The base of the tower crane is typically bolted to a large concrete pad which provides really necessary support. The base is attached to a tower or a mast and stabilizes the crane which is connected to the inside of the building's structure. Normally, this attachment point is to an elevator shaft or to a concrete lift.
Usually, 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 consists of a motor and a gear that 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 pounds with counter weights of 20 tons. In addition, two limit switches are utilized in order to ensure the driver does not overload the crane. There is even one more safety feature called a load moment switch to make certain that the driver does not exceed the ton meter load rating. Finally, the maximum reach of a tower crane is 70 meters or 230 feet.
There is certainly a science involved with erecting a tower crane, especially due to their extreme heights. First, the stationary structure has to be brought to the construction location by using a big tractor-trailer rig setup. After that, a mobile crane is used in order to assemble the machine portion of the jib and the crane. These parts are then connected to the mast. The mobile crane then adds counterweights. Forklifts and crawler cranes can be some of the other industrial machines that is utilized 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 uses what is known as a top climber or a climbing frame that 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 is able to detach from the top of the mast. In the top climber, hydraulic rams are used to adjust the slewing unit up an additional 6.1m or 20 feet. After that, the crane driver uses the crane to insert and bolt into place another mast part piece.