crane

from Wikipedia, the free encyclopedia
Gantry slewing crane with fixed jib
A gantry luffing crane - the assembly boar in Eberswalde
Small gantry crane on rails
Image of a boom from a normal construction crane.
Image of a boom from a normal construction crane.
Bridge crane
Construction site cranes
Dock leveler
Mobile crane
Pillar crane
Travel lift
Pressurized water slewing crane in Bremerhaven (1899)
Mobile crane on a Unimog U423 (2014)

A crane (plural: cranes or cranes - cranes is usually as a colloquial, cranes considered fachsprachlich; etymologisch related to altgriech. Ὁ γέρανος the crane) is a manually or by motor -operated means for the vertical and horizontal loading or movement of loads. It is generally used for loading and unloading ships ( general cargo and containers ), railways and trucks, as well as in assembly , production and storage halls and in building construction.

In the version for handling bulk goods, it is usually referred to as an excavator .

The difference to a simple hoist , which can be part of the crane, is that the crane works floor-free and can execute more than two directions of movement (up / down - left / right corresponds to two coordinate directions) (three-dimensional work area) - i.e. H. to put the load down at a different point than when he picked it up.

The main application is loading and unloading, also known as cargo handling , as well as loading goods at a certain point (short distances). The latter application is particularly important on construction sites .

Crane types

There are different types and designs depending on the area of ​​application.

Differentiation according to the mast construction

Movable jib cranes are mobile cranes called.

In 1949, Hans Liebherr designed the world's first mobile tower crane , the TK 8 , with moderate success at the beginning.

various

Helicopters , cable cars , balloons and kites (ferries) can function as a crane if necessary. However, their use is usually limited to impassable areas or for work on very tall structures because of the high operating costs. Helicopter types specially designed for crane use are: K-Max , Sikorsky S-64 Skycrane, Mil Mi-10 . A test balloon was the CargoLifter CL75 AirCrane with a payload of 75 t in 2001/2001 .

The following tools are functionally similar: fishing rod , ship hook , gripping aid , poker hook , hook rod to manipulate clothes on hangers on high poles or to tip small boxes down from high shelves.

30 cranes on 21 hectares moved at dusk on February 15, 2014 as a ballet choreographed with light effects for the 15-minute Kranensee symphony , composed by Florian Reithner, on the large construction site of the Seestadt Aspern in northeastern Vienna . The construction companies celebrated the first roof matches and 14,000 came to watch. Crane ballets were performed as early as 1996 when Potsdamer Platz was redesigned in Berlin and in 2010 as a requiem for the cranes in HafenCity Hamburg.

The term crane ballet has been used in recent years as a decorative description for the mere collection of cranes, for example on large construction sites.

etymology

The lifting device consists of a vertical column and a rotatable, usually obliquely upward boom reminiscent of a standing to the long neck and beak crane . That is why the Greeks named the construction after the bird. In the Middle Ages, the original crane became the abbreviation Krahn or Krahnen (e.g. old krahnen ), later crane .

History of the cranes

Ancient Greek cranes

Greco-Roman Trispastos ("3- roller train "), the simplest ancient crane type (150 kg load)
Greco-Roman Pentaspastos ("5- roller train "), a medium-sized variant (approx. 450 kg load)

The crane for lifting heavy loads was introduced in the late 6th century BC. Invented by the ancient Greeks . Characteristic notches for the use of lifting tongs and Lewis irons are from around 515 BC. Proven on stone blocks of Greek temples. Because these grooves are either above the center of gravity of the block or in pairs, equidistant from a point above the center of gravity, archaeologists consider them sufficient evidence of the existence of cranes.

The introduction of hoisting machines, which worked with a cable winch and pulley system , led to the extensive replacement of the ramp as the main aid for vertical transport. In the two centuries that followed, there was a strong trend towards lighter loads on Greek construction sites. In contrast to the archaic period (700–500 BC), in which the size of the stone blocks used continued to increase, classical Greek temples such as the Parthenon consist of blocks that weigh less than 15 to 20 tons. In addition, they moved away from the previous practice of erecting large monolithic columns and switched to assembling columns from several drums.

