Cranes

The modern cranes used in today's construction can be traced back thousands of years. Cranes have actually been in use since the Greek times as far back as 515 B.C. Of course cranes in those times were much simpler tools, but by the time Romans began to use cranes, advances were being made. Cranes back then were mostly limited to vertical movement unlike those today that are able to move large objects vertically and horizontally.

As man began to construct more and more buildings, he began to search for a way to lift heavier and sturdier objects to help improve the building structures. It appears that the Greeks were the first to employ the lever-pulley system that helped hoist heavy objects vertically.

Nowadays there are several different types of cranes that can lift much heavier objects than the Roman or Greek cranes of the past, and modern cranes can move objects 360 degrees as well as vertically. The two main types of cranes are mobile cranes and fixed cranes. Mobile cranes are able to travel certain distances to a particular project, and fixed cranes are permanent fixtures - such as those cranes seen in shipyards.

One example of a mobile crane is the truck-mounted crane. Here the crane is built into a large truck and is able to drive to various projects in various places. These types of cranes are typically able to lift anywhere from 14 to 1,300 tons. The side-lift crane and the rough-terrain crane are basically variations of the truck-mounted crane. The side-lift crane is used in jobs like lifting objects off rail cars, and the rough-terrain crane, with its larger tires, is used in off-road projects.

The crawler crane is another well-known type of crane. It doesn't have wheels but has tracks like those you might see on an old tank. The crawler crane has to be taken to a specific jobsite, but once there is able to move short distances to lift and carry objects.

Then there are fixed cranes - these cranes are not mobile. They are permanent fixtures at a site or have to be taken down and removed after a project is finished. Probably the most common type of fixed crane is the tower crane. This is the tall, slender crane that is found at all new high rise building construction sites. These cranes are able to hoist and move heavy objects tens of stories in the air.

Another type of fixed crane is the Gantry crane. This crane runs along a rail and can lift very heavy loads. These are common in shipyards for lifting crates off cargo ships.

Cranes have come a long way since Greek and Roman times. They've gone from simple lever-pulley systems to very complex machinery.