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Bicycle Power Generator Design for DC House:

Off Grid Energy Solutions

Presented by:

Brandon Hayes

Louis Goguely

Electrical Engineering Department

California Polytechnic State University

San Luis Obispo

2011

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Table of Contents: Table of contents ...........................................................................................................................................2

List of Tables/Figures ....................................................................................................................................3

Acknowledgements .......................................................................................................................................4

Abstract .........................................................................................................................................................5

1. Introduction ...........................................................................................................................................6

2. Background ...........................................................................................................................................9

3. Requirements .......................................................................................................................................11

4. Project Methods ...................................................................................................................................14

5. Design ..................................................................................................................................................16

Bike .........................................................................................................................................................16

Design of Stand .......................................................................................................................................18

Motor .......................................................................................................................................................26

Alternator.................................................................................................................................................28

DC Permenant Magnet ............................................................................................................................32

Mounting & Wiring .................................................................................................................................35

6. Integration and Cost ............................................................................................................................40

7. Tests and Planning ...............................................................................................................................43

8. Conclusion ...........................................................................................................................................48

Bibliography ................................................................................................................................................50

Appendices ..................................................................................................................................................51

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List of Tables & Figures:

Tables

Table 5.1: Bill of Materials for Bike Stand.…………………………………….………………………….19

Table 6.1: Estimated and Actual Costs of Project.……………………........................................................41

Table 7.1: Output Current based on RPM for Ford 3G Alternator……………..…………………………..45

Figures

Figure 1.1: Energy Consumption Projections………………………………..……………………………...7

Figure 1.2: Energy Consumption Projections by Non-OECD economies…..………………………………7

Figure 3.1: Block Diagram of Overall Project Design…………..………………………………………….11

Figure 5.1: 3 pieces of 2‖x4‖x8’, 1 piece of 2‖x3‖x8’………….…………………………………....…….20

Figure 5.2: Mid-Peg to Mid-Peg Distance Defined………….……………………………………………..21

Figure 5.3: Visual of the Bike Stand Base……………….…………………………………………………21

Figure 5.4: Vertical Beam Placement on the Bike Stand Base….………………………..………………..22

Figure 5.5: Completed Back Half of the Bike Stand……………………………………………………….23

Figure 5.6: Front Tire Holder……………………………………………………….………………………24

Figure 5.7: Final Bike Stand Design with Bike and Alternator in Place……………….…………………..24

Figure 5.8: Output Current vs RPM for Ford 3G alternators...……………………….……………………29

Figure 5.9: Display of the Field Producing Parts, Stator, and Rotor…………………….…………………30

Figure 5.10: Diagram of rotor assembly in alternators…………………………………………………….30

Figure 5.11: Output Voltage vs. RPM of DC Motor....…………………………………………………….33

Figure 5.12a: Wiring of an Alternator...……………………………………………………………………34

Figure 5.12b: Wiring of an Alternator……………………………………………………………………..34

Figure 5.13: Mounting Alternator to Stand Figure…………………………………………………….…..36

Figure 5.14: Pulley Connection Between Alternator and Rim...…………………………………………..36

Figure 5.15: Battery Charging System Wiring…………………………………………………………….37

Figure 7.1: Alternator Bench Setup.……………………………………………………………………….43

Figure 7.2: Voltage Output based on RPM of Ford 3G alternator…………………………………………45

Figure 7.3: Current Output vs RPM………………………………………………………………………..46

Figure 7.4: Output Power vs RPM...……………………………………………………………………….46

Figure 7.5: Efficiency of alternator vs RPM……………………………………………………………….47

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Acknowledgments:

Special thanks to the following individuals or organizations for their contributions and

support:

-Professor Taufik

-Achievement House

-Howard Siewert

-Virgil from the BRAE shop

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Abstract: Our goal for this project is to design and implement a bicycle power generator for

the DC House Project. The DC House Project is an initiative to bring safe and reliable

power to the billions of people around the world without electricity. This goal will be

accomplished by designing a safe and sturdy human powered stationary bicycle that

produces DC energy. The DC power generated can be stored via batteries and used by the

local population to use for lights and other utilities that many take for granted on a daily

basis. Bicycle Power Generators are not a new idea, with many created by hobbyist for

residential use with small scale energy in mind, to charge batteries in case of a power

outage or natural disaster. We are looking to expand upon these designs and build a DC

generator that will convert human power into electrical power. The objective is to build a

device that is safer and more power efficient. If our product design were to be built and

shipped to people across the globe, it would be imperative that it meets all the safety

specifications that any national commercial product entails.

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I. Introduction:

In today’s modern society, most people just flip a switch or push a button, and

everything we depend on is readily available. Cell phones, computers, televisions, heated

water, lights, and so much more, are all the backbone of any modern society’s

functionality. The electricity powering all these systems is something most people rarely

think about until the power is no longer available for use. The extensive system that

allows for an instant and near constant supply of conditioned power is referred to as the

―grid‖. This grid is usually supported by government and/or private in developed

countries; a government must have enough financial resources to establish and support a

significant investment to provide the service of electricity. With this idea in mind, it may

be hard to believe that nearly 80% of all people living in third world countries have no

access to electricity. That is an estimated 1.5 Billion people with no electricity[7].

This power crisis will not be getting better in the future. The U.S. Energy

Information Administration stated in their International Energy Outlook Report for 2010

that the world energy consumption will increase by 49 percent, or 1.4 percent per year,

from 495 quadrillion Btu in 2007 to 739 quadrillion Btu by 2035, as shown in Figure 1.1.

The Organization for Economic Co-operation and Development, OECD for short, is an

international organization, which includes a majority of the world’s most advanced

countries. Historically, OECD member countries have accounted for the largest share of

current world energy consumption; however, in 2007—for the first time—energy use

among non-OECD nations exceeded that among OECD nations as depicted in Figure 1.2.

If any growth in the world’s energy supply and infrastructure is to occur in the future, it is

likely the majority of this energy will go to these developed countries before any

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developing or third world country. This will only exasperate the needs and deficiency of

these developing and third world countries.

