how do they get counter-weights onto high cranes?

Answer 1

The top section of a tower crane, including the cab, boom, and counterbalance, is erected on the crane's base, using a portable crane. After that, there is a mechanism on the tower crane that jacks up the top and allows another tower section to be inserted under it to increase the crane's height.

Answer 2

1

Answer 3

2

Answer 4

Crane Counterweights

Answer 5

The crane itself hoists them. Suppose a crane is rated to support X tons, then the optimal counter weight would be X/2 tons, an the crane has to be designed to support an imbalance of X/2 tons.
If the operational crane is not lifting anything, then it has to support its unbalanced counter weight, and if it lifts its maximum load, then it has to stand an unbalanced load of (again) X/2 -- the other half of the load is balanced by the counterweight.
Therefore the crane is capable of hoisting its own counterweight as an unbalanced load. It is then secured in place and the crane can then start operating to its rated maximum lifting capability.

Answer 6

4

Answer 7

3

Answer 8

This is overkill. 50 tons from 1 foot or 1 ton from 50 foot would do the job. Arguably it would be more humane, but humane execution was the express intent of the guillotine. Didn't stop it being widely reviled. You might be interested in the wikipedia article, Execution by Elephant, the nearest to what you suggest that has actually been used.

Answer 9

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Answer 10

A modern crawler type derrick crane with outriggers. The latticed boom is fitted with a jib.
A modern crawler type derrick crane with outriggers. The latticed boom is fitted with a jib.
An old manual crane with a pivoted boom. The incline of the boom is controlled by means of chains, sprockets and gears.
An old manual crane with a pivoted boom. The incline of the boom is controlled by means of chains, sprockets and gears.

A crane is a mechanical lifting device equipped with a winder, wire ropes and sheaves that can be used both to lift and lower materials and to move them horizontally. It 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.
Contents
[hide]

* 1 Overview
* 2 History of cranes
o 2.1 Ancient Greek cranes
o 2.2 Ancient Roman cranes
o 2.3 Medieval cranes
+ 2.3.1 Origins
+ 2.3.2 Structure and placement
+ 2.3.3 Mechanics and operation
+ 2.3.4 Harbor cranes
* 3 Mechanical principles
o 3.1 Lifting capacity
o 3.2 Stability of crane
* 4 Types of cranes
o 4.1 Railroad cranes
o 4.2 Mobile crane
o 4.3 Telescopic crane
o 4.4 Tower crane
o 4.5 Hammerhead crane
o 4.6 Truck-mounted crane
o 4.7 Rough terrain crane
o 4.8 Crawler crane
o 4.9 Gantry crane
o 4.10 Overhead crane
o 4.11 Floating crane
o 4.12 Vessel (Deck) crane
o 4.13 Aerial crane
o 4.14 Jib crane
* 5 Crane-like machines
o 5.1 Loader crane
o 5.2 Rolloader crane
o 5.3 Stacker crane
* 6 Cranes of special interest
* 7 Manufacturers
o 7.1 Historic
* 8 Training
* 9 References
* 10 Literature
* 11 See also
o 11.1 Types of crane
o 11.2 Other
o 11.3 Related ideas
* 12 External links

[edit] Overview

The first 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 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 utilised 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, and the largest floating cranes, used to build oil rigs and salvage sunken ships.

This article also covers lifting machines that do not strictly fit the above definition of a crane, but are generally known as cranes, such as stacker cranes and loader cranes.

[edit] History of cranes
Tower of Babel constructed with a treadwheel crane, illustration in the Maciejowski Bible (fol 3r)
Tower of Babel constructed with a treadwheel crane, illustration in the Maciejowski Bible (fol 3r)

[edit] Ancient Greek cranes

The crane for lifting heavy loads was invented by the ancient Greeks in the late 6th century BC.[1] The archaeological record shows that no later than c.515 BC distinctive cuttings for both lifting tongs and lewis irons begin to appear on stone blocks of Greek temples. Since these holes point at the use of a lifting device, and since they are to be found either above the centre of gravity of the block, or in pairs equidistant from a point over the centre of gravity, they are regarded by archaeologists as the positive evidence required for the existence of the crane.[1]

The introduction of the winch and pulley hoist soon led to a widespread replacement of ramps as the main means of vertical motion. For the next two hundred years, Greek building sites witnessed a sharp drop in the weights handled, as the new lifting technique made the use of several smaller stones more practical than of fewer larger ones. In contrast to the archaic period with its tendency to ever-increasing block sizes, Greek temples of the classical age like the Parthenon invariably featured stone blocks weighing less than 15-20 tons. Also, the practice of erecting large monolithic columns was practically abandoned in favour of using several column drums.[2]

