DrBlackJack21
Acolyte
Like the title said, how did they handle storms? Was it as simple as removing the "blades"? Or did you just disconnect the (driveshaft?) and let them free spin?
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How did historical windmills handle storms?
- Thread starter DrBlackJack21
- Start date
CupofJoe
Myth Weaver
From the non-modern windmills I've seen, the blades are not solid. They are either fabric sails. Or wooden and slotted like a louvre door or blind.
So I would assume that the sails are furled in and that the louvres are feathered [opened] to let the wind through. Windmills in the UK [and I'm assuming elsewhere too] have a tail, vane opposite the blades to keep it pointed in to wind while in use. It does the same in a storm. This is still pretty much what they do today with modern windmills. They turn the heads into wind and feather the bladed to make them ineffective.
It is usually a really bad idea to let a windmill run too fast. The forces involved build up very quickly [1/2 m v2 and all that].
So I would assume that the sails are furled in and that the louvres are feathered [opened] to let the wind through. Windmills in the UK [and I'm assuming elsewhere too] have a tail, vane opposite the blades to keep it pointed in to wind while in use. It does the same in a storm. This is still pretty much what they do today with modern windmills. They turn the heads into wind and feather the bladed to make them ineffective.
It is usually a really bad idea to let a windmill run too fast. The forces involved build up very quickly [1/2 m v2 and all that].
Queshire
Istar
Another thing to consider is how stormy things get. I don't -think- a Dutch windmill has to worry about the same sort of tornadoes that Eustace & Muriel do down in the middle of Nowhere.
The Netherlands--all the North Sea coast--get terrible storms with very high winds. Certainly strong enough to destroy sails and blades on a windmill.
It's a good question, to which I do not know the answer. I can offer an additional consideration, though. Weather prediction was not at all reliable, so there wouldn't have been much time for taking in sails or such like. Moreover, there'd be no way to know whether the wind would blow strongly enough to cause damage.
Disengaging the gears would be quicker, but there had to have been some sort of limit to what even that could bear. I doubt even disengaging the structure could have borne a thousand rpm or whatever. Still another factor: what does the windmill do? Is it pumping water or is it grinding grain or running a stamp mill? There could be situations in which the wind didn't threaten the physical safety of the mill, but would have turned the blades more quickly than was safe for the task at hand. Disengaging gears would have been the way to deal with that, so that might have been what happened well before any truly dangerous winds hit. Just speculating there.
The sails would always be problematic. To be useful they would have to be well-secured, which implies it would have taken some time (hours?) to bring them all down. Might have been better to leave them and just deal with repairs.
Finally, don't forget watermills. They had their own environmental challenges, mainly ice and flood.
It's a good question, to which I do not know the answer. I can offer an additional consideration, though. Weather prediction was not at all reliable, so there wouldn't have been much time for taking in sails or such like. Moreover, there'd be no way to know whether the wind would blow strongly enough to cause damage.
Disengaging the gears would be quicker, but there had to have been some sort of limit to what even that could bear. I doubt even disengaging the structure could have borne a thousand rpm or whatever. Still another factor: what does the windmill do? Is it pumping water or is it grinding grain or running a stamp mill? There could be situations in which the wind didn't threaten the physical safety of the mill, but would have turned the blades more quickly than was safe for the task at hand. Disengaging gears would have been the way to deal with that, so that might have been what happened well before any truly dangerous winds hit. Just speculating there.
The sails would always be problematic. To be useful they would have to be well-secured, which implies it would have taken some time (hours?) to bring them all down. Might have been better to leave them and just deal with repairs.
Finally, don't forget watermills. They had their own environmental challenges, mainly ice and flood.
Mad Swede
Auror
It depends on the exact construction used, but usually you can both disengage the gears inside the mill and change the angle of the sails and blades. In that way you can prevent all but the strongest winds from causing too much damage.
Don Coyote
Scribe
Windmill blades could be locked in place. Blade angles were adjustable. Some systems required the blades be stationary during adjustment. Some could be adjusted while the blades turned. A couple of systems adjusted automatically.
There's no way a windmill owner would use sails that couldn't be adjusted or furled. They needed the ability to adjust blade speed to wind condition and minimize damage from high winds. Never underestimate human ingenuity when it comes to turning a profit.
There's no way a windmill owner would use sails that couldn't be adjusted or furled. They needed the ability to adjust blade speed to wind condition and minimize damage from high winds. Never underestimate human ingenuity when it comes to turning a profit.
Do you have sources for this info? I love these kinds of details.
Thank you for those references, especially the third one, which addresses pre-modern windmills in detail. I was unable to find anything that specifically addressed how to deal with a high gale, at least nothing prior to the 17th century. The best I can gather is that the miller would go outside and move the tail so the vanes sat on edge to the wind. Furling the sails in a high wind can be done, but it'd be perilous. I suppose each miller would have to make his own call on that.
Drainage windmills represent a different sort of socio-economic dilemma. They were typically owned in common, through something like a water district or sewer district. They could command individuals to go out in a storm at the risk of life and limb, but how far could they compel? Room there for a story or two! In any case, once you get up into a high gale (say, force ten), the community has other problems in addition to the fate of the mill.
I very much enjoyed the details in that third essay, such as using the position of the arms to signal, or confirmation that if the mill spun at high enough speed it could set the place on fire. It would be terrifying to be inside the building with gears spinning wildly, the structure groaning under strain, the wind howling.
Anyway, thanks again. That one's going into my link library.
Drainage windmills represent a different sort of socio-economic dilemma. They were typically owned in common, through something like a water district or sewer district. They could command individuals to go out in a storm at the risk of life and limb, but how far could they compel? Room there for a story or two! In any case, once you get up into a high gale (say, force ten), the community has other problems in addition to the fate of the mill.
I very much enjoyed the details in that third essay, such as using the position of the arms to signal, or confirmation that if the mill spun at high enough speed it could set the place on fire. It would be terrifying to be inside the building with gears spinning wildly, the structure groaning under strain, the wind howling.
Anyway, thanks again. That one's going into my link library.
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