Generally the base which is bolted into a big concrete pad provides the necessary support for a tower crane. The base is attached to a tower or a mast and stabilizes the crane that is connected to the inside of the structure of the building. Usually, this attachment point is to an elevator shaft or to a concrete lift.
The mast of the crane is usually a triangulated lattice structure which measures 10 feet square or 0.9m2. Connected to the very top of the mast is the slewing unit. 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 minimum lifting capacity of a tower crane is 16,642 kg or 39,690 pounds with counter weights of 20 tons. Furthermore, two limit switches are used to be able to make sure that the driver does not overload the crane. There is even one more safety feature known as a load moment switch to ensure that the driver does not exceed the ton meter load rating. Last of all, 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 transported to the construction site by using a large tractor-trailer rig setup. Then, a mobile crane is utilized so as to assemble the machine part of the crane and the jib. These sections are then attached to the mast. After that, the mobile crane adds counterweights. Forklifts and crawler cranes can be some of the other industrial equipment which is used 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 known as 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 can 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. Then, the crane driver uses the crane to insert and bolt into place one more mast section piece.