Lenz2 Wind Turbine

141,702

364

65

Posted

Introduction: Lenz2 Wind Turbine

This instructable will show you how to build a Lenz2 wind turbine from materials you have around the house.

The design was developed and tested by Ed Lenz of Windstuffnow.com:
http://www.windstuffnow.com/main/lenz2_turbine.htm

The Lenz2 VAWT (Vertical Axix Wind Turbine) is 4 foot tall and 3 feet in diameter. It is a basically a Savonius style turbine but with the refinement that the three wings are shaped to provide lift as well because or their teardrop configuration. In the above link Lenz describes how he placed an ananometer inside the stational turbine and showed that the windspeed picked up passing past the solid portion of the wings. This turbine is more efficient than a pure Savonius in that it provided both drag and lift.

In my design I scaled down the diameter to approximately 18 inches and the height to 21 inches. (In hindsight, I should have made the height 18 inches so that there would be more of the center axis free on both ends for flexibility in mounting.)

I was able to use materials I had on hand to build the turbine. When I tested it in a 15 mph wind, it worked so well that I was afraid to stop it for fear of getting injured. The only downside of what I produced is that it seemed to produce very little electricity. This is not due to the design of the turbine but to the nature of the DC motor that I had it attached to. The emphasis in this tutorial will be on how to construct the turbine itself. Full credit for the design and some of the instructions goes to Ed Lenz.

[Note: Since this instructable was published, I learned more about how the wings should be shaped. The construction details for the lenz2 provided in this instructable still hold but the dimensions of the wing in Step 2 should be substituted for those given in the newly inserted Step 3.]

Step 1: Materials Needed

The materials you will need are listed below. Substitute alternatives freely if you think they will work.

Materials
Plywood (quarter or half inch)
Steel strapping with holes in it (other alternatives are possible)
Nuts and bolts
24 inch allthread rod (half inch diameter)
.5 inch nuts that fit on the althread rod (about 6 of them)
Roof flashing, thin sheet metal, or even some sort of flexible plastic
9 pieces of lumber, .5" x 1" x 18"
Hardware for mounting your turbine (you will have to design this)

Tools
Drill and drill bits
Tin snips
Jigsaw
Wrenches

Step 2: Cut Out the Wing End Pieces

[Note: The design for the wing in this step will not give the best lift. Please look at step 3 for a better design. It will show that the sides of the wing are not symetrical. Step 3 will also give a procedure for sizing the wing based on the diameter of the lenz2. (added 1 June 2008).''']

The teardrop endpieces will provide the aerodynamic shape of the wings. You will be building three wing so you will need 6 end pieces. The size I used was half the size the the end pieces described by Ed Lenz. They basically look like ice cream cones.

I recommend that you cut out a cardboard template and use it to draw six images of it on half-inch plywood. Here's how to draw it:
1. Cut a rectangle of cardboard 3.5" x 7.5"
2. Draw a center line along the long axis
3. Make a mark on this line 1.75" from one of the ends (let's call it this the top end)
4. Draw a horizontal line through that mark to the side edges so that it intersects the vertical line at 90 degrees.
5. Using a compass, draw a 1.75" half circle on the top side of that mark. It should intersect the two side edges and the top edge.
6. From where the center line intersects the bottom edge draw lines to the points where the half circle intersects the side edges.
7. Cut out the template.

Use the cardboard template to draw six images on the half inch plywood. You can nest them in such a way that you don't waste the plywood.

Use a jigsaw to cut out the end pieces.

Step 3: Revision: a Change Inthe Shape of the Wing

The original shape of the wing presented in this instructable is not quite according to the plan posted for the Lenz2. After consulting with Ed Lenz, I became aware of the mistake that I have made in interpreting his plans. The new design is illustrated in this step.

Notice that the angle labeled "Angle A" is 90 degrees. Side A is at a right angle to the diameter line of the rounded end of the wing. In the original design that I presented in this instructable, the two lines forming the pointed end of the were of equal length and their angles to diameter line were identical. That cone was symetrical whereas in the change being shown here, the cone is not symetrical. Making Angle A to be 90 degrees will give the wing more lift

I have resized the design so that I can drive a minigen generator that had been sold at windstuffnow.com (but is no longer available). The basic steps in fabricating the lenz2 are still valid.

