Initial Project Design Report

Project Design Report
Energy-appropriate community vehicle
Team 1
The Goonies
Jim Bader
Chase Barnhart
Damon Givens
Ryan Helbach
Kevin Kirch
Brad Painting
Camille Robinson
Brandon Smith
Michael Smith
May 29th 2007
Abstract
The reliance on fossil fuels used for transportation results in a need for vehicles that offer a more
energy appropriate solution to short distance transportation needs. The initial needs statement is
defined, along with the initial customer needs assessments. The target specifications for the
vehicle and all relevant research on related patents and regulations are included in this report as
well as the conceptual design, prototype design and final vehicle design.
1.0 INTRODUCTION....................................................................................................... 4
1.1 INITIAL NEEDS STATEMENT.................................................................................. 5
2.0 CUSTOMER NEEDS ASSESSMENT....................................................................... 5
2.1 WEIGHTING OF CUSTOMER NEEDS..................................................................... 6
3.0 REVISED NEEDS STATEMENT AND TARGET SPECIFICATIONS ....................... 9
4.0 EXTERNAL SEARCH............................................................................................. 11
4.1 BENCHMARKING .................................................................................................. 13
5.0 CONCEPT GENERATION ...................................................................................... 15
5.1 PROBLEM CLARIFICATION.................................................................................. 15
5.2 CONCEPT GENERATION ...................................................................................... 18
6.0 CONCEPT SELECTION ......................................................................................... 26
6.1 DATA AND CALCULATIONS FOR FEASIBILITY AND EFFECTIVENESS
ANALYSIS .................................................................................................................... 26
6.2 CONCEPT SCREENING ........................................................................................ 32
6.3 CONCEPT DEVELOPMENT, SCORING AND SELECTION.................................. 34
7.0 FINAL DESIGN ....................................................................................................... 40
7.1 DESIGN DRAWINGS, PARTS LIST AND BILL OF MATERIALS ....................... 104
7.2 HOW DOES IT WORK?........................................................................................ 118
7.3 HOW IS IT MADE? ............................................................................................... 125
8.0 CONCLUSIONS.................................................................................................... 142
APPENDIX A: INTERVIEW QUESTIONS .................................................................. 153
APPENDIX B: BUSINESS OPPORTUNITY ............................................................... 156
APPENDIX C: FMEA AND DMFA .............................................................................. 157
APPENDIX D: CALCULATIONS ................................................................................ 174
APPENDIX E: REFERENCES .................................................................................... 186
1.0 Introduction
The current climate of energy insecurity in the United States and throughout the world offers a
significant engineering challenge to develop more efficient vehicles that reduce the dependence
on petroleum based fuels. A major aspect of engineering involves working to solve humanity’s
problems with the limited available resources. Recently there has been growing concern with the
environmental impact of the use of fossil fuels as the dominant source of energy, with concerns
about global warming, increased CO2 levels, other types of air pollution and the impact of
drilling and mining for the fuels. Petroleum fuels provide the majority of the energy used for
transportation in the United States and there is growing concern pertaining to when worldwide
oil production may peak. The United States oil production capability peaked in the late 1970’s
and the worlds oil fields are expected to reach maximum production between 2008 and 2020
(EIA, Long Term Oil Supply Scenarios). Yet there is a growing demand for petroleum based
fuels within the United States and throughout the world. This presents an enormous challenge
and opportunity for engineers today and well into the future.
The United States Department of Energy stated in its 2006 Strategic Plan that the United States’
energy infrastructure is not keeping pace with the growth in energy demand, thereby endangering
the reliability of the energy system. Energy diversity is essential for America’s energy security
and economic prosperity. In 2004, America imported 65 percent of the crude oil it used
domestically. By 2030, the Energy Information Administration forecasts that crude oil imports
will rise to 75 percent of our total crude oil supply. America’s energy security and economic
well-being are challenged when the United States is dependent upon other countries for the fuels
that account for over 60 percent of the nation’s current energy use. This is especially true in the
case of the transportation sector, which is the least energy-diverse sector of the American
economy with petroleum accounting for more than 95 percent of the fuel consumed. (DOE, 2006
Strategic Plan) This proves that there is a current need and there will be future demands for
products that utilize more energy diverse solutions to answer the needs of transportation.
The United States is a society that is constantly on the move and the major portion of the
transportation used for everyday travels is provided by cars and light trucks. “About twentyeight percent of the energy used in America goes to the transporting of people and goods. There
are over 222 million vehicles in the United States, whose total population is just under 300
million. Automobiles, motorcycles, trucks, and buses drove over 2.8 trillion miles in
2002.”(EIA, Energy facts)
Cars require large amounts of torque in order to quickly accelerate the large mass of the vehicles.
In recent years personal vehicles have gotten larger and heavier, leading to a decrease in fuel
economy and an increased impact on the environment. A majority of the traveling done in
personal vehicles are for trips under five miles with only one or two passengers.
The Department of Energy’s Strategic Plan for 2006 states that the consumption of fossil fuels
for electricity generation and transportation accounts for three-fourths of the carbon dioxide
emissions in the United States and is a major contributor of air, water, and land pollution. Most
energy intensive products (e.g., power plants, automobiles, etc.) have high capital costs and low
turnover rates. The lifetime of the average automobile is 10-20 years, so a conventional
automobile sold today will still be consuming petroleum in 2020 at about 25 miles per gallon.
The energy economy, therefore, changes slowly and new technologies receive a cautious
reception from consumers because they represent large financial investments that must operate
effectively over decades. Fuel prices will affect the rate at which many new energy-related
technologies penetrate target markets. When fuel prices are high, typically large-scale market
penetration occurs sooner than when fuel prices are lower. (DOE, 2006 Strategic Plan)
The college campus environments offer an excellent opportunity to address and implement more
effective forms of transportation. There are many faculty, staff and students at universities
around the world whose need for vehicles which travel short distances efficiently offer an
excellent business opportunity for our group. College campuses produce an abundance of stop
and go traffic that is not efficient or environmentally friendly for large personal vehicles.
Parking is an issue at most college campuses and is a cause of much frustration. Smaller more
efficient vehicles would be useful at alleviating some of this parking pressure and environmental
concerns. Universities around the world are currently looking for more energy appropriate,
environmentally friendly vehicles and there is a need to explore alternative forms of
transportation.
1.1 Initial Needs Statement
There is a need for a compact 2-passenger vehicle powered by alternative energy that will be
marketable for intra-campus and intra-community travel. The vehicle must address the problems
of pollution, oil dependency, oil consumption, parking, and money spent on energy. It must be
high-quality, safe, aesthetically appealing, weatherproof, reliable, and capable of being used all
year.
2.0 Customer Needs Assessment
The customer and their corresponding needs were identified through a series of observations,
surveys, and interviews. Collectively the team concluded that the three largest customers are
public institutions, intra-city travelers (persons traveling less than ten miles per day), and
members of small communities (such as retirement homes). Our surveys and interview questions
were created to extract useful information from the three target customers. The interview
questions for Ohio University’s Director of Transportation were created to focus around
problems with their current vehicles and transportation system. Both surveys are included in
Appendix A. Initially, a total of 58 surveys were completed, including 8 faculty members, 48
students, and 2 retirement community members. Observations of parking congestion and the
number of people riding in a vehicle were conducted at multiple locations around Athens. A
total of 196 observations have been made. The results of the first round of surveys and
observations clearly identify general customer requirements as seen in Table 1.
Table 1: Identification of Initial Customer Needs
Reliable
Safe
Heating/AC
Weather protection
Quiet operation
Ability to travel up hills
Low maintenance
Cargo area for 100lbs. or 7 bags of groceries
Aesthetically pleasing
Speed of 25mph
Fuel efficiency better than current vehicles
Ability to operate in all seasons
Must operate in all road conditions
Cost less than $7000
Turn signals
Radio
Simple operation
Passenger seat
Speedometer
Odometer
Good battery life
2.1 Weighting of Customer Needs
When trying to produce a product, meeting all customers’ needs is a goal, however this goal is
often infeasible. This is where engineers are critical. Some needs are more important to meet
than others and weighting is necessary in order to properly choose between needs. The
analytical hierarchy process (AHP) is a process used in industry to determine a ‘common
denominator’ between different sets of options. We sorted each topic into general categories
such as durability, capacities and consumer appeal and weighted them against each other in order
to determine their weighted comparison. The three topics were selected and were evaluated
between each other in Table 2. The results were put into Table 3 to show the overall weight
factors of each topic.
Table 2: AHP pair wise comparison breakdown to determine weighting
5
4
3
2
1
2
3
4
5
Consumer
Capabilities
X
Appeal
Consumer
Durability
X
Appeal
Durability
Capabilities
X
Table 3: AHP comparison chart to determine weighting for main objective categories
Consumer
Durability Capability Total Weighting
Appeal
Consumer Appeal
1.00
0.25
0.33
1.58
0.12
Durability
4.00
1.00
2.00
7.00
0.54
Capability
3.00
0.50
1.00
4.50
0.34
The results hierarchy of customer needs can be found in Table 4, which was created using the
AHP process. Durability was found to be the most important trait with a weighting factor of
0.54. Durability received the highest weight due to the customer need for a vehicle that requires
little maintenance or care and can be reliable for the user. Capability and consumer appeal
received lesser weighting factors of 0.34 and 0.12, respectively. While capability and consumer
appeal appear insignificant compared to durability, they will be significant contributing factors to
be considered in the conceptual design process. Table 4 offers the weighted hieratical customer
needs that have been compiled thus far.
Table 4: Weighted hierarchal customer needs list obtained from interviews
and group discussions
1. Consumer Appeal (0.12)
1.1 Heating
F.1 Output
F.2 Temperature Range
1.2 Air Conditioning
F.3 Output
F.4 Temperature Range
1.3 Quiet operation
1.4 Smooth ride
1.5 Simple operation
1.6 Gauges
1.7 Cost
1.8 Ergonomics
2. Capabilities (0.34)
2.1 Range
2.2 Speed
2.3 Cargo Area
F.5 Volume
F.6 Weight Capacity
2.4 Fuel Efficiency
2.5 Ability to carry passengers
F.7 Volume
F.8 Weight Capacity
2.6 Ability to travel up hills
2.7 Ability to operate in all seasons
2.8 Operation on all road conditions
3. Durability (0.54)
3.1 Reliable
3.2 Safety
3.3 Weather protection
3.4 Low maintenance
3.0 Revised Needs Statement and Target Specifications
There is a need for a safe, reliable, compact vehicle powered by alternative energy that will be
marketable for intra-campus and intra-community travel (and therefore have sufficient weather
protected and secure storage space). The vehicle must address the problems of pollution,
petroleum consumption, parking, and operating costs. It must be high quality, aesthetically
appealing and provide 4-season weather protection and performance capability (for most
locations within the continental US).
The target specifications for the vehicle are as follows:
Braking
25mph – 0
30 feet
Based on average stopping distance for an average automobile traveling at
25 mph was found to be 30 ft. Using the equation
With a velocity of 25 mph and a coefficient of friction of .7 between the tires and
the road.
Cornering Stability
25 Feet for
a Speed of
15mph
An experiment was preformed with a golf cart that has the same basic
dimensions as the target specification.
Range
30 miles
Based on customer interviews which indicated many persons make several trips
under 5 miles each week, also based on independent testing of 10 NEVs
conducted by the US Department of Energy. Average range for NEVs tested was
36.7 miles.
Gradeability
15%
Based on information found on a biking website indicating the steepest hills in
Athens do not exceed 25% grade, and few exceed 15%. Also, ODOT roadway
engineering standards state that any road with a speed limit of 25 mph is to be
designed to avoid grades greater than 15%.
Max speed
25 mph
In order to be classified as a Low Speed Vehicle, the vehicle must not be capable
of speeds greater than 25 mph.
Acceleration
0-20 mph
8 sec
Based on independent testing of 10 NEVs conducted by the US
Department of Energy. Average acceleration time from 0 to 20
mph was 8.7 seconds.
Parking
4ft. x 8ft.
This would allow the vehicle to fit into a compact parking space of 7.5 feet by 15
feet. This is also based on an average NEV size of about 4 feet by 8 feet. This
would also allow two 95th percentile males (females) to be seated side-by-side
since they are less than 35 inches (32 inches) wide.
Four Season Capability
0o – 105o F
The vehicle must have basic operability within this temperature range. This is
defined as being able to operate with minimal impact on passenger comfort and
driver visibility along with limited effects on energy storage and drive system for
the vehicle. This is based on average temperatures for more than 10 US cities in
all regions.
Visibility
Range of
Sight for
Driver
Vehicle cabin must be designed as to allow a clear line for sight for
the driver with limited obstructions caused by the frame of the vehicle.
Weather Protection
Full Encl.
Vehicle cabin must be fully enclosed by waterproof panels that offer protection
from weather to the passengers. Minimize leakage from elements into the cabin,
and close gaps in panels to seal from leakage. This is based on vehicles from
benchmarking research, NEVs, and customer preference.
Interior Temperature/Comfort/Climate Control (Winter)
Minimum
The vehicle shall comply with NEV America’s standards that ensure the
65°F at 32°F vehicle heating system is capable of maintaining interior temperatures
Exterior
of at least 65°F at an ambient temperature of 32°F. (NEV America)
Temp
Time to Reach Steady State Temperature
SS Temp.
The vehicle should reach a temperature of 65°F at 32°F exterior temperature
in 10 min.
within ten minutes of starting the heater.
Interior Temperature/Comfort/Climate Control (Summer)
Maximum
The vehicle shall have sufficient ventilation, shaded windshield/windows,
90°F at 100°F and other cooling measures to keep passengers comfortable in high
Exterior
temperature environments.
Temp
Ventilation
75 cubic
Feet per
Minute
The vehicle needs to have a ventilation system that is able to completely
add fresh outside air every half hour. The flow rate should also be
adjustable.
Energy/Fuel
Charge Time Based on independent testing of 10 NEVs conducted by the U.S.
T < 10 hours Department of Energy, where the average charging time(slow charge) was 9
hours.
Vehicle Weight
<1200 lbs.
Based on various electric utility vehicles and NEVs and includes full enclosure.
Cargo
50-100 lbs.
Based on the load capacity and volume of cargo area for various electric 11 cu. ft
utility vehicles and NEVs.
Ground Clearance
>5 inches
Vehicles should have a ground clearance of at least five (5) inches to all sprung
and un-sprung portions of the vehicle, with the vehicle loaded with rated payload.
(NEV America)
Safety
Passenger
Safety
The vehicle should meet the latest requirements set by the
National Highway Traffic Safety Administration for NEV’s. The requirements
include a safety glass windshield, wipers, headlights, taillights, turn signals, high
mounted stoplights, mirrors, and a three-point safety-belt.
4.0 External Search
Through research and the information that resulted, our team determined that the best response to
current dependence on petroleum would be the use of electric drive trains and hybrid systems in
short range commuter automobiles. It is for this reason that the external search for related topics
and systems mostly consisted of searching for electric powered vehicles and the regulations and
patents that apply to them. Many of these vehicles were designed to be operated on roadways as
low speed or neighborhood vehicles while others were designed for use in gated and other
planned communities.
