There are several commercial and industrial buildings which now surpass 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 which have their own vehicle attached or other types that are operated from the back of trucks. Tower cranes are the biggest kinds 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 such as skyscrapers or apartment buildings and commercial facilities like shopping center are being built, chances are a crane will be on site.
Types
The two major types of cranes can be distinguished by the manner in which their jib or boom 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 items. On a luffing type of tower crane, the jib could 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 vertical steel mast which is composed of separate [parts. The parts are added to increase the overall height of the equipment. The mast extends upward to where 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 referred to. The operator of the crane works from inside of the tower.
Lift
To lift materials, the crane uses 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 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 tower's opposite side. The counter jib holds weights. These weights help to prevent the crane from toppling over when lifting heavy materials.