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    Methods of Teaching Physics

    M. Vanaja

    D. Bhaskara Rao

    Chapter 14 : Laboratories

    301

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    http://books.google.com.ph/books?id=JUfpB6slS8EC&pg=PA309&lpg=PA309&dq=common+laboratory+

    apparatus+physics+that+can+be+improvised&source=bl&ots=qrARH0-LXT&sig=tPTkXMi1-

    FmZ8aRfb1wXy-WBJ20&hl=en&ei=zY-

    ATNWgOMuPcY_OqaML&sa=X&oi=book_result&ct=result&resnum=4&ved=0CCMQ6AEwAzgK#v=onepa

    ge&q&f=false

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    http://books.google.com.ph/books?id=0jeCQ140w1gC&pg=PA155&lpg=PA155&dq=common+laborator

    y+apparatus+physics+that+can+be+improvised&source=bl&ots=yrFRsMneJv&sig=ZeDwupY2utIoxuLWyJ

    xlPgmqDs0&hl=en&ei=M5WATODMH4zBcZzX6fgK&sa=X&oi=book_result&ct=result&resnum=5&ved=0

    CCMQ6AEwBDgU#v=onepage&q&f=false

    Beakman's Electric Motor

    I saw this on the TV show Beakman's World and I was very impressed that you could

    actually build a working electric motor with so few parts. I built one and brought it to

    work where it was a big hit with all the engineers around here. This writeup was for a

    friend of mine who wanted instructions that his son could follow for a science fair

    project. So, if you missed the show, here's how to build one. If you are using a text

    only browser, you can click on the "Figure" links to download the drawing s (GIF

    files). BTW, my friend's son won second place in the school's science fair.

    A homemade DC motor is a great project that illustrates electromagnitism and electro-mechanical energyconversion.

    This is a link to a design that only needs a few simple parts; wire, battery, magnet and paper clips, and

    voila! a spinning motor!

    Materials Required:

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    y One 'D' Cell Alkaline Battery

    y One Wide Rubber Band

    y Two Large Paper Clips

    y One Rectangular Ceramic Magnet

    yHeavy Gauge Magnet Wire (the kind with red enamel insulation, not plasticcoated)

    y One Toilet Paper Tube

    y Fine Sandpaper

    y Optional: Glue, Small Block of Wood for Base

    Instructions:

    1. Starting about 3 inches from the end of the wire, wrap it 7 times around the

    toilet paper tube. Remove the tube (you don't need it any more). Cut the wire,

    leaving a 3 inch tail opposite the original starting point. Wrap the two tailsaround the coil so that the coil is held together and the two tails extend

    perpendicular to the coil. See illustration below:

    Figure 1: M1.gif

    Note: Be sure to center the two tails on either side of the coil. Balance is

    important. You might need to put a drop of glue where the tail meets the coil

    to prevent slipping.

    2. On one tail, use fine sandpaper to completely remove the insulation from the

    wire. Leave about 1/4" of insulation on the end and where the wire meets to

    coil. On the other tail, lay the coil down flat and lightly sand off the insulation

    from the top half of the wire only. Again, leave 1/4" of full insulation on the

    end and where the wire meets the coil.

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    Figure 2: M2.gif

    3. Bend the two paper clips into the following shape (needle-nosed pliers may be

    useful here):

    Figure 3: M3.gif

    4. Use the rubber band to hold the loop ends (on the left in the above drawing)

    to the terminals of the "D" Cell battery:

    Figure 4: M4.gif

    5. Stick the ceramic magnet on the side of the battery as shown:

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    Figure 5: M5.gif

    6. Place the coil in the cradle formed by the right ends of the paper clips. You

    may have to give it a gentle push to get it started, but it should begin to spin

    rapidly. If it doesn't spin, check to make sure that all of the insulation has been

    remove d from the wire ends. If it spins erratically, make sure that the tails on

    the coil are centered on the sides of the coil. Note that the motor is "in phase"

    only when it is held horizontally (as shown in the drawing).

    7. For display, you will probably need to build a small cradle to hold the motor in

    the proper position. It might also help to bend the ends of the coil a bit so that

    as it slips right or left, the bends keep it in the proper position:

    Figure 6: M6.gif

    8. Here is a diagram of the finished motor:

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    Figure 7: motor.gif

    Further Experiments:

    Since this is an existing design, you might want to do some further experiments tomake it more of a Science Fair experiment instead of just a model. Here are some

    suggestions:

    1. Try to adjust the phase angle of the motor so that it will operate in a vertical

    position. This involves removing a different area of insulation from the

    partially bared tail of the coil.

    2. Try making different shaped coils and seeing how they work. Is the circle the

    best shape? Try squares, ovals, etc. Make a display showing each of the coilsyou tried with a short summary of the results underneath them.

    3. Try varying the number of turns of wire in the coil. I don't know where they

    came up with seven. Does even or odd number of turns matter? Does the

    number of turns determine the speed? Again, include the different coils in the

    display and describe the results.

    4. How long can you get the motor to run before it falls off the cradle?

    5. Turn the coil slowly by hand and feel the magnetic attraction at each position

    of the coil. Make drawings showing the different coil positions and describe

    how the attractions vary at each position.

    6. HARD ONES: Can you think of an interesting way of determining the speed of

    the motor (in RPM)? Can you make the motor do any work?

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    Final Notes:

    You can get the magnet wire and ceramic magnets at Radio Shack. I think the wirecomes in a pack of three spools of different gauges, you want to use the mediumgauge, not too heavy, but thick enough to hold its shape.

    Be sure to bring a fresh (extra) battery to school with the project.

    You should include the Beakman's World show in your bibliography.

    http://home.hiwaay.net/~palmer/motor.html

    ClocksHow do clocks keep time?

    What was the world like without clocks?

    How did people keep appointments?

    Getting Started

    Without looking at the clock or your watch, look out the window and guess what timeit is. How close were you to the "correct" time? What clues did you use to tell what

    time it was? Are there other things you could use? How do you know it's lunchtimewithout looking at a clock?

    How does a clock measure time? What would happen if a minute were 100 secondsand an hour were 100 minutes? How would that change the way you schedule yourday? How long would this class last? What about your school day?

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    Overview

    The alarm clock rings in the morning and, even in your drowsy fog, you look to see

    what time it is. As you get dressed, you check the clock again and again to make sureyou're not late for school.

    We look at clocks all the time because these devices help us regulate our lives, tellingus not only when to get up, but when to eat, sleep, play, and work. They are so much a

    part of our lives that we rarely think about what clocks really do.

    Whether they are highly accurate atomic clocks or slightly less accurate quartzwatches, electric alarm clocks or grandfather clocks with slowly swinging pendulums,all clocks have one thing in common - they consistently count precise units of time.

    Those units could be anything we want them to be, but for the world to function inharmony, we have a timekeeping standard based upon three units of time - seconds,minutes, and hours.

    To measure these units, all clocks must have two things: a regular, repetitiveresonator, or oscillator, to mark off equal units of time; and a way of displaying thoseunits in an understandable form.

    Most clocks and watches today keep time by applying electric energy to a quartzcrystal, a system developed in the 1930s. The energy makes the crystal vibrate

    oroscillate at a constant frequency and produce regular electric pulses that regulate amotor. The motor advances the watch hands or, in a digital watch, the number display,

    by one-second increments.

    Mechanical watches use a coiled mainspring for power. The mainspring drives gearsthat cause a hairspring to oscillate, rocking a lever to and fro. The lever drives othergears that move the clock hands.

    Atomic clocks, the world's most accurate timekeepers, use the natural vibration, oroscillation, of the cesium atom as their resonator. Cesium atoms vibrate exactly

    9,192,631,770 times a second, driving a clock that is accurate to within a millionth ofa second per year. In ancient times, people used the rising and setting sun to keeptrack of time. The first devices to measure time, invented in about 3500 B.C., weresmall towers called obelisks. The changing length and position of their shadowsdivided the day into morning and afternoon. Then came sundials, which split the dayinto hours; water clocks, which measured even smaller units of time; mechanicalclocks that were much more accurate; and finally, in about 1510, spring-driven

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    clocks that led the way to clocks and watches accurate to within a minute or two a

    day.

    Connections

    1. How would your day be different if nobody had clocks or watches? What otherways could you tell time?

    2. Why is it that time seems to pass quickly when you're doing somethinginteresting or fun, and slowly when you're bored?

    Main Activity

    Water Clock:Build a clock that uses dripping water to measure how muchtime has passed.

    For many centuries, the best technology available forkeeping time was the water clock. While these clocksweren't very reliable, they worked indoors, at night, and on

    cloudy days, so they were much more useful than thesundial, the only other clock in use at the time. Over time,many styles of water clocks were invented. Here's anactivity that lets you find out just how accurate an "inflow"water clock is.

