Typically the base which is bolted into a large concrete pad provides the crucial support for a tower crane. 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. Normally, 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 that enable 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. Moreover, two limit switches are utilized in order to make sure that the driver does not overload the crane. There is also one more safety feature called a load moment switch to ensure that the operator does not surpass the ton meter load rating. Lastly, the tower crane has a maximum reach of 70 meters or 230 feet.
Due to their extreme heights, there is a science involved to erecting a crane. The stationary structure would at first have to be brought to the construction location by utilizing a large tractor-trailer rig setup. Next, a mobile crane is utilized in order to assemble the equipment 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 some of the other industrial machines that is utilized to erect a crane.
As the building is erected, mast extensions are added to the crane. This is how the crane's height can match the building's height. The crane crew uses what is known as a climbing frame or a top climber 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. When complete, the slewing unit can detach from the top of the mast. In the top climber, hydraulic rams are used to adjust the slewing unit up an additional 6.1m or 20 feet. Then, the operator of the crane uses the crane to insert and bolt into place another mast section piece.