The tower crane's base is usually bolted to a huge concrete pad which provides very necessary support. The base is connected 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.
Usually, 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 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 pounds with counter weights of 20 tons. In addition, two limit switches are used to be able to make certain that the operator does not overload the crane. There is also another safety feature called 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 230 feet or 70 meters.
Due to their extreme heights, there is a science involved to erecting a crane. The stationary structure would first need to be transported to the construction site by utilizing a large tractor-trailer rig setup. After that, a mobile crane is used so as to assemble the machine portion of the jib and the crane. Then, these sections are attached to the mast. Afterward, the mobile crane adds counterweights. Crawler cranes and forklifts may be a few of the other industrial machinery that 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 could match the building's height. The crane crew utilizes what is known as 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 in order to balance the counterweight. Once 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 operator of the crane utilizes the crane to insert and bolt into place another mast part piece.