dalhousie university- mechanical engineering...

Dalhousie University- Mechanical Engineering MECH 4010 & 4015

Design Project I

Conceptual Design Report

Reel Mower

Team 15

Clark Calnan

Alex Higgs

Jean-Francois Lefort

Erica McAdam

Submitted: November 8, 2013

MECH 4010/4015 Group 15 Reel Mower

Dalhousie University: Dept. of Mechanical Eng of 30

Table of Contents

List of Tables ................................................................................................................................................. 3

List of Figures ................................................................................................................................................ 3

1. Project Information ............................................................................................................................ 4

1.1. Project Title ................................................................................................................................. 4

1.2. Project Customer ........................................................................................................................ 4

1.3. Group Members .......................................................................................................................... 4

1.4. Useful Definitions and Acronyms ................................................................................................ 4

2. Conceptual Design Summary .............................................................................................................. 7

3. Background and Context .................................................................................................................... 8

4. Requirements ................................................................................................................................... 11

5. Functional Block Diagram ................................................................................................................. 12

6. Concept Classification Trees and Concept Combination Tables ....................................................... 14

7. Overview of Conceptual Solution Alternatives ................................................................................. 15

7.1. Concept 1: Motor, gearbox, batteries mounted in-line with blade reel .................................. 15

7.2. Concept 2: Four-wheel square base ......................................................................................... 16

7.3. Concept 3: Two wheel design with handle offset ..................................................................... 17

7.4. Concept 4: Two wheel design with drive train attached to the frame ..................................... 18

8. Feasibility .......................................................................................................................................... 19

8.1. Electric Motor ........................................................................................................................... 19

8.2. Battery Packs ............................................................................................................................. 20

8.2.1. Battery Pack Run Time ....................................................................................................... 21

8.2.2. Battery Pack Charge Time .................................................................................................. 22

8.2.3. Battery Pack Weight ........................................................................................................... 22

9. Testing and Verification .................................................................................................................... 24

9.1 Requirement Testing ................................................................................................................ 24

9.2 Proof of Concept ....................................................................................................................... 24

10. Required Technical Expertise............................................................................................................ 26

11. Resources and References ................................................................................................................ 27

11.1. Facilities..................................................................................................................................... 27

11.2. Additional Advisors ................................................................................................................... 27

11.3. Funds ......................................................................................................................................... 27

References .................................................................................................................................................. 28

Appendix A- Motor and Battery Research .................................................................................................. 29



List of Tables

Table 1- Team 15 contact information ......................................................................................................... 4

Table 2- Comparison of rotary vs. reel mowers ............................................................................................ 8

Table 3- Comparison of gas vs. electric mowers ........................................................................................... 9

Table 4- Basic design requirements ............................................................................................................ 11

Table 5- Technical design requirements ..................................................................................................... 11

Table 6- Pros and cons of concept 1 ........................................................................................................... 15




Table 10- Time measurements for 6 meters of mower travel .................................................................... 19

Table 11- Battery pack run time feasibility ................................................................................................. 21

Table 12- Battery cell total weight .............................................................................................................. 22

Table 13- Engineering and technical expertise ........................................................................................... 26

List of Figures

Figure 1- Manual reel mower components .................................................................................................. 5

Figure 2- Gas powered mower...................................................................................................................... 9

Figure 3- Manual reel mower ..................................................................................................................... 10

Figure 4- Electric reel mower functional decomposition diagram ............................................................. 12

Figure 5- Concept classification tree providing cooling solutions .............................................................. 14

Figure 6- Two wheel, in-line design ............................................................................................................ 15

Figure 7- Four wheel design ........................................................................................................................ 16

Figure 8- Handle offset design .................................................................................................................... 17

Figure 9- Two wheel design, drive train mounted on handle ..................................................................... 18



1. Project Information

1.1. Project Title

Team 15 has been tasked with the design and build of an electric reel mower.

1.2. Project Customer

The reel mower is a faculty suggested project, brought forth by Dr. Swan. Team 15 will work closely

with Dr. Swan to ensure the requirements are met.

1.3. Group Members

Team 15 consists of four group members and a faculty advisor. The team information can be seen in

table 1:

Table 1- Team 15 contact information

Member Phone Number Email Clark Calnan 902-483-6268 [email protected]

Alex Higgs 902-237-8316 [email protected]

Jean-Francois Lefort 902-401-2138 [email protected]

Erica McAdam 902-830-3997 [email protected]

Dr. Lukas G. Swan will serve as the faculty advisor. Dr. Swan can be reached at [email protected].

