Some industrial and commercial buildings can reach heights of over 60 stories. Obviously, while these buildings are being constructed, they need equally tall cranes to transport the supplies to the higher floors. There are cranes that are operated from the rear of trucks or other kinds which have their own vehicle attached. Tower cranes are the largest types on the market.
Tower cranes are the stand-alone structures which are often found on high-rise building projects. Usually, they are part of a major city's downtown skyline. Wherever new construction like skyscrapers or apartment buildings and commercial facilities such as shopping center are being constructed, chances are a crane would be on site.
Types
There are two different kinds of cranes: boom crane or the jib crane. The jib is a metal frame which extends from the main section. On a flat tower crane, the jib remains horizontal as it carries items. On a luffing kind of tower crane, the jib could ratchet to upward or downward angles. The lifting capacity for both kinds can vary from 30,000 lbs. to 10,000 lbs.
Body
The crane's body is composed of a vertical steel mast which is composed of separate [parts. The parts are added to be able 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 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
The crane utilizes a braided metal cord to be able to raise materials. This cord extends out from a motor situated near the control module to the end of the jib or boom. 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 located on the opposite side of the tower. The counter jib has weights. These weights help to prevent the crane from tipping over when raising heavy materials.