The invention relates to a method of manufacturing a tower (2) for an offshore wind turbine as well as such a tower. The method comprises providing the tower, mounting a crane (5) to an outer surface of the tower, and transporting the tower to the installation site of the wind turbine after the mounting of the crane. The crane comprises a base part (6) fixedly mounted to the tower, and a crane arm (7) pivotally connected to the base part at a first end (8). The method may further comprise a step of testing and certifying the crane according to a predetermined standard before the step of transporting the tower to the installation site. By application of the invention, the amount of installation work to be performed at the installation site can be minimized. In some embodiments of the invention, the crane arm has a shape matching the outer surface of the tower.

The invention relates to a method and a construction and/or a materials-handling machine for guiding and moving a working head, in particular a 3D print head, wherein at least three revolving tower cranes are attached to each other with their booms, wherein according to one aspect of the invention a guide beam carrying the working head is attached to at least two trolleys of two revolving tower cranes, and the working head is adjusted and moved in its working position by moving the trolleys along two booms of two revolving tower cranes.

Various embodiments of the teachings herein include methods for controlling a crane. The method may include: acquiring a first speed of a first motor pulling a first end of a hoist; acquiring a second speed of a second motor pulling a second end of the hoist opposite the first end; acquiring a first speed difference between the first speed and the second speed; acquiring a first speed difference threshold; and if the first speed difference is smaller than the first speed difference threshold, sending a control instruction to the first motor to increase a torque output value of the first motor in the trolley traveling direction.

A marine knuckle boom crane includes a pedestal and a crane housing rotational relative to the pedestal. A knuckle boom assembly is attached to the crane housing and includes a main boom and a spreader type jib. A hoisting system includes a first departure sheave and a second departure sheave on the jib, and a third departure sheave mounted to the main boom or to the crane housing. One or more winches drive a first, second, and third cable which are each connected to an object suspension device and each pass via the first, second, and third departure sheave, respectively, to the respective winch. The first, the second, and the third cable together define an inverted pyramid which diverges upwards from the object suspension device when handling the object.