Generally the base which is bolted into a big concrete pad provides the essential support for a tower crane. 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.
The mast of the crane is often a triangulated lattice structure that measures 0.9m2 or 10 feet square. Connected 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 minimum lifting capacity of a tower crane is 16,642 kilograms or 39,690 lbs. with counter weights of 20 tons. Moreover, two limit switches are utilized to be able to ensure the driver does not overload the crane. There is also another safety feature referred to as a load moment switch to ensure that the operator does not surpass the ton meter load rating. Last of all, the tower crane has a maximum reach of 70 meters or 230 feet.
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 using a huge tractor-trailer rig setup. After that, a mobile crane is utilized so as to assemble the machinery portion of the jib and the crane. After that, these parts are attached to the mast. Then, the mobile crane adds counterweights. Crawler cranes and forklifts could be a few of the other industrial machines that is used to erect a crane.
When the building is erected, mast extensions are added to the crane. This is how the crane's height could 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 so as to balance the counterweight. Once complete, the slewing unit can detach from the top of the mast. In the top climber, hydraulic rams are used to adjust the slewing unit up an additional 6.1m or 20 feet. Then, the driver of the crane uses the crane to insert and bolt into place another mast section piece.