Figure 1.1: Energy Consumption Projections[1] Figure 1.2: Energy Consumption Projections by

Non-OECD economies[1]

As of today, oil is by far the most used energy product in the world’s energy

supply, with coal at a distant second. According to the International Energy Agency, oil

products make up over 33% of the world’s energy supply, while coal products make up

around 27% of the world’s energy supply.[1] The Middle East and Russia are the top

producers of oil in the world, and based on their current trends, will be hitting peak oil

production within the next decade.[2] This means the energy demand will continue to

increase but the oil supply will not be able to follow the same trend. To make matters

worse, the cost of oil worldwide has skyrocketed due to the combination of issues such as

the crisises in the Middle East, off shore drilling accidents, and the increasing difficultly

for finding and drilling for oil. While coal is still an option for fossil fuels the

environmental impact is arguably worse than oil. Per unit of energy, coal is even worse

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for the environment than oil. The amount of CO2 produced is nearly the same, but coal

produces much more solid, liquid, and gaseous waste products. The trend of rising energy

needs and waning fossil fuel supplies means a new forms of energy needs to fill in the

gaps.

As the electrical grids get older in developed countries, and the cost and demand

for energy gets higher worldwide, it is likely the people who are left out are the ones in

developing and third world countries. Grids are a large expense, even for the wealthiest

countries, and the amount of transmission losses in large grid would only compound the

energy crisis. So a grid of energy for less fortunate countries is out of the question.

Without the grid to support these people, a standalone system is the only solution.

There is only one way to create a standalone system, and this is with a generator.

The type of generator to select is our main concern. The typical solution is to use a fossil

fueled generator that produces AC or DC energy from fossil fuels. This solution is less

than ideal as fossil fueled generators are bulky and expensive, plus the ever-rising costs

of fossil fuels and the negative impacts on the environment due to emissions.

Additionally, more regulations regarding emissions are starting to limit the burning of

harsher fuel. Clean energy technology development has increased to combat the cost of

rising fuel costs and provide an alternative to fossil fuel. This alternative is to use more

sustainable means of power generation. These means include solar, wind, water, and

human powered generators that produce clean energy. Not only would the energy be

clean and sustainable, but we have only begun to scratch the surface of the amount of

energy production possible with renewable energy. This is the option Cal Poly’s DC

House Project looks to develop.

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II. Background:

The DC House Project is a Cal Poly initiative, led by Professor Taufik, to help the

energy crisis in third world and developing countries. The DC House is simply a house

that runs completely off of sustainably produced DC power, and is completely

independent of the grid, as many of the users would have no access of the grid. The DC

House is currently in the first phase of development, with many students working on

viable ways of producing DC energy, which include: wind generated power, hydro-

electric power, solar power, and human generated power[7]. This project focuses on the

development of human generated power as a standalone DC generating stationary

bicycle. While this DC House Project is being used to provide cheap and clean energy to

the users in third world and developing countries, this is also an opportunity to design and

implement clean sustainable house designs that could become feasible for modern

countries in the future to future help solve the energy gap worldwide. The DC House

Project is intended to be an open source project, with future help from developing

countries and interested individuals. The main portal is available at

http://www.calpoly.edu/~taufik/dchouse/index.html.

The applications for the DC House would be simple in the initial phases. The

house would supply energy for simple appliances like light bulbs for rooms, fans, and

small pumps for running water from wells. These objectives may seem mundane, but for

the inhabitants, it is the first step towards enjoying the luxuries we take for granted every

day. The ultimate goal for the DC House would be to produce the most efficient

generators with the highs energy output, in order to run even more appliances such as

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stoves, refrigerators, and coolers. This would give less fortunate people many of the

comforts we enjoy while being completely energy independent and self-sustainable.

As it was pointed out earlier, a DC approach makes much more sense than a

standard AC transmission approach. While grid infrastructures exist in developing

countries, many of the people do not have access to it because of a lack of funds or living

in a remote location or both. The money required to bring the grid to these people is not

reasonable, so localized DC generation is the best choice. The localized DC generators

means no extensive transmission is required, which will cut down power losses.

This project focuses on a human powered bicycle generation. We will design a

simple and efficient bike stand to integrate with the rest of the DC House generation

projects. Most likely the bike will be connected to a motor that generates energy to be

used directly or stored in batteries for later use. While solar, wind, and water generated

energy are also sustainable, our human powered energy has a few unique properties

related. The first is that human power is the only truly independent form of power

generation. Wind, water, and solar energy are all at the will of nature; however, our

system will always be available to produce energy if an able body is around. This on-

demand energy will always be available to provide energy for an item in an emergency

situation, if all the other generators fail to provide energy. Another great aspect of the

human powered generator is the awareness it could instill in the users, as they will be

able to observe and appreciate the energy they are making for themselves. This could

help create a future of energy conscious individuals in developing countries as opposed to

the energy wasting that has been created in other developed countries.

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III. Requirements:

A simple block diagram of the overall project design is shown in Figure 3.1.

Figure 3.1: Block Diagram of Overall Project Design

The project’s main goal is simply to charge a battery array with a produced 24VDC from

the bicycle design; however, for this project design to be considered successful, a list of

primary and secondary objectives has been determined.

Primary objectives include:

Low Production Cost

High Safety

Secondary objectives include:

High Energy Efficiency

Low Upkeep

High Product Durability

The first two major objectives were identified for their obvious necessities. With

the majority of people without energy being at or below the poverty line, and with

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minimal expected financing and donation, it is imperative that the product design be at its

absolute minimum cost to any users. We researched other available bicycle generators,

and all of them are much too expensive to be produced for the DC House, with some

costing nearly $1000. These systems are built with expensive steel stand, DC motors, and

regulators. Our system will look to use more common items such as wood for the stand,

and reused motors from other products. These items will be engineered to afford the most

power output for the least amount of money.

Safety is another major factor, because the safety of the consumers, no matter who or

where, is always of the utmost importance. The DC House is to help improve the life of

the users, so we do not want them being injured from our product. For the aspects of

safety, nothing will be overlooked and the product will be held to standards equivalent to

any national electrical product. These include following mandates:

Conform to the National Electrical Code (NEC)

Conform to IEEE code 1547

These regulations required the obvious safety precautions. These precautions include no

exposed wires or components in order to prevent electrocution, and rated electrical

equipment to protect the system and users for electrical shorts and overloads.

Once these two objectives have been sufficiently met, the focus can be turned to the

secondary objectives. A product with high efficiency will guarantee the maximum

usefulness for the inhabitants of the DC House. We want our bicycle generator to be able

to power the most utilities for the longest possible time. For this objective, we

constructed multiple designs to verify the most efficient setup. These various designs are

explained in the design section. All designs are tested and their results are compared in

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the design section as well. Tests include comparing produced kilowatts per hour versus

the bicycle wheel’s revolutions per minute and produced volts DC Output versus the

loaded output resistances, etc. for the various designs.

