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Technical descriptions of English windmills



Blackborough Mill

Post mill, gone


Farries: The mill was a post mill of orthodox construction. It had four common sails, and the two-floored superstructure, containing many fine oak timbers, and covered with tarred weatherboarding, was turned by a tailpole mounted on a cart wheel. The main post, of oak, was supported by crosstrees resting on brick pillars; the ends of the crosstrees projected through the walls of the roundhouse and were there covered by brick “blisters” or protective shoulders. The cast-iron poll end was mounted on a wooden windshaft to which were attached a brake and a tail wheel, both of wood. There was an iron brake. The quants to the two pairs of stones below the driving wheels were controlled by the same governor. In the rear of the stone floor was a wire dressing machine.

Reigate Heath

Post mill, standing today


Farries: Mounted on the square cast-iron windshaft, which was last turned by four double-shuttered patent sails, is a wooden brake wheel of clasp-arm construction, from which the 104 cogs have been sheared off. The wooden brake remains in position. The wallower, of cast-iron, with 33 teeth, is mounted on an octagonal upright shaft of iron. Above these gears the sack hoist is still attached to the gable, but has no chain. It was rope-driven by a wooden pulley of 3ft 6in effective diameter mounted on the forward side of the brakewheel, and the sack hoist bollard took up the drive when raised by a long wooden lever extending back to a point under the rear of the hoist.

 The two pairs of stones in the breast – peaks on the left and burrs on the right, on 5ft 6in centres – were underdriven. Sections of the octagonal vats around them remain. The great spur wheel is an iron mortice with 80 cogs, and it is interesting to note that it drove cast-iron stone nuts differing by 1in in diameter and having 23 and 25 teeth respectively in the peak and burr stones. The peak stones were therefore made to revolve a little faster, as was customary. To put the nuts out of gear an iron ring contacting their underside was screwed up from below to slide them off a taper. There was formerly a pair of stones in the tail, where the circular housing for the bed stone in the stone bearers may still be seen. The space left by the removal of the tail stones provided an ideal passageway for the sacks up the mill. The change from head and tail stones to a pair in the breast resulted in a much greater freedom of movement for the miller, and allowed the construction of large bins and a walkway between them over the rear of the windshaft. This arrangement resembles the far more generous layout found in the typical watermill, where the problem of bin capacity does not exist. The tendency to upset the balance of the mill was effectively offset in the case of this mill by moving the brakewheel and headstones further back towards the main post; gaping mortices in the top side rails testify to this fact and also to the former provision of a spindle beam for the rear stone nut. The existing assembly of stone nuts and spur wheel forward of the main post is supported by two hangers bolted to the forward face of the crowntree and a beam let into the corner posts 2ft 3in measured on centres below the member carrying the stone bearers. Both brays are pivoted suitably at their inner ends and run out to their respective steelyards at opposite sides of the mill. The left bray lies just to the rear of the added transverse beam, and the right-hand one is situated just forward of the crowntree. The steelyards are therefore of equal length, approximately 9ft, and are both brought at overhead height to the collar of the governor operating to the left rear of the crowntree. This centrifugal ball governor was belt-driven from the upright shaft just below the spur wheel, and regulated both pairs of stones. Most of the new construction was in pine, a choice of timber common to many modifications of this kind, and characteristic of work in the later tower mills. However, old methods could still find favour; both the stone nuts and the spur wheel were centred by means of tapered wedges applied at the sides of flanged iron plates let into the bridge trees and sprattle beam, as at Shiremark. Reference may be made to the accompanying line drawings of that mill for a better understanding of the machinery and the general construction, which may be described as broadly typical of the known Surrey examples.

 The mill body was probably extended at some time to house the wire dresser, which is still in position across the rear of the stone floor. The belt drive for this machine came from a pulley set on a short horizontal shaft carrying a bevel pinion meshing with the brakewheel on the left side of the mill. The belt drove a wooden pulley mounted on a horizontal shaft and thereby turned, through a solid wooden gear of 27in diameter, a 9in iron bevel pinion on the inclined machine shaft above.

