Ducted fans and Wind collectors

good answer.. 401mm.

I would go for a Savonious version as it does not matter from which direction the wind comes from, so it can be made quite simply.....just a thought!

Darius do the same, but they're both terribly innefficient.

Cheers,

Stu.

...and terribly simple at the same time.....

If you duct a fan, you increase efficiency, but then have to turn the whole apparatus to catch the wind.

Efficiency is not as important as many think.

The power is free. If one method is simpler and cheaper than a more efficient method, you need to assess if a bigger version of the less efficient one will still be cheaper for the same power output.

A simple Savonius turbine can be made by cutting a 200L drum in half lengthwise and using the halves to make the "S" of the rotor.

(I'd draw you a diagram if I could work out how to feed it onto this forum. Obviously it isn't difficult, but I haven't worked out how yet. Can anyone help me?)

If one rotor isn't enough, you can stack another on top. The raw material is usually cheap and easily accessible, although the support bearings may not be!

Look here

A home made savonius turbine is all very good but in high winds when it will spin fast the problems of balance will become severe. Images of the turbine rolling Boedecia style acroos the land spring to mind!

Chas

I totally agree with you..I would be exporting them inadvertantly.

I have two points to answer here:-

1) Properly made and balanced, that should never be a problem. A good DIY person should be able to make a strong and well balanced unit quite easily. It really is just up to the quality of the work....

2) If the wind gets too strong, its fairly easy to have a built in "Condom" of canvas to drop down and stop the wind getting to the turbine, causing it to come to a safe stop. A strong peg(s) to completely lock it for maintenance is an easy further fix for such problems.

I see no problems that a good DIYer with a reasonable brain, could not fix fully and safely.

Hi Andy,

I suspect you haven't tried to live on a remote site.

The rules are similar to those of being at sea. Viz,

1/ If it can come to grief, IT WILL!

2/ When it comes to grief it will be in the dead of night with a howling gale and snow / hail / Rain by the bucketload (or all three).

Sceptic is suggesting putting two turbines vertically. Have you tried to fit a six foot condom in the middle of the night? (don't boast)

In real terms, the turbine is going to be taller than wide and would require dynamic balancing which i think would be beyond the possibilities of most home brew projects.

regards

Chas

The condom needs to be fitted, folded, all the time. A simple system with weights could be triggered to drop it.....but there must be several other ways too to stop the wind getting there....slats? I bet CR4 could think up a dozen ideas in a few days. Come on Guys!!

Its not as though I am talking about imaginary windmills, Helix Wind is selling them, look at my last post with the links....

I spent 10 years at sea, I know how strong nature can get, which is a further reason for KISS - Keep It Simple Stupid!

What you said is really only another reason to keep it uncomplicated!!

What about a speed sensor that would apply a brake system, similar to the electric brakes in a trailer, only the brake application would be triggered by the speed sensor.

Hi Andy,

I didn't say it couldn't be balanced, only that dynamic balancing would be beyond a homebrew project.

Sceptic's comment about free energy is more appropriate I think, as a normal windmill with a weather cock vane made to the required size would probably be easier to produce since it is simple balancing.

Bob C's suggestion of electrical braking is a technique used in quite a few commercial wind gens to keep rotor speeds within design limits.

regards

Chas

I really don't see why. A simple strobe with a pressure sensor (the same way that tyres are balanced on the wheel/car) will flash the strobe and a chalk mark and the balancing would be a complete doddle....many thousands, if not millions of people the world over who have balanced tyres using such equipment, could balance the Savonius windmill easily in this manner.

If you start out with the thought that you cannot do something, then you probably can't do it.

I never start that way......but many do......sadly for them!

Andy,

In theory this is simple, but far outside the capabilities of the average DIYer.

Have you ever had to make one of these balancer devices? And added the degree of difficulty to the project of producing a SIMPLE wind turbine to fit within the brief?

I've been professionally called upon to do just this several times, and in the process developed a simple, self regulating 'propeller' type wind machine.

The brief of harvesting 2kw from a small rooftop mounted machine of any sort in just 8mph wind IS the problem.

There are currently hundreds of folks engaged in just this conundrum. Anyone to successfully crack it will make a fortune.

