There are several industrial and commercial buildings that now exceed 60 stories or more. These buildings all need tall cranes to be able to help transport the materials to the upper floors. There are cranes that are operated from the back of trucks or other types which have their own vehicle attached. Tower cranes are the biggest kinds on the market.
Tower cranes are the stand-alone structures that are often found on high-rise building projects. Often, they are part of a major city's downtown skyline. When new construction like for example skyscrapers or apartment buildings and commercial facilities such as shopping center are being built, odds are a crane will be on site.
Kinds
The two major kinds 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 when it lifts items. On a luffing type of tower crane, the jib can ratchet to downward or upward angles. The lifting capacity for both types can range from 30 pounds 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 machine, parts are added. The mast extends upward to where the desired height is, to the control module, which is a small room which has glass windows on all four sides or to the tower as it is also referred to. The driver of the crane works from inside of the tower.
Lift
To lift materials, 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 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 which holds the cord becomes balanced by a counter jib located on the opposite side of the tower. The counter jib has weights. These weights help to prevent the crane from toppling over when heavy materials are lifted.