1.4. Useful Definitions and Acronyms

Manual reel mowers are simple mechanically. Figure 1 displays the important components of a

manual reel type mower.



Figure 1- Manual reel mower components (http://home.howstuffworks.com/reel-mower2.htm, accessed 2013)

Useful definitions:

x Handle-The handle is pushed by the operator, transferring the power into the drive

components of the mower.

x Rollers- The rollers provide stability.

x Cutter Blade- The spinning blades of the mower do not actually cut the grass. It manipulates

the grass to be cut by the cutter blade or bedknife. The cutting surface shears the grass as it

is caught between the spinning drum and the cutter blade.

x Main Wheel- The main wheels are the contact point with the ground. An internal gear mesh

allows the power to be transmitted to the spinning drum.

x Pinion Gear- The pinion gear transfers the power from the rotation of the main wheel to the

axle and spinning blades.



x Brush Bar- The brush bar is used to bend over the grass so it can be cut properly.

x Axle- The axle transfers the power from the pinion gear to the spinning blades.

x Blade Reel- Although this component is called the blade reel, it does not cut the grass. It

manipulates and positions the grass to be cut effectively by the cutter blade. The contact

between the blade reel and cutter blade provides a shearing force which cuts the grass.

x Adjustment Screws- The adjustment screws are used to adjust the height of the cutter blade

for variable grass length.

These definitions will be used to describe the operation and design of the electric reel mower in this

report.



2. Conceptual Design Summary

The conceptual design report highlights the design process used for this project. This report

contains useful information with regards to the thought process and techniques used in analyzing

alternative solutions.

The background and context for this project are discussed in detail in this report. Manual powered

reel mowers do not have enough power or torque for cutting long, thick and wet grass. By designing

an electric mower with increased power, the mower can be used in more robust applications.

The requirements that have been defined were established by doing market research and

examining the problems that arise while using a manual mower. Basic and technical requirements

have been defined for the project. Basic requirements include physical characteristics such as

weight and dimensions. These are fundamental to the safe and efficient operation of the mower.

Technical requirements have been defined after initial calculations. The basic requirements will not

change throughout the process; however the technical requirements are subject to change. A

detailed list of basic and technical requirements can be found in section 4.

The functional block diagram in section 5 shows the flow of energy, materials and signals in the

mower.

The concept tree in section 6 shows the process used for making sub component decisions.

Several alternative designs have been sketched and analyzed in section 7. These include two and

four wheel design. There are several pros and cons associated with each design including stability,

maneuverability and overall weight.

The feasibility of critical components such as battery packs and electric motor selection has been

analyzed in section 8. This allows for critical components to be identified.

The testing and validation procedure for the requirements is outlined in section 9. These

procedures include running the mower, measuring the dimensions and weighing the mower.

Section 10 describes the engineering expertise that this project requires such as CAD modeling and

electrical engineering design.

Some external resources are defined in section 11.



3. Background and Context

The objective of this project is to design and build a battery powered electric reel mower. There are

several reasons why it is beneficial. Table 2 lists the advantages and disadvantages of a rotary and

reel mower.

Table 2- Comparison of rotary vs. reel mowers

Rotary Reel

Advantages - Powerful Engine

- Cuts all grass types

- Cuts lawn evenly

- Provides a close cut

- Clean cutting method

Disadvantages - Tears grass, which could result

in discoloration and increase

risk of disease

- Uneven cut

- Doesn’t provide a close cut

- Less powerful

- Can be tiring if cutting a

very large lawn

- Not well suited for long

grass

Rotary mowers have a horizontal fan-style blade that spins in a circular motion. They also have a

large motor so they can provide enough power to cut thick grass. However, with the horizontal

cutting motion the grass can be torn. When grass is torn rather than cut it can become discoloured

and the frayed ends make it more susceptible to disease.

Many manually powered reel mowers do not generate as much power as rotary mowers, therefore

they can have a difficult time cutting through thick grass and weeds. With the reel mower, the

power of the blade reel is directly related to how much force the user applies. If the operator cannot

produce a large enough force, they may have difficulties operating the mower. A battery powered

reel mower would separate the rotation of the blade reel from the rotation of the wheels, allowing

the drum to spin faster and making it less susceptible to jamming. Reel mowers also cut lawns more

evenly and much closer.

