TAMING THE NATURAL FORCES AND THE DEVELOPMENT OF WATERMILL

The simplest and the oldest of these structures was the undercurrent waterwheel, which, in its primitive form was placed directly into the currents and used in the Roman watermills. This type of waterwheel could be easily used in gently sloping rivers, allowing the current to turn the waterwheel in the direction opposite to the current.

If the slope of the water current was greater, it was guided by a special gutter above the waterwheel and the downward flowing water turned the waterwheel with its pressure and weight in the direction of the current. These overcurrent waterwheels have a sloped, cup-type blade construction.

The third type is the mid-current waterwheel, where the water is fed by a gutter to the middle section of the wheel. In order to increase the water pressure by the weight of the water, this wheel had cup-type blades with higher sides. This, similarly as the undercurrent waterwheel, was generally turning in the direction opposite to the current.

All three types of waterwheel with different ways of feeding water and structural improvements were used to power watermills until the turn of the 19th and 20th centuries (sometimes even longer), when the rapid modernization of mill machinery started and the waterwheels were replaced by Francis water turbines.

J.Francis water turbine, patented in 1848. A modern version of this turbine is still used today. Francis water turbine is called also the reactive hydroturbine. It is powered by constant water pressure which is achieved by placing a turbine into a wood or concrete shaft in which specific water level is maintains. Turbines are manufactured with a horizontal or vertical axel, which, similarly to the waterwheel, is connected to a water feeding system. Nowadays water turbines are mostly used in hydro power stations many of which are in old watermills.

Since the beginning of the 20th century, turbines have been produced also in Latvia – in several engineering companies. Most well known are “Ferdinand Meyer & Co”, later “G.Valdispuhl”, as well as “Pirwitz & Co” machinery production plant.