The base of the tower crane is usually bolted to a huge concrete pad that provides really necessary support. The base is attached to a tower or a mast and stabilizes the crane which is affixed to the inside of the structure of the building. 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 which enable the crane to rotate.
Tower cranes may have a max unsupported height of 80m or 265 feet, while the tower crane's maximum lifting capacity is 16,642 kg or 39,690 pounds with counter weights of 20 tons. Furthermore, 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. Lastly, the tower crane has a maximum reach of 70 meters or 230 feet.
Because of their extreme heights, there is a science involved to erecting a crane. The stationary structure will at first have to be transported to the construction location by utilizing a large tractor-trailer rig setup. Next, a mobile crane is utilized in order to assemble the machine portion of the crane and the jib. Then, these sections are connected to the mast. The mobile crane next adds counterweights. Forklifts and crawler cranes can be some of the other industrial machinery that is used 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 known 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. When 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 extra 6.1m or 20 feet. Next, the crane operator utilizes the crane to insert and bolt into position another mast section piece.