Although the exact circumstances of the shift from the ramp to the crane technology remain unclear, it has been argued that the volatile social and political conditions of Greece were more suitable to the employment of small, professional construction teams than of large bodies of unskilled labour, making the crane more preferable to the Greek polis than the more labour-intensive ramp which had been the norm in the autocratic societies of Egypt or Assyria.[2]

The first unequivocal literary evidence for the existence of the compound pulley system appears in the Mechanical Problems (Mech. 18, 853a32-853b13) attributed to Aristotle (384-322 BC), but perhaps composed at a slightly later date. Around the same time, block sizes at Greek temples began to match their archaic predecessors again, indicating that the more sophisticated compound pulley must have found its way to Greek construction sites by then.[3]

[edit] Ancient Roman cranes
Reconstruction of a 10.4m high Roman Polyspastos at Bonn, Germany (I)
Reconstruction of a 10.4m high Roman Polyspastos at Bonn, Germany (I)
Reconstruction of a 10.4m high Roman Polyspastos at Bonn, Germany (II)
Reconstruction of a 10.4m high Roman Polyspastos at Bonn, Germany (II)

The heyday of crane in ancient times came under the Roman Empire, when construction activity soared and buildings reached enormous dimensions. The Romans adopted the Greek crane and developed it further. We are relatively well informed about their lifting techniques thanks to rather lengthy accounts by the engineers Vitruvius (De Architectura 10.2, 1-10) and Heron of Alexandria (Mechanica 3.2-5). There are also two surviving reliefs of Roman treadwheel cranes offering pictorial evidence, with the Haterii tombstone from the late first century AD being particularly detailed.

The simplest Roman crane, the Trispastos, consisted of a single-beam jib, a winch, a rope, and a block containing three pulleys. Having thus a mechanical advantage of 3:1, it has been calculated that a single man working the winch could raise 150 kg (3 pulleys x 50 kg = 150), assuming that 50 kg represent the maximum effort a man can exert over a longer time period. Heavier crane types featured five pulleys (Pentaspastos) or, in case of the largest one, a set of three by five pulleys (Polyspastos) and came with two, three or four masts, depending on the maximum load. The Polyspastos, when worked by four men at both sides of the winch, could already lift 3000 kg (3 ropes x 5 pulleys x 4 men x 50 kg = 3000 kg). In case the winch was replaced by a treadwheel, the maximum load even doubled to 6000 kg at only half the crew, since the treadwheel possesses a much bigger mechanical advantage due to its larger diameter. This meant that, in comparison to the construction of the Egyptian Pyramids, where about 50 men were needed to move a 2.5 ton stone block up the ramp (50 kg per person), the lifting capability of the Roman Polyspastos proved to be 60 times higher (3000 kg per person).[4]

However, numerous extant Roman buildings which feature much heavier stone blocks than those handled by the Polyspastos indicate that the overall lifting capability of the Romans went far beyond that of any single crane. At the temple of Jupiter at Baalbek, for incidence, the architraves blocks weigh up to 60 tons each, and the corner cornices blocks even over 100 tons, all of them raised to a height of ca. 19 m above the ground.[3] In Rome, the capital block of Trajan's Column weighs 53.3 tons which had to be lifted at a height of ca. 34 m.[5]

It is assumed that Roman engineers accomplished lifting these extraordinary weights by two measures: First, as suggested by Heron, a lifting tower was set up, whose four masts were arranged in the shape of a quadrangle with parallel sides, not unlike a siege tower, but with the column in the middle of the structure (Mechanica 3.5).[6] Second, a multitude of capstans were placed on the ground around the tower, for, although having a lower leverage ratio than treadwheels, capstans could be set up in higher numbers and run by more men (and, moreover, by draught animals).[7] This use of multiple capstans is also described by Ammianus Marcellinus (17.4.15) in connection with the lifting of the Lateranense obelisk in the Circus Maximus (ca. 357 AD). The maximum lifting capability of a single capstan can be established by the number of lewis iron holes bored into the monolith. In case of the Baalbek architrave blocks, which weigh between 55 and 60 tons, eight extant holes suggest an allowance of 7.5 ton per lewis iron, that is per capstan.[8] Lifting such heavy weights in a concerted action required a great amount of coordination between the work groups applying the force to the capstans.

