There are several industrial and commercial buildings that now surpass 60 stories or more. These buildings all need tall cranes to be able to help 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 attached. Tower cranes are the largest kinds on the market.
Tower cranes are the stand-alone structures that are normally found on high-rise building projects. Normally, they are part of a major city's downtown skyline. Wherever new construction like for example skyscrapers or apartment buildings and commercial facilities like shopping center are being constructed, odds are a crane will be on site.
Types
The two major types of cranes can be distinguished by the way in which their jib or boom raises supplies. The jib is the metal frame that extends from the main section. On a flat tower crane, the jib remains horizontal as it carries items. On a luffing kind of tower crane, the jib could ratchet to downward or upward angles. The lifting capacity for both kinds can range from 30,000 lbs. to 10,000 lbs.
Body
The crane's body is composed of a vertical steel mast which is composed of individual [parts. The sections are added to 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 crane operator works from inside of the tower.
Lift
The crane utilizes a braided metal cord to be able to lift supplies. This cord extends out from a motor situated near the control module to the end of the jib or boom. 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 situated on the opposite side of the tower. The counter jib has weights. These weights help to prevent the crane from toppling over when lifting heavy materials.