Here in OZ there have been successful wind powered generators for 60 years or more, and none of them Savonius, nor Darrieus (sorry, last time I misspelled it), with very few which one could mount on a rooftop in the 'burbs'. Some of the most efficient machines are in the leisure marine industry, and usually attached to sailboats, however, only low voltage DC. I guess someday someone will up the voltage and invert it, in these applications too, but there goes the KISS principle, out the window.

K.I.S.S. is my credo.

Calling for power from the wind one has to take into account several factors: Space available to mount the machine; aesthetic requirements of the finished product; efficiency of operation; ergonomics of operation; relative cost of production of the machine. Not neccessarily in that order.

Having lived on an island on the 40th parrallel South, for 23 years we did indeed learn a thing or two about wind powered machines and their upkeep.

We built all of them. We eventually had to park the truck (pantec) in 'front' of the Savonius to stop it exploding . So, I guess that one of the prerequisites for building a 'simple' Savonius is to also purchase a pantec truck to act as the 'brake'.

Just a few thoughts,

Cheers,

Stu.

I am sure that there are badly built Savonius windmills around, as there are of many other types of equipment around where brains were not up front at design time.

There is a CR4 blog somewhere where here very recently where a car (US) manufacturer could not stop rowdies with a baseball bats popping the air bag on parked cars, till a secretary said, why not take the power off it when the ignition key is not inserted? DUUUUUUHHHHHHHH!!!

On you-tube, there are videos of large windmills over speeding to destruction, because the braking system failed.......

http://www.youtube.com/watch?v=lvvRHhsQhi8

Here is the Helix, it gives me an extremely solid impression,,,,,

http://www.youtube.com/watch?v=q9flSPAdOLk

Some of the VAWT Design features over a conventional design:-

1) Does not need to be turned to face the wind

2) Apparently no high frequency noises downwind, manufacturers claim silent operation.

3) Can be built on a single shaft, no gearing or belts needed as these can reduce efficiency

4) Could be easily fitted with any number of simple devices to "spill" the wind in the even of a storm. (Driving a truck in front of it appears to work as well if no other safety devices were installed!)

5) Does not require any "ground clearance" and need not be mounted as high if that is impractical for some reason

6)The thrust bearing(s) must only handle rotor weight, not wind power as well, so can still be safe, but substantially smaller for the same power output.

7) Radial loads are slightly higher, but as radial ball and roller bearings are generally the cheapest of all bearings, this is never a problem. Its far easier to handle radial loads than axial loads as many engineers know to their cost....

8) Simplicity. In North Africa, Arabs have been building such designs for several 1000 years......propeller designs come much much later.......

It is FAR FAR easier to stop wind getting to a Savonius windmill, even on a badly designed one as you can sometimes park a truck in front of it!!!! What could be simpler than that? You mentioned that yourself, thanks....

I even suggested a method or two of spilling the wind that you either made fun of or completely ignored (maybe the principle was not made clear enough by me at the time) and I know of another very simple method that is being patented right now......which actually improves the windmill performance in low speed wind conditions as well!!

Also, you seem to want to allow your judgement to be clouded by one bad personal experience with one badly designed Savonius.......that's your prerogative, but I personally would never let my own judgement to be so clouded so quickly.

That is similar to my mind in never getting in a car again after the first ever car accident, so you should never ever get in a car my friend ever again......they are highly dangerous and kill people every second of every minute of every day.......as far as I am aware, few people seem to have been killed in ANY windmill accidents where the wind got too strong!!! At least, the news is not reporting them very often!!!

One has to keep things in perspective and balance and not try and defend a position that is at best undefencable.......I am not telling you what to do either, you can carry on and do whatever you want in any area you wish, rightly of wrongly......but KISS is not being followed by you as well as it should be to my mind.......but again, that's your personal definition, forget me completely please.....

Also, you seem to have not found the time to look properly at the links I posted, where a company is seemingly producing an almost silent VAWT windmill (link has be placed here again!) that can be placed on houses without annoying the neighbours or the owners. I have yet to see a propeller design except for really tiny versions, that are fully quiet......I have seen some here that make make cats go crazy, because the sounds appear to be out of the human audible range and are always "downwind".....cat owners get upset, I expect dog owners too.....

The VAWT designs appear to be far far slower and hopefully do not generate any high frequency noises.....though I must admit, VAWT designs are few and far between here, at least at this time.....time will tell....I am sure that the future will bring them here too, I do sincerely hope so.