During the search for applicable patents, the following were found to be most relevant to electric
powered vehicles. Patent #6631775 describes an electric vehicle’s chassis with a compartment
for a removable battery module. The patent describes the decreased weight and increased range
that could be attained through the use of a removable battery pack. Facilities similar to service
stations that store, charge, and exchange battery packs are also described by this patent.
Removable battery packs and charging stations could significantly increase the range and the
ease of operation of the project vehicle.
Patent #7116065 deals with an alternative energy system control method and apparatus. The
patent describes an energy control system that can control and regulate multiple variables found
in an energy system. This type of control system could be very helpful in regulating and
controlling an electric motor in the project vehicle.
Patent#7117044 is mainly concerned with the design of an electric vehicle with separate electric
motors driving each wheel. The system described by the patent controls each wheel separately.
In the presence of a turn, this system would be able to slow one wheel while accelerating the
opposing drive wheel. The system would then be able to return each wheel to the same speed
once the vehicle has exited the turn and returned to a straightaway. This type of system could be
very beneficial by allowing the rear wheels of the project vehicle two operate at different speeds
and accelerations. This system would reduce the amount of tire wear that is caused by cornering
with a solid rear axle. It would also allow the project vehicle to have a tighter turning radius.
Rules and Regulations:
Federal Rules and Regulations:
Since the needs statement requires a compact two passenger vehicle that will be marketable for
intra-campus and intra-community travel, it will most likely be a three or four wheeled slow
moving vehicle. The rules and regulations vary significantly between motorcycles, motor
scooters, and low speed vehicle classifications. The vehicle will most likely have three or four
wheels; vehicles with three or less wheels require motorcycle endorsed licenses and insurance in
many states.
The National Highway Traffic Safety Administration (NHTSA) outlines the minimum
requirements for four wheeled low speed vehicles in the Federal Motor Vehicle Safety Standards
(FMVSS) § 571.500 Standard No. 500 and in the 49 CFR Part 571 ruling on low speed vehicles.
The vehicle will have to meet each of these standards.
NHTSA Rules and Requirements for slow moving vehicles
•
The vehicle must not be capable of exceeding 25 miles per hour in the distance of 1 mile
on a paved level surface.
•
The vehicle must be equipped with headlights, tail lights, front and rear turn signal lights,
and reflex reflectors.
•
The vehicle must have either a AS-1 or AS-5 glazed windshield.
•
The vehicle must have exterior one driver’s side exterior mounted mirror and either one
interior rearview mirror or one external mirror mounted on the passenger side.
•
The vehicle must be equipped with a parking brake, windshield, and a Type 1 or 2 seat
belt.
•
The vehicle must have a VIN number.
State Rules and Regulations:
Since it is also likely that our vehicle will be marketed and sold in many different states, it must
meet each states specific rules and regulations for vehicles. All vehicles in any state must follow
all of the NHTSA rules and regulations as well as all state sanctioned requirements.
4.1 Benchmarking
The recent dramatic increase in oil prices worldwide commenced a dramatic increase in
development and production of alternative energy vehicles. Some of these vehicles have been in
regular production and have attained popularity throughout Europe. Others, such as the
Neighborhood Electric Vehicles (NEVs), have recently been developed in the US as a native
response to the energy issue. All the while, human powered vehicles have been developed for
mass production and constructed in garages for over a century.
Neighborhood Electric Vehicles are currently in production by more than 16 manufacturers
worldwide. Generally, NEVs are limited to a top speed of 25 mph in order to be classified as a
low speed vehicle (LSV), and may not be operated on roadways with a speed limit exceeding 35
mph. Federal legislation has been passed along with supporting legislation in 44 states dictating
low speed vehicle operation.
Three wheel electric vehicles have been produced in relatively high numbers in Europe during
recent years. Many of the European manufacturer’s have recently created models for the US
market as the demand has dramatically increased in North America. One particular advantage
these vehicles may have over NEVs is the category of vehicle for registration purposes. Most 3
wheel electric vehicles can be registered as 3 wheel motorcycles, which means that some of the
laws that govern NEV use do not apply and some 3 wheel vehicles may even be registered as a
moped, which have even fewer restrictions when compared to four wheel vehicles. Table 5
introduces six vehicles that were benchmarked for ideas and use of comparison to the target
specification for the vehicle.
Table 5: Benchmarking of Products
Feature
Cost
Speed
Capacity
Range
All
Weather
All
Season
Misc.
Neighborhood
Electric
Vehicles
GEM eS
3 Wheel
Electric
Vehicles
Twike
Human
Powered
Vehicles
Aerorider
$6,000 +
25 mph
2-6
20-70 mi
$7,995
25 mph
2
30 mi
$5,000 +
20-70 mph
1-2
20-80 mi
$26,000
53 mph
2
80 mi
$200 +
<30 mph
1-2
unltd
$7,000
<30 mph
1
unltd
Many
Yes
Many
Yes
Few
Yes
Few
No
None
No
Very Few
No
16+
manufacturers
690 lb
payload
Reg. as
Motorcycle
Human
Power Assist
100's of
Models
elect
assist
Figure1: GEM eS
Figure 2: Twike
Figure 3: Aerorider
Research found numerous vehicles that fulfill the requirements for energy efficiency and are
alternatively fueled but fail to address all of the comfort and utility needs of college students.
Therefore, it is our intention that a power train, and other components necessary for operation,
could be easily integrated to our design or an existing model could be adapted to implement our
design. While similar vehicles addressing the energy situation are available, students are not
buying them because they only address the energy issue and overlook the other essential
elements. Our plan is to develop a vehicle that is appealing to college students by focusing on
key elements and features. The scope of the project includes the body, frame, and comfort/utility
features. Our team selected this scope based on research of similar products and customer input.
From our surveys it was determined that college students want a level of protection from rain and
snow that is equivalent to a traditional car. While many current alternatively fueled vehicles
have the level of weather protection desired by college students, they are plagued with problems
consisting of: poor ventilation, inadequate protection of cargo, and little to no defrosting
capability. Our team plans to incorporate weather protection into our vehicle that addresses
these problems. Utility of the vehicle is also important to college students. Even though
students want an energy efficient vehicle, they are not willing to sacrifice the ability to carry
cargo or an additional passenger. It is our intention to balance the needs for energy efficiency
and utility by designing the vehicle with the capability to carry a passenger and cargo while
making the vehicle as energy efficient as possible. Aesthetics of the vehicle is a concern that
consistently appeared on the student surveys and is something we plan to address by continually
consulting the customer during the design process. There are also a number of smaller features
that students desired in the vehicle which we plan to include, such as 12 volt outlets, radio, and
cup holders.
5.0 Concept Generation
5.1 Problem Clarification
Power flow models are used to represent cause and effect in a given system and are very useful
in clearly defining a problem. These models can be of simple generic systems such as seen in
Figure 4 or it can be expanded as seen in Figure 5. The two figures are models of systems that
use power in vehicles. The first figure gives a very general diagram of the flow of power within
the system. The second figure breaks down the power requirements in a vehicle. The input is
the power to the system, this power is then used for either the drive train or other auxiliary power
requirements, and these two systems output work with the power. There are internal and
external power requirements in the drive train and there are essential and non-essential power
requirements. Using both Figures 4 and 5 we were able to better understand what the power
requirements for this vehicle and both figures were used when discussing the scope and
feasibility of the project.
Input Power
Power Loads
Figure 4: Power Flow Model
Output Power
(Work)
Power
Source
Drive Train
External Power
Losses
Internal Power
Losses
Air Resistance,
Rolling Friction,
Static Friction,
Passenger Weight,
Vehicle Weight,
Cargo Weight,
Temperature,
Environment
Friction within Drive
Train, Power
Conversion,
Temperature, Motor
Efficiency
Auxiliary
Power
Requirements
Non-Essential
Essential
Radio, Defroster,
Heater, 12 Volt DC
Socket, Clock,
Interior Lighting
Gages, Turn Signals,
Lights, Window
Wipers
Figure 5: Expanded Power Flow Model
5.2 Concept Generation
The purpose of this section is to show the process by which ideas and concepts were created with
creativity. It was decided that the best way to start the concept designing was to brainstorm or
sketch any and all ideas that were thought of for the project. Meetings were set up to come
together as a group and pick out the best and most important features that can distinguish the
design from others currently on the market. Some of these features included trying to make
unique opening doors and possibly a LCD screen in the steering wheel. It also included other
features such as power sources, window wipers, and mirrors to make sure to include features that
cannot be forgotten. Figure 6 shows some of the brainstorming lists and Figures 7, 8, and 9 show
more detailed brainstorming.
Utility Bed
Trunk
Side-by-side
Tandem
Cargo Rack
Cargo
Box
2
2 or more
Utility
GEM
Vehicles
Passenger
ATV
Golf Cart
4-Wheel
Automobile
Tracks
3-Wheel
E
Power
Source
Electric/Human
Electric
Bio-diesel
Electric/Ethanol
Single
Source
Hybrid
Electric/Bio-diesel
Figure 6: Spider diagram show first brainstorming format branching from the EPCT to
specific ideas
Roof
1 Person
Glove
Center
Console
Cargo/Storage
Adjustable
Capacity
Utility
Seating
2 People
Foldable or
Removable
Seats
Washable
Floor Mats
Hitch
Sport Utility
Truck
Armor
Plating
Removable/Replaceable
Body Panels
Collapsible
Frame
Bumpers
Figure 7: Detailed Ideas for Utility on the Vehicle
Adjustable Fan
Manually
Operated
Windows
Waterproof
Materials
Removable
Rear Cap/Roof
Removable
Doors
Windshield
Wipers
Spring/Fall
A/C
Summer
Four-Season
Necessities
Winter
Defrost
Heater
Battery
Insulation
Heated
Mirrors/Windows
Hard Top/Doors
Figure 8: Detailed Brainstorming for Four Season Designs
Hands-Free
Phone
Capability
Cup
Holders
Appropriat
e Gauges
12 Volt DC
Socket
Digital
Stereo
MP3
Interior
Lighting
Ash Tray
Cigarette
Lighter
Tray Table
Interior
Suicide
Doors
Scisso
r
Security
System
Appealing
Features
Power
Steerin
Sliding
Doors
Amplifier
Body Style
Bubble Shape
Sport
Utility
Joystick
Operation
Mini-van
Transparen
t Body
Wheel
Spinners
Figure 9: Detailed Ideas for Features
Sunroof
After brainstorming and coming up with the spider diagrams above, most of the ideas could be
configured into the concept designs. The designs try to incorporate scissor doors into a design,
or a heater for the four season protection. These are some of the things that were taken from the
brainstorming and put into the concept designs. Figure 10 and 11 show sketches that were
presented during the group’s discussion on concepts. They started out simple, but after meeting
and deciding what to continue on ideas were improved or dropped from the list. For example,
tandem seating was an idea that was presented and used in other concepts until we decided that
side-by-side seating would be more appropriate and more feasible to meet our goals. Figure 11
shows how we first came up with the removable back and doors idea, after continuing our
designs, we felt that having a removable seat would be a better idea for the vehicle.
Figure 10: Sketches created from our first features list to be analyzed and improved for the
next evaluation
Figure 11: Updated sketches created after the first evaluation and decided as a good
concept to update and continue creating from the design
Main Characteristics
Main configurations are being thought up at this time. Some being considered are comfort,
appeal and chassis style.
ƒ Comfort A comfort for the design could be as simple a comfortable seating to appeal
more to the customer. It could also lead up adjustable heating and cooling systems.
ƒ Appeal Appealing to the customer is a big part of the focus on this design. Some of the
ideas for appeal included a LCD screen in the wheel for displaying a variety of screens.
ƒ Chassis style There is a possibility to look into the best style of frames for this design.
There is a need to make sure to choose a style that is both feasible and effective. It
needs to be strong and reliable to ensure the safety of the driver and passenger. The
three basic categories that have been chosen are light-weight, medium-weight, and
heavy-weight frames. There will be research done for each category in order to make
sure the most appropriate frame is picked. Making sure that the best frame is chosen
will help the design come along tremendously.
Subsystems
Some of the subsystems are weather protection and cargo area that will capture customers when
they see the design.
Weather Protection
It is strongly believed that weather protection from the elements would be a strongpoint to have
in the product. This is off of surveys with nearly every interviewer wanting some kind of
protection from weather, such as protection from rain, light snow, and cold weather. Some of the
ideas that have come up include; permanent closure, removable panels/roof, heating and cooling
systems, hard top coverage, or soft top coverage. Choosing the most feasible and effective ideas
from this list will help make sure that the design will provide the best weather protection. Some
of the ideas developed so far are shown in the Figures 12 and 13 below.
ƒ Permanent closure: As it sounds, a permanent closure would incorporate a system that
had full enclosure from the environment that could not be removed. It would provide
protection from all weather, which means it would be necessary for the material to
withstand any harsh conditions such as hail or snow that could cause damage. To make
sure the vehicle was lightweight; it should use a light material such as fiberglass or
plastic. In Figure 12 it is seen that this design incorporates the permanent closure of the
sides and roof.
Figure 12: Concept design incorporating permanent closure from weather elements
ƒ Removable panels/roof: Some of the designs so far have incorporated removable
panels and roof. This could be a comfort to the customer in the summer during hot
days or appeal to a customer that likes convertible style cars. The removable panels or
roof would address the issue of cooling the vehicle during hot weather by letting free
flowing air act as a fan or AC system. A problem with the removable panels or roof is
the issue of security and whether the vehicle can still be secure if the material used can
be torn or cut. Some of the materials that have come to mind are a clear plastic for
windows, which could be punctured easily by elements around the vehicle.
ƒ Heating and cooling systems: In order to meet the four season capability, heating and
possibly cooling systems are going to be needed. It could range from simple fans for
air to pass through the car, or a heater to heat the inside compartment during the winter.
ƒ Hard top or soft top: Like most jeeps, a hard top or soft top could be design to fit the
transporter. This could go with the removable roof option or be a system that could
help with the weather coverage and cooling system.
Steering Wheel
One novel design idea was to incorporate a LCD screen into the center of the steering wheel.
This would function as a multiuse display replacing some of the dashboard gages. The screen
would be able to display the current speed, trip distance, total distance traveled in the vehicle, the
fuel or battery life gage, and the radio. As seen in Figure 13 this feature would be unique and
free up space in the dashboard to allow for extra storage or leg room.
Figure 13: Concept drawing incorporating a LCD screen into the steering wheel
Cargo Area
Trying to make sure that the customer can put a good amount of cargo or supplies to transport is
a main focus. It would also be great to be able to hold a heavy amount of cargo. Some ideas for
the cargo discuss whether to have it be removable or permanent, or having a foldable seat that
can turn into the cargo area.
ƒ Removable cargo area: This concept would be an area at the back of the transporter
that would hold all cargo desired by the customer, but if it was not needed for every
trip; it could be removed in order to take some weight off of the transporter to improve
the performance. It would have the functionality for the customer to move the cargo
box with items in it to a desired area. A concept drawing of a removable cargo area in
show in Figure 14 below.
Figure 14: Concept drawing incorporating a cargo area in the rear of the vehicle, cargo
area could possibly be removed
ƒ Foldable seat/cargo area: This would help keep the cargo inside the transporter and
protect it from weather. By incorporating a foldable seat you could switch between
having a second passenger and being able to hold items. The seat could also be
removable to get a complete area for the cargo.
