truck 4 by disengaging the rapid action couplings 9 and 24 and removed the superstructure 2 can be directly placed onto the truck 4 if a tracklaying gear with a narrow track is not required the separable rapid action couplings also make it possible to mount a different truck 4 in this case the rapid action coupling 24 is disengaged and the supporting device 3 with the superstructure 2 arranged thereon is raised by lowering the outriggers 12 the narrow tracklaying gear is then driven away and replaced with another tracklaying gear that is illustrated in fig1 once the outriggers 12 are retracted the center part 11 with the truck bearing 26 is placed onto the new truck according to fig1 the tracklaying gear of this truck may have a track width to track length ratio of approximately u00be to 1 the steering of the crane with the narrow tracklaying gear according to fig1 and 2 is realized as described below in the position according to fig3 in which the crane still points in the old driving direction the legs 17 of the supporting device 3 are initially lowered such that the supporting device 3 lifts the entire crane including the truck 4 with the tracklaying gear 21 off the ground in this raised position of the tracklaying gear 21 the truck 4 is turned in the desired new driving direction relative to the supporting device 3 by means of the truck rotary drive 20 in fig4 the truck is turned by 90 u00b0 the legs 17 are then slightly raised such that the tracklaying gear 21 once again comes in contact with the ground the outriggers 12 remain in contact with the ground during this process the superstructure 2.