Generally the base that is bolted into a big concrete pad provides the necessary support for a tower crane. The base is attached to a mast or a tower and stabilizes the crane which is affixed to the inside of the structure of the building. Often, this attachment point is to an elevator shaft or to a concrete lift.
Typically, the mast is a triangulated lattice structure measuring 10 feet square or 0.9m2. The slewing unit is attached to the very top of the mast. The slewing unit is made of a gear and a motor which allows the crane to rotate.
Tower cranes are able to have a maximum unsupported height of 80m or 265 feet. The maximum lifting capacity of a tower crane is 16,642 kilograms or 39,690 lbs. with counter weights of 20 tons. Moreover, two limit switches are used to be able to make sure that the driver does not overload the crane. There is even one more safety feature called a load moment switch to ensure that the operator 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 would at first need to be brought to the construction site by using a large tractor-trailer rig setup. Next, a mobile crane is utilized so as to assemble the machine portion of the crane and the jib. After that, these parts are connected to the mast. After that, the mobile crane adds counterweights. Crawler cranes and forklifts may be a few of the other industrial equipment which is used to erect a crane.
Mast extensions are added to the crane when 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 known as 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 utilized to adjust the slewing unit up an extra 6.1m or 20 feet. Next, the crane driver uses the crane to insert and bolt into place another mast section piece.