Some industrial and commercial buildings are capable of reaching heights of over 60 stories. Obviously, while these buildings are being built, they need equally tall cranes to move the supplies to the higher floors. There are cranes which have their own vehicle connected or other types that are operated from the rear of trucks. Tower cranes are the biggest types on the market.
Tower cranes are the stand-alone structures which are normally seen on high-rise building projects. Often, they are part of a major city's downtown skyline. When new construction such as 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 key types of cranes could 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 things. On a luffing kind of tower crane, the jib can ratchet to upward or downward angles. The lifting capacity for both kinds can range 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 separate sections. In order to increase the overall height of the equipment, parts 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 operator works from inside of the tower.
Lift
The crane utilizes a braided metal cord to lift materials. This cord extends out from a motor located next to the control module to the end of the boom or jib. 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 situated 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.