Although the historical background to the introduction of the crane remains unclear, it is believed that the unstable social and political situation in Greece favored the employment of smaller and professional construction teams. This made the use of cranes appear more attractive to the polis than the ramp technique, which required the mass deployment of workers and was common in the autocratic societies of Egypt or Assyria .

The first unambiguous written evidence of a multi-role train can be found in the mechanical problems ( Mechanika 18, 853a32–853b13), which Aristotle (384–322 BC) are ascribed to, but were possibly written a little later. At around the same time, the stone blocks of the Greek temples reached the size of their archaic predecessors again, which indicates that the multi-roller train must have found its way into Greek construction sites at this time.

Ancient Roman cranes

Reconstruction of a 10.4 m high Roman polyspasto in Bonn
Reconstruction of a Roman construction crane in Xanten

Cranes played a particularly important role in the building industry of the Romans , where there was a lot of construction activity and whose buildings reached enormous dimensions. The Romans took over the crane from the Greeks and developed it further. Thanks to the relatively extensive treatises by the Roman engineers Vitruvius ( De Architectura 10, 2, 1-10) and Heron of Alexandria ( Mechanica 3, 2-5), we are relatively well informed about Roman lifting technology. Images of Roman treadwheel cranes can be found on two ancient reliefs , of which the Haterii tombstone from the late 1st century AD is particularly detailed.

The simplest Roman crane was a three-roller hoist , which was appropriately named Trispastos and consisted of a lifting beam , reel , rope and a block and tackle with three rollers, which corresponds to a transmission ratio of 3 to 1. According to calculations, a single worker at the reel - assuming that 50 kg represents the maximum effort that a man can exert over a longer period of time - could lift a weight of 150 kg with the Trispastos (3 rolls of 50 kg = 150 kg ). Heavy crane types had more complex pulley blocks with five rollers (Pentaspastos) or, in the case of the largest crane, even three times five rollers ( Polyspastos ) and had two, three or four lifting masts depending on the maximum load. The Polyspastos was able to lift 3000 kg in reel operation with four men (3 ropes × 5 pulleys × 4 men × 50 kg = 3000 kg). If the reel was replaced by a pedal bike , the maximum weight even doubled to 6000 kg with half the crew, since the pedal bike has a much larger gear ratio thanks to its larger diameter. This means that the maximum lifting force of the Roman polyspastos of 3000 kg per person was sixty times greater than when building the pyramids , where it took around 50 workers to move a 2.5 t stone block up the ramp (50 kg per person).

Archaeological evidence suggests that the Romans had the technical ability to transport significantly larger loads vertically, because in numerous Roman buildings there are much heavier stone blocks in higher elevations than the Polyspastus could handle. So weigh z. For example, the architraves of Jupiter temple in Baalbek are that m is approximately 19 above the ground, each of up to 60 t and the blocks of the Eckgesims even more than 100, t during the 53.3 ton Kapitellblock the Trajanssäule in Rome on a height of approx. 34 m was hoisted.

It is believed that Roman engineers were able to cope with these extraordinary loads by two means: First, as suggested by Heron, a wooden lifting tower was built, the four sides of which were in the shape of a square with parallel sides, not unlike a siege tower , but with the column in the middle of the construction ( Mechanica 3, 5). Second, a multitude of windlasses were placed at the base of the tower, which were manned by crews. Despite their smaller leverage ratio, anchor winches were preferred to pedal bikes because they could be set up in larger numbers and operated by more workers (and draft animals). The use of anchor winches is described by Ammianus Marcellinus (17, 4, 15) when erecting the Obelisco Lateranense in the Circus Maximus (approx. 357 AD). The maximum lifting capacity of antique windlass can be determined by the number of Lewis iron holes drilled in the monolith . In the case of the architrave blocks from Baalbek, which weigh between 55 and 60 t, eight holes indicate the use of as many anchor winches with an individual maximum load of 7.5 t (60 t / 8 holes = 7.5 t). Lifting such large loads in a concerted effort required a high degree of concentration and coordination from the work groups on the anchor winches.