[edit] Medieval cranes
Small-scale modern reconstruction of the medieval gantry crane at Brugge harbor
Small-scale modern reconstruction of the medieval gantry crane at Brugge harbor
The Kraanplein ("Crane Square") at Brugge is glimpsed in this portrait of 1551 by Pieter Pourbus
The Kraanplein ("Crane Square") at Brugge is glimpsed in this portrait of 1551 by Pieter Pourbus
Medieval port crane with building overhanging in the former Hanse town of Danzig.
Medieval port crane with building overhanging in the former Hanse town of Danzig.

During the High Middle Ages the treadwheel crane was reintroduced on a large scale after the technology had fallen into disuse in western Europe with the demise of the Western Roman Empire.[9] The earliest reference to a treadwheel (magna rota) reappears in archival literature in France about 1225,[10] followed by an illuminated depiction in a manuscript of probably also French origin dating to 1240.[9] In navigation, the earliest uses of harbor cranes are documented for Utrecht in 1244, Antwerp in 1263, Brugge in 1288 and Hamburg in 1291,[11] while in England the treadwheel is not recorded before 1331.[12]

Generally, vertical transport was done safer and cheaper by cranes than by customary methods. Typical areas of application were harbors, mines, and, in particular, building sites where the treadwheel crane played a pivotal role in the construction of the lofty Gothic cathedrals. Nevertheless, both archival and pictorial sources of the time suggest that newly introduced machines like treadwheels or wheelbarrows did not completely replace more labor-intensive methods like ladders, hods and handbarrows. Rather, old and new machinery continued to coexist on medieval construction sites[13] and harbors.[11]

Apart from treadwheels, medieval depictions also show cranes to be powered manually by windlasses with radiating spokes, cranks and by the 15th century also by windlasses shaped like a ship's wheel. To smooth out irregularities of impulse and get over 'dead-spots' in the lifting process flywheels are known to be in use as early as 1123.[14]

[edit] Origins

The exact process by which the treadwheel crane was reintroduced is not recorded,[10] although its return to construction sites has undoubtedly to be viewed in close connection with the simultaneous rise of Gothic architecture. The reappearance of the treadwheel crane may have resulted from a technological development of the windlass from which the treadwheel structurally and mechanically evolved. Alternatively, the medieval treadwheel may represent a deliberate reinvention of its Roman counterpart drawn from Vitruvius' De architectura which was available in many monastic libraries. Its reintroduction may have been inspired, as well, by the observation of the labor-saving qualities of the waterwheel with which early treadwheels shared many structural similarities.[12]

[edit] Structure and placement

The medieval treadwheel was a large wooden wheel turning around a central shaft with a treadway wide enough for two workers walking side by side. While the earlier 'compass-arm' wheel had spokes directly driven into the central shaft, the more advanced 'clasp-arm' type featured arms arranged as chords to the wheel rim,[15] giving the possibility of using a thinner shaft and providing thus a greater mechanical advantage.[16]

Contrary to a popularly held belief, cranes on medieval building sites were neither placed on the extremely lightweight scaffolding used at the time nor on the thin walls of the Gothic churches which were incapable of supporting the weight of both hoisting machine and load. Rather, cranes were placed in the initial stages of construction on the ground, often within the building. When a new floor was completed, and massive tie beams of the roof connected the walls, the crane was dismantled and reassembled on the roof beams from where it was moved from bay to bay during construction of the vaults.[17] Thus, the crane ‘grew’ and ‘wandered’ with the building with the result that today all extant construction cranes in England are found in church towers above the vaulting and below the roof, where they remained after building construction for bringing material for repairs aloft.[18]

Less frequently, medieval illuminations also show cranes mounted on the outside of walls with the stand of the machine secured to putlogs.[19]

[edit] Mechanics and operation
Tower crane at the inland harbour of Trier from 1413.
Tower crane at the inland harbour of Trier from 1413.

In contrast to modern cranes, medieval cranes and hoists - much like their counterparts in Greece and Rome[20] - were primarily capable of a vertical lift, and not used to move loads for a considerable distance horizontally as well.[17] Accordingly, lifting work was organized at the workplace in a different way than today. In building construction, for example, it is assumed that the crane lifted the stone blocks either from the bottom directly into place,[17] or from a place opposite the centre of the wall from where it could deliver the blocks for two teams working at each end of the wall.[20]

Additionally, the crane master who usually gave orders at the treadwheel workers from outside the crane was able to manipulate the movement laterally by a small rope attached to the load.[21] Slewing cranes which allowed a rotation of the load and were thus particularly suited for dockside work appeared as early as 1340.[22] While ashlar blocks were directly lifted by sling, lewis or devil's clamp (German Teufelskralle), other objects were placed before in containers like pallets, baskets, wooden boxes or barrels.[23]