The idea of low upkeep and high durability coincided with the factor of cost. Just as it

must be low cost for the affordability of the DC House, the product must last for a long

period of time, as the inhabitants may not be able to afford the necessary equipment or

labor to maintain or fix the product if something should fail. We hope to do this by

keeping the components of the product simple and commonly available. This includes a

standard, stand-alone bicycle, a simply constructed bicycle stand, and standard electrical

components for any energy conversation. Secondary components such as DC-DC

converters could add more cost and complexity, but should be designed as purely

optional. If all of these objectives can be met, we can consider the Bicycle Powered

Generator Design to be a success and usable for any consumers.

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IV. Project Methods:

This project has various different design paths to complete our product while

meeting the majority objectives. This means we will have to implement and compare our

different designs to insure the best product based on our set of objectives. These paths

have changed as we progressed through our project, and there were a few foreseen

methods that we expand upon in the design section.

The basic design for the bicycle powered generator is to have a bicycle on a fixed

stand, and then when the bicycle is pedaled, the spinning motion of the rear tire is used to

produce mechanical energy directly into a DC voltage. If an AC voltage is produced, a

full bridge rectifier will be necessary to produce the DC voltage. This DC voltage can

then be used immediately or stored via a battery array. If a constant DC voltage is

required by the user a DC-DC converter may be necessary to change the varying DC

voltages produced from the varying bike speed to a constant DC voltage for certain

utilities or battery array. The first decision is selecting a bill of materials for each design

path. This will help determine the ultimate product affordability. We must decide whether

to use an alternator or dynamo to convert the bicycles mechanical energy to AC or DC,

respectively. While an alternator is easier to find and purchase with many functioning

units available in scrap yards, they also tend to be less efficient in the output of DC power

compared to a dynamo. Another design factor that must be implemented and compared is

the coupling of the bicycle wheel to either the alternator or dynamo rotor. One option is

to use two contacting wheels to connect the two components. This option is a bit simpler

to implement and take very little upkeep to maintain; however, the efficiency of the

contact is relatively low due to slippage losses and frictional losses. A more efficient yet

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expensive design would be to have the wheel and the alternator/dynamo be connected via

a rotary belt, similar to a car belt system. There are bound to be various other obstacles

and design methods to be implemented as the project progresses, and will be observed

and recorded as they occur.

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V. Design:

The Bike:

A bicycle is designed to convert human energy into mechanical energy for

transportation purposes. The mechanical energy is then translated into electrical energy

through the use of a drivetrain turning a motor. To maximize the efficiency of both

conversions is essential to obtaining the maximum power output. The first conversion is

from human energy or muscle energy into mechanical energy. The bicycle is an efficient

and robust method to convert between the two types of energy. It is an efficient design

that provides seating for the user as well as pedals and drive train that are easily

activated. There are few moving parts and the simplicity of design is proven. Alan Cote

wrote in Bicycling Magazine in 2005, that most of the forces acting again a rider are due

to off bike force such as wind, gravity, and rolling resistance. He explains, ―Together,

these three off-bike forces make up about 95 percent of the force against you, which

means the bike itself is about 95 percent efficient‖ [8]. The bicycle is one of the most

efficient uses of the human body’s existing musculature and the ergonomic position

allows for nearly everyone to utilize. As published in the International Journal of

Industrial Ergonomics, ―Pedaling is the most efficient way of utilizing power from

human muscles. Pedal power enables a person to drive devices at the same or higher rate

as that achieved by hand cranking, but with far less effort and fatigue‖ [11]. The human

musculature is concentrated in our legs and the bicycle set-up allows for harnessing the

maximum output. The article also explains that stationary power generation on bicycles

has been skipped over in past research but with the rising cost of other power generation,

reliance on human power generation will become more important; furthermore, the

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bicycle is a universal symbol of transportation in all types of countries especially

developing ones. We can find bicycles everywhere and the robustness of the simple

mechanical system makes the learning curve essentially zero.

The rotational nature of the bicycle drive train or more specifically the pedals is a steady

style of movement. The constant driving of the pedals become more constant when

reaching the drivetrain since there is rotational inertia to smooth out any subtle changes in

the speed. The rear wheel therefore becomes an ideal prime mover for electrical

generation; we would need to connect an alternator and rear wheel though either direct

contact or a belt system. Modern bikes have gears that can adjust the range of RPMs and

makes initial pedaling easier. The user is able to start softly and increase the resistance as

momentum is gained. The user can also adjust the speed and perceived resistance to their

comfort levels. When the bicycle stabilizes and gains more speed, then the user ―down-

shift‖ thereby increasing perceived resistance and outputs more power. The same

approach can be used by the user of our stationary power generation set-up. This factor

comes into play further when developing the motor for the bicycle design.

In developing countries, people use bicycles more often than motor vehicles. The

idea of electricity generation through stationary bicycling has been introduced in select

area, but more as recreation focus in the United States. An elementary school in New

Jersey uses a pedal-a-watt system that requires children in gym class to pedal for at least

five minutes. These stationary bicycles generate electricity to power the gym’s sound

system as well as charge batteries in the school’s laptop computers[10].

While a bike is the ideal tool to harness human power, there are a few difficulties

when trying to use a bicycle. A bicycle is only stable when in movement; it will fall over

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if not moving forward or braced. A stand or brace has to be built in order to remain

stationary when trying to generate power. This bracing, if done haphazardly, could result

in injury to the user or the bicycle. These injuries would not be more catastrophic than

crashing on a traditional bicycle.

A bicycle is not design to be braced easily. It is a streamlined structure that is not

readily drilled, glued, or clamped down upon. Modern materials are making bike lighter,

but less suited for being braced or placed on a stand for example carbon fiber or

aluminum alloys. These materials are not meant to be stressed in all directions; a brace

often adds shear or torsion stress which may damage the bicycle’s frame.

There is limited adjustability for different sizes of users. The position of a single

frame of a bike does not allow for all of the population to be accommodated. The seat

post adjustment only accounts for one dimension of accommodation and there needs to

be more dimensions. Standard bicycle frames also come in various sizes thus indicating

lack of accommodation for all of the population.

Bike Stand:

The first step in designing a bicycle generator is building the stand for the bicycle.

