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Forum Index : Windmills : MacGyver Furler
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MacGyver Guru  Joined: 12/05/2009 Location: United StatesPosts: 1329 |
When we talk about "furling" a windmill, it means turning the blades out of the direct wind flow. This is done to prevent damage by things spinning too fast. Several things can prompt furling. Higher-than-normal high winds heads the list of course, but things like an open circuit (burnt wire) in an alternator or the chance of magnets taking flight due to centripital force are other considerations prompting us to slow the shaft rpm down. Through the years, many of us (myself included) have built fairly intricate systems to furl the windmill, but it was always too complicated a matter. This is an attempt to level the playing field. What follows is a simple furling method anyone can utilize. The one shown here has about 4 moving parts, but future builds will have only three and be even simpler. I must apologize in advance for the shoddy workmanship; I threw this together more than anything for a "proof of concept" sort of thing. Future builds will show improved construction, but for now here goes: 
This is that same little "test" mill I have flying in my back yard. I merely rebuilt the vertical tail section for this project. The stabilizer rests in a "drag" position 45* to the wind. As the wind speed picks up and goes beyond a preset minimum, the stab rises (against a spring not shown) and the rudder kicks to starboard. 
Here's a closer look. For anyone familiar with R/C gliders, I just added a "full-flying" stab (horizontal stabilizer) to the existing vertical stab (tail) and am using its action in the wind to move a rudder. 
Here's a shot looking down over the top. As the stabilizer moves, it in turn moves linkages that ultimately turn the rudder, turning the mill out of the wind and slowing things down. When the pressure on the bottom of the horizontal stab lessens, a spring returns the rudder to "amid-ships" (center) and the mill points directly upwind again. 
Here's another shot showing the rudder at "zero" as things sit at rest. 
I propped a 1/4" piece of wood between the "stop" peg and the arm of the bell crank to show how much this reacts at the rudder (next picture). 
Just that small amount of movement in the stabilizer kicks the rudder hard enough to turn the mill out of the wind lickety-split! It's too late today to shoot a video (along with no wind) but tomorrow, I'll fly it and stick a video on Youtube and either put a link here (if the edit function works) or put one in a reply. I intend on refining this build and using it on all future "MacGyver" wind projects. Newer versions will have much of the mechanics built within the insides of the vertical stabilizer and only a flexible push-rod sticking out the side, connected to a horn on the rudder. . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
I don't know how well that would work in real life, but its definitely the most amazing thing I have seen all weekend! I look forward to your posts. 
Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| DTMC Newbie  Joined: 12/02/2010 Location: Posts: 11 |
Mac, have you flown this yet? I am curious as to how far (in degrees) this configuration will furl the mill off the wind before the tail stalls or the horizontals become ineffective. Cheers |
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ChrisOlson Regular Member  Joined: 19/01/2010 Location: United StatesPosts: 60 |
That's an interesting concept indeed. My last turbine I built uses the standard furling tail, albeit with the tail hinged in the center of the boom, and controlled by a spring over hydraulic cylinder. This is a photo of that machine on the tower: 
And this is a photo of the tail hinge setup with the tower lowered: 
This is probably the smoothest and most reliable furling mechanism I've built to-date. The internal hydraulic damping in the cylinder allows a minimum stop-to-stop time of 3 seconds, which dampens the forces on the tail in high winds. The cylinder has three different adjustments: "breakaway" - or where it starts to furl, maximum furling pressure (set according to maximum continuous output of the generator), and damping speed (minimum 3 seconds stop-to-stop, maximum 5 seconds). I have flown this setup in 111.8 mph wind recorded by the anemometer on the tower, without shutting the turbine down, with no damage to the machine. The main reason I developed this setup for this turbine is because it is a rear generator unit with a PTO driven generator and the conventional method of hinging the tail on the yaw tube didn't allow enough tail movement to prevent the tail boom from contacting the large rear mounted generator. This is a 13 foot turbine and I experimented with a rudder type system but found that the surface area of the rudder had to be considerably larger than the vertical stabilizer or as soon as it started to yaw the wind pressure on the stationary portion of the tail won out and the machine