It is noteworthy that medieval cranes rarely featured ratchets or brakes to forestall the load from running backward.[24] This curious absence is explained by the high friction force exercised by medieval treadwheels which normally prevented the wheel from accelerating beyond control.[21]

[edit] Harbor cranes
Beyond the modern warship stands a crane constructed in 1742, used for mounting masts to large sailing vessels. Copenhagen, Denmark
Beyond the modern warship stands a crane constructed in 1742, used for mounting masts to large sailing vessels. Copenhagen, Denmark

According to the “present state of knowledge” unknown in antiquity, stationary harbor cranes are considered a new development of the Middle Ages.[11] The typical harbor crane was a pivoting structure equipped with double treadwheels. These cranes were placed docksides for the loading and unloading of cargo where they replaced or complemented older lifting methods like see-saws, winches and yards.[11]

Two different types of harbor cranes can be identified with a varying geographical distribution: While gantry cranes which pivoted on a central vertical axle were commonly found at the Flemish and Dutch coastside, German sea and inland harbors typically featured tower cranes where the windlass and treadwheels were situated in a solid tower with only jib arm and roof rotating.[25] Interestingly, dockside cranes were not adopted in the Mediterranean region and the highly developed Italian ports where authorities continued to rely on the more labor-intensive method of unloading goods by ramps beyond the Middle Ages.[26]

Unlike construction cranes where the work speed was determined by the relatively slow progress of the masons, harbor cranes usually featured double treadwheels to speed up loading. The two treadwheels whose diameter is estimated to be 4 m or larger were attached to each side of the axle and rotated together.[11] Today, according to one survey, fifteen treadwheel harbor cranes from pre-industrial times are still extant throughout Europe.[27] Beside these stationary cranes, floating cranes which could be flexibly deployed in the whole port basin came into use by the 14th century.[25]

[edit] Mechanical principles
Cranes helping to construct a tower block in Melbourne, Australia
Cranes helping to construct a tower block in Melbourne, Australia

There are two major considerations that are taken into account in the design of cranes. The first is that the crane must be able to lift a load of a specified weight and the second is that the crane must remain stable and not topple over when the load is lifted and moved to another location.

[edit] Lifting capacity

Cranes illustrate the use of one or more simple machines to create mechanical advantage.

* The lever. A balance crane contains a horizontal beam (the lever) pivoted about a point called the fulcrum. The principle of the lever allows a heavy load attached to the shorter end of the beam to be lifted by a smaller force applied in the opposite direction to the longer end of the beam. The ratio of the load's weight to the applied force is equal to the ratio of the lengths of the longer arm and the shorter arm, and is called the mechanical advantage.
* The pulley. A jib crane contains a tilted strut (the jib) that supports a fixed pulley block. Cables are wrapped multiple times round the fixed block and round another block attached to the load. When the free end of the cable is pulled by hand or by a winding machine, the pulley system delivers a force to the load that is equal to the applied force multiplied by the number of lengths of cable passing between the two blocks. This number is the mechanical advantage.
* The hydraulic cylinder. This can be used directly to lift the load (as with a HIAB), or indirectly to move the jib or beam that carries another lifting device.

Crane constructing a building in Kansas City
Crane constructing a building in Kansas City

Cranes, like all machines, obey the principle of conservation of energy. This means that the energy delivered to the load cannot exceed the energy put into the machine. For example, if a pulley system multiplies the applied force by ten, then the load moves only one tenth as far as the applied force. Since energy is proportional to force multiplied by distance, the output energy is kept roughly equal to the input energy (in practice slightly less, because some energy is lost to friction and other inefficiencies).

[edit] Stability of crane

In order for a crane to be stable, the sum of all moments about any point such as the base of the crane must equate to zero. In practice, the magnitude of load that is permitted to be lifted (called the "rated load" in the US) is some value less than the load that will cause the crane to tip. Under US standards for mobile cranes, the stability-limited rated load for a crawler crane is 75% of the tipping load. The stability-limited rated load for a mobile crane supported on outriggers is 85% of the tipping load.

[edit] Types of cranes

[edit] Railroad cranes
Diesel-powered railroad crane for maintenance work – Tampa, Florida.
Diesel-powered railroad crane for maintenance work – Tampa, Florida.

Main article: Crane (railroad)

A railroad crane is a crane with flanged wheels, used by railroads. The simplest form is just a crane mounted on a railroad car or on a flatcar. More capable devices are purpose-built.

