Several commercial and industrial buildings can reach heights of over 60 stories. Obviously, while these buildings are being built, they require equally tall cranes to move the materials to the higher floors. There are cranes that have their own vehicle attached or other kinds that are operated from the back of trucks. Tower cranes are the biggest ones 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 for instance apartment buildings and skyscrapers and commercial facilities like shopping center are being constructed, chances are a crane will be on site.
Kinds
There are two different kinds of cranes: jib crane of the boom crane. The jib is a metal frame which extends from the main section. On a flat tower crane, the jib remains horizontal when it carries things. On a luffing type of tower crane, the jib could ratchet to downward or upward 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 [parts. The sections are added to increase the overall height of the machine. The mast extends upward to wherever 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 crane operator works from inside of the tower.
Lift
To lift 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 near 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 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 heavy materials are lifted.