A chain boat,National Geographic Society (1937). The National Geographic Magazine, Jan-Jun 1937, pp. xxi and 552.John MacGregor (1867). The voyage alone in the yawl "Rob Roy": from London to Paris, and back etc., London: Maranda merrill, Son and Marston, pp. 97-99. chain tug or chain-shipRoger Pilkington (1969). Small boat to Northern Germany, Macmillan, pp. 90, 91 and 95. was a type of river craft, used in the second half of the 19th century and first half of the 20th century on many European rivers,This system is still used at Riqueval Tunnel of Canal de Saint-Quentin in France. that made use of a steel chain laid along the riverbed for its propulsion.Kettenschifffahrt definition in Schifffahrts-Lexikon, by J. Friedrichson, p. 149. Retrieved 1 Mar 2014.Willi Zimmermann: Über Seil und Kettenschiffahrt, Beiträge zur Rheinkunde 1979, Rheinmuseum Koblenz (digitalized version by Peter Haas ; pdf; 5.9 MB) The chain was engaged using a steam engine mounted on board and enabled the boat to tow a string of barges.MacGregor (1867), p. 97-98 states "The power of this chain-boat is so great that it will pull along, and that too against the rapid stream, a whole string of barges, several of them of 300 tons' burthen, while the long fleet advances steadily though slowly, and the irresistible engine works with smokeless funnels, but with groanings within, telling of tight-strained iron, and loud undertoned breaths of confined steam."Hearst's International, Volume 3 (1902) by International Magazine Company. Retrieved 12 Mar 2014. In Germany, such a boat was variously referred to as a Kettenschleppschiff, Kettenschlepper, Kettendampfer or Kettenschiff and in France as a toueur.Roger Pilkington (1965). Small boat in Southern France, Melbourne, Toronto, p. 33.
The chain was raised out of the water over a boom at the bow of the ship and led over the deck along the ship's axis to the chain engine amidships. The transfer of power from the steam engine to the chain was usually achieved using a drum winch. From there the chain was led over the deck to another boom at the stern and lowered once more into the river. By moving the stern boom and the two rudders, front and aft, from side to side it was possible to replace the chain in the centre of the river again, even when negotiating river bends.
History
Chain boat navigation revolutionised inland shipping during the Industrial Revolution in the second half of the 19th century in Europe and superseded the hitherto commonplace haulage of barges by draught animals or people. The chain drive of these riverboats made optimal use of still relatively low-powered steam engines of that period. In addition, the boats were especially well suited to the difficult condition of river navigation that pertained at that time: many rivers were shallow or fast-flowing and effectively precluded the use of paddle steamers. As a result, chain boats were soon being used on many rivers across Europe. But by the first half of the 20th century they were increasingly threatened by competition from ever more powerful paddle steamers, something that was aided by the canalization of rivers.K. Dietze: Chain and Rope Towage on German Rivers. In: International marine engineering, Volume 16, New York 1911, pp. 433–439
The first designs and early technical stages in the development of chain boats took place in the mid-19th century, especially in France. The prototype of all later chain boats on the rivers Elbe, Neckar and Main was the French steamboat La Ville de Sens, which was built by the German engineer, M. Dietz, around 1850 in Bordeaux, and plied the upper Seine between Paris and Montereau. Its technically very advanced operating principle and its engineering features were adopted by all the later European chain steamers.
Design
The hull of these symmetrically-designed boats was almost level with the surface of the water at the bow and stern. This design reduced the power needed to lift the tow chain onto the bow of the boat and also reduced the draught at the bow.Eduard Weiß: "Die Kettenschlepper der kgl. bayerischen Kettenschleppschiffahrt auf dem oberen Main" in der Zeitschrift des Vereins Deutscher Ingenieure, Vol. 45, 1901, No. 17, pp. 578–584 The greater height of the boat in the centre made it easier to accommodate the steam engine. This deck shape - low at the bow and stern, and higher in the centre - is typical of all subsequently built chain boats.
Chain boats were favoured on shallow rivers with fast currents. This was the reason for the flat, shallow draught of their keels. Chain boats optimized for particularly shallow water had a draught of only when unladen. Even fully laden with coal, their draught was only about .Theodor Grötschel und Helmut Düntzsch: Betriebsmittelverzeichnis der KETTE – Deutsche Elbschiffahrts-Gesellschaft This shallow draught enabled river transportation even in the dry summer months when the water level of rivers could be very low.
Shorter chain boats, with lengths from , and widths from , were more manoeuvrable and well suited to narrow rivers with many bends, for example on the Saale. Longer craft, with lengths from , and widths from , were better suited to relatively deep rivers such as the Elbe. The deeper a waterway was, the greater the power needed to lift the heavy chain. The bow of the ship was pulled down further. On larger boats this effect is reduced.Zeitschrift für Bauwesen Volume 16, Berlin 1864, p. 300, Verein für Eisenbahnkunde zu Berlin, Protokoll vom 10. November 1863 (digitalized version)
The hull itself was made of iron or wood and could withstand light impacts with the riverbed, and was compartmentalized internally by several waterproof bulkheads that prevented the craft from sinking in the event of a hole. Below deck were the steam engine, the coal bunkers and the crew accommodation.
