Wind energy - Drinking straw furling wind turbine

I have to admit to being a little surprised when this one worked.

Here is my fully functional wind turbine made from three flexible drinking straws, three pins, a small piece of paper, and some tape.

The only tools required were a small pair of scissors, and the entire wealth of human knowledge as provided by the Internet.

Thanks entire wealth of human knowledge as provided by the Internet.

Thanks small scissors.

I started with the blades. Its probably easiest to see how these are made by looking at this previous post on blade twist.

Pictured here is the basic shape we are aiming for. On the drinking straw version, it will be a long thin version of this triangle looking thing drawn here.

In the cardboard version, the halves are connected by the thin, square, sticking out bit on the bottom LEFT, so the triangle bits on the top left become the leading edge of the blade. This one would rotate anticlockwise if the wind came from under the green thing in the background.

Bottom right tip goes up. Bottom left square bit is the centre.

The drinking straw version should look something like this. Its hard to see, but each blade has the same shape as the cardboard version. The straight sides (bottom on the cardboard picture) almost line up with each other.

The drinking straw version will also be made with two blades connected at the middle so there is no need to cut the straw in half. Just cut the required shape from a single straw. This means the blades will line up perfectly because both are made in one piece. Keep a small section of whole straw in the centre to aid in keeping the axle in place.

Jam a pin through the centre to act as an axle.

Now make a tail.

The only important thing here is to get the angle of the pin at around 20 degrees.

Don't be too fussy because its very easy to make a new pinhole.

You will need to adjust this a few times unless you are lucky.

Then make one of whatever you might call this.

The straw that goes out to the far right is to stop the tail swinging back too far (adjustable with bendy bit)

The bit that points up in the centre is the section that holds the tail pin. (also adjustable so you can play with that 20 degree angle a bit to see what changing it will do)

The bit that points diagonally up and to the left holds the turbine.

The device pictured above might be better explained by looking at a previous post where I described making the furling model.

Pictured left, is the design version of the three straw and tape thing pictured above. [I just noticed it's facing the opposite way just to be irritating]

On each of the three pins, you need to make a bearing to keep the pins from wobbling.

Just fold a section of straw in half lengthways, and stuff it into the straw where the pin needs to go.

This just makes the hole smaller.

One for the turbine (pictured), the tail mount, and the pivot point for the entire contraption to mount it to the straw we will use as the pole.


Next stick a folded straw bearing into a full length drinking straw. That's your pole. Stick everything else onto the pole, and it's done.

There are at least four points of adjustment that will let you learn some stuff.

1. The tail pin's angle. Making it slope more will make it furl later in stronger winds. Less,earlier in lighter winds. Adjust by changing the pin and/or the straw that the pin sits in (bendy bit)

2. The pivot point offset (the bottom most picture). Adjust it's position so that some balance is achieved between the blades desire to fold, and the tails desire to keep everything pointed into the wind. Shift it around randomly until it works. Mine worked best at the extreme left. If it still doesn't work try changing the weight of the tail.

3. Adjusting the weight/length/area of the tail can change when the device furls.

4. The tail stop point (bendy bit) that stops the tail from going back too far when its in the NOT furled position.

Remember if a bit doesn't work, it only take a few minutes to make a replacement part. I might have been lucky with my blades, but everything worked well enough to adjust some bits to get it right.

It might even be worth making a few different blades to see what they do.

Test with a fan, the wind, or even a brisk walk. Yes, you will look silly if you mount your wind turbine on a hat, but it's a small price to pay for knowledge.

Wind energy - Making the furling model

I'm not sure showing the results, and then the "making the furling model" is really best practice, but I got a bit excited when I made the thing and it actually worked, so I posted the result first.

I tend to strive for 2nd best practice anyway, so it's all good. Here is what I did.


First up I cut some blades out of a 30cm cardboard clingwrap tube.

I used about a quarter of a tube for each blade.

