There are several commercial and industrial buildings that now exceed 60 stories or more. These buildings all need tall cranes to help transport the materials to the upper floors. There are cranes which are operated from the back of trucks or other kinds which have their own vehicle attached. Tower cranes are the biggest types offered on the market.
Tower cranes are the stand-alone structures that are often found on high-rise building projects. Usually, they are part of a major city's downtown skyline. Wherever new construction like apartment buildings and skyscrapers and commercial facilities such as shopping center are being constructed, chances are a crane will be on site.
Types
The two major kinds of cranes could be differentiated by the way in which their boom or jib lifts 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 items. On a luffing kind 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 lbs.
Body
The crane's body is composed of a mast. This is a vertical steel frame which is a combination of individual parts. In order to increase the overall height of the equipment, sections are added. The mast extends upward to wherever 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 called. The operator of the crane works from inside of the tower.
Lift
The crane uses a braided metal cord to lift supplies. This cord extends out from a motor situated near 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 tipping over when heavy materials are carried.