There are some commercial and industrial buildings which now surpass 60 stories or more. These buildings all require tall cranes to be able to help transport the materials to the upper floors. There are cranes that are operated from the rear of trucks or other types that have their own vehicle attached. Tower cranes are the largest ones 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 like apartment buildings and skyscrapers and commercial facilities like for example shopping center are being built, odds are a crane will be on site.
Kinds
The two major kinds of cranes can be differentiated by the manner in which their boom or jib lifts materials. The jib is the metal frame which extends from the main section. On a flat tower crane, the jib remains horizontal when it carries items. On a luffing type of tower crane, the jib can ratchet to downward or upward angles. The lifting capacity for both types could vary from 30 pounds to 10,000 lbs.
Body
The body of the crane is composed of a vertical steel mast which is composed of individual sections. The parts are added to be able increase the overall height of the equipment. The mast extends upward to wherever the desired height is, to the control module, which is a small room which has glass windows on all four sides or to the tower as it is also called. The driver of the crane works from inside of the tower.
Lift
To lift supplies, the crane uses a braided metal cord. The cord extends all the way to the end of the boom or jib from a motor located next to the control module. There is a pulley system located at the end of the jib, through which the cord is positioned and lowered down. The jib that holds the cord becomes balanced by a counter jib located on the opposite side of the tower. The counter jib holds weights. These weights help to prevent the crane from toppling over when heavy supplies are carried.