Misplaced Pages

#788211

69-456: It is close to sunset in Paris, and the stevedores work unloading Michele's barge. Giorgetta, Michele's wife, asks her husband if she can bring wine to the workers. He agrees but does not join them because she refuses his kiss. The stevedores start dancing to the music of a nearby organ grinder and one of them steps on Giorgetta's foot. Luigi, a stevedore, dances with her, and it is evident that there

138-531: A longshoreman , stevedore , or docker ) is a waterfront manual laborer who loads and unloads ships . As a result of the intermodal shipping container revolution, the required number of dockworkers has declined by over 90% since the 1960s. The word stevedore ( / ˈ s t iː v ɪ ˌ d ɔːr / ) originated in Portugal or Spain , and entered the English language through its use by sailors . It started as

207-478: A mechanical advantage of 3:1, it has been calculated that a single man working the winch could raise 150 kg (330 lb) (3 pulleys x 50 kg or 110 lb = 150), assuming that 50 kg (110 lb) 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

276-678: A phonetic spelling of estivador ( Portuguese ) or estibador ( Spanish ), meaning a man who loads ships and stows cargo , which was the original meaning of stevedore (though there is a secondary meaning of "a man who stuffs" in Spanish); compare Latin stīpāre meaning to stuff , as in to fill with stuffing . In Ancient and Modern Greek, the verb στοιβάζω (stivazo) means pile up. In Great Britain and Ireland , people who load and unload ships are usually called dockers ; in Australia , they are called stevedores , dockworkers or wharfies ; and, in

345-558: 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. 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

414-635: A concerted action required a great amount of coordination between the work groups applying the force to the capstans. 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 . The earliest reference to a treadwheel ( magna rota ) reappears in archival literature in France about 1225, followed by an illuminated depiction in

483-516: A constant pressure, thus increasing the crane's load capacity considerably. One of his cranes, commissioned by the Italian Navy in 1883 and in use until the mid-1950s, is still standing in Venice , where it is now in a state of disrepair. There are three major considerations in the design of cranes. First, the crane must be able to lift the weight of the load; second, the crane must not topple; third,

552-412: A crane. The containers either leave the port by truck or rail or are stored until they are placed on another ship. Once the ship is offloaded, the containers it leaves with are brought to the dock by truck. A crane lifts the containers from the trucks onto the ship. As the containers pile up on the ship, the workers connect them to the vessel and the other already-placed containers. The jobs involved include

621-407: A height of about 34 m (111.5 ft) (see construction of Trajan's Column ). It is assumed that Roman engineers lifted these extraordinary weights by two measures (see picture below for comparable Renaissance technique): 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

690-524: A manuscript of probably also French origin dating to 1240. In navigation, the earliest uses of harbor cranes are documented for Utrecht in 1244, Antwerp in 1263, Bruges in 1288 and Hamburg in 1291, while in England the treadwheel is not recorded before 1331. Generally, vertical transport could be done more safely and inexpensively by cranes than by customary methods. Typical areas of application were harbors, mines, and, in particular, building sites where

759-609: A much greater lifting capability than was previously possible, although manual cranes are still utilized where the provision of power would be uneconomic. There are many different types of cranes, 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, to facilitate constructions by reaching tight spaces. Large floating cranes are generally used to build oil rigs and salvage sunken ships. Some lifting machines do not strictly fit

SECTION 10

#1732881060789

828-408: A point over the center of gravity, they are regarded by archaeologists as the positive evidence required for the existence of the crane. 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 200 years, Greek building sites witnessed a sharp reduction in the weights handled, as the new lifting technique made

897-517: A port for a limited amount of time, so their work must be completed quickly. In earlier days before the introduction of containerization , men who loaded and unloaded ships had to tie down cargoes with rope. A type of stopper knot is called the stevedore knot . Securely tying up parcels of goods is called stevedore lashing or stevedore knotting . While loading a general cargo vessel, they use dunnage , which are pieces of wood (or nowadays sometimes strong inflatable dunnage bags ) set down to keep

