The base of the tower crane is typically bolted to a large concrete pad that provides very crucial support. The base is attached to a tower or a mast and stabilizes the crane that is affixed to the inside of the structure of the building. Usually, this attachment point is to an elevator shaft or to a concrete lift.
The crane's mast is normally a triangulated lattice structure which measures 10 feet square or 0.9m2. Connected to the very top of the mast is the slewing unit. The slewing unit is made of a gear and a motor which 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 kg or 39,690 pounds with counter weights of 20 tons. Additionally, two limit switches are utilized to be able to ensure 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 surpass the ton meter load rating. Finally, the maximum reach of a tower crane is 230 feet or 70 meters.
Because of their extreme heights, there is a science involved to erecting a crane. The stationary structure would at first have to be brought to the construction location by using a big tractor-trailer rig setup. Then, a mobile crane is utilized in order to assemble the equipment part of the jib and the crane. Afterwards, these parts are attached to the mast. The mobile crane next adds counterweights. Crawler cranes and forklifts may be some of the other industrial equipment which is used to erect a crane.
As the building is erected, mast extensions are added to the crane. This is how the crane's height is able to match the building's height. The crane crew uses what is called a top climber or a climbing frame 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 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 operator utilizes the crane to insert and bolt into place another mast part piece.