ƒ Roof rack: A simple roof rack could be feasible and helpful to the customer with
materials that were too big or bulky to fit in the cargo area. This would provide even
more space for cargo and be capable to handle unusual items. For example, it would
appeal to students that like to ski, wakeboard, or just need a roof rack to transport
materials.
As mentioned before, one of our “delighter” features could be the LCD screen found in the
steering wheel. This would not be like a TV to watch while driving, but more of a multiple
screen dashboard. It would be able to switch from showing the speed at which one was driving,
to showing the power level left in the vehicle. We want to improve the design even more by
improving the capabilities of the readouts to as many important features that a driver would
want. Overall, the concept design deals with coming up with ideas, bringing them to the table,
getting feedback from team members and customers, and then improve the concept with new
innovative ideas
6.0 Concept Selection
6.1 Data and Calculations for Feasibility and Effectiveness Analysis
Power Calculations
The power needed for the vehicle can be calculated for three different situations to estimate the
maximum power needs for the vehicle. These three different situations are acceleration,
climbing a given slope, and the power needed to maintain the maximum velocity. There are
three different forces that act in resistance to the vehicle as it is moving. These are rolling or
kinetic friction, the air friction caused by the drag of the vehicle, and the resistance caused by a
slope such as a hill. In Table 6 the variables and constants what were used in the calculations are
presented.
Table 6: Variables and Constants used for power calculations
Variables
Units
Justification
Diameter of Wheel
(D)
Maximum Velocity
(V)
12 Inches
25MPH = 36.7
Feet/Second
Size of standard golf carts and NEV wheels
Frontal Area (Af)
Coefficient of Drag
(Cd)
Coefficient of
Rolling Friction (Cr)
Total Weight (W)
Gravity (g)
16Feet^2
0.75
0.02
1600 Pounds
32.2
Feet/Second^2
2.38 x 10^ -3
Slugs/Feet^3
Density of Air (ρ)
Coefficient of friction
for decelerating ( μ ) .7
Maximum speed allowed for NEVs
Rough conservative estimate, based on benchmarked
vehicles
Very conservative estimate
Conservative estimate of friction between rubber and
concrete
Rough conservative estimate, based on weight of two
passengers and weight of benchmarked vehicles
Calculated by Sir Isaac Newton in Philosophiae
Naturalis Principia Mathematica
Density of air at sea level
Based on the friction on a dry concrete road
The first calculation that was made was the calculation of the amount of power that is required to
sustain the vehicle at maximum speed on a level surface. The drag friction caused by the vehicle
at 25 mph is calculated using the equation
Fd = 1 / 2 * ρ * V 2 * Af * Cd
Eq. 1
and is calculated to be 19.2 pounds. The resistance force caused by friction is calculated using
equation 2 as follows
Fr = Cr * W
Eq. 2
The rolling friction was calculated to be 32 pounds, this value is greater then the drag force due
to the weight of the cart and the minimal frontal area of our cart. Since there is no slope in this
calculation the total force (Equation 3) the vehicle needs to over come is 51.2 lb.
Fe=Fd+Fr
Eq. 3
The power (Equation 4) needed to propel the vehicle at 25 mph is 1879 foot pounds per second.
This is 3.42 gross horsepower which does not consider for losses in the drive train.
Pe = Fe * V
Eq. 4
The second power calculation to be made is the power that is required to accelerate the vehicle
on a level road from 0mph to 20 mph in 8 seconds. Equation 8 was used to calculate the power
needed however this does not take into account the fact that the power required changes for
different velocities.
1 W
2
* *V
E 2 g
Pe = =
t
t
Eq. 5
The power for acceleration was calculated to be 4.86 horsepower, however the vehicle will need
to allow for a greater horsepower as this is not the horsepower that will be truly needed to propel
the vehicle from 0-20mph in 8 seconds.
The final power calculation is the calculation of the amount of power required to propel the
vehicle up a given slope. Cable Lane and Terrace Drive are two hills located in Athens were
chosen as potential test hills for the final vehicle.
Distance
.2 miles
Average Grade
14 %
Maximum Grade
24 %
Elevation Gain
153 ft.
Base Elevation
673 ft.
Peak Elevation
826 ft.
Figure 15: “Terrible” Terrace Drive Profile and Statistics
Distance
Average Grade
Maximum Grade
.75 miles
7%
21 %
Elevation Gain
296 ft.
Base Elevation
647 ft.
Peak Elevation
943 ft.
Figure 16: Cable Lane Profile and Statistics
The power needed for grades of 5% and 15% at 15mph and 5mph respectively was calculated
using the following equation:
∑ Fs = W * (
% slope
)
100
Eq. 6
This force was added to the forces in Equation 3 and the total resistive force was calculated to be
118lb and 272.75lb respectively. The power for a grade of 5% and a speed of 15mph was
calculated to be just over 4.75 horsepower and the power required for a grade of 15% and 5mph
was calculated to be 3.64hp.
Given these power calculations our vehicle will require a motor that can output over 5hp to meet
the target specifications and allow for any potential losses in the drive train. There are currently
a wide variety of relatively in expensive motors on the market that can supply this amount of
power.
The maximum amount of torque at the wheels required for acceleration and climbing hills is
334.125 foot*lbs and 136 foot*lbs respectively. These values were calculated using Equation 7
and do not take into account a gear box which would reduce the amount of torque requirements
for the motor.
τ =F*
D
2
Eq. 7
Braking calculations
The amount of force that will need to be applied to the wheels to allow for controlled braking
was calculated for two different situations. The first calculations are for rapid deceleration on
level ground and the second set calculations are for braking on a slope.
Rapid braking on level ground without sliding can be calculated by first calculating the rate of
deceleration that the vehicle undergoes using Equation 8.
∑ Fx = m * a(max) − W * μ
Eq. 8
Assuming that the net force is zero the maximum deceleration the vehicle can undergo is -22.54
ft/s² from a speed of 25mph. The stopping distance for the vehicle for this type of deceleration is
30 feet and was calculated using Equation 9.
Vf
2
2
= Vi + 2 * a (max) * Δx
Eq. 9
Using Equation 10 the amount of time that is required for rapid deceleration is 1.63 seconds,
which is quite allowable in real world circumstances.
Eq. 10
The amount of torque that must be applied to each axle on level ground is calculated to be 280
foot*lbs using the equations for torque and the frictional force ( Ff ).
Ff =
W
*μ
2
Eq. 11
The stopping distance needed for deceleration on a grade of 15% was calculated to be 47 feet
using Equations 10 and 12.
∑ Fx = m * a(max) − W * sin(θ ) * μ − W * cos(θ )
Eq. 12
The required torque that needs to be applied to each axle for stopping the vehicle on a 15% slope
was calculated to be 166 foot*lbs.
The required braking torque for the vehicle is feasible to construct based on market research and
can be done so with brakes currently available on the market.
Energy Calculations
The target specifications for the vehicle require that it be able to complete a 30-mile trip without
recharging. To make energy calculation for the vehicle we planned a route from the Ohio
University’s Stocker Center to Kroger’s on East State Street. This type of trip represents the
type of trips that the vehicle will undergo on a daily basis on college campuses around the
worlds. The trip there and back was 8.25 miles and consisted of 18 accelerations and
decelerations. The road was approximately 75% level or down hill and 25% of the trip was on a
grade of 5%. We also assumed that maximum speed would be required on level ground and a
speed of 15mph on the hills. Using Equation 10 we calculated to total amount of distance that
was spent for acceleration was 13000 ft out of the total 43 thousand feet traveled. Out of the
remaining distance 23000 ft was on level ground and 7600 ft was on a slope of 5%. Then using
these numbers and Equations 13, 14, and 15 the amount of the trip spent for each of the three
parts was calculated.
t (acceleration) = # (accelerations) * time
Eq. 13
t ( slope) =
d ( slope)
V ( slope)
Eq. 14
t (level ) =
d (level )
V (level )
Eq. 15
The time spent accelerating was 144 seconds, the time traveling up a 5% grade was 345 seconds
and the time spent on level ground at maximum speed was 626 seconds. Plus there is also all the
time spent idling while waiting at traffic lights and stop signs. Then using the power calculation
the amount of required energy for each was calculated using Equation 16.
Energy = Power * time
Eq. 16
The total energy required for the 8.25 mile trip was 2.25 million foot pounds which is .85
kilowatt-hours. For a 30 mile trip this would require 3 kilowatt-hours of energy. However this
does not account for any losses while idling or any other accessories that require power or any
losses in the drive train. The Columbia ParCar uses 6.25 kW-hours of energy for a maximum
range of 52 miles (AVT:ParCar, 2002). The GEM cart used 4.22kW-hours of energy for a
maximum distance of 42 miles (AVT:GEM, 2005). Given these two benchmarked vehicles
performances our vehicle is well within the average energy requirements for NEVs.
There are currently many types of batteries available that could possibly fulfill the power
requirements of an electric vehicle. Some of the most feasible options include deep cycle,
marine deep cycle, and electric golf cart batteries.
One of the most effective and versatile deep cycle batteries currently available is the Optima
Yellowtop. It offers excellent vibration resistance, a spill proof six cell arrangement that can be
mounted in any position. The Yellowtop has a long life and is maintenance free. The Yellowtop
line offers many sizes and power outputs. The Yellowtop is an absorbed glass mat or AGM type
battery, which is relatively expensive compared to other wet cell lead acid batteries (Optima
Batteries Tech Specifications).
Deka offers a deep cycle lead acid marine battery known as the Dominator. The Dominator is
completely sealed and spill proof. The Dominator offers a long life and requires little or no
maintenance. The Dominator line also offers many different sizes and power levels. The
Dominator is also a relatively expensive gel battery (Deka Dominator Product Specs).
Advance Auto Parts offers the AutoCraft line of deep cycle lead acid wet cell batteries. The
AutoCraft line offers a small selection of sizes and power output levels, but the AutoCraft
batteries are significantly less expensive than gel or AGM type batteries. The AutoCraft
batteries are flooeded wet cell and can only be mounted in an upright position. The AutoCraft
batteries are also not sealed and require some maintenance (AutoCraft Deep Cycle Marine
Battery Product Page).
There are many tradeoffs to consider in the matter of battery selection. One example would be
the advantages that gel and AGM type batteries offer over wet cell batteries. Gel and AGM
batteries offer more discharge and recharge cycles than wet cell batteries. Gel batteries also offer
increased discharge times over wet cell batteries. Gel and AGM batteries are also completely
sealed, can be mounted in many positions, and are maintenance free. Gel and AGM batteries do
have the drawback of being quite expensive (Carquest Batteries).
Cost, weight, and performance will undoubtedly be the factors most considered during the
battery selection process. Table 7 compares the three types of researched batteries and from this
data we are better able to determine some of the available battery sizes and weights.
Battery
Yellowtop
D34/78
Deka 8G24
AutoCraft
27DC2
Table 7: Comparision of Similar Batteries
Volts
Weight
Cost
Volume
(lbs.)
(in3)
43.5
$180-200
537.1
12
Reserve
Capacity
(min.)
120
52.5
53
$200
$80
724.5
791.0
12
12
132
175
6.2 Concept Screening
The vehicle frame, drive train, and miscellaneous features were evaluated as possible systems to
modify. The systems were evaluated based on effectiveness with respect to market impact and
manufacturing feasibility. The combination of effectiveness and manufacturing feasibility with
the highest rating which also impacted the energy situation would be chosen. Figure 17
demonstrates the different directions that marketing, impact and feasibility can take which is an
obstacle that engineers must work to balance in projects.
Figure 17: Feasibility vs. Market vs. Impact
It was determined that modifying the vehicle frame or body would have the greatest market
impact. Benchmarking shows that existing vehicles already have good mobility and make use of
energy saving features such as regenerative braking. By focusing on the body of the vehicle
rather then the whole of the vehicle the group will be better able to apply its energies where we
can make the most difference. Modification of the vehicle body and frame would allow it to be
tailored to the needs of college students and staff. Also with modifying the body and frame we
can focus on energy issues in that area. We can work to produce a more aerodynamic vehicle
that will reduce possible drag losses. Also the vehicle can be designed to allow for more cargo
area than current vehicles which will be beneficial for college students and faculty members who
need to carry different types of loads in the vehicle. We will be focusing on the material used for
the body structure in order to decrease the weight which will increase the energy efficiency of
the vehicle. By using materials that are light but strong we will able to dramatically reduce the
curb weight of the vehicle. By focusing on the body and frame of the vehicle we can better
improve possible problems that current vehicles have such as weather protection and cabin
safety. One of those areas that benchmarked vehicles have issues with was defrosting because
many of the current vehicles are marketed for retirement communities in the south where this is
not a big issue. The wide variety of possible changes allows for a range of manufacturing
feasibility. These changes can affect the energy situation as a side effect of increased
marketability.
Several rounds of concept screening are in the process of being performed. During each meeting
the individual concepts of each team member were evaluated based on manufacturing feasibility,
versatility, energy efficiency, consumer appeal, reliability, safety, and the “wow factor”. A
group consensus on whether each concept rated positively, negatively, or neutrally for each
criterion was reached as shown in Table 8 and Table 9. The nine initial designs will be included
in the next report to show the different concepts that were produced and to allow for better
understanding of the two tables.
Table 8: 1st Round Concept Screening
SELECTION
CRITERIA
Feasibility
Energy
Appropriate
User-Friendly
Ease of Mfg.
Reliability
Appealing
Versatility
Safety
Ryan
Michael
Kevin
Chase
Brandon
0
+
+
+
+
+
+
+
+
+
+
0
+
-
+
+
0
0
+
+
+
+
0
0
0
0
+
0
0
0
+
+
+
0
+
0
-
Damon
Camille
0
+
Jim
Table 9: 2nd Round Concept Screening
SELECTION
CRITERIA
Feasibility
Energy
Efficient
UserFriendly
Ease of Mfg.
Reliability
Appealing
Versatility
Safety
Wow Factor
NET
RANK
CONTINUE
Michael
Ryan
Kevin
Chase
Brandon
Damon
Camille
Jim
Brad
+
+
+
+
+
+
+
+
+
+
+
+
+
0
+
+
0
+
0
0
+
+
0
+
+
+
0
+
0
0
0
+
0
4
4
No
+
0
0
0
+
+
5
3
No
+
0
0
+
+
0
6
2
Yes
0
0
+
+
+
+
7
1
Yes
+
0
+
0
+
0
4
4
No
0
0
0
+
+
0
5
3
No
0
0
+
+
+
0
6
2
Yes
0
0
0
+
+
0
4
4
No
+
0
0
+
0
3
5
No
It was decided that no concepts would be eliminated during the first round because not all team
members were able to present an idea, and the group feedback could be used to improve
concepts for later screening. Ranking involved subtracting the total negative ratings from the
total positive ratings with respect to each concept.
The next step involved picking several templates for each of several design areas including the
body, seating arrangement, door style, and cargo type. The features which were determined to be
included by vote were side by side seating, scissor doors, a trunk which could be accessed from
within and outside the vehicle, and a body shape similar to Chase's drawing (Similar to Figure
12).