    Materials

    y 2 big eye screwsy a sturdy, wooden stick, 30 cm (12") long and 2.5 to 5 cm (1" to 2") squarey a thin, round stick or dowel, 20 to 25 cm (8" to 10") long, that fits through the

    eye screwsy 2 rubber bandsy a markery glue and a small piece of sturdy paper or cardboardy a corky 2 empty cans - medium sized, about 28 oz

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    y can opener

    1. Screw the eye screws into the 30-cm stick, the first an inch or so above thelevel of the cans, the other an inch or so below the top of the stick.

    2. Run the thin, round stick through the openings in the eye screws and insert thelower end of the stick into a cork.

    3. Fasten the large stick to the outside of one of the cans with the two rubberbands. Make sure the cork at the bottom of the thin stick doesn't rub against theinside of the can.

    4. Glue a small paper or cardboard pointer to the thin stick so that it points at, butdoesn't touch, the large stick.

    5. Use the can opener to make a tiny hole in the side of your second can as closeto the bottom as possible. You want the hole small enough so the water onlydrips out.

    6. Fill the second can with water and set it on a platform so water drips from itinto the first can. As the water slowly fills the first can, the cork will rise and

    push the thin stick and the pointer upward. Mark the starting level for thepointer on the large stick. Then every five minutes, as the water drips in, makeanother mark across from the rising pointer. At the end of the class period, youwill have calibrated your clock.

    Now, try it again and see if it remains accurate as it counts off the five-minutesegments. There are many different designs for water clocks. Look for ideas on

    building other types of water clocks or come up with your own design. Compare the

    accuracy of different designs.

    Questions

    1. Does the clock run slower or faster if you use very cold water? Why?2. Can you build two water clocks that measure time at the same rate? If not, why

    not?3. What disadvantages are there to using this type of clock?

    Look at the sweep hand of a clock and note exactly when a minutebegins. Without looking at the clock again, try to silently count off 60seconds in your head. How close did you come? Try again, but this time

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    have someone talk to you and interrupt your concentration.

    Build your own sundial with a medium-sized flowerpot filled with sand.Put a 30-cm (12") stick in the center of the pot and set it in the sun.Every hour, mark where the shadow of the stick falls on the edge of the

    pot with a piece of masking tape. If you don't move the pot, you cankeep track of time on sunny days.

    Galileo realized that a pendulum oscillates, or swings, back and forthfor the same unit of time, even as the arc of each swing decreases. Tie aweight to one end of a string and tie the other end to a stick. Lay thestick down on a table so the string is hanging free, then swing the stringlike a pendulum. Was Galileo right?

    Key Concepts

    atomic clocka very accurate clock that keeps time by measuring the natural oscillations of a cesiumatom

    horologythe science of measuring time

    obeliskan upright, four-sided pillar that tapers to a pyramid at its top

    oscillateto swing back and forth; with electricity, to switch between a high and a low charge

    quartzcrystal when placed in an electric field, a quartz crystal vibrates and generates a regular

    electric signal that is a good resonator for running clocks and watchesspring-driven clocks

    a tightly wound spring provides the energy for these clocks, but they slow down as thespring unwinds

    weight-driven clocksold mechanical clocks that used the pull of a heavy weight to provide energy to run theclock

    Resources

    Dohrn-van Rossum, G. (1996).History of the hour: Clocks and modern temporalorders. Chicago: University of Chicago Press.

    Macaulay, D. (1988). The way things work. Boston: Houghton Mifflin Company.

    Suplee, C. (1994, Nov 16).A brief history of time-keeping: How the mechanical clock

    set a new tempo for society. The Washington Post Horizons learning section, p.H1.

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    Tait, H. (1983). Clocks and watches - An illustrated history of clocks since the MiddleAges. Cambridge: British Museum Publications/Harvard University Press.

    Index of Horology: http://www.horology.com/horology

    National Institute of Standards and Technology: http://physics.nist.gov/lab.html(Click on "General Interest" in main menu, then click on "A walk through time.")

    Tapes of this episode of Newton's Apple and others are available from GPN for only$24.95.

    Please call 1-800-228-4630.For information on other Newton's Apple resources for home and school,

    please call 1-800-588-NEWTON!

    http://www.darylscience.com/Demos/Clocks.html

    Building a Water Clock

    Purpose

    To build a feedback-controlled system (a water clock) and research ways to improve the system design.

    Context

    This activity should follow student encounters with more simple systems, such as pencils, scissors, etc. In this activitystudents will begin to examine more closely the interactions between the parts of a system. The main goal of havingstudents learn about systems is not to have them talk about systems in abstract terms, but to enhance their ability toattend to various aspects of particular systems in attempting to understand or deal with the whole system.

    Planning Ahead

    Materials:

    1-liter plastic soft drink bottle with the label removed pin timer or watch that can be read to seconds ruler marking pen 100-mL graduated cylinder

    Motivation

    Begin by letting students view a picture of the largest water clock in North America, on display at the Children'sMuseum of Indianapolis. Ask students to jot down and describe some of the parts that make up the water clock. Ask

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    students to try to guess the time that the picture was taken based on the hint given at the website. The answer isgiven at the bottom of the page.

    Then let students read more about water clocks in A Walk Through Time. Focus the students' attention on the simplewater clock, or clepsydras, which is described on the page.

    As they read, ask students to write down the answers to these questions:

    What are the parts of a water clock? What is it designed to do? What advantage does it have over other devices such as sundials? (It could be used at night as well as in

    daylight.) What is the largest problem associated with water clocks? (The rate of flow of water is very difficult to control

    accurately.)

    Discuss the answers with the class.

    Development

    How A Water Clock WorksIn the first part of the activity, the class will investigate how a water clock works and the effect of one of its variableson its ability to be an accurate timepiece.

    Tell students: Early water clocks were stone vessels with sloping sides that allowed water to drip at a nearly constantrate from a small hole near the bottom. Other water clocks were bowl-shaped containers that slowly filled with waterat a constant rate. Markings on the inside surfaces measured the passage of time as the water level rose on theinside of the bowl, a result of its slowly sinking. We're going to use a soft drink bottle to make a similar device.

    Ask students to select what they consider to be the most important parts of the device.

    Procedure: Do the following as a teacher-led exploration:

    Use the pin to make a very small hole in the bottom or close to the bottom of the bottle. A hole smaller than thediameter of the pin is desirable. Let the students examine the hole.

    Holding a finger over the hole, fill the bottle with water to a level just below the shoulder where it begins to have asmaller diameter. Mark this level on the outside of the bottle. Measure the time required for 100 ml (+/- 0.5 ml) ofwater to run or drip out of the bottle. Repeat the experiment with the starting water level about halfway up the bottleand with the starting water level very low in the bottle. Plot the times as a function of the distance the starting waterlevel was above the hole in the bottle.

    Discuss the results with the class using questions such as the following:

    What do the results tell you? (The drip rate will change if the water level in the bottle changes very much.) What does this tell you about a water clock? (It might not be very accurate.)

    Now have each student write a one-sentence description of how they might improve the simple water clock made inthis demonstration. Student answers may vary, but generally they should respond that the clock could be improvedby making the drip rate more constant.

    Building a Better Water ClockIn this part of the activity, students will build a feedback-controlled robotic system that will function as a water clockthat will keep time accurately for at least two hours without human intervention.

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    Procedure: Divide the class into groups. The goal for each group is to construct a water clock that will keep timeaccurately (within +/- 1%) for at least two hours without human intervention. To accomplish this, the drip rate from thebottle has to be constant. A drip rate of 10-15 ml/min will give appropriately accurate data (when the volume that dripsout is measured). At this drip rate, 1-2 L of water will be collected in two hours and this is a small enough amount tobe manageable. Since the drip rate will change if the water level in the bottle changes very much, the water level inthe drip bottle will have to be kept pretty constant in order to keep the drip rate constant.

    The task is to design a feedback-controlled robotic system to keep the water level in the bottle constant enough tomaintain a steady drip rate. The student groups will each have to decide what "constant enough" is. The robot willneed to sense the water level in the bottle and add water as necessary (but not too much or the level will get toohigh).

    You can restrict the kind of sensors the students may use to mechanical devices (like floats) or allow them to use anymaterials from the classroom (or readily accessible in almost any household), including photocells for electro-opticalsensing, if you have them.

    The source of water could range from a large (2-L) reservoir of water to the tap, again depending on the restrictionsyou wish to place on the design. The robots can also range from ones powered only by the force of gravity to onesthat incorporate electrical components like small motors. The critical part of the robot is the control of water flow fromits source into the bottle. Again, you may restrict the options from controlling the flow through tubing by squeezing itto control by electro-mechanical devices like solenoid valves, if available.

    Provide students some time in class and outside of class to develop the concepts for their robots, check their ideas tobe sure they meet the design criteria and are safe, and then provide at least one or two periods of in-class time forpart of the construction, so you can judge how the group members are working together and to provideencouragement and reinforcement of their ideas.

    The finished robots must have a prominent sign giving the conversion factor from volume of water collected tominutes from beginning of collection.

    Students should present their finished robots to the class. Each project should be accompanied by a written reportwhich details their design, including drawings illustrate and name all of the parts of the robot system they havedesigned.

