The tower crane's base is typically bolted to a large concrete pad which provides really crucial support. The base is attached to a tower or a mast and stabilizes the crane which is attached to the inside of the structure of the building. Usually, this attachment point is to a concrete lift or to an elevator shaft.
Typically, 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 is made 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 maximum lifting capacity of a tower crane is 16,642 kg or 39,690 pounds with counter weights of 20 tons. Additionally, two limit switches are used in order to make certain that the operator does not overload the crane. There is even another safety feature known as 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 230 feet or 70 meters.
There is certainly a science involved with erecting a tower crane, specially due to their extreme heights. At first, the stationary structure needs 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 machine part of the jib and the crane. These parts are then connected to the mast. Afterward, the mobile crane adds counterweights. Forklifts and crawler cranes could be a few of the other industrial equipment which is commonly used 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 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 in order to balance the counterweight. Once complete, the slewing unit could 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 place another mast section piece.