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/dev/thekevdog - My Homemade Wind Generator

http://www.thekevdog.com/projects/wind_generator/

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06.03.2009 19:45

/dev/thekevdog - My Homemade Wind Generator

http://www.thekevdog.com/projects/wind_generator/

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06.03.2009 19:45

/dev/thekevdog - My Homemade Wind Generator

http://www.thekevdog.com/projects/wind_generator/

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06.03.2009 19:45

How I Built a Wind Generator in My Backyard for $150

Lately I've been spending a great deal of time working on ways to
generate my own electricity. It isn't a necessity for me yet, but someday
being electrically self-sufficient could really come in handy. My interest
started a while back when I stumbled upon a how-to article on building
wind generators from treadmill motors and PVC pipe. It sounded easy
enough, so I decided to try and design my own. This particular design can
be built for $100-$150 if you are thrifty and can regularly generate
50-250 watts (considerably cheaper than a solar panel of similar power
output). Here's how I built it for those of you who are interested...

Videos

Before we get into the details of how to build one of these, here are some videos of it in action. Each one demonstrates the
behavior of the generator in a different blade configuration.

Long, thin-bladed design (best overall)

/dev/thekevdog - My Homemade Wind Generator

http://www.thekevdog.com/projects/wind_generator/

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06.03.2009 19:45

Six-bladed design (low startup speed and lots of torque, but slowest)

Wide-bladed design (good startup speed, but also very slow)

How does my wind generator work?

/dev/thekevdog - My Homemade Wind Generator

http://www.thekevdog.com/projects/wind_generator/

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06.03.2009 19:45

Every wind generator, whether they produce enough energy to power a city or to power a small radio, works on these same
basic principles...

1. The wind blows

2. The generator's vane (tail) causes it to turn into the wind

3. Blades attached to an alternator/generator experience the force of lift and begin to spin

4. The spinning creates electricity for us to use directly or to charge batteries

Sounds pretty simple eh? Well, then how the heck do I build one? Read on...

Tools Required

Surprisingly, building a simple wind generator only requires very basic hand tools, and if you are desperate you won't
necessarily need all of them. I used...

Jigsaw (or a hacksaw and a lot of determination)

Drill

(2) Drill Bits (1/2", 7/32")

Tape Measure

Crescent Wrench

Pipe Wrench

Protractor (to measure angles for the hub)

Sandpaper (various grits)

Parts Required

I wanted to be as minimal as possible with my design (I'm a poor college student), so I took the already simple designs from
around the web and made them even simpler. All of the parts are available at any local home improvement or hardware
store, and the entire setup can be constructed in as little as a weekend. Many of the parts you may already have lying
around, and lots of substitutions can be made (instead of 1" steel pipe for the tower, you could use an antenna pole for
instance). Here are the parts I used to build my generator...

10" x 14" Steel Sheet

10" x 1/4" Steel Nipple

1-1/4" Floor Flange

36" x 1" Square Tubing

1/2" Bore Circular Sawblade (for hub)

5/8" x 1/2" Arbor (to attach sawblade to motor shaft)

(2) Metal Straps

8" x 4" PVC Pipe

30" x 8" PVC Pipe (6" pipe works well too)

A DC Permanent Magnet Motor (preferably Ametek 30V or 260V 5A treadmill motor)

(8) 1/4" Bolts (with washers and nuts)

(2) 1/4" Sheet Metal Screws

/dev/thekevdog - My Homemade Wind Generator

http://www.thekevdog.com/projects/wind_generator/

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06.03.2009 19:45

10-40 Amp Diode (the bigger the better)

All of the above parts (with the exception of the motor), can be picked up in a single stop to any large hardware or home
improvement store. For the motor, the most popular types are old tape drive motors manufactured by a company called
Ametek. The key is to finding a motor that puts out the highest voltage per RPM. For instance, the Ametek is rated for 30V
at 325 RPM, making it excellent as an electricity generator. However, pretty much any permanent magnet motor with a
good volt/RPM ratio will do. Keep in mind that if you want to generate useful electricity, you will need to produce at least
12V to charge deep cycle batteries or run an inverter. My setup can easily achieve 300-400 RPM in a pretty average wind
(for Oklahoma). These instructions assume an Ametek motor with a 5/8" shaft, but can easily be adapted to other motors
(search ebay for "wind generator" and you will get a listing of lots of good motors).

