There are several industrial and commercial buildings which now exceed 60 stories or more. These buildings all need tall cranes to help transport the supplies to the upper floors. There are cranes that 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 stand-alone structures found as part of a major city's downtown skyline on high-rise building projects. When new construction such as skyscrapers or apartment buildings and commercial facilities like for example shopping center are being constructed, odds are a crane would be on site.
Types
The two major kinds of cranes can be distinguished by the way in which their boom or jib lifts supplies. The jib is the metal frame which extends from the main section. On a flat tower crane, the jib remains horizontal when it lifts 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 pounds to 10,000 lbs.
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, sections are added. The mast extends upward to where the desired height is, to the control module, that is a small room that has glass windows on all four sides or to the tower as it is also called. The driver of the crane works from inside of the tower.
Lift
The crane uses a braided metal cord to be able to lift materials. 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 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 located on the tower's opposite side. The counter jib has weights. These weights help to prevent the crane from tipping over when lifting heavy supplies.