The cylindrical drum on a reel mower cuts every individual blade of grass like a pair of scissors.

This produces a clean cut, which will protect the grass from disease and increases the health of the

grass. Table 3 lists the advantages and disadvantages of a gas and electric mower.



Table 3- Comparison of gas vs. electric mowers

Gas Electric

Advantages - Cordless

- Long run time

- Quiet

- No gas spills

- Environmentally friendly

- Can be cordless

Disadvantages - Noisy

- Produces emissions

- Gas spills

- Requires oil changes

- Vibrations

- Limited run time

- Special charging

equipment

Gas powered lawn mowers have a negative impact on the environment. They produce toxic

emissions, are very noisy and gas spills can occur. By using an electric reel mower instead of a

gasoline powered mower, these problems are eliminated or mitigated. A battery powered reel

mower does have a few disadvantages including limited run time and requiring special equipment

to recharge the batteries. Limited run time can be mitigated through the use of two battery packs;

one will be in use while the other is charging. The special charging equipment introduces an up

front cost but this expense can be offset through the savings in gasoline purchases.

Figure 2- Gas powered mower (http://www.flickr.com/photos/14168332@N07/3716809618/)



Figure 3- Manual reel mower (How To: Service Your Reel Mower,http://www.apartmenttherapy.com/how-to-service-your-reel-mower-54176)

Taking these design elements into consideration, it would be beneficial to design an electric

powered reel mower. This project will challenge the team to think on an innovative level, testing

the ability to design mechanical and electrical systems previously learned in the engineering

program.



4. Requirements

The requirements in this section have been defined after extensive market research. These

requirements will ensure that the final product can compete with other products on the market.

Table 4 lists the basic design requirements, which will remain the same throughout the duration of

the project.

Table 4- Basic design requirements

Requirement Description Justification

B-1 The blade reel shall not exceed 20 inches

(51 cm) in width.

This width allows for an even cut over

uneven terrain.

B-2 The overall width of the reel mower shall

not exceed 30 inches (76 cm). Less than 30 inches allows the mower to

be pushed through a standard door frame.

B-3 The mower shall weigh less than 50 lbs

(22.7 kg). One person may operate and lift the

mower.

B-4 There shall be two battery packs. Two battery packs allows for increased run

time by providing the ability to swap

batteries.

B-5 The battery packs shall last at least 30

minutes on one full charge when used to

perform regular lawn maintenance.

A 30 minute run time is the industry

standard. This will allow adequate run time

for average lawns while maintaining an

appropriate weight.

B-6 The battery packs shall charge in 30

minutes or less. A charge time that is equal to the run time

will allow for efficient battery swapping

when mowing large lawns.

Table 5 lists the technical design requirements; these are subject to change during the course of the

project.

Table 5- Technical design requirements

Requirement Description Justification

T-1 The mower will operate with a 150 W

electric motor.

An average individual provides 60 W while

operating a manual reel mower. 150 W is a

significant improvement in power.

T-2 Lithium ion battery packs will be used. The energy density (Wh/kg) of lithium ion

battery cells is significantly higher than

other battery chemistries.



5. Functional Block Diagram

Figure 4 is a functional decomposition diagram for the design of the electric reel mower. The figure

identifies the transfer of energy with red arrows, signals with blue arrows, and the transfer of

material with green arrows.

Figure 4-Electric reel mower functional decomposition diagram

The electric reel mower will receive three inputs: electricity during recharging, operator energy

input by moving the mower, and a signal input from the operator.

Electrical energy is stored in an onboard battery pack. From there it is transferred to the motor and

also dissipated as heat during operation. Electrical overheating is a concern; therefore

consideration will have to be placed into the transmission of the electrical power, as well as the

method of heat dissipation. Heat sinks or fans may be used to effectively transmit the excess heat

energy. Once electrical energy is transferred to the motor, it is then transferred to the reel mower’s

blade reel. This can be accomplished with a gearbox, which will adjust the motor’s output rotation

to the desired blade reel velocity. Finally, the mechanical energy in the blade reel is transferred to

the lawn, cutting the blades of grass.