966-443: A vertical lift, and not used to move loads for a considerable distance horizontally as well. 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, 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

1035-422: Is distressed about being twice her age; she comforts him but she still will not kiss him, and goes off. Michele wonders aloud if Giorgetta is still faithful to him and ponders who might have changed her so much. He reviews the list of men who have shared in their lives but dismisses each of them as improbable. Michele lights his pipe and Luigi, seeing it from afar, thinks that it is Giorgetta's signal. He returns to

1104-455: Is near the deck. Additionally, the DLF increases further when lifting objects that are underwater or going through the splash zone. The wind speeds tend to be higher than onshore as well. Though actual DLF values are determined through crane tests under representative operational conditions, design specifications can be used for guidance. The values vary according to the specification, which reflects

1173-477: Is not enough work in Rouen. When they are alone, Giorgetta asks Luigi why he requested to be dismissed; the pair acknowledge their love. They plan to meet later that evening upon the signal of a match being lit on board. By now Luigi seems determined to kill Michele and flee with Giorgetta. Michele later reminisces with Giorgetta of the days before their child died and how he could cover the two of them under his cloak. He

1242-418: Is noteworthy that medieval cranes rarely featured ratchets or brakes to forestall the load from running backward. This curious absence is explained by the high friction force exercised by medieval tread-wheels which normally prevented the wheel from accelerating beyond control. According to the "present state of knowledge" unknown in antiquity, stationary harbor cranes are considered a new development of

1311-427: Is something between them. Upon hearing of Michele's return the stevedores' gathering breaks up. Work is getting scarce and Giorgetta and Michele discuss which of the stevedores should be dismissed; she prefers that it be anyone other than Luigi despite him being Michele's first choice. Soon the conversation turns into a fight. La Frugola enters, looking for Talpa, her husband and one of the stevedores. She shows everyone

1380-405: Is usually part of the crane's type approval . In offshore lifting, where the crane and/or lifted object are on a floating vessel, the DLF is higher compared to onshore lifts because of the additional movement caused by wave action. This motion introduces additional acceleration forces and necessitates increased hoisting and lowering speeds to minimize the risk of repeated collisions when the load

1449-539: The Elswick works at Newcastle , to produce his hydraulic machinery for cranes and bridges in 1847. His company soon received orders for hydraulic cranes from Edinburgh and Northern Railways and from Liverpool Docks , as well as for hydraulic machinery for dock gates in Grimsby . The company expanded from a workforce of 300 and an annual production of 45 cranes in 1850, to almost 4,000 workers producing over 100 cranes per year by

SECTION 20

#1732881060789

1518-668: The United States and Canada , the term longshoreman , derived from man-along-the-shore (or alongshore + man ), is used. Before the extensive use of container ships and shore-based handling machinery in the United States, longshoremen referred exclusively to the dockworkers, while stevedores , part of a separate trade union , worked on the ships operating their cranes and moving cargo. Dockworkers, also known as longshoremen and stevedores, have existed since ancient times. The role of dockworkers has evolved significantly over

1587-586: The lever and pulley , to create mechanical advantage to do its work. Cranes are commonly employed in transportation for the loading and unloading of freight, in construction for the movement of materials, and in manufacturing for the assembling of heavy equipment . The first known crane machine was the shaduf , a water-lifting device that was invented in ancient Mesopotamia (modern Iraq) and then appeared in ancient Egyptian technology . Construction cranes later appeared in ancient Greece , where they were powered by men or animals (such as donkeys), and used for

1656-480: 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 instance, the architrave blocks weigh up to 60 tons each, and one corner cornice block even over 100 tons, all of them raised to a height of about 19 m (62.3 ft). In Rome , the capital block of Trajan's Column weighs 53.3 tons, which had to be lifted to