Basic Calculation:
I now understand better how to determine the size and proportions of the wing. You first determine what the diameter of lenz2 will be. The easiest way to do this is to decide what the distance will be from the center axis of the lenz2 to the outside edge of a wing. This will be the radius of the lenz2. You double it to get the diameter.

In my new design, I made the assumption that the diameter of lenz2 will be 16 inches (that is, the distance from the center axis to the outside edge of a wing will be 8 inches).

To determine the diameter of the wing, multiply the diameter of the lenz2 times .1875. In my example, 16 inches * .1875 = 3.0 inches.

To determine the length of the wing, multiply the diameter of the lenz2 times .4. In this case, 16 inches * .4 = 6.4 inches. The length of Side A is 6.4 minus 1.5 or 4.9 inches.

I will be creating a new instructable that will include this design in a lenz2 that drives a minigen generator

Step 4: Cut Out the Ribs

You will need to have three ribs to connect the two end pieces of each wing. The length of these ribs will be determined by how tall you want the wings to be. I chose 21" because that's what I thought I could mount on the vertical axis allthread bar.

The ribs should be .5" deep and 1" wide and whatever length you choose (21" in my design).

You will be cutting out .5" x 1" notches in the end pieces where you will dock the ribs. I suggest that you trace the end of the end of one of the ribs on a piece of card paper that you can use as a template for drawing on the end pieces. You could measure the rectangle but by tracing it, you can be sure that the notches will be just large enough.

Step 5: Prepare the End Pieces

Use the .5" x 1" carboard template for the rib notches to draw three notches on each end piece. Two notches will be on one side and one on the other.

There will be a notch on each side of the end piece at its widest point. Since this will be on a curve, make sure that depth of each side of the template full fits into the end piece. This will make sure that the rib will be flush with the outside edge of the end piece.

On one side of the end piece near the pointed end draw a pattern that is about one inch from point. The rectangle will be parallel to the slanted side. The side with two notches will the back side of the wing (the side that faces the center of the turbine.)

Cut out the notches with a jigsaw.

Step 6: Plan the Wing Angle

The pointed end of each wing will be rotated 9 degrees back towards the center of the turbine at 9 degrees off being parallel to the center of the turbine. This measurement was empirically determined by Ed Lenz. I chose that angle and the turbine seemed to work fine. You will have the ability to adjust the angle after the wings are mounted if you feel that you want to prove it to yourself.

First drill a hole in the center of cone part of the end piece. This will be the point where the vertical and horizontal lines meet. The size of the hole will be the diameter of the bolt that you will use to attach it to the strut leading from the center axis.


From somewhere along staight portion of the back edge of the end piece (the side with the two rib notches) draw a line across the end piece that is at right angles to the side.

From where that line intersects the back edge of the end piece, draw a line 9 degrees to the right of that 90 degrees line (this will be on side that is closer to the hole). This line will the one that the bar connecting the wing to the center axis lines up with. If you don't have a protractor, see step 8 for a link where you can download a protractor image.

Do this with all six end pieces.

Step 7: Assemble the Wing Frame

To assemble each wing you will insert a rib into corresponding notches on top and bottom end pieces. Make sure that the rib does not protrude beyond the top and bottem pieces. They should should be flush.

With a rib in place, pre-drill a single hole through the rib and into the plywood. Screw the rib into place with a 1" wood screw. You could optionally glue these ribs into place but this isn't necessary unless you are building a turbine that you actually intend to use outside to produce electricity.

Attach the other two ribs to form the wing.

Step 8: Attach the Skin of the Wings

The round part of the wing and the back side (the side with the two ribs) is covered with some sort of skin. I chose to use aluminum flashing material that I had left over. You may have some other kind of material that might work.

