The base of the tower crane is typically bolted to a huge concrete pad which provides very necessary support. The base is connected to a mast or a tower and stabilizes the crane which is attached to the inside of the structure of the building. Normally, this attachment point is to an elevator shaft or to a concrete lift.
The mast of the crane 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 is made 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 tower crane's maximum lifting capacity is 16,642 kilograms or 39,690 pounds with counter weights of 20 tons. Additionally, two limit switches are used in order to ensure the operator does not overload the crane. There is also one more safety feature called a load moment switch to make sure that the driver does not surpass the ton meter load rating. Last of all, the tower crane has a maximum reach of 230 feet or 70 meters.
There is definitely a science involved with erecting a tower crane, especially due to their extreme heights. First, the stationary structure has to be brought to the construction location by utilizing a large tractor-trailer rig setup. Then, a mobile crane is utilized in order to assemble the equipment part of the crane and the jib. Afterwards, these parts are attached to the mast. After that, the mobile crane adds counterweights. Forklifts and crawler cranes could be some of the other industrial machines that is utilized to erect a crane.
Mast extensions are added to the crane when the building is erected. This is how the height of the crane 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. When 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 extra 20 feet or 6.1m. Next, the driver of the crane utilizes the crane to insert and bolt into position another mast part piece.