There are several industrial and commercial buildings that now exceed 60 stories or more. These buildings all need tall cranes to be able to help move the materials to the upper floors. There are cranes that are operated from the back of trucks or other types which have their own vehicle attached. Tower cranes are the largest ones offered on the market.
Tower cranes are stand-alone structures seen as part of a major city's downtown skyline on high-rise building projects. Wherever new construction like for example skyscrapers or apartment buildings and commercial facilities such as shopping center are being constructed, odds are a crane would be on site.
Kinds
There are two different kinds of cranes: boom crane or the jib crane. The jib is a 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 30,000 lbs. to 10,000 pounds
Body
The crane's body 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 machine. The mast extends upward to where the desired height is, to the control module, which is a small room that has glass windows on all four sides or to the tower as it is also called. The operator of the crane works from inside of the tower.
Lift
In order to lift materials, the crane utilizes 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 tower's opposite side. The counter jib has weights. These weights help to prevent the crane from tipping over when heavy materials are carried.