would not furl. I suspect you'll find the same thing with this design. On small turbines you may be able to get away with this, I don't know. But on larger ones the rotor will develop close to full power in high winds running at 45° to the wind and the power output does not drop appreciably until the rotor is turned 60° from the wind direction, minimum. At 75° to the wind direction, in 100+ mph winds you will still see upwards of 4-5 kW from a 13 foot rotor and the only way to get it to slow down at all is to design the furling system so it will turn a full 90° from the wind direction and keep it there. At that point the tail must provide enough control over the rotor at those wind speeds to keep it from swinging downwind and having a runaway with the rotor running in reverse. -- Chris off-grid in Northern Wisconsin, USA |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Crew To answer the questions so far: No, I have not flown this yet & yes, it'll likely only work for a small-ish windmill. Fortunately, all I build is small stuff, so I suspect it will be fine for me; not sure about the rest of the crew. If there's wind tomorrow, I'll fly it and post a video on youtube. Future builds will see the mechanical stuff housed inside the vertical stabilizer (hidden from view). I will still use a full-flying stab, but the trailing-edge cross-connector rod (which ties the aft end of the stab) will control the bell crank directly. There will be a small horizontal slot near the bottom of the vertical stab which will have the exit horn from the lower portion of the internal bell crank to which will be attached a flexible linkage that is tied ultimately to the control horn on the rudder itself. Since my stuff is all really small, I design it to run at very high speeds and all I'm looking for is a way to fall off the wind "just below" the windmill's red-line limit. I don't think one of my tiny machines would come apart in a hurricane, so like I said, all I want it to do is fall off a bit at or near its top end. I'm also thinking instead of using a spring (which would be subject to corrosion from weather) I'll merely weight the trailing edge of the horizontal stabilizer with a strip of lead and let gravity do the work. This may not work due to any vertical vibration induced by the fact that the stab is constantly trying to dip the nose, but that's just something I'll have to watch for I suppose. I'll update this post as I make changes and find out more about how well (or not) this set-up works. 
Edit: OH, I almost forgot one very important thing. My windmill builds incorporate stops at 180*. What this means is I physically stop the horizontal rotation of the windmill 45* off center each way from the "mean" direction of wind-flow. What this boils down to is my not having to worry about electric wires wrapping around my tower due to the windmill revolving round and round with changing wind direction. It also means if the mean wind source changes up more than 45 degrees either way, my windmill doesn't stay in its direct path. Oh well; can't have everything, right? . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi Mack I like the idea but think you will need to pivot the whole Stabilizer to get enough energy to furl without stalling, also needs a damper on the servo surface to stop flutter that could cause an oscillation to establish in the mechanist. Very interested in hoe it works. All the best Bob Foolin Around |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi Chris I like your damper in the furling, as it slows the action so the gyroscopic s are not so damaging. All the best Bob Foolin Around |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
[Quote=VK4AYQ]I like the idea but think you will need to pivot the whole Stabilizer to get enough energy to furl without stalling . . . Ya know, it's funny you should mention that, because originally I had in mind to set the stab at about 40* "up" and pivot the entire assembly at a gimbal joint or something similar so when the wind got out of hand, it simply tilted the whole head assembly (including the alternator) backwards, spilling the excess wind off the tops of the blades. I did something similar in Florida back in the day, but in that case, the whole tower swung back about five feet, changing the angle of attack. It was fun to watch, but slow and clumsy, so I abandoned the idea. I still might do the tilt-back thing though if this latest approach proves too problematic. In my case, all I need is a small amount of over-speed protection as things approach light speed, since my stuff is very small. I have a set of one-meter blades that are 3" at the root and 2" at the tip, each weighing less than an ounce! They are too much for anything I have built to date, but I have them just in case I need lots of leverage at high speed. Those babies should fly like there's no tomorrow! Unfortunately, they were very difficult to manufacture, so I've settled in on making my plastic blades 4" at the root and 3" at the tip with a length of 24 to 36 inches overall.
