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Technical descriptions of English windmills




Great Sark

Tower mill, standing today

Sark tower mill, a little gem, is unique in being the only windmill within the Channel Islands and, if the latter are counted as part of the United Kingdom, a quite large area of that country including Devon, Cornwall and Dorset, in anything like a complete state. It has therefore a particular claim to preservation. It is an interesting example of an early-type tower mill, small and cylindrical in form and typical in that respect of the Brittany/southwest England region, which has been modernised. It was built in 1571 and refitted in 1830 with largely iron machinery plus patent sails and an eight-bladed fantail. Each sail was of equal width on both sides of the pitch pine stock and had 40 wood-framed canvas shutters, making 160 in all. Going by the metric system, each shutter was 84cm long and 28cm wide, the total sail area being about 48 square metres. The sails were c.7m long each. The weight of the iron windshaft, together with the rest of the upper machinery, was approximately 6 tonnes. The sails passed close enough to the ground for the miller to start them easily by hand once the brake was removed. According to an information board in the mill, striking was by attaching the weights to a chain hanging from the fantail “cogs” and connecting to the striking rod. Since a fantail does not have “cogs” as such I am unclear as to what arrangement exactly is being described but if the information is correct it was something exceptional.(1) The fan was a lofty affair which in the words of R Thurston Hopkins (speaking of the fantails of Suffolk post mills, on their tall carriages) reminded one of a “cocky-olly bird” (cockatoo). It had a safety rail positioned parallel to the diagonal timbers of the fan cradle, which were cantilevered backwards, in the Lincolnshire style, suggesting along with other things the involvement of a millwright of that county in the refitting or subsequent modifications.

 The cap was an ogee with a weathervane mounted on the finial and a dormer extension at the front where the windshaft passed through it. It was removed by the German occupying forces during the Second World War along with most of the upper machinery, and the latter now lies in a heap on the ground beside the mill. The present roof, constructed over the existing cap frame, is a replica, lower and flatter than the original but retaining the weathervane. A surviving shutter was purloined by an English holidaymaker in 1964 and later, perhaps in a fit of conscience, posted to Sybil Hathaway, the then Dame of Sark, with the intention that it should go to the local museum. It is now preserved in the mill.(2)

 The mill is maintained in good condition although not officially open to the public. In recent years much work has been carried out to it including the laying of new floorboards and joists over the original beams and stone bearers, and the installation of new ladders (whether always in the same position as the old is not clear). There are at present no plans to restore the mill to working order. 

The upper machinery is becoming overgrown where it lies, and not all the details can be made out clearly, but the principal items are as follows:

(1) The windshaft. The sails are mounted on a cross after the Lincolnshire/Yorkshire/East Midlands fashion, with bolts and a pair of lugs, on each arm holding the stocks in place. Some of the lugs have become detached. The cross is ribbed on the rear faces of the arms.

(2) The wallower, a six-armed all-iron bevelled affair of light construction. It was located on the upright shaft by means of a short tube fitting over the top few inches of same.

(3) The fan hub, a solid iron drum with mortices for the spars, the rotted stump of one of the latter being still evident, and spindle with bevel nut. 

(4) Part of the fantail gearing, a long square iron shaft with a small iron gear at one end and a larger, bevelled one on the other. The bevel gear is difficult to examine closely because of overgrowth but is presumably the four-armed wheel shown beneath and on the right side of the fanstage in photographs of the mill in working order. 

(5) A segment of a bevelled iron mortice gearwheel, probably the brakewheel. What happened to the rest of it is unknown but it may at some point have been taken away and broken up for scrap.

(6) A twisted iron band the purpose of which I couldn’t identify.

The fate of the spider and striking gear, whether they are still on site somewhere or have been disposed of, is not clear.

Built of stone like all the Channel Island mills, and whitewashed inside, the tower is of small, narrow dimensions with three storeys: dust/bin floor, stone floor and ground/spout floor. The doors and windows are located within deep embrasures. Earth is thrown up to form a mound, with a retaining wall of stone, around the tower for the first few feet of its height, making it easier to attend to the sails. On the north and south sides this mound is interrupted by a sunken stone-lined passage which ends in a short flight of steps to an entrance door.


As noted above the original timbers of the cap frame remain; it is of fairly solid construction and in exceptionally good condition. It consists of the sheers, weather beam (apparently missing), a second lateral timber fore of the brakewheel, sprattle beam and the tail beam, the latter with the tail bearing of the windshaft still in position. What appears to be the neck bearing is preserved on the ground floor. There are additional timbers such as those on which the bearings for the fantail gearing are mounted. The space between the sprattle beam and the second lateral beam, in which the brakewheel turned, is much greater than is normally the case on the mainland UK. The sheers are scarfed into a segmented wooden cap circle, original but not in as good a condition. I could not see whether this turned on skid plates or rollers. There are five solid iron centering wheels, two at the rear, one at each side and one at the front. These bear on the side face of the lower layer of an iron curb. Meshing with the iron mortice rack is the lower of two all-iron toothed gears on a vertical spindle; this is the final stage of the fantail gearing. The centering wheels are mounted in iron castings on the undersides of wooden shoes which are very large, so that the rear ones are in close proximity to the side ones. These shoes are morticed into the cap circle, as are the two timbers which between them flank the forward shoe and connect the cap circle to the second lateral beam to give the assembly extra rigidity and stability. At a guess the weather beam rested on the cap circle but it is hard to be sure. The forward centering wheel shoe projects from the second lateral beam and the rear shoes from the tailbeam, while the side ones are mounted on the underside of the sprattle beam.

 Above the cap frame and to the rear of the tailbeam is the surviving section of what appears to be a previous curb; it is in two layers, the lower deeper then the upper and containing a number of empty mortices, and the whole resting on a short timber-framed section. Within an aperture in the lower layer is part of a casting which would have served as a bearing for a shaft that presumably had something to do with the fantail gear.


There are three windows, a large one on the west side and two small ones on the east and northeast.  The stairwell is on the northwest. A ladder has been fixed leading into the cap.

 The cylindrical upright shaft is of iron throughout its length. It has ornamental “moulding” just above the floor. It tapers at the top towards a final short vertical section which received the tubular projection from the hub of the wallower. The bearing, which remains in place, was beneath the wallower which was not the usual practice on the British mainland.

 Within an aperture in the wall on the northeast side, a foot or so above the floor, is a bearing for a layshaft, but what this drove and where it was itself driven from (it is too low to have been off the wallower) is unclear. Another long, square iron shaft, with a single all-iron pinion, lies displaced on the floor, but this is probably from the fantail gearing. Most likely one of the long shafts took the drive from the nut on the fan spindle down via the bevel gears to the second, which was positioned horizontally within the cap, the larger gearwheel at its other end meshing with the upper of the two final gears.

There is no trace of a sack hoist or any indication where one could have been driven from.


This floor is lit by two large windows on the north and southwest sides. The stairwell and ladder are on the west/southwest. There are no supporting brackets where the main ceiling beams enter the wall. A lateral timber between them carries a steady bearing for the upright shaft on its southern face, just below the ceiling.

 Since the mill served a very small population there was never need for more than one pair of stones. The Peak runner appears to have been broken up, and the fragments later marked with Roman numerals, perhaps to aid eventual reassembly; some rest on the (French burr) bedstone, along with three balance weights by good old Clarke and Dunham, others are on the ground floor along with the binding hoop. The new flooring has been laid with a raised area abutting the stone on the southern side. The vat, horse, shoe etc. are missing. The stone spindle terminates in a curious iron ring which is oval in shape. 


There are no windows. As noted previously the two doors are on the north and south sides. On the southwest side is a short flight of stone steps leading to the ladder giving access to the stone floor.

 The main stone floor beams and the longitudinal timbers of the upright shaft support frame are connected at the south end by vertical members so that the whole forms a single integrated assembly. All the timbers are very massive, but those of the H-frame have been reinforced in metal, as well as varnished by way of an additional preservative. As on the ground floor there are no supporting brackets at the walls.

 A four-armed iron mortice great spur wheel of small diameter meshes with a large all-iron stone nut on the southern side. This nut has a jack ring and three-prong handle for manual adjustment. From the east end of the bridgetree a vertical rod goes up to a link on the connecting post to the ceiling beam above; a steelyard runs from there to rest in a slot in additional vertical timber fixed between and on the outside faces of the ceiling beam and the longitudinal timber of the upright shaft support frame, north of the bridge beam. Whether this mechanism is complete is unclear but there is no sign of a governor and I suspect it was operated manually by pulling on a rope.

 There is no evidence of any auxiliary machinery and dressing was probably done manually as with the tentering gear, a hand sieve being used. The mill forms in some ways a small museum, with items such as a grain measure being preserved, and pulley blocks retained in their original position to help give the look and feel of a working concern.

On the north side of the mill on each floor a boarded-in aperture is presumably intended to indicate the former positions of the sack traps.

(1) Information board within mill

(2) Ditto

Based on survey carried out by Guy Blythman 9th August 2017. Entry was by kind permission of Mr Axton, the mill custodian.