Usually the base that is bolted into a large concrete pad provides the essential support for a tower crane. The base is connected to a tower or a mast and stabilizes the crane which is affixed to the inside of the structure of the building. Often, 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 that allows the crane to rotate.
Tower cranes are able to have a maximum unsupported height of 80m or 265 feet. The tower crane's maximum lifting capacity is 16,642 kilograms or 39,690 lbs. with counter weights of 20 tons. Moreover, two limit switches are utilized to be able to ensure the driver does not overload the crane. There is even another safety feature known as a load moment switch to make certain that the driver does not exceed 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 at first need to be transported to the construction site by utilizing a huge tractor-trailer rig setup. After that, a mobile crane is used so as to assemble the equipment part of the jib and the crane. Afterwards, these parts are attached to the mast. After that, the mobile crane adds counterweights. Forklifts and crawler cranes could be some of the other industrial equipment that is utilized to erect a crane.
When the building is erected, mast extensions are added to the crane. This is how the crane's height could match the building's height. The crane crew utilizes 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. When complete, the slewing unit could detach from the top of the mast. In the top climber, hydraulic rams are utilized to adjust the slewing unit up an additional 6.1m or 20 feet. Next, the driver of the crane uses the crane to insert and bolt into place another mast part piece.