There are several commercial and industrial buildings which now exceed 60 stories or more. These buildings all need tall cranes to help move the materials to the upper floors. There are cranes that are operated from the back of trucks or other types that have their own vehicle attached. Tower cranes are the largest types offered on the market.
Tower cranes are stand-alone structures seen as part of a major city's downtown skyline on high-rise building projects. When new construction like apartment buildings and skyscrapers and commercial facilities like shopping center are being built, chances are a crane will be on site.
Kinds
There are two different types of cranes: jib crane of the boom crane. The jib is a metal frame which extends from the main section. On a flat tower crane, the jib remains horizontal when it lifts items. On a luffing kind of tower crane, the jib could ratchet to downward or upward angles. The lifting capacity for both types can vary from 30 pounds to 10,000 lbs.
Body
The crane's body is composed of a vertical steel mast which is composed of separate [parts. The sections are added to increase the overall height of the machinery. 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
In order 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 situated 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 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 lifting heavy materials.