The tower crane's base is generally bolted to a big concrete pad that provides really crucial support. The base is attached to a mast or a tower and stabilizes the crane which is affixed to the inside of the building's structure. Normally, this attachment point is to an elevator shaft or to a concrete lift.
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 gear and a motor that allows the crane to rotate.
Tower cranes are able to have a maximum unsupported height of 80m or 265 feet. The maximum lifting capacity of a tower crane is 16,642 kg or 39,690 lbs. with counter weights of 20 tons. Moreover, two limit switches are utilized to be able to ensure the driver does not overload the crane. There is even one more safety feature called a load moment switch to ensure that the operator does not exceed the ton meter load rating. Finally, the tower crane has a maximum reach of 230 feet or 70 meters.
Because of their extreme heights, there is a science involved to erecting a crane. The stationary structure would at first have to be transported to the construction site by utilizing a large tractor-trailer rig setup. Then, a mobile crane is used in order to assemble the machine portion of the crane and the jib. These sections are then connected to the mast. Next, the mobile crane adds counterweights. Crawler cranes and forklifts could be a few of the other industrial machinery which is used 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 which fits between the top of the mast and the slewing unit. A weight is hung on the jib by the work crew so as to balance the counterweight. When complete, the slewing unit could 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 crane operator utilizes the crane to insert and bolt into position one more mast section piece.