My biggest hurdle is there is not very much consistent wind where I live. A mile down the road at the beach, it's a different story altogether, but where I reside, the wind is on and off. . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| ChrisOlson Regular Member Joined: 19/01/2010 Location: United StatesPosts: 60 |
It also causes high peak power spikes when a 80 mph gust front hits in a storm. But I've found that the turbine is more easily able to handle those momentary power spikes than having the rotor suddenly snapped to the side and the tail slammed up against the stop. -- Chris off-grid in Northern Wisconsin, USA |
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Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Hi Mac, The tilt back system has been tried with some success, but from the reports i had read there is one main problem or 2 really. The first is when it tilts back, the mill in normally under load and speed on, the reports say that this causes the mill head to take a orbit or 3 around, as it tilts back and then, #2 it slows and crashes violently back down into the wind again. There has been some very good systems made this way but requires lots of dampners. I just dont like the idea of the mill head taking several orbits around the tower, very stressful on the tower. Pete. Sometimes it just works |
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| ChrisOlson Regular Member Joined: 19/01/2010 Location: United StatesPosts: 60 |
By "horizontal rotation" I assume you mean yaw. I guess I don't understand the yaw stop arrangement here. 45° either side of the wind direction is 90°. If you consider the "mean" wind direction to encompass a 45° sector, then 45° on either side of that adds up to 135°. Or maybe I don't understand what you're saying here. This setup you invented is very cool looking indeed. But I think what you're going to see here is that when you use a passive yaw control system to steer a turbine and try to switch it to active yaw control to furl it, that forces are introduced that you may not be considering. One of those is gyroscopic precession forces. I don't know which way your rotor turns, but judging from the photos it appears that this turbine will furl right view from upwind. If that's the case you need a rotor that turns left (counterclockwise) viewed from upwind so precession forces can assist in furling. The other thing is the tail design. It takes a LOT of rudder area to steer a tail with a stationary vertical stabilizer. The rudder can try to deflect the tail to the side, but as soon as that vertical stabilizer increases its angle of attack it starts making lift, and it won't turn any further than the point where the lift from the rudder balances the lift from the vertical stabilizer. -- Chris off-grid in Northern Wisconsin, USA |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Chris Oops! I meant 90* but didn't think it through when I typed it up. Ben was right; 'Haste makes waste'. At any rate, the prop spins clockwise facing the wind, so I made the linkage kick the rudder pedal to starboard (right-side when facing into the wind flow). I wasn't actually thinking in terms of gyroscopic precession, but my years of flying R/C just kicked in and this "seemed right" to me at the time. Thanks for the science behind it. I think this would be a good place to restate some facts: MacGyver is a plumber NOT an engineer. I like to think of myself as an engineer, but the reality of it is I can't handle the math. Heck, I keep way more money in my checking account than I should just so I can let it balance itself each month! Now everyone knows what we're dealing with here. Just thought I should clear the air a bit. The longer I stare at what I've built, the goofier it looks, but it was fun to think through and build, which is 99% what I'm all about anyway. It's like what I'm up to today. Yesterday I sat on the beach for a couple hours pouring dry sand in front of a large, flat-faced ceramic magnet culling out magnetite to be used in a molded stator build. Today, I'm going to slam together a contraption that will allow me to fill a "hopper" using a bigger shovel than I used yesterday and let the "machine" do all the holding-the-2-pound-magnet stuff. I was in hopes I could walk away from the beach with a 2-gallon bucket full of nearly pure magnetite. Turns out my efforts only got me about half a pound! Back to the furling device: All "I" am after here is to slow the rotor speed down a 'tich' when it reaches it's near-maximum speed. I don't know what that is yet, because I haven't coupled the blades to a working alternator. At this point, I'm merely getting all my little ducks in a row. Thanks for all the comments though. You never really understand all you know about something until you're forced to explain it to someone else. It's only then that you see how goofy you come off to folks. Still, 62 years of bad habits will be tough to change, so stand by for more goofy projects from you-know-who (see avitar)! . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi Mack Goofy or not it dosen't matter as long as you are having fun, it keeps you occupied and out of the wife's way. All the best Bob Foolin Around |
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niall1 Senior Member  Joined: 20/11/2008 Location: IrelandPosts: 331 |
its intersting to see ideas about tilting machines discussed again Mac...i think a machine mounted on a true vertical hinge does bring in the gyroscopic problem in a big way especially if theres no tail offset (or any tail) to counteract the effect my crude go at this a while back with a downwind mill was fraught with problems of rotation on the mast ....sometimes going right around it when it furled high..that in the end was the final nail in the coffin for that machine it was really just a huge gyroscope ...masquerading as a mill ..its intersting thinking about gyro effects in mills ...sort of are there any small issues with the direction off rotation and tail offset ?... sometimes the weird effect off wind seeking in mills comes up...ie. the mill mighnt just furl as good as it should and not protect itself in extreme conditions its interesting thinking about it..... 
