There are some commercial and industrial buildings that now surpass 60 stories or more. These buildings all need tall cranes to help move the materials to the upper floors. There are cranes which are operated from the rear of trucks or other types that have their own vehicle connected. Tower cranes are the biggest ones offered on the market.
Tower cranes are the stand-alone structures which are normally seen on high-rise building projects. Normally, they are part of a major city's downtown skyline. When new construction like for instance apartment buildings and skyscrapers and commercial facilities such as shopping center are being built, odds are a crane would be on site.
Types
The two key types of cranes could be differentiated by the manner in which their boom or jib raises materials. The jib is the metal frame which extends from the main section. On a flat tower crane, the jib remains horizontal when it carries things. On a luffing type of tower crane, the jib could ratchet to upward or downward angles. The lifting capacity for both kinds 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 sections. The parts are added to increase the overall height of the machine. 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 called. The driver of the crane works from inside of the tower.
Lift
The crane uses a braided metal cord to lift materials. This cord extends out from a motor situated near 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 that 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 tipping over when heavy materials are lifted.