Usually the base which is bolted into a huge concrete pad provides the crucial support for a tower crane. 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 crane's mast is often a triangulated lattice structure which measures 10 feet square or 0.9m2. Attached to the very top of the mast is the slewing unit. The slewing unit is made of a gear and a motor that enable the crane to rotate.
Tower cranes are able to have a maximum unsupported height of 80m or 265 feet. The maximum lifting capacity of a tower crane is 16,642 kilograms or 39,690 pounds with counter weights of 20 tons. Moreover, two limit switches are utilized in order to make sure that the operator does not overload the crane. There is also another safety feature known as a load moment switch to make sure that the driver does not exceed the ton meter load rating. Last of all, the tower crane has a maximum reach of 230 feet or 70 meters.
Due to their extreme heights, there is a science involved to erecting a crane. The stationary structure would at first need to be transported to the construction site by utilizing a huge tractor-trailer rig setup. Next, a mobile crane is utilized so as to assemble the equipment portion of the crane and the jib. Afterwards, these parts are attached to the mast. After that, the mobile crane adds counterweights. Forklifts and crawler cranes can be a few 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 is able to match the building's height. The crane crew uses what is known as a climbing frame or a top climber which 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 additional 20 feet or 6.1m. Then, the crane operator uses the crane to insert and bolt into position another mast part piece.