Medieval cranes

Modern reconstruction of the medieval slewing crane in the port of Bruges (smaller scale)
Medieval harbor crane in the former Hanseatic city of Gdansk

After the pedal crane had fallen out of use in Western Europe with the fall of the Western Roman Empire , lifting technology found its way back into use on a large scale in the High Middle Ages . The earliest mention of a treadmill (magna rota) appears in French sources around 1225, followed by an illustration in a manuscript from 1240, which is probably also of French origin. In shipping, the earliest use of harbor cranes for Utrecht in 1244, Antwerp in 1263, Bruges in 1288 and Hamburg in 1291 is documented, while in England the pedal bike can be seen for the first time in 1331.

In general, vertical transportation with cranes was safer and cheaper than conventional methods. Typical areas of application were harbors, mines and, in particular, construction sites, where the step-wheel crane played a key role in the construction of the towering Gothic cathedrals . Nevertheless reveals itself based on contemporary sources and illustrations that newly introduced machines like treadmills and wheelbarrows more labor-intensive methods, such as ladders and carrying stretchers could not completely replace. Rather, old and new machines were used side by side in medieval construction and port operations.

Aside from treadmills, medieval depictions show cranes that are driven manually by winches with star-shaped spokes, cranks and, since the 15th century, by winches shaped like a steering wheel . Flywheels , which compensate for irregularities in the drive and help overcome dead spots in the lifting process, have been known since 1123.

Origins

The exact process that led to the reuse of the pedal crane is not known, but its return to medieval construction sites must undoubtedly be seen in close connection with the simultaneous rise of Gothic . The pedal crane could be a technical advancement of the winch , from which its structure and mechanics derive. Alternatively, the medieval treadmill could be a deliberate reinvention of the Roman crane, as described in Vitruvius 's De architectura , which was part of the inventory of many monastery libraries. Likewise, its reintroduction may have been inspired by observing the labor-saving qualities of waterwheels , with which early treadle designs had many similarities.

Structure and placement

The medieval treadmill consisted of a large, wooden wheel that rotated around an axle and had a tread wide enough for two workers to walk next to each other. While early 'compass-type' wheels had the spokes directly in the axle, more advanced 'bracket-type' models had arms attached to the side of the axle. This arrangement enabled the use of a thinner drive shaft, which increased the mechanical lever.

Contrary to what is often assumed, medieval construction cranes were neither erected on the light scaffolding that was customary at the time, nor on the thin walls of the Gothic cathedrals, which did not have the load-bearing capacity to take the added weight of the tractor and load. Rather, the cranes were placed on the ground in the first construction phase, often inside the building. As soon as one floor was built and massive tie beams connected the side walls, the crane was dismantled and reassembled on the roof beams, where it was moved from field to field during the construction of the vaults. In this way, the crane "grew" and "migrated" with the building, so that nowadays all existing medieval construction cranes in England are in church towers above the vaults and below the roof, where they remained after the construction work was completed to pick up materials for repairs .

Less common medieval representations show cranes on the outside of the walls, where the frame of the machine was attached to protruding beams.

Operation and Mechanism

Tower crane from 1413 in the Trier inland port, 2nd jib for counter load

In contrast to modern cranes, medieval cranes - just like their ancient predecessors - hardly moved loads in a horizontal direction, but were primarily only suitable for vertical lifting operations. The lifting work at the workplace was organized accordingly. It is assumed that in building construction the crane either lifted the stone blocks directly from the ground into their place, or from a point opposite the center of the wall, so that the two work teams that worked at both ends of the wall can be supplied with building material could.