The team split into small groups to each create an overall concept based on the agreed upon
criteria. A general design would be selected based on the best concept. Fortunately, the concepts
appeared similar, resulting in the design shown in Figure 19 in section 6.3.
Future concept screening will consist of receiving feedback from customers on a currently
chosen design, making proposed changes to the group, and ranking the changes based on the
above criteria. This cycle will be repeated throughout the design process.
6.3 Concept Development, Scoring and Selection
From the three leading concepts, the best rated ideas in the areas of body style, door style, cargo
area, and seating arrangement were selected to be combined into a final concept. The rounded
front-end body was chosen for a stylish look and decreased drag. Scissor doors were determined
to be a unique alternative to regular or suicide doors. They do not increase the width of the
vehicle substantially when opened which can aid parking the vehicle in tight spaces. Since
parking was considered when developing specifications, it has been taken into account in
conceptual design. A trunk-style cargo area offered a larger space and greater versatility
compared to a cargo box separated from the passenger area. Side-by-side seating allowed the
transporter to have the best dimensions when considering possible parking issues. A wheel
design similar to that used on the Aerorider and Twike was also chosen for its uniqueness and
size. This type of wheel is large in diameter and small in width and is comparable to a bicycle
wheel. Small groups within the team used these ideas to form a final concept. This technique
produced results from each group with little variation. Differences were discussed until the
details of a final concept were determined.
The interior features that are included in the concept are determined from the functionality,
comfort, and appeal desired by customers. Customer feedback will be pursued until a satisfying
combination of features is created. An LCD touch-screen that displays useful data is the main
interior feature of the design. This serves as a replacement for most gauges and dashboard
components. A 12 volt DC socket, mp3 input, hands-free phone capability, cup-holders, and a
passenger tray table are some of the functional items that have been included. Foldable and
adjustable seating is incorporated into the design for comfort and versatility.
A
heating/defrosting system typical of an automobile but adapted for a small vehicle of this type is
implemented as defense against harsh weather. A ventilation system is also included. Safety
items required of NEVs such as window wipers, head/tail lights, turn signals, and brake lights are
also included.
Figure 18 is an example sketch of the final concept displaying some of the main exterior
features. Figure 19 is a preliminary model of the transporter produced with SolidEdge.
Figure 18: Sketch of final concept
Figure 19: SolidEdge model of final concept
In previous sections, target specifications were determined from customer requirements and
benchmarking and were presented in order to guide the conceptual design process. The final
concept will be justified with regard to the target specifications relevant to the scope of our
project. These are outer dimensions, cargo, visibility, four-season capability, weather protection,
climate control, ventilation, and safety.
Center of Gravity (CG)
To determine the turning stability of the vehicle and thus justify the general dimensions of the
transporter, the location of the center of gravity was calculated using standard methods. The
weights and dimensions of major components were researched and benchmarked. The locations
of these components were estimated based on scale drawings of the final concept. Figure 20
shows the CG location and the relative positions of the components and their respective centers
of mass.
4.8 ft.
Cargo
Passengers
CG
Batteries
Motor
2.5 ft.
Wheels/Tires
Controller
Wheels/Tires
Figure 20: Location of CG and major components of transporter
It must be noted that because the exact weight distribution of the frame is unknown these
calculations were performed assuming the frame had no mass. Assuming the mass of the frame
will be slightly heavier in the rear due to the cargo area and near the bottom, the actual CG will
be lower and farther towards the back of the transporter. The center of gravity was calculated as
being 2.5 feet above the ground assuming the vehicle was on 26 inch tires. The distance of the
CG from the front of the vehicle was determined as 4.8 feet.
Turning Stability
Turning stability can be calculated by considering the forces acting on the vehicle while turning.
There will be a horizontal force on the bottom of the wheel described by the following equation:
FH =
mV 2
r
Eq. 17
The mass of the vehicle is represented by m, the radius of the turn is r, and V is the velocity of
the vehicle.
As the vehicle turns, the resultant lifting force, FR, from the wheel through the CG is as follows:
FR = FH tan(θ )
tan(θ ) =
H
t
Eq. 18
Eq. 19
The t term is the half-tread distance and H is the height of the center of gravity of the vehicle.
The half-tread for a four-wheel vehicle is the distance from the center of gravity of the vehicle to
the outside of the wheel.
In order for a roll to be avoided, the resultant lifting force must not exceed the weight of the
vehicle. The following expression must hold:
⎛ mV 2
⎜⎜
⎝ r
⎞ ⎛H⎞
⎟⎟ ⋅ ⎜ ⎟ < w
⎠ ⎝ t ⎠
Eq. 20
The vehicle’s mass and weight are m and w, respectively. The inequality is satisfied assuming a
gross weight of 1900 lbs. (the specified vehicle weight plus passengers and cargo), a turn radius
of 25 feet, a speed of 15 mph, and a half-tread distance of 2 feet. This results in:
1428 < 1900
This outcome justifies the general dimensions of the vehicle as well as the turning stability
requirement.
Cargo Space
The cargo space of the transporter concept is larger than most vehicles on the market. This is to
accommodate a wide variety of shapes and sizes. This area is accessible from the rear through
an SUV-style hatch or from the passenger area which will be made easier by implementing
foldable seats.
Visibility
The vehicle concept has a large windshield and side windows to allow greater visibility and
prevent the driver’s line of sight from being obstructed by the frame or enclosure.
Weather Protection, Climate Control, Ventilation, and Four-Season Capability
The full enclosure of the vehicle will offer protection to the passengers, cargo, and propulsion
system from the sun, wind, rain, snow, and other forms of precipitation. A heating and
defrosting system will be used to maintain a comfortable temperature inside the vehicle during
winter months as well as defrost the windshield and windows. Ventilation will circulate air
inside the vehicle to help keep the passengers cool in warmer weather. Removable scissor doors
will also aid in air circulation. These features will provide comfort for the passengers in times of
inclement weather or fairly extreme temperatures.
Safety
As mentioned above, the vehicle will meet the latest requirements set by the National Highway
Traffic Safety Administration for NEV’s. The requirements include a safety glass windshield,
wipers, headlights, taillights, turn signals, high mounted stoplights, mirrors, and a three-point
safety-belt.
Concept Overview
The main features of the final concept are as follows:
ƒ Rounded front end body style with large windshield and side windows
ƒ Scissor doors
ƒ SUV-style access to cargo area
ƒ Side-by-side seating
ƒ Thin, large diameter wheels and tires similar to Twike and Aerorider
ƒ LCD touch screen displaying data on vehicle speed, battery level (if appropriate),
music selection, etc.
ƒ Heating/defrosting capability and interior ventilation
ƒ Foldable/adjustable seating
Customer Feedback
To verify the general appeal of some of the features chosen for the final concept, a collage of
pictures was created in order to collect more customer feedback prior to design refinement and
detailed design. These features are the shape of the body, scissor doors, steering wheel with
LCD screen, and wheels. Figure 21 is the collage used by the team.
Figure 21: Collage for Customer Feedback
7.0 Final Design
With refinement of the conceptual design many decisions need to be made and supported. In this
section there will be a discussion of the details of those decisions and an exploration of the
methods that were employed to make the decisions. The design was further modified and an
updated image of the proposed vehicle can be seen in Figure 22.
Figure 22: Exterior View of Proposed Vehicle
With the completion of the conceptual design it was decided that the team would focus its
resources and energies on developing and testing an enclosed body for the vehicle with focus on
the ability for the vehicle to function in all types of temperature conditions. This meant that a
heating system would be developed and tested to explore its feasibility and functionality in a
small alternative energy vehicle. From our customer feedback and benchmarking it was found
that most NEV style systems did not employ a heating system which leaves a potential business
opportunity open for the taking. In addition to the enclosure of the vehicle it was also
determined that the scissor doors from the conceptual design would be prototyped and tested for
functionality and feasibility. This was chosen based on research of the target market of college
age students who found the feature to be an exceptional feature that would set the proposed
vehicle apart for other vehicles that are on the market currently.
The design process for the vehicle required the division of The Goonies into 4 sub-groups made
up of the Body group, Mechanism group, the Interior group, and the Frame group to focus on the
four areas of investigation and development chosen by the team. The focus of the Body Task
Team was to select a material to be used for the exterior body of the vehicle and to investigate
the need for insulation in the vehicle to help reduce some of the heat loss in cold temperatures.
The body group would also be focusing on the shape and type of windows to be used in the
design. The mechanism group would be focusing on the production and testing of the hinges to
be employed for the scissor doors and the rear trunk hatch. The mechanism group would also
focus on the selection of a strut for the doors and hatch to enable the doors to be opened with
assistance from a mechanical device and to control the movement of the doors and hatch. The
interior group would be focusing on the climate control for the interior of the vehicle. They
would be prototyping the use of heating in the vehicle to decide the feasibility and safety of such
a system. They would also be focusing on the development of the dashboard and exploring the
different features that were being proposed for the dashboard. The seating and related safety
measure of seat belts would also be investigated. The selection of the batteries that would be
used for the heating system would also be a part of the interior group. The frame group was
reduced to allow members to help the other groups in their individual tasks since the frame is not
the main focus of testing for the vehicle. One member would be focusing on the door frame
design for the scissor door. The frame group would be deciding on the material and general
design to be used for the final design of the vehicle and exploring how the frame would be
affected by the decisions from the other three groups. The frame group’s decisions were to be
driven by the decisions of the other groups with a focus on the implementation of light weight
frame material into the construction of the vehicle.
Failure Modes and Effects Analysis (FMEA)
Failure modes and effects analysis is a design method that is employed by engineers to identify
problems and areas of concern within a system. The first step of the process is to list all potential
failure modes and then select the ones with the highest severity or probability of occurrence.
Then as a team a rating scale was established for severity and probability, after which the
potential failure modes were analyzed. The failure modes were compared and corrective actions
were decided upon to reduce the severity or probability of failure. Analysis was performed on
the corrective actions to determine what their impacts were. The list of FMEAs is then updated
and the process may be repeated. FMEA methodology was used to help organize the design
justifications and validations for the vehicle. The list of the possible failures that the team came
up with for the entire system can be seen in Table 10. Table 11 displays the focuses of each
individual group member.
Table 10: FMEA for Entire System
System
Component
Failure Mode
Electrical
Battery
Overcharging/Overdraining
Electric Shock
Explosion
Water Damage
Short Circuit
Thermal Shock
Computer Malfunction
Software Problem
Short/Open Circuit
Overheating
Overheating
Power Failure
Malfunction
Breakage of Mounts
Stuck/Failure to Adjust
Worn Out
UV Damage
Components Stop Working
Don't extend or latch
Breakage of Mounts
Leaking
Cracking
Worn Out
Detach from Frame
UV Damage
Leaking
Cracking
Scratched/Worn
Leaking
Scratched/Worn
Cracking
Absorbs Moisture
LCD Screen
Wiring
Heater
Interior
Controller
Seats
Dash
Seatbelts
Body
Body Panels
Windows
Windshield
Insulation
Probability of Occurrence Severity
8-9
6-7
2-3
8-9
2-3
7
1-2
9-10
7-8
4-5
7-8
4-5
7-8
4-5
7-8
4-5
System
Component
Failure Mode
Frame
Frame
Impact
Fatigue
Corrosion
Breaking of Welds/Joints
Improper Fit
Sagging
Seizing
Vibration
Excessive Wear
Lock Up
Failure to lock/latch
Fracture
Corrosion
Leaking
Seizing
Failure to lock/latch
Fracture
Corrosion
Leaking
Seizing
Suspension
Wheels
Tires
Brakes
Mechanisms Scissor Doors
Rear Hatch
System
3
9-10
6-7
6
6-7
4
Table 11: FMEA Analysis Assignment
Component
Failure Mode
Electrical
Battery
Heater
Interior
Seats
Seatbelts
Body
Probability of Occurrence Severity
Body Panels
Windshield/
Windows
Member
Assignment
Overcharging/Overdraining Brandon
Overheating
Kevin
Breakage of Mounts
Stuck/Failure to Adjust
Don’t Extend or Latch
Breakage of Mounts
Camille
Brad
Brad
Cracking
Wearing Out, UV Damage
Stretched/Worn
Jim
Damon
Damon
Frame
Frame(Doors)
Impact
Ryan
Mechanisms
Scissor Door
Rear Hatch
Failure to lock/Latch
Failure to lock/Latch
Chase
Michael
Enclosure Material Decision
An engineering decision had to be made concerning the material with which the enclosure of the
vehicle will be constructed. An acceptable decision will be supported by a number of
considerations and engineering methods including the following: FMEA, Value Engineering and
Functional Analysis, Benchmarking, Target Specifications, Design for Safety, Impact/Effects,
Design Analysis, and Testing. Figure 23 is a SolidEdge image of the general shape of the
vehicle’s enclosure.
Figure 23: SolidEdge Enclosure Model
FMEA for Enclosure
To begin the application of FMEA, enclosure failures were brainstormed and various lists of
example failure modes were considered. A more extensive list of failures than that shown above
displays those types of failures relevant to the panels of the enclosure and is given below in
Table 12.
Table 12: Table of Enclosure Panel Failure Modes
Leaking
Cracking
Wearing
Detachment
UV Damage
Impact
Fatigue
Expansion/Contraction Chemical Reaction
Rubbing
Deformation
Insulation Factor
Ruined Finish
Vibration
Takes on Moisture
Looseness
Obstructs View
Noisy
Melting
Corrosion
The team identified the critical failure modes (in bold) from the list above as cracking/fracture
and wearing/corrosion. These were selected because of the high probability for each to occur
and their potential impacts on the system. This probability of occurrence was given a rating of 78 for both modes of failure due to the constant weathering and wear and tear that the enclosure
could be subjected to during normal operation. The severity for each failure was given a rating
of 4-5. Both failures have significant operational impacts on the enclosure and other subsystems,
but they do not pose a direct threat to the occupants of the vehicle. Cracking or fracture of a
panel would make the enclosure unable to further protect the passengers, cargo, and the electrical
and propulsion systems from the environment. This could have potentially damaging effects on
the batteries, controller, or motor. It may also cause damage to the insulation which would
reduce the effectiveness of the heating system. Wearing and corrosion of body panels would
greatly affect the appeal of the enclosure by altering its appearance. This would be detrimental
to the effectiveness of the transporter as an appealing product because aesthetics is a major part
of the business opportunity and design. It may also lead to other failures such as panel cracking
if it is not repaired.
Although detailed analysis was not performed for every failure mode, each was considered
throughout the process of designing the enclosure.
The purpose of the method of 5 Whys and a fishbone (Ishikawa or cause and effect) diagram are
similar in that they are both aids in determining the root cause of a particular problem. Possible
root causes of the critical failure modes were determined using these tools in conjunction. See
Appendix C for more detailed analysis and the FMEA worksheets. The problem being
considered is to be placed at the head of a fishbone. The causes are then categorized into the ribs
of the diagram. The fishbone diagram aids the user in identifying as many causes of a particular
failure as possible. The diagrams for the critical failure modes are presented in Figures 24 and
25 below.
