The swiveling can be done by a double acting cylinder, which transmits via a rack and bevel the movement to engage in a fixed ring gear planetary gear mounted the swivel work. More common is the execution of two plunger cylinders which act alternately on one chain (rope), which have led to a suitably arranged sheave, the swinging movement initiates.
The cylinders can be mounted on the boom, so that they participate in the swing, or be housed separated in the foundation of the crane frame (see Figure)