I made the first cut straight along the tube, and the next cut from a quarter of the tube away. Cut to one centimetre away from the first cut at the tip.

That's not so clear. If they look a bit like the picture they will probably work. I wasn't too fussy with angles and things because this wont matter if it falls to bits.

I'd be fussy with the real thing, because vibration will be an issue.

Next I delicately removed some excess bits of an old computer chip fan (I used a hammer and a screwdriver), so that I could mount the blades on it and use it as a bearing. It would have been possible to even generate a small amount of electricity if this fan wasn't broken.

It turns out, many electric motors will produce electricity if you rotate them.

And then a drop of super glue to mount the blades in place.

In this case, my blades will be rotating clockwise.

As mentioned in a previous post on blade twist, the leading edge bits that sticks out from the centre line  in the middle of the blades, are there because we want a steep angle of attack, and a fatter blade profile at the centre. This is because a given spot near the centre moves slower than a given spot at the tip.

I cut a tail out of cardboard, and screwed it onto a stick. The total tail length should be around the length of one of your blades.

From what I've read, the tail area should be somewhere around 15% of the swept area of the blades.

So 16% of pi X (blade length X blade length)

But I just cut something that looked about right.

I drilled a hole through the stick so it wouldn't split when I put a nail through it. The nail will be the pivot point for the tail.

The nail goes through on an angle of around 20 deg, so that the bottom points away from the tail.

Like this, as seen in the first post on this genius system of furling.











Now all we need to do is make a base plate with a few holes drilled in it to mount everything on.



It should look like this.

But instead of a pipe set at an angle I just drilled a hole at an angle through some wood.

Mine looked like this with the computer chip fan bearing mounted.












To create the angles required, and to make your tail do the right thing as described in the post called genius furling, there are a few angles and dimensions to get right.

- Picture a square (black)
-mark out a 50 deg angle (green)
-and weld a pipe on a 20 deg angle (yellow), pointing back along the line made by the 50 deg angle.
This creates an offset between the turbine and the tail.
-this offset (blue) should be around 5% of the length of one blade.




What all this does, is makes your tail and the offset blades try to meet in strong winds because the tail is always trying to point down wind. This means the blades turn away from the wind, thus protecting them from spinning too fast and either burning out all your wiring, or total catastrophic destruction of everything. The weight of the tail resists this meeting, because it has to move up if its to move to the side, due to the 20 deg angle. Adjusting the weight of the tail adjusts the wind speed required to furl the system.

Ingenious. (and sadly not my idea)

It's described better in the post I called genius furling.

Here is a video showing the test turbine working. This video shows the angles a bit better than the last as I attached a drinking straw pointing straight back at 90 deg to the blades. Especially in the last few seconds of the video, the straw shows the angle of the turbine in relation to the tail as the wind speed changes (using a fan). The wind direction stays the same throughout the video.

Wind energy - Genius furling

I'm not even sure I can convey this one. Its simple, it's genius, and even knowing how it works makes it no less difficult to explain.

To quote me quoting an ancient rocker "There aint 'alf been some clever bastards."

This method of furling requires no springs, is very reliable, and by all accounts works a treat.
It furls the turbine by lifting the vane upwards, towards the wind if the wind is too strong. I like it already.

Whoever came up with this was, without question, a genius.

First we start with a pole to mount everything on.

Then we make one of these.

Its basically a sleeve welded at an angle to a plate.

We attach this thing to the top of the pole via a bearing so it can spin around freely.

This is what we will now stick our turbine and wind vane to.



Note that the sleeve is on an angle. It's very important.

Side view

Next we build a wind vane so that it has a shaft set at such an angle that when we set it into the angled sleeve in the fist picture, it sits flat to the horizon as in the picture to the left.

Side view

Then we stick the two bits together by slotting the shaft into the sleeve and attach our turbine.

Note that the turbine and the vane are off centre on either side of the pole.

This offset is also very important

Top view

When the wind blows onto the turbine, the force is one that tries to pivot the turbine around the pole and to the left.

