Hi JoeF,

For the Cyclo-Kite (Bird Windmill), the goal is to make the blade aspect ratio as small as possible without significantly reducing lift and thrust. So I found that I can go as low as 4 without a significant loss of power. In other words, the span is 4 times the chord. In general, wings work better with higher aspect ratios. But in the case of the Cyclo-Kite, the solidity ratio is very low due to using only one blade and using a very large blade orbit diameter. So what is needed is the highest solidity ratio in order to increase the power. That can be done by using the largest blade span, as determined by the height of the towers and the chosen RPM. Then, to maximize the area of the blade, use the largest, practical chord length. And that is ¼ of the span. A primary reason for doing this, a controlling variable, is that the TSR is limited (so far) to 2. That is too low for the solidity ratio. So the blade area needs to be as large as practical to compensate for the low TSR. Only if the TSR were much higher would a high aspect ratio blade would be preferable. A higher aspect ratio blade does not seem to increase the TSR. As I recall, I’ve tested up to an AR of about 8 to see if it makes any difference in the TSR, but no noticeable improvement.

Incidentally, the blade/kite is not a “Looping Arch”. That’s an misleading label assigned to it out of ignorance.

PeterS

DaveS,

The interactions are between blade lift, gravity, and the energy stored and released by the elastic cords.

PeterS

Hi JoeF,

Fig. 9 in that paper contains errors which overly complicate the diagram and make it non-standard: the azimuth angles go in the wrong direction and opposite the direction of blade travel. That is why his quadrants are non-standard. If, his azimuth angles went in the correct direction -- counter-clockwise -- his quadrants be numbered counter-clockwise as well, and the same as I have described.

As for your aside, I’m not quite sure what you have in mind. It sounds like you want to make a cycloturbine with 2 blades, and with its central axis horizontal, and then you want to use Bird blades on long cords. If so, that could be made to work. I demonstrated it using a vertical axis in 1978. The tricky part is the length of the blade-support-arms that serve keep the blades on opposite sides of the rotor. The windmill is a hybrid pitch-control system of a Bird Windmill and a Sharp Cycloturbine. A Sharp Cycloturbine cannot operate with its central axis horizontal because gravity interferes with the pitch-control. The Bird Windmill can operate with its central axis horizontal because the blade is in free-fall, so gravity does not affect the pitch-control. However, a Bird Windmill has a TSR of only 2, while a Sharp Cycloturbine has a maximum operating TSR of about 4. So the question for a hybrid of the two systems is how long the blade-support-arms can be before the pitch-control is affected negatively, meaning lowering the TSR to less than 2. If all this seems a bit too complicated, that’s because it is.

PeterS

Hi JoeF,

One of the big advantages of passive pitching, as for the Bird Windmill (Cyclo-Kite), is that it does not require mechanisms or computers to control the pitching. That simplifies enormously. So there needs to be some large advantage to using radio control in order to justify using it. If it could increase the TSR, then it might be justified. But I have doubts that it could increase the TSR if the blade is suspended on cords.

PeterS

Hi JoeF,

The purpose of the Bird Windmill (vertical orbit) on towers is to make the side forces as “huge and oscillating” as possible so as to create an oscillating pulling force. That pulling force can be transmitted, via a long cord, to a pump, or it can be transmitted to a rotating shaft with one-way clutches to spin a generator. The purpose of the expanding orbit diameter is to keep those oscillations under control by limiting the RPM so as to prevent uncontrolled shaking.

Electricity can be produced by mounting a ram-air-turbine (RAT) on the Bird blade. I tried it and made it work, as shown here while using a vertical axis:

https://www.youtube.com/watch?v=x5VdGIKT9mo 

The LED mounted on the blade is hard to see without freezing the picture, but it is fully lit. The blade is much heavier than it needs to be, and the RAT is too large for the blade, but it worked anyway. The electricity could be transmitted on wires paralleling the elastic cords. The swivels can serve as slip rings.

PeterS

Hi JoeF

I can’t visualize what you are describing because I’m not sure what some of the terms mean. A sketch would be helpful.

PeterS

Hi JoeF,

There is no need for any hopping. The Bird Windmill, like other windmills, can be mounted on a boat and connected to some type of propeller or fin-drive, so as to sail directly upwind. I have sketches of how to do that. It’s fairly simple. Another option is to cause a Bird Windmill with a vertical axis to rock a boat, which is then propelled by fins sticking out from the sides or from the bottom of the hull. That too can go directly to windward.

However the speed of the boat will be limited to about ½ of the wind speed in all directions. That is due to the high drag of the windmill.

I invented a way to go faster than the wind in all directions on water. The basic principle is called “Power Alternating Sailing” (PAS). Basically, two windmills are used. They take turns propelling each other forward. The stationary windmill provides the power. The moving windmill is feathered to minimize drag. There are different ways to design the boat, or twin boats, to accomplish this. The speed is only the average speed of the two windmills, but there is no inherent limit on that speed.

PeterS

Hi JoeF,

“Ignorance” was too strong of a word. I just get tired of people changing the names I give to inventions – because it creates confusion. Sometimes I have to do it myself when people can’t remember a name for some reason. The same objection applies to changing the names of particular phenomena if it doesn’t serve the purpose of clarification, and it usually doesn’t. It create unnecessary ambiguity.

Yes, there is still much to explore.

I don’t have multiple papers about the Bird Windmill; just one long one, plus many drawings of variations.

Technically speaking, the cords and blade do not create a “troposkein” shape because they form almost straight lines -- due to the concentration of mass near the middle. Although, they serve much the same purpose.

