1The Sails & Stocks
Two stocks cross at the windshaft, each carrying a sail at either end — four sails from two timbers, not four separate arms bolted on. Each sail is built on a whip, the long outer timber, braced back to the stock by a web of struts. Common sails are simply covered in canvas, reefed by hand like a ship's; spring sails carry hinged shutters instead, opened and closed together by a single striking rod so the miller adjusts all four sails from the ground without climbing anything.
- Whip
- outer sail timber, bolted to the stock
- Stock
- the main crossbeam, one pair carries all four sails
- Shutter
- hinged slat, spring-sail pattern, ganged to the striking rod
- Uplong shaft
- carries the striking gear down through the windshaft's centre
2The Cap & Fantail
The cap is the roof of the mill, and on a tower or smock mill it turns independently of the body beneath it, riding on a circular curb track so the sails can face into whatever the wind is doing that hour. Left to a miller's attention alone, that meant climbing out with a tail pole to haul the cap round by hand. The fantail did the job automatically: a small secondary windmill set at right angles to the main sails, geared down through a train of gears to a pinion running on the curb, turning the cap to keep the main sails square to the wind without anyone touching it.
3The Millstones
A pair of stones, bedstone fixed below and runner stone turning above, dressed with a pattern of furrows cut into the grinding face — furrows that do the actual cutting, while the flat lands between them do the final grinding and push meal outward to the rim. The runner is hung on a rynd, a rigid bar that lets the miller adjust the tentering — the tiny gap between the stones — by fractions of a turn, because too tight scorches the meal and too loose leaves it coarse.
4Winding Gear
Below the fantail's own gear train, the drive runs down through a series of reductions before it ever reaches the curb pinion, because the torque needed to shift an entire cap and four sails against a stiff breeze is well beyond what a small tail-fan alone could deliver at speed. The full sequence:
- Fantail turns directly in the wind, always facing across the main sails.
- A bevel gear at its axle drives a long shaft running down through the cap frame.
- A worm gear at the base of that shaft engages a large spur wheel fixed to the cap's own curb ring.
- The spur wheel turns slowly against the fixed curb, and since the curb does not move, the cap — and everything mounted to it — turns instead.