Typically the base that is bolted into a large concrete pad provides the crucial support for a tower crane. The base is attached to a mast or a tower 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.
Typically, the mast is a triangulated lattice structure measuring 10 feet square or 0.9m2. The slewing unit is attached to the very top of the mast. The slewing unit consists of a motor and a gear which allows 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 utilized in order to make sure that the operator does not overload the crane. There is even one more safety feature called a load moment switch to ensure that the driver does not exceed the ton meter load rating. Finally, 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 needs 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 equipment part of the crane and the jib. These sections are then attached to the mast. The mobile crane next adds counterweights. Crawler cranes and forklifts can be a few of the other industrial equipment 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 called 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 additional 6.1m or 20 feet. Next, the driver of the crane uses the crane to insert and bolt into place one more mast part piece.