Article

About Windmills

Introduction

Sibsey Trader Windmill, Lincolnshire

Our look at windmills, is structured into a number of steps, first a quick overview,  an historical perspective and then a more detailed look at each type, also introducing some of the terminology used. This approach serves you well in that it allows you to get the level of knowledge that you require and come back later to look up specifics and is also designed to be expandable allowing us to extend the coverage over time.

The development of windmills in Britain

Wind has been used for a very long time as a form of power, with a version being explained in the 1st century AD to power an organ to play music, and since that point around the world there have been constant developments.

In Britain waterwheel driven mills were introduced by the Romans, if not already in existence before, and much of the business end of the technology, for example grinding corn, and transferring the drive by about 90 degrees, is common with the windmill. The Domesday Book (before 1086) records many mills but does by specifying them by type. As well as water powered mills using streams and tidal mills, there were also mills powered by animals walking around a circular track. Its said that the earliest records of windmills in Britain is from the 12th century. Treadmills, large wheels a little like a hamster wheel also existed in some places, where a number of people were used to provide the power, Gloucester prison had a large wheel of this type powered by prisoners and although the wheel no longer exists, the place where parts of it was fitted is still visible.

By the 14th and 15th centuries we have illustrations, including those in manuscripts, stained glass, wood carvings and  brasses, and some think the technology developed independently in western Europe to the earlier wider developments, but information and techniques have, since the stone age, filtered around the old world, and with the crusades if not before Britons would have seen a variety of advanced eastern designs. Its likely that windmills in different forms have existed here for a very long time, and probably taken for granted, however we are starting our look from the earliest illustrations we have.

The earliest illustrations we have are of small mills made completely of wood, looking like a post mill.

The development of mills in Britain have generally followed the route from post mils, to smock mills, to tower mills, which we will look at below.

While the windmill was in existence for a long time before we know of its design in Britain it was after this period that British and Dutch inventors and millwrights made a series of technological advances, particularly in ways to automate the turning of the mill into the wind and in sail design that was able to both use variable wind. You cannot allow a windmill to run too fast as the friction caused between the wooden parts builds up to produce heat, and rubbing two sticks together we all know can create fire. Very many mills burnt down.

Use of windmills

Windmills we all know were used to grind corn, but they were also used for several other uses. A large number are drainage pumps, often working with a scoop wheel that moves water up from one level to another, fewer use a 'archimedes' screws, and piston pumps to achieve the same, the Dutch used a very large number and had by the 19th century over 9,000 windmills. In Britain you find very many drainage or pumping windmills within East Anglia. Others were used to drive saw mills, thrashing, pressing oil from seeds, and grinding many different materials.

In some places a miler had several mills with perhaps a watermill and a windmill, and in many places there were a line of windmills. Mills were also used in cloth making for fulling, and turned England into a major cloth-making country from the 14th century. They were known as walk mills in northern England and tuck mills in the south-west. Mills were adapted to other industrial uses, such as paper-making, lead-smelting and tanning. The most dangerous of these was gunpowder-making. The risk of violent explosions meant that powder mills were generally sited well away from towns and villages. The Industrial Revolution saw the creation of large-scale spinning mills. Generally windmills were favoured in flatter windier places and watermills where there were more hillside streams.

Types of windmills in Britain

There are three basic designs, that tend to follow in series historically, the post mill, then the smock mill and then the tower mill. A range of examples of all three can be visited and photographed and some can be seen working. The basic requirements of all windmills in Britain is to be able to turn the sails to face into the wind, as the weather we all know here is inconsistent and wind can come from any direction.

Although in Britain we tend to look at each of these designs following the other generally, some historians talk of just post mills and tower mills and look on the smock mills as a design that came out for a period in the middle of the time tower mills were being built. Tower mills without rotating tops had been used elsewhere for a long time.

