The base of the tower crane is typically bolted to a big concrete pad that provides really crucial support. 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. Usually, this attachment point is to a concrete lift or to an elevator shaft.
Generally, 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 gear and a motor 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 kilograms or 39,690 lbs. 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 another safety feature known as a load moment switch to make certain that the driver does not surpass the ton meter load rating. Lastly, the maximum reach of a tower crane is 70 meters or 230 feet.
There is definitely a science involved with erecting a tower crane, particularly because of their extreme heights. First, the stationary structure has to be transported to the construction site by utilizing a large tractor-trailer rig setup. After that, a mobile crane is utilized in order to assemble the equipment part of the crane and the jib. Afterwards, these parts are attached to the mast. Then, the mobile crane adds counterweights. Crawler cranes and forklifts could be some of the other industrial equipment that is usually used to erect a crane.
Mast extensions are added to the crane as 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 called a top climber or a climbing frame that 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. 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. After that, the crane driver utilizes the crane to insert and bolt into position another mast section piece.