In addition, the crane foreman, who usually directed the workers in the treadmill from outside the crane, carried the load on a small rope with which he could swing the load sideways. Slewing cranes, which allowed the load to rotate and were therefore particularly suitable for unloading work on the harbor quay, can be verified as early as 1340. While ashlar stones were lifted with slings, Lewis irons or lifting tongs ('devil's claws'), other objects could be transported with containers such as baskets , wooden boxes , pallets or barrels .

It's worth noting that the medieval crane rarely had pawls or brakes to keep the load from running backwards. This is explained by the high frictional forces that normally prevented the wheel from accelerating uncontrollably.

Harbor cranes

For port cranes that have been preserved in Germany from the Middle Ages and early modern times, see port crane .
Crane from 1749 in Copenhagen for erecting masts for sailing ships

Stationary harbor cranes - unknown in antiquity according to current knowledge - are seen as a new development from the Middle Ages. The typical harbor crane was a rotating construction equipped with two treadmills. These cranes were built for loading and unloading freight directly on the quay, where they replaced or supplemented older lifting methods such as winches , seesaws and yards .

Two types of harbor cranes with different geographical focuses can be identified: On the one hand, gantry cranes , the entire construction of which rotated around a central, vertical axis and which were usually found in Flemish and Dutch coastal towns. On the other hand, tower cranes , in which the cable winch and running wheels were in a fixed tower and only the jib and roof structure rotated with the load. This type was widespread in German sea and inland ports. Interestingly, quay cranes have not been adopted in the Mediterranean or in the highly developed Italian port cities, where authorities made use of the more labor-intensive method of unloading via ramps beyond the Middle Ages.

In contrast to construction cranes, in which the work speed was determined by the relatively slow work rhythm of the bricklayers, harbor cranes usually had a double treadle wheel to speed up the loading process. The two pedal wheels, the diameter of which is estimated to be 4 m and more, were attached to both sides of the crane axis and turned together. According to an investigation, fifteen pedal-wheel harbor cranes from pre-industrial times still exist in Europe today. In addition to these stationary cranes, floating cranes appeared in the 14th century that could be used flexibly throughout the port basin.

safety

Driver's license for crane operators, 1998

Before a crane (hoist) is put into operation for the first time in Germany, an acceptance test in accordance with BGG 905 ( employers' liability insurance association principles ) by an expert authorized by the employers liability insurance association is required. This acceptance test ranges from the inspection of the documents available for a crane to the examination of all safety-relevant functions, safety clearances and adjacent areas. For a more detailed explanation in this context u. a. Reference is made to the accident prevention regulation for cranes BGV D 6. The annually recurring inspection must then be carried out by an expert (BGV D 6 §26).

A crane driver's license in Germany and a crane driver's license in Switzerland are required to operate a crane ( Art. 5 Para. 2a Crane Ordinance).

The operation of cranes, the training of crane drivers (in Germany according to BGG 921, in Switzerland according to Art. 8 ff. Crane Ordinance) and the safe use of cranes are subject to strict regulations. So contradicts z. B. the often observed anti-theft device on construction sites, in which devices are hung on the crane overnight, the obligations of the crane operator according to § 30, paragraph 11 of the BGV D6. Operating instructions regulate the handling of the respective cranes on the basis of legal regulations.

Today, the safety of crane systems is supported by intelligent controls of both cranes and wire rope hoists.

Museum cranes

Well-known cranes

The medieval Cologne Cathedral crane, photo by Theodor Creifelds , 1868, shortly before dismantling

Increasing the efficiency of cranes

In the case of cranes made of welded metal structures , post-weld treatment can significantly increase the service life or, if taken into account during development, the transferable load level (lifting load). In the case of existing structures, post-weld treatment can often extend the service life by many years. By taking this into account during a new design , the crane structure can be designed to be lighter in a targeted manner. In most cases, this leads to an increase in the permissible lifting capacity and thus to an increase in efficiency .

