The tower crane's base is typically bolted to a huge concrete pad that provides very necessary support. 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. Usually, this attachment point is to an elevator shaft or to a concrete lift.
The mast of the crane is usually a triangulated lattice structure which measures 0.9m2 or 10 feet square. Attached to the very top of the mast is the slewing unit. The slewing unit is made of a motor and a gear 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 pounds with counter weights of 20 tons. Moreover, two limit switches are utilized in order to make certain that the operator does not overload the crane. There is even one more safety feature known as 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 230 feet or 70 meters.
There is certainly a science involved with erecting a tower crane, particularly because of their extreme heights. At first, the stationary structure has to be brought to the construction location by utilizing a huge tractor-trailer rig setup. Next, a mobile crane is utilized in order to assemble the machinery portion of the crane and the jib. These sections are then connected to the mast. The mobile crane then adds counterweights. Forklifts and crawler cranes can be some of the other industrial machinery 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 in order 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 position one more mast section piece.