Wood A-X problem?

[farmer56]

 I recently built a wood A-X and mounted it on a 30ft tower (Not the tallest but beats having nothing). Since I usually only see about 10 mph or 15 mph winds, I was only hoping for about 50 watts. I built the alternator to instructions using the same magnets and AWG 18 copper wire. When completed, I spaced it with a CD, and put a 5 foot two-bladder prop on it. The prop was 3 1/2 inches at the base and 2 inches at the tip at carved out with 5 degree tip and about a 10 or 14 degree slope at the base. After a few days free wheeling it on a 20ft test tower I saw 19 AC volts max on a fairly windy day and about 7 or 8 volts in a fair wind. I then built a 30ft tower and hooked it up two cells of a forklift battery which measure 3.87 vdc and tested amperage with a multimeter. After a few days of unusually low wind The wind finally picked up a bit, (about 8 mph is my guess) but I only saw about .9 amps out of the windmill. this means that at 4 volts and .9 amps it only produced 3.6 watts. What is wrong? Or is it that there was too little wind?

[kurt]

mite be stalled at 4v its designed to run hooked to a 12v battery not a 4v battery. man you could not have picked a more ancient design if you tried that design is like the stone age of the axial alternator 

[farmer56]

So even if you put it on say 10v or 12v, the benfits gained from higher speed and no stalling will overcome the losses of not harnessing low speed winds?

[kurt]

another thing that is a single phase alternator the coils need to reverse every other one around the stator if it is not right it would explain your low voltage maybe someone else can explain it better been so long since i thought about single phase i forget how to explain it sorry.

[farmer56]

another thing that is a single phase alternator the coils need to reverse every other one around the stator if it is not right it would explain your low voltage maybe someone else can explain it better been so long since i thought about single phase i forget how to explain it sorry.

Do you mean by reverse that you should hook the in wires to in's and out's to out's? Or are you supposed to flip the coils upside down?

When I wired up my alternator I simply put all the coils in the same direction, with the start of the coil and one side and the end on the other, the hooked them all up with the in's to the in's, out's to out's until I had two wires left, of which I draw of power.

[farmer56]

Could it be that the prop is too big? The one on Otherpower was a 4 ft. I put on a 5 ft. prop. Would this lower the prop speed by any significant amount?

[DanB]

I hope the stuff we've done more recently doesn't come back to haunt me as badly as the stuff I did that long ago ;-)
The 'wood axe' was a fun little project and it did seem to work surprisingly well on the front of my truck when I drove it down the road.  That said - the steel laminates behind the coils like I did that, and all the wood was probably not wise and the single phase alternator is not something I'd ever do again. Hopefully there is a sort of 'warning/disclaimer' at the top of those old pages that suggests folks look for newer stuff.

In your case though - since you are seeing 19VAC from it, I should guess you have the coils hooked up right.  Hopefully the bearings spin very freely because it is a tiny machine with a tiny rotor.

Yes - putting a 5' diameter blade on it will not help, the alternator is simply not that powerful and it probably needs more speed in lower winds.  If bearing friction is not a problem, then a smaller rotor will spin faster in low winds and you should get more power.  The blade for that really does need to be fast.

Hooking it to a lower voltage battery will stall the blades too.....  with a larger 5' rotor, you migth do better to try charging a 10V battery or something, but at the end of the day I expect you'll get the most power from a smaller rotor, 3-4' in diameter.

Another factor there.. I wonder what sort of steel laminate you used?  I forget what I used, probably something horrible like band saw blades or something - but you will have losses in the laminates and they will make it stiffer to turn, best bet is find some silicon steel for that but it's probably not worth the trouble really.

That was a fun project and it did work - and perhaps the machine could've even held together for a while and produced a tiny bit of useful energy.  But it was mostly for fun and today I would do everything differently.

If you're very enthusiastic, I would learn a bit from this (like I did) and move on to a more practical design.

[farmer56]

I just did it as a quick project. As for the steel laminate, I used 5/8" strips of 24(?) gauge sheet metal that came in a roll. They were separated by invisible tape to prevent eddy currents.

[DanB]

that should work... again, I don't recall what I used (it's probably on the web page though).

I made a few machines with steel laminates of various types of steel (some good some bad) in wood like that.  it always seemed to put  some drag on the machine though and eventually the steel lams would always seem to pull the coils into the magnet rotors.

I much prefer the 'air core' now.. a bit more cost in magnets but none of the other troubles.

[Ungrounded Lightning Rod]

another thing that is a single phase alternator the coils need to reverse every other one around the stator...

Do you mean by reverse that you should hook the in wires to in's and out's to out's? Or are you supposed to flip the coils upside down?

They're equivalent.  (Think about which way the current goes around the coil in each case.)  Do either one of 'em - but not both (which would cancel out and leave you back where you started).