I wish you a great day in spite of me as I enjoy immensely the "repartee"!!!

Here we go again!

Andy, let me ask you what is your personal, hands-on experience with wind powered devices?

Are you, perhaps an 'educator', in real life?

You sure seem to have 'arced up' over this thing. Do you have some pecuniary interest in the type of turbine which you champion?

Resisting the temptation to take umbrage at your 'observations' I'll try to put this conundrum into the perspective, as I see it. (I'm sorry, but by definition, only you can see the problem from your side. I stand apart from you.)

Let me assure you that as a professional, practicing engineer of some 55 years, (5 Diplomas, 2 Degrees, plus trade qals in automotive, electrical and welding)

that the devices described in my previous blog were never 'badly built'.

I'm way ahead of you in the 'common sense' approach to engineering solutions. Don't need to be sermonised, as in you blog to which I reply.

Have experience with and have designed, and constructed wind turbines of ALL persuasions.

Savonius does have it's rightful place in the engineering realm. However, the man asked about a particular type of device, stated a particular application for it, and asked for advice on it. It seemed to me at the time that he mostly knew his own mind and didn't need to be lectured 'ad nauseum' on alternatives which, to me, don't even come close to fitting the brief.

Addressing some of your points: #2. Depending on several factors, one being size, one being rotational speed, the Savonius is NOT silent ( except at very low, to stationary, speed. #3. On a device of such size so as to withdraw 2kw in an 8mph breeze, how would you propose, in sound engineering practice, to mount the generating device to the rotor? Close couple it?? What size generator do you propose? #4. The truck is the easy way. After that, complexity and stability are diametrically opposed. #7 BS. Who is the pracicing engineer who, a. doesn't know his loadings, and, b. isn't entirely familiar with bearings to acommodate those loads. ( Axial loadings?? Ever seen the wheel bearings on the ubiquitous motor car, truck, tractor, bike etc................?) #8 And that's probably the best reason not to use it 'just everywhere'. Whilst we take great comfort and kudos in rediscovering an age-old remedy to a problem, it needs to be applied with intelligence, incorporating that innovation of recent times so as to PERFECTLY accomplish it's mission. ( How many times have we despaired of those who do things in a particular manner simply because our forfathers did so). Innovation got us from teh Archimedian screw method of moving water: pumps, ship's propulsion, etc. to the present day screw, yet, a simple device, but much more EFFICIENT at it's task.

Didn't ever make fun of you, old chap. Well, not yet anyway. Didn't intend to either.

Now, here's the bit..................

My experiences with these devices have indeed been personal, hundreds of them, but NEVER bad. And as for judgement..............you've certainly leapt to such in this para. Shame. Shame. Shame. I do reserve the right to apply the most appropriate technology to each requested solution without the bullying, and noise of bigots.

Sermon. Again.

The simplex is ALWAYS the goal of this here engineering office.

I do percieve that you are indeed telling me what to do. But maybe I'm less inteligent than you.

How could I EVER forget you.

Did too.........................

You'll have to tell the owners of those thousands of 'propeller' windmills gererating power all over the world, that they should have installed Savonius mills.

Finally, when all is said and done, I do really think that we are on, more or less, the same side in this. In that we should, as a world community, be cutting down on personal energy usage, so that our efforts to harvest the solar may, perhaps, take a major portion of the load.

In a previous dwelling I managed to have the entire energy requirements supplied by solar. Plasma screens and all.

I'm not worried about 'The Cat'. I know he'll put up with the noise.

Cheers,

St.

If what you say is true, then the Helix company are lying through their teeth!!!

Somehow that sounds (pun intended!) wrong, as they are selling to people who are putting them on their houses......would not the company go quickly bankrupt if what you say is true?

End result is that I think you are talking through the top of your head and probably have had even less exposure to some of these modern (and old!) VAWT devices......sorry Guy, but that's how it came across to me....

I saw a program a year or two back on discovery or similar where the Arabic VAWTs were being demonstrated, the commentator was standing right next to them and you cold hear them, but you could also hear and understand him as well. They were really primitive ones, super simple, amazingly quiet, but there was no particular need for quietness as they were built well away from habitats, at least those they filmed.....fantastic!!!

Here is a great study of HAWTs and VAWTs from Wikipedia, it details the advantages and disadvantages of both types.....very good reading.

