Making the wooden turbine blades is proving to be more of a intellectual problem rather than a skill problem. At least so far.
I cut my 2400mm length of 42mm by 11mm pine into lengths I could stack as per the plan in the post called wooden blades. The longest section was cut to 1200mm, then 700mm, 350mm, and the last length was 150mm. I chose these numbers because of some vague image in my head of what it should look like.
I lined them up and drilled a centre hole to fit a bolt I had.
this way I can rotate the stack into position knowing that at least one point is lined up.
Next up was to glue them and line them up so that they were in a rotated stack. Each progressively shorter section was stacked on top of the others with enough rotation to line up the stacks edge with the new items half way point.
After doing this I started to question exactly why I was doing this. My plan had started to evaporate in my head.
I have design doubt.
I cant figure out which side I think is the front, and which way I think this thing will spin.
The only thing left to do was to attach as many clamps I could find and stop thinking about it until it's dry.
Watching glue drying is even less fun than watching paint dry, because you cant even see it.
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.
Wood might be a pretty good substance to make some turbine blades from.
Unlike me, it's strong, light, flexible, and easy to work with.
It can also be shaped with a few tools that I already own. I also have a bit of experience with shaping wood from an earlier "thing" from my 120 things in 20 years.
Pictured here is a wooden lure body from a previous post on getting the most out of your printer by making hand made fishing lures with it. It even has the wing shape that I'll need as the profile for my turbine blade.
But enough self promotion...
By stacking a few different bits of wood together, it should be possible to give a turbine blade shape a bit of a head start.
We want an angled up, thicker wing shape in the centre, and a thinner, flatter wing shape at the tip.
Because the middle bit is moving slower that the tip, we need a bi-plane wing in the middle, and a jet wing at the tip, and everything else in between.
Then we should be able to cut away the bits that don't look like a turbine blade, giving us a nice curve that looks a bit like a propeller.
And then shape the blade into that progressively thinner and flatter wing shape.
If we start by making cuts that join the dots so we cut from "A" to "B", we should get the angles roughly correct.
Then it should be a simple matter to round off the front edge (thick green smudge) in such a way as to make the front round, and the thickest point of the turbine 1/3 back from the front. So a line running the length of the blade running through point "C" would be the thickest bit.
With the guide points created by the corners made by the different heights of wood, there might even be a chance that I can make a second blade that looks a bit like the first. It needs to be very close to exact, so I might need a little luck, or some brand new skills.
That's the theory. I'll give it a go, and see what happens.
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.
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.
I made a model to show myself how clever that furling system I described in a previous post really is, so I'll share some video. The video looks a little boring, but that's just as it should be. The entire point of furling is to make everything less exciting. Exciting tends to lean toward total destruction, and boring, toward surviving storms. (This furling method isn't my idea or anything. In fact, the more I study, the more I doubt I'll be able to contribute anything new to this field.)
The point I attempt to illustrate here is that regardless of wind speed, the blades don't spin out of control.
Adjustment is made to the mechanism by adding weights to the tail, but I added weights all over the place in an attempt to stop my poorly balanced blades from shaking themselves to bits.
It's difficult to capture the way this thing works, but it does. Even with the tail bending, and the entire contraption wobbling all over the shop. I hope this makes this genius method of furling a bit clearer, or at least proves that it works.
I'll talk about how I built this next, but I just had to post the fact that it worked first.
I figure, if I want to understand coils, I need some kind of consistency in a test device.
One of the biggest issues in backyard science, is all the noise that comes with the data. This noise is often caused by changing too many things at once, or there being to many variables. If we change more than one thing, it can become impossible to determine which change brought about the different result. This can lead us to wacky habits, superstitions, or carrying baggage left over from some meaningless bit of the last test we did.
One change, one test.
Noise can also come in the form of sloppy engineering. If your race car is held together with tape, the last very slow lap on those new tyres might be caused, not by the tires, but by the fact that your gearbox fell off.
With that in mind, I thought I should make something a bit more robust than my previous device.
I made this out of, you guessed it, PVC.
I also discovered my rare earth (neodymium) magnets will stick nicely to a nut. These are the same magnets reputed to hold together with 7kg of force required to separate them.
They really are amazingly strong.
Add a bearing and a lock nut, and the neodymium magnet rotatey bit is done.
I'm never sure what tech the universe is aware of, so I'll err on the side of caution and mention locknuts.
If you get two nuts on a threaded shaft, and tighten them toward each other you can "lock" them into position on the shaft. They will no longer spin on the shaft until such a time as you release the pressure between them. They will spin with the shaft allowing us to rotate our magnets by placing them on the nuts.
It seems, that a large plastic hose fitting has a tapered section to grip the hose. This creates a pretty good seat for a bearing.
Placing the shaft into place, then tightening the plastic "nut" presses the bearing firmly into its seat.
Giving us a nice reliable coil jig to test different wire thicknesses, and different numbers of turns on our coils.