Different types of crane are used for maintenenace work, recovery operations and freight loading in goods yards.

[edit] Mobile crane

The most basic type of mobile crane consists of a steel truss or telescopic boom mounted on a mobile platform, which may be rail, wheeled (including "truck" carriers) or caterpillar tracks. The boom is hinged at the bottom, and can be raised and lowered by cables or by hydraulic cylinders. A hook is suspended from the top of the boom by wire rope and sheaves. The wire ropes are operated by whatever prime movers the designers have available, operating through a variety of transmissions. Steam engines, electric motors and internal combustion engines (IC) have all been used. Older cranes' transmissions tended to be clutches. This was later modified when using IC engines to match the steam engines "max torque at zero speed" characteristic by the addition of a hydrokinetic element culminating in controlled torque converters. The operational advantages of this arrangement can now be achieved by electronic control of hydrostatic drives, which for size and other considerations is becoming standard. Some examples of this type of crane can be converted to a demolition crane by adding a demolition ball, or to an earthmover by adding a clamshell bucket or a dragline and scoop, although design details can limit their effectiveness.

To increase the horizontal reach of the hoist, the boom may be extended by adding a jib to the top. The jib can be fixed or, in more complex cranes, luffing (that is, able to be raised and lowered).
A telescopic crane dismantling a 40 m tower crane in Cambridge, UK
A telescopic crane dismantling a 40 m tower crane in Cambridge, UK

[edit] Telescopic crane

A telescopic crane has a boom that consists of a number of tubes fitted one inside the other. A hydraulic or other powered mechanism extends or retracts the tubes to increase or decrease the total length of the boom. These types of booms are often used for short term construction projects, rescue jobs, lifting boats in and out of the water, etc. The relative compactness of telescopic booms make them adaptable for many mobile applications.

[edit] Tower crane
Six tower cranes constructing buildings at Canon's Marsh, Bristol, England.
Six tower cranes constructing buildings at Canon's Marsh, Bristol, England.
Luffing tower crane,Singapore
Luffing tower crane,Singapore
Concrete counter-weights on a tower crane Cape Town, South Africa.
Concrete counter-weights on a tower crane Cape Town, South Africa.
A "jack up" mast supporting a tower crane. The inner element is moved upward with jacks and a new outer section is assembled around the exposed portion.
A "jack up" mast supporting a tower crane. The inner element is moved upward with jacks and a new outer section is assembled around the exposed portion.

The tower crane is a modern form of balance crane. Fixed to the ground (or "jacked up" and supported by the structure as the structure is being built), tower cranes often give the best combination of height and lifting capacity and are used in the construction of tall buildings. To save space and to provide stability the vertical part of the crane is often braced onto the completed structure which is normally the concrete lift shaft in the center of the building. A horizontal boom is balanced asymmetrically across the top of the tower. Its short arm carries a counterweight of concrete blocks, and its long arm carries the lifting gear. The crane operator either sits in a cabin at the top of the tower or controls the crane by radio remote control from the ground, usually standing near the load. In the first case the operator's cabin is located at the top of the tower just below the horizontal boom. The boom is mounted on a slewing bearing and is rotated by means of a slewing motor. The lifting hook is operated by a system of sheaves.

A tower crane is usually assembled by a telescopic crane of smaller lifting capacity but greater height and in the case of tower cranes that have risen while constructing very tall skyscrapers, a smaller crane (or derrick) will sometimes be lifted to the roof of the completed tower to dismantle the tower crane afterwards. A self-assembling tower crane lifts itself off the ground using jacks, allowing the next section of the tower to be inserted at ground level.

[edit] Hammerhead crane

The hammerhead, or giant cantilever, crane is a fixed-jib crane consisting of a steel-braced tower on which revolves a large, horizontal, double cantilever; the forward part of this cantilever or jib carries the lifting trolley, the jib is extended backwards in order to form a support for the machinery and counter-balancing weight. In addition to the motions of lifting and revolving, there is provided a so-called "racking " motion, by which the lifting trolley, with the load suspended, can be moved in and out along the jib without altering the level of the load. Such horizontal movement of the load is a marked feature of later crane design. Hammerhead cranes are generally constructed in large sizes, up to 350 tons.

The design evolved first in Germany around the turn of the 19th century and was adopted for use in British shipyards to support the battleship construction program from 1904-1914. The ability of the hammerhead crane to lift heavy weights was useful for installing large pieces of battleships such as armour plate and gun barrels. Hammerhead cranes were also installed in naval shipyards in Japan and in the USA. The British Government also installed a hammerhead crane at the Singapore Naval Base (1938) and later a copy of the crane was installed at Garden Island Naval Dockyard in Sydney (1951). These cranes provided repair support for the battle fleet operating far from Great Britain.