Operator energy input is transferred to the mower through the mower handle as well as through

the wheels. These components should allow for easy and comfortable movement. Adjustable handle

heights and a properly designed frame should make this possible. Mower movement is crucial for

allowing the mower to effectively cut grass. Cutting will occur as a combination of the spinning

blade reel and forward movement. This results in the production of grass clippings, which

represent a material output of the reel mower.

An operator signal input will be directed to the onboard motor controller. This signal will be

transferred from the controller to the motor. The power that this controller will require will be

determined by a feedback control loop, which will compute the error between a desired blade reel

rotation and an encoder reading of the actual rotation and will attempt to minimize it.



6. Concept Classification Trees and Concept Combination Tables

One area of interest for this design is the method of heat dissipation from the battery pack and the

electric motor. It is expected that these components will require a cooling system, as the battery

discharge rate will be rapid. Figure 5 presents a concept classification tree for possible cooling

solutions.

Figure 5- Concept classification tree providing cooling solutions

The favored options from this classification tree involve air cooling from a fan. This would not

require a substantial amount of power and could either be driven by the electric motor or by the

rotary motion of the wheels.



7. Overview of Conceptual Solution Alternatives

Several alternatives were considered for the design of the electric reel mower. These designs and

the pros and cons are highlighted in the following sections.

7.1. Concept 1: Motor, gearbox, batteries mounted in-line with blade reel

Figure 6- Two wheel, in-line design

Table 6- Pros and cons of concept 1

Pros Cons

Compact design The inertia of the spinning drum may cause

the mower to flip. To prevent this, a counter

moment system would need to be

implemented

Easy to maneuver The overall length of the mower may exceed

30 inches

Able to handle uneven terrain Not as stable as a four wheel design



7.2. Concept 2: Four-wheel square base

Figure 7- Four wheel design


Pros Cons

Improved stability over a two wheel design Increase in weight and cost

Easy to mount motor, batteries and gearbox Ability to handle uneven terrain would

decrease

Not as easy to maneuver as the two wheel

design

Difficult to mow up against an edge or wall



7.3. Concept 3: Two wheel design with handle offset

Figure 8- Handle offset design


Pros Cons

Offset will prevent the handle from flipping

over the mower

Difficult to maneuver the mower because of

the offset

Limited space available for mounting the

motor, gearbox and batteries

Difficult to operate over uneven terrain

Extra weight on handle

Difficult to transmit power from motor to

blade reel



7.4. Concept 4: Two wheel design with drive train attached to the frame

Figure 9- Two wheel design, drive train mounted on handle


Pros Cons

Compact design Not as stable as a four wheel design

Installing the drive train on the handle

would mitigate the rolling effect caused

by the inertia of the blade reel

Limited space to mount drive train

Two wheel design increases

maneuverability and ability to handle

uneven terrain

Extra weight on handle and difficult to

transmit power from motor to blade reel



8. Feasibility

8.1. Electric Motor

One crucial sub-function is the provision of power to the blade reel. This will be accomplished with

an electric motor, as outlined by the basic requirements of this project. In order to assess the

requirements of this motor, a manual reel mower was examined.

To calculate the mower power and blade reel rotational velocity, the translational velocity at which

the manual reel mower is pushed was calculated by replicating mowing speed and determining the

time it takes to travel 6 meters. Table 10 shows the results of this experiment:

Table 10- Time measurements for 6 meters of mower travel

Measurement Time (s)

1 4.85

2 4.50

3 4.33

4 4.70

5 4.60

6 4.54

7 4.62

8 4.59

9 5.03

10 4.80

Tavg= 4.68

Typical operator walking speed was determined using the average time to walk 6 meters with the

following calculation:

𝑣 = = .

= 1.30 m/s (1)

To calculate the rotational velocity of the blade reel, the drum diameter was measured. The

following calculations and simple physical relationships were used to determine the rotational

velocity of the manual reel mower.

D = 0.25 m

V = 1.30 m/s



Gear ratio = 4.4: 1

C = π ∗ D = 0.785 m (2)

ω = = 99.4 RPM (3)

ω = ω ∗ Gear ratio = 437 RPM (4)

This magnitude of velocity will easily be exceeded by most electric motors. A gearbox providing a

gear reduction of at least 5:1 will likely be required to reduce the provided rotational velocity to a

value of approximately 450 RPM.