    Assessment

    Actual testing of the finished robots could be an event open to the whole school as each is tested at two or threerandom times during a two-hour run to see whether it is keeping time to within the specified +/- 1% over the entireperiod.

    Full assessment credit should be given to any group whose robot meets the specifications. Deductions for missingthe goal should be decided by you and the students together in advance of the testing.

    To push student creativity, you might want to set up some special awards and incentives for robots run entirely by theforce of gravity or by springs or by electric motors and/or for devices that show the elapsed time continuously. Yourown creativity in this regard should be restricted only by what is reasonably available in your school. The wider therange of options allowed, the more everyone will learn about whats possible with robots.

    ExtensionsStudents can learn more about robots by exploring Get a Grip on Robotics from the Tech Museum of Innovation. Thisresource provides an introduction to robotics and describes the components of robots. Animations allow you toexplore the degrees of rotation of robotic arms and fictional case stories allow you to explore some of the implicationsof robotics for humans. Other topics include robots in science fiction, industrial applications, and the use of robotsaround the world. A focus of the activity is the effect of robots on the workforce. After exploring this resource,students can engage in debates about the potential benefits and drawbacks of robots.

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    Visit The Franklin Institute's Robo-Spot for more on robotics, including Cool Robot of the Week and links to a varietyof robot resources. Students who are interested in doing research reports or science fair projects on robotics can usethese links as a starting point.

    http://www.sciencenetlinks.com/lessons.php?BenchmarkID=11&DocID=2

    It's All in the Wrist: Moving Water with the

    Archimedes Screw Pump

    Abstract

    Amaze your friends and family by moving water with just a few turns of your wrist! Nope, it's not a

    magic trick. It's simply an Archimedes screw. In this science project, you will build a very simple

    pump, called an Archimedes screw, to transfer water from a low-lying location to a higher location.

    Objective

    For this science project you will build an efficient Archimedes screw pump, using commonly foundmaterials.

    Introduction

    Archimedes of Syracuse was born in the 3rd century BC. He was one of the most importantinventors of his time because he liked to solve problems; particularly problems that would help hisItalian hometown prosper. During the Siege of Syracuse, Archimedes developed the Archimedes heatray, which used parabolic mirrors to focus the energy of the sun onto incoming enemy ships, and

    supposedly caught them on fire. For many years, several modern-day scientists didn't believe this kindof weapon could have been built. However, recently a group of students at MIT showed that anArchimedes heat ray weapon is possible. Although, they do not claim that the story is completely true.

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    Figure 1. Engraving of Archimedes of Syracuse. (eonimages.com, 2007.)

    The King of Syracuse requested that Archimedes build the biggest luxury ship possible. This shipproved to be leaky and Archimedes had to design a device to rid the hull of bilge water. So hedesigned the Archimedes screw. The screw was very effective because it got rid of the water andonly required one person to operate it. The Archimedes screw was also used to transport water fromlow-lying areas up to irrigation ditches. The design is so effective that it is still being used in manymodern-day applications. For instance, it is used to lift wastewater in treatment plants and even to liftwater at the Shipwreck Rapids water ride at Sea World in San Diego, California. It's a tool that hasnever gone out of style.

    The Archimedes screw is a positive-displacement pump. A positive-displacement pump traps anamount of fluid from a source and then forces the fluid to move to a discharge location. TheArchimedes screw is made up of a hollow cylinder and a cylindrical core. The core sits inside of thehollow cylinder. Helical blades are wound around the core and are secured tightly against the hollow

    cylinder. The helical blades create pockets between the core and the inner wall of the hollow cylinder.To use this device as a pump, one end is placed in a low-lying fluid source and then tilted up into adischarge tank. To move water, simply rotate the screw. As the screw moves, it scoops up a smallamount of water into the first pocket. On the next turn of the screw, the first pocket of water movesto the second pocket, and a new scoop of water enters the first pocket. This motion continues untilfinally the first scoop of water comes out at the other end.

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    Figure 2. Here is an inside view of an Archimedes screw pump. The screw is turned and

    water is scooped up from the river and makes it's way up the screw pockets to the canal.

    (U.S. Department of the Interior, 2004.)

    The site of the fluid to be moved and the amount of fluid to be moved determine the outer radius of

    the Archimedes screw (the distance from the center of the core to the outer wall of the hollowcylinder), the length of the tool, and how much the tool has to be tilted (the slope). But there areother parameters that are utilized to optimize the efficiency of the screw; for instance, the inner radius(the distance from the center of the core to the inner wall of the hollow cylinder), the number ofblades, and the pitch of the blades (Rorres, 2000). The pitch or period is the length of one cycle ofthe blade.

    In this science project, step into Archimedes' shoes. Design the most-efficient pump using thematerials listed in the Materials and Equipment list below. Have fun and remember that Archimedesloved solving difficult problems!

    Terms, Concepts and Questions to Start Background Research

    y Archimedes of Syracuse

    y Archimedes screw

    y Pump

    y Radius

    y Slope

    y Pitch

    y Period

    Questions

    y What other inventions did Archimedes develop?

    y What areas of science did Archimedes study?

    y What are some modern uses of the Archimedes screw?

    y Can you explain how an Archimedes screw works?

    Bibliography

    y U.S. Department of the Interior. (2004, October 26). Hydraulic Research inTransition. Retrieved April 7, 2008 from the U.S. Department of the Interior Bureau ofReclamation website: http://www.usbr.gov/pmts/hydraulics_lab/history/transition/trans1.html

    To learn more about Archimedes and his contributions, check out the following websites:

    y Rorres, C. (n.d.).Archimedes. Retrieved April 7, 2008 from this New York Universitywebsite: http://math.nyu.edu/~crorres/Archimedes/contents.html

    y Wikipedia Contributors. (2008). Archimedes. Wikipedia: The Free Encyclopedia. Retrieved April9, 2008 from http://en.wikipedia.org/w/index.php?title=Archimedes&oldid=210433020

    Check out this site for information about the Archimedes screw, as well as an animation of how itworks:

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    y Wikipedia Contributors. (2008). Archimedes Screw. Wikipedia: The FreeEncyclopedia. Retrieved April 9, 2008from http://en.wikipedia.org/w/index.php?title=Archimedes%27_screw&direction=prev&oldid=205908572

    The following pdf describes how to design an Archimedes screw.

    y Rorres, C. (2000). The Turn of the Screw: Optimal Design of an Archimedes Screw. Journal ofHydraulic Engineering, Vol. 126, No. 1, 72-80. Retrieved April 9, 2008from http://www.math.nyu.edu/~crorres/Archimedes/Screw/optimal/optimal.html

    Materials and Equipment

    y PVC pipe, -inch inner diameter, 2-foot length; available at hardware stores

    y Clear vinyl tubing, 10-foot length, with a 3/8-inch outer diameter x -inch inner diameter;available at hardware stores

    y Clear vinyl tubing, 10-foot length, with a -inch outer diameter x -inch inner diameter;available at hardware stores

    y Strong and sticky tape, such as Gorilla tape or duct tape

    y Permanent marker

    y Retractable blade knife

    y Lab notebook

    y Liquid measuring cup

    y Spoon

    y Water

    y Food coloring

    y StyrofoamTM bowls, 12-oz (2)

    y Tape (Scotch tape works fine)

    y Pen

    y Books of various thickness or pieces of plywood board; available at hardware stores (12)

    y Helper

    y Graph paper

    Experimental Procedure

    Making Your Archimedes Screw

    1. Using the PVC pipe and the -inch-inner-diameter vinyl tubing, take a piece of strong tape

    and tape one end of the tubing to the outside of one end of the pipe such that a -inch lengthof tubing is hanging off the end.

    2. Carefully wrap the tubing around the pipe in regular intervals until you come to the other endof the pipe. From that point, add a inch and mark that spot on the vinyl tubing with apermanent marker.

    3. Unwrap the tubing and cut it with the blade knife at the mark. Ask an adult for assistancewhen using the knife.

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    4. Rewrap the cut piece of tubing around the pipe in regular intervals and tape it down withpieces of strong tape along the pipe. There should be a -inch of tubing hanging off both endsof the pipe, past the sections that you taped down. The starting section will reach into thewater, allowing it to travel through the tube and the end section will help get the water out. Bywrapping the tubing in regular intervals you are establishing the period of the tubing.

    5. Count the number of times you have wrapped the tubing around the PVC pipe. Divide 2 feet

    (the length of thePVC pipe) by the number of times you wrapped the tubing around the

    PVCpipe. This value is the period and is in units of feet. Note this down in your lab notebook in a

    data table similar to the one shown at the bottom of the Experimental Procedure.

    Figure 3. Experimental Archimedes screw.

    Setting Up Your Bowls

    1. In your liquid measuring cup, mix a few drops of food coloring in 1 cup of water. This makesthe water easier to see.

    2. Now make tape loops with the Scotch tape to stick to the bottom of one of the Styrofoambowls and press the bowl onto a table so it stays in place.

    3. Pour a cup of the colored water into the other Styrofoam bowl. With a pen, mark the levelof the water on the bowl. Pour the water back into the measuring cup.