1725-456: The shape-up . Dock workers have been a prominent part of the modern labor movement . Former stevedores and dockworkers include: Crane (machine) A crane is a machine used to move materials both vertically and horizontally, utilizing a system of a boom , hoist , wire ropes or chains , and sheaves for lifting and relocating heavy objects within the swing of its boom. The device uses one or more simple machines , such as

1794-455: 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. The exact process by which the treadwheel crane was reintroduced is not recorded, although its return to construction sites has undoubtedly to be viewed in close connection with the simultaneous rise of Gothic architecture. The reappearance of

1863-456: The 361 t heavy Vatican obelisk in Rome. From his report, it becomes obvious that the coordination of the lift between the various pulling teams required a considerable amount of concentration and discipline, since, if the force was not applied evenly, the excessive stress on the ropes would make them rupture. Cranes were also used domestically during this period. The chimney or fireplace crane

1932-426: The DLF. More sophisticated methods, such as finite element analysis or other simulation techniques, may also be used to model the crane's behavior under various loading conditions, as deemed appropriate by the designer or certifying authority.To verify the actual DLF, control load tests can be conducted on the completed crane using instrumentation such as load cells , accelerometers , and strain gauges . This process

2001-882: The Middle Ages. 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. Their capacity was 2–3 tons, which apparently corresponded to the customary size of marine cargo. Today, according to one survey, fifteen treadwheel harbor cranes from pre-industrial times are still extant throughout Europe. Some harbour cranes were specialised at mounting masts to newly built sailing ships, such as in Gdańsk , Cologne and Bremen . Beside these stationary cranes, floating cranes , which could be flexibly deployed in

2070-411: The Middle Ages. 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 . Two different types of harbor cranes can be identified with a varying geographical distribution: While gantry cranes, which pivoted on

2139-600: The above definition of a crane, but are generally known as cranes, such as stacker cranes and loader cranes. Cranes were so called from the resemblance to the long neck of the bird , cf. Ancient Greek : γερανός , French grue . The first type of crane machine was the shadouf , which had a lever mechanism and was used to lift water for irrigation . It was invented in Mesopotamia (modern Iraq) circa 3000 BC. The shadouf subsequently appeared in ancient Egyptian technology circa 2000 BC. A crane for lifting heavy loads

Il tabarro - Misplaced Pages Continue

2208-469: The autocratic societies of Egypt or Assyria . 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

2277-492: The barge and is confronted by Michele. In the ensuing fight, Michele disarms Luigi and forces him to confess his affair with Giorgetta before strangling him to death and hiding Luigi's body under his cloak. Giorgetta returns to the barge, approaching him remorsefully after their fight earlier, and when she is close enough Michele opens his cloak to reveal her dead lover, Luigi's lifeless body falling on Giorgetta. Notes Sources Stevedores A dockworker (also called

2346-428: The cargo out of any water that might be lying in the hold or are placed as shims between cargo crates for load securing . Today, the vast majority of non- bulk cargo is transported in intermodal containers . The containers arrive at a port by truck, rail, or another ship and are stacked in the port's storage area. When the vessel that will be transporting them arrives, the containers it is offloading are unloaded by

2415-406: The centuries as maritime trade has grown and modernized: Loading and unloading ships requires knowledge of the operation of loading equipment, the proper techniques for lifting and stowing cargo , and the correct handling of hazardous materials . In addition, workers must be physically strong and able to follow orders attentively. Many longshoremen are needed to unload a ship. A ship can only be at

2484-405: The column in the middle of the structure ( Mechanica 3.5). 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). This use of multiple capstans is also described by Ammianus Marcellinus (17.4.15) in connection with

2553-594: 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

2622-512: The construction of buildings. Larger cranes were later developed in the Roman Empire , 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

2691-447: The construction of the ancient Egyptian pyramids , where about 50 men were needed to move a 2.5 ton stone block up the ramp (50 kg (110 lb) per person), the lifting capability of the Roman polyspastos proved to be 60 times higher (3,000 kg or 6,600 lb per person). However, numerous extant Roman buildings which feature much heavier stone blocks than those handled by

