Town Mill - How the Mill Works

IN THE WATERMILL


HOW THE FLOUR MILL WORKS


THE GENERAL LAYOUT OF THE MILL

The Sack Floor The highest and driest floors of the mill are the Sack Floor and the Grain Loft above. They provide good storage for both the grain awaiting grinding and the bags of finished flours. The Stone Floor The Stone floor contains the millstones that grind the grain, together with the grain hoppers which deliver the grain into the stones. The Meal Floor This floor is at ground level and houses the waterwheel itself, as well as the machinery and gearing to drive the millstones.


			HOW THE MILL WORKS


		THE RIVER The River Lim provides the water to power the Town Mill. When the water reaches Mill Green, about 150 yards upstream of the Town Mill, its flow is controlled by a weir. The weir channels much of the river water into a mill-stream, or leat. Only when the leat is full is the rest of the water allowed to flow over the weir and onward to the sea.


USING THE WATER At the mill, the water from the leat is carried onto the top of the waterwheel through an oak trough called a launder. The amount of water used determines how fast the waterwheel turns. The miller controls the water flow onto the wheel by moving a lever which raises a sluice-gate, or penstock, at the end of the launder. THE WATERWHEEL The Town Mill is fitted with an overshot waterwheel. This wheel arrangement makes use of the weight of water flowing in from the river to fill a series of 'buckets' on the rim of the wheel. The wheel works by gravity. It turns because the water flowing onto it makes one side of the wheel heavier than the other. The buckets are self-emptying as the wheel turns.

The last waterwheel used in the Town Mill was installed in 1888, but was removed in the 1930s after the mill closed down because it had become uneconomic. A replacement Victorian wheel, made in 1878, was found for the renovation. This waterwheel is 13 feet (4 metres) in diameter. It has a new steel wheel-shaft that turns on bronze bearings. At the centre of the waterwheel is a pair of cast iron naves which hold the wheel's oak arms. At their outer ends, the arms carry the wheel rims, or shrouds, which hold the 40 wooden buckets. Each shroud is made of 8 cast iron sections bolted together. These, together with the naves, were cast by H Beare of Newton Abbot in Devon in 1878. Traditionally, the wooden buckets would have been made of elm but, because of Dutch elm disease, these new ones are made of Douglas fir.

			THE MEAL FLOOR

			The rotational power from the waterwheel is transferred directly along the wheelshaft to drive the great iron pit-wheel, specially cast for the Town Mill in the year 2000 at Wadebridge in Cornwall. Painted dark red, the pit-wheel weighs 3/4 ton and cost £6,543. It was the single most expensive item in the restoration of the milling machinery. Because it is so heavy, simply moving it into position in the mill was a major operation taking several days. The pit-wheel and its gearing is used to turn the power from the waterwheel through 90 degrees by means of the wallower on the vertical shaft. The pitwheel and wallower thus turn the huge vertical timber shaft, which transfers power to all the other mill machinery. This vertical shaft is by far the biggest upright mill shaft in the whole of Dorset.

Directly above the wallower, the much larger diameter spurwheel drives two newly cast small gear wheels, or stone-nuts, whose pinions turn the millstones on the Stone Floor above. Other iron gears and levers, the tentering gear, on this floor control the gap between the sets of millstones. The gap affects how finely the grain is ground.




THE STONE FLOOR A set of millstones consists of a carefully balanced top stone, the runner, which turns at up to 100 revolutions per minute over a fixed bottom stone, the bedstone.

			Each set of millstones is covered with a round wooden case, or tun, to stop the flour flying everywhere. To start the milling process, the miller pours grain into the square box, or hopper, above the millstones. Grain from the hopper is fed along a wooden trough, or shoe, to the centre of the runnerstone. Poking up from the middle of the millstone is a 3-cornered metal rod or damsel. The damsel is designed to vibrate the shoe when the millstone is turning so that a constant trickle of grain is fed into the centre, or eye, of the stone.

The surfaces of the millstones are cut, or dressed, in such a way that the grains of wheat fed into the central eye are split by the spinning stone and ground into flour or, to give it its correct name, unrefined meal.

				The meal emerges from the grinding process randomly at the outer circumference of the millstones, but inside the side-walls of the tun. Inside the tun, the meal flows into the top of a chute, or meal-spout, and drops down this to the Meal Floor below to be bagged.




THE SACK FLOOR Just below the Sack Floor, at the top of the wooden vertical shaft is a large wooden gear wheel - the crownwheel. The crownwheel turns a lay shaft and pulley wheel, which drive a belt to power a sack hoist on the Sack Floor.


		Using the sack hoist, the miller harnesses the power of the waterwheel to move his freshly ground flour between the four floors of the mill, through the sack flaps cut into the boards of each floor of the mill. The stone-ground wholemeal flour is stored on the sack floor ready for sale or delivery to bakeries.






	The Town Mill Mill Lane, Lyme Regis, Dorset DT7 3PU, England Tel: 01297 443579 e-mail info@townmill.org.uk