The principal engineering firm for hammerhead cranes in the British empire was Sir William Arrol & Co Ltd.

[edit] Truck-mounted crane
A typical truck-mounted crane
A typical truck-mounted crane

A crane mounted on a truck carrier provides the mobility for this type of crane.

Generally, these cranes are designed to be able to travel on streets and highways, eliminating the need for special equipment to transport a crane to the jobsite. When working on the jobsite, outriggers are extended horizontally from the chassis then down vertically to level and stabilize the crane while stationary and hoisting. Many truck cranes possess limited slow-travelling capability (just a few miles per hour) while suspending a load. Great care must be taken not to swing the load sideways from the direction of travel, as most of the anti-tipping stability then lies in the strength and stiffness of the chassis suspension. Most cranes of this type also have moving counterweights for stabilization beyond that of the outriggers. Loads suspended directly over the rear remain more stable, as most of the weight of the truck crane itself then acts as a counterweight to the load. Factory-calculated charts (or electronic safeguards) are used by the crane operator to determine the maximum safe loads for stationary (outriggered) work as well as (on-rubber) loads and travelling speeds.

Truck cranes range in size from about 14.5 US Tons to about 1200 US tons.

[edit] Rough terrain crane

A crane mounted on an undercarriage with four rubber tires that is designed for pick-and-carry operations and for off-road and "rough terrain" applications. Outriggers that extend horizontally and vertically are used to level and stabilize the crane for hoisting. These telescopic cranes are single-engine machines where the same engine is used for powering the undercarriage as is used for powering the crane, similar to a crawler crane. However, in a rough terrain crane, the engine is usually mounted in the undercarriage rather than in the upper, like the crawler crane.

[edit] Crawler crane

A crawler is a crane mounted on an undercarriage with a set of tracks that provide for the stability and mobility of the crane. Crawler cranes have both advantages and disadvantages depending on their intended use. The main advantage of a crawler is that they can move on site and perform lifts with very little set-up, as the crane is stable on its tracks with no outriggers. In addition, a crawler crane is capable of traveling with a load. The main disadvantage of a crawler crane is that they are very heavy, and cannot easily be moved from one job site to the next without significant expense. Typically, a large crawler must be disassembled or moved by barge in order to be transported.

[edit] Gantry crane
Portainer gantry cranes at the Hamburg Harbour
Portainer gantry cranes at the Hamburg Harbour

A gantry crane has a hoist in a trolley which runs horizontally along gantry rails, usually fitted underneath a beam spanning between uprights which themselves have wheels so that the whole crane can move at right angles to the direction of the gantry rails. These cranes come in all sizes, and some can move very heavy loads, particularly the extremely large examples used in shipyards or industrial installations . A special version is the container crane (or "Portainer" crane, named after the first manufacturer), designed for loading and unloading ship-borne containers at a port.

[edit] Overhead crane

Also known as a "suspended crane", this type of crane works in the same way as a gantry crane but without uprights. The hoist is on a trolley which moves in one direction along one or two beams, which move at right angles to that direction along elevated tracks, often mounted along the side walls of an assembly area in a factory. Some of them can lift very heavy loads.

[edit] Floating crane
SSCV Thialf
SSCV Thialf

Floating cranes are used mainly in bridge building and port construction, but they are also used for occasional loading and unloading of especially heavy or awkward loads on and off ships. Some floating cranes are mounted on a pontoon, others are specialized crane barges with a lifting capacity exceeding 10,000 tonss and have been used to transport entire bridge sections. Floating cranes have also been used to salvage sunken ships.

Crane vessels are often used in offshore construction. The largest revolving cranes can be found on SSCV Thialf, which has two cranes with a capacity of 7,100 metric tons each.

[edit] Vessel (Deck) crane

Located on the ships and used for cargo operations which allows to reduce costs by avoiding usage of the shore cranes. Also vital in small seaports where no shore cranes available. Mostly are electric, hydraulic, electro-hydraulic driven.

[edit] Aerial crane

Aerial cranes usually extend from helicopters to lift large loads. Helicopters are able to travel to and lift in areas that are more difficult to reach by a conventional crane. Aerial helicopter cranes are most commonly used to lift units/loads onto shopping centers, multi-story buildings, highrises, etc. However, they can lift basically anything within their lifting capacity, (i.e. cars, boats, swimming pools, etc.). They also work as disaster relief after natural disasters for clean-up, and during wild-fires they are able to carry huge buckets of water over fires to put them out.

