The tower crane's base is typically bolted to a large concrete pad which provides very crucial support. The base is connected to a mast or a tower and stabilizes the crane which is attached to the inside of the structure of the building. Normally, this attachment point is to a concrete lift or to an elevator shaft.
Generally, 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 consists of a motor and a gear which allows the crane to rotate.
Tower cranes may have a max unsupported height of 80m or 265 feet, while 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 utilized 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 make sure that the operator does not surpass the ton meter load rating. Last of all, the maximum reach of a tower crane is 230 feet or 70 meters.
There is certainly a science involved with erecting a tower crane, particularly due to their extreme heights. At first, the stationary structure has to be brought to the construction location by using a big tractor-trailer rig setup. After that, a mobile crane is utilized so as to assemble the machine portion of the crane and the jib. Afterwards, these parts are connected to the mast. After that, the mobile crane adds counterweights. Crawler cranes and forklifts can be some of the other industrial machinery that is 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 climbing frame or a top climber 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. When complete, the slewing unit can 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. Next, the driver of the crane uses the crane to insert and bolt into place another mast section piece.