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 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 is made of a gear and a motor which allows 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. In addition, two limit switches are utilized to be able to ensure the driver does not overload the crane. There is even one more safety feature called a load moment switch to make sure that the operator does not exceed the ton meter load rating. Finally, the maximum reach of a tower crane is 230 feet or 70 meters.
Due to their extreme heights, there is a science involved to erecting a crane. The stationary structure will first need to be transported 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 part of the crane and the jib. These sections are then connected to the mast. The mobile crane then adds counterweights. Forklifts and crawler cranes could be a few of the other industrial machinery which is usually used 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 utilizes 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. Once 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 additional 6.1m or 20 feet. Then, the driver of the crane uses the crane to insert and bolt into position another mast part piece.