The tower crane's base is typically bolted to a big concrete pad which provides very necessary support. The base is attached to a mast or a tower and stabilizes the crane which is attached to the inside of the structure of the building. Usually, this attachment point is to a concrete lift or to an elevator shaft.
Generally, 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 is made of a motor and a gear which 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 lbs. with counter weights of 20 tons. Moreover, two limit switches are used in order to ensure the driver 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 exceed the ton meter load rating. Lastly, the tower crane has a maximum reach of 70 meters or 230 feet.
Due to their extreme heights, there is a science involved to erecting a crane. The stationary structure would at first need to be brought to the construction site by using a big tractor-trailer rig setup. Next, a mobile crane is used in order to assemble the machinery portion of the crane and the jib. These sections are then connected to the mast. After that, the mobile crane adds counterweights. Crawler cranes and forklifts could be a few of the other industrial equipment which is usually 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 can match the building's height. The crane crew utilizes what is called a top climber or a climbing frame which fits between the slewing unit and the top of the mast. A weight is hung on the jib by the work crew so as 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 additional 20 feet or 6.1m. Next, the operator of the crane utilizes the crane to insert and bolt into place one more mast part piece.