By the way, it mentions that the vertical types, due to a lower rpm, can make far less noise......that sort of goes against your comments in that area - invaliding most of your other comments for me in the process, as if you got that point wrong, what else did you get wrong?.........

Here is a small sample, read the rest at the link below:-

VAWT advantages

• A massive tower structure is less frequently used, as VAWTs are more frequently mounted with the lower bearing mounted near the ground.
• Designs without yaw mechanisms are possible with fixed pitch rotor designs.
• A VAWT can be located nearer the ground, making it easier to maintain the moving parts.
• VAWTs have lower wind startup speeds than HAWTs. Typically, they start creating electricity at 6 m.p.h. (10 km/h).
• VAWTs may be built at locations where taller structures are prohibited.
• VAWTs situated close to the ground can take advantage of locations where mesas, hilltops, ridgelines, and passes funnel the wind and increase wind velocity.
• VAWTs may have a lower noise signature.

http://en.wikipedia.org/wiki/Wind_turbines#VAWT_advantages

Have a good one.........!

How did you get the truck to the roof in the wind?

Now THAT'S in the patent application.

Cheers, Bob,

Stu.

Stu, Your engineering qualifications sound good, Im working on basically the same thing as the original question, so let me ask this, as the wind passes thrrough the duct or nacell, what would be the best mechanism for energy transfer to the generator, a bladed fan?, a savonius, something else like an evaporative air cooler, this can be mounted horizontaly.

Spacecannon

SS,

A pleasure.

Right now the jury's still out as to the ultimate efficiency of the ducted fan from the un-. Work on blade shape is forging ahead all over the world and I won't offer a definitive answer on this. What's your annual mean wind velocity? Peak? And frequency of those peaks? Lots more questions to establish the 'best' way to harvest the breeze at your place.

Sorry. To answer your question as best I can- the most mechanically efficient way is to mount the fan directly to the generator shaft, however it rarely is that easy. mostly it is needed to have a small step-up gearset incorporated ion the nose of the generator. Recent iterations of these are very efficient, ie minimal power losses.

That said, there is much work being done using polypolar AC motors out of Fisher and Paykel washing machines, rejigging the field wiring, creating very efficient generators able to produce effective charge at low rotational speeds. Check it out. They are much sought after hereabouts. With the increased need for items such as these there will be manufacturers on your side producing the goods, without your need to resort to pliers and solder.

I haven't done it, but Google would be the best place to start.

You pose an interesting question with the 'squirrel cage' blower from a cooler harnessed as a wind turbine. Never thought of it before myself. I'll do some work on it as soon as time permits. I guess someone must have.

My math indicates that the radial bladed 'propeller type of WT is the mostly the most efficient to use. Reliable, and efficient, reductions can be done with aramid fiber Gillmer belts.

As indicated by the developments in fan blades, ie the new scimitar shaped ones -car cooling fans, aeroplane propellers, boat propellers, et al-seeking the most effective way to apply power to the medium, it has always seemd to me that to wrest power from that medium the exact reverse strategy might be the best answer.

Don't often see an aircraft propelled by a Savonius rotor. Won't say that it won't ever happen, but I can't see it.

There was an American guy in West Australia who developed and made, to my eye, a good design of a WT, which was auto regulating ( self feathering). It was a 'down wind' style with a flying tailplane. I've forgotten his name. If I come across it I'll let you know.

Well. Me about done now. Have to go to work.

Cheers,

Stu

LOL!!!!

Unlike other turbines, a Savonius is basically a drag machine and can't generate tip speeds as high as wind speed.

Of course in a cyclone when it can gust to over 200km/hr, this can still be considerable, which is why they should always incorporate a speed operated brake.

Might be fun to export one, but I'd rather not be in the vicinity!

Hi capblanc:

The mind boggles at the thought of a rotor spinning off it's pedestal and racing off along the ground.

In fact, the tip speed of a Savonius rotor is less than the wind speed, so these things are inherently fairly slow speed.

At 8 m/s about 150rpm

At 20m/s (72 km/hr) about 380 rpm

At 30m/s (108 km/hr) about570 rpm.

You would probably be applying a brake above this point.

At 50m/s (180 km/hr - cat 2 or 3 cyclone) about 1000 rpm.

You definitely wouldn't let it run free under these conditions.

