Typically the base that is bolted into a big concrete pad provides the crucial support for a tower crane. The base is attached to a tower or a mast and stabilizes the crane that is affixed to the inside of the building's structure. Normally, this attachment point is to an elevator shaft or to a concrete lift.
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 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 kg or 39,690 lbs. with counter weights of 20 tons. Additionally, two limit switches are utilized in order to make certain that 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. 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 will at first have to be transported to the construction location by using a large tractor-trailer rig setup. Then, a mobile crane is used in order to assemble the machine part of the crane and the jib. These parts are then attached to the mast. Next, the mobile crane adds counterweights. Forklifts and crawler cranes can be some of the other industrial machinery that is typically used to erect a crane.
As the building is erected, mast extensions are added to the crane. This is how the crane's height can 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 20 feet or 6.1m. Next, the operator of the crane uses the crane to insert and bolt into position one more mast part piece.