See also

literature

Monographs

  • Jünemann / Schmidt: Material flow systems , ISBN 3-540-65076-8
  • Martin Scheffler u. a .: conveyors, vol. 1, hoists, elevators, industrial trucks , Friedr. Vieweg & Sohn Verlagsgesellschaft mbH, Braunschweig / Wiesbaden, 1998, ISBN 3-528-06626-1 This volume describes the mode of operation, design and design of load handling equipment, series hoists, hoists, vehicle cranes, elevators, wagons and tugs, forklifts, automated guided vehicles and storage and retrieval systems .
  • Rudolf Becker: The big book of the mobile cranes , Volume 1 - manual of the vehicle crane technology , KM-Verlags GmbH, ISBN 3-934518-00-1
  • Rudolf Saller: The large book of mobile cranes , Volume 2 - manual for crane operators , KM-Verlags GmbH, ISBN 3-934518-04-4
  • KM-Verlag: 50 years of Demag mobile cranes , KM-Verlags GmbH, ISBN 3-934518-03-6
  • Walter Lütche: Giants of work , 40 years of mobile crane construction in the GDR -das Typbuch-, KM-Verlags GmbH, 64560 Riedstadt, ISBN 3-934518-05-2
  • Oliver Bachmann, Heinz-Herbert Cohrs, Tim Whiteman, Alfred Wislicki: The fascination of construction machinery - crane technology from antiquity to modern times , Giesel Verlag für Publizität GmbH, 1997, ISBN 3-9802942-6-9
  • Hans-Otto Hanover, Fritz Mechtold, Jürgen Koop, Dieter Lenzkes: Sicherheit bei Kranen , 7th edition, Springer Verlag Berlin Heidelberg New York, ISBN 3-540-62730-8
  • Ing.Hans Werner Friedrich, Obering. Ulrich Wiese: Textbook for hoist operators , 3rd edition, Verlag Technik Berlin, 1990, ISBN 3-341-00777-6
  • Siegfried Zimmermann, Bernd Zimmermann: Crane Operator Training , Verlag Ingo Resch, 82156 Graefelfing, ISBN 3-930039-31-1
  • Christoph Seeßelberg : crane tracks - dimensioning and structural design ; 3. Edition; Bauwerk-Verlag Berlin 2009; ISBN 978-3-89932-218-7

Magazine articles

  • Gernot Kotte: Mobile crane instead of tower crane? When are mobile cranes beneficial? In: bd baumaschinendienst, issue 4, April 1989, pp. 398–402
  • Heinz Herbert Cohrs: Load torque limiter and crane electronics. In: Förder und Heben, Mainz, 1989, issue 12, pp. 1008-1010
  • Modern mobile cranes for construction. Market and technology in motion. In: BMT Baumaschine und Bautechnik 37, 1990, issue 5, pp. 244–247
  • Günter Otto: The development of the telescopic crane. In: Deutsche Hebe- und Fördertechnik, Ludwigsburg, 1992, issue 6, issue 6, pp. 44–49 (part I) and issue 7/8, pp. 34 and 37 (part II)
  • Josef Theiner: New and further developments in mobile cranes . In: Deutsche Hebe- und Fördertechnik, Ludwigsburg, 1998, issue 9, pp. 28–34
  • Ulrich Hamme, Josef Hauser, Andreas Kern, Udo Schriever: Use of high-strength structural steels in mobile crane construction. In: Stahlbau 69, 2000, issue 4, pp. 295–305
  • G. Scheffels: Limits in sight? State of the art and trends in boom technology. ( Telescopic cranes ) In: Förder und Heben, Mainz, 2000, issue 6, pp. 439–441
  • Jacques Maffini: Control systems for medium and large mobile cranes. In: Hebezeuge und Fördermittel, Berlin, 2001, issue 11, pp. 528-530
  • Wolfgang Beringer: The triumphant advance of mobile cranes. In: Deutsche Hebe- und Fördertechnik, Ludwigsburg, 2004, issue 6, pp. 96-100