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Figure 24: Fishbone (Ishikawa) Diagram for Wearing/Corrosion
The lack of a protective coating or processing to increase a material’s hardness was determined
as an important root cause of wearing. As a preventative measure, it was advised that the chosen
material for the enclosure have a high resistance to scratching and impacts associated with the
normal operation of the transporter, or a procedure or coating must exist to enhance the specified
material’s properties.
46
Figure 25: Fishbone (Ishikawa) Diagram for Cracking/Fracture
It was found that a root cause for the cracking or fracturing of the enclosure panels could be a
reduced thickness in a given area or too much stress on areas such as those near the door or hatch
hinge. In order to prevent any such failure, proper analysis of the material will be performed to
find any weaknesses. The panels will be designed in order to withstand a high amount of stress.
Making sections of the body panel thicker near the hinges or connections is one possible
solution.
Value Engineering for Enclosure
Typical questions associated with value engineering were asked to begin analyzing the enclosure
from a functional perspective. These include:
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What does it do?
What else will do that?
What must it do?
What must it not do?
Can we do without?
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To help answer these questions and visualize the enclosure’s functions, a Functional Analysis
System Technique (FAST) diagram was employed. The target specifications and business
opportunity require an enclosure for weather protection, four-season capability, and climate
control. These requirements were lumped into an overall goal for the enclosure to maintain the
comfort of the passengers. The basic functions of the enclosure subsystem were established as
protecting the passengers from inclement weather and maintaining a comfortable cabin
temperature. This is how the enclosure will achieve this goal. The question how was asked of
each function until an input function, defined as that which initiates the subject at hand, was
found. The input of the enclosure is its attachment to the transporter frame. The scope is what
the study is concerned with, and it is every function located between the two scope lines just
inside the goal and input functions. The scope is every function that must be considered in
design and that the enclosure must perform. The FAST diagram created for the enclosure of the
transporter is shown below in Figure 26.
HOW
WHEN
Goal
Maintain
Passenger
Comfort
Protect
Passengers
from Inclement
Weather
WHY
Prevents
Weather from
Entering Cabin
Withstands
Forces due to
Weather
Distributes
Loads
Prevent Hot
Air from
Escaping
Cabin
Basic
Functions
Maintain
Comfortable
Cabin
Temperature
Stops Rain,
Snow, and
Wind
Provide
Barrier from
Outside Air
Prevent Cold
Air from
Entering Cabin
Prevent
Conduction
of Heat
Input
Prevent Air
Leakage
Covers Joints
and Gaps
Attaches to
Frame
Acts as an
Insulator
SCOPE
Figure 26: FAST Diagram for Enclosure
The enclosure plays a large part in the control of the conditions inside the vehicle. It is evident
from the FAST diagram that the design of the enclosure will have direct impacts on the heating
system. It will help define the required output of the heater. The heat required will also have
effects on the electrical system. Based on the heater output needed, appropriate selection of
batteries must be made to supply sufficient energy for extended times of heating. The enclosure
must also reduce the losses of the system by preventing air flow in and out of the vehicle and
conduction through the panels.
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Functional analysis also reveals a need for the enclosure to be constructed of a strong weatherresistant material. It must be able to withstand loads associated with inclement weather such as
rain and other forms of precipitation and wind in order to protect the occupants. This
requirement will help determine the required material strength and its associated thickness.
Based on the roles of the enclosure that have been clarified, required material properties such as
strength and conductivity can be verified as important to the proper function of the enclosure.
Benchmarking for Enclosure
Some of the materials being considered for the enclosure are due to benchmarking. The
benchmarking of NEVs, golf carts, and other similar vehicles showed a preference toward
designs with lightweight materials such as thermoformed plastics such as acrylonitrile butadiene
styrene (ABS), fiberglass, and aluminum. Steel and other composites were also researched and
considered in the enclosure material decision due to their availability, corrosion resistance, or
strength. A list of benchmarked vehicles and their respective enclosure materials is included in
Table 13.
Table 13: Benchmarked Vehicles and Respective Enclosure Materials
Enclosure Materials
Vehicle
Zenn (Zero
Emission No
Noise)
Nevco Gizmo
GEM
Dynasty Electric
Car
Electric Cars
and Carts
California
Roadster
Electric Cars
and Carts
California
Hummer H3
B.I.G. Man
Aerorider
Twike
ABS or
similar plastic
Fiberglass
X
X
X
X
X
X
X
X
X
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Aluminum
As previously stated, lightweight materials are preferred to reduce the overall weight of electric
vehicles. From the above table, it can be assumed that plastics and fiberglass are readily
available due to widespread usage for NEVs and other electric vehicles.
Target Specifications/System Impacts for Enclosure
From the target specifications of the vehicle, important information can be gathered on the
necessary material properties of the enclosure. For instance, considering the specification for the
overall weight of the transporter, the enclosure should contribute very little. Therefore, a high
strength-to-weight ratio and a low density are desirable. The weight of the enclosure will have
significant impacts on the overall weight of the vehicle thus effecting the requirements for a
propulsion system.
Table 14 displays general properties of some of the materials being considered for the material of
the enclosure. These were used for ballpark estimates and to gain an understanding of a few
materials that were otherwise unfamiliar.
Table 14: Material Comparison Chart
Tensile
Strength
(Ksi)
Compression
Strength
(Ksi)
Elastic (E)
Modulus
(Msi)
(D)
Density
(lbs/in³)
Carbon Fiber
Epoxy
Kevlar Epoxy
120
50
18.5
0.054
200
40
12
0.05
E-Glass Epoxy
100
50
5.5
0.069
6061-T6 Aluminum
45
35
10
0.098
Titanium
115
63
15
0.162
Steel
95
75
30
0.284
Material
It can be seen that aluminum and composites have much lower densities compared to other
metals making them better suited for electric vehicles.
A climate control specification was created for the transporter to maintain a temperature of 65˚F
when the ambient temperature is 32˚F. The heat lost through the enclosure has a large impact on
the requirements of the heating system. Therefore, the material chosen should have a low
coefficient of conduction to help reduce heat losses. This will also reduce the number of
batteries needed to adequately power the heater. Fiberglass, Kevlar, and plastics were all found
to have low conductivity.
As part of the business opportunity, the enclosure should exhibit some appealing properties such
as a smooth, colorful finish and rounded shape. This requires that the material be easily
manufactured or processed to achieve the desired shape and look. This is also important for
production costs and time. Fiberglass, carbon fiber, and plastic have generally good machining
characteristics when compared to Kevlar and metals.
50
Although they are readily available, metals such as aluminum and steel were eliminated as
possible materials for the enclosure due to their weight, formability, and conduction properties
when compared to those of composites and plastics. Also, composites and plastics are primarily
used for NEVs and similar products. Information about plastics, specifically ABS, was gathered
and added to Table 15 which was a comparison of common composites and originally found at
www.fibreglast.com. Shown in this table is a relative comparison of the remaining materials
with respect to various properties important to the enclosure design.
Table 15: Relative Cost/Functionality Comparison of Materials
Specifications
Cost
Density
Sanding/Machining
Heat Resistance
Moisture Resistance
Stiffness
Tensile Strength
Compressive Strength
Electrical Conductivity
Abrasion Resistance
Fatigue Resistance
Resin Compatibility
Comparison of Body Materials
Composites
Fiberglass
Carbon
Kevlar
E
P
F
P
E
E
E
E
P
E
E
F
G
G
F
F
F
G
F
E
G
G
E
P
P
E
P
F
F
E
G-E
G
E
E
E
F
P = Poor
F = Fair
G = Good
Plastics
ABS
P
E
E
E
G
G
P
P
P
N/A
N/A
E
E = Excellent
Decision
Based on the above considerations, analysis, and comparison of alternatives, the decision was
made to use fiberglass for the construction of the enclosure. This decision demands additional
research and action for further detailed design. This includes some testing of fiberglass for a
better physical understanding, an enclosure mock-up to determine its separation into individual
panels, and safety considerations associated with fiberglass production and handling.
Fiberglass Testing
To become familiar with fiberglass and estimate the required thickness for the enclosure, simple
tests need to be conducted on some sample material. This testing will also serve as a reality
check for the previous research to validate the general strength and stiffness and impact and
abrasion resistance. The fiberglass in the following experiments was obtained from a gas tank.
The original structure is displayed in Figure 27.
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Figure 27: Fiberglass Gas Tank to be used for Testing
Using a reciprocating saw, the gas tank was divided into manageable pieces for testing and to
determine the thickness of the material. This was approximately 1/16” for most pieces containing
one layer. There were three different parts tested. These were a flat panel, a curved portion, and
a reinforced section. Some initial observations of the material were made just from handling the
pieces prior to the experiments.
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It was extremely flexible and showed no signs of cracking or fracture when bent to a
great extent.
It was very flimsy and easily deflected.
The material was very tough and resisted impacts, scratches, and general wear and tear.
The separated pieces are shown in Figure 28 below.
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Figure 28: Fiberglass Gas Tank Separated into Pieces for Testing
The tests performed were deflection and strength tests. The ends of each part were fixed and
various weights were placed near the center. First, a flat section of the fiberglass was tested.
This piece was quite flimsy and deflected greatly (> 2”) under a load of only 10 lbs, but the piece
showed no visible or auditory signs of failure for a load up to 45 lbs. Figure 29 shows the flat
piece with a load of 15 lbs.
Figure 29: Testing of Flat Panel of Fiberglass (15 lbs. shown)
Below, Figure 30 shows the curved piece that was tested. It produced results similar to that of
the flat part. The shape did not add any strength or rigidity to the part.
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Figure 30: Example of Curved Section of Fiberglass
Two sections of the gas tank had two layers of fiberglass overlapped with some material in
between them (similar to a glue or caulk) to seal the gap. The two layers were also connected
with screws. An example of such a piece is shown below in Figure 31 and is loaded with 45 lbs.
in Figure 32.
Figure 31: Example of Reinforced Section of Fiberglass
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Figure 32: Testing of Reinforced Section of Fiberglass (45 lbs. shown)
The reinforced section of fiberglass deflected very little (< ½”) under the 45 lb. load. This part
was much stiffer and also showed no signs of failure.
Some important conclusions can be drawn from this experiment with respect to the construction
of the enclosure with fiberglass.
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The fiberglass used for the enclosure must be somewhat thicker and stiffer (at least ⅛”) to
reduce deflection under very small loads (< 20 lbs.).
The toughness and impact and scratch resistance of the material are confirmed by
observations made during experimentation.
The testing of fiberglass was also performed on prototyped test panels. This experimenting
yielded superior results because the exact composition of the panels was known and more
extensive testing could be performed. These parts were created using ¾ oz. chopped strand
fiberglass mat and a non-hazardous water-based resin known as Aqua-Resin. The properties of
Aqua-Resin are somewhat comparable to conventional resins. It is sufficient for testing and
drawing some conclusions about the final design of the enclosure. A detailed explanation of this
testing and decision process is given in the Conclusions (section 8.0).
Enclosure Cost and Weight Estimates
Composite consists mainly of reinforcement, glass fibers in this case, and a polymer matrix
known as a resin. The operating conditions in which the enclosure will be used are a large factor
in determining the specific types of fiberglass and resin to use.
55
Although fiberglass has been previously selected and justified for the enclosure, there are many
forms and weave types available to choose from. Each of these forms offers some unique
properties. These include a tow or roving, veil mats, chopped strand mats, and woven fabrics.
Roving exhibits the highest material properties of the reinforcement. They are typically supplied
on a large spool and cut as needed for stiffness. A veil consists of long thin fibers randomly
looped throughout the roll. Generally, these are used for a smoother layer just under the surface
coat. Chopped strand mats are low in strength, but they are equally strong in all directions.
Woven fabrics are strong reinforcements. They are fibers bundled into yarns oriented in just two
directions and offer strength in those two directions. Layers can be oriented differently for a part
to have strength in multiple directions. There are also many types of weaves to choose from.
For strength, versatility, and formability, a 7.5 oz. and a 10 oz. plain weave will be considered.
The name implies that the fabric weighs approximately 7.5 or 10 oz. per square yard,
respectively. These are also known as “boat cloths” because they are generally used to
waterproof and protect boat surfaces.
A manual, wet lay-up molding process is to be used in the production of the enclosure. It is a
widely-used composite production process for fiberglass and polyester resins.
The following products considered, prices, and procedure for calculating material costs and
weights are from Fibre Glast Developments Corporation (www.fibreglast.com).
The total surface area of the enclosure was obtained from a SolidEdge model as approximately
93.95 ft2 or 10.44 yd2. This value was used to calculate the weight of a layer of each fabric for
comparison purposes.
(7.5 oz/yd2) * (10.44 yd2) / (16 oz/lb) = 4.89 lbs/layer
(10 oz/yd2) * (10.44 yd2) / (16 oz/lb) = 6.52 lbs/layer
The lighter fabric was chosen to reduce the weight of the enclosure without sacrificing too much
strength. The 7.5 oz fabric is also the most common boat cloth available. 8 plies (layers) of 7.5
oz fabric at .011” thickness should create a strong, 1/10” to 1/8” laminate thickness.
(4.89 lbs/layer) * (8 layers) = 39.14 lbs
Generally, a 50/50 fabric-resin (by weight) ratio is used to guarantee the fabric is saturated. So,
the resin required will weigh the same as the total weight of the fabric (≈ 39.14 pounds). From
these values, we can make an initial estimate that the total weight of the enclosure will be around
80 to 90 pounds.
Now, the cost of each material required must be calculated. Fabric is generally sold by the yard
for a few different widths depending on the size of parts being made. A 38” wide fabric will be
used for the following calculations.
Total Area of Fabric = (10.44 yd2) * (8 layers) = 83.51 yd2
56
So, about 84 yards of 38” wide, 7.5 oz fabric is required for one enclosure. For 10 or more rolls
of fabric, each containing 125 yards, the cost is $4.40 per yard.
(84 yards) * ($4.40 per yard) = $370 per enclosure
For molding and low cost part fabrication, a polyester molding resin will be used. The cost of
#77 Molding Resin is $2.65 per pound for 4 drums (500 pounds each) or more. Nearly 40
pounds of resin is required. This is equivalent to about 5 gallons.
(40 lb) * ($2.65 per pound) = $106 per enclosure
A hardener is required in specific concentrations for each resin to promote the curing of the
resin. MEKP hardener #69 is needed for use with the chosen polyester resin in a 1%
concentration (by weight). For 5 gallons of resin, 6.5 oz of hardener will be used. A case of 4
gallons of hardener costs $129.95 which is $34.49 per gallon.
(6.5 oz) * (1 gallon/128 fluid oz) * ($32.49 per gallon) = $1.65 per enclosure
A 15 to 20 mil (0.015” or 0.020”) thick gel coat is required for all laminates. It is an unreinforced, clear or pigmented coating resin applied to the surface of a mold or part to provide a
smooth, more impervious finish on the part exterior (Composite Resources, 2007). 1 gallon of
gel coat mix covers 80 ft2 at 20 mils and weighs about 9 pounds. For the enclosure, which has a
total area of about 94 ft2, an acceptable 17 mil gel coat can be applied to the exterior and interior
surfaces with two gallons. The #173 Super High Gloss Gel Coat Kit is fully UV resistant and
compatible with pigment. It costs $229.95 for a kit of 4 gallons and the necessary hardener.
