Usually the base which is bolted into a huge concrete pad provides the essential support for a tower crane. The base is attached to a mast or a tower and stabilizes the crane that is connected to the inside of the building's structure. Often, this attachment point is to an elevator shaft or to a concrete lift.
Usually, 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 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. Additionally, two limit switches are utilized to be able to make certain that the operator does not overload the crane. There is also one more safety feature referred to as a load moment switch to make sure that the operator does not exceed the ton meter load rating. Last of all, the maximum reach of a tower crane is 70 meters or 230 feet.
Because of their extreme heights, there is a science involved to erecting a crane. The stationary structure would at first need to be brought to the construction site by using a large tractor-trailer rig setup. After that, a mobile crane is utilized so as to assemble the machine part of the crane and the jib. These sections are then connected to the mast. Then, the mobile crane adds counterweights. Forklifts and crawler cranes may be a few of the other industrial machines that is commonly used 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 known as a top climber or a climbing frame 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. Once complete, the slewing unit is able to detach from the top of the mast. In the top climber, hydraulic rams are used to adjust the slewing unit up an additional 20 feet or 6.1m. Then, the crane operator uses the crane to insert and bolt into place another mast section piece.