Some industrial and commercial buildings can reach heights of over 60 stories. Obviously, when these buildings are being built, they need equally tall cranes to move the supplies to the upper floors. There are cranes which have their own vehicle connected or other types that are operated from the rear of trucks. Tower cranes are the biggest types on the market.
Tower cranes are the stand-alone structures that 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 like shopping center are being built, chances are a crane will be on site.
Kinds
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 carries things. On a luffing type of tower crane, the jib could ratchet to upward or downward angles. The lifting capacity for both types can range from 30,000 lbs. to 10,000 pounds
Body
The body of the crane 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 machinery, sections are added. The mast extends upward to wherever the desired height is, to the control module, which 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
To lift materials, the crane utilizes a braided metal cord. The cord extends all the way to the end of the jib or boom from a motor located next to 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 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 supplies are lifted.