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 connected to the inside of the structure of the building. Normally, 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 consists of a gear and a motor that enable 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 pounds with counter weights of 20 tons. Additionally, two limit switches are utilized to be able to ensure the operator does not overload the crane. There is even one more safety feature referred to as a load moment switch to make certain that the driver 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 first have to be transported to the construction site by utilizing a large tractor-trailer rig setup. Then, a mobile crane is utilized so as to assemble the equipment portion of the jib and the crane. After that, these parts are connected to the mast. The mobile crane next 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 utilizes 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. Once 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 extra 20 feet or 6.1m. After that, the operator of the crane uses the crane to insert and bolt into place another mast section piece.