There are several commercial and industrial buildings which now exceed 60 stories or more. These buildings all need tall cranes to help move the supplies to the upper floors. There are cranes that have their own vehicle connected or other kinds which are operated from the rear of trucks. Tower cranes are the biggest types 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, chances are a crane will be on site.
Kinds
The two major types of cranes can be differentiated by the manner in which their boom or jib raises materials. The jib is the metal frame that extends from the main section. On a flat tower crane, the jib remains horizontal as it lifts things. 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 vertical steel mast which is composed of individual sections. The parts are added to increase the overall height of the machinery. The mast extends upward to wherever 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 crane operator works from inside of the tower.
Lift
The crane utilizes 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 boom or jib. 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 has weights. These weights help to prevent the crane from toppling over when lifting heavy materials.