The base of the tower crane is typically bolted to a huge concrete pad that provides very necessary support. The base is attached to a mast or a tower and stabilizes the crane which is attached to the inside of the structure of the building. Usually, this attachment point is to a concrete lift or to an elevator shaft.
Typically, 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 enable 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 in order to ensure the operator does not overload the crane. There is also another safety feature known as a load moment switch to ensure that the driver does not surpass the ton meter load rating. Last of all, the tower crane has a maximum reach of 70 meters or 230 feet.
There is definitely a science involved with erecting a tower crane, especially because of their extreme heights. At first, the stationary structure has to be brought to the construction location by utilizing a huge tractor-trailer rig setup. After that, a mobile crane is used so as to assemble the equipment portion of the jib and the crane. These sections are then connected to the mast. Then, the mobile crane adds counterweights. Crawler cranes and forklifts can be a few of the other industrial machinery which is utilized to erect a crane.
As 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 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 so as to balance the counterweight. Once complete, the slewing unit could 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 crane operator utilizes the crane to insert and bolt into place one more mast section piece.