Typically the base that is bolted into a huge concrete pad provides the crucial support for a tower crane. The base is connected to a mast or a tower and stabilizes the crane which is connected to the inside of the structure of the building. Normally, this attachment point is to an elevator shaft or to a concrete lift.
The mast of the crane is usually a triangulated lattice structure that measures 10 feet square or 0.9m2. Connected to the very top of the mast is the slewing unit. 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 kg or 39,690 pounds with counter weights of 20 tons. Moreover, two limit switches are used to be able to make certain that the operator 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 surpass the ton meter load rating. Lastly, 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 at first need to be transported to the construction site by utilizing a big tractor-trailer rig setup. After that, a mobile crane is utilized so as to assemble the machine part of the jib and the crane. These parts are then attached to the mast. The mobile crane next adds counterweights. Forklifts and crawler cranes may be some of the other industrial equipment that is typically 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 can match the building's height. The crane crew utilizes what is called a climbing frame or a top climber which fits between the top of the mast and the slewing unit. 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 utilized to adjust the slewing unit up an extra 6.1m or 20 feet. After that, the crane operator utilizes the crane to insert and bolt into place one more mast part piece.