Generally the base which 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 that is connected to the inside of the structure of the building. Usually, this attachment point is to a concrete lift or to an elevator shaft.
The crane's mast is usually a triangulated lattice structure which measures 0.9m2 or 10 feet square. Connected to the very top of the mast is the slewing unit. The slewing unit is made of a gear and a motor which enable 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 pounds with counter weights of 20 tons. In addition, two limit switches are utilized 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 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 certainly a science involved with erecting a tower crane, specially 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 machinery portion of the crane and the jib. Afterwards, these sections are attached to the mast. Then, the mobile crane adds counterweights. Crawler cranes and forklifts could be a few of the other industrial machinery that is commonly 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 can match the building's height. The crane crew uses what is called 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 extra 20 feet or 6.1m. After that, the driver of the crane uses the crane to insert and bolt into position another mast part piece.