There are several industrial and commercial buildings which now exceed 60 stories or more. These buildings all require tall cranes to be able to help transport the materials to the higher floors. There are cranes which are operated from the back of trucks or other types which have their own vehicle attached. Tower cranes are the largest kinds offered on the market.
Tower cranes are stand-alone structures found as part of a major city's downtown skyline on high-rise building projects. Wherever new construction like apartment buildings and skyscrapers and commercial facilities like shopping center are being built, odds are a crane will be on site.
Types
There are two different kinds of cranes: boom crane or the jib crane. The jib is a metal frame that extends from the main section. On a flat tower crane, the jib remains horizontal when it lifts things. On a luffing kind of tower crane, the jib can ratchet to downward or upward 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 that is a combination of separate parts. In order to increase the overall height of the machinery, sections are added. The mast extends upward to wherever 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 driver of the crane works from inside of the tower.
Lift
The crane utilizes 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 jib or boom. 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 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.