Wind Power

It looks as though it might, though the turbine needs to be sized to provide no more than 130W, to preserve the motor.

Quiquid agas, Sapiens, fortiter ex animoque.

I'd have thought it was a good starting point to allow you to get something up and running on the WAQAP principle... (wrong as quick as possible) as this is vastly supior to 'Right first time' which only works in ideal conditions when 'first time' is retrospectively defined .

The Mk II will doubltless be better... but let us know how the mkI goes.

Good luck

Del (here's a gratuitous link)

Del,

Thanks for the interesting link.

Fourmdev

How will you connect the blades to the motor? You have to try to not over spin the motor during strong winds, while getting as much as possible from less than maximum wind conditions. For this reason, you need to consider some way to change the ratio. Multiple groove pulleys comes to mind, as on drill presses. I came across a machine shop that had a collection of very old machinery. Two different machines had belts from the motor to a truck transmission. From the truck transmission to the input of the machine. (One was used to scrape keyways, I don't remember the other.) Good luck.

Variable pitch blades appear to be the most efficient method for limiting the speed of the motor at the top end, and providing the torque needed at the lower end.

The best designs show up on aircraft, especially those in the lower horsepower/speed ranges. Because those planes are light, they are far more sensitive to weight, especially weight cantilevered off the front of the engine.

Most are three bladed and have the blade shanks mounted in tapered roller bearings in the hollow hub. Some use a hydraulic piston to allow the pilot to vary the blade angle from the cockpit. Others use a Bowden cable method to achieve the same thing.

Regardless of the method chosen, I see no reason why a simple, mechanically driven governor can't be developed that allows automatic blade angle adjustment to optimize the system over a wide range of wind velocity. You don't need much of a change angle: I'd be surprised if it were more than 15°.

If nothing else, it will do a better job of keeping the RPM's at a constant speed. That might not be important to you. I'm not sure. I'm better at mechanical designs than electrical.

When designing and building the blades, exercise care in selecting the airfoil profile. Choose a profile optimized for the air speeds likely to be seen. The NACA library of wing profiles is a good place to start.

When building the blades I suggest the use of Uni-directional carbon fiber for most of the layups with fiber orientation parallel to the blade span. Do this over a medium density foam or balsa core so as to keep the weight to an absolute minimum. Not only do such light weight cores add dramatically to the stiffness of the finished product but they are easy to contour to the airfoil profiles selected.

Low weight is of paramount importance as the centrifugal loads on the shanks increase disproportionately as rpm increases. That's one reason why I suggest the use of carbon fibers over a low density substrate. The last thing you need is to fling a blade through the neighbors window!

You can easily make a variable ratio 3 Axis pantograph at home with a modest investment. You'll need one to insure consistent geometry from blade to blade. A stylus at one end and an inexpensive laminate trimmer at the other with a ball mill does it all. I bought three powerful high speed units for less than $20 each at Harbour Freight.

We use these all the time for replicating damaged two blade props. Cut the damaged blade in half. Toss the splintered part and use the remaining blade as the pattern for replication. There is more to this than what I have written but you get the idea I'm sure

You might get a better sense of what is possible by Googling "Constant Speed Props" or "Variable Pitch Props"

L.J

Hi, in addition to 130V/1A you should know: rpm and power (output) at 130V/1A, resistance of rotor to calculate rotor heating by 1 or more amps, cooling of rotor as rotor has to be dissipated by cooling, temperature limit or insulation class of rotor as allowed maximum temperature is dictated by insulation material. (Most often class F material is used allowing for 130°C continuous and 175°C short time temperature.) Then you should know the magnet material: if it is AlNiCo then opening the motor will demagnetise the magnets. If it is FeNdB there may be a low temperature degradation and rust sensitivity, if it is SmCo(uncoated) there is existing hydrogen poisoning by minute amounts of hydrogen from corroding steel. Actual limits as generator are: temperature and centrifugal force in the rotor, arcing at brushes and collector, failure of insulation by overvoltage and temperature, Need for optimum operation: commandable power consumption of load, that is reconfigurable battery stack. Or electronic inverter to make constant voltage (variable amps) and constant battery configuration. RHABE

Given the availability of ubiquitous automotive alternator and the alleged ease with which it can be modified, I find myself puzzled that this device isn' being discussed as a wind turbine driven power unit to maintain lead acid or more modern storage batteries. DC to AC inverters are plentiful which makes the transition back to usable AC fairly easy.

One mod I saw for a conventional engine mounted alternator allowed a welder to weld 1/4" plate steel with apparent ease.

100 amp alternators are common. At 13.4 volts, that's 1340 watts. That's enough to drive any number of devices with a reserve left over to charge batteries.

L. J.

I think there's a good section in the link I provided (or I've seen it somewhere) which explains why car alternators are NFG... I think they are designed to run at too high RPM

Del

Considering the low output at such a high RPM, I wouldn't consider such a motor to be practical for use as a wind turbine. Gears and variable pitch blades may help, but at what cost?

If you haven't already, please consult the following website, which provides an abundance of ideas for home-grown wind turbines:

http://www.otherpower.com/otherpower_wind.html

WindGenMan

As I acknowledged in my previous post, I do not know enough about motors to comment on the efficacy of the motor being considered.

However, regardless of the generation method selected, wind turbines need blades and if the thrust they generate is to be optimized across a range of wind velocities, some means has to be devised to alter the pitch.

The added work needed to make a fixed blade "ground adjustable" is minimal. That alone must be part of the development cycle as there is no way to predict with accuracy what the baseline pitch angle should be. Making that blade respond to an governor is simply the next logical step.

Gear reduction, if used at all, is not a challenge either.

