Generally the base that is bolted into a huge concrete pad provides the necessary support for a tower crane. The base is connected to a tower or a mast and stabilizes the crane that is affixed to the inside of the building's structure. Normally, this attachment point is to an elevator shaft or to a concrete lift.
Generally, 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 is made of a motor and a gear that 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 pounds with counter weights of 20 tons. Furthermore, two limit switches are used to be able to ensure the operator does not overload the crane. There is also another safety feature referred to as a load moment switch to make sure that the driver does not surpass the ton meter load rating. Lastly, the tower crane has a maximum reach of 230 feet or 70 meters.
Because of 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 large tractor-trailer rig setup. After that, a mobile crane is used so as to assemble the equipment portion of the jib and the crane. After that, these parts are connected to the mast. After that, the mobile crane adds counterweights. Forklifts and crawler cranes may be a few of the other industrial equipment that is utilized to erect a crane.
Mast extensions are added to the crane when 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 top climber or a climbing frame that 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 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 additional 6.1m or 20 feet. After that, the crane driver utilizes the crane to insert and bolt into place another mast part piece.