Usually the base which 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 attached to the inside of the structure of the building. Usually, 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 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 kilograms or 39,690 pounds with counter weights of 20 tons. Moreover, two limit switches are utilized in order to ensure the operator does not overload the crane. There is even another safety feature called a load moment switch to make sure that the driver does not exceed the ton meter load rating. Finally, the tower crane has a maximum reach of 70 meters or 230 feet.
Because of their extreme heights, there is a science involved to erecting a crane. The stationary structure will first have to be brought to the construction site by utilizing 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 sections are then connected to the mast. The mobile crane next adds counterweights. Crawler cranes and forklifts can be a few of the other industrial machines which is typically utilized to erect a crane.
As 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 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 could detach from the top of the mast. In the top climber, hydraulic rams are utilized to adjust the slewing unit up an extra 20 feet or 6.1m. Next, the driver of the crane uses the crane to insert and bolt into place one more mast section piece.