The drive unit has a motor (3) i.e. hydraulic motor, a transmission (4) and a drive shaft on which a pinion (6) is arranged for driving the gear ring. A mechanical overload protection unit e.g. slip clutch or disengaging clutch, is arranged between the transmission and the pinion. The overload protection unit is designed as a predetermined breaking point (20) of an output shaft. A common housing (10) i.e. oil-tight housing, is provided for the transmission, the overload protection unit and a main bearing (9) of the output shaft. The predetermined breaking point is realized by shear pins. Independent claims are also included for the following: (1) a set of drive units for common drive of a gear ring (2) a device comprising a gear ring.