The tower crane's base is usually bolted to a huge concrete pad that provides very crucial support. The base is attached to a mast or a tower and stabilizes the crane that 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 is made of a motor and a gear that enable the crane to rotate.
Tower cranes are able to have a maximum unsupported height of 80m or 265 feet. The maximum lifting capacity of a tower crane is 16,642 kilograms or 39,690 pounds with counter weights of 20 tons. In addition, two limit switches are utilized in order to make certain that the driver does not overload the crane. There is also another safety feature called a load moment switch to ensure that the driver does not exceed the ton meter load rating. Lastly, the tower crane has a maximum reach of 70 meters or 230 feet.
There is certainly a science involved with erecting a tower crane, specially because of their extreme heights. At first, the stationary structure has to be brought to the construction site by using a big tractor-trailer rig setup. After that, a mobile crane is utilized so as to assemble the machinery part of the jib and the crane. Afterwards, these parts are connected to the mast. After that, the mobile crane adds counterweights. Forklifts and crawler cranes could be some of the other industrial equipment which is typically used to erect a crane.
Mast extensions are added to the crane when the building is erected. This is how the height of the crane could match the building's height. The crane crew uses what is known as a climbing frame or a top climber 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 is able to 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 utilizes the crane to insert and bolt into place another mast section piece.