Generally the base which is bolted into a huge concrete pad provides the essential 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 a concrete lift or to an elevator shaft.
Generally, the mast is a triangulated lattice structure measuring 0.9m2 or 10 feet square. The slewing unit is connected to the very top of the mast. The slewing unit consists 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 kilograms or 39,690 pounds with counter weights of 20 tons. Furthermore, two limit switches are used to be able to ensure the driver does not overload the crane. There is also one more safety feature called a load moment switch to make certain that the operator does not surpass the ton meter load rating. Finally, the maximum reach of a tower crane is 230 feet or 70 meters.
Because of their extreme heights, there is a science involved to erecting a crane. The stationary structure will first need to be brought to the construction location by utilizing a huge tractor-trailer rig setup. After that, a mobile crane is utilized so as to assemble the machinery portion of the crane and the jib. These sections are then connected to the mast. Afterward, the mobile crane adds counterweights. Crawler cranes and forklifts may be some of the other industrial machines that is commonly utilized to erect a crane.
When the building is erected, mast extensions are added to the crane. This is how the crane's height could match the building's height. The crane crew uses what is referred to as a climbing frame or a top climber 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 can detach from the top of the mast. In the top climber, hydraulic rams are used to adjust the slewing unit up an additional 20 feet or 6.1m. After that, the crane driver uses the crane to insert and bolt into position one more mast section piece.