Generally the base which is bolted into a large concrete pad provides the necessary support for a tower crane. The base is connected to a mast or a tower and stabilizes the crane which is affixed to the inside of the building's structure. Normally, this attachment point is to a concrete lift or to an elevator shaft.
Typically, the mast is a triangulated lattice structure measuring 0.9m2 or 10 feet square. The slewing unit is attached to the very top of the mast. The slewing unit is made of a gear and a motor which 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 kg or 39,690 pounds with counter weights of 20 tons. Additionally, two limit switches are used to be able to ensure the operator does not overload the crane. There is even another safety feature called a load moment switch to make sure that the driver does not surpass the ton meter load rating. Lastly, the tower crane has a maximum reach of 230 feet or 70 meters.
There is definitely a science involved with erecting a tower crane, particularly because of their extreme heights. At first, the stationary structure needs to be transported to the construction site by using a huge tractor-trailer rig setup. After that, a mobile crane is utilized so as 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. Forklifts and crawler cranes can be some of the other industrial equipment which is usually used 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 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 in order to balance the counterweight. Once 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 20 feet or 6.1m. After that, the operator of the crane uses the crane to insert and bolt into position one more mast section piece.