As others have pointed out, balancing isn't especially difficult, even for the DIYer.

I still love the image of the rotor exporting itself into the neighbours yard, even if it isn't probable.

Hi Sceptic,

I was researching spares for a product called a "Wind-bugger" which unsurprisingly with a name like that, had gone out of business. (Andy in Germany is going to love this!) What I did find was a whole bunch of blogs with complaints, one of which was a report of the rotor coming loose and "autogyroing" across an anchorage for >100m before hitting the water. This three bladed rotor of GRP was about 5kg and 60cm dia. , Potentially very dangerous.

BTW the "Helix" linked by Andy was beautiful and almost worth having as a mobile sculpture. I would suppose that the helical form will reduce wind noise as well.

regards

Chas

Perhaps you could utilise a tail or rudder, similar to the windmills which dot the Australian landscape for pumping artesian water.

This one is 7m diameter, 13m above ground and pumps 3500 litres/day of water.

It would be interesting to compare the efficiency comparison with a shrouded and unshrouded version. There was a company promoting a commercial venture in the early '90s of a ducted wind turbine based on the Northrop Grumman shrouded fan principle. This one was of concrete construction, base and shroud. I think they were looking at something like 20m diam impeller and I recall the direction to wind control was via a control system of some form.

I've often wondered if the addition of a small shroud to each blade (a simple winglet in principle) would improve the operation of these wonderful old windmills.

They have done a fantastic job in country areas. Most of the Australian stock routes would have been unworkable without them.

something like this? let me know what you want to change.

Winglets on a wing reduce induced drag by, in effect, increasing the length of the wing, reducing a strong vortex of air at the tip from the high pressure side to the low pressure side. The "long side" of the winglet should be more or less perpendicular to the chord of the airfoil, as if the blade were bent 90 deg., so it will appear to be "wrong" if you don't visualize the airflow at the tip of the blade. (With apologies to Whitcomb, the "first generation" of winglets were simply flat discs at the wing tip, and they worked well, but looked uckey and spoiled the lines of the airliner)

The duct should have an effect similar to the winglet, reducing tip losses. If the winglet is moving at high velocity (as it will on a rotating blade) relative to the nearby stationary duct, there will be all sorts of energy-robbing effects, tremendous shear in the air flow between them. Attempts to put some sort of sophisticated "twist" in the winglet will, I predict, be unproductive. Choose a duct or winglets, but not both.

Consider the extreme situation. The winglets are extended to form a complete ring around the rotor. It would be, in effect, a rotating duct, but the great "wetted area", the amount of skin subject to friction with the air, would clearly make it much less efficient than the conventional "tipless" rotor. It will also add to the angular momentum of the assembly which, if nothing else, will make it less responsive to gusts and will likely require a stronger structure, bigger bearings, etc.

so should the winglet have the lift vector towards the radial center?

A lift vector toward the center is not going to produce power. The object is to reduce the energy wasted in making vortices. One gets the same effect, but better, by extending the blade.

If the lift vector of the winglet is toward the center, that lift is produced by deflecting air away from the center. (Remember, F=MA; one must accelerate air to get a lift force. Don't believe those FAA pilots' manuals written by ignorant bureaucrats. Bernoulli has nothing to do with it) There might be some very small advantage in that it maintains the lower pressure which motivates the blade to turn, but I doubt it would be significant. Similarly, if the winglet lift vector is outward, it will be moving air inward, reducing the lift of the blade. Either way, the added drag and structure will be a negative. I'm not a slave to tradition, but there are good reasons why propellers and helicopter rotors don't have tip plates or winglets.

Heres a curiousity I stumbled across.. very interesting organic adaptation of winglets. very birdlike

GA. Is it possible for the wing-lets to also counteract centrifugal forces as rotor speeds increase?

It should be possible to arrange them to have a net thrust inwards towards the hub.

This could be a useful addition to conventional HAWT blades.

I haven't seen anyone do it yet, but it could allow longer blades.

I managed to resurrect some of the diffuser wind turbine concept images of the early '90s. Their proposed size was about 20m diam and around 3MW.

I've modelled up my Horizontal Axis design in more of a construction oriented way.. just to figure out more about how it would work.. look here

Chris

With your design it would be possible to mount another speed reducer and generator in the forward nose cone. The same pivoting movement design would stay, perhaps the blades could be larger.

