Some industrial and commercial buildings are capable of reaching heights of more than 60 stories. Apparently, while these buildings are being built, they need equally tall cranes to be able to transport the supplies to the higher floors. There are cranes that are operated from the rear of trucks or other types which have their own vehicle attached. Tower cranes are the largest types on the market.
Tower cranes are the stand-alone structures which are normally found on high-rise building projects. Often, they are part of a major city's downtown skyline. When new construction like skyscrapers or apartment buildings and commercial facilities like shopping center are being built, chances are a crane will be on site.
Kinds
The two key types of cranes can be differentiated by the way in which their boom or jib lifts 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 could ratchet to upward or downward angles. The lifting capacity for both kinds could vary from 30 pounds to 10,000 lbs.
Body
The crane's body is composed of a mast. This is a vertical steel frame which is a combination of separate parts. In order to increase the overall height of the machinery, 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 driver works from inside of the tower.
Lift
The crane utilizes a braided metal cord to be able to raise supplies. This cord extends out from a motor located near the control module to the end of the boom or jib. There is a pulley system situated at the end of the jib, through which the cord is positioned and lowered down. The jib which 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 tipping over when heavy materials are lifted.