A bicycle being an important transportation device, we tried to design a stand that would

not damage the original intention of the bicycle. Our stand’s design could not render the

bicycle useless for traditional transportation. A permanent attachment to the stand would

also void transportation. Welding and other permanent methods were thus eliminated

from design choices. For the stand, we opted to construct it using wood, instead of buying

or constructing a stand from metal. This was an easy choice to make as wood is much

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cheaper than steel in most locations around the world. The negative aspect of a wood

frame is the issues of breakability and corrosion from the user or the environment or both.

These factors can be reduced with a proper stand design and protective coatings. For the

stand to be able to handle the vertical and lateral motions of the users, a wide and solid

base is necessary. The bike to be mounted on the frame is intended to have pegs on the

back wheel. If the bike does not have pegs, a pair can be found or purchased for less than

$10. The bill of materials for the wood stand we designed is listed in Table 1:

Table 5.1: Bill of Materials for Bike Stand

Item Cost Per Unit Quantity Total

2"x4"x8' wooden beam $2.39 4 $9.56

2"x3"x8' wooden beam $1.87 1 $1.87

Rigid Tie $1.15 2 $2.30

Angle Tie $0.43 12 $5.16

Box of Wood Screws N/A N/A $4.00

Long Bolts N/A N/A $3.00

Total

$25.89

The tools we used for a more precise stand were a table saw, an angular saw, a

drill press, and a power screwdriver; however, a simple handsaw and hand drill would

suffice to build the stand. To assist with the building of the stand, visual sketch ups were

designed with Google SketchUp. Figure 5.1 shows the four 8’ pieces of wood used for

the frame.

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Figure 5.1: 3 pieces of 2‖x4‖x8’, 1 piece of 2‖x3‖x8’

In order to build a stand with acceptable stability, a wide and strong base must be

constructed for the design. Two of the four 2x4 wooden beams are used for the base. One

beam is cut into two equal 4 foot pieces. The other wooden beam is cut twice. Once the

piece is cut into two 4’ sections, use one of the sections and cut it in half again to form

two 2’ sections. This gives us three 4’ sections, and two 2’ sections of wood. The two 2’

sections are laid down parallel to each other 4 feet apart, and one 4’ section is placed

parallel between the two pieces, with the piece about 1 foot away from the front 2’

section and 3 feet away from the back 2’ section. Then the two remaining 4’ sections are

laid on top of the three wooden boards perpendicularly across the two 2’ sections spaced

about the distance mid-peg to mid-peg of the bike to be mounted as depicted in Figure

5.2.

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Figure 5.2: Mid-Peg to Mid-Peg Distance Defined

These pieces of wood are fastened together with 6 angle ties at each connecting point,

giving a base with the form shown in Figure 5.3.

Figure 5.3: Visual of the Bike Stand Base

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Once the base is made, the vertical stands for holding the bike can be added to the

frame. These vertical pieces are two 2’ wooden sections cut from one of the remaining

2x4 wood beams. These two 2’ sections are mounted vertically over the cross section of

the two 4’ sections, and face each other, wide side out, perpendicularly. Two holes

slightly bigger than the peg’s diameter need to be drilled in the two wood sections, in

order to hold the bike in the stand. These holes need to be high enough to avoid the back

wheel from contacting the lower 4’ wooden section of the frame’s base. The two rigid

ties are used to connect the two vertical beams to the base of the frame. Figure 5.4

clarifies this layout.

Figure 5.4: Vertical beam placement on the bike stand base

Side stabilizers are imperative for the final frame design, as there is a great

amount of force put on the stand, from twisting and push-pull forces, when the user

pedals the bike. These side stabilizers are made from the remaining 2x4 wood. A 45°

angle needs to be cut at each end of the six stabilizing beams, to connect the stabilizers

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from the base to the vertical posts. The angle ties are used to connect the stabilizing

beams from the base to the vertical posts. Figure 5.5 depicts the final frame design

showing the locations of the six stabilizing beams, as well as the approximate locations of

the peg holes and angle ties.

Figure 5.5: Completed back half of the bike stand

The main frame for the bike stand is now complete; however, a front wheel holder

must be constructed to hold the front tire in place. This will keep the user from turning

the tire and possibly shifting too much weight to one side of the stand. The front tire

holder is much easier to construct. Simply cut the 2x3 wooden beam into two 2’ sections,

and two 1’ sections. Place the two 1’ sections parallel to one another approximately 2 feet

apart. Lay the two 2’ sections on top of the 1’ sections perpendicular to the 1’ sections

and parallel to one another. The space between the two 2’ sections should be just a bit

wider than the width of the bikes front tire, in order to hold it tightly in place. Angle ties

are used to connect the pieces of wood together as Figure 5.6 demonstrates.

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Figure 5.6: Front Tire Holder

Once the two sections of the bike stand are completed we can mount the bike and other

hardware such as a motor or alternator on the frame. A concept of the bike frame with a

bike is shown in Figure 5.7.

Figure 5.7: Final bike stand design with bike and alternator in place

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The bike stand frame design was made to withstand a great amount of force from

the user and still maintain its performance and form. This is necessary in the bike to

allow the user to pedal much faster if more energy is required in a shorter amount of time.

While the stand does not have the strength of a steel stand, we believe the stand is more

than adequately meets the strain requirements from a user of average weight and size.

Another factor that needs to be addressed is the issue of corrosion. This bike is

intended to be used by people in developing and third world countries, so it is safe to

assume the entire system will be outside in the elements for the majority of its working

lifetime. Wood corrodes when left unprotected in the environment for an extended period

of time; however, there are many protective coatings for wood on the market that are

reasonably priced. A coat of lacquer and fresh paint should be more than enough to help

significantly increase the lifetime of the stand for outdoor use. If cost is too much of a

factor, the stand should still hold up quite well in an exposed environment if it is kept out

of direct contact with rain, water and other liquids.

While we believe our stand has high durability and stability for its given cost,

there are more than likely many improvements that can be made to the stand in order to

improve its quality to cost ratio. This would require extensive testing in a controlled

environment as well as extensive testing in an exposed environment; however, the scope

and limited time of our project did not permit us this opportunity. We do hope that

students in the future phases of the DC House project will look to improve upon our

current bike stand design.