    4. Making more tape loops, carefully tape the marked bowl onto one of the books or plywood

    boards so that it will stay in place during the experiment. The bowl on the book or plywood isthe discharge bowl.

    Testing Your Experimental Setup

    1. Now you are ready to test your experimental setup and determine what slope works best soyou can run your trials. Place the marked bowl on the book or plywood about 2 feet away fromthe bowl taped to the table. Pour the 1 cup of water into the bowl on the table.

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    2. Place your Archimedes screw across the two bowls, as shown in Figure 4. Be sure the extra inch of tubing hanging off the end is in the bowl of water on the table. Turn the screw so thatevery time the end of the tube goes into the water it scoops up some of the water.

    3. Tilt the screw so that one end is in the water and the other end is in or close to the bowl thatyou want to move the water to, which in this case, is the bowl taped to the book or plywood.

    Figure 4. Experimental setup.

    4. Make sure that as you turn the screw, the water doesn't fall back out of the screw. If thewater does fall out, adjust the tilt of the screw, the placement of the bowls, and/or the heightof the discharge bowl. Use an extra book or board if needed.

    5. Turn the screw a few times to make sure that the water is traveling through the tubing.Experiment with how fast you can turn the screw and still move water through the tube. Goingtoo fast might not lead to positive results.

    Running YourTrials

    1. Now you're ready to start running your trials. Hold the screw vertically and empty all of thewater from the tubing and the discharge bowl back into the bowl on the table.

    2. Using your permanent marker, make a mark on the middle of the pipe at the position whenthe vinyl tubing is just about to enter the water. This will help you keep track of the number ofturns you make. Turn the pipe so the mark is facing up, and then start turning the screw untilthe mark is facing up again. You have made one turn and should see some water in thetubing. On each successive turn, the tubing should be completely under water so that youscoop as much as possible.

    3. Continue turning the screw until a cup of water is in the discharge bowl. Make sure that youmaintain the same tilt the whole time you are turning the screw. Also make sure that you arescooping up water on every turn. Have your helper help you count the number of turns as you

    go along. You can gauge when you have about a cup in the discharge bowl, based on thepen marking you made when you first started. To be exact, confirm that you have a cup ofwater in the discharge bowl by pouring it into the measuring cup. One person should hold thescrew in place and the other person should carefully remove the bowl from under the screwand measure the water.

    a. If the amount of water in the discharge bowl is not a cup, continue turning thescrew until you get a cup.

    b. If the amount of water in the discharge bowl is greater than a cup, empty all of thewater back into the first bowl and restart this step.

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    4. Keep track of the number of turns it takes to move a cup of water from the starting bowlinto the discharge bowl. Note this information in your lab notebook.

    5. Repeat "Running Your Trials" two more times. Every time that you start a new trial, empty allof the water back into the measuring cup. Make sure that you have a full cup of water at thestart of each trial. If you do not, then add water into the measuring cup until you have 1 cup.For each trial, note the information in your lab notebook.

    6. Calculate the average of the results of the three different trials and record them in your datatable.

    7. Now unwrap the -inch-inner-diameter tubing from the pipe. Take the -inch-inner-diametertubing and wrap that around the -inch-inner-diameter PVC pipe. Use the same period as youdid for the -inch tubing. Wrapping this tubing will be harder than it was with the -inchtubing because the tubing is larger and stiffer. Have your helper assist you with wrapping.Repeat the entire experiment with the new Archimedes screw. Remember to record the datayou collect in your lab notebook.

    8. Plot your data. Label the x-axis Design and the y-axis theAverage Number of Turns to Move a Cup ofWater. Which design is more effective at moving water? Why?

    Design Period Number of Turns to Move Cup of Water

    -inch tubing wrapped on -inch pipe

    Trial #1

    Trial #2

    Trial #3

    Average of all trials

    -inch tubing wrapped on -inch pipe

    Trial #1

    Trial #2

    Trial #3

    Average of all trials

    Variations

    y Change the period of the tubing to increase or decrease the number of wrappings andinvestigate how this affects the number of turns it takes to move cup of water from thebowl on the table to the discharge bowl.

    y Change the diameter of the pipe. Try using a 2-foot-long, 1-inch-inner-diameter PVC pipe withthe -inch-inner-diameter vinyl tubing. Does it make a difference?

    y For more science project ideas in this area of science, see Mechanical Engineering ProjectIdeas.

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    Credits

    Michelle Maranowski, PhD, Science Buddies

    This project is based on a design for a homemade Archimedes screw from this website:de Campos Valadares, E. (2005, September 23). Fun Physics Experiments with Household Objects:

    Hand-OperatedWater Pump (Arichmedes' Screw). Retrieved April 9, 2008from: http://www.informit.com/articles/article.aspx?p=413663&seqNum=4

    Last edit date: 2008-05-06 12:00:00

    http://www.sciencebuddies.org/science-fair-projects/project_ideas/ApMech_p039.shtml

    There are three basic types of science fair projects:

    he experimental type - investigates a scientific issue by asking a question, testing ahypothesis, performing an experiment and drawing conclusions from it - what we callthe scientific method.

    The experimental type is the most common (but not always the best choice).

    For example:

    y The effect of exercise on blood pressurey

    Which bleach works the best?y Light effects on seed germination

    y The effect of the amount of storage space and RAM on the speed of a computer

    E.g.

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    Multiple Rotors: A High

    Efficiency Windmill Design

    Project Information

    Project Information

    Dayna Walker

    Team size: 1Grade 7-9

    Engineering - Experimental

    Level: Advanced

    Traditional Website constructed using Softquad HotMetal Pro

    Graphics: Adobe Photoshop, Ulead Photoimpact & MetalWorks

    Charts: Microsoft Excel

    Hardware Tools: Digital Camera

    Project Summary"Watts Up With Torque!" is Phase 2 of my 2003 project, "Torque it Up!". The

    results from Phase 1 strongly supported my hypothesis that multiple rotors

    would produce more torque and mechanical power than a single rotor.

    The purpose of this project was to determine if multiple rotors would increase

    the electrical output of a horizontal axis windmill. A laboratory scale windmill

    was designed and built. Torque, the force created by the rotating windmill axis,

    was used to turn the axle of three sizes ofDC motors and generate electricity.

    Electrical current in mAmps and electrical force in mVolts were measured andelectrical energy in mWatts calculated. The experiment was designed to measure

    the effect of the independent variables (rotor size, placement, number, fan speed,

    motor size) on the dependent variables (wind speed, RPM, mAmps and mVolts).

    Twelve rotor variables were tested at two fan speeds, using three sizes ofDC

    motors. Each measurement was repeated ten times. RPM and wind speed were

    used to calculate tip speed ratio. Statistical analysis was used to assess the quality

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    of the data collected.

    Multiple rotors produced more electicity than a single rotor and operated at

    lower wind speeds. Adding a second rotor produced the largest increase (over

    2000%) in electricity generated. Overall, three 28 cm rotors, placed side by side,

    with offset blades, coupled to a 12 V DC motor produced the most electrical

    energy. This rotor combination consistently had the highest tip speed ratios and

    produced the most electrical energy at both fan speeds and with all three motors.

    Abstract

    Watts Up With Torque!

    Multiple Rotors: A High Efficiency Windmill Design

    The overall efficiency of a windmill is the amount of electricity that can be

    generated over time on a cost basis. Two important factors that determineoverall windmill efficiency are the ability to use low velocity wind and the ability

    of the windmill to convert the kinetic energy of the wind into electrical energy

    (conversion efficiency).

    Currently, the most popular windmill design utilizes a large, single, three-blade

    rotor. It is obvious that "unused" wind passes between the blades of these three-

    blade systems. Rotors with more blades, such as those used on farms for

    irrigation, will turn at lower wind speeds, and have high conversion efficiency.

    However, these multiple blade rotor systems are subject to higher loads and

    unable to withstand extreme winds. My design is to utilize multiple three-bladed

    rotors. Multiple small rotors weigh less than a single large rotor, are easier to

    produce and transport, and less subject to fatigue.

    The purpose of this project was to determine if multiple rotors would increase

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    the electrical output of a horizontal axis windmill. Torque, the force created by

    the rotating windmill axis, was used to turn the axle of various sized DC motors

    and generate electricity. Three sizes ofDC motors were used to assess whether

    the rotor combinations produced enough torque to start, and continuously turn

    larger motors. Electrical current in mAmps and electrical force in mVolts weremeasured and electrical energy in mWatts calculated.

    My engineering objectives were to design and build a multiple rotor, horizontal

    axis, laboratory scale windmill, complete with couplers to connect the axis to the

    axle of various DC motors. The scale model was used to determine the effect of

    different rotor attributes (size, number, distance apart and orientation of the

    rotors) on the resulting torque and electricity generated with the various sizes of

    DC motors. The rotor arrangement and motor that produced the most electricity

    was identified.

