Several commercial and industrial buildings can reach heights of more than 60 stories. Obviously, when these buildings are being built, they need equally tall cranes to be able to transport the materials to the upper floors. There are cranes that have their own vehicle connected or other kinds that are operated from the back of trucks. Tower cranes are the biggest kinds offered on the market.
Tower cranes are the stand-alone structures which are usually seen on high-rise building projects. Normally, they are part of a major city's downtown skyline. When new construction like apartment buildings and skyscrapers and commercial facilities like for instance shopping center are being built, chances are a crane will be on site.
Kinds
The two major kinds of cranes can be distinguished by the manner in which their boom or jib raises materials. The jib is the metal frame which extends from the main section. On a flat tower crane, the jib remains horizontal when it lifts things. On a luffing kind of tower crane, the jib could ratchet to downward or upward angles. The lifting capacity for both types could vary from 30 pounds to 10,000 lbs.
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 machinery, sections are added. The mast extends upward to wherever 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 utilizes 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 that holds the cord becomes balanced by a counter jib located on the tower's opposite side. The counter jib has weights. These weights help to prevent the crane from toppling over when lifting heavy supplies.