Some industrial and commercial buildings can reach heights of more than 60 stories. Apparently, when these buildings are being built, they need equally tall cranes to transport the materials to the upper floors. There are cranes that have their own vehicle attached or other types which are operated from the rear of trucks. Tower cranes are the largest types on the market.
Tower cranes are stand-alone structures seen as part of a major city's downtown skyline on high-rise building projects. When new construction like skyscrapers or apartment buildings and commercial facilities like for instance shopping center are being constructed, chances are a crane would be on site.
Kinds
There are two different types 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 could range from 30,000 lbs. to 10,000 pounds
Body
The body of the crane is composed of a vertical steel mast that is composed of individual sections. The parts are added to be able increase the overall height of the machinery. 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 called. The driver of the crane works from inside of the tower.
Lift
In order to raise supplies, the crane uses a braided metal cord. The cord extends all the way to the end of the jib or boom from a motor situated near 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 which holds the cord becomes balanced by a counter jib situated on the opposite side of the tower. The counter jib has weights. These weights help to prevent the crane from toppling over when raising heavy supplies.