history

  • JJ Coulton: Lifting in Early Greek Architecture. In: The Journal of Hellenic Studies , Vol. 94 (1974), pp. 1-19
  • Hans-Liudger Dienel / Wolfgang Meighörner: The pedal crane. Publication by the Deutsches Museum ( history of technology series), 2nd edition, Munich 1997
  • Lynne Lancaster: Building Trajan's Column. In: American Journal of Archeology , Vol. 103, No. 3 (July 1999), pp. 419-439
  • Michael Matheus: Medieval harbor cranes. In: Uta Lindgren (Ed.): European technology in the Middle Ages. 800-1400, Berlin 2001 (4th edition), pp. 345-348 ISBN 3-7861-1748-9
  • Andrea Matthies: Medieval Treadwheels. Artists' Views of Building Construction. In: Technology and Culture , Vol. 33, No. 3 (July 1992), pp. 510-547
  • Karl-Eugen Kurrer : History of Structural Analysis. In Search of Balance , Ernst and Son, Berlin 2016, pp. 556–577, ISBN 978-3-433-03134-6 .

Footnotes

  1. ↑ http://wien.orf.at/news/stories/2631057/ “Seestadt”: Cranes dance ballet, with video, ORF.at, from February 15, 2014, accessed on February 16, 2014
  2. ↑ http://wien.orf.at/news/stories/2630065/ "Kranensee" in the Seestadt Aspern, ORF.at, from February 9, 2014, accessed on February 16, 2014
  3. ↑ http://www.vertikal.net/de/news/artikel/20111/ Gigantisches Kranballett, vertical.net May 13, 2014. Accessed May 13, 2015.
  4. ↑ http://view.stern.de/de/rubriken/streetlife/berlin-baustelle-kran-s-bahn-wasserturm-s-bahnhof-ostkreuz-original-1960835.html crane ballet with water tower (picture title), view photo community, Stern.de, February 14, 2011. Retrieved May 13, 2015.
  5. ↑ Johann Christoph Adelung : Grammatical-critical dictionary of the High German dialect . 2nd Edition. Johann Gottlob Immanuel Breitkopf und Compagnie , Leipzig 1793 ( zeno.org [accessed on October 9, 2019] lexicon entry "Kranich").
  6. ^ A b J. J. Coulton: Lifting in Early Greek Architecture. In: The Journal of Hellenic Studies , Vol. 94 (1974), p. 7.
  7. ^ A b J. J. Coulton: Lifting in Early Greek Architecture. In: The Journal of Hellenic Studies , Vol. 94 (1974), pp. 14-15.
  8. ^ A b J. J. Coulton: Lifting in Early Greek Architecture. In: The Journal of Hellenic Studies , Vol. 94 (1974), p. 16.
  9. ↑ All data from: Hans-Liudger Dienel, Wolfgang Meighörner: Der Tretradkran. Publication by the Deutsches Museum (history of technology series), 2nd edition, Munich 1997, p. 13.
  10. ^ Lynne Lancaster: Building Trajan's Column. In: American Journal of Archeology , Vol. 103, 1999, p. 426.
  11. ^ Lynne Lancaster: Building Trajan's Column. In: American Journal of Archeology , Vol. 103, 1999, pp. 427ff.
  12. ^ Lynne Lancaster: Building Trajan's Column. In: American Journal of Archeology , Vol. 103, 1999, pp. 434ff.
  13. ^ Lynne Lancaster: Building Trajan's Column. In: American Journal of Archeology , Vol. 103, 1999, p. 436.
  14. ↑ Andrea Matthies: Medieval Treadwheels. Artists' Views of Building Construction. In: Technology and Culture , Vol. 33, 1992, p. 514.
  15. ^ A b Andrea Matthies: Medieval Treadwheels. Artists' Views of Building Construction. In: Technology and Culture , Vol. 33, 1992, p. 515.
  16. ↑ Andrea Matthies: Medieval Treadwheels. Artists' Views of Building Construction. In: Technology and Culture , Vol. 33, 1992, p. 526.
