Usually the base that is bolted into a large 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 connected to the inside of the structure of the building. Normally, this attachment point is to a concrete lift or to an elevator shaft.
The mast of the crane is often a triangulated lattice structure that 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 motor and a gear that enable 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. In addition, two limit switches are utilized to be able to ensure the operator does not overload the crane. There is even another safety feature called a load moment switch to make sure that the driver does not surpass the ton meter load rating. Last of all, the tower crane has a maximum reach of 230 feet or 70 meters.
Due to their extreme heights, there is a science involved to erecting a crane. The stationary structure will at first have to be transported to the construction site by using a large tractor-trailer rig setup. After that, a mobile crane is used in order to assemble the equipment part of the crane and the jib. Afterwards, these parts are connected to the mast. The mobile crane next adds counterweights. Forklifts and crawler cranes can be a few of the other industrial machines which is usually used to erect a crane.
When the building is erected, mast extensions are added to the crane. This is how the crane's height can match the building's height. The crane crew utilizes what is known as a top climber or a climbing frame which fits between the slewing unit and the top of the mast. A weight is hung on the jib by the work crew in order 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 crane driver uses the crane to insert and bolt into position another mast section piece.