Blade Construction

Arguably, the most important part of a wind generator are its blades. A lot of people like to carve their own blades out of
wood or composite materials. However, for the rest of us, it's quite easy to make a good set of generator blades from
common PVC pipe (and the efficiency isn't too bad either). A 2-3 foot section of either 6" or 8" PVC pipe will do the trick.
Before we go any further, here are a few blade theory quickies...

The longer your blades are the more "swept area" you have to gather energy from and easier your blades will spin in
low winds, but the slower your rotation speed will be

The tips of the blades always spin faster than the base, therefore one needs to take into account the "tip speed ratio"
(TSR) when designing blades (there is a reason why old farm windmills will spin all year long at 40RPM)

The power that can be extracted from the wind increases by the cube of wind speed (something like P=k*v^3
k=constant of wind generator, v=wind velocity)

According to the Betz Limit, only about 59.3% of power can be extracted from the wind (so in reality P=.593*k*v^3,
assuming k accounts for mechanical inefficiencies in the generator motor)

The higher you get the generator off of the ground, the more wind it will be exposed to (the general recommendation
seems to be 25-50ft., but I've had decent results at just 12ft.)

Cutting the blades for this machine is very simple. You will need to cut your PVC pipe into 3 sections, two 150 degree
sections and one 60 degree section (I've attempted to illustrate this VERY APPROXIMATELY in my favorite CAD
program--and by CAD program I really mean MS Paint). The red lines are cut marks. You will want to use a good tape
measure and possibly some construction paper or newspaper to mark everything before you cut. The 150 degree angles will
result in wide blades that start up in lower wind speeds, however this will lower the shaft turning speeds. In practice, you
will find that the optimum angle could be anywhere from 75-150 degrees. The best idea is start out with a wide set of blades
that you can always thin out later if you need to. Remember, measure twice and cut once!

After the blades are cut, I like to go ahead and smooth out all of the edges. If you want to follow aerodynamic theory, you
can round the angled (leading) edge and flatten the straight (trailing) edge, but in practice I haven't seen this make much
difference with PVC blades. So, you should end up with something roughly like these...

/dev/thekevdog - My Homemade Wind Generator

http://www.thekevdog.com/projects/wind_generator/

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06.03.2009 19:45

Hub & Blade Assembly

The next obstacle is building a hub to attach the blades to. There are many types of ways that this can be done. I have used
circular sawblades and scrap steel disks. I recommend the sawblade approach, as they are readily available and easy to drill
through. You can pick up an arbor with a 5/8" or 1/2" shaft at any homestore that will attach directly to the sawblade. Using
the 1/4" drill bit, you will want to drill 3 sets of 2 holes 1" apart which each set 120 degrees from the next (this is where the
protractor comes in handy, unless of course you are a Euclidean purist in which case you probably don't need a protractor).
Here is a picture to make it more clear...

It's a pretty simple idea, but circular sawblades have worked out very
well for me as hubs. Be sure and get some sort of rubber covering for the
tooth edges and/or file down the edges as best you can, because the last
thing you want is a hub of death flying at you if your generator decides
to rip apart!

After our holes are cut out and we are confident of our safety procedures, we attach the blades to the hub (note that the hub
pictured was cut from scrap steel, more pictures to come later)...

/dev/thekevdog - My Homemade Wind Generator

http://www.thekevdog.com/projects/wind_generator/

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06.03.2009 19:45

Tail & Pivot Assembly

Now we need to build a spinning platform for our generator motor to rest on. To achieve this, we will use some square
tubing, a pipe nipple, flange, and small sheet of steel. Here is my "CAD" draft of what I wanted my tail & pivot assembly to
look like, and a real picture of some of the parts I used...

