There are several industrial and commercial buildings which now surpass 60 stories or more. These buildings all require tall cranes to help transport the supplies to the upper floors. There are cranes which have their own vehicle connected or other types that are operated from the back of trucks. Tower cranes are the largest kinds offered on the market.
Tower cranes are the stand-alone structures that are normally found on high-rise building projects. Usually, they are part of a major city's downtown skyline. Wherever new construction like for instance apartment buildings and skyscrapers and commercial facilities like for instance shopping center are being constructed, chances are a crane will be on site.
Kinds
The two key kinds of cranes can be distinguished by the manner in which their boom or jib raises supplies. 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 type of tower crane, the jib can ratchet to downward or upward angles. The lifting capacity for both kinds could range 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 machine, parts are added. The mast extends upward to where 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 called. The crane operator works from inside of the tower.
Lift
To lift supplies, the crane uses a braided metal cord. The cord extends all the way to the end of the jib or boom from a motor located near the control module. There is a pulley system located 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 holds weights. These weights help to prevent the crane from toppling over when lifting heavy materials.