Shown here with a wacky experimental coil that did nothing, the only thing left to do is force a flexible plastic tube over the end of the threaded shaft, and stick the other end into a power drill's chuck.
The drill should give us consistent revolutions per minute to keep our test at least a bit scientific.
I was taking some photo's of my fish, and thinking of doing a post on their growth rate over the last 6 months, when I noticed the way they absorb a feed pellet.
It is quite interesting.
For some time now, as the fish have become bigger, I've been hearing a violent "thuck" sound as the fish take feed pellets off the surface of the water.
I was never sure if it was their tails simply making a splash, or something else.
But this seems to indicate they might be sucking in a stack of water with the pellet.
What ever is going on, it's making me think it might be worth revisiting with a better camera.
This series of shots spanned just 1/5 of a second.
I've been working hard at making more electrons do their thing.
But it's not working.
I'm not sure why.
I made some nice coils out of the coil I made before. I unravelled it and thought I should try to explore the relationship between the number of turns on my coil, and what I see on my multimeter.
I started by making a cardboard tube coil winder. I figured it would be best to at least have the size of the coil consistent. I found a few different designs to make a coil winder and all the good ones shared a few points.
The most important aspect to a coil maker is that you should be able to dismantle it a bit to let the coil out.
This looks pretty dismantleable to me. In fact it's trying to dismantle itself just because I'm looking at it.
The object here is to create a frame to coil the wire in so that it stays nice and neat.
If you put a little space under the disks, it should be possible to add some tape before we start winding the coil to hold it together even better. At least that's what those well designed coil makers have.
So if we poke something through from the back, we should be able to stick the tape onto it to allow us to draw it through.
This gives us a bed of sticky side up tape to lay the coil over.
Once it's through, you can hold the tape and the device in your left hand and add coils of wire with your right hand.
When you have added the desired number of coils you can mess about in such a was as to fold the tape over the coil before you dismantle the device.
The plan here is to avoid this.
Its best to work with a real friend, unlike the imaginary one I retain.
Thanks for nothing Ted.
Oddly enough, it all seemed to work pretty well.
I successfully made three neat and well formed coils.
One each of 25 turns, 50 turns, and 100 turns.
That is, it worked quite well until the making the electricity bit.
That bit didn't go so well.
Magnet wanger no flash
Magnet wanger with flash
I made a magnet wanger to make the magnets wang around really fast, but for some reason I registered only .2 of a volt
Here is the magnet rotating device (a stick with a magnet stuck to it attached to a motor) pictured top without the flash, and bottom, with flash to freeze the image so you can tell its there.
The bit of wood sticking out to the left holds the magnet. All the other tackle is as counter-balance to stop all the stuff on my desk from vibrating away. Unbalanced motors vibrate a lot.
The point here is that I had the magnet spinning over the coils very fast and quite close and got as close to zero result as I could, without simply not turning up on the day.
In the first test I did, I spoke of the electrons surging around within the coil. Those were my words, but I'm not sure I understood them. What if it wasn't just the magnet passing first on side of the coil then the other, but the simultaneous passing of the south pole on one side and the north pole on the other. Magnets have poles by the way. Actually I read they don't and magnetic poles are an illusion, but the site I read that on was way out of my league, so for now I'm sticking with "Magnets have poles". Sometimes illusions are handy.
So things that I might have done wrong possibly include, but are not necessary restricted to...
1. I used less magnets than my first attempt. Perhaps this arrangement wasn't powerful enough.
2. I had only one magnet. Perhaps I need a north and a south pole hitting opposite sides of the coil.
3. I had less turns on my coils. Even the biggest one had only 100. My first attempt had 157.
4. Perhaps my magnet was passing the coil slower. Or too fast???
5. Something/everything else
Its possible that there is a certain threshold below which you get nada, then suddenly you make some power. Some things work like that. I can't think of anything that works like that, but there must be some things that do.
Whatever it is, rest assured, I'll get to the bottom of it. I often finish what I start.
It turns out, most people who go to all the trouble of building a wind turbine, also go to all the trouble of needing one to do something for them in the first place. I need to develop a need.
I'm going to make some electrons wriggle. When I succeed, you will just have to take my word for it because electrons, like the invisible man, cant be seen by the naked eye.
So, here are some facts I know about electricity, and how to make it. Electron, magnetic field, flux, magnet wire, coil.
And some words.
Those are some words I've read recently.
To make electricity we can wave a magnet over a coil of insulated coper wire. The more we wave, the more electricity we make (or excite or whatever). The coil needs to be of a shape and size that the magnet passes first over one side, then the next. Not both at the same time. As I understand it the magnet imparts some magical force causing electrons to surge around in the coil. And it seems it's the difference between the sides of the coil that gives us the strength of what turns out to be called "Alternating Current" or AC. AC is the stuff that comes out (or peaks out then goes back) of your household electric outlet. Unless you live in the top left hand bit of Australia, where I think you still just get a wire from a gigantic battery to your house. Batteries give us DC or "Direct Current".
