Several industrial and commercial buildings can reach heights of over 60 stories. Obviously, when these buildings are being built, they require equally tall cranes to be able to transport the supplies to the higher floors. There are cranes that have their own vehicle connected or other types which are operated from the back of trucks. Tower cranes are the largest types offered 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 for example skyscrapers or apartment buildings and commercial facilities such as shopping center are being constructed, chances are a crane would be on site.
Kinds
There are two different types of cranes: jib crane of the boom crane. The jib is a metal frame that extends from the main section. On a flat tower crane, the jib remains horizontal when it lifts items. On a luffing kind of tower crane, the jib could ratchet to downward or upward angles. The lifting capacity for both types can vary from 30,000 lbs. to 10,000 pounds
Body
The body of the crane is composed of a mast. This is a vertical steel frame that is a combination of individual sections. In order to increase the overall height of the machine, sections are added. The mast extends upward to where 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 referred to. The crane driver works from inside of the tower.
Lift
To raise supplies, the crane utilizes a braided metal cord. The cord extends all the way to the end of the jib or boom from a motor located 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 that holds the cord becomes balanced by a counter jib located on the opposite side of the tower. The counter jib holds weights. These weights help to prevent the crane from toppling over when raising heavy supplies.