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Motor:

With a solid stand in place, a motor must be selected in order to create the DC

power to supply the DC House’s battery array. There are many options for the motor set

up for the system. These include a DC motor, a Generator, and an Alternator. We will

look to connect the spinning back wheel directly to the axel of motor’s rotor. The two

options are to either have direct contact between the back wheel and motor axel or to

have a belt connect the two elements. It was decided early on to use a belt to connect the

two elements together. While a belt adds more complexity to the set up and makes the

bike more difficult to remove from the stand, it gives much more grip between the wheel

and axel, reducing the slippage losses between the two parts. If a direct connection was

made the slippage losses could increase dramatically depending on how the user was

pedaling the bike and the external conditions at the time, such as the stand being in a wet

environment.

To connect the wheel to the motors axel, the bicycle tire and tube was removed. A

belt that fit nicely on the wheel rim was chosen and an axel head for the motor needed to

fit the belt as well. The next step was to determine the best motor to connect to the bike.

A simple DC motor was initially thought to be the best choice as the DC output of

the motor was the desired electrical output for the battery array. That meant components

would not need to be created or maintained to convert AC to DC and the losses from AC

to DC could also be avoided in the system. We searched for DC motors in common

household appliances such as vacuums and ceiling fans, but found no motors at the size

we wanted for the scale of the bicycle system. The sizes were too small and did not create

enough voltage or current to output a substantial amount of power. While looking into

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buying a DC motor at a decent size and rating, it was found that the cost for such a motor

would be too expensive, and finding such motors in third world and developing countries,

much less buying them, would be out of the question for the scope of cost for this project.

Another motor option was using a car generator to produce the output DC voltage

for our system. Car generators are parts found on older models of cars before the 1960’s.

They are similar to alternators, but produce DC voltage directly without a use of a

converter like an alternator. This seemed a valid choice as once again the losses from AC

to DC conversion could be avoid; therefore, improving the efficiency of the bicycle

system. We looked for a car generator from an old car in order to test the part; however, it

soon became obvious that the part is very difficult to locate. There are very few cars left

that use car generators as opposed to car alternators and the ones that still exist are

usually very expensive or hard to find. When looking for a car generator from Los

Angeles to as far north as Bakersfield, we found no working car generators. The few that

were located were rusted beyond the repair we could provide. This was unfortunate

because we were not able to compare a car alternator to a car generator. It may have been

in vein nevertheless, if it was that difficult to find a car generator in California where

supplies are very abundant, it could be even more difficult to locate internationally in

poorer areas. The cost of a car generator could also pose a problem as older car

generators tend to cost more due to their rarity and the components they utilize. Car

generators use a component called a commutator to rotate the motors fields, which makes

the generators more costly and heavier. Due to the increased expense and less availability

compared to alternators, the car generator was ruled out for the system design.

28

Alternator:

The last practical option to implement for the bicycle system was to use a

standard car alternator. This seems to be the most reasonable motor for the design, as car

alternators are widely available worldwide for relatively low costs when purchased as a

used part. Finding donated alternators would also be an easier task to reduce the projects

overall cost. There are some difficulties however with an alternator as opposed to other

motor options. The first issue is the power loss due to conversion from AC to DC voltage.

Most alternators automatically convert AC to DC in the regulator of the part; however,

there is still the power loss in the alternator that will reduce the efficiency of the product

and waste some of the energy exerted by the user. Another major issue when using an

alternator occurs at the speed at which the part is operated. When a car is idling, the rpm

of the motor can be seen in the odometer. This value is usually around 600-700 rmps.

Alternators usually run at a 3:1 rpm ratio due to the diameter difference in the motor and

alternator head. This means an alternator is more efficient at speeds of 2000 rpms and

higher[3]. We could never hope to achieve this speed even with a bike tire being

somewhere around a 10:1 ratio of the alternator’s head diameter. If a user was to pedal

around a reasonable 100 rpms the alternator would only be rotating around 1000 rpms;

which is around half the speed of an idling car. For our testing and bike design, we used a

Ford 3G alternator. This part is readily available as it was used in a majority of Ford’s

cars for over a decade. Figure 5.8 shows the current output on the various models of the

3G alternator based on the shaft’s RPM.

29

Figure 5.8: Output Current vs RPM for Ford 3G Alternators[3]

As you can see, no matter which model of the Ford 3G alternator used, the output

current does not begin to reach its maximum potential until around 3000-4000 rpms.

Even though it would be physically impossible, we would never want to run the

alternator as such speed as the output current would be much too high for the rated

equipment used for the design.

There is one possible method to increase the current output at lower RPMs. This

process would require either the stator or rotor wiring to be rewrapped. The rewrapping

of the stator or rotor would have to be with thinner gauge wire in order to increase the

number of turns.

30

Figure 5.9: Display of the field producing parts, stator and rotor[4]

From the Figure 5.9, you can see it is much easier to rewrap the rotor instead of

the stator. The stator is a complex number of wired loops set up in a particular order to

produce an electromotive force (EMF) when charged so the rotor can produce an

electrical output. The difficulty with rewrapping the rotor is trying to remove it from the

finger poles. A more detailed picture of the rotor structure is shown in Figure 5.10

Figure 5.10: Diagram of rotor assembly in alternators[13]

31

The finger poles on the rotor actually bend the magnetic field of the rotor around the shaft

in order to obtain the electromagnetic induction between the rotor and stator that produce

the electrical power. This process produces a voltage across a conductor moving through

a magnetic field. In this cause, the rotor moving through the stators magnetic field that

causes the alternating current.

Once the finger poles and shaft are removed, the coil of the rotor can be rewound

with thinner wire more times. From Farraday’s equation, , we find that as

N (number of turns) increases, ε (electromagnetic force) increases proportionally[12].

With the higher EMF, we produce more power from less rotor rotations. In other words,

with a rewrapped rotor we can produce more power with lower RPMs; however, this will

not give the alternator any more power efficiency, it will only shift the Output Current vs.

RPM curve shown in Figure 5.8 to the left. While more current will be produced at lower

RPMs this is because the EMF is much bigger, which in turn will give the users another

problem, the EMF-produced resistance. An EMF in a motor is not a problem until you

are the one actually supplying the rotation of the shaft. A higher EMF means the user will

experience a higher resistance in their pedaling. This ―inductance hump‖ of starting to

pedal will tire the user greatly if a full field is being produced by the stator. To resolve

this issue a few different ideas were implemented to reduce the pedaling resistance in the

alternator.

