The tower crane's base is typically bolted to a large concrete pad that provides very crucial support. The base is connected to a tower or a mast and stabilizes the crane which is affixed to the inside of the structure of the building. Usually, this attachment point is to a concrete lift or to an elevator shaft.
The crane's mast is often a triangulated lattice structure that measures 0.9m2 or 10 feet square. Attached to the very top of the mast is the slewing unit. The slewing unit is made of a gear and a motor which allows 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 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 also another safety feature called a load moment switch to ensure that the operator does not exceed the ton meter load rating. Last of all, the maximum reach of a tower crane is 230 feet or 70 meters.
There is certainly a science involved with erecting a tower crane, especially due to their extreme heights. At first, the stationary structure has to be transported to the construction location by using a large tractor-trailer rig setup. After that, a mobile crane is utilized in order to assemble the machine portion of the crane and the jib. These sections are then connected to the mast. The mobile crane next adds counterweights. Crawler cranes and forklifts could be a few of the other industrial equipment which is usually 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 uses what is called a climbing frame or a top climber that 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 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. After that, the driver of the crane uses the crane to insert and bolt into position another mast part piece.