Hi bob_c,

I think that maybe if you had a counter rotating pair of blades... the extra generator could definitely go in the front.. its probably the best way.

if you have something specific you wish to model up for development...send me a pm.. if I can find the time... or you can hire me of course.

Chris

I am not in the air moving business as a way of earning a living but There are some things I have learned being at an airport for 25 years. The only reasons that I can see for the ducted fans are 1) funneling a larger cross section of air into a smaller fan opening. 2) using the ducting to help align the fan to the wind direction. and 3) To keep the air that hits the fan blades from slipping off of the outward edge of the fan blades. This effect was occurring on airplane wings at higher speeds. And because of that, wing-lets were developed.

Could the same type of "wing-let" design be Incorporated into a fan blade to increase the efficiency of it?

OK, it seems there are concerns about a rotor overspeeding and or destructively relocating itself. While it is true that perhaps the most economical propeller type rotors are fixed pitch and probably laminated wood, there is much to be said for variable pitch. (NASA spent $millions building wind turbines with blades that looked like airliner wings, requiring periodic inspections for popped rivets and fatigue cracks. After a while, even NASA conceded that composites are better, and they decided wood is the most economical composite) If wood, the pitch is fixed, and at high wind speeds the rotor will stall and self-limit the rotational speed, we hope. There are other approaches.

I would propose the following:

1. The rotor starts with a hub and two "spokes", rods or tubes which form the spar of the blades.

2. Several airfoil sections are strung along the spars, free to rotate around the spar.

3. Each airfoil section has a trim tab or equivalent which aerodynamically establishes an angle of attack relative to the local wind.

4. The trim tab or other control can be set to establish a given lift (think of a measurement of the pressure difference between the sides of the foil). This can be very simple, like a diaphram with a push rod to the tab, or even a spring. Or, if you have gov't funding, put Intel inside. Obviously, the airfoils at a larger radius from the hub can generate more lift. Centripetal acceleration ("centrifugal force") will keep the flexible spar from bending excessively.

5. The control can be set to zero lift, if need be.

If set for zero lift, the rotor doesn't rotate, even in a hurricane, though some rotation is probably good to keep the spar in tension. If set for a fixed lift, gusts and high winds will tend to feather the foils, limiting lift and drag forces. It is relatively easy to keep torque and rotational speed constant. If the lift setting is readily adjusted, the output can be maximized for the available wind. The foils will, of course, line up with the local flow, giving "optimal" twist to the blade over the entire range of wind speeds. Thus it will not stall. The foil sections can be mass-produced, perhaps extruded plastic.

The dynamics of the rotor are interesting. A faster wind at greater altitude, or turbulence, will not bend the rotor blades, as the lift is constant. There are no torsional forces on the spar, which can be fairly flexible. It's like swinging a chain around your head, as opposed to swinging a board. Fatigue problems should be minimal.

Once the wind trubine industry has perfected the rotor, use the same engineering for helicopter rotors, which would be gust resistant and easy to control (as in UAVs).

It would sem to me that the more complex the rotor-blade assembly, the longer time for return on investment. Almost as if there needs to be two distinct approaches. One for commercial wind farming, and another for direct consumer wind farming. I believe that it would be cheaper to build 2 inefficient generators than 1 efficient one.

Hi Esbuck, I understand what you are trying to achieve but I cannot picture it exactly. Have you any way of sending a sketch of your concept. I can give you my email address if you want. I use acad ,do you ?

Here's a rough sketch. The airfoil section rotates around a tubular spar. It can be built using model airplane techniques, such as foam plastic with mylar cover, or with conventional aircraft techniques, as with aluminum sheet. 21st century geeks can use digital control, perhaps by fiber optic, but old conservatives like me like simple analog systems. The trim tab aligns the airfoil at as suitable angle of attack, say 3-6 degrees, with the local wind. Lift, torque on the hub, will increase to some maximum, at which point the pressure difference across the airfoil sucks on the bellows and reduces the angle of the tab, therefore the angle of the airfoil. Over a wide range of wind speeds the torque is constant. If you need to stop the rotor and the wind is blowing, pump some air down the tubular spar. That puts the tab in the no-lift position and the rotor looks like the no-wind sketch, no twist. In use, each airfoil section aligns with the local wind, so the blade has close to optimum twist.

