The base of the tower crane is generally bolted to a big concrete pad which provides very necessary support. The base is connected to a mast or a tower and stabilizes the crane which is attached to the inside of the building's structure. Usually, 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 motor and a gear which allows the crane to rotate.
Tower cranes may have a max unsupported height of 80m or 265 feet, while the tower crane's maximum lifting capacity is 16,642 kilograms or 39,690 pounds with counter weights of 20 tons. Furthermore, two limit switches are utilized in order to make sure that the driver does not overload the crane. There is also one more safety feature referred to as a load moment switch to make certain that the driver does not surpass the ton meter load rating. Lastly, the tower crane has a maximum reach of 230 feet or 70 meters.
There is certainly a science involved with erecting a tower crane, especially because of their extreme heights. At first, the stationary structure has to be transported to the construction site by utilizing a large tractor-trailer rig setup. Then, a mobile crane is used in order to assemble the machinery part of the crane and the jib. These sections are then attached to the mast. The mobile crane next adds counterweights. Forklifts and crawler cranes could be a few of the other industrial equipment which is commonly utilized to erect a crane.
Mast extensions are added to the crane as the building is erected. This is how the height of the crane can match the building's height. The crane crew uses what is known as 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 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 extra 20 feet or 6.1m. Next, the operator of the crane uses the crane to insert and bolt into place one more mast section piece.