/dev/thekevdog - My Homemade Wind Generator

http://www.thekevdog.com/projects/wind_generator/

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06.03.2009 19:45

First, I recommend cutting the sheet steel with a jigsaw into a nice design for the the tail (Note: this step is quite
unneccessary and ONLY for aesthethic reasons).

We then want to make a cut down the center of the square tubing. The length of the cut isn't that important, but I
recommend about a 9" cut (this will help make balancing easier later on). We may then slide the tail metal into the hole and
use the 1/4" drill bit to drill and attach the tail to the square tubing.

/dev/thekevdog - My Homemade Wind Generator

http://www.thekevdog.com/projects/wind_generator/

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06.03.2009 19:45

We will then want to cut out a weather covering for our motor. A piece of 4" PVC slips perfectly over the Ametek 30V
motor that I use. I cut it out like so (note the side hole for the motor wires).

Then we go ahead and paint it all up to seal everything from the elements. I wouldn't recommend painting on your front
porch like I did though...

/dev/thekevdog - My Homemade Wind Generator

http://www.thekevdog.com/projects/wind_generator/

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06.03.2009 19:45

After everything is painted, we can now put it all together. Take the floor flange and put it under the square tubing about
6"-7" from the head. Mark the holes and drill them out with the 7/32" drill bit (or any bit close to but smaller than 1/4").
Attach with the 1/4" sheet metal screws. Use the metal straps to secure the motor and cover assembly, screw on the pipe
nipple and you should have something like this...

Watch the latest videos on YouTube.com

Tower Assembly

Every wind generator needs a tower. I built mine from some pipe fittings from my local hardware store. If you already have
an antenna pole or electrical conduit lying around, then you can skip this section. Here is my recommended parts list for a
small extensible tower...

(2) 5' Sections 1" Pipe

/dev/thekevdog - My Homemade Wind Generator

http://www.thekevdog.com/projects/wind_generator/

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06.03.2009 19:45

(1) 1" Pipe Coupling

(3) 1" Pipe Elbows

(4) 18" Pipe Sections

(2) 12" Pipe Sections

The tower base is pretty self-explanatory. Just hook up the elbows and pipe sections to create a base similar to this...

From there we can attach the 2 5' sections of pipe together to form a nice strong mini-tower for our generator to sit atop...

/dev/thekevdog - My Homemade Wind Generator

http://www.thekevdog.com/projects/wind_generator/

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06.03.2009 19:45

Finished Product

Now we are ready to attach the blades to the motor shaft with the arbor. You will also want to go ahead and attach some
wire to the motor and run it to a device to power or a bank of batteries etc...

Here is a picture of the experimental design using six blades. It would spin in practically no wind, but would never get past

/dev/thekevdog - My Homemade Wind Generator

http://www.thekevdog.com/projects/wind_generator/

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06.03.2009 19:45

100RPM. At least it looked interesting!

Here is the battery bank I'm feeding into in parallel with solar panels. I am just using two 12V marine deep cycle batteries
that can be found at any place that sells car batteries. I keep them in a standard plastic tub with a hole cut in the sides for
12V fans I cannibalized from a couple of old Mac G4s (not pictured). Be sure and put a diode between the battery and the
generator so that current doesn't flow from the battery to the motor.

It turns out, cutting the blades a little thinner works better for my area. So I used the large white blades from the previous
picture and thinned them out a bit. This resulted in the fastest shaft speeds as seen in first video at the top of this page.

/dev/thekevdog - My Homemade Wind Generator

http://www.thekevdog.com/projects/wind_generator/

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06.03.2009 19:45

Not too bad for a 22 year old kid from Oklahoma eh? Please feel free to use my

contact form

if you have any questions, and

of course I will gladly welcome your feedback positive or negative.

Contact Kevin Harris

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/dev/thekevdog - My Homemade Wind Generator

http://www.thekevdog.com/projects/wind_generator/

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