 The crowntree is of exceptional size, being 26in square in section; nevertheless it shows a downward curvature, and has been strengthened on its upper surface by two wide-flanged steel joists, which, through further short joists at their extremities, reinforce the side girts. There are single intermediate uprights 8in by 5in deep extending from the bottom side rails up to the side girts, set a little behind the ends of the crowntree, and therefore approximately centrally placed between the main uprights; from these intermediaries, near spout-floor level, diagonals measuring 7in by 5in., the longer dimension flat to frame, spring to the undersides of the girts. Diagonals of the same section also brace the framing above the side girts from girts to corner posts, and in the front frame from corner posts at side-girt level to near the point of entry of the prick or prow post into the weatherbeam. These diagonals give the mill a rigidity which it would otherwise long since have lost in the weakened state of many of the main joints up to the time of the renovations in 1963. The oak studding, 4in square, in the front framing at approximately 2ft intervals, runs horizontally and carries vertical boarding inside the normal weatherboarding from the forward sill up to the weatherbeam, thus giving added protection against the weather. The framing of the mill in general closely resembles that at Lowfield Heath, and Blackborough also had vertical boarding on the front frame; all these mills conformed broadly to Outwood in body construction, where, however, diagonals are conspicuously absent. The four main upright or corner posts supported by the side girts in Reigate Heath mill all show a thickening towards the interior of the mill in their top two feet – the “gunstock head” effect – giving a wide surface for the support and housing of the tail and weather beams. The true corner posts in the extreme rear of the mill are much smaller in section.

 The main post is unusual in having a cross-tailed gudgeon at the top; this fitting has been observed elsewhere in Surrey only at Lowfield Heath. One may hazard a possible explanation for the use of the gudgeon as follows: when these two mills were constructed they probably contained little or no ironwork, and carried lightweight common sails. Later replacements by up-to-date materials may have upset their balance, so that the wooden tops of the posts, and the pintles, would have been reduced by friction, making reinforcement by iron casting imperative.

 In the roundhouse the main post, which exhibits a large crack of considerable age, and is strengthened by an iron band, is steadied by crosstrees which rest on brick piers and show a pronounced sag in the lower member. This may be due partly to the practice of notching deeply both crosstrees at the point of bearing with the butt of the main post, but the gap of 1in between the crosstrees where they cross, no doubt intended, is a reminder that the weight of the mill is supported by the extremities of the crosstrees where the quarterbars are houses. The lower crosstree has been bound with wrought-iron straps on either side of the post to prevent the extension of a long horizontal split along its centre.

Trumpets Hill

Smock mill, gone



The oldest of the four Surrey smocks to survive into the 1940s, the Trumpets Hill mill was the most modernized and the first to stop working, probably unexpectedly, since the brake and spur wheels were newly cogged. It is of special interest as a representative of the C18 Surrey smock mill having the wooden structure built up from ground level. It was among the mills surveyed by Mr Denis Sanders, who contributes the following technical description:

 This octagonal tarred smock mill was built wood to ground, the brick footings standing at field level, and the woodwork rising 30ft to the curb, with four floors, the ground floor being of timber supported by small brick piers. The cant posts were of pine, 9in square, and the wooden curb 12in by 9in deep. Central vertical members 5in square were used in all panels, with diagonals and studs somewhat similar to those at Shiremark. The tower was 23ft across at ground level, and 15ft across at the curb; the overall height of the mill was 40ft.

 The first floor – stone floor – had been completely cleared of all milling equipment, boarded right across, and a circular table fixed round the upright shaft, making a very pleasant garden room, access being gained by an outside stairway and balcony only. Illustrations showing the balcony from some angles can give the mistaken impression that the mill had a stage at first floor level. Electric light was installed and the room was used for some time as a classroom for the owner’s children.

 The pairs of floorbeams ran in alternate directions and were of oak, very massive; those of the bin floor, for example, were 14in deep by 10in, on 5ft centres.

 The cap was of the Kentish pattern, like that on a post mill, with a straight ridge and very stoutly built, with the sheers set wide apart, forming the outside edges, and having the roof spars mortised directly into them. Blisters were needed on the sides of the cap to clear the curb, and in this and other ways there was a resemblance to the smock mill at Outwood. The sheers were 11in wide by 12in deep and the weather beam 13in deep by 2ft at the centre, being straight on the rear face and shaped to the cap profile on the forward side, set in the same plane as the sheers, and double-tenoned into them at each end. The sheers projected through the boarding a little at the front, and were weathered with lead. The spindle beam and tail beam were each 12in deep by 14in, both in the same plane as the sheers and tenoned into them. The width of the cap was 25ft, the length 18ft, and the height over the curb 10ft.

 The eight vanes of the fan were removed many years before the end and stored on the dust floor. They were 3ft 6in deep, 2ft 9in wide, and painted white. The gear train from the fan to the upwards-facing rack on the curb was unusually complicated. A worm on the fan spindle drove a worm wheel on a vertical shaft, which led successively to a pair of bevels, a pair of spurs, a second pair of bevels, then a third pair of bevels, the driven one being on a horizontal shaft carrying an 8in diameter spur pinion meshing with the upward-facing rack. The two heavy timbers of the fanstage were set at a low angle; their inner ends were bolted on top of the spindle beam just inside the sheers.

 The curb was live, with eighteen iron rollers 4in diameter arranged as tandem pairs, each pair carried in an identical iron bracket secured to the underside of the rectangular cap frame; three for the weather beam and two each for the tail beam and sheers. The fact that these four main beams were in the same plane, and that the sheers were set wide apart, allowed this neat and simple scheme. The seven iron truck wheels, employed to keep the cap central, were each of 13in diameter, and were also carried in iron brackets fixed to the cap frame, one at the head, two each side and two at the tail.

 Four double-shuttered spring patent sails – of a similar pattern to those at Outwood smock mill, and almost certainly by the same maker, spanned 68 feet, giving a ground clearance of only two to 3ft. They were 6ft 6in wide, with thirteen bays, the two outer bays having two shutters each, and all the rest three. The stocks were 4oft long, 12in square at centre and 7in square at the tips, strengthened by clamps 7in by 9in and 14ft long. A six-armed Y-wheel, outside at the right rear of the cap, controlled the striking gear, with pinion to rack on the striking rod.

 The iron windshaft was 16ft long overall and 12ft from neck to tail journals, which were of 12in and 5in diameter respectively. Between the two the shaft was octagonal, and 10in across the flats at the brakewheel mounting, where an iron boss with four horns was keyed on, giving an effective 22in square for hanging the wheel.

 The brake wheel was an all-wood clasp arm gear, with two sets of arms 5in square, eight shallow cants 7in thick, and two sets of rim sections, fore and aft of the cants, bringing the overall thickness to 12in. There were 104 wood cogs of 5in face and 3¼ in pitch, the overall diameter being 9ft 6in. The wooden brake, in segments, was very neat and well-finished, 11½ in wide by 5½ in thick.

 The wallower was a single iron casting, 4ft diameter, with eight arms and 45 teeth. The upright shaft extended from the cap down to the ground floor, where it was carried in a bridging box on a wooden sprattle beam 14in by 10in set diagonally between two of four posts which served to support the stone floor above. The shaft was iron, 5in square, in two equal coupled sections, and 25ft long overall, running in a bearing at second floor level, and carried at the top in an inverted bridging box (cf. Shiremark) on the underside of the spindle beam in the cap. The great spur gear was keyed on at the base of the upright shaft in the ceiling of the ground floor; it was an eight-armed iron wheel, 6ft 6in in diameter, with the rim cast separately from the hub and arms, and bolted on. The wooden cogs numbered about 100.

 The stones had been removed; they were underdriven, on the first floor, and there were certainly two and possibly three pairs. The stone nuts and spindles, and the bridge trees, all formerly on the ground floor, had also been removed. The machine-drive gear was mounted on the upright shaft in the ceiling of the first floor; it was an eight-armed iron bevel gear, of 4ft diameter, with upwards-facing wooden cogs, 76 in number. This drove the machines, and probably the sack hoist also, there being no indication of friction gear on the wallower.

