There are several industrial and commercial buildings which now surpass 60 stories or more. These buildings all require tall cranes to be able to help move the materials to the upper floors. There are cranes which are operated from the back of trucks or other types that have their own vehicle connected. Tower cranes are the largest types offered on the market.
Tower cranes are the stand-alone structures which are usually seen on high-rise building projects. Normally, they are part of a major city's downtown skyline. Wherever new construction like skyscrapers or apartment buildings and commercial facilities such as shopping center are being built, chances are a crane would be on site.
Types
There are two different kinds 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 type of tower crane, the jib could ratchet to downward or upward angles. The lifting capacity for both types can vary from 30,000 lbs. to 10,000 lbs.
Body
The body of the crane is composed of a vertical steel mast which is composed of separate [parts. The sections are added to increase the overall height of the equipment. The mast extends upward to wherever the desired height is, to the control module, that 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 raise supplies, 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 tower's opposite side. The counter jib holds weights. These weights help to prevent the crane from toppling over when lifting heavy materials.