stator rewind for a dirtbike...

[birdhouse]

hey all-
i have a honda xr 600 dirtbike that is really lacking in electrical power.  i've read about rewinding the stator here:  http://www.all-offroad.com/DirtBikes/TrailTips/XRStatorRewind.html 

the stator has twelve poles.  two are already taken for ignition and i don't want to screw with these.  only four of the remaining 10 poles have wire on them.  the idea is to strip off the existing 4 poles and re-wind all ten poles with a continious 18 awg magnet wire switching the direction of the turns with each coil.  32-34 turns per pole. 

i am unsure of what type of magnet(s) are used in the flywheel but have thought about beefing it/them up as well. 

this all seems so similar to building an axial flux, so i figured i'd post my plans and see if anyone had any info they thought might be good to know to make this re-wind easier or better. 

i understand i'll have to coat the new windings with high temp epoxy, and probably replace my rectifier/voltage regulator with a beefier one. 

any thoughts are totally welcome!

adam

[hiker]

keep the stock mags..dout if you would see much of a incress in power out put...
coils should work out for you[are they going to be the same number of turns as stock?]

[Ungrounded Lightning Rod]

Sounds like a plan.

Wind your new ten-pole-in-series winding with thicker wire and so the total number of turns on the ten pole pieces is the same as the total number of turns on the original four coils.  That will give you the same (unloaded) generated voltage at any given RPM.

Your available output current will be increased in proportion to the increased cross-section of the wire - up to at least 2.5x the original output current.  (Beyond that the mag field might be too wimpy to keep the voltage up.)

Going up (down in AWG gauge number) by 4 multiplies the cross section by almost exactly 2.5x.

Yes you may need a beefier regulator to take advantage of (and perhaps survive) this extra available current.

[Flux]

The main thing limiting output of these type of pmg is leakage reactance.

By using 10 coils instaed of 4 you should reduce this reactance but in the end you can only gain more current by reducing turns and compromising the low speed end. You can get a lot more power at the fast end with a reduction in the number of turns, that is the only way to gain much.

The limit with air gap machines is resistive but these salient pole iron cored pmgs are dominated by reactance and they go into constant current mode when the reactance becomes greater than the resistive bit. The reactance rises with frequency and so does the emf so you reach a constant current.

You will have to play with turns to get the best trade off.

Flux

[birdhouse]

thanks for the replies!

i don't know how many turns are used on the original poles, but will find out when i strip off the four original poles.  i was wondering if i could get maybe 17guage wire and still have it fit withing the winding space.  sounds like that would be even better. 

i think the original stator puts out around 60-70 watts, and apparently folks who have done this re-wind have gotten upwards of 150 watts.  still need to pick up the wire, and have a super busy week coming up followed by a long weekend away climbing, so i probably won't get to this for a week or so.  i'll let you know how it goes! 

adam