Fairbanks Morse windmill. How does that design work?

[Tom]

You know the one - next to the water tank on the prairie, creaking away. What got me to wondering was as I crested Crawford Road the other day through my watering and tunnel vision eyes I see a modern house-sized power generating windmill just going nuts up there and it immediately puzzled the hell out of me never having thought about it before. The puzzling thing is that directional vane is perpendicular to the axis the power vanes rotate around and thus perpendicular to the wind and isn't set up like a weather vane like you'd expect. So I look online and see that the directional vane is really a governor - when the wind pushes too hard on it the vane feathers the entire rig out of the wind some, or entirely if it's really blowing.

OK, but how does the device orient itself into the wind in the first place, then? I have some theory that I can't back up with anything I remember from physics that somehow the thing has to face into the wind to even out the forces on it but then that gets all screwed up with the vane and I get confused and angry.

Anybody know how this works?

[Noteddy]

Well, as nearly as I can recall from the dark recesses of youth...

There is a lot more going on than appears. Do a google patent search on windmill governor and you will see it was as prolific a source of innovation as clipless pedals.

There were two types of controls. You are right in assuming that the "tail" trails behind the turbine when in normal operation. When things go too fast, a counter weighted governor would feather the turbine in some way or other. Some cranked the tail to the side, putting the turbine oblique to the wind. Others changed the pitch of the blades.

Windmill weights are apparently collectables now.

The other mechanism was a float-control that prevented the water tank from overfilling. When the float rose, the governor was engaged slowing and stopping the pump, or the turbine and pump were disengaged from each other.

The one we used when I was a wee lad, also had a manual way to disengage a clutch and let the turbine freewheel to protect the wear-prone parts-e.g. The pump.

I don't miss carrying buckets of well water to the house. But, I do miss how it tasted.

[christian]

There were two types of controls. You are right in assuming that the "tail" trails behind the turbine when in normal operation. When things go too fast, a counter weighted governor would feather the turbine in some way or other. Some cranked the tail to the side, putting the turbine oblique to the wind. Others changed the pitch of the blades.

The first one sounds basically like a governor in a hit-n-miss engine. Which makes sense when you think of the manufacturer, no?

[Tom]

...You are right in assuming that the "tail" trails behind the turbine when in normal operation. When things go too fast, a counter weighted governor would feather the turbine in some way or other. Some cranked the tail to the side, putting the turbine oblique to the wind...

In this case the turbine was facing directly into the wind, the tail was parallel to the plane of the turbine and perpendicular to the wind direction. It was blowing pretty hard and the turbine was cranking.

[Noteddy]

In this case the turbine was facing directly into the wind, the tail was parallel to the plane of the turbine and perpendicular to the wind direction. It was blowing pretty hard and the turbine was cranking.

Sounds like you saw one oriented something like this:


If the wind is blowing hard, and the pump is disengaged, the turbine can freewheel and will still continue to turn, just not generate as much power. And, it's possible it was not functioning according to spec. Might need to plug in the Di2 diagnostic box. In theory, as the wind speed decreases, and load increases,the tail rotates to be in line with the turbine axle, like this:


You've exhausted my knowledge/remembery. There is/was an amazing variety of mechanisms. The examples here are Aeromotors, which dominated the market by the 1930's. Stop and look next time and let us know what you discover.

I don't recommend climbing a windmill in Sidi's though. One reason Aeromotor dominated was that their oil-bath mechanisms were low maintenance and fewer farmers fell to their deaths oiling them.

[Noteddy]

The first one sounds basically like a governor in a hit-n-miss engine. Which makes sense when you think of the manufacturer, no?

Exactly what I was thinking as I looked through the patent drawings. It always surprised me that early steam/gas engines had such refined governors. But, the governor designs were stolen from windmills which predated them by as much as a century.

Just like bike tech, there is very little new under the sun.

[Tom]

That makes sense. I ride up that road at least every couple of weeks and that house has had a shingle for a local wind power company out front most of the summer, the tower went up a while back but this is the first I've seen a turbine up there. The system might not have yet been completed so it was just spinning. I'll have to go up there this Saturday and check.