Studying Tower Cranes: Learning How Tower Cranes Work

Imagine a construction site where all you see are ladders and people on scaffolding trying to reach one storey and the next. It would take more than a year or two to finish a building. It would take more than a month to put up one floor. It would take more than a day to string up and connect cables from one pole to the next without these man-made inventions that allow man to fly and move in the sky.

No, it’s not the airplane. In the world of construction, tower cranes are a necessity. The mere mortal cannot possibly do all these moving and connecting of parts and pieces in a twenty-storey building without them.

Tower cranes are used to lift steel, concrete, large tools and other building materials. With cranes, there’s no need for high-rise ladders and scaffolding to allow the workers to move from one storey to the other. So, what makes these cranes work?

Here’s a brief study guide on how tower cranes work:

Tower cranes are composed of the following parts: the base, mast, slewing unit, two horizontal jibs or machinery arm, the operator’s cab and the motor. The base is attached to a concrete pad that supports the crane. It is connected to the mast or the tower which is responsible for the tower crane’s height. On top of the mast is the slewing unit that allows the crane to rotate. This slewing unit is composed of the gear and the motor. On top of the slewing unit are three other parts. One is the long horizontal jib which carries the load. The other shorter horizontal jib contains the motor and electronics and counter weights. Then there’s also the operator’s cab where the worker or the operator is carried by the crane.

Now, after all those techno parts. Let’s go look into how these cranes work and why they don’t fall over. Each tower crane is built specifically with a maximum unsupported height of 265 feet or 80 meters. Its reach extends to 230 feet or 70 meters. As a machine that’s primarily used to carry or lift building materials, the crane can lift 19.8 tons or 18 metric tons. The closer the load is to the mast, the more weight it can lift safely. Say, if an operator positions the load 30 meters away from the mast, the crane can lift a maximum of 10.1 tons.

To avoid overloading, the crane uses limit switches that checks and makes sure that the crane carries only the allowed weight. The maximum load switch checks the pull on the cable and makes sure the load is not more than 18 tons. On the other hand, the load moment switch checks the ton meter rating of the crane as the load moves out of the jib.

Now, what makes them hold up?

One of the factors that make these cranes stable is the concrete pad constructed before the actual crane is set up. This pad is usually 30 feet by 30 feet by 4 feet. It weighs around 400,000 pounds. Anchor bolts are embedded in the pad to support the base of the crane.

Now, with these cranes going up from one storey to the other is an easy, no-sweat job in the construction site!

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