    My hypothesis was that multiple rotors, blades offset, closely spaced would

    produce more torque and generate the most electrical energy. The experiment

    was designed to measure the effect of the independent variables (rotor size,

    number, placement, fan speed and motor size) on the dependent variables (wind

    speed, RPM, mAmps and mVolts). Wind speed was measured with an

    anemometer, RPM with a digital tachometer and mAmps and mVolts with a

    digital multimeter. In all, 12 rotor variations were tested at medium and high fanspeeds, using three sizes ofDC motors. Each measurement of wind speed, RPM,

    mAmps and mVolts was repeated ten times. The RPM and wind speed

    measurements were used to calculate tip speed. Statistical analysis was

    performed to assess the quality of the data collected.

    My engineering objectives were met and my hypothesis was correct. Multiple

    rotors produced more electricity than a single rotor. There were substantial

    differences in the amount of electrical energy produced depending on rotor size,

    number, orientation, spacing, wind speed and size of the DC motor. Adding a

    second rotor produced the largest increase (over 2000 %) in electricity

    generated. Over all, three 28-centimeter (cm) rotors, placed side by side with the

    blades offset and coupled to a 12 V DC motor produced the most electrical

    energy. This rotor combination consistently turned at the highest RPM and

    produced the most electrical energy output at both fan speeds and with each of

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    the three motors. However, the addition this third rotor only increased the

    amount of energy produced by two rotors by an average of 29 %.

    My results suggest that the overall efficiency of windmills could be substantially

    increased through the addition of a second rotor.

    PurposeThe purpose of this project is to determine if multiple rotors will increase the

    electrical energy output of a horizontal axis windmill. Torque, the force created

    by the rotating horizontal axis, will be used to turn the axle of various sized DC

    motors and generate electricity. A digital multimeter will be used to measure

    mAmps and mVolts and electrical energy output in mWatts calculated.Revolutions per minute (RPM) and wind speed measurements will be used to

    calculate tip speed ratio. Various sized motors were used to assess the ability of

    the rotor variation to start and continuously turn larger motors.

    Opposition to the production of electricity from fossil fuels is rising and the

    earth's non-renewable resources are being depleted. Twenty percent of all

    greenhouse gases released in Ontario in 2001, were produced by five coal fired

    power plants. Wind power offers a pollution free, electricity generating

    alternative, using a renewable energy source. The cost of wind generated

    electricity is declining, in comparison with other energy sources. Wind power iscurrently one of the fastest growing sources of electricity generation in the world,

    growing an average of 25% per year.

    Most wind turbines are the single rotor, classic Danish three-blade design.

    Although there has been a large amount of research on windmill design, there

    appeared to be none published on the use of multiple rotors.

    Results from Phase 1 of this project (Torque it Up!), indicated that multiple

    rotors did increase the torque of a horizontal axis windmill and could potentially

    produce more electrical energy. Subsequent to my initial research, I did find thatresearchers in California have been testing a multiple rotor windmill.

    This research could impact on the construction of wind turbines. Multiple small

    rotors weigh less, are easier to produce and transport and are less subject to

    fatigue. Multiple rotors turn at lower wind speeds and produce more torque.

    Increased torque may permit increased turbine size and produce more electricity

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    than that of a single rotor wind turbine.

    The use of multiple rotors could result in lower construction costs because rotor

    blades would be smaller, fewer support towers would be required and the overall

    efficiency of wind turbines would increase.

    Engineering ObjectivesMy engineering objectives were to design and build a multiple rotor, horizontal

    axis, laboratory scale windmill that could be coupled to the axle of various sizes

    ofDC motors. The scale model was used to determine the effect of different rotor

    attributes (number, size, distance apart and orientation of the rotors) and size ofDC motor on the resulting mAmps and mVolts generated. The rotor

    arrangement and motor that produced the most electrical energy output was

    identified.

    HypothesisIf a three-blade rotor on a horizontal axis windmill generates a given amount of

    electrical energy, then adding additional three-blade rotors will increase the

    amount of electrical energy output.

    I predict that the distance between the rotors will affect the amount of electrical

    energy produced and that there is an optimal distance.

    I predict that the orientation of the rotors (i.e. blades off set or in line) will affect

    the amount of electrical energy produced.

    I predict that the size of the rotors will affect the amount of electrical energy

    produced.

    I predict that single rotors will be able to start and continuously turn smaller DC

    motors but will be unable to start turning larger DC motors.

    Background

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    Most wind turbines are the single rotor, classic Danish three-blade design. These

    blades are often more than 50 meters in length, requiring towers that are 100

    meters in height. It is obvious that unused wind passes between the blades of

    these three-blade systems. Smaller diameter multi-blade rotors, such as those

    used on farms for irrigation, will turn at lower wind speeds but are subject to

    higher stress and unable to withstand extreme wind conditions. My design is to

    utilize multiple three-blade rotors. Multiple small rotors weigh less than a single

    large rotor, are less costly and easier to produce and transport and less subject to

    fatigue.

    This project, "Watts up with Torque!" is Phase 2 of my 2003 project "Torque it

    Up!" The purpose ofPhase 1 was to determine if multiple rotors would increase

    the torque of a horizontal axis windmill. Torque is the force created by a rotating

    shaft.

    In Phase 1, force in Newtons was measured using a spring scale and torque in

    Newton-Meters calculated using the formula:

    Torque (N-M) = Force (N) x Radius (M)

    The revolutions per minute (RPM) of the rotor was used to calculate blade tip

    speed and mechanical energy (power in Watts) was calculated using the

    formula:

    Mechanical Energy (Watts) = Torque x Blade Tip Speed

    The results from Phase 1 strongly supported my hypothesis. Every test usingmultiple rotors produced more torque than a single rotor and the mechanical

    power produced was dependent on rotor size, number, blade orientation, rotor

    spacing and wind speed.

    Subsequent to the completion ofPhase 1, I found that researchers in California

    have been testing a multiple rotor windmill. Preliminary results from this testing

    indicate that their design, the "Quadrunner", using multiple rotors, coupled to a

    single shaft, will harvest more wind and energy, at less cost than current models

    using a single rotor.

    This further convinced me that my research of a multiple rotor windmill design

    had merit and was worthwhile pursuing.

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    Phase 2: Watts Up With Torque!

    The overall efficiency of a windmill is the amount of electricity that can be

    generated over time on a cost basis. Two important factors that determine

    overall windmill efficiency are the ability to use low velocity wind and ability ofthe windmill to convert the kinetic energy of the wind into electrical energy

    (conversion efficiency).

    In Phase 2, I wanted to further my research of multiple rotor windmills and

    assess the conversion efficiency utilizing a more direct approach. This project

    required a device to generate electrical energy from the rotating horizontal

    windmill axis. Direct current (DC) motors are readily available in various sizes.

    They work as motors when you apply electricity to them, but they also work as

    generators when you turn the motor axle. Lower voltage motors such as 3 Volt

    (V), are easier to start up but have a lower electrical output. Higher voltagemotors, such as 12 V, require more torque to start the rotation, but produce

    more electricity.

    The common units used to measure the quantity of electricity are:

    Volts: electrical force or pressure behind the electrons in a current Amps:

    number of electrons flowing past in a second

    Watts: total amount of electrical energy per second and is equal to Watts = Volts

    x Amps

    For Phase 2, I modified the laboratory scale horizontal axis windmill model sothat the axles of various sizes ofDC motors could be coupled to the windmill axis.

    The electricity generated by rotor combinations that were able to start and

    continuously turn the motor was measured and conversion efficiency assessed at

    two wind speeds.

    Review of Literature

    What is wind?

    Wind is air in motion, caused by the uneven heating of the Earth by the sun.

    Wind occurs when warm air rises, and cooler air moves in to fill the space. It is

    estimated that 2% of the solar energy reaching the earth is converted into wind

    energy. Air is constantly being interchanged between the warm tropics and the

    cold polar caps. The rotation of the Earth also produces wind.

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    The sun radiates the most heat over the equator

    and therefore the air there is warmer. Air from

    both hemispheres is constantly moving toward

    the equator. The rotation of the Earth causes thecool winds to be deflected from east to west. As

    the surface of the earth heats and cools unevenly,

    pressure zones are created that make air move

    from high pressure to low pressure areas.

    What is wind energy?

    The process by which the kinetic energy of wind is used to generate mechanical

    power or electrical energy is known as wind power or wind energy. Kinetic

    means being related to or produced by motion such as the blowing wind.

    A windmill converts the force of the wind into a turning force acting on the rotor

    blades. The strength of this turning force is known as torque.

    Wind speed and energy:

    The amount of energy that can be captured from the wind is exponentially

    proportional to the speed of the wind. If a windmill were perfectly efficient, the

    power generated is approximately equal to:

    P (watts) = 1/2 D (air density) x A (area of rotor) x V cubed (wind velocity)

    Air density at sea level and 14 degrees C = 1.225.

    Therefore, if wind speed is doubled, the power in the wind increases by a factor

    of eight, i.e. 2 x 2 x 2. In reality, because wind turbines are not perfectly efficient,

    changes in wind velocity do not have such a dramatic effect on wind power. Betz'

    Law states that you can only convert approximately 59 % of the wind energy to

    mechanical energy using a wind turbine. However, small changes in velocity do

    impact on available energy, making wind speed an important factor to consider

    in the placement of a wind turbine.

