Mini Axial Flux ... early planning stages

[arc]

Hey-O Team,

A little background:

A number of years back I made a conversion alternator from an induction motor.

Basically, I just ground down four sides of the armature to accommodate clusters of 7ea. 1/2" diameter x 1/2" neos. With Zubbly's help I rewired it and used the starter windings as a second phase. It still works but it's been through quit a bit of weather and appears to have a slightly bent shaft now. I think I could probably keep using it as is but have the itch to build a new project in the near future.

My budget is in the neighborhood of $0-0 with an absolute maximum of $0 (I'm currently out of work and the near future looks pretty bleak in that regard).

So, if I want to do this project I'm just going to have to use what I have around and scrounge some junk to make it happen.

If nothing else it will be a great challenge and I'll have fun tryin'.

A beginning:

My greatest resource is the 28 neos that I'd like to salvage from my conversion.

Getting these off and cleaned up probably won't be easy but I read one post that said that they had used carburetor cleaner to dissolve the epoxy and said they had good luck with this method. I'll give that a try since the only realistic method I know to keep from harming the neos is by using chemicals of some sort.

Wish me luck, I'll probably need it.

I suppose there are a number of ways to use the 28 - 1/2"dia.X 1/2" to generate power but the obvious choice is probably a mini axial flux alternator.

I would love to build a larger one but it's just not in the cards right now so hopefully I can scale things down and still be successful. In scaling things down, I'm going to lose the advantage of the speed at which the magnets pass by the coils ... as with a larger diameter alternator.

One thing I do have is time, so I'll use that time to work with various configurations to try to make the best of my resources.

This is where I hope to be able to run some ideas past y'all to garner some collective knowledge and perhaps to point me in the right direction once and a while.

Goals:

I have two 6V-220Ah AGMs wired in series that provide 12VDC and is also wired up to an Aims 1250W Inverter in the house for a UPS of sorts.

I also have eight 12V-9Ah SLAs on my ebike that I usually just jumper (parallel) to the AGMs above. The SLAs provide 24V (series/parallel) for the ebike running but I have a DPDT switch so I can charge the SLA bank at 12V.

I'd like to be able to provide 15VDC (will dump or divert excess if needed for proper charge to the batteries using one of Gary's circuits no doubt)

I also have 37Watts of solar panels to blend with any power from the wind to help maintain these batteries.

Whatever alternator I build will be riding on my 21' 2-1/2" black pipe tilt-up.

Wind conditions are poor in a heavily treed area so the wind we do get is mostly gusty and changes direction a great deal. High winds are extremely rare if ever here.

An average day has gusts to 20mph so I'd like to design for a cut-in around 150 rpm, if possible and am not worried about efficiency loss at the higher wind speeds.

Here are some preliminary sketchs of some thoughts I've had so far.

It may work out better to use a larger diameter with single row of the neos but I'll start here and head there if needed.

In this plan, the coils would be backed by strips of sheetmetal wound tightly but separated with a thin membrane to cut down on eddy currents. The laminations would be set into a circular area routed into some plywood. Coils would be set in resin but I will need to learn that process.

Magnets would be epoxied in place or set in resin on a steel backing plate, probably 1/4" steel plate.

I hope to find a small trailer hub or something similar as a hub.

Thanks for taking a look.

arc

big pic

gotta watch that pixel size arc 1000 pixels wide is unacceptable here Kurt

[electrondady1]

the drawing shows a three phase layout.

28x.5x2 /3.13=8.9+.25+.25=9.4"

i can't speak to which one would give a better output

but if your willing to go single phase,

consider putting all 28 on a rotor about 9.5" dia.( disk brake rotor )

use a second rotor (no mags)for a flux return path.

both trailer hubs and brake rotors can be found in your local bone yard.

 

[willib]

Hi Arc,

Your layout looks very good , i see no problems with it the way it is.

The "casual traveler" uses a setup similar to jerry's ,(for his alt bearing) they both would work nicely for you .Jerry dosent use trailer type bearings though , not sure which will work better ,but jerrys bearings dont need any adjusting which might be a plus.

...bill

[gotwind2]

Hi Arc.

From my experience (all be it limited) it's best to go with a larger stator, 6" dia makes things very tight, if you can go up to 8" or 9" that would help.

In my opinion casting the stator and rotor aren't absolutly neccesary.

If you are located in a reasonable dry climate, zip ties (cable ties) can be used to hold coils in place. and a mechanical method of preventing magnets being moved outwards from centrifugal forces can be used, a steel 'ring' in this instance, it could also be done with a nut and bolt maybe.

e.g.

Single rotor alternators do have a place,if done properly, the alternator above has yielded me 110 watts in a 25 mph wind.

Good luck and have fun..

[Flux]

You haven't got much magnet so don't expect much.

I would go for 24 pole single rotor with a spinning second disc with no magnets. Your laminated iron circuit would need very good material for you to get good low Wind results.

