How a Windmill Lifts Water
There are mills standing in Caldwell County that have been lifting water since before the people who own the land were born, and nobody has ever paid a cent to run one. No meter. No fuel. No wire across the pasture, no controller to fail, no call to the electric co-op when a line goes down in a storm. Wind turns it, and when the wind quits it stands there and waits.
For a machine that has been obsolete on paper for about seventy years, it holds up remarkably well. Here's what's actually happening up there.
Everything above the gearbox goes round... everything below it goes up and down.
That sentence is the whole machine, and the rest is detail.
The wheel is the fan of curved blades, and it does not need the kind of wind people assume. A steady breeze moves it. The blades are set at an angle to catch air from the front and spill it out the back, and there are a lot of them, which is why a farm mill starts turning in conditions that would leave a modern three-blade turbine standing still. A windmill isn't built for efficiency. It's built for torque at low wind, because the job is heavy and the wind out here is usually mediocre.
Behind the wheel, the tail vane keeps it pointed into the wind as the wind swings around through the day. It also does the more important job, which is stopping the thing. Pull the lever at the base of the tower and the tail folds, swinging the wheel side-on to the wind until it loses interest and quits. A hard blow will do the same automatically on a mill that's set up right. If your furl lever doesn't work, that isn't a maintenance item you get to put off until spring. A mill that can't be shut down will eventually shut itself down, expensively, on a night when nobody's watching.
Under the wheel sits the gearbox, running in a sealed oil bath. Inside it, gears convert rotation into reciprocating motion and gear it down hard while they're at it, so the wheel turns several times for every single stroke below. You are trading speed you have plenty of for force you don't. That trade is the reason the thing works at all in eight miles an hour of wind.
That oil is the one item on the whole mill worth being slightly obsessive about. It doesn't want changing often. It wants being there. A gearbox run dry grinds its own teeth off, and replacing it means getting a hoist and a crew up a seventy-year-old tower, which costs roughly a hundred times what the oil did.
The part nobody sees
From the gearbox, a sucker rod runs down the middle of the tower and into the well casing, in threaded lengths, all the way to the water. It's heavier than people expect. On a deep set, a serious fraction of what the wheel is lifting is the rod lifting itself.
At the bottom, below the water line, is the cylinder: a brass or stainless tube with a plunger in it and a check valve at the base. On the up-stroke the plunger rises, the bottom valve opens, water comes in underneath, and the whole column already sitting above the plunger gets shoved a little higher up the drop pipe. On the down-stroke the bottom valve slams shut so nothing falls back, the plunger travels down through the water, and it starts again. A few quarts a stroke, maybe. Ten or fifteen strokes a minute in a decent breeze.
It is an absurdly slow way to move water and it never stops, which turns out to be the entire point.
Sealing the plunger against the cylinder wall are the leathers. On a great many mills that is still exactly what they are, cupped rings of actual leather riding against brass, swelling slightly when wet to make the seal. They wear out. They are supposed to wear out. When a mill turns beautifully in a good wind and delivers nothing at all, worn leathers are the first suspect and usually the right one, and putting a set in is an afternoon's work rather than a rebuild.
Why it doesn't matter that the wind stops
That bottom check valve is also doing something people miss: it holds the column. Water that has been lifted does not run back down between gusts. So a mill that turns for twenty minutes, sits still for an hour, and turns again is not starting over each time. It's picking up where it left off.
Which is why comparing a windmill to an electric pump on gallons per minute is the wrong comparison, and why people who make it come away unimpressed. A submersible is sized to meet demand at the moment demand happens. A windmill is sized to fill a tank over a day, and the tank is what meets demand. Get the storage right and the wind becomes almost irrelevant. Get it wrong and you'll stand there in a dead-still August afternoon watching cattle drink your margin for error.
When it goes wrong, and how much to worry
Turning but not pumping is leathers, then the bottom check valve, then a parted rod down the hole. In that order, and the first one covers most of it.
Turning slowly, or refusing to start in a breeze that used to move it, is the gearbox. Oil, or wear, and the difference matters.
Pumping less than it used to is the one where people replace parts they didn't need. Before you touch the mill, find out where the water is standing in the well. Levels drop in a dry stretch. A cylinder set at a depth that was generous in a wet year can be marginal in a bad one, and nothing on the tower is broken.
A bang or a hard knock up top means shut it down now and call somebody. That noise is a machine coming apart in slow motion, and it is much cheaper to catch in the middle than at the end.
Whether the old one is worth saving
Usually. The tower and the wheel are the expensive parts and they routinely outlast every component bolted to them, which is why mills that look finished from the road so often aren't. We've put back into service more than one that the owner had written off.
Sometimes the answer is no, and that's a shorter conversation than people expect. But it's worth having somebody look before it comes down, because the version of this that we hate to see is a good tower on the ground and a new pump on a meter next to it.
More on rebuilds and installs on windmills, and what a call-out involves on service and repair. If you're weighing a mill against a submersible, a turbine or solar, all four are laid out side by side in four ways to get water out of the ground.
Give us a call
Royall's Windmill & Pump, 15240 FM 1322, Luling. (512) 844-4960, or royallswindmill@yahoo.com. Caldwell, Guadalupe and Gonzales counties and a good way past the edges of all three.
Same people quote it and do it, which means there's nobody to hand you off to and nobody to blame if it's wrong.