Some industrial and commercial buildings are capable of reaching heights of over 60 stories. Obviously, when these buildings are being constructed, they need equally tall cranes to be able to transport the supplies to the higher floors. There are cranes which have their own vehicle connected or other types which are operated from the back of trucks. Tower cranes are the biggest ones available on the market.
Tower cranes are the stand-alone structures which are normally found on high-rise building projects. Normally, they are part of a major city's downtown skyline. Wherever new construction such as apartment buildings and skyscrapers and commercial facilities like shopping center are being built, odds are a crane would be on site.
Types
There are two different types 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 kind of tower crane, the jib can ratchet to downward or upward angles. The lifting capacity for both types could range from 30,000 lbs. to 10,000 lbs.
Body
The body of the crane is composed of a vertical steel mast that is composed of individual sections. The sections are added to 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 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
To raise materials, the crane uses a braided metal cord. The cord extends all the way to the end of the boom or jib from a motor situated 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 that holds the cord becomes balanced by a counter jib located on the tower's opposite side. The counter jib holds weights. These weights help to prevent the crane from tipping over when heavy supplies are lifted.