There are several industrial and commercial buildings which now exceed 60 stories or more. These buildings all require tall cranes to help transport the materials to the higher 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 largest types on the market.
Tower cranes are the stand-alone structures which are usually seen on high-rise building projects. Normally, they are part of a major city's downtown skyline. When new construction like apartment buildings and skyscrapers and commercial facilities like shopping center are being built, chances are a crane will be on site.
Types
There are two different kinds of cranes: jib crane of the boom crane. The jib is a 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 can ratchet to downward or upward angles. The lifting capacity for both kinds could range from 30 pounds to 10,000 pounds
Body
The body of the crane is composed of a mast. This is a vertical steel frame that is a combination of individual parts. In order to increase the overall height of the machinery, parts are added. The mast extends upward to where 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 crane operator works from inside of the tower.
Lift
In order to raise supplies, 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 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 that holds the cord becomes balanced by a counter jib situated on the tower's opposite side. The counter jib holds weights. These weights help to prevent the crane from toppling over when raising heavy materials.