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    The chart below illustrates that a doubling of wind velocity increases power

    available by a factor of eight.

    History of Wind Power:

    Wind has been used for centuries to propel ships and the wind routes were well

    known and used by explorers such as Magellan and Columbus.

    Wind power was used as a source of mechanical energy on land for thousands of

    years. The Babylonians constructed windmills for irrigation as early as 1700 BC

    and Europeans were using windmills by 1000AD.

    The Dutch used windmills to drain the land and

    used eight basic types. Dutch settlers introduced

    windmills to the United States in the early 1600s.

    Daniel Halliday invented a new style of windmill,

    which many believe encouraged the rapid settling of

    the American West. More than 6.5 million windmills

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    were sold in the US between 1880 and 1935. They were used to pump water,

    grind grain and cut lumber. Some small electrical generating systems were used

    to produce direct current by 1900. Cheap electricity was introduced in th 1940s

    and most of the wind powered generating systems in rural areas were considered

    obsolete and fell into disuse.

    Wind turbine is the name given to a complete,

    electricity generating windmill. In its simplest

    form, it consists of a tower, blades, generator

    and, if electricity is to be stored, batteries.

    There are large windfarms in many areas of

    the world.

    Wind Turbine Rotor Design:There has been a great deal of research on rotor design including whether the

    turbine will be upwind (rotor facing the wind) or downwind (rotor on the lee side

    of the tower), the number, size and shape of blades, the load (forces acting on the

    rotor in high wind) and other rotor aerodynamic considerations.

    Generally speaking, larger windmill rotors and higher wind speed, produce more

    power. The old Western windmills had many, wide blades. During very high

    winds, they were exposed to extremely high forces known as loads and were often

    damaged. Modern wind turbines by law, have to be able to withstand extreme

    winds that may only occur once every 50 years.

    Most wind turbines are the classic Danish three-bladed design with the rotor

    positioned up-wind (facing the wind). Even numbers of blades cause instability.

    Some designs are two bladed, saving the cost of a blade and reducing rotor

    weight. They need higher rotational speeds to produce the same amount of power

    as a three bladed design. These speeds produce more noise. There are one bladed

    designs that require a counter-balance on the other side of the hub. They also

    require higher rotational speed.

    Aerodynamics of Rotors:Rotor blades act like airfoils. An airfoil is a structure around which air flows

    creating lift. Rotor blades have a special shape so that when the wind passes over

    them, it moves faster over one side. Bernoulli's Principle states that increased air

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    2. mVolts

    3. RPM

    4. Wind Speed

    Independent Variables:

    1. Fan speed2. Number of rotors (1, 2 or 3)

    3. Rotor spacing

    4. Position of rotor on horizontal axis (i.e. rotor blades offset or in line)

    5. Size of the DC motor (1.5-3V, 9-18V or 12V)

    Controls:1. The same test station, retort stand supporting the motor, and electric fan were

    used for all tests.

    2. All of the testing was done in the same location at ambient temperature.

    3. The equipment was positioned exactly the same for every test. The test stationand retort stand were clamped onto the workbench and the required fan position

    was marked on the floor.

    4. The rotor placement on the axis was checked with a T-square to ensure that

    the rotors were perpendicular to the axis.

    5. A ruler was used to mark the required distance between rotors.

    6. The same measuring instruments were used for all tests.

    7. The anemometer was held in approximately the same position for every

    measurement.

    8. The tachometer was placed so that the beam was centered on the reflective

    tape. 9. RPM and multimeter readings were not taken until the rotors had

    reached maximum and stable rotational speed.

    10. All testing was repeated a total of ten times to ensure accuracy and

    reproducibility.

    Experimental Design

    Chart

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    Material & Equipment

    Equipment

    3 bladed propeller 28 cm (3)

    3 bladed propeller 20 cm (3)

    3 DC motors (1.5-3V, 9-18V, 12V)

    0.635 cm (1/4") round stainless steel rod 48 cm in length (1)

    0.635 cm U bolts 16 cm in length (2)

    bearings (2)

    0.635 cm washers (4)

    0.635 cm nuts (4)composite wood block 14 cm x 20.5 cm x 3.5 cm (1)

    wood block 14 cm x 20.5 cm x 3.5 cm (2)

    0.635 cm compression lock washer (1)

    0.635 cm plastic cap (1)

    10-24 set screws

    digital multimeter

    anemometer

    digital photo tachometer

    retort stand (1)

    three speed electric fan (1)

    Tools:Drill with #25 drill bit and " drill bit

    10-24 tap

    Allen key set

    Black and Decker Workmate bench (1)

    "C" clamps (2)

    measuring tape (1)

    protractorruler (1)

    Test Unit Construction

    1. Holes were drilled on the hub of each propeller, between each blade with the

    #25 drill bit. Each hole was tapped with a 10-24 tap. This allowed for the

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    insertion of 10-24 set screws (3) on each propeller. The set screws were used to

    fasten the propeller to the steel rod.

    2. Four " holes were drilled through the composite wood block as follows:

    3. The U bolts were placed over the bearings, through the drilled holes and

    anchored with washers and nuts.

    4. The steel rod was inserted through the bearings.

    5. The lock washer was placed on the rod at the first bearing to anchor the

    bearing.

    6. Rotors were placed on the rod in various positions and combinations during

    testing and the set screws tightened using the Allen key.

    7. The plastic cap was placed at the rotor end of the steel rod.

    8. The test unit and retort stand were clamped on a workbench to hold it stable.

    Test Unit Schematic:

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    ProcedureNote: The manipulation of dependent variables is detailed on the previous

    experimental design chart. In total, there were 12 rotor variables manipulated,using one, two or three rotors, three sizes ofDC motor at medium and high fan

    speeds. Each variation was tested ten times.

    1. The rotor(s) was/were attached to the horizontal axis. The plastic end cap was

    placed on the end of the axis.

    2. A DC motor (1.5-3 V, 9-18 V or 12 V) was coupled to the other end of the axis

    and the leads of the multimeter attached to the poles of the motor using electrical

    connectors.

    3. The fan speed was set at medium or high and the rpm and wind velocity at the

    rotor end of the axis were measured using the digital tachometer andanemometer and recorded.

    4. Step 3 was repeated a total of ten times.

    5. Ten measurements each of mAmps and mVolts were taken using the digital

    multimeter.

    6. If the rotor variation failed to start and continuously turn the DC motor, the

    rotor variation RPM was equal to zero and testing of that variation stopped.

    Caution: The rotating blades could cause serious injury. Care was taken toensure that body parts, hair and clothing were always kept clear of the moving

    rotors.

    ObservationsObservations for each rotor variable manipulation were recorded on the

    following data worksheet. As noted previously, each of the 12 rotor variables was

    tested at medium and high fan speeds, using three sizes ofDC motors and ten

    measurements each of wind speed, mAmps, mVolts and RPM were taken. In

    total, 72 of the following worksheets were completed.

    Data Worksheet

    Date:______Independent Variables:

    Motor Size:_____Fan Speed: _____

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    Rotor 1 Size:_______

    Rotor 2 Size:_______

    Rotor 3 Size:________

    Number of Rotors: ___

    Rotor 1 Position:_____

    Rotor 2 Position:____Rotor 3 Position:

    Observations for the 12 Rotor Variables

    and Each of the Three Motor Sizes

    Wind speed, RPM, mAmps and mVolts were measured ten times each, at each

    fan speed, for each of the 12 variables and each of the three motors. Mean,

    standard deviation (SD), coefficient of variation (CV) and mWatts were

    calculated.

    OS = blades offset; IL = blades in line

    Motor Size: 1.5-3.0 V

    Trial #WindSpeed(m/s)

    mAmps mVolts RPM

    1

    2

    3

    4

    5

    6

    7

    8

    9

    10

    Average

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    Rotor Variable 1: 1-28 cm rotor

    Rotor Variable 2: 2-28 cm rotors, 0 cm apart

    Rotor Variable 3: 2-28 cm rotors, 3.5 cm apart

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    Rotor Variable 4: 2-28 cm rotors, 5 cm apart

    Rotor Variable 5: 2-28 cm rotors, 7 cm apart

    Rotor Variable 6: 3-28 cm rotors, 3.5 cm apart

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    Rotor Variable 7: 3-28 cm rotors, 3.5 cm apart, rotors 1 & 3 in line and rotor 2

    offset

    Rotor Variable 8: 2- 20 cm rotors, 0 cm apart

    Rotor Variable 9: 3-20 cm rotors, 3.5 cm apart

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    Rotor Variable 10: 3-20 cm rotors, 3.5 cm apart, rotors 1 and 3 in line and

    rotor 2 offset

    Rotor Variable 11: 3-28 cm rotors, 0 cm apart

    Rotor Variable 12: 3-20 cm rotors, 0 cm apart

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    Motor Size: 9-18 V

    Rotor Variable 13: 1-28 cm rotor

    Rotor Variable 14: 2-28 cm rotors, 0 cm apart

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    Rotor Variable 15: 2-28 cm rotors, 3.5 cm apart

