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  #1  
Old 03-05-2022, 09:28 PM
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arizonian arizonian is offline
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Default Tilting at Windmills

Tilting at Windmills
I am documenting my windmill build project for any one that wants to follow along. There will be multiple photos, and there will be gaps and out of sequence shots, so please bear with me. Don’t pay attention to the dates on the photos as they will be all over the place. This project was started in earnest at the end of September with the first piece of material that was bought.

The first thing needed is to size the windmill. A one-half scale seemed plausible, so that is the direction this is going. This is not a true model in the sense of copying down to the last bolt a vintage Aermotor windmill, but the operating mechanisms and principles are based on the general Aermotor design. Also, I do not have access to a foundry so any and all castings in the original mill will be fabricated steel to mimic the design intent rather than the actual dimensions.
The Sail:
To calculate the sail (wheel) several photos were taken and printed and then drawn on to map out the curvature of the blades, the openness of the wheel and the angle of attack to the wind. The chord angle of the curved blade coupled with the percent openness of the wheel, the number of blades and the scaling factor and some rudimentary trigonometry gave a pretty fair estimate of the blade geometry. As seen in the photos below, the sail is not solid wheel but has a roughly ~38% openness.

The chord angle is about 35°. Once the size of the sail blade and chord angle was determined, the actual dimensions of a half scale blade could be calculated. The wheel in my windmill will be forty-eight inches in diameter with a blade length of fifteen inches and a flat width of six and five-eights inch. The angle of attack to the wind depends primarily on the speed of the wind. As this is a fixed pitch turbine, the angle of attack will change over time depending on wind velocity and the RPM of the sail.

The curvature of each of the blades required a wooden buck for final forming. Each blade was formed with a slip roller. The buck was created using a router with a pivot to mimic a part of a cone at the appropriate geometry. Since there is always springback when cold forming steel and the slip roll in use only duplicated approximately, the buck and hammer was used to bring the final form. The buck was reinforced on the bottom when repairs to the buck were made necessary. The last photo is the soldering fixture to attach the bottom clip and middle clip to each vane.

Yes, I did take a photo of a photo. We'll see how that turns out later.

More to come.
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Bill in sunny Tucson

I believe in gun control.

Gun Control: The ability to consistently hit what you are aiming at.

Weldor by choice, engineer by necessity.

Last edited by arizonian; 03-05-2022 at 11:41 PM.
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  #2  
Old 03-05-2022, 09:34 PM
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Whitetrash Whitetrash is offline
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So cool, "Old Man" would be all over this
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  #3  
Old 03-05-2022, 09:52 PM
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arizonian arizonian is offline
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Center Hub and Sails: The center hub presented numerous challenges. A dividing head, a 20 inch sine plate and the appropriate number of turns that were mathematically correct to place the spokes in their intended position. There are twelve spokes, six on each hub face, with three leading and three trailing spokes on each face. There is a one and a half inch gap between the leading and trailing spokes on opposing hub faces. The spokes cross each other at the inner ring and have a separation of two inches at the outer ring. The spokes also lean in toward each other so they are in a staggered alignment at the outer ring. The first set of three holes for the leading spokes were milled, drilled and tapped an each face without a hitch, but a mathematical error placed the trailing spokes in the wrong position. A bit of welding to plug the mistakes and a correction was made to the formula.

The sine plate was posted about earlier, but in brief, it is fabricated from a short length of S4x7.7 S-beam and a three-eights by five by twenty-one inch cap plate. The sine length is twenty inches between centers. The twenty inch length of the sine plate was required to allow the mounting of the dividing head and tail stock at the appropriate angle to drill and tap for the spokes in the hub.

The inner and outer rings were cut to length, drilled and rolled with a cheapie Harbor Freight ring roller. Spokes are from 1/4" hot rolled and threaded on each end.

I have to admit that the spokes are not exactly what I hoped for. I learned that there are two threads almost exactly the same but off by .008". The desired thread is 1/4-20 UNC, but the die I used is a #14-20 die. Turns out that there used to be #14-20 (.242") standard that is no longer in use today.

The last shot is hammer forming the inner (bottom) clips. Thanks, Three Piece!

More to come.
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Bill in sunny Tucson

I believe in gun control.

Gun Control: The ability to consistently hit what you are aiming at.

Weldor by choice, engineer by necessity.
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  #4  
Old 03-05-2022, 10:24 PM
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I am going to enjoy watching this. Do you intend to pump water with it?
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  #5  
Old 03-05-2022, 10:30 PM
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Welding Positioner

Early on I discovered that my welding skills are not what they used to be and I needed a welding positioner. I don't have many photos of the build so this is the description.

A DC treadmill motor supplies the power to turn a Ford front brake disc and hub bearing. There is a carbon block against the back side for the ground. The small lathe chuck is threaded on a 1-1/2"-8 spindle that is bolted to the front of the disc.

