Generally the base that is bolted into a big concrete pad provides the essential support for a tower crane. The base is attached to a mast or a tower and stabilizes the crane that is attached to the inside of the building's structure. Often, 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 motor and a gear which enable 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 kilograms or 39,690 pounds with counter weights of 20 tons. Moreover, two limit switches are utilized in order to make certain that the driver does not overload the crane. There is even one more safety feature known as a load moment switch to ensure that the driver does not surpass the ton meter load rating. Lastly, 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 because of their extreme heights. At first, the stationary structure has to be transported to the construction location by utilizing a large tractor-trailer rig setup. Then, a mobile crane is used so as to assemble the machine portion of the jib and the crane. After that, these sections are attached to the mast. The mobile crane next adds counterweights. Forklifts and crawler cranes can be some of the other industrial machines which is used to erect a crane.
As the building is erected, mast extensions are added to the crane. This is how the crane's height is able to match the building's height. The crane crew utilizes what is called a climbing frame or a top climber that 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. Once complete, the slewing unit can detach from the top of the mast. In the top climber, hydraulic rams are used to adjust the slewing unit up an additional 20 feet or 6.1m. Then, the operator of the crane utilizes the crane to insert and bolt into place one more mast part piece.