The base of the tower crane is generally bolted to a big concrete pad that provides very crucial support. The base is attached to a mast or a tower and stabilizes the crane that is affixed to the inside of the structure of the building. Normally, this attachment point is to a concrete lift or to an elevator shaft.
Generally, the mast is a triangulated lattice structure measuring 10 feet square or 0.9m2. The slewing unit is connected to the very top of the mast. The slewing unit consists 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 tower crane's maximum lifting capacity is 16,642 kilograms or 39,690 lbs. with counter weights of 20 tons. Furthermore, two limit switches are used in order to ensure the driver does not overload the crane. There is even another safety feature called a load moment switch to ensure that the driver does not exceed the ton meter load rating. Finally, the maximum reach of a tower crane is 70 meters or 230 feet.
Due to their extreme heights, there is a science involved to erecting a crane. The stationary structure would first need to be transported to the construction location by using a large tractor-trailer rig setup. Then, a mobile crane is used so as to assemble the equipment part of the crane and the jib. These sections are then connected to the mast. The mobile crane then adds counterweights. Forklifts and crawler cranes could be a few of the other industrial machinery that is typically utilized to erect a crane.
When 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 called a climbing frame or a top climber that fits between the top of the mast and the slewing unit. 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 utilized to adjust the slewing unit up an additional 6.1m or 20 feet. Next, the crane driver uses the crane to insert and bolt into position one more mast part piece.