Features - The Horizontal Waterwheel

The remains of grain mills powered by horizontal water wheels can be seen on Orkney, Shetland and at a few other places in the highlands and islands. These are very simple structures and generally regarded as inefficient and primitive when compared with mills driven by vertical wheels. Horizontal mills are characterised by a horizontal waterwheel and vertical axle, which passes through the lower mill stone to turn the shaft and upper millstone. There is no gearing. The water supply is conducted to one side of the wheel through a channel and the wheel turned by impact. Thus the mill is suited to a small, but fast flow of water. In this there are similarities with the impulse turbine but there is no evidence that the latter is a direct development of the simple wheel. Water is taken from an adjacent river; small reservoirs are sometimes used to conserve water.

Such mills are not confined to Scotland and some of those developed elsewhere show a degree of development not seen in the Scottish examples. Mills driven by horizontal wheels have been found in Greece, Norway, North America, Ireland, France, Romania, Persia and China. During excavations of the Saxon strata of the town of Tamworth in Staffordshire a watermill with two horizontal waterwheels was found(1) and archaeological evidence from Ireland suggests dates prior to 1200-1300 AD, possibly as far back as the 3rd cent. AD for their use.

Possibly the first written reference to such a mill is in a Greek epigram written in the first century BC by Antipater (2) and horizontal and vertical mills were in widespread throughout Greece up to the Second World War. In 2003 my wife and I spent some time in Greece and visited the Waterpower Museum just outside Dimitsana in the Peloponnese. This was one of the areas where the Greek war of independence from Turkey started: it was well away from the main centres of population and Dimitsana had a long tradition of manufacturing of black powder as a cottage industry. Numerous small gunpowder mills were erected and the remains of these can still be seen. The stamps used to incorporate the powder were driven by a camshaft connected directly to a simple overshot, vertical waterwheel. With this heritage Dimitsana was a suitable site for a water power museum. The museum has a range of vertical water wheels and mills mainly associated with the manufacture of gunpowder and tanning together with an example of a Greek grain mill driven by a horizontal wheel. While the general arrangement of this mill is very similar to those found in Orkney and Shetland, there are distinct differences in the construction of the wheel. Greek examples use a large number of curved or angled blades, initially made of wood and more recently of metal. Wheels recorded in Shetland have a small number of flat, wooden blades set at a small angle to the vertical.

Similar differences occur in wheels from other countries. Those excavated in Ireland have scooped blades, approximately 20 in number, and in this are similar to Iberian, Greek and Persian wheels. Norwegian and Faroese waterwheels are similar to those found in Scotland and have fewer, flat blades. The example from Huxter in Shetland, which is illustrated in Hay and Stell(3), has nine flat boards set at a small angle to the vertical. Faroese mills had eight flat boards, either set at an angle or vertical. Williamson(4) concluded that such wheels were a recent introduction to the Faeroe isles and that the design came from Norway. There is a suggestion that Shetland Mills had curved blades in earlier times and that flat blades were substituted as they became freely available from Norwegian saw mills. If so, they were probably similar to the Norwegian example illustrated in Goudie(5), which shows a wheel comprising eight slightly curved blades set at a small angle to the vertical. Curwen (2) in his review of the development of the horizontal wheel suggested that the design originated somewhere between China and Southern Europe and from there was taken to Ireland and then Norway. This has been disputed but the dates, first century BC for Greece, the seventh century AD for Ireland and later for Scandinavia, suggest that it is quite plausible. Curwen also notes that whereas northern wheels rotate in a clockwise direction, those from the south rotate anti-clockwise.

Hunter(6) points out that the horizontal water wheel played an important role in America and was until recent years in use in parts of Southern Appalachia. The North American "tub-wheel" reflects Scandinavian practice in that it has flat wooden blades but differs in one important detail. The wheel with its blades is contained within a circular wooden container, the tub, which constrains the inward flow of water. Tub wheels were made larger than those recorded in Shetland. A description from Maine gives 4.5 feet for the wheel diameter and a table reproduced from Evans(7) (The Miller's Guide) gives data for wheels up to 7 feet in diameter; compared with some 3 feet for the Shetland mill. The tub wheel was also used to power the up-and-down sawmill; this necessitated the use of gearing. Power take off by pulley was also used. The largest installation of horizontal wheels recorded by Hunter was at the Springfield Armoury of the Federal Ordnance Department. A total of 27 water wheels were employed, 13 being tub wheels.