Because the vane is always blown downwind, there is a tendency that the two try to meet.

The stronger the wind, the stronger this tendency.

This is a good thing because we want the blades to point away from the wind a bit as the wind gets too strong. Auto furling is the desired outcome after all.

But the reason they don't just give in to their desire to meet is the clever bit.

The reason they don't meet is to do with the angle of the sleeve on the pole cap. In order for the tail to swing to the right, it also has to move up because of the angle of the sleeve. This means that the weight of the tail sets the tension rather than some kind of spring. The weight of the tail resists the tendency to arc up and to the right. By setting the weight of the tail, we determine at which wind speed the device starts to furl. Gravity is very reliable. Things like springs, not so reliable.

Remember, throughout this thing adjusting itself, and setting how much of the turbine is presenting to the wind, the device is still tracking the wind. The vane still does its job and continues to follow where ever the whim of the wind takes it. When I talk of the vane arcing up and to the right, it's only moving to the right relative to the turbine. It's following the wind, always pointing downwind, and is taking the turbine with it. 

Relative to the universe everything rotates together on the pole as the device tracks the wind, as decided by the vane.

Relative to the wind, the turbine is presented at a different angle depending on the wind speed.

The tail still serves as a vane and maintains the turbines aspect into the wind, but it folds a little as the wind gets too strong.

Front view

In slow winds it looks like any normal wind turbine. It tracks the wind and keeps the turbine pointed directly into the wind to extract the most energy from the available light winds.

Side view

The vane is in its maximum straight position and is sitting flat to the horizon.

Flatish in my diagram.

Front view

When the wind becomes a little too strong we want to turn the turbine slightly away from the wind to collect a little less power. This way we still get energy from the wind but we reduce just how much we collect. After all, there is now a bit too much energy in the wind, so we shouldn't be greedy and risk damage to our turbine.

The vane still points downwind, but it has folded toward the turbine... or the turbine has folded toward the vane, depending on how you look at it.




The vane has also lifted a little. It's weight is now coming into play. As the vane rotates toward the turbine it also has to rise up as a result of the angle of the sleeve, and the shaft that sits within it that's attached to the vane.

Looking down

The stronger the wind, the more the vane and the turbine try to meet by folding together, but the weight of the vane is trying to settle them back to the straight into the wind configuration. The weight of the tail is in a constant struggle with the wind.

The weight of the vane wants straight, the wind wants folded.

front / side view

Viewed from the side we see this more clearly.

Remember the wind is coming from the left and meeting the auto adjusted blade at a 45 degree angle at this particular wind strength. The vane is pointing downwind but we can see the wind strength has overcome the vane's weight.

If the vane were to move down like gravity wants it to, it can do so, but it will stay down wind. Due to the angle of the sleeve, it must also turn the turbine back into the wind. It can only do that if the wind slows down a bit.

Front view

Eventually, if the wind gets strong enough, the device turns the turbine 99.9 % out of the wind.

If all the constructed angles are correct on the sleeve and the vane shaft, we should see our turbine still generating electricity, or doing whatever it's supposed to be doing, regardless of  the wind strength. If it's all designed properly it should be safe without having to lock it all down in a gale to protect it from burning out the generator, or spinning so fast that the whole thing breaks apart and scatters it's bits to the horizon.

Those angles are really important. I don't know what they should be yet. But I'm pretty sure they would have to be spot on to furl at the correct wind speed, and unfurl at the other correct wind speed.  Given the correct wind speeds would be different for different wind turbines, There is a reasonable chance the angles of the sleeve might need to be designed to suit. It's also possible that one angle fits all.

I'll find out before I start building one.

I'll even let you know.

Side view

This is what we would see in a gale if we looked from the side. The turbine has turned almost directly out of the wind, and the vane is still trailing downwind, but is standing high. When the wind subsides a bit, the vane drops a little, turning the turbine to present a little more of itself  to the weather.


