Usually the base which is bolted into a large concrete pad provides the crucial support for a tower crane. The base is attached to a mast or a tower and stabilizes the crane that is affixed to the inside of the building's structure. Normally, this attachment point is to a concrete lift or to an elevator shaft.
The crane's mast is often a triangulated lattice structure that measures 10 feet square or 0.9m2. Connected to the very top of the mast is the slewing unit. The slewing unit consists 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 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 referred to as a load moment switch to make sure that the operator does not exceed the ton meter load rating. Lastly, the maximum reach of a tower crane is 70 meters or 230 feet.
There is certainly a science involved with erecting a tower crane, specially due to their extreme heights. At first, the stationary structure has to be transported to the construction location by utilizing a huge tractor-trailer rig setup. Then, a mobile crane is used so as to assemble the equipment part of the crane and the jib. These parts are then connected to the mast. Then, the mobile crane adds counterweights. Forklifts and crawler cranes may be some of the other industrial machines that is typically 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 utilizes what is called a climbing frame or a top climber which 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 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 extra 20 feet or 6.1m. After that, the crane driver utilizes the crane to insert and bolt into position one more mast part piece.