Examples include:

* Sikorsky S-64 Skycrane/Erickson Air Crane - civilian version
* CH-54 Tarhe - military version
* Mi-26 - Russian flying crane helicopter

[edit] Jib crane

A Jib crane is a type of crane where a horizontal member (jib or boom), supporting a moveable hoist, is fixed to a wall or to a floor-mounted pillar. Jib cranes are used in industrial premises and on military vehicles. The jib may swing through an arc, to give additional lateral movement, or be fixed. Similar cranes, often known simply as hoists, were fitted on the top floor of warehouse buildings to enable goods to be lifted to all floors.

[edit] Crane-like machines

The generally-accepted definition of a crane is a machine for lifting and moving heavy objects by means of ropes or cables suspended from a movable arm. As such, a lifting machine that does not use cables, or else provides only vertical and not horizontal movement, cannot strictly be called a 'crane'.

Types of crane-like lifting machine include:

* Block and tackle
* Capstan (nautical)
* Hoist (device)
* Winch
* Windlass

More technically-advanced types of such lifting machines are often known as 'cranes', regardless of the official definition of the term. Some notable examples follow:

[edit] Loader crane
A loader crane offloading aerated concrete bricks at a building site
A loader crane offloading aerated concrete bricks at a building site

A loader crane (also called a knuckle-boom crane) is a hydraulically-powered articulated arm fitted to a truck or trailer, and is used for loading/unloading the vehicle. The numerous jointed sections can be folded into a small space when the crane is not in use. One or more of the sections may be telescopic. Often the crane will have a degree of automation and be able to unload or stow itself without an operator's instruction.

Unlike most cranes, the operator must move around the vehicle to be able to view his load; hence modern cranes may be fitted with a portable cabled or radio-linked control system to supplement the crane-mounted hydraulic control levers.

In the UK, this type of crane is almost invariably known colloquially as a "Hiab", partly because this manufacturer invented the loader crane and was first into the UK market, and partly because the distinctive name was displayed prominently on the boom arm.

[edit] Rolloader crane

This is a loader crane mounted on a chassis with wheels. This chassis can ride on the trailer. Because the crane can move on the trailer, it can be a light crane, so the trailer is allowed to transport more goods.

Manufacturer of rolloader cranes include the Dutch Kennis [1] and the Finnish company Hiab (Hydrauliska Industri AB).

[edit] Stacker crane

A crane with a forklift type mechanism used in automated (computer controlled) warehouses (known as an automated storage and retrieval system (AS/RS)). The crane moves on a track in an aisle of the warehouse. The fork can be raised or lowered to any of the levels of a storage rack and can be extended into the rack to store and retrieve product. The product can in some cases be as large as an automobile. Stacker cranes are often used in the large freezer warehouses of frozen food manufacturers. This automation avoids requiring forklift drivers to work in below freezing temperatures every day.

[edit] Cranes of special interest

* Finnieston Crane (aka the Stobcross Crane)

– Category A -listed example of a 'hammerhead' (cantilever) crane in Glasgow's former docks
– 50m tall, 175 tons capacity, built 1926

* Kockums Crane

– shipyard crane formerly at Kockums, Sweden.
– 138m tall, 1500 tonne capacity, since moved to Ulsan, South Korea

* Samson and Goliath (cranes)

– two gantry cranes at the Harland & Wolff shipyard in Belfast
– Goliath is 96m tall, Samson is 106m
– span 140m, lift-height 70m, capacity 840 tonnes each (1600 tonnes combined)

[edit] Manufacturers

Major manufacturers of cranes include:

* Arcomet
* American Hoist and Derrick
* BaltKran
* Bantom and Spierings.
* Broderson Manufacturing Corp (BMC)
* Bucyrus-Erie
* Demag (Mannesman Dematic)
* Dreggen Crane AS – Design/Engineering, ship and offshore cranes
* Fassi Cranes
* Favelle Favco
* Gorbel Inc.
* Grove
* Heila Cranes (Poviglio, Italy) – truck loaders, marine cranes
* HIAB (Hydrauliska Industri AB) – loader and rolloader cranes
* Hitachi Construction Machinery Co., Ltd.
* Hitachi Construction Machinery (Europe)
* Hitachi Sumitomo Cranes
* HMF (Højbjerg MaskinFabrik) – loader cranes
* Huisman-Itrec
* Koehring
* Konecranes



