Pressure and it's limits

The energy stored in wind is like the wind stored in drivers. 

If you get a string of it and the bit in front tries to stop for a bit, all the other bits of string like to plough into the back of the stopped bit at the front spilling it's coffee all over its lap. 

So... that's the Betz’s limit in a nutshell.

120ThingsIn20Years just found hundreds of drafts in it's outbox all scheduled to automatically publish over a decade in around 80-90 years. Stay tuned I guess?

Wind energy - nothing to see here

I went for another drive in the country. This time I only got as far as the Flinders Ranges only a few hundred kilometres north of my home.

I'm out looking for windmills, and photo opportunities.

There are plenty of photo's to be taken, but none of windmills.

I'm told they have all been retired.

The closest thing to a windmill I could find was this...


[upload your own photo here]



Actually, it turns out that I cant get a good enough satellite connection to upload a photo, so I'm off to the fire instead.

Fires are much more reliable than satellites.

Wind energy - Carving wooden blades 3

I'm not so sure I can make the other half of this thing.

And I'm not so sure my glue Fu is powerful enough, or dynamic enough for this caper.

I got a shape that looks a bit like it should, but its in 3 very distinct steps. I get the feeling this will make for some inefficiencies , and perhaps a stack of noise.

It takes a lot of plane work and file work to get to anything that looks by eye to be about right.

The big problem, that is the problem bigger than the ones I'm dealing with now, is that I have to go on to make another of these on the other side. I have no idea if I can do that.

This blade will work, but its a thing made by eye, and it's a thing that deviates from the image I have in my head. Its not the same as the image in my head, how am I going to make another one that's the same as the one I already made.

But on more immediate concerns, my blade broke a bit when I was filing it.

I used PVA wood glue. (that white stuff you can make removable fingerprints with when you should have been listening to your teacher) But I think some epoxy might have been a better bet.

It should be safe enough because all sections will have the shaft through their centre, so if it all comes unstuck it will just be a motley collection of different shaped puzzle pieces spinning around in the breeze.

I glued it back together with yet more PVA glue just in case it will do, and wrapped it tightly with tape to hold it in place to dry.










I'm really not sure if I can make another blade the same as this without developing some other method. I have a pretty good eye for 3D shapes as a result of doing a bit of pottery, but I also have a pretty good understanding of the limitations of my current skill set.

At the moment I'm thinking...

• Cutting this blade up into sections so I can trace the shape onto thin sheet plastic or something so I can cut out a series of section profiles that I can test a new blade against.
• Mould making to duplicate this blade in cast plastic or something.
• PVC (with PVC, I could use a template so I could copy the first blade I made. Other people have used PVC with some success, especially on smaller windmills like this one.
• Or even making a big version of my proposed lure copying machine. I'm pretty sure that would work, and it only requires longer threaded rod to make the thing big enough for this project. Longer threaded rods, and being built in the first place. 
• Something else

It's interesting to see that, if I include my newly learned PVC tech as a "thing", three of my five ideas include stuff from previous 120 "things".  I wonder if that's going to happen more and more.

Mould making was suspended until I had a project that actually required it, so perhaps this might be it.

But I do love working with PVC. It's just so easy to cut, file and drill. Mmm Polyvinyl chloride.

Wind energy - Another drive in the country

Always willing to bring yet more wind energy information to the world, I once again made the sacrifice of going for a drive in the country. Last time I went North, this time, South.

In fact this time I drove down to Glenelg River in Victoria, just East of the South Australian border, just north of the wet stuff at the bottom of Australia that keeps us from walking to the south pole. This trip was only a little over a thousand kilometres. I spent a couple of days there to look at stuff.

I saw a stack of these.

Some, mixed in with these.

And I even saw one of whatever this is.

This thing was actually kind of interesting. I might have to make one out of drinking straws or something. It's most interesting aspect was that it worked like two different styles of wind turbine depending on which way the wind was blowing.

Or not. I'm not sure. But if it didn't work like I think it does, then I've just had an idea.



I just walked in the door.

Sleepy.

Wind energy - Carving wooden blades 2

Sometimes you just have to wait until glue dries before you can progress with your wind turbine construction. This has been one of those times, and this post follows on from the post called "Wind energy - Carving wooden blades".

After undoing all the clamps, I still felt a bit like I had no idea what I was doing. This was partly due to knot getting enough sleep, and partly due simply to the fact that I really don't have any idea what I'm doing.

I'm still not certain I've got the shape correct.

But that's ok. I'll learn some stuff anyway.

Just don't copy this until you see if it works out.

The aim here is to try to make the blade have a steeply angled, thick wing shape at the slow centre, tapering out to a thin, slightly angled wing shape at the faster moving tip.

The cuts I'm making go to approximately 6mm from the edge to around 6mm from the other edge

It seemed like a good idea at the time.

I used a coping saw to make these cuts. A coping saw is the only saw I ever enjoy using. They have rotatable blades so you can cut sideways, and because the blades are very thin, you can cut circles etc. They are the only saw that seems to cut anything. It might be that, because the blades are so thin, you break them all the time. This means your blade is always brand new. Buy a coping saw if you need a small saw. They are very cheap, and are great to work with.

It took around 10 minutes to make the cuts.

Any of the regular readers (hi regular readers) might have come to realise that perhaps I don't use rulers and things as much as I should. This may be one of those times.

If you look carefully, you can see a collection of random looking lines drawn on the wood. At least one of these lines is important. Perhaps two. 

This is the under side of the blade. Actually I think this might be the front. This is my problem. I cant tell. I'll cut and see. 

Hack away at the little bits of wood between the cuts. They break of in a very satisfying way. 

I used a chisel for a bit, then just hit them with the side of the chisel as if it were a hammer. 

Then I just used a hammer. 

Once again, I'm a little surprised.

It kind of looks a little bit like it might one day resemble a turbine blade. 

The wacky angled bit of wood in the foreground is just the top, smallest length of wood on the progressively more angled stack. 

The bit sticking out toward the back is the blade I just hacked into a rough shape.

Next up, let the filing begin.

This might take a while. It's not as smooth as it looks in the photo to the left.

I'm tempted to just use the angle grinder, but I thought I should do at least one side by hand to keep it to a basic set of tools.

If it takes too long I'll use the angle grinder for the other side, but this one will be by hand.



And using an angle grinder might set fire to my project anyway.

I used a bench grinder to carve my home made fishing lures in a previous "thing", and that got a little hot but worked quite well and was fast.

We shall see.

Wind energy - Carving wooden blades

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 hate waiting.

I hate design doubt.

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 - Wooden blades

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.

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 - Furling model turbine

Even more than usual, I'm pleased with myself.

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.

Wind energy - Coil winding

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.

Wind energy - Coiled again

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.