There are several commercial and industrial buildings that now exceed 60 stories or more. These buildings all require tall cranes to be able to help transport the supplies to the upper floors. There are cranes that are operated from the back of trucks or other types that have their own vehicle connected. Tower cranes are the largest ones offered on the market.
Tower cranes are stand-alone structures seen as part of a major city's downtown skyline on high-rise building projects. When new construction like apartment buildings and skyscrapers and commercial facilities such as shopping center are being built, odds are a crane would be on site.
Types
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 items. On a luffing type of tower crane, the jib could ratchet to upward or downward angles. The lifting capacity for both kinds can 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 which is a combination of separate sections. 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 that has glass windows on all four sides or to the tower as it is also referred to. The crane operator works from inside of the tower.
Lift
The crane uses a braided metal cord to raise supplies. This cord extends out from a motor located near the control module to the end of the jib or boom. 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 tower's opposite side. The counter jib holds weights. These weights help to prevent the crane from tipping over when heavy supplies are lifted.