About the windmill
Lacey Green Windmill can be found at the top of the escarpement of the Chiltern Hills at the north end of Lacey Green village in Buckinghamshire.
The mill, which is leased to, and maintained by, The Chiltern Society, was in use for 260 years and the unique oak machinery inside the windmill dates from 1650, making it the oldest smock windmill in the country.
From fantails to flour
The cap, the roof of the mill, rotates by means of the fantail mechanism (pictured) so that the sails are always luffed (to windward). The sails are fixed by a metal hub to the exterior end of a huge, 635mm diameter axle, the windshaft. Some way along the windshaft there is a large, almost 3m in diameter, six-spoked wheel known as the brake wheel.
The top floor (the dust floor), houses the top end of the 356mm diameter main shaft, upon which another large wheel, the wallower – 1.4m diameter, with hornbeam teeth and 4 oak spokes – engages with the brake wheel above. This transfers power via the main shaft to the rest of the mill. Also on this floor are two hoppers which store grain and flour for processing on the bin floor below.
The main shaft powers three machines on this floor: 1. A sack hoist, used to raise sacks of grain (or flour for additional grinding) to higher floors; 2. A smutter, for cleaning grain; and 3. A bolter for sifting and grading flour. The smutter and bolter at Lacey Green Windmill date from the 19th century and were brought in to replace similar ones that were beyond repair. Also on this floor are two hoppers with grain for the stone floor below.
A large beam on this floor supports the bottom end of the main shaft, where power is transfered by the great spur wheel. Two much smaller, toothed wheels (stone nuts), when engaged with the 1.8m diameter great spur wheel, drive one of two overdrift (runner or top) millstones.
One pair of millstones, made from Derbyshire Millstone Grit, was used for coarse grinding oats or barley for animal feed. The other pair, made from French Burr Stone, was used for grinding wheat into flour.
The picture shows one of the stone nuts engaged with the great spur wheel, which in turn would drive one of the overdrift millstones at the lower end of its square driveshaft.
Below ground level this floor houses large timbers which support the millstones on the floor above. The underside of the bed (fixed) millstones can be seen. Between the timbers two flour boxes (or bins) collect the product of the millstones. In order to fine tune the milling, other timbers on this floor – supporting the overdrift stones – can be adjusted to alter the gap between the stones, to ensure that they never actually touch.