Typically the base that is bolted into a huge concrete pad provides the necessary support for a tower crane. The base is attached to a mast or a tower and stabilizes the crane which is attached to the inside of the building's structure. Usually, this attachment point is to a concrete lift or to an elevator shaft.
Usually, 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 enable the crane to rotate.
Tower cranes may have a max unsupported height of 80m or 265 feet, while the minimum lifting capacity of a tower crane is 16,642 kg or 39,690 lbs. with counter weights of 20 tons. Furthermore, two limit switches are utilized to be able to make certain that the operator does not overload the crane. There is even one more safety feature referred to as a load moment switch to ensure 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 need to be brought to the construction site by utilizing a huge tractor-trailer rig setup. Next, a mobile crane is utilized in order to assemble the machinery portion of the crane and the jib. These sections are then attached to the mast. Next, the mobile crane adds counterweights. Crawler cranes and forklifts could be some of the other industrial machinery which is usually used to erect a crane.
Mast extensions are added to the crane as the building is erected. This is how the height of the crane could match the building's height. The crane crew uses what is called a climbing frame or a top climber which fits between the top of the mast and the slewing unit. 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 20 feet or 6.1m. Then, the operator of the crane utilizes the crane to insert and bolt into place one more mast section piece.