My roll of flashing was 6 inches wide. I discovered that if I cut two pieces 6" x 21", I could cover the leading edge and the back of each wing. I was able to attach one piece of flashing from one rib to the other around the leading edge. I anchored each piece with a few metal screws. Some of these went into the ribs and others into the edge of the plywood end piece. Then I attached the second piece of flashing to the back part of the wing, They were screwed into the back ribs. This piece of flashing can overlap a little with the one going around the leading edge.

Do this for all three wings.
Now you are ready to attach the wings to the center axis.

Step 9: Prepare the Struts and Center Disks

The wings will be attached to the center axis (the allthread bar) using two circles of plywood and struts that connect these to the tops and bottoms of the wings.

Cut two 8 inch circles of half inch plywood. Using a full-circle protractor (I downloaded one from
http://upload.wikimedia.org/wikipedia/en/thumb/0/0f/Protractor1.svg/531px-Protractor1.svg.png
), I marked lines on each circle that were 120 degrees apart. These will be the lines that the struts follow out to the wings.

drill a hole in the center of each of the circles. This hole will be the same diameter as the allthread bar.

For struts that connect the circles to the wings, you have a variety of choices. The easiest might be to simply to make these out of wood. I chose to use wood for the bottom struts (because i wasn't sure that the metal strap that I bought would support the weight. For the top I bought a 4 foot piece of zinc plated metal that had holes punched in it along the center line of the strip of metal.

I cut the struts to 11 inches in length. Then I placed the end of each strut 1 inch from the center of the circle along one of the 120 degree lines. I drilled two holes in the strut and one through the circle of plywood. I bolted these firmly in place.

About one inch from the other end of the strut I drilled a hole the same diameter of the hole in the end piece.

Step 10: Mount the Wings to the Center Axis

Thread a .5 inch nut onto the bottom of the axis (the allthread bar) so that it is about 2.5 inches from the end. Slip one of the plywood disks up from the bottom of axis to where it meets the nut. Then thread another nut up the bar to where it meets the disk. Crank the two nuts toward each other so that the disk sits firmly on the axis.

Attach the second disk to the other end of the axis. You may have to adjust the position of the disks so that they accomodate the height of the wings and also leave room for attaching the axis to a generator or some other structure. Note that there is very little axis sticking above the top of the center disk. I had decided to make the wings 21 inches on a 24 inch axis bar. This was a mistake. In hindsight, I suggest that you make the wings shorter so that you have much more of the axis sticking out the bottom and the top for flexibility in mounting the whole turbine to a generator or other structure. I probably would go with 18 inches.

Now you can mount the wings. With the covered side of a wing facing towards the axis, bolt the struts to the end pieces. These can be fairly tight but loose enough to rotate. Now line up the top strut with the 9 degree line you drew and then tighten down the top and bottom nuts. This angle the wings towards the center axis the right amount.

Do this with the other two wings.

The turbine is ready to be mounted to a generator or some other structure.

Step 11: Mount the Turbine to the Generator

Somehow you will have to mount the turbine to a generator or possibly some sort of support framework that will let it spin freely. In this project I mounted it to a 24 volt DC motor that I had saved from a battery-operated lawnmower. The motor was used to spin the blade of the lawn mower.

The motor has plus and minus spade connectors at one end and a shaft protruding from the other end. Unfortunately the shaft was half inch in diameter with fine thread. This makes it very difficult to mate with something like an allthread bar with is half inch coarse thread.

The way I solved the problem is to bolt an L-shaped bracket to the shaft of the motor. Then I used a piece of metal that I had saved from an old tiller. It is U-shaped and has holes on the side and a threaded hole on the top. The threading is half inch coarse thread, just perfect for mounting the allthread bar. Finally, bolted the U-shaped connector to the L-bracket.

I cut a hole in a piece of plywood large enough to insert the motor. After inserting the motor to the plywood, I bolted it down. To try out the turbine, I placed the whole affair on top of a heavy wooden box.

