This was a lot of fun.
No stress for anything to really need to work.
But it does!
It started as killing time with stray parts, and grew into a simple little mill that has potential for a nice paper and project about wind power, from permanent magnet power generation to blade design.
I assume a lot of web surfers come here looking for something like this.
Well, here it is! Or here is one!
The 3 phase permanent magnet alternator is from a VCR.
Only the bottom plate was removed for the photo.
Most of these motors are held in with 3 screws from the top, and are very easy to remove.
The wires connecting the motors are unplugged.
The large disk on the front of the motor is probably held in place by magnets and a small plastic washer on the axle. Often the shaft can be pushed, removing the assembly as the washer slides down the shaft, but sometimes they need cut off.
Save the washer if it comes off easy.
There seems to be 2 common types of this motor.
The bad motor is subject to very strong eddy currents in the metal backing plate, and is not very usable because as the RPMs increase the drag increases to an extreme amount.
These motors are wired 3 phase star, meaning the 3 phases are connected together in one place, and each of the 3 phases have the other end going out of the motor.
An Ohm meter is needed to tell where the 3 motor output wires are located.
The 'good' motor in the photos has the common connections and output wires very easy to see and connect wires to.
The traces or conductors on the circuit boards were scraped away with a utility knife, just to be sure no power was being fed to the circuits.
The 'bad' motor had 3 holes drilled to get the wires out the rear.
Output wires are soldered to the ends of each phase.
This link by DanB has a nice drawing for 3 phase.
http://www.fieldlines.com/story/2003/9/11/84741/6758
Each phase has the same ohms reading.
This 'good' one is about 4 ohms.
From common to any output is 4 ohms.
From any output to any other output is 8 ohms.
From any common to any other common is about 0.4 ohms, but that is from the wires on the meter, and is almost the same as the ohm meter test lead to test lead.
Now seems like a good time to show the light wires.
Red LEDs light quite easy, and I recommend only red LEDs.
LEDs only pass current or light in 1 direction, but the alternator makes current back and forth (Alternating Current), so each section needs a pair of LEDs conected backwards from each other. The resistor is to limit current so the LEDs do not burn out, but they will have very little effect on the LEDs lighting up.
LEDs also have the advantage of not conducting any current until they reach a certain voltage, and that helps get the windmill turning before there is a load dragging the speed lower.
A regular light bulb will result in very poor, if any, operation. It must be RED LEDs.
I can not get a decent photo of the LEDs lighting.
It can be fancy or simple, but the wires can not touch each other where they shouldn't.
After the soldering is done the large disk with the magnet ring is replaced and a quick spin of the shaft should light the LEDs!
Wooden rulers make simple blades.
Part of the angles are ready to use!
I removed the metal strip, marked and cut off 3/16" along that side, from 3 and 1/2" to the end.
The blades are sanded for a trailing and leading edge.
A bench mounted sander will make things faster and easier.
The root, or center, is not changed.
The root angle is needed later for fastening to the hub.
A hub holds the blades together and on the front of the alternator.
It is not a motor any more!
This is a donut of wood 3/4" thick. Use smooth good wood. The chip board in the photo is not a great idea later. The center hole is as close to the pulley diameter as possible.
A set of hole saws helps make the hub easier.
The hub is marked with 3 lines 60 degress apart. Each line is marked twice and small holes drilled for screws that will hold the blades. The blades are marked and drilled with a bit that is a little larger than the screw threads.
Now the blades can be attached to the hub.
The more accurate everything is done the better.
The hub should now fit over the alternator, and the blades should look something like this.
Some rulers have a lower or higher angle than others.
This set of blades has 2 layers of a business card under one side of each blade to increase the angle as viewed from the end. About 8 degrees seems like a good angle.
After the blade angles are adjusted if they needed it, a bit of wood glue is a good idea.
Next is holding it all together.
This shows a main piece of wood with everything attached.
The center is drilled for a 5/16" bolt about 3-1/2" long. The bolt is placed in the hole, then a washer (so it turns smooth), then a tight nut.
Next, another nut is screwed half way up the bolt, the end of the bolt, on the side, was smacked with a hammer to badly damage the last 3 or 4 threads at the very end, and the second nut was screwed toward the end until it is firmly held in place by the damaged threads.
Then the alternator was screwed to the base.
A suitable tail and tail boom were assembled from scrap paneling and moulding, and attached.
Where are the blades?
A good quality double sided foam tape holds the hub to the magnet rotor and shaft.
That is why wood is better than chip board... nothing seems to stick very well to chip board, and chip board is damaged by water sooner.
The blade assembly is slid back into the alternator.
Blade balancing.
One side will probably come to the top, again and again, after a few slow spins. The top is the lightest side and a little extra weight to that side will help the windmill to start turning much easier.
A rubber band around the hub, holding a couple washers or maybe a nut, should show how much weight is needed and where. The weights can then be screwed to the hub.
Don't rely on a rubber band to hold any weights, because it will not!
This 'tower' is a section of 1/2" metal conduit.
The photos show the 1/2" conduit inside a piece of 1" copper at the bottom because that is one of my test towers.
The windmill nuts and bolt is simply placed in the conduit.
A few notes...
This windmill can make about 8 or 9 volts AC per phase under a load of about 25ma when spun by a flick of the fingers. I have no idea the RPM at that time.
These LEDs were placed in a half clear plastic tube in the first photo. The whole thing lights up very nice on a dark windy night.
Only -RED- LEDs!
Red colored plastic red LEDs are hard to see light up in day light.
"Water clear" red LEDs show up when lit the easiest, by far, because as soon as they light they turn red!
The blades could be a little shorter, maybe about 10" each, or even 9" for this particular alternator. Then the windmill would spin a little faster and the LEDs would light up sooner.
This particular windmill needs about 14 mile per hour wind, steady, not gusting, to light the LEDs with the 12" each blades.
Different alternators will act different.
The blades do not spin very fast at all in front of a fan. The air is too turblent. They work far better outside.
These blades could surely be improved upon, but these are easy to make, work well, and have a decent airfoil for a school paper.
It is very hard (I can not do it at all) to light the LEDs by hand spinning the shaft after the blades are attached. The LEDs light very easy without any blades.
A school project might want to have a alternator for the windmill, and one to light the LEDs by hand. Just so everyone can see it light up!
Accurate blade placement and making all the blades the same is important, it seems quite important for a decent balance. Good balance is important for the windmill to start turning in a low breeze.
Danger! These blades get turning very fast. A blade that flies from the hub, or hits a person will hurt, and could cause injury.
Be safe!
I will try to follow here for any questions.
Any simple to do improvements are appreciated.
Or any thoughts in general.
Please, do post any results if you try it!
G-
P.S. PhotoshopCS and msPaint. That's got to be a first! :)
