Typically the base that is bolted into a huge concrete pad provides the essential support for a tower crane. The base is connected to a mast or a tower and stabilizes the crane that is affixed to the inside of the structure of the building. Usually, this attachment point is to an elevator shaft or to a concrete lift.
The mast of the crane is usually a triangulated lattice structure that measures 0.9m2 or 10 feet square. Attached to the very top of the mast is the slewing unit. The slewing unit is made of a motor and a gear 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. Additionally, two limit switches are utilized to be able to ensure the driver does not overload the crane. There is also another safety feature called a load moment switch to make certain that the operator does not exceed the ton meter load rating. Last of all, the maximum reach of a tower crane is 70 meters or 230 feet.
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 using a huge tractor-trailer rig setup. Next, a mobile crane is utilized in order to assemble the machine part of the crane and the jib. These parts are then attached to the mast. Afterward, the mobile crane adds counterweights. Forklifts and crawler cranes can be a few of the other industrial machines which is typically 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 in order 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 utilized to adjust the slewing unit up an additional 6.1m or 20 feet. Then, the driver of the crane utilizes the crane to insert and bolt into position one more mast section piece.