The tower crane's base is generally bolted to a big concrete pad which provides very necessary support. The base is connected to a tower or a mast and stabilizes the crane that is affixed to the inside of the structure of the building. Normally, this attachment point is to an elevator shaft or to a concrete lift.
Typically, the mast is a triangulated lattice structure measuring 10 feet square or 0.9m2. The slewing unit is attached 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 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 pounds with counter weights of 20 tons. Furthermore, two limit switches are utilized to be able to ensure the operator does not overload the crane. There is also another safety feature called a load moment switch to ensure that the operator does not surpass the ton meter load rating. Finally, the maximum reach of a tower crane is 230 feet or 70 meters.
There is definitely a science involved with erecting a tower crane, particularly because of their extreme heights. At first, the stationary structure has to be brought to the construction location by using a large tractor-trailer rig setup. Next, a mobile crane is used so as to assemble the equipment part of the crane and the jib. These sections are then connected to the mast. The mobile crane next adds counterweights. Crawler cranes and forklifts may be some of the other industrial equipment that is utilized to erect a crane.
Mast extensions are added to the crane when the building is erected. This is how the height of the crane could 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. 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 additional 6.1m or 20 feet. Then, the crane driver uses the crane to insert and bolt into position one more mast section piece.