The required force to operate the mower was measured using a simple bathroom scale. The

measured operator input force to drive the mower at a typical speed was determined to be

approximately 50 newtons.

𝑃 = 𝐹𝑣 = (50N) ∗ 1.30 ≅ 60 W (5)

This approximate value of power input represents the required operator input to move the mower

and spin the blade reel. The electric reel mower must provide more power than a manual reel

mower. Values ranging from 150 to 250 watts represent the desired power that the electric motor

must provide. These values are easily obtainable with many electric motors.

Various motor types were examined in order to select the most appropriate electric motor for this

application. Following research and consultation with the design team supervisor, it was

determined that a brushless DC motor paired with a gearbox would be capable of delivering the

required amount of power and velocity for this application, while performing reliably at a relatively

high efficiency. This type of motor would also dissipate heat much more readily than other motor

types due to the location of electromagnets on the stator.

Appendix A contains further information obtained from motor research.

8.2. Battery Packs

Two battery packs will be used to supply the required power. One pack will be in use while the

other is charging. Various battery chemistries are available to perform this task. After conducting

research and assessing each type of battery cell, lithium ion batteries will likely be used as defined



in the technical requirements. Lithium ion (Li-Ion) battery cells can be expensive, however, the

power-to-weight ratio is significantly higher than other battery chemistries. A direct comparison

can be seen in Table B in Appendix A. Unique cells will be a critical component as they are

considered to be a specialty product.

The motor described in section 8.1 is 150 W. Several types of Li-Ion battery cells are available, such

as prismatic and cylindrical. Prismatic cells can be packed tighter than cylindrical cells. Since the

cells will be discharged in a relatively short time, heat generation will be a problem. Cylindrical cells

would be the best selection due to the air gaps between the cells when packed together. A cooling

system would be used to force air through these gaps, which would increase heat transfer and

reduce the risk of damaging the cells.

The 150 W motor will be powered with a battery pack of 48 V or 72 V. These voltages provide low

current draw for 150 W. Low amperage reduces the nominal capacity required of the packs,

however it increases the overall weight of the pack. The feasibility of these two characteristics will

be assessed in the following sections.

8.2.1. Battery Pack Run Time

A thirty minute run time is needed as defined in the requirements section. Table 11 illustrates the

capacity required from the battery packs to achieve this run time:

Table 11- Battery pack run time feasibility

Power Voltage Current (I=P/V) Ah (A*0.5hr) Ah*0.8 (OF)

150 W 48 V 3.13 1.56 1.95

150 W 72 V 2.08 1.04 1.30

Table 11 shows that the capacity required for 48 V and 72 V is 1.95 Ah (amp hours) and 1.30 Ah,

respectively. Preliminary battery research showed that there are many Li-Ion cells available with a

nominal capacity greater than 1.95 Ah and 1.30 Ah. One specific model is the “ANR26650m1”

cylindrical cell made by A123. The nominal voltage is 3.3 V and the nominal capacity is 2.3 Ah.

The capacity required for the motor is less than the 2.3 Ah available from the battery cell. Battery

cells connected in series increases the voltage, however the capacity (Ah) remains the same.

Connected battery cells in parallel increases the capacity but the voltage remains the same. With

this cell comparison, it is evident that the run time required from the cells can be achieved using



several cells connected in series. To add a larger operational factor, the same size pack can be

connected in parallel to double the capacity.

After research into available cells and basic electrical calculations, it has been determined that a

battery pack run time of 30 minutes is feasible.

8.2.2. Battery Pack Charge Time

The charge time is 30 minutes as previously defined in the requirements section. The feasibility of

this requirement was assessed by calculating the current required to charge the cells in 30 minutes.

The following equation can be used to relate the current required to charge in a certain time

interval:

𝐼 = ( ℎ) (ℎ) (6)

Evaluating equation 6 with the nominal capacity of 2.3 Ah (A123 cell) and a charge time of 30

minutes, 4.6 A is required. This amperage is easily obtained with a modern Battery Management

System (BMS).

The maximum allowable charging current for the rapid charge of the A123 Cell is 10 A (A123,

2006). The evaluation of 4.6 A demonstrates that a 30 minute run time is feasible.

