12v dual rotor alternator design

[Tony h]

Hello,im building my first wind turbine and need some advice.i have 50 neo 25mm x 10mm x 3mm magnets.I plan to stick 2 mags together to make a 6mm thick one and use 12 of these on a 5/6mm mild steel mag rotor for a duel rotor 12 pole/9 coil(3 phase)machine.I want it to be as small as possible but still want the best as possible from magnets i have.Ive decided on 150mm diameter rotor disks which rules out using a car hub/bearings set up.I have looked into using two cast 4bolt flange bearings on a 15/20mm shaft but the thickness of the bearing/housing once fitted onto discs and facing each other will make the air gap between disks for stator about 50mm which is to big.Ive read air gap should be 1.2 x magnet thickness,ive also read that the bearing housings should be on same side as magnets on the discs,can i put one on opposite side to mags on one disk?so the questions i have are

:how thick should the stator be for above set up?

:how can i solve bearing/hub/shaft set up problem?

:am i right in having a 150mm diameter mag rotor for these magnets?

:max total blade diameter(including blade hub) of 1 meter,is this big enough to work?

 i hope this makes sense,any and all advice welcome

thanks,

newbie Tony

[electrondady1]

it's good to have as much space between mags as the width of the mag.

50. /50 spacing
    
10. mmx2x12=240 + 25mm +25mm =290/3.14=92.3mm circumference required.
    
    

the thickness of one mag is usually considered optimum for stator thickness.

but to be practical one must use a stator thickness that will give sufficient strength.

plywood is often used for a stator mold and that comes in specific thicknesses.

try to use something between 6mm and 12mm

i can't understand what your bearing setup is or why it dictates your air gap ?

[Tony h]

hi,thankyou for your response,i thought stator should be around 6/12mm thick just wanted to make sure.the bearing set up and how all moving parts attach to shaft is where im stuck.shaft will be welded to framework with furling device and yaw bearing ect on it.then i need to attatch bearings and housing onto magnet rotors and blade plate.i was going to use 4 bolt flange bearings and put them on the same side as mags,on each rotor.because the bearing and housing is about 35mm thick,when i face the magnet rotors together with bearings facing each other there will be a 55mm(at closest)air gap between magnet rotor disks,to big for my mags and stator,the magnets will be to far away to work.could i just use two housed bearings,one on rotor plate and one on magnet rotor closest to framework which means the other magnet rotor will only be joined with the threaded rod and not a bearing.this will allow magnet rotors close enough to stator to work.would this be ok?also,what do i put on the end of the shaft to stop all the moving parts falling off?i hope this is a bit clearer.im trying to work out how to do a diagram and add it to show my problem.all advice welcome

thanks

Tony

[electrondady1]

i'm mostly into vertical mills but i have picked up a lot while studying p.m.a's around here.

you were describing a method were the shaft is rigid and the prop /alternator turns on bearings.

but there is an alternate method were the shaft rotates and the alt and prop are solidly attached to it.

i think if you use "pillow block" bearings  instead of those four bolt flange type

you will be able to make the thing work .

place both bearings on the shaft on one end and that will free up the other end for the alternator and prop.

there are lots of examples of this if you google the board.

the place you buy your bearings will have little collars with set screws to keep every thing from falling apart.

good luck!

 

[Tony h]

thanks for your responce,that is definatley an idea.ive been stuck for a solition for a while and this could be it!more reading needed.

thanks again

tony

[electrondady1]

ok,i made a mistake

i don't want to steer you wrong

10mm mag+ 10mm space x 12=240mm /3.14=76.4mm dia. at the inside

add 50mm for the length of the two mags gives 126mm outside dia. rotors

[Tony h]

hello again electrondaddy,thankyou for your help,ive decided on mag rotors of 140mm diameter,looking at your calculations this leaves me alittle room for monuver.i can only keep them at 140mm if i use the spinning shaft system you suggested,because of only being able to find bearings/housing with smallest size of 76mm length 76mm width bolthole pcd 55mm.ive been looking at posts about the spinning shaft idea and am yet to find any info on how i will attacth mag rotors and blade hub to shaft.is threaded rod ok to use with pillow block bearings?if so i can then just tighten nuts on shaft against rotors to keep them in place and ajust air gap.will this be strong enough?if i cant use threaded rod for shaft i dont no what to use to attatch rotors to shaft(apart from welding)so they can be moved for air gap and placing stator in between them.any ideas?or do u no of post that will help?

thank agaian

tony

[electrondady1]

when i got started i used threaded rod for an axel shaft

you might as well use it up

check out a guy named "hiker"

also "wild in Alaska " for he built several  with threaded rod and pillow blocks

you can fill the threads with some sort of plastic to give the bearing something to live with.

i am working on a vertical today two rotors on a live axel shaft 5/8"dia .

the rotors need a center hole that will allow then to move on the shaft

then you need a center section disk that has the same hole and two parallel faces.

 i am Canadian so i use a hockey puck with a hole drilled in it.

try some plywood  of the proper thickness.

you want the stator to be nice and flat and a few millimeters less than the space

between the mags.

i say that because with this method there is no adjustment

and if there is interference between the stator and mags you need to add thickness to the stator which requires you to pull your rotors apart.

[electrondady1]

sorry, i meant add thickness to the spacer.

[Tony h]

the stator needs to be 8mm thick,the gap between mags on each rotor 10mm,the spacer needs to be width of mags + air gap to stator + stator.if i make the centre hole on the mag rotors just big enough to slide on shaft,then keep it all in place by tightening nuts in outside of mag rotors,will it sit centrally enough on shaft when tightend,to spin ok with a bit of balancing?this is my plan thanks to you electron!ive now finished final drawing/design of alternator,rotors with exact mag placement,exact stator dimensions,i no how much room i have for each coil but not how many turns of wire(i have 18awg)untill i do some tests once i have mag rotors on shaft.now i can order discs to be cut and get pillow blocks.im finaly getting somewhere it feels like.i looked at posts you suggested,good info,thankyou.i will post some pictures with my next problems to solve(there will be some im sure). another question?would a 4 bolt zinc plated steel bearing house affect magnet flux on rotors  because ive found a small bearing and housing but i am sure ive read that zinc plated steel causes probs?do you no?

thanks again :]

 tony

[Tony h]

canada is a nice place to be in the world i reckon,i would swap it for london uk  anyday

[ghurd]

Be nice to include some white space breaks.

Things get less jumbled.

G-

[Tony h]

white space breaks it will be from now on,i no its hard to read otherwise

sorry