Usually the base that is bolted into a large concrete pad provides the crucial support for a tower crane. The base is attached to a mast or a tower and stabilizes the crane that is connected to the inside of the structure of the building. Usually, this attachment point is to an elevator shaft or to a concrete lift.
Generally, the mast is a triangulated lattice structure measuring 10 feet square or 0.9m2. The slewing unit is attached to the very top of the mast. The slewing unit is made of a gear and a motor that allows the crane to rotate.
Tower cranes are able to have a maximum unsupported height of 80m or 265 feet. The tower crane's maximum lifting capacity is 16,642 kg or 39,690 lbs. with counter weights of 20 tons. In addition, two limit switches are used to be able to make certain that the operator does not overload the crane. There is also one more safety feature called a load moment switch to make certain that the driver does not surpass the ton meter load rating. Last of all, the maximum reach of a tower crane is 230 feet or 70 meters.
Due to their extreme heights, there is a science involved to erecting a crane. The stationary structure will first have to be brought to the construction site by utilizing a large tractor-trailer rig setup. After that, a mobile crane is used in order to assemble the machine portion of the jib and the crane. Afterwards, these parts are connected to the mast. The mobile crane then adds counterweights. Forklifts and crawler cranes could be some of the other industrial machinery that is utilized to erect a crane.
Mast extensions are added to the crane when the building is erected. This is how the height of the crane could match the building's height. The crane crew uses what is referred to as a top climber or a climbing frame which fits between the slewing unit and the top of the mast. A weight is hung on the jib by the work crew so as to balance the counterweight. When complete, the slewing unit could detach from the top of the mast. In the top climber, hydraulic rams are used to adjust the slewing unit up an additional 6.1m or 20 feet. Then, the operator of the crane uses the crane to insert and bolt into place another mast part piece.