A treadwheel crane (Latin: magna rota) is a wooden, human powered hoisting and lowering device. It was primarily used during the Roman period and the Middle Ages in the building of castles and cathedrals. The often heavy charge is lifted as the individual inside the treadwheel crane walks. The rope attached to a pulley is turned onto a spindle by the rotation of the wheel thus allowing the device to hoist or lower the affixed pallet.
The Roman Polyspaston crane, from Ancient Greek πολύσπαστον (polúspaston, “compound pulley”), when worked by four men at both sides of the winch, could lift 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 ancient 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 Polyspaston proved to be 60 times more efficient (3000 kg per person). [1] There are two surviving reliefs of Roman treadwheel cranes, the Haterii tombstone from the late first century AD being particularly detailed. De architectura contains a description of Polyspaston crane.
For larger weights of up to 100 t, Roman engineers set up a wooden lifting tower, a rectangular trestle which was so constructed that the column could be lifted upright in the middle of the structure by the means of human and animal-powered capstans placed on the ground around the tower. [2]
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. [3] The earliest reference to a treadwheel (magna rota) reappears in archival literature in France about 1225, [4] followed by an illuminated depiction in a manuscript of probably also French origin dating to 1240. [5] In navigation, the earliest uses of harbor cranes are documented for Utrecht in 1244, Antwerp in 1263, Bruges in 1288 and Hamburg in 1291, [6] while in England the treadwheel is not recorded before 1331. [7]
Generally, vertical transport could be done more safely and inexpensively by cranes than by customary methods. Typical areas of application were harbours, 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 [8] and harbours. [6]
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. [9]
The exact process by which the treadwheel crane was reintroduced is not recorded, [4] 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. [7]
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, [10] giving the possibility of using a thinner shaft and providing thus a greater mechanical advantage. [11]
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. [12] 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. [13]
Less frequently, medieval illuminations also show cranes mounted on the outside of walls with the stand of the machine secured to putlogs. [14]
In contrast to modern cranes, medieval cranes and hoists - much like their counterparts in Greece and Rome [15] - were primarily capable of a vertical lift, and not used to move loads for a considerable distance horizontally as well. [12] 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, [12] 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. [15] 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. [16] Slewing cranes which allowed a rotation of the load and were thus particularly suited for dockside work appeared as early as 1340. [17] 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. [18]
It is noteworthy that medieval cranes rarely featured ratchets or brakes to forestall the load from running backward. [19] This curious absence is explained by the high friction force exercised by medieval treadwheels which normally prevented the wheel from accelerating beyond control. [16]
According to the "present state of knowledge" unknown in antiquity, stationary harbour cranes are considered a new development of the Middle Ages. [6] The typical harbour 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. [6]
Two different types of harbour 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 harbours typically featured tower cranes where the windlass and treadwheels were situated in a solid tower with only jib arm and roof rotating. [20] 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. [21]
Unlike construction cranes where the work speed was determined by the relatively slow progress of the masons, harbour 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. [6] Their capacity was 2–3 tons which apparently corresponded to the customary size of marine cargo. [6] Today, according to one survey, fifteen treadwheel harbour cranes from pre-industrial times are still extant throughout Europe. [22] Some harbour cranes were specialised at mounting masts to newly built sailing ships, such as in Danzig, Cologne and Bremen. [20] Beside these stationary cranes, floating cranes which could be flexibly deployed in the whole port basin came into use by the 14th century. [20]
A treadwheel crane survives at Chesterfield, Derbyshire and is housed in the Museum. It has been dated to the early 14th century and was housed in the top of the church tower until its removal in 1947. It was reconstructed in the Museum for its opening in 1994.
A treadwheel crane survives at Guildford, Surrey, United Kingdom. It dates from the late 17th or early 18th century and formerly stood in Friary Street. It was moved in 1970, having last been used ca. 1960 to move materials for Guildford Cathedral. It is a Scheduled Ancient Monument and a Grade II* listed building. [23]
A treadwheel crane survives at Harwich, Essex, United Kingdom. It was built in 1667 and formerly stood in the Naval Yard. It was moved to Harwich Green in 1932. The crane has two treadwheels of 16 feet (4.88 m) diameter by 3 feet 10 inches (1.17 m) wide on an axle 13+1⁄2 inches (340 mm) diameter. It is the only double wheel treadwheel crane in the United Kingdom. [24] The crane is a Grade II* listed building. [25]
A reconstruction of a 13th-century treadwheel crane can be seen in action at the site Guédelon Castle, Treigny, France. It is used for lifting mortar, rubble, ashlar blocks, and wood. The object of Guédelon Castle is to build a fortress castle using only the techniques and materials of 13th-century medieval France. [26]
Crane Gate (Polish : Brama Żuraw) (German : Krantor), Gdańsk was built before 1366. It was destroyed by the soviet troops during the fighting for the city in early 1945. The brick structure survived, the wooden parts have been restored.
A reconstruction of a double wheel treadwheel crane is in use at Prague Castle, Czech Republic. [27]
A Treadwheel Crane was used in the film Evan Almighty , when Evan complained to God that he needed a crane to construct the Ark in suburban Washington, D.C.
Harwich is a town in Essex, England, and one of the Haven ports on the North Sea coast. It is in the Tendring district. Nearby places include Felixstowe to the north-east, Ipswich to the north-west, Colchester to the south-west and Clacton-on-Sea to the south. It is the northernmost coastal town in Essex.