  17. ↑ a b c d e Michael Matheus: Medieval harbor cranes. In: Uta Lindgren (Ed.): European technology in the Middle Ages. 800-1400 , Berlin 2001 (4th edition), ISBN 3-7861-1748-9 , p. 345.
  18. ^ A b Andrea Matthies: Medieval Treadwheels. Artists' Views of Building Construction. In: Technology and Culture , Vol. 33, 1992, p. 524.
  19. ↑ Andrea Matthies: Medieval Treadwheels. Artists' Views of Building Construction. In: Technology and Culture , Vol. 33, 1992, p. 545.
  20. ↑ Andrea Matthies: Medieval Treadwheels. Artists' Views of Building Construction. In: Technology and Culture , Vol. 33, 1992, p. 518.
  21. ↑ Andrea Matthies: Medieval Treadwheels. Artists' Views of Building Construction. In: Technology and Culture, Vol. 33, 1992, pp. 525-526.
  22. ↑ Andrea Matthies: Medieval Treadwheels. Artists' Views of Building Construction. In: Technology and Culture , Vol. 33, 1992, p. 536.
  23. ↑ a b c Andrea Matthies: Medieval Treadwheels. Artists' Views of Building Construction. In: Technology and Culture , Vol. 33, 1992, p. 533.
  24. ↑ Andrea Matthies: Medieval Treadwheels. Artists' Views of Building Construction. In: Technology and Culture , Vol. 33, 1992, pp. 532ff.
  25. ↑ Andrea Matthies: Medieval Treadwheels. Artists' Views of Building Construction. In: Technology and Culture , Vol. 33, 1992, p. 535.
  26. ^ A b J. J. Coulton: Lifting in Early Greek Architecture. In: The Journal of Hellenic Studies , Vol. 94, 1974, p. 6.
  27. ^ A b Hans-Liudger Dienel / Wolfgang Meighörner: The Tretradkran. Publication by the Deutsches Museum (history of technology series), 2nd edition, Munich 1997, p. 17
  28. ↑ Andrea Matthies: Medieval Treadwheels. Artists' Views of Building Construction. In: Technology and Culture , Vol. 33, 1992, p. 534.
  29. ↑ Andrea Matthies: Medieval Treadwheels. Artists' Views of Building Construction. In: Technology and Culture , Vol. 33, 1992, p. 531.
  30. ↑ Andrea Matthies: Medieval Treadwheels. Artists' Views of Building Construction. In: Technology and Culture , Vol. 33, 1992, p. 540.
  31. ↑ a b Michael Matheus: Medieval harbor cranes. In: Uta Lindgren (Ed.): European technology in the Middle Ages. 800-1400, Berlin 2001 (4th edition), p. 346, ISBN 3-7861-1748-9
  32. ↑ Michael Matheus: Medieval harbor cranes. In: Uta Lindgren (Ed.): European technology in the Middle Ages. 800-1400, Berlin 2001 (4th edition), p. 347, ISBN 3-7861-1748-9
  33. ↑ These are located in Bergen, Stockholm, Karlskrona (Sweden), Copenhagen (Denmark), Harwich (England), Lüneburg, Stade, Otterndorf, Marktbreit, Würzburg, Danzig, Östrich, Bingen, Andernach and Trier (Germany). Cf. Michael Matheus: Medieval harbor cranes. In: Uta Lindgren (Ed.): European technology in the Middle Ages. 800-1400, Berlin 2001 (4th edition), p. 346, ISBN 3-7861-1748-9
  34. ↑ Regulations in Germany BGV D6 ( Memento of February 13, 2012 in the Internet Archive ), accessed on October 3, 2015
  35. ↑ Ordinance on the use of cranes in Switzerland , accessed on October 3, 2015
  36. ↑ Sample operating instructions for the crane , accessed on October 3, 2015
  37. ↑ Modular and flexible rope hoist , Industriemagazin.at. October 7, 2015.
  38. ↑ KBM - AG Kran- und Baumaschinenmuseum eV , accessed on January 13, 2018

Web links

Commons : crane  - collection of images
Wiktionary: Kran  - explanations of meanings, word origins, synonyms, translations