32

DC Permanent Magnet Motor:

The first idea for deciding how to mitigate the EMF issue was to attach a DC

motor into the belt system between the back tire of the bike and the alternator head to

produce a DC voltage to apply to the stator. An alternator will not produce any current

unless the stator has a sufficient voltage and current to induce the EMF required to

interact with the rotor. The greater the voltage on the stator, the greater the EMF and

resistance the user will encounter. If a large voltage was applied to the stator via a battery

or voltage supply, the EMF could be strong enough to keep some users from even starting

to pedal the bike, inhibiting them from producing any power. The DC motor hooked up

to the same belt as the alternator would be a good way to regulate the stators EMF

depending on the pedaling speed of the user. When the user is not pedaling, no DC

voltage is being produced or provided to the stator of the alternator. This means there will

be no EMF resisting the user from starting the bike. As the user begins to pedal more

rapidly the DC motor will begin to produce a strong voltage to charge the EMF of the

stator. This means the strength of the field and resulting power output of the alternator

would be completely depend on the strength and speed of the user. This would allow

smaller, less capable individuals to still produce some small amount of power from the

alternator opposed to none, and stronger individuals would be able to avoid the initial

EMF field and build pedaling momentum to charge the EMF of the stator to its maximum

strength and allow for a higher amount of power output from the alternator for a longer

amount of time. We received a small DC motor from a previous power generating bike

stand to try implementing the process on our design. In order for the DC motor to be

viable for our system, the motor would have to supply enough voltage to the stator in

33

order to start the charging of the alternator. The DC motor was tested individually in a

motors lab to determine the output power of the part. The motor was connected to an

induction motor that was controlled by a Variable Frequency Drive. With this VFD, the

DC motor was tested at various RPMs to determine the output current and voltage. We

would want a maximum voltage of around 12V and a maximum current around 1A to

charge the stator and produce a strong EMF for the alternator. Once the motor data was

collected, it was clear that the DC motor we were using would not provide a strong

enough DC voltage to stator to induce the EMF at the operating RPMs of our system.

Basically, the user would have to pedal so quickly to induce the EMF of the alternator

from the DC motor, that the use of the motor to power the stator field is unreasonable.

Figure 5.11: Output Voltage vs. RPM of DC Motor

The method of using a DC motor as a field generator on the design is still

feasible; however, it would take a bigger and more expensive DC permanent magnet

motor to implement, and the main goal of this project is to keep the costs as low as

34

possible. So we determined the improvement of negating some issues of the EMF in the

alternator was not worth the cost of the DC motor.

Another way to possibly reduce the EMF of the alternator to allow for easier

pedaling is simply connecting in series a string of power resistors. This is the same

technique used by car designers when connecting the alternator.

Figure 5.12a: Wiring of Alternator[14] Figure 5.12b: Wiring of an Alternator in a Car[5]

Figure 5.12a shows that the field wire (green wire) is connected in series with a

warning light, or charge lamp, and a resistance in parallel with the lamp. This resistance

needs to be determined quite precisely. Too low of a resistance and the user would still

have the issue of trying getting over the ―induction hump‖ of the electromotive force and

35

start pedaling the bike. Too high of a resistance, and the alternator would never turn itself

on at low RPMs expected from the users on the bike [6].

Figure 5.12b shows the standard wiring of our Ford 3G alternator in a car. From

the highlighted blue section in the top right, a resistance of around 550Ω seems to be the

choice amount. Based off this number, we tested in the lab the optimal resistance to

connect in series with the field wire. We used multiple 100Ω adjustable power resistors

in parallel from the motors lab for testing. We found the actual resistance needed on the

field wire is much lower than the resistance used in a car. The resistance for the field wire

seemed the best balance for the EMF field of the alternator at 4-8 ohms. The car uses a

much higher resistance because the faster RPM of the car will be high enough to induce

the EMF in the alternator. The RPM rates a user would pedal at would not be fast enough

to induce the EMF of the alternator with such a high resistance on the field wire. More

data on the field resistance is shown in Test & Planning section as well as the Mounting

& Wiring section.

Mounting & Wiring:

In order for the alternator to produce power, it must be securely fastened to the

stand and connected correctly to the bike and all other components. Alternators are very

durable when connected correctly, but if connected incorrectly the alternator can be

destroyed very quickly and pose a serious injury threat to everyone around the system.

To mount the alternator on the bike frame, two pieces of remaining 2‖x3‖ wood

can be used to secure the alternator. The Ford 3G alternator has three mounting holes;

two on one side and one on the other. The alternator can be laid on top of the two cross

sections of wood across the back of the bike stand. The holes can then be marked and

36

drilled with a 3/8‖ bit. Three 3/8‖ 3‖ bolts and screws can be used to then thread and

secure the alternator to the pieces of mounting wood. These cross pieces of wood can

now be attached to the back of the stand with remaining angle ties from the construction

of the bike stand. It is recommended to first attach the pulley belt from the back tire to the

alternator head. Once they are connected, pull the alternator and attached pieces of wood

back until no slack is left in the belt. The belt must be tight between the two mediums in

order to reduce any belt slippage and slippage losses when the user pedals. Once the belt

is tight, mark the angle tie locations to connect the mounting wood pieces to the bike

stand firmly. A rough view of the mounting position can be viewed in Figure 5.13 and a

view of the connection between the alternator shaft and bicycle rim in Figure 5.14.

Figure 5.13: Mounting Alternator to Stand Figure Figure 5.14: Pulley Connection Between Alternator and Rim.

The direction in which the alternator is oriented to spin does not affect its output power.

The alternators rotor can be rotated either clockwise or counterclockwise and achieve the

same output values, as we found out by an initial setting up the alternator backwards.

Once the pulley belt is connected between the bikes back tire rim and alternator

head, and the alternator is mounted, the alternator must be wired to output DC power.

37

The three connections to be made, as shown in Figures 5.12, are the output wire, field

wire, and regulation wire. A simple battery charging connection is shown in Figure 5.15.

Figure 5.15: Battery Charging System Wiring.

In Figure 5.15, the alternator has three output wires labeled 1, 2, and BAT. The

wire labeled BAT is obviously the output of the alternator that is used to charge the

battery or to power an external load instantaneously. The wire labeled 1 is the field wire.