One of the versions of a Cyclo-Kite (Bird Windmill) that I think has promise is one that you may have already seen in a drawing. The drawing is called “Bird Windmill Advertising Sign”. Here is a description of a power kite version of it:

A pilot kite suspends the blade below it on a single cord. Then the blade suspends below it, on a single cord, a RAT. The way that it works is quite unusual. I tested the basic concept and it worked, much to my surprise.

When the blade begins to orbit, it causes the RAT to orbit also, but on the opposite side of the axis of rotation. So they counterbalance each other. Also the weight of the RAT serves as a sort of gravity anchor to keep the blade below the pilot kite; to keep it from being blown downwind and tilting too much. So the blade provides the power to pull the RAT through the air. The RAT would require a hoop around it to protect the blades, and a tail fin to keep it pointed toward its apparent wind. The only complication is that to get electricity from the RAT up to the pilot kite and then back down to the ground, requires a slip ring near the RAT. The very high speed of the RAT means a higher voltage and thinner wires.

What I like about this concept is that it requires no controls once flying. Very simple parts. In high winds, the orbit diameter of the blade will increase to keep the RPM low. In high enough winds, the rotor may be blown downwind to tilt it so that it loses power. But testing is needed. Elastic cords might be needed to provide enough orbit expansion, but maybe not if the blade cords are long enough to begin with. The drag of the RAT doesn’t interfere with the blade’s TSR directly, so the TSR should still be about 2. I have placed a rod at the bottom end of the cord and used it as the weight. That was the first weight I tried.

Alternative designs are possible. For example, the suspended kite could rotate a crank arm on the pilot kite, and the crank arm could spin a step-up pulley system rapidly. with a loop belt extending to the ground. But this might be heavier and more complex.

PeterS

Hi JoeF,

The hard part of using concentrically orbiting blades is to figure out how they can self-start without bumping into each other.

PeterS

Hi JoeF,

The TSR stays almost constant throughout the orbit. That’s because the blade take time to speed up and slow down.

But something quite interesting happens. The upwind half of the orbit is flattened somewhat. So the blade doesn’t need to travel as far as a half circle would require. Conversely, the downwind half of the orbit is elongated somewhat. So the blade has to travel farther than it would if it were following a half circle. That means that the blade completes the upwind pass more quickly than the downwind pass.

A similar difference occurs between the upward and downward parts of the orbit. The blade completes the upper part of its orbit faster than the lower part.

These differences are beneficial in that they help the blade to orbit.

PeterS

DaveS,

The popular terms are “VAWT” and “HAWT”. The technical terms are “cross axis” and “parallel axis”. “Wind axis” is acceptable too.

“diagonal axis” is probably too ambiguous. Please define it and I may be able to show you why that is so.

PeterS

DaveS,

The Bird Windmill -- when its axis is horizontal and perpendicular to the wind -- can be seen as both a windmill and a kite. As a kite, the concept of a kite “window” does not apply because it can be made to orient 360 degrees to the wind by using a V tower or by using floating tower support that can easily orient to the wind (around a buoy).

My point is that most “all” inclusive statements (those claiming no exceptions) tend to be incorrect because only one counter-example is required to refute them. The difference to keep in mind is the difference between a rule and a law. Rules are generally true. Laws are always true. In science, treating a rule as if it were a law tends to imply a lazy analysis and to reduce one’s credibility.  

PeterS

DaveS,

Thanks for defining the term “diagonal axis”. You are limiting its use to only Doug’s ST. And you define it as a roughly 45 degree upward tilt.

I checked Doug’s website. Doug has various ST (multiple rotors on the same shaft) designs, and some of them do not have an upward tilt; they have a sideways skew angle. Others do not use a roughly 45 degree tilt when they tilt. And some use a curving shaft that cannot be accurately described as a 45 degree tilt.

So, your term “diagonal axis” is nonsense.

PeterS

Hi JoeF,

Thanks much for the drawing. I see what you mean. I like that you are trying out ideas conceptually.

I’m not clear on what advantage this design would have. If a single shock cord is used instead of two, then it will need to be thicker, and the drag will not be reduced much. Also, at a TSR of 2, the drag of the tethers is relatively small, so reducing it is not very important.

The main problem I would expect to see (based on my experimenting with a single HAWT blade on a single tether) if you built this is that the wind would shift directions, and the blade would try to align with the wind. The blade when downwind would do the aligning, like a tail-vane. But the upwind blade pass would be blown in the same sideways direction, whereas it should align toward the wind, not away from the wind. So the plane of the orbit will start to wobble due to wind forces and gyroscopic forces. At some point, the blade may move far enough to the side as to impact the horizontal bar or the support towers.

One of the functions of using two blade cords is triangulation so as to prevent that kind of wobble from occurring. They force the blade to stay in its plane of rotation. Then, to orient to a change in the wind, a V tower with yaw can be used, or the two towers can be made to float and orient around a buoy.

But I like considering new ideas anyway, even if I can’t figure out how to make them work. So thanks again for the drawing.

PeterS

DaveS,

“Phase analysis reveals the kite only drives as such in window angles. The rest of the orbit is centrifugal inertial-ballistic. To the observer, it looks like kite window angles do not apply. They do.”

Sorry, I don’t speak Martian. Please translate into English. Please leave out the idiosyncratic terms.

PeterS

DaveS,

Clear as mud. At least you are consistent.

PeterS

DaveS,

Wrong again. HAWT means horizontal axis. Some ST are horizontal axis and are designed to have a horizontal axis, with no vertical tilt. So they are most definitely horizontal axis to begin with.

You seem to have been born with a logic gene missing somewhere. You can seem to manage analyzing the simplest things.

PeterS

DaveS,

If a speaker wishes to be understood by the listener, it is the speaker’s responsibility, not the listeners.

So clearly you did not want to be understood for fear that you would once again be shown to be speaking nonsense.

PeterS