($229.95 per kit) / (4 gallons per kit) * (2 gallons per enclosure) = $114.98 per enclosure
A pigment can be added to the gel coat to color the enclosure. They are added in at a ratio of ½
pint of pigment per gallon of resin. 1 pint will be required for the 2 gallons of gel coat required
for the enclosure. 1 gallon of pigment costs $189.95.
(1 pint pigment) * (1 gallon/8 pints) * ($189.95 per gallon) = $23.74 per enclosure
Summing the cost of each material per enclosure, the estimated total cost of the materials for the
fiberglass enclosure is $616.
Fiberglass Fabric ≈ 40 lbs
Polyester Resin ≈ 40 lbs
Gel Coat ≈ 18 lbs
Hardener & Pigment ≈ 1 to 2 lbs
Summing the weight of each material per enclosure, the estimated total weight of the materials
for the fiberglass enclosure is 100 to 105 pounds.
Enclosure Mock-Up and DFMA
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To determine the best method to divide the enclosure into separate panels, some important
aspects of DFMA were considered. These are as follows:
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Fewer panels reduce assembly time and effort.
More panels reduce the size of each panel and increase the ease of handling for assembly,
machining, etc.
Easy removal of panels in potential impact zones for replacement.
Easy removal of panel(s) to gain access to the motor, batteries, etc. for maintenance.
More panels require more connections and joints increasing assembly time.
Make enclosure symmetrical so panels are the same on both sides. This reduces the
number of molds needed and the amount of different parts being produced.
Simplification.
The mock-up of the enclosure was simply constructed from an erector set, sticky-tac adhesive,
and card stock. The initial mock-up of the enclosure without divisions for individual panels is
displayed in Figure 33.
Figure 33: Preliminary Enclosure Mock-Up
Taking into consideration the important points of DFMA noted above, the card stock was cut
into separate pieces and placed in various arrangements until a satisfactory combination was
found. The final grouping of panels can be seen in a picture of the mock-up, Figure 34, and an
exploded sketch of the enclosure which is shown in Figure 35.
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Figure 34: Final Enclosure Mock-Up
59
Figure 35: Sketch of Exploded Enclosure
The mock-up resulted in the enclosure being divided into approximately 14 panels. Many of the
divisions are a result of the parts becoming too bulky. Excessively large parts would require a
larger mold and would necessitate complex handling and machining processes. The front and
rear sections of the body were designed to include the corners and fractions of the quarter panels.
This is due to the high probability of an impact in these areas.
Connections to the Vehicle
The next step is to consider how the fiberglass panels will be connected to the frame or any other
elements of the project. After doing some research and benchmarking, there seems to be many
methods to connect fiberglass to multiple surface types. These techniques include self-tapping
screws, bolts, nuts, rivets, and adhesives. Using one or more of these types will help attach the
panels properly and most effectively. When looking into each style in more detail, some
60
interesting facts were found. The screws, nuts and bolts, and rivets can all come in various sizes.
If used, a standard size will be chosen in order to minimize multiple types of screws or rivets.
This has been determined by methods such as DFMA. Some examples of these fasteners can be
found below in Figure 36. Once the method of attachment is determined, a standard size will be
chosen. The adhesives can also be used in order to secure the panels with a good sealant to help
minimize leakage issues. More research will be performed for adhesives and sealants since the
panels need to be sealed for weather protection.
Figure 36: Examples of Rivets and Self-tapping screws
Self-tapping Screws
When looking into more detail of the styles of connections, we can up with some pros and cons
for each. Using the self-tapping screws would be helpful because there would be no need to cut
holes in either the fiberglass and frame or brackets. As the name explains, it would be able to
self-tap into the fiberglass and frame. Using this method can be helpful on the manufacturing
line because it is quick. Some of the cons of self-tapping screws are that it can potentially cause
harm to the fiberglass since it may cause stresses at the hole created. Another con is the fact that
there is a potential for misalignments or missed tolerances when screwing into the panels.
Specific guides, such as precut holes, help dramatically because help to show where to make a
connection.
Nuts & Bolts and Screws
A deeper look has been taken into using a nut and bolt system or a screw system that has a larger
cutout than the thread diameter on the screw. This can also be done with the nuts and bolts. One
method for using these styles is to cut a hole larger than the bolt or screw being placed through it.
This allows the bolt to be tightened down on the fiberglass, but does not cause a bigger stress on
the material because it gives it some freedom to move. One must be careful not to over tighten
the bolt or screw because this can cause the fiberglass to fracture from the stress. Most
benchmarked vehicles showed that they either had precut holes where screws did grab the
fiberglass or had holes slightly bigger. When we did testing on the fiberglass material we also
61
found a screw inside, it was used to hold the two pieces together and then the screw head was
covered with more fiberglass fibers to lock the screw in place. This helped to support the
method of using screws to hold fiberglass in place. Another pro for screws is how brackets can
be placed on the frames and then the fiberglass can be connected to these brackets instead of
directly to the frame. With more resources we would probably be able to construct a system that
allowed us to secure either a nut or bolt to the bracket or fiberglass for a smooth outer finish.
This may not be a desired method for the removable panels due to more complications on
removing the panels.
Rivets
When looking into the rivets method we have to consider how the stresses will affect the
fiberglass. Since fiberglass is such a strong material, the pressure that the rivets can cause may
not affect the properties of fiberglass. A pro for this method is the simplicity and the quickness
on the assembly line. There is some preparation for rivets, such as preparing cutouts and
installing the rivets. Some problems with rivets is how it makes its connections permanent, this
might not be desired for our design since we do know that we want to be able to remove some
panels. We can however use this method for panels that would most likely be permanent such as
the roof panel. However, if we go with another connection style this means we would use two
styles and this could cause an increase in labor costs and preparation time.
Future Plans
We expect to make a decision on which method to use by March 26th as a few more tests need to
be completed. Being able to make this decision allows us to get in contact with manufacturers to
get cost estimates of lots of 5000. We will also try to take a further look into adhesives and
sealants because we will need to incorporate both to help connect the panels properly and
effectively for our design scope.
Design for Safety
There are significant safety concerns associated with the production of fiberglass. Exposure to
fibrous glass may cause irritation of the skin and/or mouth, nose, and throat. Resins may also
have potentially harmful effects depending on the type being used. Here are some general
guidelines for working with a fiberglass composite, specifically a fiberglass fabric, polyester
resin, and gel coat:
ƒ
ƒ
Fiberglass Fabric
o Normal area ventilation should be sufficient to keep dust and fiber to acceptable
levels.
o Gloves, long sleeves, and eye protection such as safety glasses or side shields
should be worn to protect skin and eyes from airborne fibrous glass.
o Exposed skin should be washed after working with fiberglass.
o Clothing should be laundered separately from other clothing.
Polyester Resin
o Local ventilation may be required to keep fumes below limits.
62
ƒ
o Wear safety glasses with side shields or goggles and a face shield with both.
o Wear chemical resistant gloves and impervious clothing.
Gel Coat
o Do not inhale dust, mist, vapor, or fumes produced by the resin during processing
or handling.
o Wear an appropriate respirator during application and other use of the resin until
dust, mist, vapors, and fumes are exhausted.
o Avoid skin contact. Solvent impermeable gloves are recommended.
o Proper eye protection should be worn to protect against eye contact. These
include safety glasses with side shields, chemical goggles, or face shields.
Enclosure Windows and Windshield
The window material for the campus transporter must be lightweight, so it will not significantly
add to the weight of the enclosure, and it must be durable to withstand possible impacts and
abrasions from weather and normal operation.
Acrylic glass (Polymethyl methacrylate or PMMA) and polycarbonate were the materials mainly
considered for the window material of the enclosure due to their low weight and high impact
strength when compared with glass. Both materials require a special coating for abrasion
resistance and UV absorption.
Acrylic was determined to be the best alternative. It has greater UV stability than polycarbonate,
and it is less expensive. A ⅛” thickness is desired for all of the windows of the enclosure.
Acrylite Abrasion Resistant Acrylic Sheeting costs around $5.41 per ft2 for a thickness of ⅛”.
This price includes a 15% discount for bulk purchasing from United States Plastic Corporation.
This sheet has an abrasion resistant coating on both sides and is UV resistant.
J. Freeman, Inc. distributor of plastics offers Acrylite AR OP-3 (UV filtering and abrasion
resistant) for $4.84 per ft2 at 0.118” thickness. This is reduced to $4.11 per ft2 after a 15%
discount for bulk purchasing. The total material cost and weight were calculated using this type
of less expensive acrylic. The total area of the window material needed was obtained from the
SolidEdge model as 44.0 ft2. This value includes a panel that divides the cargo area and the
passenger compartment to reduce the space to be heated within the vehicle.
(44.0 ft2) * ($4.11 per ft2) = $181 per enclosure
(44.0 ft2) * [0.118” / (12”/ft)] * (1 m / 3.28 ft)3 * 1190 kg/m3 = 14.59 kg = 32.10 lb per enclosure
Battery Decision
Value Engineering
Since the vehicle being designed will have and electric propulsion system, batteries will be used
to supply all the necessary power to the electric drive motor and all of the accessory systems.
63
There are currently many types of batteries available that could possibly fulfill the power and
range requirements of an electric vehicle.
•
•
Battery Core Functions
Provide power to the propulsion system
Provide all auxiliary power to the heater and interior
Some options include deep cycle, marine deep cycle, and electric golf cart batteries. There are
many tradeoffs to consider in the matter of battery selection. There are many factors that must
be considered during the battery style selection process. The batteries selected for the vehicle
should meet as much of the following criteria as possible.
•
•
•
•
•
•
•
•
Battery Selection Criteria
Lightweight as possible
Low cost
Small Size
Low maintenance
Mounting and deign configuration freedom
Vibration resistance
Operation in extreme temperatures
Cycle Life
Battery
Weight
Cost
Different Size
Availability
Maintenance
Spill/Leak Proof
Vibration/Shock
Resistance
Functionality if
Battery Wall is
Breached
Operation in
Extreme
Temperatures
Overcharge
Recovery
Fast Charge
Capable
Power Density
Cycle Life
Table 16: Comparison of Battery Designs
Lead Acid
Lead Acid Wet Lead Acid Wet
Gel Cell
Cell Flooded
Cell Sealed
+
+
+
+
+
+
AGM Dry Cell
+
+
+
+
+
-
+
-
+
+
-
+
-
-
+
+
-
-
+
-
+
+
+
-
-
-
+
+
+
-
-
+
+
64
Total +’s
9
5
6
+ indicate positive attributes and – indicates negative attributes
10
Failure Mode and Effect Analysis (FMEA) for the Batteries
There are many different types of failure that can occur with batteries. Any failure of the
batteries will cause the vehicle to become inoperable. Battery failures can be broken down into
two distinct areas. These areas are internal failures and external failures. Internal failures are
failures that occur due problems inside the confines of the battery. Such failures could be due to
poor manufacturing, inferior materials, and poor construction. Internal failures are due mostly to
quality. These failures can be easily overcome by selecting high quality batteries from reputable
manufacturers.
External failures are failures of the batteries due to an outside cause. These failures are usually
due either to poor battery housing design, user abuse/misuse, or incorrect operation. External
failures can be anticipated and avoided.
Most Likely External Battery Failure Modes
•
•
•
Overcharging
Overheating
Over-discharging
To avoid these failures the batteries must not be operated outside of the manufacturer’s
recommended specifications. To prevent incorrect user operation and misuse, warning labels,
warning lights, and state of charge gages will be added to the vehicle to prevent overdischarging. The chance of overheating can be reduced by allowing the batteries to have
adequate ventilation for heat dissipation.
Overcharging poses a difficult problem. Possible solutions would be to have an automated
charging system that would automatically shut off when the batteries are fully charged. If this is
not plausible, warning labels with the appropriate charging time, currents, and voltages could be
affixed to the vehicle and a charging procedure could be included in the vehicle’s manual.
Designing for Safety (DFS) for the Batteries
Batteries can pose many safety concerns. Batteries are capable of shocking or exploding. For
these reasons, the batteries need to be stored outside of the cab area. One possibility is for the
batteries to be stored in a compartment underneath the seats. This compartment could be
insulated and constructed out of a rigid material that could safely withstand any forces generated
if a battery should explode. To prevent electrical and shock hazards the batteries will need to be
anchored by a strap or other means. This will prevent the terminals from grounding against any
metallic surfaces. All of the electrical wiring for the batteries should either be located outside of
the cab or in an area where the wires cannot shock the occupant.
Target Specifications
To meet the established target specs, the batteries will need to meet the following requirements.
65
•
•
•
•
Target Specifications that Impact the Batteries
Four Season Capable (Temperatures of 15o – 105o F)
A charging time under 10 hours
Need to provide enough energy for an operating range of 30 miles
Need to provide enough energy to allow the motor to accelerate from 0-20MPH in 8
seconds.
Battery Decision and Its Impact on the Overall System
The batteries are core to the operation of this electric vehicle. Based on the target specifications
and all the available batteries and configurations AGM (absorbed glass mat) batteries were
chosen. These batteries meet the most desired qualities. Many types of AGM batteries are
offered.
The battery decision has large effects on the rest of the system. A balance had to be established
between the number of batteries required to meet the target specifications and the vehicle’s total
weight. The 48 volt propulsion system could be powered by 4 large in series or 8 small batteries
in a series-parallel combination. The 8 small batteries were chosen because their total weight was
less than that of the 4 large batteries. The 8 smaller batteries would also require much less space
within the vehicle. For these reasons, the smaller Optima Dual Purpose Deep Cycle and Starting
D51 battery was chosen over its larger counterparts. Its exact specifications are listed in Table
17.
Table 17: Characteristics of Selected Battery
Physical Size
Model
D51
Associated
Amp
Volts
References
Hours1
8071-167
--SC51DA
CCA2 CA2
Case
Reserve Length x Width x Height
@
@
Size
Weight Terminals
(inches)
Minutes3
0° F 32° F Category
(Height includes 1"
terminals)
500
12V 41 AH
CCA
625
CA
Small
70
Case Size Category:
Small
9.25 x 5.0 x 9.0"
Height includes 1"
terminals
26.0
lbs
Top Post
A transformer will be utilized to convert the 48 volts supply into 12 volts for all of the
accessories. There will be extra 2 batteries that will be used solely to supply power to the heater.
The 10 total batteries required have a combined weight of 260 pounds.
Climate Control Heating
Note To Ryan: I don’t have a copy of the latest target specs but to make sure they
are up to date here are the thermal performance ones. 1: attain 65 degF inside when
32 degF outside, (18.3 degC temperature differential). 2.Attain the target temp in
less than 10 minutes.
66
Climate Control Heating
The purpose and function of the heating system is to provide a comfortable interior environment
for the driver and passenger. This system has been designed for the target specification to
maintain an interior cabin temperature of 65 ˚F when the exterior temperature is 32 ˚F. While
analysis is a significant part of the design process, many other design methods were used to
develop this system. The proposed location for the heater is seen in Figure 37
Figure 37: Location of Heater in Vehicle Design
The first step of the system design was an initial feasibility investigation, which eventually
developed into a simulated model. The purpose of the original feasibility investigation was to
estimate the heat input required and determine if this feature could be implemented at reasonable
cost. Ultimately, the result of the feasibility investigation was that implementing this feature
would be feasible if certain changes and optimizations were made.
