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 tower or a mast and stabilizes the crane that is connected to the inside of the building's structure. Usually, this attachment point is to an elevator shaft or to a concrete lift.
Usually, 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 consists of a motor and a gear that allows the crane to rotate.
Tower cranes are able to have a maximum unsupported height of 80m or 265 feet. The tower crane's maximum lifting capacity is 16,642 kilograms or 39,690 lbs. with counter weights of 20 tons. Moreover, two limit switches are used in order to make sure that the operator does not overload the crane. There is even one more safety feature known as a load moment switch to make certain that the driver does not exceed the ton meter load rating. Finally, the maximum reach of a tower crane is 230 feet or 70 meters.
There is certainly a science involved with erecting a tower crane, particularly due to their extreme heights. First, the stationary structure needs to be transported to the construction location by utilizing a large tractor-trailer rig setup. Then, a mobile crane is utilized so as to assemble the machine part of the jib and the crane. These sections are then connected to the mast. The mobile crane then adds counterweights. Forklifts and crawler cranes can be a few 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 uses what is called a top climber or a climbing frame which fits between the top of the mast and the slewing unit. A weight is hung on the jib by the work crew in order 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 extra 20 feet or 6.1m. Then, the crane driver utilizes the crane to insert and bolt into position one more mast part piece.