The peak of the scientific improvement in water wheels design is probably the introduction, in the middle of the nineteenth century, of the Sagebien and Zuppinger water wheels. In all civilizations of the past, water wheels (noria) were also used to elevate water. Water wheels were employed mainly for grain milling, but also for running forge hammers, bellows, mortars, fullers, and saws. In the Middle Ages, decreasing the availability of workforce, water mills spread considerably, so that in the nineteenth century there were more than 60,000 wheels in France, 30,000 in England and 33,500 in Germany. In fact, all the oldest mills found in archaeological excavations, Venafro, Barbegal, Tournus, Rome and Athens, were fed by an aqueduct. Initially, in the Roman Era, the spread of the mills has been very slow, both due to the availability of cheap labor, and to the difficulty in regulating the regime of the rivers of the Mediterranean area, characterized by strong seasonal fluctuations in flow. In some cases, it was also used for running hammers of blacksmith’s workshops and hemp mills, devoted to roll the hemp fibers in order to break down their natural coating and make it pliable enough for spinning and weaving ( Figure 1). The horizontal water wheel was normally used as the prime mover of small grain mills, suitable for a modest production of flour of the order of a few quintals a day, typical of highland family farming. The conversion into mechanical energy occurs with low efficiency. The mean rotational velocity is about 15–20 rpm. The horizontal water wheel is appropriate for the low flow rate and high water velocity, typical of mountain rivers. It presents a very simple mechanical architecture: The horizontal wheel is directly coupled to the load through a vertical shaft, supported by an axial bearing cooled by the water flow. This kind of mill has spread both to the east and to the west, and in the fourth century is present throughout Europe. The first traces are narrated by Strabo that, in 65 B.C., tells us about a mill built by Mithridates, the king of Pontus, near his palace in Cabeira. The Greek mill originated probably in the mountainous areas of the Near East. There are two main types of mills: The Greek or Norse and the Vitruvian. In fact, by knowing only the specifics of the ancient mills, it is possible to enhance their potential and restore them from the perspective of a renewed high quality production, or reconvert them in mini-plants for the production of electricity. In the paper, analyzing some typical examples of the old water mill of the Piemonte region, in North-West of Italy, the mechanical architecture of old water mill, from water wheels to millstones, is described and the functional details of various mechanisms are provided. Even when, for economic reasons, their recovery for the original tasks is not suitable, the conversion into mini plants for the production of electricity can be advantageous. Recently, there is a renewed interest in their reuse, both for their widespread diffusion in the territory and for the excellent environmental integration and intrinsic sustainability. It is an enormous historical and cultural heritage of inestimable value, which is for the most part, abandoned today. In the nineteenth century there were hundreds of thousands of mills in all of Europe. Since ancient times and for hundreds of years, grain mills, hammers, sawmills, spinning mills, and hemp rollers have been powered by water wheels.
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