The field wire feeds current and voltage into the stator of the alternator to create an EMF

to produce the output DC power as described earlier in the report. A resistor and switch

are placed in series between the alternator and battery. Both of these components are used

to protect the alternator. The switches purpose as stated by Eagle and Olding, ―It is

equally important – perhaps even more so, actually – that the field coil wire not be

attached directly to the battery’s positive terminal. In a car, the field coil is connected to a

switch, a small warning light, and then the battery’s positive terminal. The switch isolates

38

the battery from the field coil when not in use. This is important, as otherwise the battery

will run itself down powering the field coil when the alternator is not operating. Some

kind of switch should always be wired up in between the field connection and the

battery.‖[6] The field will always pull current and voltage from the battery, regardless of

whether the alternator is running or not. Without a disconnect, the battery would be dead

before it is needed to excite the field when the alternator is actually running. The resistor

is used to protect the field from over-amperage that could damage lesser quality

alternators [6]. Without a resistor in series, the battery can output 14 volts and up to 6

amps to the field. Not only will this amount of power into the field possibly damage the

alternator, it will also create a very large EMF that would make human pedaling of the

rotor almost impossible due to the great resistance. As stated earlier, too low of a

resistance and the user would still have the issue of trying getting over the ―induction

hump‖ of the high EMF and pedal the bike; too high of a resistance, and the alternator

would never turn itself on at low RPMs expected from the users on the bike due to the

low EMF[6]. The wire labeled 2 on the alternator diagram in Figure 5.15 is the regulation

wire. This wire is usually hooked up directly to the positive terminal of the battery. It

senses the voltage on the line and compares the output voltage to this sensed voltage. It

creates a feedback in the alternator controller that regulates the output of the alternator.

One of the main objectives of this project is to produce a 24 volt DC output to charge an

array of batteries. This would require a DC-DC converter at the back end of the alternator

to produce this; however, it was determined through testing that we could take advantage

of the alternator’s regulation wire to output 24 volts directly. If the regulation wire is

hooked up to a voltage source with the desired DC output, the output of the alternator

39

will be regulated to this voltage source. This only goes to a certain point that the

alternator is rated to go. In our case, we were able to regulate the output up to 22V on the

Ford 3G alternator. This is a much cheaper and simpler option to obtaining a 24 volt DC

output, rather than buying an expensive DC-DC converter to accomplish the same goal.

In summary, the field wire of the battery must be connected to a certain resistance

and switch to protect the alternator, and battery and make human pedaling of an

alternator possible. Also the regulation wire can be used to manipulate the desired output

voltage of the alternator up to a certain voltage limited by the rating of the specific

alternator. Finally, the alternator must be mounted in such a way to both hold the

alternator firmly, and create a strong tension between the alternator and back wheel to

avoid excess slippage losses.

40

VI. Integration & Testing:

Integration & Cost:

The integration process for this project is relatively simple and a majority of it has

been covered in detail in the design section. The first step of integration was securing the

bike into a stable stand for the system. Bikes are not easy objects to stabilize as they are

very sleek and have no obvious places to hold and secure. In order to find a way to secure

the bike, the idea of placing pegs on the back of the bike was found as the best solution.

The pegs had to be cut so that the bolt was flush to its end otherwise our axel did not

offer enough thread to screw the pegs on. To hold the bicycle in the designed wood stand,

we installed common bicycle pegs so the rear axle would protrude outside of the frame of

the bicycle. Holes were then drilled into the wood and the pegs were inserted into the

drilled holes. The boards stranding upright containing the pegs were braced in all

coordinate directions. The stand was extended backwards to allow for motor mounting

positions. This allowed for any possible belt sizes; furthermore, for added safety a small

brace was built for the front wheel so that any torsion would not occur. The front wheel

was rendered stationary.

Mounting the motor was the next part of the integration. This was relatively

simple as two pieces of 2‖x 3‖ wood were tied to the frame and the alternator was bolted

to the mounting wood accordingly. The alternator had to be positioned at the right distant

back from the bike to give a strong enough tension on the belt to avoid excess slippage

losses from pedaling.

41

The battery and resistors had to be wired and integrated with the alternator in

order to complete a system that could charge a battery according to the standards set in

the requirement section of the report.

Also stated in the requirement section of the report was the absolute necessity of

the power generation bike system being as cheap as possible in order for it to be

financially viable for the DC House project. Table 6.1 shows a list of various parts and

equipment that were necessary for the completion of our entire project.

Table 6.1: Estimated and Actual Costs of Project

The actual amount of money spent on this project was very low thanks to

generous donations and available equipment accessible to students at Cal Poly. The

alternator and pulley belt were donated by Howard Siewert, a mechanic in Northern

California. The bicycle, battery, power resistor, and wires were all equipment that was

able to borrow from Cal Poly and Cal Poly students in order to test and demonstrate our

project.

42

While donations are possible and would be beneficial to the DC House’s success,

an estimated cost table was made to estimate the total cost of our design excluding any

donations. All the estimated costs were researched by calling local scrapyards, shops, and

average prices from retailers during the building process. The estimated cost is still

within a respectable cost range of just over $200.00. The cost is very respectable for the

scope of the system with the majority of the cost due to the battery; however, the battery

is not an intrinsic cost of only our system, but rather the entire DC House project. The

battery array will be charged by the various other sustainable systems, and be considered

split cost between all DC House projects. This drops the total cost of the power

generation bike system even lower.

43

VII. Tests & Planning:

Planning:

The test plans for the power generating bike include laboratory testing and field

testing. We had two sizes of Ford 3G alternators available for the project: the 95 amp

model and the 130 amp model. The nominal current outputs for the two types can be seen

in Figure 5.8. We used the 95 amp alternator in laboratory testing and the 130 amp model

was attached to the bike stand. The available DC motor was also testing in the laboratory

to determine its output characteristics based on RPM.

In order to be able to record accurate data for the alternator we decided to use an

induction motor as a prime-mover in the laboratory. The motor was run by a Variable

Frequency Drive (VFD), which allows for precise control over the RPM of the alternator

in order to understand the outputting characteristics of the motor based on the RPM. This

also has the added benefit in we could measure the input power and hence calculate the

efficiency of our alternator. The basic bench set up to record data for the 95 amp Ford 3G

alternator is shown in Figure 7.1. The DC motor was testing in the same manner as the

alternator for laboratory testing.

Figure 7.1: Alternator Bench Setup

44

The testing in the field, with the bicycle setup, was less accurate but just as

important of information. The field setup was running the 130 amp alternator attached to

the bicycle stand and wired to the components accordingly to the wiring section. A

simple bicycle RPM meter can be connected to the back wheel of the bicycle. If you

multiply the RPM measured by 10, we receive the approximate RPM of the alternator

shaft. This multiplication is the result of the 10:1 diameter ratio between the bike wheel

and alternator head. The bike diameter measured 24 inches while the alternator head

measured less than 2.5 inches, which gives us the said 10:1 ratio. The issue with running

a field test for the alternator current output is the difficulty of the peddler to hold a

constant pedaling rate with the varying EMF strength and other external conditions.

