Finding the right generator

[Thaelin]

   Concerning Gen heads for wind, there are many makeups to choose from. I have settled
in on the 12mag/9 coil setup. To reach fair output, it seems to be necessary to hit 700 rpm
with it.
   Now what would happen if you had a wheel with 24 magnets on it and two sets of 9 coils
in two arcs on both sides? If both sets were wired seperate but outputs together for double
the amps, still mean the wheel would have to only travel one half the speed?
   That would make the wheel bigger, but it would only have to go 350 instead. I have a bike
wheel that had 48 slots between the spokes I am thinking of mounting two metal rings on
so as to put 24 magnets on both sides for a total of 48 and run the coils in a half circle mounted
on both sides and running in the middle of the mags.

   Any comments here?

thaelin

[capthook]

Hi Thaelin -

One implementation of the  12mag - 9 coil setup is in the axial flux dual rotor design.
The idea of the dual rotor is eliminate iron in the stator and then maximize the flux in the airgap between two rotors of magnets.
If iron is used (should always be so) as a backing for each rotor, the 'magnetic circuit' is completed - boosting flux.  (the flux from the backside of each magnet is 'channeled' to flow back through the adjacent magnet and back through the stator)

The problem with a single rotor/dual stator design is the incomplete magnetic circuit.
One would think that putting coils next to BOTH faces of the magnet would offer superior performance - but that is not the case.

I have just completed my first axial flux dual rotor build. (Hugh Piggot style design)
1. 12 mags 9 coils
2. .75" x .5" N42 mags  :  1/4" steel rotors
3. 500 turns #24 AWG coils .75" ID x 2" OD x 7/16"
4. airgap from each rotor to stator 1/8"

The magnets were taken from a build I did 2 months ago of a single rotor/dual stator design like you describe.  The coils had an iron core.

Comparing the two:
1. The dual ROTOR generated TWICE the power
2. The dual ROTOR resulted in around FOUR TIMES (or more) LESS drag. (no iron in coils)
(so at least 8x better performance)

For a long time I was of the notion that putting coils on BOTH sides of the magnets would be best - even though I'd been told it was not so as the 'magnetic circuit' was incomplete and thus inefficient.

Having now built BOTH designs - I can say that a DUAL ROTOR is SUPERIOR in many ways over the dual stator.

My next build of this design will use larger magnets (2" x 1" x 1/2") , 16 mags 12 coils with larger wire (#18 AWG?) and 1/2" steel rotors.

[Thaelin]

    I see I was incomplete with what I was trying to say. I am looking to put
two metal rings, one for both sides of the stator. The magnets will be placed
on the inside of both rings so that they face the stator.
    I see tho that the two rings will have to be joined somewhere for the flow
to happen. Guess I could put small metal pieces across the back of the rings
so to complete it.

    As I am not going to be powering this by wind prop, I need to maximize the
low speed output as much as I can. That is the reason I am considering this. I
just wished I had drawing software that I could put down what I see in the head.
It frustrates me to no end when I cant put my thoughts to action.

The beat goes on.

thaelin

[terry1094]

The Fisher Paykel washing machine motor makes a good generator.  Here is a complete detail plan for a windmill from downunder:

http://www.thebackshed.com/windmill/fp2a.asp

Elsewhere,

http://www.watchtv.net/~rburmeister/smart.html

others recommend grinding the edges of the cores of the electromagnets to reduce cogging.

Terry

[Thaelin]

  Thanks Terry:
   I believe I saw that vid of one hooked up. I must stress again tho that this will not be
a windmill setup. It will be a Gravity Wheel that is running it. The only kick back I have
is it must be a low speed unit. My latest test shows I have ample torque and can most
likely do  a six to one gear up to the head.
   I have to get another pair of weights yet and a drive belt that is the correct length. I
really only need to generate 60watts over the needs of the wheel to charge up the batt
stack.

thaelin