What all this enables us to do is create a turbine that can work in lower winds, but that can still survive  higher winds. We could just make a wind turbine so it was safe from high winds by fixing the vane so it presented the blades almost side on to the wind, as in the last picture, but that would not catch enough wind to be of any use in light winds.

It seems wind turbine design is always a compromise between getting the most out of light winds, and still being upright to cash in on those times when the winds are strong. This automatic furling mechanism goes some way towards having the best of both worlds.

From what I've read so far, this looks like the furling method I would employ.

Wind energy - Vane furling

Vane furling may well not mean anything.

Another method (see previous post) of furling is to allow your vane to collapse a bit. I'm calling it vane furling. There is at least a 50 50 chance that I'm calling it that because that's what it's called, but the other 50 is because I'm studying too fast and not taking good enough notes. You be the judge.

It doesn't matter.

The vane on a wind turbine will always point directly downwind, and the fact that it's connected to the wind turbine at a 90 degree angle will make the turbine point directly into the wind.

 If we make the connection less rigid, we can use its floopyness to our advantage.

Floopyness and furling are virtually synonymous.

At least in my reference books they are, but someone named Robbo taught me to edit mine many years ago, so there may be discrepancies.

With vane furling, we once again see the windmill pointing directly into the wind when we have normal weather. As wind direction changes, the entire device pivots around in such a way as to always present the blades directly into the wind.

No surprises there.

It gets more interesting in rougher weather.

The floopyness is in the spring hinge that we employ. We can do this on a small scale by simply buying a sprung hinge, like the hinge you might find on a kitchen cupboard, if your kitchen is newer than mine. We could even use the kind that makes some cupboards stick open when they get to their limit. In a crazy storm, you might be better off not having your little windmill wanging around chasing the vagaries of a storm. It might be better if the little thing just packed up for the time being until it's human decided it was ok to come back out to play.

On a larger scale we might need to attach a spring to a gate hinge or similar. I'm not sure if there are sprung gate hinges, but if it turns out that I need to make one, I'm confident it wont be too hard.

The important thing is that, once the wind picks up to a point where you get a bit worried about your equipment, the hinge starts to give a little so that your blades don't present themselves quite so perfectly to the wind.

As the wind increases, we see the vane fold more. It still trails directly away from the wind, but the sprung hinge struggles more and more to keep the blade pointed into the wind, so at some stage it gives up trying and surrenders to the whim of the wind.

Even in the strongest winds, the device is protected. It also maintains a reasonably consitant speed. The more wind, the more it turns away from the wind. If the wind drops off a bit, the device turns the blades back to collect more wind, but while the wind is too strong, the wind turbine is safely pointed away from the extreme weather.

This means your wind turbine can to some degree be self governing. If everything is adjusted correctly, and you live in perfect land, you should be able to make your windmill rotate at the same speed regardless of the wind speed, as long as there is enough to get the thing spinning in the first place. But at your address, there always is. If you live in perfect land.

Unlike in the universe depicted in the previous post, the wind in this universe doesn't create ever bigger arrows as it's bluster increases. It creates the same size arrows, they just have more power on the inside. If you are already confused by everything that came before this paragraph, you can safely ignore this one without fear of missing out on anything of importance. In fact, if I were you, I'd go back to the beginning of this paragraph, and simply skip over it.

To this bit.

Wind energy - Tilt furling

I always thought tilt had something to do with pinball. But it turns out its a method of furling.

The tilt back method of furling involves mounting all your kit in a straight line on a plank. Turbine, generator, vane and whatever else you feel like sticking up a pole.

Once it's all mounted on a plank, all you have to do is hinge it with a springy hinge, and hope.

In light wind, the device will point itself into the wind, and generally go about being a windmill.

In the event of winds that might make the generator spin too fast, or that could endanger the turbine, the pressure pushing against the turbine overcomes the spring on the hinge, and the device tilts back.

