The tower crane's base is generally bolted to a huge concrete pad that provides really crucial support. The base is attached to a tower or a mast and stabilizes the crane that is attached 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 10 feet square or 0.9m2. The slewing unit is connected to the very top of the mast. The slewing unit consists of a motor and a gear which allows the crane to rotate.
Tower cranes may have a max unsupported height of 80m or 265 feet, while the tower crane's maximum lifting capacity is 16,642 kg or 39,690 lbs. with counter weights of 20 tons. Moreover, two limit switches are used to be able to ensure the driver does not overload the crane. There is also another safety feature known 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 70 meters or 230 feet.
Due to their extreme heights, there is a science involved to erecting a crane. The stationary structure would first need to be transported to the construction site by using a huge tractor-trailer rig setup. After that, a mobile crane is used in order to assemble the equipment portion of the crane and the jib. These parts are then attached to the mast. The mobile crane next adds counterweights. Crawler cranes and forklifts may be some of the other industrial machinery which is commonly 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 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 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. After that, the crane driver utilizes the crane to insert and bolt into position another mast part piece.