Everything is lighter than a conventional wind turbine. Except for gravitry only, the no wind condition, the spar is in tension. the short airfoil sections are not stresed much. (Each will have a thrust bearing on the spar, so it experiences no forces from other sections) By analogy, consider carrying a 20 ton load in a bomber. It requires a long wing with a deep spar. Alternatively, carry the same load with a few fighter planes flying wingtip to wingtip

OK, somebody please explain to me how to get the picture to show. I sketched the airfoil and photoed with a digital camera and posted the photo. It looked fine before I hit SUBMIT, but now it's gone?

Ya I don't know.. maybe you are on dialup, and it got interrupted or something.. try again please. Is it JPG you are posting?

Chris

When you find the answer, please let me know.

I have a picture loaded into a "word" document and I can't get it to transfer onto CR4.

Incidentally, how do you do sketches and load them on here?

I have had some luck clicking on a corner of the picture, and then dragging the cursor to the opposite corner. This will usually highlight the picture. Then right click and choose copy. Then go back to the reply box on the post. When the message board opens up, type the words needed, then choose an appropriate area and locate the cursor, and right click and choose paste. That is my best suggestion.

Thanks bob c:

This is the sort of thing a wind turbine must cope with

Wooden stake through palm at Silkwood during Cyclone Larry

I think you get an idea of what I am trying to paste, but this is all I can get.

Wooden stake through palm at Silkwood during Cyclone Larry

You posted the wrong picture. This is the snow storm from 2006. The polar bear is on the left.

Esbuck please try sending it to my email address michael@roof2000.com

It should work

Maybe this will help:-

http://cr4.globalspec.com/thread/15743/How-to-insert-Graphics-into-your-Post-to-make-it-more-readable-or-interesting

Basically get the picture as a jpg somewhere on your computer:

click on the little green camera

click on browse

Find your picture, then, Submit.

If it may help, if you look at the properties of "successful" loaded pictures their properties are something like;

http://cr4.globalspec.com/PostImages/200902/red_dot_sight_001_7CC22CBF-9792-9781-

compared with the missing image which has properties;

aolemb://E6843150-8B65-44D6-94E3-20588F4A0701/Garth's%20visit%20001.JPG

and missing the leading globalspec details. Seems related to submit process, type of jpeg, folder too deep in directory tree or time-out issues ?

For the image in a Word doc, I would expect you would need to get it out of the word doc, saving as an image to a specific location, before you could upload.

well.. this is not a ducted idea... and I'm not sure if my image will explain it properly.. but it is a new invention... if you have heard of such a thing before..let me know.

it originally started as a kind of inverted paddlewheel idea for the side of a house...

and in order to make it work, you have to stagger the wheels... basically the lowever half if the wheel is enclosed (insided the pointed box), and the upper half moves in the wind, with as much resistance to the wind as possible.. I'm sure it is kind of half-baked.. but I also think it would at least move if unloaded.. not sure how it would actually perform as a loaded system. the green arrows indicate wind direction.

I've got 75 images as bmp.. but haven't figured out yet how to make them into an animated gif that I can put on here.

I had to experiment to get the right wheel size versus the wheel spacing and length of connecting board. (for lack of a better word).. and the angled verticals on each board are just to catch the wind.

the direction of rotation is clockwise. the image shown has ax. 12 foot wheels. the boards stay parallel to each other and to the ground. it might be easier to just use gravity like a ferris wheel, but what the heck. I hope the function is obvious... but if you have any questions, I'll do my best to answer them. if you want to see larger images, send your email to me in a pm.

Chris

Chris,

Invert the thing and you have a very efficient propulsion system for a watercraft (paddlewheel). Very much reduced entry and exit losses as the 'paddles' act in the water, over the conventional, already the most efficient of the water drives. The mechanics of it would indicate a power limit though. Not nearly as sturdy as a conventional paddlewheel assembly.

You certainly have a fertile imagination.

Keep up the good work.

cheers,

Stu.

thanks Stuey.. its really just a parallelogram.. sortof..x3

I originally thought there would be 4 wheels.. but couldn't get that to work..so trial and error.. and voila...

just for fun. I do believe you are right about the simple paddlewheel.. the only benefit is the longer exposure to the current of the fluid.. maybe that will help.. I can't tell without testing.

Chris