Generally the base that is bolted into a huge concrete pad provides the crucial support for a tower crane. The base is attached to a mast or a tower and stabilizes the crane which is affixed to the inside of the structure of the building. Normally, this attachment point is to an elevator shaft or to a concrete lift.
The mast of the crane is usually a triangulated lattice structure which measures 10 feet square or 0.9m2. Connected to the very top of the mast is the slewing unit. The slewing unit consists of a motor and a gear that enable the crane to rotate.
Tower cranes are able to have a maximum unsupported height of 80m or 265 feet. The tower crane's maximum lifting capacity is 16,642 kg or 39,690 pounds with counter weights of 20 tons. Moreover, two limit switches are used in order to make sure that the driver does not overload the crane. There is even another safety feature referred to as a load moment switch to ensure that the driver does not exceed the ton meter load rating. Last of all, the tower crane has a maximum reach of 70 meters or 230 feet.
There is definitely a science involved with erecting a tower crane, particularly because of their extreme heights. First, the stationary structure needs to be transported to the construction site by using a large tractor-trailer rig setup. Next, a mobile crane is utilized in order to assemble the machine portion of the jib and the crane. These parts are then attached to the mast. Then, the mobile crane adds counterweights. Crawler cranes and forklifts could be some of the other industrial machines that is 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 could match the building's height. The crane crew uses what is referred to as a climbing frame or a top climber that 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 is able to 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. After that, the crane operator uses the crane to insert and bolt into position one more mast part piece.