Back in August of 2009 we released a post digging into the science of cranes, their components and how everything works together. We decided it was time for an update, but you can still see the former boom crane post here: https://obtainable-rake.flywheelsites.com/cranes/science-behind-boom-cranes/
The Parts of A Crane
A quick look at crane terminology.
- The Boom: The boom of a crane is the long, telescopic, or fixed, arm that is used to move objects.
- The Counterweights: The counterweights are stabilizers placed near the cab’s exterior that prevent the crane from becoming unbalanced when lifting heavy loads.
- The Jib: The jib is the lattice-like structure that gives the boom the freedom to extend.
- The Rotex Gear: The Rotex gear affords the crane the ability to rotate its apparatus, thereby better enabling it to do its job from awkward standpoints. Hook rollers are also used in some crane applications.
A look into the parts of cranes, and what they can do.
The Ancient Greeks and Cranes
Many of the different technologies we use today have origins in ancient societies. Roads, water utilities, and even calculators all began as ideas to improve the efficiency with which we do things. One of the most prolific societies of inventors were the Ancient Greeks. From this wonderful society came many of our favorite inventions, but none have had the impact on the building of large structures that the crane has managed.
On top of being wonderful, the Greeks were an industrious and innovative society. In the 6th century BC they discovered that by using a lever-fulcrum system they could lift heavy loads with relative ease. Over time, they improved their design and added a few features such as hand cranks and pulleys.
Before their improvements, the loads moved by their cranes had to be small. This decreased the size of stones used for construction. It was faster than their previous method of ramps, but not nearly as strong. With the perfection of their additions, however, they were able to return to using the same large stones that previously required ramps. After their designs were spread throughout the world only a few small, but important, changes were made. And though there have been a few changes, the basic idea remains.
The Basics of Crane Technology
Cranes are a complex combination of simple machines. Basically, a lever is used to crank a line of cable through a pulley, or system of pulleys, to lift heavy objects. The cranes built by the Ancient Greeks were typically made with wood and rope, and anchored into the ground with large stakes. They were used to lift stones, and other heavy objects, into better positions for building large structures. Today crane parts are made of different types of metals, heavy-duty cables, and can lift and move objects many times heavier than the loads of ancient times.
Moving these objects involves some interesting physics. The load is attached to the end of the cable, then cranked along pulleys to whatever height necessary. The most fun lies in the smallest piece, the pulley. This wonderful, simple machine reduces the force of the weight of an object, and allows less force to be used to move it than would be necessary with direct force, such as pushing it up a ramp. The pulley divides the weight, spreads it out along the cables, and multiplies the force being used to lift the object. The perfect condition for this is a pulley with zero friction and cables that do not stretch. While currently impossible to reach these conditions, technology has gotten much closer than the Ancient Greeks with their ropes and wooden pulleys. Now, with new materials and powerful motors, cranes can be used to lift much heavier objects than ever before.