There are several commercial and industrial buildings which now surpass 60 stories or more. These buildings all need tall cranes to help transport the materials to the higher floors. There are cranes which are operated from the rear of trucks or other kinds which have their own vehicle connected. Tower cranes are the largest kinds available on the market.
Tower cranes are stand-alone structures found as part of a major city's downtown skyline on high-rise building projects. Wherever new construction such as skyscrapers or apartment buildings and commercial facilities like for instance shopping center are being built, chances are a crane will be on site.
Kinds
The two major types of cranes could be differentiated by the way in which their jib or boom raises supplies. The jib is the metal frame that extends from the main section. On a flat tower crane, the jib remains horizontal as it carries items. On a luffing type of tower crane, the jib can ratchet to downward or upward angles. The lifting capacity for both kinds can range from 30,000 lbs. to 10,000 pounds
Body
The body of the crane is composed of a vertical steel mast that is composed of individual sections. The parts are added to increase the overall height of the machine. The mast extends upward to wherever the desired height is, to the control module, that is a small room that has glass windows on all four sides or to the tower as it is also referred to. The crane operator works from inside of the tower.
Lift
The crane uses a braided metal cord to be able to lift materials. This cord extends out from a motor situated near the control module to the end of the boom or jib. There is a pulley system situated at the end of the jib, through which the cord is positioned and lowered down. The jib which holds the cord becomes balanced by a counter jib situated on the tower's opposite side. The counter jib has weights. These weights help to prevent the crane from toppling over when heavy materials are carried.