DURAMILL

Engineering Fundamentals 152

Final Project Report

Section A1, Team 3

Bryan Allen

Kirstin Childrey

Tim Stephens

Robert Wise

November 4, 2008

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Overview

For this project, our team of engineers was charged with the task of designing and

constructing a windmill that could generate electricity. The given restrictions for the

design and construction process were for the device to be original, fit within the size

specifications of 2 cubic meters, function without interaction once started, and work with

a budget of only $40. The use of readily available materials was strongly advised and we

had a time frame of approximately one month to complete all project requirements,

mostly outside of class time. We were also encouraged to choose a design that would not

take a long time to build.

Design Process

The initial steps in creating our device design involved establishing what kind of

generator the device would utilize. To better understand how a generator works, a hand

crank flashlight was “dissected” for research. This experiment exemplified how a

generator could easily be assembled using coiled copper wire and a powerful magnet.

Though the flashlight’s generator also involved gears, in the essential concept, turning the

handle would spin a coil of wire within a large cylindrical magnet creating enough

electrical current to power the light. Our initial plan

was modeled after this design; however, we soon

moved to a more practical design where magnets

spin within a larger continuous coil of copper wire.

Once we acquired the magnets we would use, we decided to spread them out over a small

piece of cardboard rather than using them in the column form that was in our original

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design. This reduced the mass moment of inertia of the magnets by having them more

spread out, allowing a quicker start-up to the rotation and more ease of movement.

It was also decided fairly early in our design process that the generator and

windmill would be closely connected, namely by a lightweight aluminum rod with the

blades of the windmill on one end and the magnets on the other. The idea of using gears

to increase the rotation of the magnets was also briefly entertained; however, we were

afraid this might create too much resistance to allow the blades to still spin freely so this

idea was discarded.

In brainstorming, our design plans

consistently incorporated a lateral orientation

for the generator. However, this layout soon

presented the challenge of finding a way to

support the windmill without much resistance

to its rotation. This was finally solved with the

addition of a cork insert and a series of washers to reduce friction. The next design

obstacle involved the blades of the windmill, for which we had countless suggestions. For

several weeks, we worked under the concept of having a central joint connecting

individual blades. We researched and tested several possible materials and structures for

the blades including soda cans, stretched fabric wings,

and plastic. Unsatisfied with any of these options, we

returned to brainstorming and found a new idea for the

windmill, a pinwheel in place of individual blades.

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Final Product

We named our final product DuraMill. The total construction time for the device

was approximately 4 hours, with the most time-consuming tasks involving coiling the

wire and stripping the ends, and cutting the wood components to size and connecting

them as necessary. All team members participated in the construction of the windmill and

generator components, and much teamwork was required in finding our raw materials

and building the device. Our final design was somewhat similar to

our original ideas, but with some sizeable changes such as the

blade structure and magnet orientation.

We used a pinwheel for the blades of our windmill in our

final design, made of rigid, but lightweight cardboard. This new design eliminated the

need for a central joint, and ensured that the blades would all be sturdy, since the entire

blade system was one piece. It was easily connected to the opposite end of the aluminum

rod and washers between the back of the pinwheel and the wood base reduced any local

friction.

Efficiency Analysis

Power=0.5 XrhoXareaXvelocity^3

Where:

Rho is the density of air (approximately 1.225 kg/m3)

Area is the area swept by the rotor (blades){ pi Xradius^2 }radius

approximately 0.14 meters

Velocity is the velocity of the air( approximately 1.7 meters/second)

Power=0.5X1.225X(piX.14^2)X1.7^3=0.185 Watts

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Actual Power= .001 Watts

Efficiency=Actual Power/Power=(0.001/0.185)x100=0.54 efficient

Bill of Materials

Many of the materials used in our final project were items team members already had, or

were acquired at no cost from other sources. The prices for these components are

approximate, roughly calculated based on an average value for these items and the

amount of each material present in the final device.

Materials Used: Cost: Magnets $ 13.99 Copper Wire 10.99 Wood (estimated) 4.00 Electrical Tape 2.99 Cardboard (estimated) 2.00 Cork 0.99 Aluminum Rod 1.50 L-Brackets 1.99 Washers (estimated) 1.00 $ 39.45 Our budget restriction for this project was $40. As shown in the bill of materials, we were

able to stay within this limitation when building our device. To do this, we had to try to

use materials that we already had or that were inexpensive and easy to find. This required

much creativity and ingenuity in the device design from our team. While our team’s

device efficiency was limited by this budget, a much more efficient generator could be

built with more expensive and higher quality materials.

Conclusions

During the in-class testing, our generator produced approximately 1 watt of power

while the windmill was in operation. We found our device was not very efficient,

however we believe it performed well for the budget and time restrictions we were given.

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One change we would have made to our device to improve our efficiency would be to use

more copper wiring in the coil to increase our power production, as well as coiling the

wire tighter around the magnets. Also, by increasing the surface area of the pinwheel, our

windmill could catch more of the air flow from the fan and spin faster, though we would

increased drag would also have to be taken into account.

Our knowledge of generators coming into this project was virtually nonexistent,

so we had a lot to learn about the flow of electricity and how the different components of

a generator work together as a system before we could even being to draw up our original

designs. Our building process consisted largely of a system of trial and error, making

small changes, observing any potential improvements, and adjusting accordingly.

In this project, we learned about working on a deadline and with a team of busy

schedules to coordinate and finish tasks. We gained experience working with a group and

brainstorming, planning, and executing our ideas. Input and discussion from all members

was integral in achieving each aspect of our objective. This dynamic is a good indication

of what we will see when we begin working as engineers. Most importantly however, this

project exemplified how engineering can be fun!

References

Tim’s flashlight