Several industrial and commercial buildings could reach heights of more than 60 stories. Obviously, while these buildings are being built, they require equally tall cranes to be able to move the materials to the higher floors. There are cranes that are operated from the back of trucks or other kinds that have their own vehicle connected. Tower cranes are the biggest kinds 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 for instance skyscrapers or apartment buildings and commercial facilities such as shopping center are being built, chances are a crane will be on site.
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 carries items. On a luffing type of tower crane, the jib could ratchet to downward or upward angles. The lifting capacity for both kinds could vary from 30 pounds to 10,000 pounds
The body of the crane is composed of a vertical steel mast which is composed of individual [parts. The parts are added to increase the overall height of the equipment. The mast extends upward to where 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 driver of the crane works from inside of the tower.
To raise 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 situated 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 holds weights. These weights help to prevent the crane from toppling over when lifting heavy materials.