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Description

Reasons for Designation A tower mill is a type of windmill in use during the late medieval and post- medieval periods, which owes its name to the housing of the milling gear in a tapering tower of brick, stone or wood. The sails are fixed to a rotating timber-framed cap. On early tower mills the cap was rotated manually to move the sails in and out of the wind, while on later examples, which were generally taller and carried a greater number of sails, it was moved automatically by means of a fantail. Towers built of stone or brick were usually circular in plan and their sides were protected from the weather by paint, tar or tiles; timber-framed towers, known as smock mills, were built onto a brick base and were normally octagonal in plan and protected by weather-boarding. Used primarily for grinding grain, tower mills had a wide distribution but were most common in the grain growing areas of south and east England where there was insufficient water power to run an adequate number of watermills. In some areas tower mills were also used to pump water or to saw wood. There were about 10,000 tower mills in England at the peak of their construction in the mid-18th century; they declined in use in the late 19th century due to increased use of steam power, although some continued to function into the 20th century. Formerly a common feature of the English landscape, less than 400 tower mills are known to survive, principally of the mid-18th to mid-19th century. Tower mills preserve valuable evidence for the development of milling technology and the economy from the late medieval period to the 20th century, and many have acquired an important amenity and educational value. All examples surviving in good condition, particularly those which contain their machinery intact, demonstrate unusual characteristics or significant associations, are considered to be of national importance. Sibsey Trader Windmill is a rare example of a complete tower mill which has been restored to working order. As a multi-sailed windmill with an ogee-shaped cap it is characteristic of a particular region, and is one of very few six-sailed windmills still surviving. Built in 1877 it is an unusually late example of this type of monument in a part of the country where windpower continued to be exploited for a longer period than in more industrialised areas; it is therefore representative of its local historic and economic environment. With the buried remains of an earlier post mill and the site of the later engine house, the monument preserves evidence for the evolution of milling on the site which will tell us how this activity originated here and developed into its present form. As a monument in the guardianship of the Secretary of State, Sibsey Trader Windmill serves as an important educational and recreational resource. Details The monument includes Sibsey Trader Windmill, a six-sailed tower mill built in 1877 by Saunderson & Son of Louth. Originally there were four pairs of millstones; in the early 20th century a further pair was installed, run by an engine housed in an exterior engine-shed. The mill was in regular use until 1953, after which date the engine was removed and the mill fell into disrepair. In 1975 the mill passed into the care of the Secretary of State and was subsequently restored to working order. The monument includes the mill, a Grade I Listed building, complete with gear, sails and other fittings; it also includes the base of the engine-shed and buried remains associated with an earlier post mill which the tower mill was built to replace. Sibsey Trader Windmill is located on the edge of the West Fen about 1km west of Sibsey parish church. It takes the form of a tarred brick tower of six storeys tapering upwards to the curb, a circular cast-iron track on which the cap is rotated. At third-storey level is an exterior gallery with ornate wrought-iron railings. The cap is ogee-shaped and is weatherboarded. Fixed to the cap are six wooden double-sided sails of Cubitt's Patent type, the speed of which is regulated by double sets of movable shutters. The shutters are controlled by a series of rods which are connected to the striking gear on the opposite side of the cap; the striking chain and weight are suspended to gallery level where they can be adjusted. Also on the cap is a wooden fantail, the movement of which rotates the cap to turn the sails into the wind. The tower and cap together reach a height of approximately 22.6m. On the interior of the mill are six storeys with whitewashed walls, timber floors and interconnecting ladders. Running through all six storeys is the central upright shaft, turned by the sails, and the sack hoist chain, by which sacks of grain are carried from the ground floor to the upper storeys through a series of trap doors. The ground floor is reached by a short flight of brick and stone-flagged steps. It is now occupied by a wooden elevator dating from the first half of the 20th century when a pair of engine-driven millstones were installed here, since removed. Also on the ground floor is part of a sail, recently fitted for display purposes. Originally the ground floor was an open area used for bagging flour fed down wooden chutes from the millstones above, and for fixing sacks of grain to the sack-hoist to be carried to the grain bins in the upper part of the tower. Beneath the ground floor is a low basement, reached by a trap door, which was used for the storage of empty sacks. Above the ground floor is the meal floor. On this storey are the governor and tentering gear, which control the gap between the millstones on the floor above, and the tensioners which control the flow of grain onto the millstones. Also on the meal floor is a millstone, recently fixed for display purposes. Above is the stone floor where the millstones are located. Three of the original four pairs of millstones survive, fitted in the original wooden vats. One pair of stones is still in use and the vat is now lined with aluminium. Above the vats are wooden hoppers from which the grain is fed onto the millstones. Each of the upper `runner' stones is fixed to a quant, a vertical shaft which terminates in a small horizontal iron wheel known as the stone nut. In turn, the stone nuts are engaged to the great spur wheel, a large horizontal iron wheel beneath the ceiling, which is turned by the upright shaft. On the stone floor are two opposing wooden doors giving access to the gallery. Above the stone floor are two bin floors where the grain bins were located; part of a wooden bin survives on the upper floor. In the floors are small holes, now covered with perspex, through which the sacking spouts ran to the stones below. On the top storey is the dust floor, open to the cap, where an iron wind shaft runs between the sails and a vertical brake wheel and brake; the brake is connected to a horizontal wooden lever by which the brake wheel is released to allow the wind shaft, and thus the sails, to turn. The brake wheel is engaged with a horizontal iron wheel, the wallower, on the upright shaft. Adjacent to the upright shaft is the sack hoist gear, also run by the wallower. Here the curb may be seen resting on top of the brick wall; running down the inside of the wall is a series of iron holding bolts which keep the curb in place. Adjacent to the north west side of the tower is the base of a rectangular building approximately 8.5m long and 3.5m wide. The floor is constructed of concrete. This represents the remains of an engine-shed built to house an auxiliary oil engine in the early 20th century. In the north wall of the tower is a small aperture, now sealed, through which the engine was connected to the pair of millstones which formerly occupied the ground floor. Adjacent to the west of the tower is a raised area of accumulated deposits, over 5m in diameter and about 0.3m high, sloping down slightly to the base of the engine-shed on the north, the track on the south and the fence on the west. The archaeological deposits in this area are considered to represent buried remains associated with the post mill which occupied the site prior to the tower mill. The millstone on the meal floor and part of a sail on the ground floor, which are fitted for display purposes are not included in the scheduling. The two millstones which are now leaning against the exterior of the tower and the parts of the original curb which lie near the east side of the tower, are not included in the scheduling although the ground beneath them is included. Sources Books and journals Brann, M, The Engine Shed, Sibsey Trader Windmill, (1993) Dolman, P, Lincolnshire Windmills: a contemporary survey, (1986), 25 Other Apted, M R, Sibsey Trader Mill, 1986, pamphlet Title: Boston Source Date: 1824 Author: Publisher: Surveyor: 1 inch map

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