The tower crane's base is usually bolted to a big concrete pad that provides really crucial support. The base is connected to a mast or a tower and stabilizes the crane which is attached to the inside of the building's structure. Normally, this attachment point is to a concrete lift or to an elevator shaft.
The mast of the crane is often a triangulated lattice structure that measures 10 feet square or 0.9m2. Connected to the very top of the mast is the slewing unit. The slewing unit consists of a gear and a motor which enable the crane to rotate.
Tower cranes are able to have a maximum unsupported height of 80m or 265 feet. The tower crane's maximum lifting capacity is 16,642 kilograms or 39,690 pounds with counter weights of 20 tons. Furthermore, two limit switches are used to be able to ensure the driver does not overload the crane. There is also another safety feature referred to as a load moment switch to make sure that the operator does not surpass the ton meter load rating. Last of all, the maximum reach of a tower crane is 230 feet or 70 meters.
Because of their extreme heights, there is a science involved to erecting a crane. The stationary structure would first have to be brought to the construction location by using a huge tractor-trailer rig setup. Then, a mobile crane is utilized in order to assemble the machine portion of the jib and the crane. After that, these parts are connected to the mast. Then, the mobile crane adds counterweights. Crawler cranes and forklifts can be a few of the other industrial machines that is typically used 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 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. When complete, the slewing unit can detach from the top of the mast. In the top climber, hydraulic rams are used to adjust the slewing unit up an extra 20 feet or 6.1m. Then, the crane operator uses the crane to insert and bolt into position one more mast section piece.