1/2 Scale "model" windmill

[windybob]

Looks pretty neat!

[Ron Stauffer]

About 5 years ago, I had curiousity on the Aermotor "mathematical" windmill as it was called when introduced. I compared each size by weight, fan blade surface area, HP rating & RPM, basic motor % complete head weights and pumping capability. I found some interesting information worth noting.

The scaling of the windmills wasn't linear because of the fan blade surface area. The jump from a 8 to 10 wasn't 25% greater but was 56% greater fan surface area and a complete head weight of 83% more. The change wasnt uniform between mill sizes as I comparted all sizes 6' to 16'.

The back gearing ratio varied between from 3.3 to 3.5 to 1. The variance I think was from fitting a certain number of evenly spaced teeth on the circumference of a given diameter.

The numbers on the pumping capacity charts for different sizes was more linear than anything else. I found the numbers to me somewhat suspect.

The ratio of "basic motor" weight to "complete head" weight was very consistent averaging 48% throughout the sizes. This makes sense to have a head that is well balanced.

Fan surface area or swept area wasnt a be all to pumping capacity. A university study (NMSU I think) compared the 18 blade 8" Aermotor to the 15 blade Dempster and found negligible difference. Roller bearings may compensate for 3 blades?

The design of the Aermotor seems to pivot off of the 8'. When they scaled for the other sizes and used different sizes and weights of materials, there are weaknesses/failures that are specific to a size. Design engineers for the time didnt have the tools and resources to account for everything.



Since you plan to "use" this scaled model, you may want to consider the variable of wheel RPM. A 16' turns at 53 RPM, an 8" at 105 and a 6' at 125. A 6" turns fast and is prone to self destruct. Big mil bearings and shafts last longer because of slower RPM. A 4' will be faster yet and with scaled down fan fasteners...

Ron Stauffer
Montrose CO

[mtblah]

INTERESTING , thanks Ron for sharing knowledge !
Mike B

[arizonian]

Decided to add machining pads to the motor housing while it was on the mill. Little brother has a 120V mig at the machine shop.

Facing and boring the backside and making use of the machining pads.

The housing is a little more catywampus than I would have liked. You won't notice it 15 feet in the air, tho.

I meant to mention this earlier. When Oilite sleeve bearings get hot or get spun on a lathe, they lose their oil. I'll have to extract them and soak them in warm oil before the motor goes together.

More to come.

[arizonian]

About 5 years ago, I had curiousity on the Aermotor "mathematical" windmill as it was called when introduced. I compared each size by weight, fan blade surface area, HP rating & RPM, basic motor % complete head weights and pumping capability. I found some interesting information worth noting.

The scaling of the windmills wasn't linear because of the fan blade surface area. The jump from a 8 to 10 wasn't 25% greater but was 56% greater fan surface area and a complete head weight of 83% more. The change wasnt uniform between mill sizes as I comparted all sizes 6' to 16'.

The back gearing ratio varied between from 3.3 to 3.5 to 1. The variance I think was from fitting a certain number of evenly spaced teeth on the circumference of a given diameter.

The numbers on the pumping capacity charts for different sizes was more linear than anything else. I found the numbers to me somewhat suspect.

The ratio of "basic motor" weight to "complete head" weight was very consistent averaging 48% throughout the sizes. This makes sense to have a head that is well balanced.

Fan surface area or swept area wasnt a be all to pumping capacity. A university study (NMSU I think) compared the 18 blade 8" Aermotor to the 15 blade Dempster and found negligible difference. Roller bearings may compensate for 3 blades?

The design of the Aermotor seems to pivot off of the 8'. When they scaled for the other sizes and used different sizes and weights of materials, there are weaknesses/failures that are specific to a size. Design engineers for the time didnt have the tools and resources to account for everything.

Since you plan to "use" this scaled model, you may want to consider the variable of wheel RPM. A 16' turns at 53 RPM, an 8" at 105 and a 6' at 125. A 6" turns fast and is prone to self destruct. Big mil bearings and shafts last longer because of slower RPM. A 4' will be faster yet and with scaled down fan fasteners...

Ron Stauffer
Montrose CO

Thanks for the info, Ron.

I am aware the a smaller wheel will turn faster. In fact, I was counting on it. I have not completed an analysis of all the factors for this first windmill. Once it is up and running, I may do an analysis before I dive into the next project. I did notice looking at various websites that at one time a 6 footer was back geared in the ~4.10-4.30 region, exact memory escapes me right now. That information was much too late as I had decided on the 3.28 (46/14) ratio and had cut one gear already and the gear parameters and centers were set in steel.

I need to set my sights on Phoenix and have a talk/visit with Jeff (rockingjl).

The start of this project was like having a conversation with a non-welder about welding. Bright light, heat and flames, sparks flying, how hard can it be? Until you get dirty, you have no idea how hard it can be.

[Ron Stauffer]

I have an upcoming trip to AZ and will be stopping at Jeff's. I come down and do work even farther south than you - Rio Rico and Southeast - Wilcox but I don't think I will be down that far on this trip

Ron Stauffer
Montrose CO

[arizonian]

I have an upcoming trip to AZ and will be stopping at Jeff's. I come down and do work even farther south than you - Rio Rico and Southeast - Wilcox but I don't think I will be down that far on this trip

Ron Stauffer
Montrose CO

I'm very familiar with Montrose. I lived in Grand Junction for 3-1/2 years and travelled to Ouray quite frequently back in the late seventies. Haven't been up that direction for a few years now. I probably wouldn't recognize anything now.

[arizonian]

Housing flipped over, faced, dialing in the shaft bore, bore complete.

Snout for the wheel support. Forgot to add thickness for the shoulder which will pilot into the bore of the motor housing. Chucked it into the weld positioner and added a bit of material. I jiggled and left a rough spot but the shoulder itself will clean up.

[arizonian]

Beginning to look like something.

A few parts.

A partial mock up.

Still a long way to go.

[arizonian]

Met with Jeff today. It was a very enlightening and worthwhile trip. Thanks, Jeff!