    Rotor Variable 16: 2-28 cm rotors, 5 cm apart

    Rotor Variable 17: 2- 28 cm rotors, 7 cm apart

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    Rotor Variable 18: 3-28 cm rotors, 3.5 cm apart

    Rotor Variable 19: 3-28 cm rotors, Rotors 1 and 3 IL, Rotor 2 OS

    Rotor Variable 20: 2-20 cm rotors, 0 cm apart

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    Rotor Variable 21: 3-20 cm rotors, 3. 5 cm apart

    Rotor Variable 22: 3-20 cm rotors, 1 & 3 IL and 2 OS

    Rotor Variable 23: 3-28 cm rotors, 0 cm apart

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    Rotor Variable 24: 3-20 cm rotors, 0 cm apart

    Motor Size: 12 VRotor Variable 25: 1-28 cm rotor

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    Rotor Variable 26: 2-28 cm rotors, 0 cm apart

    Rotor Variable 27: 2-28 cm rotors, 3.5 cm apart

    Rotor Variable 28: 2-28 cm rotors, 5 cm apart

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    Rotor Variable 29: 2-28 cm rotors, 7 cm apart

    Rotor Variable 30: 3-28 cm rotors, 3.5 cm apart

    Rotor Variable 31: 3-28 cm rotors, 3.5 cm apart, Rotors 1 & 3 IL, Rotor 2 OS

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    Rotor Variable 32: 2-20 cm rotors, 0 cm apart

    Rotor Variable 33: 3-20 cm rotors, 3.5 cm apart

    Rotor Variable 34: 3-20 cm rotors, 3.5 cm apart, Rotors 1 & 3 IL, Rotor 2 OS

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    Rotor Variable 35: 3-28 cm rotors, 0 cm apart

    Rotor Variable 36: 3-20 cm rotors, 0 cm apart

    CalculationsmWatt Calculation from mAmp and mVolt measurements:mWatts were calculated using the following formula:

    mWatts = mAmps X mVolts

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    The data collected for each rotor variable was input into an Excel spreadsheet to

    calculate the mean, standard deviation and coefficient of variation of the ten

    measurements each of wind speed, mAmps, mVolts and RPM. A shortened

    example of the spreadsheet is shown below,to provide the formulas used to

    calculate the statistics.

    Tip Speed Ratio Calculations:Additional calculations were done to calculate the Tip Speed Ratios of each rotor

    variable at medium and high fan speed.Blade Tip Speed = RPM X Pi X Rotor Diameter / 60

    Pi = 3.14Tip Speed Ratio = Blade Tip Speed (m/s) /Wind Speed (m/s)

    A shortened example of the Excel spreadsheet may be seen below to show the

    formulas used for the calculations.

    ResultsThe overall efficiency of a windmill is the amount of electricity that can be

    generated over time on a cost basis. Two important factors that determine

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    overall windmill efficiency are the ability to use low velocity wind and the ability

    of the windmill to convert the kinetic energy of the wind into electrical energy

    (conversion efficiency).

    The results show that multiple rotors operated at lower windspeeds and had a higher conversion efficiency.

    1. Adding a second 28 cm rotor, coupled to the 1.5 - 3 V motor, increased the

    amount of electricity generated by 4500% at medium fan speed and 2324% at

    high fan speed.

    2. A single 28 cm rotor did not produce enough torque to start and continuously

    turn the larger motors (9-18 V and 12 V) at either fan speed.

    3. Adding a third rotor increased the amount of electricity generated by tworotors an average of 28 %.

    4. Three 28 cm rotors, with 0 cm distance between the rotor hubs and with the

    nine blades offset 40 degrees generated the most electricity for all three motor

    sizes.

    5. This rotor combination also produced the highest tip speed ratios.

    6. There is an inverse relationship between rotor spacing and electricity

    generation. As the spacing between the rotors increases, electricity generation

    decreases.

    7. Interestingly, three 28 cm rotors, spaced 3.5 cm apart, with the blades of rotor

    one and three inline and the blades of rotor two offset 60 degrees, produced more

    electricity than the same rotor spacing with all blades offset 40 degrees.

    A summary of all calculated means of wind speed, mWatts and

    tip speed ratio can be seen below.

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    The highlighted data below displays a summary of five rotor variables, including

    those that produced the highest mWatts and tip speed ratios.

    Results

    Note: Rotor Variables are Charted from 1 to 12, left to right.

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    Statistical Analysis

    Statistics are a way of assessing the quality of the data collected. Standard

    Deviation (SD) is a mathematical calculation used on a set of data to assess the

    amount of scatter or dispersion from the mean, or average. It is an indication of

    accuracy. If all data points are exactly the same, the SD would be equal to 0.

    Coefficient of Variation (CV) is a mathematical calculation (standard deviation x

    100 /mean) that provides information that can be used to compare different sets

    of data. A CV of 10% is considered acceptable.

    Wind Speed Measurements:The differences in wind speed wereinsignificant with a highest SD of 0.19 and a highest CV of 3.0%. The chart

    below is a summary of all wind speed measurements and statistical analysis.

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    Grand Mean of Wind Speed Measurements:A grand mean of all medium wind speed measurements was calculated as 5.6

    with a SD of .12 and CV of 2.14%.

    A grand mean of all high wind speed measurements was calculated as 6.44 with a

    SD of 0.089 and CV of 1.38%.

    The chart below shows the grand mean calculations of wind speed. Overall,differences in the wind speed at each of the fan speeds for each set of

    observations was insignificant.

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    mAmp Measurements:

    The highest SD was 2.73 and CV was 10.74%. There was only one observation

    set with a CV for mAmps greater than 5%. Overall, the measurements were

    quite reproducible. The chart below shows the means and statistics for all mAmp

    measurements.

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    mVolt Measurements: The highest SD was 13.12 and CV was 7.08%. Thechart below shows all of the mVolt statistics.

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    RPM Measurements:The highest SD was 20.98 and the highest CV was

    6.86%. The chart below shows the statistics for the RPM measurements.

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    Summary ofStatistical AnalysisThe coefficient of variation for all the data collected was acceptable (i.e. < 10%),

    with the exception of the mAmp results for one rotor variable at medium fan

    speed. The rotational speed of that particular rotor was relatively low and

    produced slightly more erratic results.

    Overall, the data collected was accurate and precise.

    Conclusions

    My engineering objectives were met and the design of the laboratory scale model

    accomodated my experimental design. The results supported my hypothesis as

    follows.

    I predicted that the number of rotors and their size, placement and orientation

    on a single horizontal axis windmill would affect the amount of torque and

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    electrical energy produced. I predicted that the size of the DC motor would affect

    the amount of electrical energy produced and that some rotor variables would be

    unable to start and continuously turn the axle of larger DC motors.

    1. Larger rotors produce more torque and electrical energy than smaller rotors.

    2. Increasing the number of rotors from one to two increases the amount of

    electrical energy generated by over 2000%.

    3. Single rotors were unable to start and continuously turn larger motors .

    4. Rotor size, number, placement and blade orientation affected the amount of

    torque and electrical energy produced.

    Overall, three 28-cm rotors, placed 0 cm apart with all of the blades offset 40

    degrees, produced the most torque and electrical energy, and the highest tip

    speed ratios. This rotor variation produced 5448 % more electrical energy at

    medium fan speed, and 2593% more electricity at high fan speed than a single

    28-cm rotor.

    However, adding a third rotor increased the amount of electricity generated by

    two rotors an average of 28%.

    The largest increase in electricity generated was from increasing the number of

    rotors from one to two.

    The results show that multiple rotors operated at lower wind speeds and had

    a higher conversion efficiency.

    DiscussionThis was a really interesting project and I enjoyed working on it. I wanted to do

    a project that was important and relevant to society. Phase 1, the 2003 "Torque

    it Up!" project produced results that strongly supported the idea that a multiple

    rotor windmill design was potentially more efficient than conventional three

    blade windmill designs.

    In Phase 2, "Watts Up with Torque", I wanted to further my research and use a

    more direct approach than torque, to measure windmill efficiency.

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    For the project "Watts Up with Torque!", I was originally going to use a pulley

    system connected to the windmill axis and the axle of the motor. I quickly

    discovered that this was not a viable option. The pulley kept slipping and when

    tightened, pulled the motor out of alignment. A visit to a local specialty model

    airplane shop proved successful. I was able to purchase couplers to connect the

    windmill axis to the motor axle as a direct drive. The couplers allowed me to

    connect and disconnect the DC motors relatively easily. This modification

    ensured that errors in measurement were minimized.

    The use of couplers and various sizes ofDC motors allowed me to not only

    measure the electricity generated, but also allowed me to assess the ability of a

    rotor variable to start and continuously turn the axle of a motor.

    "Watts Up with Torque!" started out as an expansion ofPhase 1. I wanted to test

    the effect of more than two rotors and the associated variables of placement,

    blade orientation and size on electricity generation. Choosing to test various sizes

    ofDC motors provided the added bonus of verifying my previous results about

    torque.

