Typically the base that is bolted into a huge 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. Normally, this attachment point is to a concrete lift or to an elevator shaft.
The crane's mast is often 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 is made of a gear and a motor which allows the crane to rotate.
Tower cranes may have a max unsupported height of 80m or 265 feet, while the minimum lifting capacity of a tower crane is 16,642 kilograms or 39,690 lbs. with counter weights of 20 tons. In addition, two limit switches are used in order to make certain that the driver does not overload the crane. There is even another safety feature called a load moment switch to ensure that the operator does not exceed the ton meter load rating. Finally, the maximum reach of a tower crane is 70 meters or 230 feet.
Due to their extreme heights, there is a science involved to erecting a crane. The stationary structure will first have to be transported to the construction location by utilizing a big tractor-trailer rig setup. Next, a mobile crane is utilized in order to assemble the machinery portion of the jib and the crane. These parts are then attached to the mast. Afterward, the mobile crane adds counterweights. Forklifts and crawler cranes may be a few of the other industrial machinery which is typically utilized to erect a crane.
As 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 uses 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 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 utilized to adjust the slewing unit up an additional 20 feet or 6.1m. After that, the driver of the crane uses the crane to insert and bolt into position one more mast section piece.