The base of the tower crane is usually bolted to a large concrete pad that provides really crucial support. 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. Usually, this attachment point is to an elevator shaft or to a concrete lift.
Typically, 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 enable 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. Furthermore, two limit switches are utilized in order to make certain that the operator does not overload the crane. There is also another safety feature referred to as a load moment switch to ensure that the driver does not surpass the ton meter load rating. Finally, the tower crane has a maximum reach of 230 feet or 70 meters.
Due to their extreme heights, there is a science involved to erecting a crane. The stationary structure would at first need to be brought to the construction site by utilizing a huge tractor-trailer rig setup. Next, a mobile crane is used so as to assemble the machine part of the crane and the jib. Then, these parts are connected to the mast. The mobile crane next adds counterweights. Forklifts and crawler cranes may be some of the other industrial machines which 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 top climber or a climbing frame that fits between the slewing unit and the top of the mast. 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 20 feet or 6.1m. Next, the operator of the crane uses the crane to insert and bolt into position one more mast section piece.