From the initial analysis, our team was able to identify which variables/decisions had the largest
impact on the required heat input. This impacted other design decisions, such as the body
material and insulation material. Resulting from the simulation and the rest of the design
methods, stemmed a decision to use ¼” thick fiberglass for the body, ½” of thermal insulation,
and ¼” thick acrylic windows. The properties of these materials were used for the final analysis.
Sizing and selection of heating options was done using the results of the final analysis. After the
initial feasibility investigation and many optimization iterations, the required heat output was
reduced to approximately 476 watts. This is the minimum heat input required to attain the target
specification.
The Model & Analysis
Main Assumptions
• No heat losses due to mass transfer between interior and exterior
• No radiation
• Free convection inside cab
• Exterior forced convention (flat plate assumption @ max velocity & Gr/Re2 << 1)
• Only front half of vehicle is heated due to dividing wall
• Even temperature distribution within cabin
67
The purpose of making these assumptions is to simplify the models complexity. The assumption
that will likely have the largest effect is the no radiation assumption. The magnitude of the no
radiation assumption became apparent in the prototype testing, see section 8.0, and the target
specifications were still met.
Minimum Heat Required
The main idea behind the model is that at the steady state temperature differential, the heat input
is equal to the heat losses. Thus, the required heat input is found by calculating the heat losses at
the target spec temperature differential (65 ˚F interior temperature with 32 ˚F exterior
temperature). The heat flux (heat per unit area) through the body and through the windows was
calculated using the resistive circuit analogy. Using the total body and window areas the total
heat loss was calculated. The total window area includes the side windows, front windshield,
and the dividing wall (top portion). The total body area includes, the front, top, bottom, both
sides, and the bottom portion of the dividing wall as seen in Figure 38.
Figure 38: Heat Flow through Body and Windows
Equations 18 and 19 are the two equations used for the calculation of the heat loss through the
body panels and windows.
QBody
⎛
⎜
Ti − T0
= ABody ⎜
⎜ 1
L
L
1
+ in + B +
⎜
⎝ hin K in K B ho
68
⎞
⎟
⎟
⎟
⎟
⎠
Eq. 21
QWindow
⎛
⎞
⎜
⎟
Ti − T0
⎜
⎟
= AWind
⎜ 1
Lw
1 ⎟
+
+ ⎟
⎜
⎝ hin K w ho ⎠
Eq. 22
Where, the insulation thermal conductivity Kin=.03, thickness of the insulation Lin=.0127m, area
of windows Awind=3.4266 m2, thermal conductivity windows Kw=.24 W/mK, thickness of
windows Lw=.00635 m, thermal conductivity of body Kb= .288 W/mK, thickness of body panels
Lb= .00635 m, area of body panels Ab=7.345 m2, convection coefficient interior hin=5 W/m2k,
convection coefficient exterior ho=150 W/m2k.
Although the primary purpose of this model is to estimate the minimum required heat input, it
also gives insight as to which factors/variables have the greatest impact on the required heat
input. It is observed in the heat flux equations that the interior convection coefficient hin has a
large impact on the required heat input. A small variation of hin can significantly effect the
required heat input. To justify/calculate the interior convection coefficient, the velocity of the
interior air due to ventilation had to be estimated. The minimum ventilation target specification
of 20 cubic feet per minute is much lower than most combined heater/fan products. The
volumetric flow rate assumed was 102 cfm, five times more than the minimum target spec but
concurrent with available products.
Determining the Convection Coefficients
Using a flow rate of 102 cfm and the vehicle cross-sectional area of 1.67 m2, the interior air
velocity is estimated to be .028 m/s. Utilizing the vertical plate assumption and interior air
velocity in conjunction with the Reynolds number, the interior convection coefficient was
estimated to be 2.545 W/m2K, see Appendix D. The vertical plate assumption is for a free
convective flow, which is justified by the ratio of the Grashoff and Reynolds numbers. The
original assumed value of 5 W/m2K was selected based on the general rule that for free
convection the coefficient is typically between 2 and 20 W/m2K. The calculated convection
coefficient hin=2.545 W/m2K is lower than the assumed value of 5 W/m2K, but since the actual
design geometry varies from the vertical plate assumption it was decided to use a conservative
approach and perform any further analyses with the original value of 5 W/m2K. This calculated
value essentially confirms that the value being used is within the correct range for the given
assumptions.
The exterior convection coefficient was calculated with the same process. By using the
relationship of the Grashoff and Reynolds numbers, see Appendix D, it was determined that as
long as the vehicle is traveling at .38 m/s the free convection of the vehicle could be neglected.
At the maximum velocity, the flow over the body using the flat plate assumption begins as a
laminar flow and transitions to turbulent flow. The method used to calculate the average
convection coefficient for the characteristic length is shown in Appendix D. The average
convection coefficient across the surface was calculated to be 26.3 W/m2K. This is less than the
assumed value of 150 W/m2K, but since this difference causes a small change in the required
heat input, less than 10 W, a conservative approach was taken and all further analysis was
69
performed using the original assumed value. From this derivation, it is also determined that
largest convection coefficients occur at higher velocities. Thus, the worst case scenario is when
the vehicle travels at its maximum velocity of 25 mph.
Estimation of the Rate of Temperature Increase
The time it takes for the cabin temperature to increase is estimated using numerical methods.
This is accomplished by using a very small time step and finding the temperature increase of the
air over that time step. The losses associated with the small increase in temperature are
calculated and factored into the new cabin temperature. The time step is advanced until the
difference between the input and the losses is less than .5 watt. Using Matlab (see Appendix D),
the cabin temperature was plotted as a function of time (see Figure 39). The first three iterations
of this method were done by hand and compared to the Matlab result.
Figure 39: Interior Cabin Temperature as a Function of Time.
70
Figure 40: Losses and Net Heat Input
Figure 41: Heat Lost Through Body vs. Windows
Real World Testing for Simulation Confirmation
The results from the simulation/model are theoretical estimates. This is why a real world
experiment was devised to test the simulation and confirm/reject its result. The experiment
estimated the physical dimensions of a car and took data of the heating system performance.
After the cars engine had warmed up, the heat and fan were set to the maximum level and the
interior temperature recorded every minute until steady state conditions were attained. The
71
steady state interior temperature reached was 99 ˚F with an exterior temperature of 19 ˚F, see
Figure 42.
Figure 42: Experimental Test
Inputting the exterior temperature, maximum interior temperature, surface areas, and thermal
conductivities etc, into the simulation resulted in a value of 4.438 kW (15140 Btu) for the
required heat input. This result of 15140 Btu is in between the typical heat output of a passenger
car of this size, which is 13000 to 17000 Btu. While the testing confirms our simulations output
for the heat required, it slightly disagrees with the rate at which the interior temperature
increases.
For the experimental parameters, the simulation predicts that the steady state conditions will be
reached in nearly nine minutes, see Appendix D. The actual time to reach steady state was 23
minutes, over twice the time as predicted by the simulation. The initial reasoning as to why there
is such a large discrepancy points toward the accuracy of the numerical method used. However,
there is also an experimental aspect to the error. Items within the car, including 5 gallons of
frozen water, were absorbing some of the heat energy, the energy absorbed by these items are
losses but are not losses to the surroundings and are not factored into the simulation.
Final Result
Using the body design ( ¼” fiberglass for the body material with ½” of polystyrene insulation
and ¼” acrylic windows) a minimum heat input of 476 Watts is required to maintain an interior
temperature of 65 ˚F when the exterior is 32 ˚F. The maximum projected time to reach the
steady state condition for the at the maximum temperature differential is about 16 min.
However, the specific heater used in the design is predicted to reach the target temperature in 4.5
minutes, well before the 10 minutes target time.
Designing for Failure Modes
72
Failure of the heating system can occur in many different ways. While some of the failures have
minor consequences, a few of them could result is serious bodily harm and damage to the
vehicle. Table 18 shows the potential failure modes for the heating system.
Table 18: Potential Failure Modes for Heater
Electrical
• Short circuit
• Fan motor malfunction
• Thermostat malfunction
• Fuse fails to function
Mechanical
• Proximity to other vehicle parts causes damage (clearances)
• Overheating
• Build up of dust or foreign objects that ignite
• Impact causing deformation of heating unit/vents
• Clogged vents or filters
• Compensated cabin enclosure
Other
• Not enough heat output
• Too much noise
• Large effect on vehicle range
Designing for these failure modes was based on the impacts/consequences of failure and the
probability of occurrence. An FMEA performed on the heater identified that overheating of the
unit could cause severe harm to both the vehicle and the occupants, and since overheating can
occur through several different modes the probability of occurrence is relatively high. The
recommended action to address the overheating failure was to select a heater that has a built in
safety thermostat or to add one if it does not. This safety thermostat effectively turns off the
power supplied to the heater when the temperature exceeds its designed limit. Including the
thermostat will prevent overheating of the unit for cases in which the fan fails, electrical short,
and clogged vents/filters.
Other failure modes, though less severe than the overheating scenario, have been accounted for
in designing this system. For instance, to address the heater noise failure the current design
includes a variable speed fan. Even though the noise will not be more than an average
automobile, the variable speed fan will allow the operator to reduce the noise of the fan if
desired.
Since the heater can potentially have a significant effect on energy available to the motor, it will
use a separate electrical system. This will prevent the failure situation where running the heater
will reduce the effective range of the vehicle. Using a single electrical system, it is likely that an
uninformed operator would not understand the ramifications of running the heater unnecessarily
and could greatly reduce the range of the vehicle. Having the heater on its own electrical supply
will eliminate this situation.
The failure mode of damage to the vehicle due to proximity (allowable clearances) is severe but
can be avoided. To avoid this failure, all of the manufacture clearance specifications are being
73
followed. Furthermore, the design of the mounting bracket and ventilation ducts use materials
that can withstand elevated temperatures.
Available Heating Methods
Several different methods of heating were considered for the vehicle, but only four of them were
deemed feasible enough for further investigation. Many different aspects of the heating methods
were compared, however safety was a large deciding factor in selecting the heating method.
Tables 19 and 20 compare key aspects of the heating methods selected for further investigation.
Table19: Heating Methods Comparison
Positive Aspects
Negative Aspects
Electrical
Infrared
Point specific
Electrical
Resistance
Cooler heating elements (comparatively)
Use existing electrical system
Many manufacturers
Capable of defrosting
Cheap
Dual function: heat & ventilate
Very hot heating element
Fragile elements (some units)
Few available low voltage units
Needs a lot of electrical power
Poor defrosting capability
Needs a lot of electrical power to meet
requirements
Propane
Easily meets power requirements
No effect on electrical system
Safety hazards: very hot, explosive
Added effort to get fuel
Federal regulations for vehicles
Limited defrosting ability
Heat Pump
Efficient
Less impact on electrical system
Heavy
Few/no manufactures for size needed
Complicated
Expensive
More difficult assembly
Table 20: Comparison of Heaters
Electrical
Resistance
Infrared
Resistance
Stored
Energy
Exposed
Electrics
Hot Parts
Rotating
Machinery
Leads
Leads
Moderate
Fan
Very
Propane
Infrared
Chemical
Energy
Compressed
Fluid
Heat Pumps
Very
Moderate
Compressor
Compressed
Fluid
The result from the comparison of each different method was the selection of the electrical
resistance heater. Compared to the other options, electrical resistance is: cheaper, safer, more
functional (dual purpose), and has more available products to choose from. However,
implementing this type of heater requires a substantial amount of electrical power which requires
74
adding additional batteries. Since adding the batteries effects the vehicles performance and adds
cost to the vehicle, the customer was consulted. The intent was to determine if the customer was
willing to pay more (high estimate $350), sacrifice on performance (1/2 mile off total range), and
if they would be willing to complete an extra step to charge the vehicle. The result of the
customer feedback had an overwhelming positive response. Thus, the customer considers the
value of implementing the electrical resistance heater to be more than the corresponding costs,
which further confirms the current selection.
Available Products and Selection
The minimum required heat input to reach the target specification is 476 W. Many electrical
resistance heaters are available and are near the power required. Evaluation of available heating
products resulted in the selection of a 24 volt electrical resistance heater with a 600 W output,
see Table 21 and Figure 43. Therm-Tec, the manufacture of the unit, confirmed that they are
able to produce this unit in lots of 5000 but did not want to disclose the price per unit. For a lot
of 5000 units, it is estimated that the price per unit would be $130.
Product Name
Volts (V)
Therm-Tec Mini
DC
Therm-Tec Back
Seat Heat
Golf Car Heater
12
Table21: Products
Heat Output T-stat Safety Shut- Fan
(W)
off
300
+
+
+
Market
Price
$108
24
600
+
+
+
$169
48
1000
-
-
+
$200
Red Quartz
Infrared
Portable Car
Ceramic
24
980
-
-
+
$238
12
150
-
-
+
$50
Roadpro
Ceramic
12
300
-
-
+
$35
Figure 43: 600 W Back Seat Heat
The 24 V Therm-Tec heater includes a variable thermostat, a fan, and a safety thermostat. From
the FMEA for the heater unit, see Appendix, it was recommended that the unit selected have a
safety thermostat to prevent overheating. By selecting the Therm-Tec unit, all of the desired
75
functions and features are already incorporated into the heater which will reduce the required
assembly time. Included with the Therm-Tec unit is a wiring harness and a mounting bracket
which allows the unit to rotate 30 degrees. This unit circulates 100 cfm, which easily meets the
target specification of 20 cfm. Power to the heating unit will be supplied by two optima D51
batteries, which contain 41 amp hours. At a current draw of 25 amps (maximum draw specified
by Therm-Tec), the optima batteries will be able to power the heating unit for 70 minutes until
the batteries reach the manufacture defined discharge state of 10.5 V. Overall, this design meets
the target specifications and adds the most value for the price.
The model calculates that for the 600W unit the maximum temperature differential is 24 ˚C and
will attain the target specification temperature of 18.3 ˚C in 4.5 minutes, see figure 44. Part of
the reason for selecting a 600 W heater is that it reaches the target temperature 10 minutes faster
than the minimum heater output of 473 W.
Figure 44: Thermal Performance for 600W Heater
Heater Location and Ventilation
Since the heater serves a dual purpose as a ventilation fan, it is necessary that the design allow
for exterior air to circulate into the vehicle. However, when heating the cabin it is critical that no
exterior air enter the vehicle. The first proposed design accomplished this through series of ducts
and vents, which ultimately added significant cost and complicated the assembly. After the first
optimization, the conventional ducts were eliminated, see Figure 45.
76
Heating Unit
Re-Circulation
Opening
Exterior Air Vent
Figure 45: Heater Location
In order to simplify the design, the heater is mounted flush with the dash board using the
mounting bracket provided by the manufacture. Instead of using a series of ducts to direct the
incoming air, a “chamber” in the hollow space just behind the heater has an opening to the
exterior and to the interior cabin. This enclosed space behind the heater also allows the heater to
rotate in the bracket up to 30 degrees so that warm air may be redirected to the windshield.
