The origin of cranes is traced back to ancient Egypt when constructors of the great Egyptian temples used them to lift large stones and other construction material. This mighty tool can lift, lower, and move around extremely heavy loads that men would otherwise not be able to lift. Today’s cranes are so advanced that they use simple operation systems to perform complex lifting jobs.
The power of cranes
The power of a crane is determined by the amount of weight they can lift. Nonetheless, cranes are also classified based on the kind of lifting job they do. Here are a few examples:
These cranes are mostly found on construction sites. Tower cranes are anchored to the ground and used to lift heavy construction for the tall buildings we see in our cities. Think of Burj Khalifa in Dubai with a height of 2717ft.
Mobile cranes are usually mounted on wheeled vehicles, making them easier to transport and use where needed. This may include road or rail construction works.
Crawler cranes have a solid broad-base body and are fitted with caterpillar tracks. This makes them good to use on delicate grounds where wheeled vehicles would not operate. They can lift heavy loads and move them around a wide radius. One of the largest cranes in the world, the Liebherr Mobile Crane, is a crawler crane built by the Liebherr Group Company in German. It can lift 1,200 metric tons.
Dockside gantry cranes
Dockside gantry cranes can lift entire ships! They are used at dockyards to lift loads of extreme weight. For example, they can suspend and move heavy trucks from a transporting ship at the dock to place them on dry land.
Bubble cranes are the ideal decision where space is constrained. Ergonomically structured, they give a 23-meter working range and are just 2 meters wide, guaranteeing they can fit into rear entryways, slender garages and other tight spaces that mig
ht be hard to get to.
How cranes are built:
A key question for anyone interested in cranes is how these mighty machines are manufactured. Here are the 2 key steps:
Step 1: Building crane parts
At the initial stage in the construction of a crane, large iron blocks are made by melting iron ore and coke in a furnace. Oxygen is passed in the melted substance to remove carbon and the molten steel poured into thick iron shapes to cool.
The large iron bricks are shaped to desired forms such as plates, sheets, rods, and bars. This is done by placing the iron bars between large rollers with massive amounts of pressure. When hollow parts are made, sheets of steel are bent and welded or compact rod pierced with a rotating cone. Cables are made by rolling steel into long rods whose diameter is reduced to enable the production of twisted cables.
Once all these parts are made, they are delivered to a crane manufacturer, inspected for quality and stored in a warehouse for use in making the specific parts. Drills and lathes are used to shape the rods and sheets to specific crane parts including the base, the tower, and the operator’s cabin.
Step 2: Assembling the crane
Depending on the type of crane, the individual parts are assembled. In the example of a mobile crane, the broad base is bolted to a concrete pad that serves as the support for the entire crane. The base is connected to the tower (mast) which defines the height of the crane. At the top of the tower, a slewing unit is attached which consists of three parts:
- The jib: also known as the working arm which has a trolley running along to lift and carry the load.
- Shorter arm: this horizontal part houses the motors, electronics, and the concrete counterweight that are important for the crane’s balance.
- The operator’s cab: this is the small compartment where the operator sits and controls every movement of the crane. Thanks to this part, the operator can safely lower the tower, lift the load, and deliver it where it is needed.
The ready-to-use crane
When all the parts are assembled, the crane is tested and loaded on a ship by other cranes for delivery to its work station. Extremely large cranes may be transported as parts and assembled at the work sight.