By 1760 windmills had reached an advanced level of sophistication. They were equipped with automatic regulators that controlled the speed of rotation, that adjusted the pitch of the fan blades for maximum power at a given wind speed, and that oriented the fan so it always faced directly into the wind. When they were used for milling, they were equipped with devices that regulated the pressure of the millstones on the grain. At that time an improved and practical steam engine was invented and this led to both the dropping off of further development and eventual replacement of most of the mils with engines. Most of the technology was forgot so for example when aircraft came and started to fly they overlooked much of what had been known earlier and it was not until the 1930's that variable pitch propellers were rediscovered, although they had been used in mills 200 years before. Today with wind turbines again some information from windmills, is being rediscovered, and applied.

In the time these windmills were being built, repaired, rebuilt etc., there was quite a lot of variation, different millwrights creating different structures and differences between regions as well as the level of investments available for individual mills, some are works of art, while others are of a practical design, some are large, some small, the variation in the size of tower mills is particularly noticeable. You can find small tower mills and large smock mills. You will also find some combination designs and a few that were powered both by water and wind, of which at least one still exists. They have a varying number of sails, examples you can see today having from 2 to 8 sails, and you will find some sails rotate clockwise, while most turn anti-clockwise. Given also the variation in materials and locations from town centres to idyllic country settings, from the top of hills to by lakes, and the sea, the opportunities for the photographer are enormous.

Post Mills Post mills are built with a body that rotates around an upright post. The body, also known as a buck, houses all the workings and is supported on a base of some type, early ones on the wooden arrangement standing on the ground, but later ones on pillars and upon the top of a brick or stone built round house, that can be a single floor or several high, however all the workings of this type of mill is in the buck, and any roundhouse is for storage or living space. They are rotated into the wind by using a lifting or tail pole also known as a tiller beam or later by rear fan arrangement.

Smock Mills Smock mills differ in that the body of the mill stays still and only the top piece moves around to face into the wind, this allowed larger mils to be developed housing more stones. Still mostly a wooden structure, but needing to approach a round shape so the sails don't have to be too far away from the body, but being built with straight timber, these are often 8 sided although others you will find examples of range from 6 to 12 sides in Britain. Like the post mills these are often found on top of brick bases, varying from a single storey to several storeys high. They have also been known as smock mills, and its thought to have originated from the similarity in shape to a smock worn as a part of period agricultural costume.   Picture by Clem Rutler 2007   Killicks Mill, Meopham, Kent

Tower Mills Tower mills are a further development replacing the wooden structure with a circular stone or brick tower. The major advantages are in being able to get extra height, the strength to withstand storms and being more weather tight and less at risk from fire. Extra height allowed the mill to work on more days both by catching more wind by being higher but also often being able to support larger sails and larger numbers of sails. Most are circular, but some start off another shape and convert to being circular as they gain height, in some cases because they were built upon a smock base. Some tower mills are very tall, the largest today being 10 storeys,  just short of 100 feet, but a few even larger ones existed. It also perhaps lines up with both general changes in the structure of buildings and the way, and by who they were financed.

Sails

Sails often called sweeps, were originally a simple lattice arrangement that sail cloth was spread out over, as the power of the wind changed the miller had to adjust the cloth coverage, these are referred to as common sails. The only other way he had to control the speed was by using a brake to slow it down. Early sail designs were flat but later ones involved a twist similar to found on propellers. Sail design evolved first by having a spring sail operating a bit like a Venetian blind we find in homes and offices, once set up this could be self regulating, but the sails had to be stopped to set it up. Next came a roller blind design that could be remotely changed without needing to stop the sails. Next came the patent sail,  a combination of a hinged sail and a remote control chain arrangement, by changing the weight hung on the chain the speed of the sails could be regulated, without needing to stop them.

Fantails The automatic fantail was invented in 1745, this is the tail fan you see behind some post mills and on the roof of some tower and smock mills.  It is made of a set of five to eight vanes mounted on the tail pole or the ladder of a post mill at right angles to the sails and connected by gearing to wheels running on a track around the mill. When the wind veers it strikes the sides of the vanes, turns them and by a connection the track wheels also, which turn the mill body until the sails are again square into the wind. The fantail was also fitted to the caps of many tower mills, driving down to a geared rack on the curb.

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