Some commercial and industrial buildings can reach heights of over 60 stories. Obviously, when these buildings are being built, they require equally tall cranes to transport the supplies to the upper floors. There are cranes that are operated from the back of trucks or other types which have their own vehicle connected. Tower cranes are the largest types available on the market.
Tower cranes are the stand-alone structures that are often found on high-rise building projects. Often, they are part of a major city's downtown skyline. When new construction such as apartment buildings and skyscrapers and commercial facilities like for instance shopping center are being built, odds are a crane will be on site.
Kinds
The two major kinds of cranes can be distinguished by the manner in which their boom or jib raises supplies. The jib is the metal frame that extends from the main section. On a flat tower crane, the jib remains horizontal as it carries things. On a luffing kind of tower crane, the jib could ratchet to upward or downward angles. The lifting capacity for both kinds can range from 30,000 lbs. to 10,000 pounds
Body
The body of the crane is composed of a vertical steel mast which is composed of separate sections. The sections are added to be able increase the overall height of the machinery. 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 operator of the crane works from inside of the tower.
Lift
The crane uses a braided metal cord to be able to raise supplies. This cord extends out from a motor located 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 that 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 toppling over when heavy supplies are lifted.