Even so I doubt that you will manage much bigger than a 5ft prop even in a low wind area. You didn't give the prop size for the motor conversion.

Unless you are using pvc or something then 150 rpm cut in is low for 5ft and will restrict your power out. 250 to 300 rpm cut in would be a better choice for a sensible 5ft prop ( perhaps keeping nearer 250 for a very low wind region).

Your present layout would indeed work but unless you can find an exceptionally good source of laminate material I suspect a lot of your output will go in iron loss.

Flux

[arc]

Here is the single row of 24 Neos and 18 Coils.

I have no problem of changing the diameter, it will somewhat depend on what I find around or can get cheap. The diameters shown for both the double row version above and this single row version are just a starting point and would be the smallest configuration for the number of neos I have.

I know very little about coil shape and size but I was reading up on some of Ed Windstuffnow's diagrams for what works well for magnet spacing in relation to coil leg width. I also found (and since lost) a guide somewhere on the forum that showed the O-scope wave shape for various coil hole sizes in relation to magnet size. It appears that a hole close to magnet size produces a nice clean curve with no low point in the middle. It all made a lot of sense when I read it.

So, once again, the pics below are just a starting point and show the smallest diameter that takes into consideration most of what I tried to describe above here.

I really appreciate all of your comments and suggestions, they will be of great help in getting me rolling in the right direction. I especially appreciate the suggestions related to making do with what's at hand or at least "scroungable". (durn spellchecker didn't like that one much. Folks that write dictionaries must not know much about scroungability factors.)

So thanks tons for the comments so far, they are appreciated!

[arc]

I'll have to study up to see what advantages there are to the 3 phase vs Single phase as it relates to this situation.

Depending on what I find out, using all 28 neos would make a lot of sense. Considering the size of these neos I need all of them I can work into the equation. I may be able to latch on to a brake rotor or two from a guy down the street who does towing and mechanical repairs. He probably chucks used ones in the scrap pile.

Thanks for the suggestions!

arc

[arc]

I'll do some user searches to check those out.

Thanks Bill,

arc

[arc]

Hey Gotwind,

If I could get around having to do the resin/ glass thing I would be literally jumping for joy. I'm allergic to the resin (or was with one type) and have avoided learning anything about working with glass all my life. Great suggestions here, a band could be brazed end to end, heated and dropped over a rotor without too much difficulty.

As the lightbulb lights up!

Thanx,

arc

[arc]

Hiya Flux,

I'll be sure to keep my expectations in check. If I can supplement my humble solar (a whoppin 37 Watts) to help keep my AGMs topped off I'd be a happy camper. I mainly need the Voltage, anything over a trickle of Amps will be frosting on the cake.

I'll always have my Iota 15 Amp charger standing by, regardless of how cooperative the weather and conditions may be.

I'll heed the second rotor advice, my current blades have a 63" diameter, so about 2 sq meters windswept area. 3 blades vs. 5 blades is up for debate, there are currently three blades on the conversion. I'll carve some wooden blades, PVC is inexpensive but I'm ready for some real blades this round. Nothing too fancy but they will have a twist and be a scaled down version of one of the popular blade designs suggested throughout the forum.

Appreciate your input,

arc

[willib]

I ment to add earlier that a bicycle sprocket may be just what you can use for a pair of rotors.

also adding hard drive neos sure couldnt hurt when on a budget( for the second rotor).

[ghurd]

If you have some tools, I think you will find a second rotor easier than (or the same as) laminations.  

The force of the attraction from the neos to the laminations was (for me) a seriously underestimated PITA.  Stress on the small "scroungable" $0 non-automotive-type bearings, pull on the laminations, pull on the plywood the laminations are epoxied onto, etc.

G-

[kurt]

hiker, you been around long enough to know the rules about the pictures come on man.....

[hiker]

sorry about that--thought i had those all resized......

[arc]

Hi Kurt,

I started out with pics 640 wide on all of these, when I do a properties on them now it reads "640px × 462px (scaled to 719px × 519px)"

Not sure where the "scaled to" part is happening but I do realize that there are still quite a few folks here that have dial-up, so I'm always careful to resize my pics.

I used Gimp to resize all of my recent pics to the 640 wide max, can you check to be sure that the 1000 wide that you mention is not incorrect?

If they are showing up larger, I truly apologize and will do what I can to insure that they are correct in the future.

Let me know what you find out on the actual size, I can't fix what is showing up to me as the correct size if they change when I upload them.

Open to suggestions ... I use Linux (Ubuntu) but that shouldn't make any difference, a pixel should still be a pixel.

Thanks (and I'll make them smaller yet if needed)

arc

[arc]

Kurt,

Found the culprit, sorry about that!

Took some re-uploading and renaming but I got it changed.

You were correct ... just slipped by my radar.

arc

[arc]

Hi Willib (Bill),

The bicycle hub might just work if I keep my blade weight and stresses down to a minimum. I'll carry that thought with me as I proceed.

Thanks again,

arc