There are several industrial and commercial buildings that now surpass 60 stories or more. These buildings all need tall cranes to help move the supplies to the upper floors. There are cranes that have their own vehicle attached or other kinds that are operated from the rear of trucks. Tower cranes are the largest ones on the market.
Tower cranes are the stand-alone structures that are usually seen on high-rise building projects. Usually, they are part of a major city's downtown skyline. Wherever new construction such as apartment buildings and skyscrapers and commercial facilities like for example shopping center are being built, chances are a crane will be on site.
Types
The two major kinds of cranes can be distinguished by the way in which their boom or jib lifts materials. The jib is the metal frame that extends from the main section. On a flat tower crane, the jib remains horizontal when it lifts 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 pounds to 10,000 pounds
Body
The body of the crane is composed of a vertical steel mast which is composed of separate 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, that is a small room which has glass windows on all four sides or to the tower as it is also referred to. The crane driver works from inside of the tower.
Lift
The crane uses a braided metal cord to raise supplies. This cord extends out from a motor located next to 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 holds weights. These weights help to prevent the crane from tipping over when heavy supplies are carried.