Trials, tribulations and ponderings as I build my first dual rotor

[WoodSpinner]

Hi, I've been tryint to build my first dual rotor alternator and keep running into problems just getting started.

I guess I should start at the beginning, I have some 3/4"x1/4" neos prolly n35s that I planned to use in a 12/9 3p alternator. 

I started by cutting some thin steel for the rotors with a torch but they twisted all over the place, waste of time.

Then I cut some saw blades to 8.5" diameter and got a friend to weld on some locking collars for the shaft I chose, the saw blades cracked almost immediately, another wasted effort.

So now I'm thinking of going with some 1/4" mild steel plate but before I spend any money on them I have some question in my mind as to diameter to go with, the spacing at 8.5" seemed adequate but was wonding if I go with larger diameter rotors maybe I can use larger coils hoping for better output or go with larger wire or both, but is there a breakover point where the spacing being too large is detrimental to output?

John

[WoodSpinner]

Ok, so I finally got the rotors made, and my magnets epoxy'd in place.  I mounted them on my woodlathe and have started making test coils, at 100 wraps of 19g wire, I'm getting 2.68vac or thereabouts. and one at 88 turns same wire that gave me 2.3vac or thereabouts.

I've been trying to use http://www.alton-moore.net/wind_calculations_english.html to figure out a prop/alternator combo but I'm kinda of at a loss, I'm willing to go up to a 6' rotor in an attempt to not have it run at mach 5 all the time, my target originally was to make a piece of yard art that would light some lights on the 8' tower as it spun, but its kinda looking like it will either make too much electricity for the task,meaning I should use it to charge the storage batteries on the rv I live in and turn off the builtin charger or never hit cutin without stalling horribly. 

Any advise you might have would be very much appreciated.

[ghurd]

The test coil figures sound correct compared to each other.
Need to know the RPM for anyone to offer advice.

I see a few oxymorons.
Yard art and 6' rotor.  6' rotor and 8' tower.

Then Mach 5.
A larger diameter rotor will turn 'relatively' faster because it is underloaded.  Unloaded can spin twice as fast.
I think TSR is what causes noise.  My best guess is under 6.5 is quiet, over 7 can be noisy.

Yea, that's too big a diameter for a few small direct drive incandescent lights.  They will pop.

"turn off the built in charger"?
No, not for common built in chargers.  My camper has a simple transformer with no regulation at all.
Common built in chargers reduce the amps as the battery voltage increases.
If the turbine is making good power, it is that much less power that comes from the built in charger.
G-

[WoodSpinner]

Duh, sorry, brain fart. I should know better than to give no base rpm, the tests were run on my woodlathe at 500 rpm acording to the lathe, I cant attest to accuracy. as to the 6' rotor, using that calculator I was seeing smaller rotors not come into any power until they hit 500 rpm or more and was concerned that I would be runing the mill at extreemly high rpms on gusty days. I guess with an 8' tower individual blades aught not to reach my head so maybe I should just concentrate on building a sturdy machine and avoid letting it run on exceptionally good wind days, oh, and I had planned to light the lights in sequence and am considering using those led's you told me about, maybe going with yellow then red then a dump load.  oh, And its nice to know I wouldnt need to turn the inverter off,
thanks
John

The test coil figures sound correct compared to each other.
Need to know the RPM for anyone to offer advice.

I see a few oxymorons.
Yard art and 6' rotor.  6' rotor and 8' tower.

Then Mach 5.
A larger diameter rotor will turn 'relatively' faster because it is underloaded.  Unloaded can spin twice as fast.
I think TSR is what causes noise.  My best guess is under 6.5 is quiet, over 7 can be noisy.

Yea, that's too big a diameter for a few small direct drive incandescent lights.  They will pop.

"turn off the built in charger"?
No, not for common built in chargers.  My camper has a simple transformer with no regulation at all.
Common built in chargers reduce the amps as the battery voltage increases.
If the turbine is making good power, it is that much less power that comes from the built in charger.
G-

[WoodSpinner]

Well, I've decided to go with a 3' rotor with a tsr of 6 and a cut in of 7mph wind.  I played with the calculator modified by ChrisOlsen found here http://fieldlines.com/board/index.php/topic,143174.30.html  . I'm gonna try following what it says and and using the blade calculator found here http://www.alton-moore.net/wind_calculations_english.html  and see how it turns out.  Wish me luck.

John

[WoodSpinner]

While winding my coils I ran out of the 19g wire I was using, will there likely be a problem running 22g 2 in hand for half the coils or do I need to find some more 19g?

John

[ghurd]

Myself, I have no idea about the coils.
It sounds fine to use 2 in hand #22 (it is the same as one #19).
I think it will fit in a bit smaller area.

The 3' dia rotor and 500RPM sound a lot better.

Calculators just calculate.  Experienced intuition is often better.
I have no reason to say that except other people guesses were closer than calculators for a lot of my stuff.
G-

[WoodSpinner]

Myself, I have no idea about the coils.
It sounds fine to use 2 in hand #22 (it is the same as one #19).
I think it will fit in a bit smaller area.

The 3' dia rotor and 500RPM sound a lot better.

Calculators just calculate.  Experienced intuition is often better.
I have no reason to say that except other people guesses were closer than calculators for a lot of my stuff.
G-

Thats what I was thinking, that 2 in hand#22 would be the same as the 1 of #19.  I got a total of 5 coils out of the #19, I do have one more alternator from a car, thats where I got the #19, from the rotor field coil. I'll see if the last alt has #19 before using the #22 for the rest of the coils.

If I do use the #22, do you think I should try to intermingle them with the others rather than have one entire phase out of them.

Thank you
John

[ghurd]

I figure it would be best if all the phases matched.  At least as close as possible.
If one phase is very much different than the other 2, it will vibrate more.
Go with intermingled.
G-