As with all development projects, ". . . by the inch it's a cinch; by the yard it's hard"

In other words, keep it simple and make small changes until you get what you want. It takes a little longer but spares you the time lost backing up over major design flaws.

L.J.

Utility scale wind turbine manufacturers are desperately seeking to rid themselves of gears altogether due to the high failure rate and replacement cost. My only point is, the Guest would be better off with a higher output generator.

That Wind Generator site you suggested is very good!

I played there for some time and came away with a very positive experience. Were it not for the constraints of existing projects, I'd likely start a wind generator project immediately.

One thing I did notice however, was that people are being encouraged to make turbine blades the hard way.

A good prop is a thing of extreme precision. It has to be, especially if it's to be used in concert with other blades on a a common hub. It's not until you have made one that you fully appreciate the skills artisans had back on the 30's when such devices were made entirely by hand. Although the process is more automated, they still make wood props today. In fact some pusher type aircraft cannot use anything but wood props. All else fails structurally, even carbon fiber.

The time needed to make a home built 3 axis pantograph will consume less than a weekend and the investment in time will be recovered with the speed with which the first blade is made.

The benefits of fast and accurate replication will be readily apparent.

Because they do not see the RPM's, gyroscopic loads and power absorption common to aircraft props, one might get away making each small diameter turbine blade from a single plank of pine. I personally would not choose such a method but would build up a wood blade from a blank built up from thin veneers.

The orientation of the grain from ply to ply, helps prevent warpage and strengthens the blade considerably.

By skewing each veneer a few degrees around the imaginary hub, the build up allows for the blade angle to be almost built in while minimizing the amount of material that needs to be removed.

Wood blades must be thoroughly sealed with a high grade of UV resistant polyurethane to prevent changes in moisture.

There is simply too much information on the basics of blade carving to cover here. I suggest you go to the main web site of the Experimental Aircraft Association and search for books on prop making. I also would try Wick's Aircraft's site and that of Aircraft Spruce & Specialty.

I'm also confident that if you Google using some combination of the words Propeller, Carving and Pantograph, you will find the same free plans set I used to make mine.

This is a great string and I found the responses quite informative.

Thanks

L. J.

I appear to have lost the plans for the 3D pantograph that was modified to a dedicated prop carving table. That was in the 70's.

The main hinge was made up from two spherical ball joints, one at each end of the frame that held the pantograph. This one was first built as a fixed ratio unit that only replicated existing props full scale.

Since it was designated a prototype and hastily built to prove the design concept there wasn't any easy way to incorporate a ratio adjustment. However, the unit proved to be so effective, no one wanted to mess with it, even though a variable ratio pantograph would have been preferable.

A neurotic and angry spouse damaged the machine during the divorce proceedings. The judge rewarded her behavior by awarding me custody of our 10 year old daughter so the pantograph served a purpose with a much greater reward after all.

If I can ever catch up with what is already in play, I'll develop another, this time, variable one as it appears to be a worthwhile production machine for the wind turbine industry.

In the meantime here are some links to sites that will give you an idea of what is possible as well as some helpful design tools.

http://www.wood-carver.com/gemini.html

http://www.n-lemma.com/indoorrc/propcalc.htm

http://www.torchmate.com/pantograph.htm?gclid=CLer8abtxJUCFQSwFQod_gq5jQ

http://www.shopsmith.com/ownersite/catalog/sa_routerpantograph.htm

The Shopsmith unit is discontinued but gives you an idea of how some simple, low budget, router based pantographs can be made. I'd not attempt a large radius blade with a high aspect ratio on this small a machine. However, once you understand the concept, it's not difficult to scale it up to accommodate a turbine sized blade.

L. J.

Good information. Blade design is extremely critical, as is the material used. Right now, most utility scale manufacturers use carbon fiber composites which are poured into a mold and then reinforced with fiber glass and epoxy. As you can imagine, the mold pattern is a closely guarded secret. If you look at a blade close up, the aerodynamic profile changes along its length and contains a myriad of twists. I only wish some of the smaller scale turbines would follow suit. Their efficiency rating is far below that of a megawatt class machine (44% vs 52-54%), all due to poor blade design.

WGM

Hi,

I strongly agree,

the starting point should be selection of blade length (related to needed power and available mean wind velocity.

Then look if there is a motor (there is) that can be used without gears.

AC any phase count - if permanent magnet type -is suitable too.

Do you know why so often the gears are failing?

Gear manufacturing: art, engineering, machines, and practise all is highly developed.

I never heard about the ships gears failing - many megawatts!

So what is so different and difficult?

RHABE

The difference for wind turbine gear boxes is the load variance. Unfortunately, no matter how quickly megawatt class turbines are able to adjust blade pitch in response to wind speed fluctuations, inevitably some adverse load is transferred to the gear box. In addition, just the size of rotor in itself (some now almost 100m!) creates a tremendous load variance when one blade reaches its rotational apex. The top blade is exposed to nearly twice the wind speed as the lower two blades! While the low speed shaft connected to the rotor can dampen some of that load, the gearbox still winds up absorbing quite a bit of the punch.

WGM

ASI Technologies in Pennsylvania, has a patent on a new tooth design that replaces the conventional involute geometry with what I remember as being called a "convaloid" (? not sure. It's been a while since I did any design work fo them).

The advantage of the new tooth profile is that it decreases unit loading of the contact area dramatically.

This makes it possible to manufacture much smaller gears with the same power transmission capability or make existing sizes more durable.

I know ASI is working with many high profile wind turbine developers in an effort to promote this solution. Not surprisingly, ASI makes gears and gear boxes.

L. J.

Good to know. Thanks!

WGM