The base of the tower crane is typically bolted to a huge concrete pad that provides really necessary support. The base is connected to a mast or a tower and stabilizes the crane that is connected to the inside of the structure of the building. Usually, this attachment point is to a concrete lift or to an elevator shaft.
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 consists of a gear and a motor which 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 ensure the driver does not overload the crane. There is even one more safety feature called a load moment switch to ensure that the driver does not surpass 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 first have to be brought to the construction site by utilizing a huge tractor-trailer rig setup. Then, a mobile crane is utilized in order to assemble the machinery portion of the jib and the crane. These sections are then attached to the mast. The mobile crane next adds counterweights. Forklifts and crawler cranes can be a few of the other industrial machines that is usually utilized to erect a crane.
When the building is erected, mast extensions are added to the crane. This is how the crane's height 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 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 additional 6.1m or 20 feet. Next, the operator of the crane uses the crane to insert and bolt into position one more mast section piece.