WINDMILL, a kind of mill, the inter nal parts of which are much the same with those of a water-mill ; from which, however, it differs, in being moved by the impulse of the wind upon its vanes or sails, which are to be considered as a wheel on the axle. Plate, Windmill, is a verti cal section of a windmill of that kind, which is called a smock-mill, i. e. when the building, the mill, and machinery are fixed, and the head of the mill support ing the axis of the sails turns round upon it. A A are the walls of the mill•house, which is longer one way than the other, and the section is through the shortest side ; in this direction it will but just con tain the machinery, and leave a passage ; in the other. .direction the house is longer, and is used as a warehouse to stow the corn and flour. The roof of the house is framed of large beams, a flooring is laid on these beams, and then the whole 18 covered with sheet lead. Eight long up right beams, B B, are framed into the roof of the house, and disposed round in a circle; at the upper angle they support a circu lar kirb, D D; the eight uprights, B are braced by cross pieces framed be tween them, so as to render the whole building very staunch ; the outside is covered with weather-board, just to shoot off the rain, but open enough to admit the wind to pass freely through the house. Upon the upper fixed kirb, D D, thirty-six rollers are placed (two of them are seen in the section ;) these rollers turn in mortices, cut through a circular ring of wood, which keeps the thirty-six rollers in their places, and at their proper distances from one another. The rollers support another cir cular wooden ring, a a, on which the head of the mill is framed. This framing consists of two beams, b, halved into the ring, parallel to the main axis of the sails, and including the great cog wheel be tween them, only one of them is shown in the figure, the other being taken away in the section. Two cross beams, d and a, bolted upon b 5, supports the bearings for the main axis, and another cross beam, f, bolted to the under side of b, to sus tain the upper bearing for the vertical axis.
We now come to speak of the machi nery: H 11, are two of the four sails seen edgeways ; the broad part of the sails, which is covered with cloth, is set oblique to the plane of the sails, motion, and the axis of the sails is set in the di rection of the wind; it is by the action of the wind upon the oblique sail, that it is made to revolve on its axis ; the wind acts constantly as a wedge upon the sails, and thus drives them round. The four sails are firmly bolted to an iron cross, e, cast in one piece with the main : abcdefgis a wooden pole fixed on at the intersec tion of the four sails, and forming a con tinuation of the axis ; Ibur ropes are ex tended from the end of the pole to the end of the sails, and hauled tight by a block of pulleys, by these the sails are stiffened, and prevented from bending by the action of the wind upon them : S is the main cog wheel, fixed upon the iron axis, and turning round with it ; it has a flexi.
ble ring of wood, composed of five seg ments, and jointed together by iron hing es, and compassing it ; one end of this ring oewood, called the brake, is fastened by a joint to the under side of the beam, h ; the other end comes round nearly to the same point, and is fastened to a long le ver, i, called the brake lever. When this lever is lifted up, the brake is lifted off from the wheel, and does not touch it on any part, and the wheel and sails can turn ; but when the lever is suffered to fall down, the brake closes round the wheel, and prevents the wheel and sails from turning. The brake lever is lifted up by a rope, lc, which hangs down in reach of the miller when standing on the stage, II, built round the mill for the purpose, as also for clothing or unclothing the sails. When the brake is to be held up for any length of time, while the mill is at work, the brake rope is hooked on a hook driven into one of the uprights, BB. The head of the mill can be turned round upon the thirty-six rollers, to set the sail round in the proper direction to meet the wind. The fixed kirb, D D, has a ring of cogs all round its outside, which work with a pinion on a spindle, /, turning in a: socket fixed by iron braces. To the moveable head of the mill, on the upper end of the spindle, 1, a crown wheel is fix ed, which is turned by a small pinion on the same spindle, with a wheel, In, round which an endless rope runs, and which hangs down in reach of the miller when on the stage, I. By pulling down one side of the endless rope he turns the wheel, m, and by the pinion the crown wheel, and its pinion, which acting against the teeth in the kirb, 1), turns the head round upon the thirty-six rollers, and puts the sails in any position according to the wind : o is a roller turned upon an iron pin fastened to the under 'side of the beam, b, and acting against the inside of the kirb ; another similar roller is fixed to the other beam, which is parallel to b ; their use is to keep the head steady upon the rollers, otherwise the head might be thrown backwards by the action of the wind upon the sails. The upper part of the head is light framing and thin boards, covered with copper just to exclude the rain. The main cog-wheel, n, turns a trundle, K, on the upper end of a long vertical shaft, L L, which comes down to the ground, and turns in a socket support ed on Masonry at 1I : p is a crown wheel of fifty-six teeth turning another wheel of seventeen teeth on horizontal, which has riggers, g, on it to turn bolting mills and dressing- machines in the tipper room. In the lower room a large spur wheel, t, of seventy-two teeth, is fixed, and turns a nut on each side of it, one of twenty.eight, the other of twenty•six teeth, on the i4 spindles of their respective mill-stones, a and a.
The construction of the mill for grind. ing flour is well explained in the article MILL, to which we refer our readers.