8.2.3. Battery Pack Weight

The overall weight of the mower is required to be less than 22.7 kg. A measurement of the manual

push mower was carried out and it was determined to weigh 11.4 lbs. This allows for a maximum of

11.4 kg of added material such as the motor, battery pack and housing.

To determine the weight of an individual battery pack, the “ANR26650m1” cylindrical Li-Ion

battery cell was used for comparison. With a nominal voltage of 3.3 V, and a weight of 0.07 kg per

cell table 12 shows battery pack weight characteristics:

Table 12- Battery cell total weight

Voltage (V) Number of Cells Bare Cell Weight (kg) Total Pack Weight (kg)

48 15 1.1 2.1

72 22 1.5 3.1



The weight of the battery pack and the weight of the motor described in sections 8.1 and 8.2 show

that incorporating a motor and battery pack while limiting the weight to 50 lbs is feasible.



9. Testing and Verification

There are several tests which will be performed to ensure that the battery powered reel mower

satisfies all of the necessary requirements. The requirements were split into two categories: basic

and technical requirements. The basic requirements will be used as a guide throughout the design

process and will be verified once the mower is complete. Precautions will be taken throughout the

course of the project to ensure that these requirements are met. The testing required has been

broken into two sections: requirement testing and proof of concept testing. The purpose of the

requirements testing is to prove that the basic requirements have been met. The proof of concept

testing will be used to determine the feasibility of the technical requirements at an early stage in

the design.

9.1 Requirement Testing

The physical characteristics of the mower, such as the dimensions and weight will be verified using

simple measurement techniques. The dimensions will be verified using a tape measure and the

weight will be verified using a scale with a resolution of 0.05 kg. The resolution of these

measurement devices is appropriate for these tests.

To test the functionality of the battery packs, two experiments will be done. The first will consist of

timing how long it takes for one of the battery packs to fully charge. The second test will consist of

timing how long it takes to fully discharge the battery while the mower is being used.

9.2 Proof of Concept

Three proof of concepts will be done. The first test will be performed to determine the heat

generation which occurs during a quick battery discharge. This test will determine if a cooling

system must be implemented into the design. This experiment will be done by connecting a battery

pack to an electrical resistor, which will discharge the battery in 30 minutes. The heat generation

will be monitored closely by measuring the temperature increase of the surrounding air.

The second test will occur at an early stage in the design process and will consist of hooking up an

electric motor of approximately 150 watts to the manual reel mower. This will operate the same

way as a battery-powered motor. During the test, the performance of the motor and electrical feed

will be measured. This will allow the average power to be calculated.



A third test will be performed to determine the required power input from a reel mower operator.

This will be done by measuring the input force and walking speed. With these two measurements,

the power required to turn the blade reel can be calculated. A digital scale will be fixed to the

handle of the manual reel mower. When the operator applies a pushing force to the scale, the

weight will be recorded from the scale and monitored.

If these tests are successful, the proposed design will continue as planned. If these tests reveal

conceptual design errors, design modifications will be made.



10. Required Technical Expertise

The design of the reel mower will require mechanical and electrical engineering skills. Detailed CAD

drawings will be required for the construction of the mower. Basic assembly skills will be needed

when the prototype is built. Table 13 shows the engineering expertise required for this project and

the level of knowledge that each individual has:

Table 13- Engineering and technical expertise

Technical Area Team Member Responsible Level of Expertise SolidWorks/CAD Erica McAdam Medium Welding JF Lefort Low Electrical/Programming Clark Calnan Medium-Low Electrical Wiring JF Lefort Low Mech. Assembly Erica McAdam Medium-Low Battery Spec. Alex Higgs Low



11. Resources and References

There are several resources required for the success of this project. These resources include testing

facilities, additional expertise and extra funding.

11.1. Facilities

In order to test some of the electrical equipment such as the battery discharge rate and mower

power train, a testing facility will be needed. Dr. Swan has offered his lab and expertise for these

tests. In order to use these resources, a test and safety plan will be done to his satisfaction.

Assembling the mower will required space and tools. If the design studio is insufficient for the

project, personal workshop space and tools will be used.

11.2. Additional Advisors

To perform the proof of concept test, Dr. Allen has offered a 150 W electric motor. A safety and test

plan will be drafted and Dr. Allen will play a small role in advising the team on this test.

11.3. Funds

The scope of work for this project is budget-dependent. If sufficient funds are not available from the

department, several third party companies will be approached for small donations.