    This project allowed me to learn how to use additional devices such as the

    multimeter for measuring mAmps and mVolts and the DC motors as generators.

    The experiments taught me how careful I had to be in positioning the

    instruments and being patient enough to wait until the RPM of the rotors

    stabilized before attempting multimeter measurements.

    In all, I planned to collect 2880 observations. The actual amount of data collected

    was less because some of the rotor variables failed to start and/or continuously

    rotate. I learned more about how to organize a controlled experiment, and design

    useful worksheets for recording the data collected. I learned a lot more about

    spreadsheet programs and how to use them to analyze and present the data

    collected. I also learned some basics about statistics and how they can be used to

    assess the quality of the testing performed.

    My multiple rotor windmill design seems to be very efficient and worthwhile

    pursuing. I may continue to explore additional facets of this approach in futureprojects.

    Sources of Error

    The experiment was designed to keep sources of error to a minimum but not

    every aspect could be perfectly controlled.

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    1. Although the same three speed fan was used for all tests, the wind speed

    measurements at each speed were not exactly the same. However, the wind speed

    data at each speed was analyzed using statistics and there did not appear to be a

    significant variation.

    2. Some of the rotor variations would start the motor turning, but would not

    allow it to run continuously. It was impossible in these cases to get consistent

    readings of RPM, mAmps and mVolts. In these cases, that rotor variable was

    assigned a RPM of zero.

    3. The wind speed, RPM, mAmp and mVolt measurements could not be done

    simultaneously. The anemometer was held between the fan cage and rotor and

    the position interfered with the wind flow to the rotor, meaning that RPM,

    mAmp and mVolt measurements would not be valid.

    4. The anemometer had a stated accuracy of +/- 3 % or +/- 0.1 m/s.

    5. The tachometer had a stated accuracy of +/- 0.05 %.

    6. The multimeter had a stated DC voltage accuracy of +/- 0.5 % and stated

    Amps accuracy of 1.2 %.

    Applications & CostEffectiveness

    Opposition to the production of electricity from fossil fuels is rising and the

    earth's non-renewable resources are depleting. In 2001, Ontario's five coal fired

    power plants were responsible for 20% of all greenhouse gases released in the

    province, 23% of all sulphur dioxide emissions, 14% of nitrogen emissions and

    23% of mercury emissions. These plants are scheduled for closure by 2007.

    Wind power offers a pollution free, electricity-generating alternative, using a

    renewable energy source. The cost of wind generated electricity is declining, in

    comparison with other energy sources.

    This research could impact on the construction of wind turbines. Increased

    torque may permit increased turbine size and produce more electricity than that

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    of a single rotor wind turbine. The use of multiple rotors to increase torque could

    result in lower construction costs because rotor blades would be smaller, fewer

    support towers would be required and the overall efficiency of wind turbines

    would increase.

    My research could lower the cost of producing wind energy and have the added

    environmental appeal of requiring fewer wind towers. Less land would be

    utilized, less habitat destroyed and this could lessen some of the opposition to the

    construction of wind farms.

    Wind energy is the fastest growing source of energy worldwide. I believe that it

    will become more popular in North America due to the Kyoto Protocol and

    concerns about greenhouse gas emissions.

    Cost Effectiveness:A 50 meter rotor windturbine costs approximately 2 million dollars.Construction costs include tower construction (20 %) and rotor cost (20 %). The

    cost of turbine components, foundation and maintenance does not rise in

    proportion to size.

    Although cost information is difficult to obtain for proprietary reasons, I

    estimate that a multiple rotor design, with smaller, lighter and less expensive

    rotors, would exceed the performance of a conventional turbine, at a competitive

    cost.

    Cost comparisons between traditional and green sources of power do not include

    medical expenses. The Ontario Medical Association estimates that air pollution

    costs Ontario more than $10 billion per year in health care costs, lost work time

    and other measurable expenses. The time for investment in alternative sources of

    energy is now!

    Glossary of Terms

    Airfoil - A structure around which air flows creating lift.

    Amps - The number of electrons flowing past in a second; similar to litres per

    second in a water pipeline; defines electrical current in a wire

    Anemometer - An instrument for measuring wind velocity.

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    Bearing - A device that supports, guides, and reduces the friction of motion

    between fixed and moving machine parts.

    Bernoulli's Principle - States that increased air velocity produces decreased

    pressure.

    Betz' Law - A mathematical proof that states only 59% of the kinetic energy

    from the wind can be converted into mechanical energy by a wind turbine with a

    disc-like rotor.

    Blade Swept Area -The circular area that the rotor blades pass over.

    Blade Tip Velocity -The speed in meters/second of the tip of the rotor blade.

    Coefficient of Variation - A mathematical calculation (standard deviation x 100

    /mean) that provides information that can be used to compare different sets of

    data.

    Greenhouse Gases - Greenhouse gases are produced primarily through the

    burning of fossil fuels (coal, oil and gas) to produce heat, electricity and

    transportation. These gases trap the heat of the sun and cause global warming.

    Green house gases are carbon dioxide, nitrous oxide and sulphur dioxide.

    Kyoto Protocol - An international agreement on climate change that calls for

    reductions in carbon emissions from industrialized countries by the year 2008 -2012.

    Multimeter - An instrument designed to measure AC/DC voltage, batteries, DC

    current, resistance, diodes and continuity.

    Standard Deviation - A mathematical calculation used on a set of data to assess

    the amount of scatter or dispersion from the mean, or average. It is an indication

    of accuracy.

    Tachometer - An instrument for measuring revolutions per minute.

    Tip Speed Ratio - The blade tip velocity divided by the wind speed. The tip speed

    ratio is how much faster, than the windspeed, the blade tips travel.

    Torque - The strength of rotational force usually measured in Newton-Meters.

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    Volts - The electrical force or pressure behind the electrons in a circuit; similar

    to water pressure in a pipe line

    Watts - The total amount of electrical energy per second equal to Amps x Watts

    Acknowledgements

    This project could not have been completed without the assistance of my father,

    who helped me design and build the test unit and my mother who proofread the

    notebook and helped me understand basic statistical analysis.

    BibliographyDennis, L. (1976). Catch the wind: A book of windmills and windpower. New York:Four Winds Press.Gibson, D, (2002), Wind power. North Mankato, Minnesota: Smart Apple Media.Torrey, V. (1976). Wind-catchers: American windmills of yesterday and tomorrow.Brattleboro, Vermont: The Stephen Greene Press. Hamburg, M. (1987).Statistical Analysis forDecision Making. Chicago: Harcourt Brace JovanovichPublishershttp://electronics.howstuffworks.com/motor.htm/printablehttp://www.speakerfactory.net/wind.htmhttp://www.simetric.co.uk/si_watts.htmhttp://oge.apogee.net/pd/dfre.htmhttp://www.energy.iastate.edu/WindManual/Text-Systems.htmlhttp://www.energy.iastate.edu/WindManual/Text-power.htmlhttp://rredc.nrel.gov/wind/pubs/atlas/chp1.htmlhttp://www.eren.doe.gov/RE/wind_basics.htmlhttp://www.windpower.org/tour/wres/enerwind.htmhttp://www.windpower.org/tour/wres/tube.htmhttp://www.windpower.org/tour/wres/windspeed.htmhttp://www.windpower.org/tour/wres/varuab.htmhttp://www.windpower.org/tour/wres/windsprac.htmhttp://www.windpower.org/tour/wres/siting.htmhttp://windpower.dk/tour/wtrb/rotor.htmhttp://www.windpower.org/tour/wtrb/lift.htmhttp://www.windpower.org/tour/wtrb/aerodyn2.htm

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    http://www.windpower.org/tour/wtrb/size.htmhttp://www.windpower.dk/tour/design/index.htmhttp://www.windpower.org/tour/wtrb/powtrain.htmhttp://www.windpower.org/tour/wtrb/powerreg.htmhttp://www.windpower.org/tour/wtrb/electric.htm

    http://www.windpower.dk/tour/wtrb/tower.htmhttp://www.eren.doc.gov/wind/feature.htmlhttp://www.windpower.dk/tour/design/updown.htmhttp://www.windpower.dk/tour/design/concepts.htmhttp://www.windpower.dk/tour/design/optim.htmhttp://www.windpower.dk/tour/design/horver.htmhttp://www.windpower.org/tour/wtrb/comp/right.htmhttp://www.windpower.dk/tour/wres/park.htmhttp://www.windpower.dk/tour/wres/wake.htmhttp://www.windpower.dk/tour/wres/betz.htmhttp://www.opet.net.cn/enery/wind/science/basic.htmhttp://www.iclei.org/efacts/wind.htmhttp://www.technologyreview.com/articles/print_version/fairley0702.asphttp://www.windpower.org/tour/wres/index.htmhttp://www.science.org.au/nova/037/037key.htmhttp://www.lookout2000.com/windpower/http://www.energyadvocate.com/fw90.htmhttp://www.otherpower.com/otherpo