This tilting does at least two things I can think of. It  makes it so that less surface area is exposed to the wind, and it makes it so that the blades don't get presented to the wind in a very favourable aspect. That is, the blades are at the wrong angle to the wind to be at their most efficient.

In the event of dangerously high winds, the tilt mechanism leans everything back so far, that the blades are almost side-on to the wind.

If all goes well, and no gigantic arrows hit it, your windmill lives to see another storm.

Wind energy - Wind vane

A wind vane is a simple but clever device employed to passively point something in a desired direction relative to the wind.

They work like a flag. Always trailing away from where they are fixed, being carried with the wind.

If we make a rigid flag, it's a wind vane.

If we stick something to the front edge of the wind vane, (where the flagpole is if it was still a flag) we can make that thing face the wind. So for instance if we nailed a sign to the front edge at 90 degrees, the wind would be able to read it.

Rather than a sign, we can stick a wind turbine on to face the wind.

Anything you stick out in the wind wants to act a bit like a wind vane.

Even our windmill blades.

Without the wind vane, the windmill would act like a wind vane itself and would probably loose its sense of direction.

By placing our wind vane at the end of a long pole, we gain a mechanical advantage. Leverage in this case. What that means is a little wind vane at the end of a long stick can overcome the wind's attempt to ruin everything. The little vane at the end of a long stick can stay downwind even though the big windmill wants to be downwind as well.

As long as the entire contraption can rotate freely on the pole that keeps it all up in the air, it will always point the windmill directly into the wind. If the wind changes direction, the windmill rotates and always points the turbine correctly.

I love it when people invent things that use the force they are trying to counter against itself. I realize this is a pretty simple invention, but it was still very clever of whoever thought of it in the first place.

"I wish the wind would stop blowing my windmill out of the wind. I know, I'll just use the wind to point my windmill into the wind."

That's good brain using.

So now we have a better method of making our wind turbine track the wind without having to run outside and re-point our windmills into the wind every time the wind changes direction (the Dutch were a big fan of the running outside method in their early designs). What we need now is a way to point it out of the wind when there is too much of the stuff, without having to run outside. (the Dutch did a lot of running outside to save their windmills from too much wind by furling their windmills.) (actually I think the Dutch windmill operators were live-in like a light house keeper, so they probably didn't go outside so much. They probably just adjusted everything from inside - but I'm pretty sure there was a lot of running around, and constant attention and vigilance involved)

What we need is a method of automatic furling.

Wind energy - Furling

One of the problems with windmills is the wind. Too much of it can turn a DIY windmill rapidly back into the junk from whence it came.

Wind is the enemy of the windmill. Who'd have thought it. When there is too much wind one of several things can happen depending on the application. You can generate too much electricity and over cook your batteries, you can pump too much water and all your cows get bloated or something, you can grind so much flour that you feel a bit like a magician's apprentice with all the bucket work you find yourself having to do, or the whole shebang can just blow over and come crashing down on your neighbour's chicken coop causing an unnecessary spike in insurance premiums.

"But humans have opposable thumbs, the Apollo missions, monorails, trans fats, canned cheese, and Oprah, so surely we have a solution." I hear you exclaim.

And, luckily for me, it seems we do.

The solution is furling.

Generally speaking, "furling" describes turning your windmill away from the wind when the wind gets too strong.

If my memory of my grade 4 project serves me, rather than furling their windmills, historically the Dutch used cloth sails over the wooden frames of their windmill blades. If there was a storm, the sails could be adjusted or in the worst case would just blow out and no damage would be done to the main structure of the windmill. The sails could be adjusted in varying winds to maintain a reasonably constant speed of the grinding wheel or pump.

So, short of the old Dutch option of risking partial destruction, it seems there are a few other methods of furling we might employ to automatically regulate a windmill when it's humans are absent. 


I'll cover them each in detail at some stage. Some of them are particularly clever. 


In fact, I've turned fractionally greener than my regular shade of envy as a result of learning just how clever the simple solutions that these inventors have found really are.