The base of the tower crane is typically bolted to a huge concrete pad which provides very necessary support. The base is attached to a tower or a mast and stabilizes the crane which is attached to the inside of the building's structure. Normally, this attachment point is to an elevator shaft or to a concrete lift.
The mast of the crane is normally a triangulated lattice structure that measures 0.9m2 or 10 feet square. 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 are able to have a maximum unsupported height of 80m or 265 feet. The tower crane's maximum lifting capacity is 16,642 kilograms or 39,690 lbs. with counter weights of 20 tons. Furthermore, two limit switches are utilized to be able to make sure that the operator does not overload the crane. There is also one more safety feature referred to as a load moment switch to ensure that the operator does not exceed the ton meter load rating. Finally, the maximum reach of a tower crane is 70 meters or 230 feet.
There is definitely a science involved with erecting a tower crane, particularly because of their extreme heights. At first, the stationary structure needs to be transported to the construction site by using a big tractor-trailer rig setup. Next, a mobile crane is used in order to assemble the machinery part of the jib and the crane. After that, these sections are attached to the mast. Afterward, the mobile crane adds counterweights. Forklifts and crawler cranes could be some of the other industrial machines that is commonly used to erect a crane.
When the building is erected, mast extensions are added to the crane. This is how the crane's height is able to match the building's height. The crane crew uses what is referred to as a top climber or a climbing frame which fits between the top of the mast and the slewing unit. 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 6.1m or 20 feet. Next, the operator of the crane utilizes the crane to insert and bolt into place another mast part piece.