Hunter also mentions tests made by French engineers on similar wheels, reported by d'Aubuisson(8), used extensively in the south of France. D'Aubuisson de Voisins published his Treatise on Hydraulics in the first half of the 19th century. The English translation appeared in 1858. He notes that while vertical water wheels were generally used in the north of Europe, horizontal wheels were common in the south; "they operate nearly all the mills in the southern departments of France". He distinguished two types of horizontal wheel. First those in which the water impinged on the wheel as a jet, as in the Greek or Norse wheels, and those in which the wheel, placed at the bottom of a tub, open beneath, was rotated by the whirl of water cast upon them. He noted that those operated by a single jet were very common in mountainous regions in the Alps and Pyrenees. The example described in his book has a diameter of 1.6m and is 0.2m in height. The curved floats have a length of 0.4m and number 18. It is stated that the water jet is cast on the blades with a velocity of 7m to 8m per sec. and acts almost wholly by impulse. He notes that, from experiments using such wheels, the head of water was typically 4.11m and the flow some 0.3 cu. m per sec This produced a force of some 33 newton at 1.1m radius and a rotational speed of 100 r.p.m.

He notes that on Rivers, e.g. the Garonne, Aude, etc where there is much water and little fall, tub-mills are used. ("Moulins a cuve"). Here the wheel is placed at the bottom of a masonry well or cylinder, open at both ends. The wheel, 1m by 0.2m carries 9 curved, wooden floats. The well is 1.1m in diameter and 2m deep.

The wheel is placed at the bottom of the well and the cylinder pierced by a vertical slot, which extends from the wheel almost the whole height. This serves as the water lead; it narrows down towards the cylindrical well,

so that at the point the water issues from the lead the slot is only 0.22m wide. One of its sides is tangential to the side of the well. The water whirls down turning the wheel as it passes through. Because of centrifugal force, some effect is inevitably lost as water passes through the narrow gap between the wheel and wall. According to d'Aubuisson, such mills had been described in Belidor's "Architecture Hydraulique". For a typical wheel, with a head of 2.4m and a flow of 0.86 cu. m per sec. the force at the end of a 1.2m was 299 newton The rotational speed was 81 r.p.m.

Such a mill is preserved at Cougnaguet on the river Ouysse, a tributary of the Dordogne. It has 4 horizontal wheels with deeply curved wooden cups set in carefully built circular stone chambers. The drive is direct to the top mill-stone and in this and other respects they are very similar to the simple wheels above, but much more effective. The wheel, from memory, is some 1 to 1.5m in diameter, and it is stated that the mill could produce some 4 tonnes of flour per day. The wheels rotated at 80 r.p.m.

d'Aubuisson was quite clear that the turbine developed by Fourneyron was based on such a mill.

Ted Salthouse

References:

1. Watt, M, The Archaeology of Mills and Milling, 2002
2. Curwen, E C, "The Problem of Early Water-mills", Vol. XVIII, Part 69 , pp. 130-146
3. Hay, G D & Stell, G P, Monuments of Industry 1986, pp 9
4. Williamson, K, "Horizontal Water-mills of the Faeroe Islands", Antiquity, Vol. XX, 1946, pp. 83-91
5. Goudie, G, "On the Horizontal Water-mills of Shetland", Proceedings of the Society of Antiquaries of Scotland, Vol. XX, 1886 pp. 257-297
6. Hunter, L C, A History of Industrial Power in the United States, vol 1,"Waterpower", p 71 etc.
7. Oliver Evans, The Young Mill-Wright and Miller's Guide, 13th Ed., 1850, Reprint 1972
8. d'Aubuisson de Voisins, J E, A treatise on Hydraulics for the use of Engineers, 1858 (English Edition)
9. Nomikos, S, "Water power in Preindustrial Greece", 1997.

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