Medieval fortification refers to medieval military methods that cover the development of fortification construction and use in Europe, roughly from the fall of the Western Roman Empire to the Renaissance. During this millennium, fortifications changed warfare, and in turn were modified to suit new tactics, weapons and siege techniques.
The windlass is an apparatus for moving heavy weights. Typically, a windlass consists of a horizontal cylinder (barrel), which is rotated by the turn of a crank or belt. A winch is affixed to one or both ends, and a cable or rope is wound around the winch, pulling a weight attached to the opposite end. The Greek scientist Archimedes was the inventor of the windlass. The oldest depiction of a windlass for raising water can be found in the Book of Agriculture published in 1313 by the Chinese official Wang Zhen of the Yuan Dynasty.
A wheelbarrow is a small hand-propelled load-bearing vehicle, usually with just one wheel, designed to be pushed and guided by a single person using two handles at the rear. The term "wheelbarrow" is made of two words: "wheel" and "barrow." "Barrow" is a derivation of the Old English "barew" which was a device used for carrying loads.
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 objects 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 transportation for the loading and unloading of freight, in construction for the movement of materials, and in manufacturing for the assembling of heavy equipment.
Harwich Redoubt is a circular fort built in 1808 to defend the port of Harwich, Essex from Napoleonic invasion. The Harwich Society opens it to the public.
Medieval technology is the technology used in medieval Europe under Christian rule. After the Renaissance of the 12th century, medieval Europe saw a radical change in the rate of new inventions, innovations in the ways of managing traditional means of production, and economic growth. The period saw major technological advances, including the adoption of gunpowder, the invention of vertical windmills, spectacles, mechanical clocks, and greatly improved water mills, building techniques, and agriculture in general.
Andernach is a town in the district of Mayen-Koblenz, in Rhineland-Palatinate, Germany, of about 30,000 inhabitants. It is situated towards the end of the Neuwied basin on the left bank of the Rhine between the former tiny fishing village of Fornich in the north and the mouth of the small river Nette in the southeast, just 13 miles (21 km) north of Koblenz, with its five external town districts: Kell, Miesenheim, Eich, Namedy, and Bad Tönisstein.
The Saipem 7000 is the world's third largest semi-submersible crane vessel, after the SSCV Sleipnir and the SSCV Thialf. It is owned by the oil and gas industry contractor Saipem S.p.A.
A treadwheel, or treadmill, is a form of engine typically powered by humans. It may resemble a water wheel in appearance, and can be worked either by a human treading paddles set into its circumference (treadmill), or by a human or animal standing inside it (treadwheel). These devices are no longer used for power or punishment, and the term "treadmill" has come to mean an exercise machine for running, walking or other exercises in place.
A gantry crane is a crane built atop a gantry, which is a structure used to straddle an object or workspace. They can range from enormous "full" gantry cranes, capable of lifting some of the heaviest loads in the world, to small shop cranes, used for tasks such as lifting automobile engines out of vehicles. They are also called portal cranes, the "portal" being the empty space straddled by the gantry.
An overhead crane, commonly called a bridge crane, is a type of crane found in industrial environments. An overhead crane consists of two parallel rails seated on longitudinal I-beams attached to opposite steel columns by means of brackets. The traveling bridge spans the gap. A hoist, the lifting component of a crane, travels along the bridge. If the bridge is rigidly supported on two or more legs running on two fixed rails at ground level, the crane is called a gantry crane or a goliath crane.
Guédelon Castle is a castle currently under construction near Treigny, France. The castle is the focus of an experimental archaeology project aimed at recreating a 13th-century castle and its environment using period techniques, dress, and materials.
A hoist is a device used for lifting or lowering a load by means of a drum or lift-wheel around which rope or chain wraps. It may be manually operated, electrically or pneumatically driven and may use chain, fiber or wire rope as its lifting medium. The most familiar form is an elevator, the car of which is raised and lowered by a hoist mechanism. Most hoists couple to their loads using a lifting hook. Today, there are a few governing bodies for the North American overhead hoist industry which include the Hoist Manufactures Institute, ASME, and the Occupational Safety and Health Administration. HMI is a product counsel of the Material Handling Industry of America consisting of hoist manufacturers promoting safe use of their products.
A bucket is a specialized container attached to a machine, as compared to a bucket adapted for manual use by a human being. It is a bulk material handling component.
Stothert & Pitt was a British engineering company founded in 1855 in Bath, England. It was the builder of various engineering products ranging from Dock cranes to construction plant and household cast iron items. It went out of business in 1989. The name and intellectual property became part of Clarke Chapman.
A fortified tower is one of the defensive structures used in fortifications, such as castles, along with curtain walls. Castle towers can have a variety of different shapes and fulfil different functions.
The Schlachte Cranes were important to the port of Bremen as they enabled heavy loads to be moved off boats on the River Weser. The Schlachte became an important harbour for the city after silting prevented the use of the Balge as a harbour. Today, only the foundations of a 19th-century crane remain on the Weser waterfront.
An elevated entrance is a type of entrance, common in the design of medieval castles, that is not accessible from ground level, but lies at the level of an upper storey. The elevated entrance is the lowest and frequently the only way of entering a fortified building or residence. In the case of circular towers, a large opening in the main wall at ground level was a potential weakness and experts on castle design have argued that the elevated entrance served a structural as well as defensive purpose.
Media related to Treadwheel cranes at Wikimedia Commons