The tower crane's base is usually bolted to a large concrete pad which provides very crucial support. The base is attached to a mast or a tower and stabilizes the crane that is affixed to the inside of the building's structure. Often, this attachment point is to an elevator shaft or to a concrete lift.
Typically, the mast is a triangulated lattice structure measuring 0.9m2 or 10 feet square. The slewing unit is connected to the very top of the mast. The slewing unit consists of a motor and a gear which allows 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 lbs. with counter weights of 20 tons. Moreover, two limit switches are used to be able to ensure the operator does not overload the crane. There is also 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 tower crane has a maximum reach of 70 meters or 230 feet.
Because of their extreme heights, there is a science involved to erecting a crane. The stationary structure will first have to be brought to the construction site by using a large tractor-trailer rig setup. Then, a mobile crane is utilized so as to assemble the equipment part of the jib and the crane. These parts are then connected to the mast. Next, the mobile crane adds counterweights. Forklifts and crawler cranes may be a few of the other industrial machines that is commonly utilized to erect a crane.
When 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 utilizes 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 utilized to adjust the slewing unit up an additional 6.1m or 20 feet. Next, the crane driver utilizes the crane to insert and bolt into position one more mast part piece.