The base of the tower crane is generally bolted to a huge concrete pad which provides very necessary support. The base is attached to a mast or a tower and stabilizes the crane that is connected 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 normally 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 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 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 utilized in order to ensure the operator does not overload the crane. There is even one more safety feature referred to as a load moment switch to make certain that the driver does not surpass the ton meter load rating. Lastly, 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 at first need to be brought to the construction location by utilizing a large tractor-trailer rig setup. After that, a mobile crane is utilized so as to assemble the equipment part of the crane and the jib. These sections are then connected to the mast. Then, the mobile crane adds counterweights. Forklifts and crawler cranes can be a few of the other industrial machines which is typically used to erect a crane.
Mast extensions are added to the crane as the building is erected. This is how the height of the crane can match the building's height. The crane crew utilizes what is known 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. 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 20 feet or 6.1m. Next, the operator of the crane utilizes the crane to insert and bolt into position another mast part piece.