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A 12VOLT 10 AMP WINDMILL

AN ATTEMPT AT DIY POWER GENERATION. A CRUDE SYSTEM BUT IT WORKED. BUILT WITH IBM TAPE DRIVE PERMANENT MAGNET DC MOTORS.
(all this, just to power my low voltage outdoor garden lights)

 

 

 

 

 

SCHEMATIC

A crude concept, but it worked.

Introduction

This project started after I moved from the small town of La Verne which is located in the greater Los Angeles area to the town of Hesperia which is located approximately 100 miles driving distance east – northeast from Los Angeles and at an elevation of about 4000 ft. above sea level. Why the windmill you may ask? I would almost bet that the wind used to blow 300 days out of the year and sometimes at gale force. One storm was measured as having a wind gust of 91 miles per hour!   

 

The Tower

I built the windmill tower out of galvanized water pipe that I had on hand and welded it together  with a little help from my father.  The pipe sizes were 10 foot lengths of 1 inch diameter galvanised water pipe for the bottom three legs. Then 6 foot lengths of ¾ inch galvanised water sleeved down into the 1 inch pipe and welded. This makes the tower about 16 foot high. All the cross members were ¾ inch electrical metallic tubing or E.M. T. conduit as we used to call it in the electrical trade.

 

Motors Now Generators

The generators are 2) 24 VDC permanent magnet DC motors that came out of old IBM mainframe computer tape drives. You know, those old giant reel to reel type tape drives. One nice thing about the DC permanent magnet motor is it already has it's field excited (magnets) and all you have to do is get it up in the wind and get it to spin and voltage will be produced in it’s armature. The only problem is you can't regulate your armature output by adjusting your field voltage because it's fixed by the strength of the magnets. Also, the output of the armature will increases or decreases with the speed of the propeller i.e. wind speed.  This was in line with my frugal nature and I took the cheap and easy way out rather then using a generator or alternator with an electro magnetic field that required some sort of exciter/voltage regulator circuit.

If I recall, the PM motors cost me $10 U.S. each when I purchased that at one of the many ham radio swap meets in the Los Angeles area.

 

I first tried using one motor but could only get about 14 volts DC out in a very strong wind which meant it was only around 8 or so volts in a nice breeze. So most of the time the two 12 volt car batteries in the prototype windmill were not getting charged.  I decided to add the second motor in series electrically and mechanically. Luckily the motors had about 3 inches of shaft out the front  of it and 1 inch of shaft out the back of the motor. Mechanically, the motors were mounted one behind the other and coupled with a piece of ½ inch standard garden hose and two small hose clamps. (a poor mans coupling) Electrically, the motors were wired in series up at the top of the tower and only 2 wires came coming down to the battery box. I had nothing to govern the maximum speed of the blade when it was in a gale of a wind. So I slightly bent the tail so it would start to push it's self out of the direction of the wind when in a gail and hopefully hold the propeller and generators together. I must say it survived a 91 mile an hour gust in a fearsome windstorm we once had, unlike my 45 foot ham radio tower and antennas! (Oh I cried!) The blades were painted black and the tips of the blades were painted yellow so you could see a slight out line of the yellow if I ever had to work around them. It was unbelievable how fast the blade would turn, even in a nice little breeze. It was just approximately a 4 ½ foot black blur with a yellow outline. Nothing like hearing those blades cutting through the wind. I always waited for the blade tips to break the sound barrier, but it never happened. (laughing)

The Propeller Blades
The blades were cut out of 3 inch diameter electrical metallic conduit or E.M.T.  I think they were about 2 foot in length each. The hub that the blades were welded onto was also 3 inch electrical conduit, about 3 inches long. The round flat ends that were welded onto the hub were off of two 12 inch stereo speakers. The ½ inch I.D. shaft coming out of the hub that went onto the 1/2 O.D shaft of the front generator was galvanized water pipe 1/2  inch in I.D. The I.D. was actually just under 1/2 inch so I had to drill out the ½ inch water pipe with a 1/2 drill bit. I also drilled and taped 2 holes in the propeller shaft for two set screws to hold it onto the shaft. I just used to tighten the set screws up into the key way on the 1/2 inch generator shaft. It didn’t seem to need too much pressure to hold it on to the motor shaft because the propeller is always pointing into the wind. Well in theory at least. The blade did come off once at high speed. It rolled across the back yard in stuck into the neighbors wood fence. The propeller was a total write off. A new propeller had to be built from scratch. This problem can happen if you loose the tail which then turns the windmill around and points the propeller down wind. The other scenario is if you have strong winds that just don't gradually slow down but just stop all of a sudden. In this case the blade is still turning but there is no wind turning the blade and it just drives itself forward right off the front of the windmill generator shaft. Just a note: The second propeller used a proper key and keyway with an interference fit to keep the propeller on the generator shaft.