I have no idea what people who live off grid have spilling out of their wires.
You can turn AC into DC. This means we can generate some AC electricity, jam it through something called a rectifier, then have some nice DC to charge a battery with. Apparently.
Because my aquaponics system is already running via a 12 volt battery (for system security in case of blackout) I can feed any electricity I can make directly into that existing system. I might even save a dollar or two. Currently the battery is charged from mains power as the power is used by my pump. Any electricity I can feed in will lessen or remove the need for that mains power charger. I can still leave it connected, but adding some wind energy should just give me another layer of backup. And another layer of complexity to enablel more things to go wrong.
Which is nice.
I found some old electrical thing and pulled it apart and cut my fingers a lot. But I got some wire out of it. For my first experiment I thought I'd keep it as simple as possible so based most of what I'm doing on google searches that started with "the world's most simple...".
I started by cutting some corflute into a strip and making a box shape out of it. A box would have been better, but I didn't have a box.
Actually I started by selecting a nice blue background to create an elecron(ic) atmosphere. It should go nicely with the copper wire as well.
My blue background came from the back of a blank CD.
Next, I needed a high-tech axle. I selected a particularly nice looking toothpick.
I have a few very strong magnets stuck to my fridge. They are small, but according to the blerb that came with them, they require 7kg of pull to get two of them apart. I'm not sure if that's true, but they are strong enough so that I spend a bit of effort to not get pinched by them. It would hurt. I hate hurt. The little magnets are there as spacers, and to form a bridge for the magnetic flux. See me use the words "magnetic flux". Its a proud moment for us all.
Next step was to poke the stick through the side of the box, through the magnet spacers, and through the other side of the box.
This should allow us to rotate the magnets by turning the stick.
This in turn should wave the magnets over the wire, imparting magic, and exciting electrons.
Electrons love waving magnets.
Next I wound 157 turns (all I had) of my salvaged copper wire around the corflute box, making sure the wire was wound in a direction so that the magnets would pass over the coils at right angles to them.
Rotating the toothpick via my drill, showed 2.7 volts AC on my multimeter. Yay!
I should be able to make it better by adding some metal on the outsides of the coil, to turn the flux back. [In the future, I think the metal would attract the flux, drawing it through the coil]
Rotating it by drill also produced some light. I think its flickering because its AC current. The bulb is an LED which I understand only works when electricity is going through it the right way. Whatever that is. AC is going one way and the then the other, so I guess it didn't matter which way its connected for this test. All I did was twist the wires from the LED to the two end wires of my coil. I burnt the insulation off the wires with a flame.
Carbon footprint! I just need more toothpicks.
Interesting cow and magnet based factoid...
Did you know cows have magnets in them. They are called "cow magnets". We put them there to collect metal stuff they might eat.
Cows hate to poop out metal stuff.
WARNING !!! - Don't let little people swallow strong magnets. I understand they have a habit of meeting the other magnet the kid swallowed earlier, and making intestines heal together. Its probably a good idea for big people to avoid eating them as well. I'm not sure if that's a myth or not but, who cares. Magnets don't taste good so there is really no point taking the risk.
A wind turbine blade needs to present to the wind at different angles depending on which point on the blade we are looking at. Because the inside of the rotation turbine moves slower than the tip, the inside blade edge needs to look more like a bi-plane wing, and the tip needs to look more like a modern jet wing.
Try this. It wont make a wing, but it will demonstrate how we might make some twist.
Take a cardboard roll, and draw two lines along its length but on an angle, so that the lines don't quite run parallel to the sides.
Cut along the lines.
And you get this.
No great surprise, but it does show a way we might make a wing shape with a twist in it.
Our wind doesn't just need to be twisted, but it also needs to be thicker and broader in near the centre, and tapering off to thin and narrow at the tip.
That means if we draw a triangle like thing on our cardboard roll, we should get something a bit like what we need.
This should give us a bi-plane style wing at one end, a modern jet wing at the other, and everything else in between.
The little square bit at the far end is where I would bolt it onto the central hub if I was going to add 2 more blades and make a turbine.
We start to see something approaching what we need. It has a big thick wing shape near the centre, and a thin modern jet looking wing shape at the tip. It also has a twist in it so that the angle of attack reduces as we get nearer the tip. This is a good thing because the tip is travelling so much faster than the near centre. The faster it rotates, the more the apparent wind appears to be coming from the direction of the next blade, rather than at 90 deg to the turbine.
I put some sticky tape around our new turbine blade model to try to get a reflection that might make the shape clear.
I think this captures it a bit.
Now, none of this is my idea by the way. In fact many other people have made blades like this and they seem to work OK on smaller turbines. They just don't make them out of cardboard rolls.
The best part about all this is it looks like I might be able to use PVC yet again.
