The tower crane's base is usually 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 structure of the building. Normally, this attachment point is to a concrete lift or to an elevator shaft.
Typically, the mast is a triangulated lattice structure measuring 0.9m2 or 10 feet square. The slewing unit is attached to the very top of the mast. The slewing unit is made of a motor and a gear that allows 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 kg or 39,690 lbs. with counter weights of 20 tons. Additionally, two limit switches are used in order to ensure the driver does not overload the crane. There is also one more safety feature called a load moment switch to make certain that the driver does not surpass the ton meter load rating. Last of all, 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 first have to be transported to the construction site by using a big tractor-trailer rig setup. After that, a mobile crane is used so as to assemble the equipment portion of the jib and the crane. These sections are then connected to the mast. The mobile crane then adds counterweights. Crawler cranes and forklifts could be some of the other industrial equipment which is typically utilized to erect a crane.
Mast extensions are added to the crane as the building is erected. This is how the height of the crane could match the building's height. The crane crew uses 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. 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 extra 6.1m or 20 feet. After that, the driver of the crane utilizes the crane to insert and bolt into position another mast section piece.