Testing:

The results of the alternator in the laboratory were very similar to the expected

data for the 95 amp Ford 3G alternator. There were two factors to determining the output

of the alternator: the RPM and the field resistance. The field resistance effect on the

output current proved quite linear at high RPMs, while at RPMs lower than 1200 a

resistance about 10 ohms kills nearly all of the current output and a resistance under 4

supplies an excess amount of current to the field. A resistance between 5-8 ohms proved

to be the optimal field resistance when in the human pedaling RPM rate, between 0-1500

RPM, which is much lower than a car’s standard RPM rate.

The RPM of the alternator proved to be the more important of the two

determining factors. The field current, regardless of the current, generates no output

power if the RPM rate is too low. We tested the alternator through various RPM values

45

with a 4 ohm field resistor attached. The data received and the calculated values of

efficiency are shown on Table 7.1.

Table 7.1: Output Current based on RPM for Ford 3G Alternator

The voltage vs. the RPM proves to be completely unchanging as expected, due to the

regulation of the alternator’s controller. The regulation wire was connected to the

battery’s positive terminal which regulated the output voltage to 12.8 V, shown in Figure

7.2.

Figure 7.2: Voltage Output based on RPM of Ford 3G alternator

The current output vs. the RPM of the alternator is very similar to the expected data of

shown in Figure 4. The output current is minimum until around 1200 RPM. Once that

RPM rate is surpassed, the output current increases greatly. The resulting graph can be

seen in Figure 7.3.

0

5

10

15

0 1000 2000 3000

Volts vs RPM

volts

46

Figure 7.3: Current Output vs RPM

As stated before, an alternator is more efficient at higher a higher RPM. The idea to

rewrap the rotor or stator of the alternator with thinner wire could shift the curve in

Figure 7.3 to the left, allowing for more power output at the lower RPM expected from

our power generation design. The output power is just the multiplication of the output

current and the regulated voltage. This can be seen in Figure 7.4.

Figure 7.4: Output Power vs RPM

The efficiency was calculated by dividing the output power by the input power recorded

from the VFD. The input power recorded may be incorrect as the labs power meters

recorded a different input power value than the VFD, so it is unsure which value was

more accurate. The efficieny results are shown in Figure 7.5.

0

5

10

15

0 1000 2000 3000

Current vs RPM

Amps

0

50

100

150

0 1000 2000 3000

Watts vs RPM

Watts

47

Figure 7.5: Efficiency of alternator vs RPM

From extensive testing with the system design, we received similar results from

the laboratory data. For the field testing, a 130 amp Ford 3G alternator was used. The

curve from Figure 5.8 shows the alternator produces higher currents at lower RPMs

which seemed to be the case for testing.

A 7 ohm field resistor was used in field testing in order to allow for easier

pedaling by the users. When pedaling at an easy pace of about 1000 RPM at the

alternator shaft, we were recieveing 14 volts regulated out and 1 to 1.5 amps. This gives a

power output from 14-21 watts when pedaling at an easy pace. A user was able to

produce an RPM of 1500 at the alternator shaft, with 15 voltage at around 3.4 amps. This

gave a respectable 51 watts of power output; however, the pace would be hard to sustain

for any lenghty amount of time.

As shown early in the DC motor section in Figure 5.11, the output voltage vs

RPM of the DC motor proved to be linear. The current was low, never passing 1.5 amps.

This power output of the DC motor would not have been enough to charge the stator field

of the alternator as previously desired. A larger DC motor could have possibly supported

the alternator field current at lower RPMs; however, the cost of such a motor would not

have been finacially viable.

0

10

20

30

40

0 1000 2000 3000

efficiency vs RPM

% efficiency

48

VIII. Conclusion:

Through research and testing, this project aimed to design and implement a first

phase of sustainable energy resources for the DC House Project. The project goal was to

supply a battery array with a 24 volt DC output. This goal had to be met within the

constraints of a low production cost and high safety. The project had to offer a durable

product with relatively good efficiency. We believe we accomplished this goal. The

project results were conclusive with the alternator as an energy provider. Alternators are

great tool when running at a high RPM, but less efficient when running at a lower RPM,

like that provided by users pedaling the bike. There are many other options to explore to

find the most efficient way of producing DC power from a bicycle, but we believe

modifying an alternator is the most cost effective way to reach that goal. Unfortunately,

the scope of time for our project did not allow for rewiring an alternator to test for the

power output improvements at lower RPMs; however, we hope that students in the next

phase of the DC House Project will be able to offer their time to try this improvement, as

well as other ideas. The bike stand and coupling between bike and motor have room for

improvement as well like to reduce torque and tension to the stand and reduce slippage

between the belt coupling. Further stress tests over a longer period of time would also be

beneficial in order to determine the actual average lifetime of our product, and if the cost

of production is worth the provided power within that lifetime.

Our greatest difficulty came with wiring the alternator correctly to run on our bike

system. The field resistor has to be set to a very specific resistance to find the perfect

strength of the EMF in the alternator to provide a high power output and low pedaling

49

resistance. More testing can be done in the motors laboratory to find this range of

resistances based on the generated RPM rate of the users.

The cost of the bike stand was relatively low compared to many other sustainable

energy sources. The cost is just about $200.00, when including a new battery; however,

when the battery cost is excluded, the system is closer to $140.00 to produce. This cost

would only decrease, if parts and equipment were bought in higher quantities for mass

production. We believe our design is a great start in developing a low cost, low upkeep

device that will allow power production whenever the user desires. Without access to

power anything we can provide to the less fortunate people of the world will help. Our

system along with solar, wind, and hydroelectric systems will help provide power for DC

House users to run simple appliances like lights, medical equipment, and fans that so

many of us take for granted on a daily basis.

50

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2011. http://www.eia.doe.gov/oiaf/ieo/world.html

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[12] Alexander, Charles; Sadiku, Matthew (2007). Fundamentals of Electrical Circuits,

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[13] Keyword Pictures. June 2011.

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[14] Bobs Garage. June 2011. http://www.bobsgarage.110mb.com

51

Appendices:

Gantt Chart:

52

Bill of Materials: