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Technical descriptions of English windmills




Tower mill, standing today


Martin Watts, Wiltshire Windmills: Wilton mill, built {in 1821} upon a “modern and improved principle”(1), has a tower in the form of a truncated cone of brickwork and originally had a group of low buildings around the base; these were removed in the 1930s. As restored, the mill has a timber stage at first-floor level. The cap is dome-shaped and was originally lead-covered. This cladding was replaced with iron sheets by Whites of Pewsey in 1910(2) and the present cap is of sheet aluminium on the original wrought iron ribs. The cap turns on a shot curb with twelve iron rollers and the top of the brickwork is now tied with a concrete ring beam to prevent any distortion of the curb. The cap and sails are turned by a six-bladed fantail on a timber carriage, which is geared to an iron-toothed ring on the outside of the curb. In 1978 a hand crank and disengagement mechanism and a brake were added to the fantail gearing.  

 At present there are one pair of common and one pair of single-sided patent sails {this appears to have been the arrangement at the end of the mill’s working life, as a photograph of it  derelict in the 1920s shows}. It seems that the mill was originally built with four patent sails. The roofs of the outbuildings would have provided the miller with a working platform for {the common} sails.

 The sails are fixed to a coffin cross cast integrally with the windshaft; the shaft is circular and tapers towards the tail. The brakewheel is a single casting some 8’ 6” in diameter, keyed onto the windshaft, and carries 108 wooden cogs driven into mortices in the iron rim. The wallower is a single cast bevel gear which has 37 teeth, giving an increase in speed of nearly three times. The wallower is mounted at the head of the iron upright shaft and close below it is an inverted bevelled face timber and iron wheel which drives the sack hoist by friction. The sack hoist is engaged by the miller pulling a cord which hangs down through the mill, and which raises a similar bevel wheel on the end of the hoist winding drum until it touches the wheel on the revolving upright shaft, turning it by friction between the two wooden surfaces. Below the cap is the bin floor, through which the upright shaft passes, and which has bins on one side only.

 At stone floor level there are now only two pairs of stones in situ, with one pair set up for milling. These are 47” diameter French burrs, enclosed in an octagonal wooden tun with a hopper, fed by chutes from the bins above, supported on a wooden horse. All the stone furniture is new, as is the iron crane used to raise the runner stone for dressing. The second pair of stones are 47” Peak stones for gristing. When advertised in 1828 the mill contained three pairs of stones, a flour machine and a dressing mill. The third pair of stones, located on the south side of the upright shaft, do not have their bridging and support timbers built into the structure integrally, as do the other two pairs, and would therefore seem to be an addition and perhaps the reason why the patent sails were not adequately powerful.

 The stones are underdriven, the drive coming from the great spur wheel which is mounted at the foot of the upright shaft, just below stone floor level. The great spur wheel has 72 wooden cogs in its iron rim and meshes with iron stone nuts. These are raised out of gear by a screw and ring device. Each stone nut has 27 teeth. The governor is driven by chain from a wooden pulley on the upright shaft just above the great spur wheel. Both stone spindles bear on iron bridges hung below the stone floor. 

 The upright shaft carries an iron mortice crown wheel, with 72 wooden cogs, over the stones. This is an inverted bevel gear and drives a horizontal shaft through a bevel pinion with 29 teeth, which carries a rope-drive pulley at its outer end; from this pulley the drive was taken to the floor below to the wire dresser. A wire machine, recently brought from a watermill in Wales, has been rebuilt at that level. The lowest floor of the mill would have served as a store and granary.

(1) Reading Mercury 4/8/1828

(2) Wiltshire Archaeological Society Bulletin April 1972