Control and navigation
In chain boat navigation the chain was simply laid "loose" on the riverbed for long distances of up to several hundred kilometres. Only the deadweight of the massive chain, which weighed about or , and its natural snagging on the sand and stones of the riverbed provided resistance, so that the chain boat and its attached barges could haul themselves along the chain. The water bore the weight of the boats and barges, whilst the chain only had to cope with the power of the engine. The chain was only anchored at its two ends so that boats could continue to haul themselves to the end of the chain route.
A problem was caused by sideways displacement of the chain. At bends in the river there was a tendency for the chain, that was laid in a curve, to increasingly pull itself straight and so move towards the inside of the bend. In order to prevent this, chain boats were fitted, fore and aft, with large, powerful rudders. These rudders sometimes had a length of over four metres and were worked with the aid of control wheels on the deck.
At the bow and stern of the boat the chain was led along a boom that projected well beyond the end of the deck. This prevented the chain from hitting the long rudders. The booms were movable and could be swung sideways using a hand crank. The boat could thereby be oriented at an angle to the direction of the chain. This also improved the chances of replacing the chain back in the centre of the river.
The boom was also fitted with chain interception equipment so that, in the event of the chain breaking, it would not be able to run away. If the chain catch was not quick enough to hook into the chain, it would simply run away and disappear into the river. It then had to be painstakingly located with a drag anchor and salvaged.Otto Berninger: "Die Kettenschiffahrt auf dem Main" in the Main Shipping Reports of the Society for the Promotion of the Wörth am Main Shipping and Shipbuilding Museum, News Sheet No. 6, April 1987, 111 pages.
Chain driver In the first generation of chain boats the chain ran over chain drums at the side of the boat. In fast-flowing currents or when there were problems lifting the chain due to silting or obstacles on the riverbed such as large rocks, the boat could swing off-course markedly and list to one side. As a result, on later chain boats, the chain drive was always located on the centerline of the boat.
Drum winch
The older chain boats on the Elbe, the chain steamers on the Neckar and the three craft on the Main belonging to the Hessian Mainkette company used a drum winch to transfer power. In order to ensure the necessary traction on the chain on the driving drums, the chain was wound several times around two traction drums placed one behind the other in the centre of the boat. The chain ran in four to five grooves and was alternately wound over the front and rear drums.Architektenverein zu Berlin: Deutsche Bauzeitung, Volume 2, Verlag Carl Beelitz, 1868, S. 100, (Google Books), (description of the 1st German chain boat between Neustadt and Buckau)
The disadvantage of this method was that the chain frequently broke. This did not simply occur due to the overloading of the chain by the length of the barge train. It has been calculated that even if the chain links wore down to half their original cross-section, this force would not have led to a break. Rather the problem lay in the fact that frictional wear on the forward traction drum was much heavier than on the rear. And once the diameters of the two drums became unequal, more chain wrapped around the after drum than could be handled by the forward one. This could produce tensions both on the drums and between them that were so large that the chain links could not withstand the tensile load and their fracture limit was exceeded. – 2. Auflage 1904–1920
This effect became even more pronounced if the chain became twisted, e.g., the chain was pulled to one side or had even formed knots. This increased the turn radius by up to 25%, whereby the 5% elastic limit of the chain was reached.
The transfer of tractive force from the drums to the chain was only achieved by friction. If frost or ice built up, the chain could slip. In such events, hot water was poured over the drums.
Another problem with drum winches was the relatively large length of chain – – that had to be wound several times around the two drums. If the chain boat was only used to haul barges upstream, it could not simply reduce the amount of chain needed for the drums on the way back otherwise, after a certain time, the surplus chain would pile up at the head of the operating section and there would be no slack at the start. In order to try to avoid this problem, the chain boat always carried the corresponding section of chain with it downstream and dropped it at the start of the chain route.A. Schromm: Kettenschifffahrt und Elektricität. In: Zeitschrift für Elektrotechnik, Jahrgang 13, Vienna, 1895, pp. 264–266, online Internet Archive As a result, there was a continual movement of the chain, that made control more difficult in more dangerous sections of the river, such as rapids. In particular, reinforced chain sections that were deliberately used, moved continually upstream. Also jettisoning the chain temporarily when two chain boats met was relatively difficult due to the multiple windings of the chain round the two drums.Das Ziehen und Fortbewegen der Schiffe auf Canälen, canalisierten Flüssen und freifließenden Strömen, Binnenschiffahrts-Congress im Haag im Jahre 1894, In: Alfred Weber Ritter von Ebenhof: Bau Betrieb und Verwaltung der natürlichen und künstlichen Wasserstrassen auf den internationalen Binnenschifffahrts-Congressen in den Jahren 1885 bis 1894, Verlag des K.K. Ministeriums des Inneren, Vienna, 1895, pp. 312–327