Construction

The Tower

Like all other windmills, the height of a wind engine is determined by the tower.  Companies offer different tower designs and sizes so trees, barns, or homes will not obstruct the wind.  Because wind engines contain no wooden machinery or weather-sensitive equipment, the towers are completely open to the elements.  Most towers follow the same, simple design: they are rectangular prisms, often tapering in size near the gearbox.  A ladder must be present so that the operator can access the gearbox for maintenance.  These towers usually have diagonal cross bracing between sections for added support. 
 
Wooden towers are of simple construction, without the unusual joists used in custom windmill construction.  Since there is no fear of an explosion, metal fasteners can be used instead of wooden dowel rods.  The towers are usually sealed and painted to better protect them from weathering.  In the early days, wooden windmills were not only less expensive, but considered “safer” because they were less likely to attract lightning (despite having metal gearboxes). 
 
Galvanized steel windmill towers eventually replaced wooden ones.  When the materials and galvanizing methods became cheap enough for mass production, manufacturers marketed them as being more reliable and far less likely to weather or rust.  Galvanized wind engines quickly became popular and are considered “standard” construction today.
 
There are, of course, exceptions to every rule.  The towers of vertical-axis turbine-style wind engines, for instance, were partially enclosed as a means of “trapping” the wind within the turbine.  Oftentimes, the architecture of these towers was designed to resemble homes or ornate water towers.  Windmills like Romeo and Juliet by Frank Lloyd Wright and the Oughton Estate Windmill in Dwight use towers more traditional to custom windmills.

An OK windmill from Challenge Windmill on
Batavia's Riverwalk

Photo by Tom Haskell

The Tail Vane

The simplest wind engines have tail vanes.  This paddle-shaped vane is mounted directly behind the sails into the gearbox of the engine.  If the wind suddenly blows from the side of the windmill, it pushes the vane (and, thus, the gearbox assembly) into the wind.  There are no engineering specifics regarding the size or shape of the vane, but manufacturers utilized their flat surfaces to advertise the name brand (sometimes highlighted by a particular color or logo), making their wind engine recognizable to the public.
 
Some manufacturers constructed “vaneless” models, meaning that they do not require vanes in their construction to be kept in the wind.  With few exceptions, these were usually pivoting sectional wind wheel models.  The “trick” to this design is that rather than have the wind turn the sails from the front, the wind actually turns the sails from behind.  In other words, the windmill is designed to accept the tail winds that would otherwise destroy a custom windmill or turbine.

A vaneless model on Batavia's Riverwalk

Photo by Tom Haskell

The Gearbox

Although called a gearbox, the early wind engines could hardly be considered a “box.”  The first wind engines were known as open-geared windmills; as the name implies, the gears sat open in the elements (one of the reasons they required such frequent lubrication).  The gears, weights, and pulleys are all cast piece by piece.  Since many early manufacturers made wooden windmills, they did not have their own machine shops; a blacksmith would be contracted to cast the metal pieces on behalf of the company.

An Aermotor gearbox illustration

Diagram from Aermotor Windmill

The Sails

Daniel Halladay’s original wind engine patent used four wooden paddle sails like to those found on custom windmills.  The paddles were always at a slight angle to form the “angle of weather,” necessary for the wind to push the sail in one direction.  These sails were designed to pivot on their axes depending on wind speed (see Wind Engine Operation).
 
After the Civil War, however, the design was changed instead to annular sails: thin, wooden pieces arranged in a full circle to create a “wind wheel,” allowing more surface area to be exposed to the wind, ideally creating a more efficient windmill.  Likewise, each slat is installed at a slight angle so that the wind will push the wheel in one direction.  Because it would be cumbersome to adjust tens of thin paddles every time the wind changes, the pivoting sectional wheel was created.
 
Wooden sails slats are carved from templates designed for each model windmill.  The thin slats are cut from larger, thin sheets (which are used as much as possible, to reduce waste), then painted and fastened to a hexagonal frame.  There are typically two frames, an inner ring and an outer ring, to form the circular sail pattern.  On a pivoting sectional wind wheel, the frames are allowed to open or close depending on the wind speed. 

Solid-wheels can be made of wood or metal.  The metal pieces are made of sheet metal, usually galvanized and painted.  In construction, these wheels differ only in that they cannot pivot in the wind; they rely on the small weather vane to turn the gearbox and sails out of strong winds.
 
Turbine style sails involve the same principles of construction, but are built upon a vertical axis so that they can rotate in any wind direction.  Though not nearly as popular as the standard wind engine, these turbines were innovative for their time.

Sales and Assembly

Most manufacturers first had trained salesmen visit customers to determine the design aspects of the wind engine.  By surveying the land, a salesman could offer a quote including the proper tower height, sail diameter, style, and placement to ensure the engine would run efficiently with few obstructions from surrounding structures.  This was a service of both direct manufacturers and catalog companies.
 
Every wind engine, then, was made to order.  While the engine is created based on the salesman’s specifications, a well-digger will arrive at the site to “open” wells to underground aquifers.  This process was not unlike the same methods used today; but without the aid of power equipment, digging a well was manual labor.
 
With such simple construction also comes simple assembly.  Wind engines often shipped in pieces that could easily be assembled on site.  The engine was typically built complete on the ground, and then manually hoisted into place over the well.  Once the engine stood vertically, the pump rod was connected, the tower was secured to footings that ran deep underground, and the engine was ready for pumping.