The drive between the spindle and the motor is a 3/4-10 UNC all-thread turned down on each end and is supported by two bearings that have a machined fit on either end of the "drive tube". The "drive tube" is cut away to allow access to the opposing gear. The all-thread acts like a worm against a worm gear and will adequately drive one direction but balks when choosing the opposite direction. The connection between the worm and the motor is a piece of rubber tube (air hose) with no clamps on either piece. The voltage source for the treadmill motor is a battery charger and a $10 digital speed controller. Getting the polarity backwards will let out the magic smoke on the controller.

The plastic gear was an experiment to see if a larger worm gear could be hobbed out of steel or aluminum. A 3/4-10 tap was chucked in the lathe and the gear was held by a special fixture on the toolpost.

On edit: Lube for the worm gear is Fluid Film.

More to come.
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__________________
Bill in sunny Tucson

I believe in gun control.

Gun Control: The ability to consistently hit what you are aiming at.

Weldor by choice, engineer by necessity.

Last edited by arizonian; 03-05-2022 at 10:35 PM.
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  #6  
Old 03-05-2022, 11:09 PM
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arizonian arizonian is offline
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Gearing

Way back when, maybe in the late teens or early twenties, Aermotor discovered that a windmill pump that is back geared will pump water in a lighter wind. I believe that this is what led Aermotor to outsell their competition after only a few years on the market.

The very first thing that physically happened on this build was torch cutting two discs from 3/4" plate, truing them up and them mounting them in a dividing head and gashing the teeth. The decisions prior to the torch included how many teeth on each gear and what was the available gear cutter in my shop. After many searches, sketches (Paper Aided Design), and inventories, one of the cutters needed was already on hand and the other cutter could be ordered.

The Terms (And some math):

Diametrical Pitch (DP) is the number of teeth on a 1" circle AT THE PITCH DIAMETER.

Pitch Diameter (PD) is the diameter of the gear at it's approximate centerline.

To find the outside diameter, add two (2) teeth to the number of teeth (N) and divide by DP. In the case of the bull gear, (46+2) / 8 = 6". In the case of the pinion, (14+2) / 8 = 2". Beautiful! Torch in hand, the blanks were cut.

An early mistake was to not key the two gears together. They were held by together by socket head screws and them keyed later. Now that the pinion cutter is on hand, they will be keyed together before gashing.

The ratio of the pinion to the bull gear 3.286, so ~3-1/4 turns of the sail wheel to the pumping action.

More to come.
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Bill in sunny Tucson

I believe in gun control.

Gun Control: The ability to consistently hit what you are aiming at.

Weldor by choice, engineer by necessity.
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  #7  
Old 03-05-2022, 11:32 PM
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The Tower

Since the pinion gear cutter was not on hand, work commenced on the tower. Fifteen feet was the height chosen for the tower with the wheel centerline no more than another foot. The tower build is basically cutting and drilling holes, general structural construction, so nothing really exciting.

Photos of my sketches do not show the details involved.

More to come.
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Bill in sunny Tucson

I believe in gun control.

Gun Control: The ability to consistently hit what you are aiming at.

Weldor by choice, engineer by necessity.
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  #8  
Old 03-06-2022, 08:05 AM
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arizonian arizonian is offline
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Quote:
Originally Posted by milomilo View Post
I am going to enjoy watching this. Do you intend to pump water with it?
Absolutely! Some kind of recirculating water feature will be built in my front yard after the windmill is up and running.
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Bill in sunny Tucson

I believe in gun control.

Gun Control: The ability to consistently hit what you are aiming at.

Weldor by choice, engineer by necessity.
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  #9  
Old 03-06-2022, 08:42 AM
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arizonian arizonian is offline
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The Motor

While technically not a motor, the gearbox is colloquially referred to as a motor since it directly drives the pump. Many pieces to the motor are still being worked on.

The wheel shaft is off center of the slewing shaft (mast). When the wind picks up to an excess speed, this gives a moment arm or torque to turn motor out of the wind. The job of the tail is to keep the motor in the wind, so there is a self regulating battle between the two. More on that later.

The gearing determines the spacing between the wheel shaft and the bull gears. Once the parts were partially machined, the parts were fixtured and welded together, then dropped onto the mill for final boring. The boring had to be done at this stage since the outside of the motor case will preclude access to the bull gear bore.

The motor case has been started. The snout that will support the wheel will be a mechanical connection to the case. A pilot will be bored to ensure concentricity with the pinion bearings. Snout is positioned in a mockup state.

The exterior of the motor case is a 6" thinwall pipe that has had the tangents flattened on an anvil.

More to come.
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Bill in sunny Tucson

I believe in gun control.

Gun Control: The ability to consistently hit what you are aiming at.

Weldor by choice, engineer by necessity.
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  #10  
Old 03-06-2022, 10:08 AM
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milomilo milomilo is offline
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Too bad you are not closer. I have a stack of windmill 1/2" sucker rod and I think a piston for 2" pipe that would suck the water up. I am sure the piston would need seals. Probably too large for your use though.
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