A radial design

[Lumberjack]

I had an idea for a radial design that might work.

The primary magnet core is made from steel round stock, center drilled to the shaft diameter and having indents milled for each magnet on its outer surface. A 3" core might support about 4 poles and a 6" diameter should support up to 9 - 2 inch wide magnets. The core length can be adjusted to allow for longer or multiple magnets. (IE each pole might consist of four 1 x 2 inch magnets and used with 10 inch long coils.)

The stator would be constructed from 4 or more plastic plates possibly cut from plastic cutting boards. The outer plates would be cut to support the core/rotor bearings. The inner plates would have a hole cut slightly larger then the core. The inner plates would then have cutouts to wind the wire on. All four plates would be held in position by all-thread once assembled. One or two middle plates might be needed to help keep the wires in place. A thin layer of teflon sheet might work to keep the core magnets from catching the wires.

A secondary idea for the stator would be to wrap the core with wax paper and glue each coil to the outside of this. once all the coils are placed a resin could be used to lock the coils in and allow it to be cast after the core was removed...

It looks to me that the core needs to be made first and the stator second so that the stator can be adjusted to suit the final dimensions...

And now the hard part, finding a large steel slug about 4 inches round and 8 inches long that I can machine.....

[dbcollen]

Do a search for "Radial Air Core"  or "RACA"

it is very similar to what you describe.

Dustin

[oztules]

Hero of the tinkerers windstuffnow has a page dedicated to this kind of design

http://www.windstuffnow.com/main/radial_air_core_alternator.htm

........oztules

[Flux]

Yes it will work but I really can't see why anyone would want to do this no more than I can see any logic in the single magnet disc axial with no return flux. There is some case for doing it as an axial to use standard cheap magnets rather than odd smaller ones for dual rotor.

The axial version is far easier to build and you can adjust the cut in speed by simply altering the clearance between magnet rotor and stator. Once built you are stuck with the radial if your cut in is wrong. The thing is a pain to mount physically with windings around the outside and you must have no solid metal in the region of flux linkage.

It makes more sense to build the equivalent of a dual rotor this way with magnets inside and outside or with magnets in a drum on the outside and a spinning steel cylinder inside.

Before the days of neo it was virtually useless to build things like this so I can't see the logic of using neos in very poor designs where it costs more to get the same output. Everyone to his own choice as always.

Flux

[Lumberjack]

Thanks, I must have missed that page.... very helpfull in some ways.

[Lumberjack]

Some interesting points flux....

Why? dual rotors are expensive but more impotantly I suspect the cause of most of the failed gennys here is largely heat which would not be as bad a problem on this design. This design scales very easily and creating a more durable genny is also a consideration.

You are right in that the design will not allow for any adjustment after it is built. The only way to change it would be to tear it apart and rewind the coils. I do not see that it will be any more difficult to build then an axial or more expensive for equal power output. I would have to build a small one to test so that I could get an idea of what a large one will cost.....

<shrug>

[WXYZCIENCE]

Lumberjack, Excellent idea! The RACA is one of the best designs that I have ever built. Think outside of the box I have always said. Here is a Link... http://www.fieldlines.com/story/2006/10/24/8145/8619


Joseph.

[Flux]

"Why? dual rotors are expensive "

Which bit is expensive? if it is steel discs and you can't produce them yourself then perhaps you are right. If you include resin then that also adds to the cost.

If you are thinking in terms of what I consider the expensive bits, magnets and copper, then you will not produce a cheaper machine by using open magnetic circuits.

As for the cooling, depends on how you mount it and what protection you give the coils.

For a given cost of copper and magnet your open flux design will have a lower efficiency and to maintain the same heat then you will get less out than an equivalent dual rotor. You can always build anything efficient enough not to over heat with any design if you want to but you will need to include serious inefficiency somewhere in the line to avoid stall if you want to directly connect it to a battery. The only way to include the loss in the alternator is to adopt cooling methods that can dissipate that crazy loss. Your idea may be a bit better than a dual rotor but if you do other things to make it robust you will be little better off.

As I say everyone has their choices as to the best method, much depends on local conditions and availability of materials and facilities. This method will produce a good machine with good low wind performance but in the hands of most people will not be the cheapest or most convenient. You alone must decide.

Flux

[gizmo]

Hi Lumberjack

You might be interrested in some research we did in Oz on the Seeley motor. A lot of our windmills are based on the F&P Smartdrive motor, but about a year ago the Seeley motor caught our attention. Its a radial design, with magnets on the outside. See the picture. Behind those coils are steel laminations to complete the magnet circuit. The design is cog free and efficient, but unfortunately the plastic used is very weak and the Seeleys were proving to be a problem from a mechanical point of view. I think a couple of windmills were built using the Seeley, but the F&P is a much more robust unit and is still the best pick for us.





I think it would be possible to make a efficient windmill alternator based on the Seeley design. A car/truck brake drum could be used as the magnet hub, just add the magnets. The stator design could be based on Ed's work or the Seeley unit. Laminations could be insulated fencing wire wound around a timer/plastic former.

The advantages are cool running thanks to the the exposed winding, easy rewire or reconfiguration, and you could also wind out the magnet hub to adjust the cut in speed, just like spacing out the disk's on the axial design. It would also elliminate problems caused by overheated and warped stators in the Axial design.

I think the radial design is worth considering

These links show some discussion and photos of the Seeley motor.

http://www.thebackshed.com/windmill/FORUM1/forum_posts.asp?TID=585&KW=seeley

http://www.thebackshed.com/windmill/FORUM1/forum_posts.asp?TID=594&KW=seeley

Glenn

[oztules]

Yes Glenn, I had a bit of a fiddle with these in a stronger guise here as well. Possibly the only solid one built so far I think. Dennis has it now.

Link is here if you want to ponder this style of construction. It may help to make an outer drum as Flux was alluding too.

The draw back with these particular ones was the high impedance output 15ohms in  star . A transformer or PWM would be required for these particular stators

http://www.otherpower.com/images/scimages/5171/seely.html

Have fun with it I did.

........oztules

[Flux]

Yes this is the way to do it, the magnets don't fly off and you have a closed magnetic circuit with the iron core, a far cry from the open flux idea proposed with all the problems of keeping magnets on the outside of a cylinder rather than inside.

I have built several of these using neos, the biggest does about 1.5kW at 400 rpm, starts in about 3 mph wind with 10ft blades and is about 70% efficient at 1kW. It is matched to low winds with a boost converter and starts charging about 6 mph.

Not something that I would attempt without a lathe but if you are lucky you might find all the bits to do it without machining. I used the outside of a motor core for the laminated core. Adopting the wound wire idea would give you more scope to match the dimensions to a vehicle brake drum.

Hugh Piggott originally used this type of construction but I think the constructors had difficulty finding motor cores to suit the brake drums. He moved away to the axial design as it is easier to build with little facilities.

For those who can machine things then the radial has far more going for it than the axial construction but with a lot of facilities I would steer clear of radials. That includes motor conversions, very difficult without a lathe.

That Seeley thing is the correct concept, but it looks so bad mechanically that I suspect to would be better to start from scratch. The concept is much better than the F & P, nothing about which inspires me, but if they are cheap they must be tempting to someone.

Flux

[Flux]

That should have said  " without a lot of facilities I would steer clear of radials"

Flux

[Lumberjack]

engineering brushes would also be a problem for most.....

[oztules]

these are brushless alternators... if thats what you are referring to.

[gizmo]

The concept is much better than the F & P, nothing about which inspires me

OK, I'll bite. Why dont you like th F&P.