Generally the base that is bolted into a big concrete pad provides the crucial support for a tower crane. The base is connected to a tower or a mast and stabilizes the crane that is attached 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 consists 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 lbs. 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 also another safety feature called a load moment switch to make sure that the operator does not exceed the ton meter load rating. Lastly, the tower crane has a maximum reach of 70 meters or 230 feet.
Because of their extreme heights, there is a science involved to erecting a crane. The stationary structure would first need to be transported to the construction site by using a huge tractor-trailer rig setup. After that, a mobile crane is used in order to assemble the equipment portion of the crane and the jib. Then, these sections are attached to the mast. The mobile crane then adds counterweights. Forklifts and crawler cranes can be a few of the other industrial machines 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 could match the building's height. The crane crew utilizes what is called a climbing frame or a top climber which 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 used to adjust the slewing unit up an extra 6.1m or 20 feet. Next, the crane operator utilizes the crane to insert and bolt into position one more mast section piece.