The tower crane's base is generally bolted to a big concrete pad which provides very crucial support. The base is attached to a tower or a mast and stabilizes the crane which is connected to the inside of the building's structure. Normally, this attachment point is to a concrete lift or to an elevator shaft.
Usually, the mast is a triangulated lattice structure measuring 0.9m2 or 10 feet square. The slewing unit is attached to the very top of the mast. The slewing unit consists of a gear and a motor which allows 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 pounds with counter weights of 20 tons. In addition, two limit switches are utilized to be able to make sure that the operator does not overload the crane. There is even another safety feature referred to as a load moment switch to ensure that the operator does not surpass the ton meter load rating. Last of all, the tower crane has a maximum reach of 230 feet or 70 meters.
Due to their extreme heights, there is a science involved to erecting a crane. The stationary structure would at first need to be transported to the construction site by using a big tractor-trailer rig setup. After that, 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. Then, the mobile crane adds counterweights. Forklifts and crawler cranes could be some of the other industrial equipment that is 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 is able to match the building's height. The crane crew uses what is called 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. Once complete, the slewing unit is able to detach from the top of the mast. In the top climber, hydraulic rams are used to adjust the slewing unit up an extra 6.1m or 20 feet. Then, the crane driver utilizes the crane to insert and bolt into place another mast section piece.