Generally the base that is bolted into a big concrete pad provides the crucial support for a tower crane. The base is attached to a mast or a tower and stabilizes the crane which is attached to the inside of the building's structure. Usually, this attachment point is to an elevator shaft or to a concrete lift.
The crane's mast is normally a triangulated lattice structure which 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 gear and a motor that allows 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 kg or 39,690 lbs. with counter weights of 20 tons. Moreover, two limit switches are utilized in order to ensure the driver does not overload the crane. There is even one more safety feature referred to as a load moment switch to make certain that the driver does not surpass the ton meter load rating. Lastly, the tower crane has a maximum reach of 70 meters or 230 feet.
There is certainly a science involved with erecting a tower crane, especially due to their extreme heights. At first, the stationary structure has to be transported to the construction site by using a huge tractor-trailer rig setup. Then, a mobile crane is used so as to assemble the machine portion of the jib and the crane. These parts are then attached to the mast. The mobile crane then adds counterweights. Forklifts and crawler cranes may be a few of the other industrial machinery which is utilized to erect a crane.
When the building is erected, mast extensions are added to the crane. This is how the crane's height could match the building's height. The crane crew uses what is known as 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. 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 additional 20 feet or 6.1m. After that, the operator of the crane utilizes the crane to insert and bolt into position another mast part piece.