* Liebherr
* Lorain
* Manitowoc
* Morris Material Handling [2] (purchased by Konecranes [3])
* NCK-Rapier
* North American Industries – overhead bridge cranes, gantry cranes, & monorails
* Northwest
* Palfinger – loader cranes
* P&H – (produced by Morris Material Handling [4])
* PPM
* RDLIFT s.r.l. – tower cranes & self-erecting cranes [5]
* Ruston-Bucyrus
* Sennebogen
* SibtyazhMash
* SPANCO [6]
* Street Crane [www.streetcrane.com]
* Sumitomo
* Terex
* Vetter
* Western Mule Cranes [www.westernmule.com]
* Wolffkran

[edit] Historic

Manufacturers that have now ceased trading as a separate entity:

* Ransomes & Rapier

[edit] Training

* United States
o National Association of Heavy Equipment Training Schools (NAHETS)
o Morrow Equipment Company, L.L.C.

[edit] References

1. ^ a b J. J. Coulton, p.7
2. ^ a b J. J. Coulton, p.14f.
3. ^ a b J. J. Coulton, p.16
4. ^ All data from: Hans-Liudger Dienel, Wolfgang Meighörner, p.13
5. ^ Lynne Lancaster, p.426
6. ^ Lynne Lancaster, p.427ff.
7. ^ Lynne Lancaster, p.434ff.
8. ^ Lynne Lancaster, p.436
9. ^ a b Andrea Matthies, p.514
10. ^ a b Andrea Matthies, p.515
11. ^ a b c d e Michael Matheus, p.345
12. ^ a b Andrea Matthies, p.524
13. ^ Andrea Matthies, p.545
14. ^ Andrea Matthies, p.518
15. ^ Andrea Matthies, p.525f.
16. ^ Andrea Matthies, p.536
17. ^ a b c Andrea Matthies, p.533
18. ^ Andrea Matthies, p.532ff.
19. ^ Andrea Matthies, p.535
20. ^ a b J. J. Coulton, p.6
21. ^ a b Hans-Liudger Dienel, Wolfgang Meighörner, p.17
22. ^ Andrea Matthies, p.534
23. ^ Andrea Matthies, p.531
24. ^ Andrea Matthies, p.540
25. ^ a b Michael Matheus, p.346
26. ^ Michael Matheus, p.347
27. ^ These are Bergen, Stockholm, Karlskrona (Sweden), Kopenhagen (Denmark), Harwich (England), Danzig, Lüneburg, Stade, Otterndorf, Marktbreit, Würzburg, Östrich, Bingen, Andernach and Trier (Germany). Cf. Michael Matheus, p.346

[edit] Literature

History of cranes

* Andrea Matthies: Medieval Treadwheels. Artists' Views of Building Construction, Technology and Culture, Vol. 33, No. 3 (Jul., 1992), pp. 510-547
* Hans-Liudger Dienel, Wolfgang Meighörner, “Der Tretradkran,“ Publication of the Deutsches Museum (Technikgeschichte Series), 2nd ed., München 1997
* J. J. Coulton, “Lifting in Early Greek Architecture,” The Journal of Hellenic Studies, Vol. 94. (1974), pp. 1-19
* Lynne Lancaster, “Building Trajan's Column,” American Journal of Archaeology, Vol. 103, No. 3. (Jul., 1999), pp. 419-439
* Michael Matheus: "Mittelalterliche Hafenkräne," in: Uta Lindgren (ed.): Europäische Technik im Mittelalter. 800-1400, Berlin 2001 (4th ed.), pp. 345-48 ISBN 3-7861-1748-9

[edit] See also
Wikimedia Commons has media related to:
Cranes

[edit] Types of crane

* Container crane (or Portainer)
* Containerlift
* Crane vessel – floating crane
* Gantry crane
* Straddle carrier
* Tow truck

[edit] Other

* Banksman
* Pallet
* Steam shovel
* National Association of Heavy Equipment Training Schools – US educational organisation

[edit] Related ideas

* Skyhook (structure)

[edit] External links

* Worlds 1st Internet TV Channel for The UK Crane Industry
* Overhead Crane Types: bridge crane, gantry crane, & monorail
* Knots, hitches and bends
* VRML Simulation of an Excavator, Tower Crane, and Dumptruck
* Picture Gallery of Overhead Cranes
* A medieval crane at work - Three different VR Panoramas - at the top of a tower on Charles Bridge, Prague, Czech Republic.

Retrieved from "http://en.wikipedia.org/wiki/Crane_%28machine%29"

Categories: Cleanup from March 2007 | All pages needing cleanup | Cranes
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