References

A123 Systems Inc. High Power Lithium Ion ANR26650m1.2006.



Appendix A- Motor and Battery Research

From Wikipedia: http://en.wikipedia.org/wiki/Electric_motors#Comparison_by_major_categories

Table A- Summary of pros and cons for different motor types

Type Advantages Disadvantages Typical application Typical drive, output

Brushed

DC

Simple speed

control

Maintenance (brushes)

Medium lifespan

Costly commutator and

brushes

Steel mills

Paper making

machines

Treadmill exercisers

Automotive

accessories

Rectifier, linear transistor(s) or

DC chopper controller.[73]

Brushless

DC motor

(BLDC)

or

(BLDM)

Long lifespan

Low maintenance

High efficiency

Higher initial cost

Requires EC controller

with closed-loop control

Rigid ("hard") disk

drives

CD/DVD players

Electric vehicles

RC Vehicles

UAVs

Synchronous; single-phase or

three-phase with PM rotor and

trapezoidal stator winding;

VFD typically VSPWM inverter

type.[69][73][74]

Switched

reluctance

motor

(SRM)

Long lifespan

Low maintenance

High efficiency

No permanent

magnets

Low cost

Simple

construction

Mechanical resonance

possible

High iron losses

Not possible:

* Open or vector control

* Parallel operation

Requires EC controller[71]

Appliances

Electric Vehicles

Textile mills

Aircraft applications

PWM and various other drive

types, which tend to be used in

very specialized

/ OEM applications.[71][75]

Universal

motor

High starting

torque, compact,

high speed.

Maintenance (brushes)

Shorter lifespan

Usually acoustically noisy

Only small ratings are

economical

Handheld power

tools, blenders,

vacuum cleaners,

insulation blowers

Variable single phase AC, half-

wave or full-wave phase-angle

control with triac(s); closed-

loop control optional.[73]

Summary of DC properties (underlined items are safety related):

x Higher efficiency (greatest at low loads) and less wear than brushed

x More complex and expensive to control than brushed

x More torque per weight than brushed

x More torque per Watt than brushed

x More reliable than brushed

x Require no airflow for cooling (windings are on the stator and conduction is possible)

x No sparking from moving brushes

Some specs for BLDC motors from Maxon, Pittman, and Baldor:

x 250W for 24V, 36V, 48V approx. $650 Maxon

x 444W 27.6V with built in controller 8.3 kg Pittman

x Brushless DC available in ½ and ¼ HP Baldor

http://en.wikipedia.org/wiki/Electric_motors#Comparison_by_major_categories

http://en.wikipedia.org/wiki/Brushed_DC_electric_motor

http://en.wikipedia.org/wiki/Brushed_DC_electric_motor

http://en.wikipedia.org/wiki/Electric_motors#cite_note-St.C3.B6lting_p._9-76

http://en.wikipedia.org/wiki/Brushless_DC_electric_motor





http://en.wikipedia.org/wiki/Voltage_source

http://en.wikipedia.org/wiki/Voltage_source

http://en.wikipedia.org/wiki/Electric_motors#cite_note-Krishnan_.281987.29-72

http://en.wikipedia.org/wiki/Electric_motors#cite_note-Krishnan_.281987.29-72

http://en.wikipedia.org/wiki/Electric_motors#cite_note-Bose.2C_pp._480-481-77

http://en.wikipedia.org/wiki/Switched_reluctance_motor





http://en.wikipedia.org/wiki/OEM



http://en.wikipedia.org/wiki/Universal_motor

http://en.wikipedia.org/wiki/Universal_motor

http://en.wikipedia.org/wiki/Electric_motors#cite_note-St.C3.B6lting_p._9-76



Table B- Comparison of batteries (source

http://en.wikipedia.org/wiki/Comparison_of_battery_types, accessed 2013)

Chemistries V Wh/kg W/kg Cycles Wh/$

Lead Acid 2.1 30-40 180 500-800 5-8

Nickel Cadmium 1.2 40-60 150 1500 1.25-2.5

Nickel-Metal

Hydride

1.2 30-80 250-1000

500-1000 2.75

Lithium Ion 3.6 150-250 1800 400-1200 2.8-5

Lithium iron

phosphate

3.25 80-120 1400 2000+ 0.7-3.0

dalhousie university- mechanical engineering...

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