Usually the base that is bolted into a big concrete pad provides the necessary support for a tower crane. The base is attached to a mast or a tower and stabilizes the crane that is attached 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 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 kilograms or 39,690 lbs. with counter weights of 20 tons. Furthermore, two limit switches are utilized in order to ensure the operator does not overload the crane. There is also one more safety feature known as a load moment switch to ensure that the driver does not exceed 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 would at first need to be brought to the construction site by using a large tractor-trailer rig setup. Next, a mobile crane is used in order to assemble the equipment portion of the jib and the crane. These sections are then connected to the mast. Afterward, the mobile crane adds counterweights. Forklifts and crawler cranes may be some of the other industrial equipment that is utilized to erect a crane.
When the building is erected, mast extensions are added to the crane. This is how the crane's height can match the building's height. The crane crew utilizes what is known as a climbing frame or a top climber that 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 can detach from the top of the mast. In the top climber, hydraulic rams are used to adjust the slewing unit up an extra 20 feet or 6.1m. After that, the crane driver utilizes the crane to insert and bolt into position another mast part piece.