How does a crane work?
Although archaeological records show the use of crane-like machines in ancient Mesopotamia, utilised for irrigation, evidence of machines that operate for similar purposes as modern-day cranes date back to ancient Greece, to around 6.000 B.C.
There are a number of types of cranes nowadays, but they all operate in accordance with the same mechanical principles utilising a lever system, a pulley system or hydraulic cylinders to create the mechanical advantage necessary to move heavy items.
The function of a crane is to lift a heavy load from one location and to place it in another: this requires a crane to have weight-bearing and lifting capacity, but also stability to avoid toppling under the weight of the load.
Although it may seem intuitive, in order for a crane to be stable the magnitude of load that is to be lifted must be some value less than the load that will cause the crane to tip.
In order to prevent cranes from tipping, the stability can be increased by two main methods: by making the crane wider and increasing its centre of gravity, and by making the part of the crane susceptible to tipping heavier.
In order to better understand how cranes work, let’s examine the different parts of a crane.
CRANE PARTS AND FUNCTIONS
Mobile cranes feature driving components. These are the parts of the crane that are involved in the crane’s mobility. In the case of crawler mobile cranes, this refers to the tracks, the driving cab or operator cabin and the engine. In the case of wheeled mobile cranes, this will be an engine, an operator cab and a deck. Wheeled cranes and crawler cranes are suited to working in different environments.
Outriggers are supporting metal “legs” located along the sides of the mobile crane that extend outwards to increase the crane’s centre of gravity and to distribute weight more evenly. Depending on the terrain condition, pads may be required under the outriggers to stop these from sinking into soft ground.
Counterweights are an extremely important part of a crane. Counterweights are weights, usually made of steel or concrete that are mounted onto the back of the crane. Counterweights offset the weight of the load being lifted by weighing down the part of the crane that is susceptible to tilting due to the load weight. Counterweights can be added or taken away in accordance with the load to be lifted.
THE OPERATOR’S CABIN
The operator’s cabin is the part of the crane that houses all of the crane’s controls. It can often be combined with the driver’s cab and is located strategically to allow for the crane operator to have the maximum possible range of visibility during all lifting operations.
The boom is the part of a crane that we most easily recognise. Booms are the long arms that lift and position the load. Booms can come in one solid piece or can be “telescopic”, meaning that they extend out and draw back in. The two main types of booms are lattice booms and hydraulic booms.
THE HYDRAULIC PUMP
Some models of mobile cranes use hydraulic pressure in some extending parts to move and lift loads.
Hydraulic pumps are the part of a crane that deliver oil and water at pressure into hydraulic cylinders and other moving parts underneath and inside the boom. The pressure created by the oil and water under a moving part forces it upward out of the cylinder.
Most cranes feature a wire rope system that runs up and down the crane; this part of the crane is known as the hoist and typically includes a hook at the end. The hoist system allows a load to be raised and lowered in place without moving the boom. The hoist cable is wound around a hoist drum, which is a motor-powered cylinder that can be rotated in order to wind up the hoist wire and shorten it, or rotated in the opposite direction to unwind the hoist line, therefore lengthening it.
This is probably the part of the crane that requires the least explanation. We all know what a hook looks like. The hook is attached to the hoist at the end of the boom. The load is attached to this part of the crane via chains or other attachments to secure it to the crane for lifting.
The hook also features a hook block, designed to increase the crane’s lifting force.
If you are interested in hiring a mobile crane and you want to work with industry-leading experts, get in touch with Emerson Crane Hire. Emerson’s fleet includes some of the most specialised cranes in the industry and all of our machines are carefully maintained by our team of expert engineers.
Our account managers can offer guidance and advice throughout your project and we boast some of the most qualified and experienced crane operators in the field.
We also provide training courses for crane operation and other related disciplines including SiteRite, CPCS, ALLMI and NVQ courses.