2760-464: The crane must not fail structurally. For stability, the sum of all moments about the base of the crane must be close to zero so that the crane does not overturn. 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, thus providing a safety margin. Under United States standards for mobile cranes,

2829-439: The crane operators, the workers who connect the containers to the ship and each other, the truck drivers who transport the containers from the dock and storage area, the workers who track the containers in the storage area as they are loaded and unloaded, as well as various supervisors. Those workers at the port who handle and move the containers are likely to be considered stevedores or dockworkers. Before containerization, freight

Il tabarro - Misplaced Pages Continue

2898-409: The cylinder and a valve regulated the amount of fluid intake relative to the load on the crane. This mechanism, the hydraulic jigger , then pulled on a chain to lift the load. In 1845 a scheme was set in motion to provide piped water from distant reservoirs to the households of Newcastle . Armstrong was involved in this scheme and he proposed to Newcastle Corporation that the excess water pressure in

2967-474: The design dynamic factor, is a critical parameter in the crane design and operation. It accounts for the dynamic effects that can increase the load on a crane's structure and components during lifting operations. These effects include: The DLF for a new crane design can be determined with analytical calculations and mathematical models following the relevant design specifications . If available, data from previous tests of similar crane types can be used to estimate

3036-417: The dynamic load on the crane due to vessel motion. Additionally, the stability of the vessel or platform must be considered. For stationary pedestal or kingpost mounted cranes, the moment produced by the boom, jib, and load is resisted by the pedestal base or kingpost. Stress within the base must be less than the yield stress of the material or the crane will fail. The dynamic lift factor (DLF), also known as

3105-462: The early 1860s. Armstrong spent the next few decades constantly improving his crane design; his most significant innovation was the hydraulic accumulator . Where water pressure was not available on site for the use of hydraulic cranes, Armstrong often built high water towers to provide a supply of water at pressure. However, when supplying cranes for use at New Holland on the Humber Estuary , he

3174-457: 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 , 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

3243-452: 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 preferable to the Greek polis over the more labour-intensive ramp which had been the norm in

3312-492: The fruits of her scavenging in Paris and scolds the men for their drinking. Luigi laments his lot in life, and La Frugola sings of her wish to one day buy a house in the country where she and her husband can retire. Giorgetta and Luigi sing a duet about the town where they were both born. The stevedores depart except for Luigi, who asks Michele to dismiss him and let him off in Rouen , but Michele convinces him against this, saying there

3381-456: 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. 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

3450-562: The lifting of the Lateranense obelisk in the Circus Maximus (c. 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. Lifting such heavy weights in

3519-572: The lower masts of the vessel under construction or repair. These lower masts were the largest and most massive single timbers aboard a ship, and erecting them without the assistance of either a sheer hulk or land-based masting sheer was extremely difficult. The concept of sheer hulks originated with the Royal Navy in the 1690s, and persisted in Britain until the early nineteenth century. Most sheer hulks were decommissioned warships; Chatham , built in 1694,

SECTION 50

#1732881060789

3588-538: The lower part of town could be used to power one of his hydraulic cranes for the loading of coal onto barges at the Quayside . He claimed that his invention would do the job faster and more cheaply than conventional cranes. The corporation agreed to his suggestion, and the experiment proved so successful that three more hydraulic cranes were installed on the Quayside. The success of his hydraulic crane led Armstrong to establish

3657-491: The maximum load. The polyspastos , when worked by four men at both sides of the winch, could readily lift 3,000 kg (6,600 lb) (3 ropes x 5 pulleys x 4 men x 50 kg or 110 lb = 3,000 kg or 6,600 lb). If the winch was replaced by a treadwheel, the maximum load could be doubled to 6,000 kg (13,000 lb) 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

