The tower crane's base is generally bolted to a huge concrete pad that provides very necessary support. The base is attached to a tower or a mast and stabilizes the crane that is affixed to the inside of the structure of the building. Usually, this attachment point is to a concrete lift or to an elevator shaft.
The crane's mast is normally a triangulated lattice structure which measures 0.9m2 or 10 feet square. Attached to the very top of the mast is the slewing unit. The slewing unit consists of a motor and a gear which enable the crane to rotate.
Tower cranes are able to have a maximum unsupported height of 80m or 265 feet. The maximum lifting capacity of a tower crane is 16,642 kg or 39,690 pounds with counter weights of 20 tons. Additionally, two limit switches are utilized to be able to make certain that the driver does not overload the crane. There is even one more safety feature known as a load moment switch to make sure that the driver does not surpass the ton meter load rating. Last of all, the maximum reach of a tower crane is 70 meters or 230 feet.
Due to their extreme heights, there is a science involved to erecting a crane. The stationary structure would at first have to be brought to the construction site by using a large tractor-trailer rig setup. After that, a mobile crane is utilized so as to assemble the machinery portion of the jib and the crane. After that, these parts are connected to the mast. The mobile crane then adds counterweights. Crawler cranes and forklifts could be a few 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 can match the building's height. The crane crew uses what is referred to as a top climber or a climbing frame that fits between the top of the mast and the slewing unit. A weight is hung on the jib by the work crew in order to balance the counterweight. Once 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 place one more mast part piece.