Step 12: Demonstrating the Turbine

You can see in the videos that the turbine spins very well in the fairly strong wind that was blowing. I would estimate that it was about 15 mph. It worked so well that I had to temporarily tie the turbine to the box to keep it from falling over. You can clearly see that it is spinning very fast but also bouncing around. The reason for this is the mount of the turbine to the motor is not perfect. It is slightly off-kilter and this can never be improved with this setup.

Does it generate electricity? Sad to say, not much. The problem is the motor. I have no idea about the design of the motor. You will notice a wire leading from the turbine to out of the photo. This is an extension cord with the male end cut off and attached to the motor. With this setup I can insert the probes from a multimeter into the female end. It turns out that I am barely generating 1 volt with the turbine running very fast.

This is the point where another project needs to start. There are numerous discussions on the internet on how to build your own generator. It is also possible to use the right kind of automobile generator or something from a washing machine.

If you don't have a generator in mind, I would suggest you test your handiwork by mounting the turbine on some sort of structure where the wind will catch it. This might be a wooden frame or something made of PVC pipe. This way you can see if the design works and if you have to make adjustments to the angle of the wings. You can also measure what windspeed is need to start the turbine turning.

If you are interested in what the average wind is in your area, you can visit an application that I have on my website that will let you pick a NOAA weather station near you and see a plot of wind, temperature and pressure for the past 24 hours. My application plots these data and gives them in a table. What you want is the average windspeed over the past 24 hours. If you visit your favorite location periodically, you will be able to take note of how the average changes. The link is: http://www.datasink.com/cgi-bin/stationCodes.cgi

Share

    Recommendations

    • Science of Cooking

      Science of Cooking
    • Pocket-Sized Contest

      Pocket-Sized Contest
    • Spotless Contest

      Spotless Contest
    user

    We have a be nice policy.
    Please be positive and constructive.

    Tips

    1 Questions

    what would the lenzs 2 blade be for a 5kw . I live in south Dakota winds r rated a 6 I believe

    I really can't give advice on something like this. As stated in the instructable, there was no generator connected to the blades. I was just experimenting with the vertical blades.

    62 Comments

    For a school project we're building a lenz2 type windturbine. in addition to the practical realization we also need some theoratical information and calculations. but we can't really find any information on the internet. does someone maybe have some useful information?

    Fantastic! I have had the frame or skeleton of the blades and PMA for this project but I have not found out how or where to find sheet aluminum. Buy it online I guess?

    You might try flashing that is used for roofing. Not sure if that is aluminum or galvanized steel.

    Sweet Thank you very much. The flashing sounds promising. I am sure I will find a way to deal with it even if it is steel. I might need a little more weight on the blades anyway. Thank you again

    What if you built the wings with balsa wood and mylar sheets, of carved out foam? cound that reduce the weight and make them spin easier.

    To make it durable and weather resistant you could make it from foam or balsa and just fiberglass it. that'd make it super light and still very durable in high winds.
    I have been playing with the idea of skinning the ribs with fabric or hardware cloth and fiberglassing it to see what i can get...

    Sure, that would work. However, I wonder about the durability in rain and strong wind. It would make a good demo model, however.

    what kind of motor did you use as tyour generator?

    Oops! That last part of the math expressions should have read:

    1/2.618034 = .3819661, 1 - 0.3819661 = 0.618034

    I wonder whether this design was arrived at empirically first and then tweaked to conform to the interesting mathematics of it, or the reverse. I notice that the proportion of outside degrees of arc corresponding to vanes and to the open spaces between them is right on the Golden Mean (1.618034 or its reciprocal, 0.618034). The angle of the vanes with respect to a tangent to the circumference has a tangent very close to 0.618034 (3/4.9 = 0.612, or a 0.9% difference).

    I would think the rationale behind this is that the Golden Mean has very interesting self-referential and scale invariant properties. Since air is essentially scale invariant macroscopically at low wind speeds, I would expect the self-referential nature of the Golden Mean to produce a high probability of self-reinforcing aerodynamic behavior. (1/1.618034 = 0.618034, 1.618034^2 = 2.618034, 1/2.618034 = 0.381966 = 1 - 1.618034, etc.)