Wray Common

Tower mill, standing today


Farries: The brick tower stands about 45 ft high to the curb, and tapers from 20ft to 12ft in diameter; the wall is 1½ feet thick and was formerly whitewashed inside and tarred outside. There were five floors which, in order of descent, were dust 5ft high, bin 7ft, stone 9ft, spout 10ft and ground 11½ feet. The machinery has been removed from the wallower downwards and the floors largely reboarded, probably by Thomas B Hunt, millwright, Soham, whose metal name plate is fixed to a second-floor joist at the hatch. The sprattle beam, which supported the lower end of the vertical shaft, is still in position immediately below the bin floor, a clear indication that the stones were overdrift.

 Two features of particular interest which may still be seen are the elaborately constructed brakewheel and the live curb of the comparatively uncommon “shot” type. The brick tower ends in a flat circular surface 1½ feet wide, and this is overlain by the wooden curb about 8in square in section. Supporting the curb and resting on the brickwork are wooden wedges, 1½ to 2in thick; these permit the easy maintenance of the curb in a true horizontal position. The upper face of the curb carries the iron rack with approximately 110 teeth on its outer section, and its inner section provides a channel within which rotate circumferentially, in a vertical plane, and at fixed positions, about twenty iron rollers 5in in diameter by 3in wide. A keep flange projects ½in over an iron track let into the interior, vertical face of the curb. Under the flange the seven truck or guide wheels which centre the cap run horizontally; they are fixed to the under faces of members of the cap framing. Below their path are eight blocks of wood bolted to the curb; these project below the brickwork internally and stop the curb from drifting laterally. A flat circular iron track, 3½ in wide, is attached to the underside of the cap base and it is this that runs on the rollers.

 The cast-iron windshaft is about 12ft long, and in section is 8½ in square above the brakewheel, but tapers to 5in square at the tail bearing. The 8½ ft brake wheel is a combination of the clasp-arm and iron-spider types, and is staked onto the windshaft with two distinct cast-iron boxes spaced an inch apart, each made rigid by eight iron wedges, two driven home at each corner. The rear part of the rim, which is much the larger, is bolted to the six iron spokes cast with the upper box; to it also is secured the bevelled face of the wheel, which is independently held by wooden clasp arms staked on with wooden wedges to the lower box. The facing, into which the cogs are set, varies in thickness radially from a mere 7/10 in at the outer circumference of the rim to just over 3in on the inner side. There were ninety teeth with tapering shanks mortised completely through the rim, their overall length being about 10in. The wooden brake contacted the rim of the brake wheel in two sections joined by an iron strap in the section where a corner of the left sheer was cut away to allow room for the wheel.


Tower mill, standing today


Farries: The tower is built of red brick; it tapers internally from a 21 feet diameter base to an 11ft curb. There are ground, spout, stone, bin and dust floors, the overall height from the ground to the top of the cap being about 55ft. To support the spout floor, which is 21 ft high and more spacious than the other floors, the interior wall is corbelled out for four courses of bricks to strengthen the tower and buttress the great beams supporting the stones and the vertical shaft. This is done also under the stone and bin floors. Against this refinement must be set the disposition of the windows one above the other in a manner conducive, over a long period, to curb distortion.

 In the shape of its cap – the Kentish wagon type – Shirley mill differs radically from the tower mills of Lincolnshire, but the ease of movement above windshaft level in so many mills in that county is also enjoyed here. The large brake wheel must needs be housed and the rear of the cap is made to overhang the curb by five feet, so affording protection to the tail bearing of the windshaft situated immediately over the curb, and to the drive from the fantail to the rack on the outside of the curb. This drive was communicated through a set of spur and bevel pinions, now missing, mounted in an iron framework, the final contact with the rack being through a spur pinion.

 The curb is of the dead type. It is of wood except for the iron rack and track, and is anchored to the brick tower by eight tie rods which run down vertically to the underside of the dust floor, where their extremities are threaded and secured by nuts. The iron blocks or “skid plates” carrying the weight of the cap, about twelve in number and spaced more closely where the weight is greater, are prevented from outward drift by a vertical keep flange, on the opposite and outer side of which is the rack; this unusual arrangement meant that sheaves, or centring wheels, could be dispensed with.

 The cast-iron windshaft is square in section; at 4ft from the neck journal it carries an iron brake wheel 9ft 4in in diameter with arms bolted to the rim. The brake itself is of wood and contacts 300 degrees of the rim. The wheel carries an exceptionally large number of wooden teeth – 172 – with the small pitch of 2in. The 4ft wallower has 75 teeth, and from its underside the sack hoist was friction-driven. The upright shaft has a uniform circular cross section of 5in diameter throughout its 25ft, with a dog clutch coupling at 14ft below the wallower. The bridge tree, or sprattle, is of iron, straddling the beams just below stone floor level with the bridging box cast onto it; the two large pairs of stones – 53in peak and 55in burr – were therefore underdrift. The great spur wheel and the two stone nuts are of iron throughout, save for the wooden cogs of the spur wheel, which are pegged in at the back in similar fashion to those of the brakewheel above. A wooden belt drive built on to the T-section arms of the spur wheel connected with a governor which acted for both stones. The spindles of the stone nuts were short, since the nuts themselves meshed immediately below the stone floor; they were raised out of gear by a pivoted forked lever. The great spur also drove a pinion which, through a bevel pinion at the lower end of the shaft, worked a wire dresser from below. Two other drives at intermediate positions on the shaft worked a governor and a second and smaller wire dresser in the floor below. Most of this system is still in situ.


Post mill, standing today


Farries: The surviving mill has a two-storeyed roundhouse; the wall of the lower floor is of brick and that of the upper floor is of vertical weatherboarding. This two-storeyed roundhouse we believe to be unique in Surrey. For the latter part of its working life until it ceased turning in 1902 the mill was assisted by a stationary steam engine installed on the ground floor of the roundhouse. A long belt from the engine drove a pulley wheel on the side of the mill body enclosed in a corrugated iron housing. This projection, which can be seen clearly in early photographs, was removed during repairs about 1912.

 Of the former machinery the mill body retains only the brake wheel, the windshaft and the vertical shaft with five wheels mounted on it. The miller must have enjoyed considerable freedom of movement, for the mill is generously proportioned; it stands about 45ft high, and the bin, stone and spout floors measure 8ft to the ridge, 7ft and 10ft respectively. There was no tail wheel and the windshaft is unusually short, leaving ample room for the bins.

 The iron brakewheel, which consists of an eight-armed spider bolted to a rim 8ft in diameter, drove the cast-iron wallower at stone floor level. Just above the latter is an iron bevel gear with wooden cogs which probably drove the sack hoist thru intermediate gearing. Below the stone floor is the great spur wheel of 3ft 6in diameter, with about 80 wooden cogs and above it a smooth wooden belt drive, probably for a governor. Below the spur gear is a cast-iron bevel wheel similar in appearance to that above the wallower, but with iron teeth; this may have driven a flour dresser in the tail. The pairs of peak and burr stones were both in the breast and underdrift. These stones are now disposed about the garden as ornaments, and the water which flows through the fishponds near them comes from a large tank which has usurped their former  position.

 An interesting detail, still observable in the mill, is the method by which the wooden cogs were held fast in the mortises of the brakewheel. These were 120 cogs having very short shanks, since the wheel has a thickness of only 2¾ in, though a flange cast integrally with it projects out over the rear of the cogs for a further 4in to provide a 6¾ in width for braking purposes. Into the rear of each cog, where the shank projects 1in beyond the mortise, two small iron wedges were driven radially to the wheel, a much less common practice than pinning, and more necessary in this case in view of the shortness of the shanks, for in some brake wheels, as at Outwood post mill, the cogs had an overall length of 11in or more, which reduced the chance of lateral play. The cogs themselves were probably of apple wood, which has the close grain and durability so essential to these hard-worked elements.

 There is one remnant of the braking system at Tadworth; it is a swing-hook of the type described in detail by Rex Wailes in connection with Cranbrook mill; this hook provided a method, ingenious in its simplicity, of applying or releasing the brake remotely by a pull on the brake rope.