A crane is a type of machine,
generally equipped with a hoist rope, wire ropes or chains, and sheaves, that
can be used both to lift and lower materials and to move them horizontally. It
is mainly used for lifting heavy things and transporting them to other places.
The device uses one or more simple machines to create mechanical advantage and
thus move loads beyond the normal capability of a human. Cranes are commonly
employed in the transport industry for the loading and unloading of freight, in
the construction industry for the movement of materials, and in the
manufacturing industry for the assembling of heavy equipment.
Mobile crane with outriggers
The first known construction cranes were invented by the Ancient Greeks and were powered by men or beasts of burden, such as donkeys. These cranes were used for the construction of tall buildings. Larger cranes were later developed, employing the use of human treadwheels, permitting the lifting of heavier weights. In the High Middle Ages, harbour cranes were introduced to load and unload ships and assist with their construction – some were built into stone towers for extra strength and stability. The earliest cranes were constructed from wood, but cast iron, iron and steel took over with the coming of the Industrial Revolution.
For many centuries, power was supplied by the physical exertion of men or animals, although hoists in watermills and windmills could be driven by the harnessed natural power. The first 'mechanical' power was provided by steam engines, the earliest steam crane being introduced in the 18th or 19th century, with many remaining in use well into the late 20th century. Modern cranes usually use internal combustion engines or electric motors and hydraulic systems to provide a much greater lifting capability than was previously possible, although manual cranes are still utilized where the provision of power would be uneconomic.
Cranes exist in an enormous variety of forms – each tailored to a specific use. Sizes range from the smallest jib cranes, used inside workshops, to the tallest tower cranes, used for constructing high buildings. Mini-cranes are also used for constructing high buildings, in order to facilitate constructions by reaching tight spaces. Finally, we can find larger floating cranes, generally used to build oil rigs and salvage sunken ships.
Some lifting machines do not strictly fit the above definition of a crane, but are generally known as cranes, such as stacker cranes and loader cranes.
The first known construction cranes were invented by the Ancient Greeks and were powered by men or beasts of burden, such as donkeys. These cranes were used for the construction of tall buildings. Larger cranes were later developed, employing the use of human treadwheels, permitting the lifting of heavier weights. In the High Middle Ages, harbour cranes were introduced to load and unload ships and assist with their construction – some were built into stone towers for extra strength and stability. The earliest cranes were constructed from wood, but cast iron, iron and steel took over with the coming of the Industrial Revolution.
For many centuries, power was supplied by the physical exertion of men or animals, although hoists in watermills and windmills could be driven by the harnessed natural power. The first 'mechanical' power was provided by steam engines, the earliest steam crane being introduced in the 18th or 19th century, with many remaining in use well into the late 20th century. Modern cranes usually use internal combustion engines or electric motors and hydraulic systems to provide a much greater lifting capability than was previously possible, although manual cranes are still utilized where the provision of power would be uneconomic.
Cranes exist in an enormous variety of forms – each tailored to a specific use. Sizes range from the smallest jib cranes, used inside workshops, to the tallest tower cranes, used for constructing high buildings. Mini-cranes are also used for constructing high buildings, in order to facilitate constructions by reaching tight spaces. Finally, we can find larger floating cranes, generally used to build oil rigs and salvage sunken ships.
Some lifting machines do not strictly fit the above definition of a crane, but are generally known as cranes, such as stacker cranes and loader cranes.
Tower Crane (a type of modern
fixed crane)
Tower cranes are
a modern form of balance crane that consist of the same basic parts. Fixed to
the ground on a concrete slab (and sometimes attached to the sides of
structures), tower cranes often give the best combination of height and lifting
capacity and are used in the construction of tall buildings. The base is then
attached to the mast which gives the crane its height. Further, the mast is
attached to the slewing unit (gear and motor) that allows the crane to rotate.
On top of the slewing unit there are three main parts which are: the long
horizontal jib (working arm), shorter counter-jib, and the operator's cab.
The long
horizontal jib is the part of the crane that carries the load. The counter-jib
carries a counterweight, usually of concrete blocks, while the jib suspends the
load to and from the center of the crane. The crane operator either sits in a
cab at the top of the tower or controls the crane by radio remote control from
the ground. In the first case the operator's cab is most usually located at the
top of the tower attached to the turntable, but can be mounted on the jib, or
partway down the tower. The lifting hook is operated by the crane operator
using electric motors to manipulate wire rope cables through a system of
sheaves. The hook is located on the long horizontal arm to lift the load which
also contains its motor.
In order to hook
and unhook the loads, the operator usually works in conjunction with a
signaller (known as a 'dogger', 'rigger' or 'swamper'). They are most often in
radio contact, and always use hand signals. The rigger or dogger directs the
schedule of lifts for the crane, and is responsible for the safety of the rigging
and loads.
Excellent post! This post provided me with valuable information about the basics of a crane. Crane technology is essential for the construction industry. They are used to lift and move heavy objects such as beams, columns, and large quantities of materials. You can also contact Boom & Bucket for additional info on the same topic.
ReplyDeleteThank you for sharing such an informative blog post on the basics of the crane. The article was well-written and provided a detailed explanation of the different components of a crane and how they work together to lift and move heavy objects. I particularly appreciated the diagrams and images included in the post, which made it easier to understand the technical aspects of crane operations. Keep up writing this type of article in the future also. If you want to know about bulldozers, you can check here How Much Does A Bulldozer Weigh?.
ReplyDelete