 

 

Balancing the Propeller

Make sure the propeller blade is balanced, balanced, balanced!!! A nice little secret my father showed me was to put a piece of shafting all the way through the center of the propeller blade hub. In this case, ½ inch diameter and approximately a foot in length.

 

I then put the propeller blade and this temporary shaft onto 2) 10 foot lengths of electrical conduit (use what ever you have on hand)  that are in parallel and about 6 inches apart. I layed one end of both conduits on the workbench and the other ends onto a rubbish bin. The 2 lengths of ¾ inch conduit need to be level with each other but pointing down hill by about 2-3 inches with in the 10 foot distance. I set the propeller on to and in between the  2) ¾ inch conduits with the 1/2 inch hub shafting across the top of both ¾ conduits. I now gave the propeller a slight push and it should of slowly rolled all the way down the 10 foot lengths of conduit, that’s if it's balanced! In reality it rolled only a few revolutions before it came to a stop with the heavy blade pointing down. Sometimes the heavy side is split between 2 blades. I used little broken bits off a 12 inch stereo speaker magnet as test weights and placed them out on the backside of the propeller blade tips and then re-roll it again. I did this until it rolls all the way down. Then I used some very small pieces of the 3 inch conduit, (it has he same 3 inch natural curve as the blades) 1/2 by 1/2 inch squares for example.  The metal weights were welded onto the backside of the blade tips out at the far ends right out were the test magnets (weights) were. These 1/2  inch small square pieces are the course adjustment. The propeller was re-roll and tested again. For the fine adjustment, the actual steel "weld" is used. I even had to use my grinder and take a tiny bit of "weld" off to get it perfect.

 

You'll find out how balanced it is when it's spinning in a 50 mph wind!!!  It either purrs like a kitten or self destructs!    

Always Pointing Into The Wind

After much thought I could only think of 2 practical ways to transfer power from the generators at the top to the batteries at the bottom of the tower.  The use of slip rings and brushes is probably the proper way to construct it but again due to my frugal nature I chose to do the following.

 

The mechanism which let's the windmill rotate 360 degrees and always points it into the wind is the left front spindle/axel and bearings off of an old VW. The spindle already has a 1/8  square hole all the way through it for the mechanical speedometer cable. All I did was drill it out to 3/8 inch. Well big enough to get two #12 A.W.G (American Wire Gauge)  insulated wires,  one red and one black wire down through the spindle and down to the battery box.

 

Now there’s just on slight problem…. I had to go out and climb the tower every 2-3 months and spin the generator and propeller around about 6-8 times to untwist the two wires coming down to the battery box from the generators. Something you have to worry about when you don't use slip rings. Also, you must pick a day when there is no wind, you really don’t want to climb a windmill tower when the steel blade is spinning so fast you can’t even see it!

Electronic Circuits

The electronics circuits are crude but pretty much straightforward. It all worked quite reliable for 3 years. 

 

As you can see from the attached picture file of the circuits the voltage regulator is your standard pass transistor regulator. The Zener diode and relay was just something that I came up with because I couldn’t think of a circuit to turn on when the voltage was about 14 volts and shut off when it dropped down to about 13 –14  volts. The Zener/relay combination energized at 14 volts and dropped out at 12 volts. This was the best I could figure out at the time.

 

The battery charger is a small trickle charger circuit. If my memory is correct, it used to charge at

1-2  amps on days when there was no wind. 

 

The day night sensor circuit and RC timing circuit are of my own design. It’s very crude but I eventually got it to work right. (after a few trips to the local electronics shop to replace the parts that had produced smoke!)  If my memory is correct, the time the lights would stay on was from 2 hour to 6 hours. 

 

The whole system used to work something like this. During the day time the batteries would either be charged by the battery charger or the windmill. If I remember right, it used to blow about 300 days out of the year where we lived so the batteries charged all day by wind!!! The battery charger only worked during the day, not at night.  During the night, all the outside garden low voltage 12 volt lighting which I had installed out and around the front of the house and garden would energize from 2 to 6 hours depending what I set it for. If there was wind then the generators would assist with the out door lighting. If not, then the batteries were on their own to power the lights.

As a side note: I never did use the 120v/12v power packs that came with the lights. I even think I chucked them in the rubbish bin upon opening the boxes. “ No need for power packs, wind power is going to power these lights.”!!!

 

I eventually gave the whole thing to 2 old gentlemen, ham radio operators of course, they were from Barstow, California. Yep, gave it away when I decided I was going to immigrate to Australia. They told me they were going to re-install it on a hill at their 2 meter radio repeater site? I don't know if they ever did. (Hey, if you two old blokes ever read this… tell me how the old windmill is operating!)

 

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