ps...your tail reminds me a bit of a tail fin on an old gypsy moth airplane Mac ... that seemed to use air pressure to aid the fin operation a little ...not the same ...but erm kind off the same ... niall |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
[Quote=naill1]. . . to use air pressure to aid the fin operation a little . . . Your mentioning this reminded me of an email I sent Chris Olson this morning after he replied to my post. I asked him if I were to "use air pressure on the leading edge of the vertical fin", would that help in my making a mechanism that turned the whole shebang. Haven't heard back yet, but I thought it funny you mentioning something similar; small world. To operate a full-flying vertical stabilizer, I would necessarily have to manufacture a fly-weight governor attached to the windmill's main shaft, which would in turn shove a lever back and forth controlling the yaw by rotating the entire vertical stabilizer (tail fin) about its point of attachment to the rest of things. After finishing this first build I was reminded that even though "a small rudder turns a mighty ship" -- with a windmill it's not the same. There are no wings on which to reestablish a bench mark and therefore doing this risks the chance of the whole thing spinning round and round like a top. So far today, there's not been enough wind in my back yard to cause my little test mill to furl. 
If and when Mother Nature decides to cooperate with my attempt at 'show-'n-tell' I'll toss up a video on youtube. . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| niall1 Senior Member Joined: 20/11/2008 Location: IrelandPosts: 331 |
just a kind off foot note on the gyro thing..... theres a video on utube off a guy sitting in a swivel chair with his two arms outstretched holding the two ends of an bicycle wheel axle... when the wheel is spun up he starts to rotate around the chair ..fairly strongly at that.. 
i think the catch is his arms arnt steady ...so they move a little up and down as he,s holding the axle... this causes ..i think ...the lateral movement on the chair Dingles was able to explain this effect a lot better.... niall |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Crew The wind finally kicked up to what I thought was enough to operate my little furling idea so I shot a short video. Here's the Latest Video of my attempts at a furling device. Fiddle sticks; it worked so well on paper! . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| ChrisOlson Regular Member Joined: 19/01/2010 Location: United StatesPosts: 60 |
You mentioned something about the horizontal stabilizer being in the "wind shadow" of the blades in your video. I'd like to point out, Al, there is probably no wind shadow behind those blades. It doesn't appear that you're driving anything with it, so the blade are just coasting. In order to slow the wind to create a "wind shadow" you have to extract power from it, which means the rotor has to be loaded. -- Chris off-grid in Northern Wisconsin, USA |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Chrs Perhaps I misspoke (not uncommon for me). What I meant was that the blades, when they are whirring around, present themselves as somewhat of a "wall" standing in the way of wind just gliding through that plane (where the horizontal stab is currently mounted). I've proven to myself this is likely not a viable build, still I'll try it again by moving the horizontal stab down to the hub level and creating a full-length rudder up the back side of the thing just for drills. For anyone wondering why all the goofy projects; I like to try stuff, so even apparent "failures" like this little project keep me happy with something to build. It's a hobby and I try not to get too serious about stuff. . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| ChrisOlson Regular Member Joined: 19/01/2010 Location: United StatesPosts: 60 |
That's unlikely. When the blades aren't loaded they present virtually zero resistance to the wind flowing thru them. I've run 10 foot rotors in my shop with a makeshift arrangement of high speed fans to simulate a 3.5 m/sec wind and when they're not loaded a handheld anemometer shows no difference in front or behind the rotor. Put a load on the generator and there's a significant difference from front to back in the measured wind speed. I have videos of doing this stuff on YouTube: http://www.youtube.com/user/OlsonFarms#p/a/u/1/4YKdmirV2xA -- Chris off-grid in Northern Wisconsin, USA |
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