New Wind Turbine Builder?

[cognito]

Good day to all.

I've acquired some 3/4 X 1/4 N48 disc magnets, and think it would be a good experiment to try with my nephews to build a small wind turbine with them as a first project.

I have 24 of the magnets. Also have some gyrocopter blades, which are flat one side, airfoil on the other - 2 blades, about 5 feet each.

Looking around and reading, I thought I would try a dual rotor alternator design with 9 coils in a 3-phase star arrangement, and rectify this output to charge my 12 volt emergency power system (currently topped up with a small solar panel). Shunt off to heat water with any excess, I'll build the controller later...

I am looking for some guidance on coil size, shape, and turns, stator size, and rotor size and magnet spacing.

Any info that could be provided, or links to info, would be greatly appreciated - and I thank you in advance!

[Boondocker]

Start with research.  One of the key concepts with wind turbine is matching the alternator and blade.

I've found this book to be a great introduction to learn the wind turbine basics.

http://www.forcefieldmagnets.com/catalog/product_info.php?cPath=21_29&products_id=28

Do a search of the board and will find detail discussion like this i.e. coils:

http://www.fieldlines.com/story/2006/11/7/223838/528

Diaries of board members are full of projects to draw inspiration and knowledge.

If you get stuck understanding something, post a question.

Good Luck

[Flux]

Not enough information on the blades to give any help.

Is each blade 5ft long or is it 5ft diameter. If each blade is 5ft long you have no chance with those magnets. If it is 5ft diameter and the pitch and solidity are in the right region then you may be able to do something.

What is a gyrocopter? is it the thing that I know as an autogyro, in which the blades freely rotate without mechanical power. If it is that then the blades are basically suitable from what I can remember but would be too big for these magnets. If as I suspect the section is constant throughout the length and you have no other use for the blades then if one is 5 ft long and you cut in half and mount at suitable angles it should make a decent 5ft prop.

Most likely the aviators will be able to give more details on these blades.

Flux

[cognito]

Thanks for the comments and the info, it is proving helpful.

The 2 blades were to be used on a 1/4 scale mockup (to be used in training) for a gyrocopter/autogyro, in fact they are cut-down full-size gyrocopter blades. They are each 5 feet long, 5 inches wide, about an inch thick at the top of the chord, constant chord from tip to root. Flat bottom, rounded leading edge, basic lifting airfoil. They appear to be a high-quality, professionally machine-made 3-section (leading edge bonded to a centre section bonded to a trailing edge) laminated blade, made of a tough hardwood. The roots have been machined flat for mounting into a hub, with "Zero" angle-of-attack built in. They are quite rigid, but have some flex. I can cut them to whatever length I need. Modifying the airfoil would take some work, but could be done...

I've read a fair amount on sizing and winding the coils - and remain confused... I've learned that this is caused by having not read up to the "critical mass required for understanding"... I'll keep at it.

I see in one of the Instructions I downloaded (from windstuffnow), illustrating the construction of an alternator with triangle-shaped magnets, that the gentleman has 12 magnets per each rotor, and 9 triangular coils wired 3-phase star. I think this is the configuration I'd like to try to build, with the exception of using round disc magnets.

So - what shape/size coils, and how many windings per coil, size of the wire, and the spacing for the magnet and coils are the things yet to be determined, at this very early stage of the design.

Simple! (That's a joke...)

I'm not looking for huge outputs, just a proof-of-design, and to develop the skills required to build the next one...

Thanks again.

[Flux]

You are a bit short of magnet but I think you could manage something with a prop about 5ft diameter.

Your 12 magnets should go well on discs about 9" diameter and about 1/4" thick.

Use 9 coils and either keep them round or you can squeeze them up into an ellipse. There is no virtue in masking them triangular. Keep the holes in the centre about 3/4" but you can squeeze the radial dimension down to about 5/8 to gain a bit of winding space.

You will likely need about 120 turns per coil. Try about #16 wire and wind the outside diameter so they just touch when assembled. See if you can keep the thickness down to about 3/8" so it will fit into a magnet gap of about 1/2".

You should get a cut in speed round 300rpm. If you cut one of your blades in half and make a 2 blade prop about 5ft diameter it should be near enough. You will need to mount the blades flat face forward and with an angle of about 5deg. You will have to alter the mounting end to get this angle and you will need to adapt the other cut section to mount at the same angle.

You could have used  part of the other blade to make it a 3 blade prop but it will be too slow for the quantity of magnet you have. Three blade props are preferred but in the smaller sizes you will find 2 blade perfectly ok. It may jump a bit during yaw but it is not a big issue on small machines.

Look through all the past stuff to see how to star connect your coils and how to interpret the results from a test coil.

Flux

[cognito]

Again, I thank you for your input.

After a fair amount of reading, understanding is starting to creep in...

After some further scouting/scrounging, I've come up with a 10 pound roll of #18 magnet wire, a 42" 3 bladed hub with "pusher" blades from an ultralight gyrocopter, and a 5 gallon bucket of brand new ball bearings of various sizes, mostly 1/2 and 3/4 inch.

Amazing the things people accumulate, then discover they have no need for, yes?