeth integral with the inner or outer race, used to drive the platform relative to the base.
As for other bearings that reciprocate, rather than rotating continuously, lubrication can be difficult. The oil wedge built up in a continuously rotating bearing is disrupted by the stop start motion of slewing. Instead, a hydrostatic bearing with pumped oil flow may be used.
Double row ball slewing bearing, slewing ring has three seat rings, the steel ball and spacers can be directly arranged into the upper and lower race, and the steel ball has two different size.
Double row different ball slewing bearing , slewing ring’s axial and radial loads are relatively large, it is specially suitable for the medium diameter tower cranes, truck mounted cranes etc.