3726-418: The more sophisticated compound pulley must have found its way to Greek construction sites by then. The heyday of the crane in ancient times came during the Roman Empire , when construction activity soared and buildings reached enormous dimensions. The Romans adopted the Greek crane and developed it further. There is much available information about their lifting techniques, thanks to rather lengthy accounts by

3795-442: The observation of the labor-saving qualities of the waterwheel with which early treadwheels shared many structural similarities. 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

3864-546: 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. These requirements, along with additional safety-related aspects of crane design, are established by the American Society of Mechanical Engineers in the volume ASME B30.5-2018 Mobile and Locomotive Cranes . Standards for cranes mounted on ships or offshore platforms are somewhat stricter because of

3933-404: 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

4002-568: 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 and harbors. Apart from treadwheels, medieval depictions also show cranes to be powered manually by windlasses with radiating spokes , cranks and by

4071-436: The type of crane and its usage. Here are some example typical values: The methods for determining the DLF vary in the different crane specifications. The following formulas are examples from one specification. The working load (suspended load) is the total weight that a crane is designed to safely lift under normal operating conditions. It is W = g ⋅ ( m w l l + m

4140-470: The use of several smaller stones more practical than fewer larger ones. In contrast to the archaic period with its pattern of ever-increasing block sizes, Greek temples of the classical age like the Parthenon invariably featured stone blocks weighing less than 15–20 metric tons. Also, the practice of erecting large monolithic columns was practically abandoned in favour of using several column drums. Although

4209-463: The vaulting and below the roof, where they remained after building construction for bringing material for repairs aloft. Less frequently, medieval illuminations also show cranes mounted on the outside of walls with the stand of the machine secured to putlogs . In contrast to modern cranes, medieval cranes and hoists — much like their counterparts in Greece and Rome  — were primarily capable of

SECTION 60

#1732881060789

4278-538: The wall. 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. Slewing cranes which allowed a rotation of the load and were thus particularly suited for dockside work appeared as early as 1340. 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 . It

4347-473: The wheel rim, giving the possibility of using a thinner shaft and providing thus a greater mechanical advantage. 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

4416-451: The whole port basin came into use by the 14th century. A sheer hulk (or shear hulk) was used in shipbuilding and repair as a floating crane in the days of sailing ships , primarily to place the lower masts of a ship under construction or repair. Booms known as sheers were attached to the base of a hulk's lower masts or beam, supported from the top of those masts. Blocks and tackle were then used in such tasks as placing or removing

4485-460: Was developed by the Ancient Greeks in the late 6th century BC. 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 center of gravity of the block, or in pairs equidistant from

4554-425: Was often handled with a longshoreman’s hook , a tool which became emblematic of the profession (mainly on the west coast of the United States and Canada). Traditionally, stevedores had no fixed job but would arrive at the docks in the morning seeking employment for the day. London dockers called this practice standing on the stones , while in the United States, it was referred to as shaping up or assembling for

4623-455: Was the first of only three purpose-built vessels. There were at least six sheer hulks in service in Britain at any time throughout the 1700s. The concept spread to France in the 1740s with the commissioning of a sheer hulk at the port of Rochefort. A lifting tower similar to that of the ancient Romans was used to great effect by the Renaissance architect Domenico Fontana in 1586 to relocate

4692-441: Was unable to do this, because the foundations consisted of sand. He eventually produced the hydraulic accumulator, a cast-iron cylinder fitted with a plunger supporting a very heavy weight. The plunger would slowly be raised, drawing in water, until the downward force of the weight was sufficient to force the water below it into pipes at great pressure. This invention allowed much larger quantities of water to be forced through pipes at

4761-413: Was used to swing pots and kettles over the fire and the height was adjusted by a trammel . With the onset of the Industrial Revolution the first modern cranes were installed at harbours for loading cargo. In 1838, the industrialist and businessman William Armstrong designed a water-powered hydraulic crane . His design used a ram in a closed cylinder that was forced down by a pressurized fluid entering

#788211