Usually the base which is bolted into a big concrete pad provides the necessary 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 building's structure. Often, this attachment point is to a concrete lift or to an elevator shaft.
Typically, the mast is a triangulated lattice structure measuring 10 feet square or 0.9m2. The slewing unit is connected to the very top of the mast. The slewing unit is made 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 kilograms or 39,690 lbs. with counter weights of 20 tons. In addition, two limit switches are utilized in order 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 driver does not exceed the ton meter load rating. Finally, the maximum reach of a tower crane is 230 feet or 70 meters.
There is definitely a science involved with erecting a tower crane, particularly due to their extreme heights. At first, the stationary structure needs to be transported to the construction location by using a large tractor-trailer rig setup. Next, a mobile crane is utilized in order to assemble the equipment part of the crane and the jib. Then, these parts are connected to the mast. Next, the mobile crane adds counterweights. Forklifts and crawler cranes may be a few of the other industrial machinery that is 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 utilizes what is referred to 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 so as to balance the counterweight. Once complete, the slewing unit is able to 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. Then, the driver of the crane utilizes the crane to insert and bolt into place one more mast part piece.