Typically the base that is bolted into a big concrete pad provides the necessary support for a tower crane. The base is connected to a mast or a tower and stabilizes the crane which is affixed to the inside of the building's structure. Normally, this attachment point is to a concrete lift or to an elevator shaft.
The crane's mast is normally a triangulated lattice structure which measures 10 feet square or 0.9m2. Attached to the very top of the mast is the slewing unit. The slewing unit consists of a gear and a motor which allows the crane to rotate.
Tower cranes are able to have a maximum unsupported height of 80m or 265 feet. The maximum lifting capacity of a tower crane is 16,642 kilograms or 39,690 pounds with counter weights of 20 tons. In addition, two limit switches are used in order to make sure that the driver does not overload the crane. There is even one more safety feature called a load moment switch to make sure that the operator does not surpass the ton meter load rating. Lastly, 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 will at first need to be brought to the construction site by using a large tractor-trailer rig setup. After that, a mobile crane is used in order to assemble the equipment part of the jib and the crane. After that, these sections are connected to the mast. Next, the mobile crane adds counterweights. Crawler cranes and forklifts can be a few 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 could match the building's height. The crane crew utilizes what is referred to as a climbing frame or a top climber which 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. When 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 extra 20 feet or 6.1m. Then, the driver of the crane uses the crane to insert and bolt into position one more mast part piece.