The base of the tower crane is generally bolted to a large concrete pad which provides really necessary support. 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. Normally, this attachment point is to an elevator shaft or to a concrete lift.
Usually, 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 consists 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 pounds with counter weights of 20 tons. In addition, two limit switches are used to be able to make sure that the driver does not overload the crane. There is even 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 maximum reach of a tower crane is 230 feet or 70 meters.
Due to their extreme heights, there is a science involved to erecting a crane. The stationary structure would first have to be brought to the construction site by utilizing a huge tractor-trailer rig setup. After that, a mobile crane is used so as to assemble the machine part of the jib and the crane. Afterwards, these sections are connected to the mast. After that, the mobile crane adds counterweights. Forklifts and crawler cranes could be a few of the other industrial machines that is utilized to erect a crane.
Mast extensions are added to the crane as the building is erected. This is how the height of the crane could 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 in order 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 6.1m or 20 feet. Then, the driver of the crane utilizes the crane to insert and bolt into position another mast part piece.