There are some industrial and commercial buildings that now exceed 60 stories or more. These buildings all need tall cranes to be able to help move the materials to the upper floors. There are cranes that are operated from the back of trucks or other kinds which have their own vehicle attached. Tower cranes are the largest kinds available on the market.
Tower cranes are the stand-alone structures that are often seen on high-rise building projects. Normally, 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 constructed, odds are a crane would be on site.
Kinds
There are two different kinds of cranes: boom crane or the jib 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 things. On a luffing type of tower crane, the jib could ratchet to upward or downward angles. The lifting capacity for both types can vary from 30,000 lbs. to 10,000 pounds
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, that is a small room which 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 uses a braided metal cord to raise supplies. This cord extends out from a motor situated next to 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 tower's opposite side. The counter jib has weights. These weights help to prevent the crane from toppling over when heavy materials are carried.