Generally 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 attached to the inside of the structure of the building. Normally, this attachment point is to a concrete lift or to an elevator shaft.
The mast of the crane is often 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 enable 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. Furthermore, two limit switches are utilized to be able to make certain that the driver does not overload the crane. There is even one more safety feature called a load moment switch to make sure that the driver does not exceed the ton meter load rating. Finally, the maximum reach of a tower crane is 230 feet or 70 meters.
Because of their extreme heights, there is a science involved to erecting a crane. The stationary structure will at first have to be transported to the construction location by utilizing a large tractor-trailer rig setup. Then, a mobile crane is utilized so as to assemble the machinery part of the jib and the crane. Then, these parts are connected to the mast. Next, the mobile crane adds counterweights. Crawler cranes and forklifts could be a few of the other industrial machinery which is utilized to erect a crane.
As the building is erected, mast extensions are added to the crane. This is how the crane's height can match the building's height. The crane crew utilizes what is referred to as a climbing frame or a top climber 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 can detach from the top of the mast. In the top climber, hydraulic rams are utilized to adjust the slewing unit up an additional 20 feet or 6.1m. After that, the crane operator uses the crane to insert and bolt into place one more mast section piece.