The base of the tower crane is usually bolted to a big concrete pad that provides really crucial support. The base is connected to a tower or a mast and stabilizes the crane which is attached to the inside of the structure of the building. Normally, this attachment point is to an elevator shaft or to a concrete lift.
The mast of the crane is often a triangulated lattice structure that 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 motor and a gear 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 kg or 39,690 pounds with counter weights of 20 tons. Moreover, two limit switches are utilized in order to make certain that the operator does not overload the crane. There is even one more safety feature known as a load moment switch to make sure that the operator does not exceed the ton meter load rating. Finally, the maximum reach of a tower crane is 230 feet or 70 meters.
There is definitely a science involved with erecting a tower crane, specially because of their extreme heights. First, the stationary structure has to be brought to the construction site by using a large tractor-trailer rig setup. Then, a mobile crane is utilized in order to assemble the machinery part of the crane and the jib. These sections are then connected to the mast. The mobile crane then adds counterweights. Crawler cranes and forklifts could be some of the other industrial equipment which is used to erect a crane.
When the building is erected, mast extensions are added to the crane. This is how the crane's height could match the building's height. The crane crew utilizes what is called 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 so as 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 utilized to adjust the slewing unit up an extra 6.1m or 20 feet. Then, the driver of the crane uses the crane to insert and bolt into position one more mast part piece.