Engine Operation


The distinct advantage of wind engines is their ease of use.  Unlike custom windmills that had to be manually turned into the wind, wind engines automatically turn the sails into the wind.  In fact, an operator is not required to make adjustments of any kind to keep the engine operating at peak efficiency.  Regardless of weather conditions, wind engines are built to be self-regulating—they even brake if strong gales prevent safe operation.





Aside from a periodic visual inspection, not much maintenance is required to operate a wind engine—which is exactly how it’s designed to function.  Many are so well built that “tune-ups” are virtually unheard of.  All that is required of the operator is ensuring that the contact points are well-lubricated with gear oil.  On early wind engines, this required operators to climb the tower every few days to oil the gearbox.  Although this design was still a vast improvement from operating a custom windmill (that required daily maintenance with several large gears), it was not uncommon to hear of people losing their balance and falling to their death.


When safety became the top priority of manufacturers, designs were modified to make maintenance trips less daunting (or, at the very least, less frequent).  One short-lived model was the “tilting tower” design, in which the tower, centrally balanced on a hinge, flipped the windmill so that the gearbox could be oiled from the ground.  Another design was the “pull-the-wire” concept, in which the operator released more oil into the gearbox from the ground by releasing small amounts from a larger reservoir (of course, the tower still had to be climbed to refill that reservoir).


Ultimately, an innovation of the Elgin Windmill Company prevailed.  “Self-oiling” gearboxes required fewer than one oil change per year.  These operated with totally enclosed gearboxes that contained the oil within and protected the gears from weathering.  It did not take long for windmill manufacturers to borrow this design, which continues to prevail.



Speed Control


Halladay’s original patent called for four spring-hinged “self-furling” sails, which could, like modern wind turbines, turn upon their axes to alter the surface area exposed to the wind.  The sails were not mounted directly to the gearbox but rather to a set of axles: as the hub increased in rotational velocity, a spring control turned those axles to expose less surface area to the wind.  If the velocity dropped, the sails turned back to their normal position.   


When engine designs changed to employ rigid annular sails instead, Halladay addressed the speed control issue with the pivoting sectional wind wheel.  The sectional wheel similarly operated on a set of springs, but rather than turn the thin, individual slats of wood out of the wind, each of the six sections of the wheel opened to allow wind to pass through as demonstrated below:

An Aermotor gearbox oiling diagram, designed to "last for many years."

Photo from Aermotor Windmill

Demonstration of a pivoting wind wheel. As the wind speed (and pressure) increases, it activates controls that automatically fan the sections of the wheel open, allowing air to pass through the sails rather than turn them. This operation was present on both vaned and vaneless models.

Illustration by Tom Haskell

While Halladay successfully sold his “standard” wind engine models across the Midwest, the problem of speed had to be addressed on models with a solid, non-pivoting wheel.  To keep the mill from spinning out of control, a second, smaller vane was added.  While the main tail vane sits perpendicular to the wind wheel and keeps the gearbox in the wind, the smaller vane operates parallel to the sails.  


If the wind is strong enough to push the small vane, it swings the gearbox out of the wind (this is not unlike the manual motion of “quartering” the cap of a custom windmill).





There are several design patents in relation to the construction of the gearbox and mechanisms, but the basic principle involves a simple geared crank to create a mechanized water pump.  Once the annular sails are facing the eye of the wind, they will turn the wind shaft.  The wind shaft passes through a smaller gear (akin to a spur gear) and into a bearing at the end of the gear box (on some models, this may turn an additional gear to activate the self-oiling feature).  


The spur gear on the wind shaft turns a larger toothed gear next to it.  The larger gear is attached to the pumping rod via a pitman arm; the arm converts the rotary motion of the gear into a vertical motion for the pumping rod.  The best way to think about the motion within the gearbox is that of an automobile engine—rather than the vertically-moving piston turning the crankshaft (that turns the wheels of the car), the crankshaft turns to move the piston.


The stand pipe contains the chambers and check valves necessary to bring water to the surface.  The downward motion of the pump forces the check valve to open, allowing water inside the chamber.  As the pump moves upward, the weight force from the water closes the check valve, bringing water with it.  This process continues as long as the engine is running.

Illustrating how the rotary motion of the gears drives the vertical motion of the pump.

Illustration by Tom Haskell