Some industrial and commercial buildings are capable of reaching heights of over 60 stories. Obviously, when these buildings are being constructed, they require equally tall cranes to move the materials to the higher floors. There are cranes which are operated from the back of trucks or other types that have their own vehicle connected. 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. Wherever new construction like skyscrapers or apartment buildings and commercial facilities such as shopping center are being built, chances are a crane would 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 as it lifts things. On a luffing type of tower crane, the jib could ratchet to upward or downward angles. The lifting capacity for both kinds can vary from 30 pounds to 10,000 lbs.
Body
The crane's body is composed of a vertical steel mast that is composed of separate [parts. The sections are added to be able increase the overall height of the machine. 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 referred to. The driver of the crane works from inside of the tower.
Lift
In order 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 next to 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 tower's opposite side. The counter jib holds weights. These weights help to prevent the crane from toppling over when lifting heavy supplies.