The tower crane's base is usually 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 that is attached to the inside of the building's structure. Usually, this attachment point is to a concrete lift or to an elevator shaft.
The crane's mast is usually a triangulated lattice structure that measures 0.9m2 or 10 feet square. Attached to the very top of the mast is the slewing unit. The slewing unit consists of a motor and a gear 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 lbs. with counter weights of 20 tons. Furthermore, two limit switches are used in order to ensure the operator does not overload the crane. There is also one more safety feature called a load moment switch to ensure that the operator does not surpass the ton meter load rating. Last of all, the maximum reach of a tower crane is 70 meters or 230 feet.
Due to their extreme heights, there is a science involved to erecting a crane. The stationary structure will at first need to be brought to the construction site by using a large tractor-trailer rig setup. Then, a mobile crane is used so as to assemble the equipment portion of the crane and the jib. These parts are then attached to the mast. After that, the mobile crane adds counterweights. Crawler cranes and forklifts could be some of the other industrial machines that is usually utilized to erect a crane.
Mast extensions are added to the crane as the building is erected. This is how the height of the crane could match the building's height. The crane crew uses what is referred to as a climbing frame or a top climber which 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 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 operator utilizes the crane to insert and bolt into position another mast section piece.