Clearances for the heater require that the walls of the chamber remain ½” from the sides of the
heating unit. Depending on the cost and thickness availability, the walls of the chamber will be
steel sheeting. To control the source of the circulating air, a small metal flap (not shown in
figure 33) will open or close the vent for exterior air. When the vent is open, the circulating air
will be a combination of exterior air and re-circulated air, when closed only interior air will
circulate. Currently, the flap is controlled by dash mounted knob that is linked to the flap
through a cable. Thus, as the knob pushed or pulled the flap rotates about the hinge. Covering
both openings is a small screen to keep foreign objects out of the vent.
Scissor door and rear hatch power assist and control
Function
To help the vehicle’s passengers easily enter and exit the vehicle and access the rear storage area,
it was decided to use some type of power assist on the two scissor doors and rear hatch. The
power assist will function as an enhanced convenience feature and also as an important safety
feature. The power assist greatly minimizes the risk of passenger injury/near-misses.
Specifically, without the power assist, bodily injury may occur such as inadvertently smashing of
the fingers or potentially hitting the head or other such injuries. Also, without the power assist,
the passengers may have difficulty opening the doors and maintaining that open position of the
door. Overall, the power assist provides the gentle guidance for opening and closing of the
scissor doors and rear hatch. Figure 46 shows the overall general placement of the pressurized
struts in the vehicle. Each scissor door will utilize one strut each and the rear hatch will utilize
two struts. The pressurized struts for the scissor door will be placed close to the door’s hinge in
77
the bottom corner, as shown by the red arrows in Figure 46. The two struts for the rear hatch will
be placed in each of the upper corners of the rear hatch.
Figure 46: General location of the struts in the vehicle
Economics/Value
Based on the benchmarking and research processes conducted and utilized, possible power assist
mechanisms identified for consideration include pressurized gas struts, torsion bars/springs and
rotary dampers. The following table provides a function and cost comparison of the pressurized
gas struts/springs versus mechanical springs. The rotary dampers were not included in this
evaluation and were immediately excluded due to research and benchmarking evaluations
showing limited use in such applications.
Table 22: Cost and value comparison of mechanisms
Pressurized Gas Struts
Mechanical Springs
Low cost
Low cost
Very low spring rate
High spring rate
Small design/size
Bulky design
Controlled dampening
Yes
No
Multiple Extension Rates
Yes
No
Weaker in colder
climates
None
Cost
Spring Rate
Required Space
Temperature Effects
78
The above table illustrates some of the advantages which pressurized gas struts have over the
mechanical springs. Although, the two mechanisms are comparable in cost, the pressurized gas
struts are more adaptable than mechanical springs and will provide more value. The total cost for
the gas struts for the purchase of four will be $. The gas struts allow for controlled motion and
speed for the doors and a cushioned end motion which meet the required specifications.
Controlled motion cannot be achieved with the mechanical springs. The pressurized gas struts
have a very low spring rate and occupy minimal space in the vehicle; to design a mechanical
spring with the same low spring rate would require almost twice the space. The only downside to
the pressurized gas strut is that there is a potential for the gas struts to weaken in colder climates,
however they will still be operable. Research and benchmarking confirms the decision to use the
pressurized gas struts and indicates that gas struts are in fact used on a larger scale to hold up
doors, hatches and hoods on vehicles rather than mechanical springs.
Figure 47 contains pictures of pressurized gas struts. The gas strut consists of the following: a
piston rod, pressurized cylinder, sealing system, nitrogen gas charge for the gas springs, and a
lubricant. The struts can be connected to the vehicle by numerous connections. They can be
connected by a hinge eye, fork heads, elbow joints, ball joints and metal fittings. End
connections that minimize side load forces to the strut should be chosen.
Figure 47: Pressurized Gas Struts
The vehicle will be equipped with a total of four pressurized gas struts. Two of the gas struts will
be installed for use on the rear hatch, while the other two struts will be installed on each of the
side scissor doors. Although, the use of one strut would work for the rear hatch, given the cost,
roughly only $11 dollars would be saved from using one strut. Therefore, it was decided to
proceed with the use of two struts for the rear hatch. The gas struts will be securely attached to
the steel frame of the vehicle. Each strut will be secured in two places: attached to the door frame
and also attached to the vehicle’s frame. The struts will be connected through eyelet end fittings
with the use of steel brackets, which will be mounted to the vehicle’s frame. They will be able to
operate efficiently under the weight of the doors which was estimated to be around 40 lbs. With a
small initial force applied to the handle of the doors the struts will open the doors and keep them
safely in the open position. A small force from the user will be required to close the doors. The
struts will be purchased from McMaster Carr who can meet our required specifications (lift
force, total extended length and end connections). Table 23 contains the ordering information for
the struts and eyelet end fittings. The part number from McMaster Carr for the strut is 9416K16
and the part number for the end fittings is 6465K61. The total cost for the four struts and eight
eyelet fittings will cost roughly $62. For a lot of 5000 it will cost roughly $262,000.
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Table 23: McMaster Carr strut ordering information
Part
Quantity
Gas Strut
2
Gas Strut
2
Eyelet Fittings
8
Description
40 lb force, 13.74” extended lg., 8.27” compressed lg.,
5.47” stroke lg., steel
90 lb force, 13.74” extended lg., 8.27” compressed lg.,
5.47” stroke lg., steel
.39” eyelet diameter, .39” thick, zinc
Cost
$10.89
$10.89
$2.27
FMEA/Safety
Below is a table of the possible failure modes of the gas struts. To avoid some of the failures the
following should be considered when deciding on a particular manufacturer for the gas struts: the
use of a non flammable gas inside the compressed cylinders to avoid possible explosions, take
the necessary precautions to ensure the cylinders are not punctured, the use of two gas struts on
the rear hatch in case one should fail, and end stops so the system doesn’t become over
compressed or overextended. Also, the use of locking struts could be utilized to ensure that the
struts would not fail and come slamming down injuring users. With locking struts, the struts have
the ability to lock in position when opened. Those are just a few solutions to the possible failure
modes of the gas struts.
•
•
•
•
•
•
•
•
Table 24: FMEA of the pressurized gas struts
Fire and explosion hazard associated with the compressed gas cylinder
Gas leak will cause the gas struts to malfunction
Struts failing resulting in the door to come crashing down
Doors not staying in the open position
Difficulty lifting the doors
The gas strut system becomes over compressed or overextended
Misalignment of the two struts used on the rear hatch
Extreme temperatures
Scissor Door Hinge Design
Function
The function of the vehicle scissor door is to open with a rotational motion in the vertical plane
to an angle which allows a user to comfortably enter the vehicle. Benchmarking research of
current vehicles demonstrating successful use of scissor doors proved to be of little use in design,
due to the fact that many of the automobile scissor doors weigh several times more than the
estimated door weight of the NEV. Many conversion kits are also available, which convert
standard passenger car doors into scissor doors. The mechanism by which most of these kits
operate is very uneconomical for the NEV application due to the constraints of motion imposed
80
by the door interface and latching of passenger cars not initially designed to optimize a scissor
door.
Considering the poor applicability of benchmarked scissor door systems, other options were
explored. The most strongly considered options are compared in Table 25. The 2 loop butt
hinge and 4 bar hinge are also displayed in figures 48 and 49.
Hinge Type
2 loop butt
3 loop butt
4 bar
pin & bracket
Table 25: Connection Comparison
Cost Effectiveness
Simplicity Reliability
4
3
5
2
3
4
4
3
1
4
1
2
4
4
4
4
Total
14
14
8
16
Figure 48. 2 loop butt hinge
Figure 49. 4 bar hinge
A pin and bracket connection device was chosen due to its effectiveness in meeting all of the
considered areas of evaluation. This connection is also the most effective in allowing for
removable doors, which will be necessary in order to meet ventilation specifications. The pin
and bracket rated well in the simplicity category, indicating that the cost of assembly would also
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be low. High simplicity combined with high effectiveness and low cost indicate that the pin and
bracket solution would have the greatest value to the design. For the hinge mechanism, the pin
will be in contact with the bracket surfaces without use of any bearing of bushing. Bearings and
bushings were found to be unnecessary due to the low speed and limited cycles of the door
opening operation. Common petroleum-based grease will be used as a lubricant to extend the
life of operation. A pin and bracket
type hinge may be observed in Figure 50.
Figure 50. Pin and bracket hinge
FMEA
Using mockups and detailed figures, a more complete understanding of the hinge mechanism
was attained. A detailed FMEA was performed using these resources. Following a group idea
generation session, several potential failure modes were identified. Table 26 shows several of
these failure modes with accompanying occurrence and severity ratings. The product of the two
ratings was then used to determine which failure mode resources should be allocated to.
Table 26: FMEA Ratings for Selected Failure Modes
System
Component
Failure Mode OCC SEV OCC*SEV
Mechanisms Scissor Door latching failure
7
5
35
Mechanisms Scissor Door
locking failure
7
4
28
Mechanisms Scissor Door
sealing failure
6
2
12
Mechanisms Scissor Door
leaking
8
2
16
Mechanisms Scissor Door
hinge failure
6
7
42
All failure modes were identified by the team. Subsequent rankings were determined after a
more detailed analysis was performed by the mechanisms group. Hinge failure was identified as
the failure mode with the greatest product of OCC and SEV, and subsequently was analyzed in
greater detail with use of a FMEA worksheet that can be found in Appendix C.
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Failure of the scissor door hinge could result in detachment from the vehicle. This would be a
catastrophic failure in a situation where weather protection is required. More importantly, the
failure could result in injury to the user or to others. Considering these factors, a severity rating
of 7 is given.
Due to the importance of the door to the system as a whole, both aesthetically and functionally,
the hinge will be designed in detail. Loads from the weight of the door and horizontal loads,
such as a person leaning on the door in the upright position, will be considered. Due to inability
to accurately model the system to simulate these loads, a safety factor of 4 will be used.
Considering the detailed design, high factor of safety, and the team’s lack of experience with
similar mechanisms, an occurrence rating of 6 was given.
No solutions have been identified as a means of avoiding this failure other than the relatively
high factor of safety and design for unintended loads. Testing of this hinge may reveal if the
design is adequate, or if the factor of safety should be increased or decreased. It is likely that
imminent failure would be recognized in advance through incorrect closing or sealing of the
door.
Safety is, of course, a top priority in the design of this mechanism. The most prevalent safety
concern is the potential risk of injury that may occur, should the hinge catastrophically fail. This
concern has been addressed by selecting a reliable connection type and by use of a high factor of
safety.
Design Analysis
Using a high spot estimate, the door weight used for all hinge calculations is 40 lbs. This was
determined by finding the predicted area of the door, and multiplying by the density for common
fiberglass body material and a thickness of ¼”, which gave 28 lbs. Then, an additional 13
pounds for the frame and latching mechanisms was added. The mass of window was neglected,
as it will be lighter than the fiberglass.
The center of gravity of the door was roughly estimated for analysis by finding center of volume
for the predicted door shape. According to this estimation, the center of gravity is found to be
approximately 20 inches from the pivot point of the scissor hinge. This estimate is considered
conservative, due to the fact that the entire door’s width is approximately 30 inches.
For analysis, the assisting strut is estimated to be placed at a distance of 2 inches from the pivot
point. The analysis is taken in the horizontal position, where the weight of the door creates the
greatest torque at the pivot point. Figure 51 illustrates the position of the door and the center of
gravity as used in the analysis. The gray area of the figure represents the vehicle frame where
the door will be attached.
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Figure 51: Dimensional Diagram
The resulting free body diagram can be seen in Figure 52.
Figure 52: FBD
Where F1 is the reaction at the pin, F2 is the force exerted by the strut, and the weight is a high
spot estimate of 40 lbs.
By summing torques about the pin, the reaction F2 can be found to be 400 lbs. Following a
summation of vertical forces, F1 is 360 lbs. F2 has the largest magnitude; therefore, stress
analysis will be taken at the bracket and pin which connects the strut to the door frame. All other
bracket and pin locations will have equal or less force applied. Stress analysis was performed
considering shear failure, tear out failure, and direct bearing failure. The purpose of the analysis
is to calculate the necessary width of the bracket, the width of the door frame support rod, the pin
diameter, and the thickness of the bracket between the pin hole and the edge. These dimensions
are depicted in Figure 53.
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Figure 53: Pin and Bracket Dimensions
Due to the fact that the strut is a two force member, we treat the force on the connecting brackets
as tension only, in order to determine tear out stresses. The stress analysis was then carried out
using the corrected areas for shear forces, bearing forces, and tear out stress. These calculations
can be found in Appendix D. Using a factor of safety of 4 and the material properties of 1020
cold rolled steel, the resulting required dimensions were found to be:
d > 0.20 in.
w > 0.16 in.
t > 0.20 in.
The factor of safety of 4 was used in response to the crude modeling and vague understanding of
all forces that could possibly be applied. AISI 1020 CR steel was chosen as a material for stress
analysis due to its moderately high formability, low cost, and high availability.
A horizontal force upon the door was also considered. This force may be a result of wind
blowing on the door when in its upright position, or a user pulling or leaning on the door when
not supported by the vehicle frame. As a rough estimate, the force applied is 10 lbs, applied
perpendicularly to the motion of the door, at a distance of 60 inches from the hinge. Weight of
the door was not considered in this analysis due to the small effect it has relative to the bending
85
force. 10 lbs was chosen as a reasonable force after measuring the force of a 160-lb person
leaning on a wall, by holding a scale on the wall perpendicular to the ground. This force is
meant to model a person leaning on the door in the upright position. The analysis is performed
about the pin and bracket where the door connects to the frame, assuming that the strut
connections will not support any of this load. The resulting FBD can be seen in Figure 54.
Figure 54: Horizontal Force FBD
Using a summation of torques, we find the resulting reaction forces in terms of width of the bar.
The calculations are then iterated several times, replacing due to the fact that width is used to
calculate R, then required width is found from the direct bearing equation. A factor of safety of
4 is again used, due to the crude model and unpredictable nature of the applied force. The
calculations for the following required dimensions can be found in Appendix D.
d > 0.350 in.
w > 0.489 in.
t > 0.196 in.
From this analysis, only thickness was a lesser value than the previous analysis. The substantial
increase in required width resulted in less thickness necessary to support the load. As a result of
the analysis, the following dimensions were chosen:
d = 0.50 in.
w = 0.50 in.
t = 0.25 in.
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The final pin and bracket design is depicted in Figure 55. The pin pictured will be held in place
by a cotter pin, which will allow for easy removal, should the user wish to remove the doors.
Figure 55. Pin and Bracket Design
The first analysis of the strut connection and the second analysis of the door-frame connection
were both considered in the selection of final dimensions, due to the fact that similar brackets
and pins will be used in each location in order to lessen the number of parts necessary for
production. Design of the hatch hinge and struts will also be performed to optimize use of
identical hinges and struts. The final dimensions were chosen because they met all required
dimensions from both analyses and are more readily available. The width of 0.50 inches will be
necessary for the bar supporting the door, however, the width of the bracket will need to be 0.25
inches as shown in the dimensioned mechanism figure. Following FEA of the hinge strut
mechanism, these dimensions will be verified.
The motion of the door and corresponding door body interface were also considered. Using
mock ups and range of motion analyses, it was determined that the door will need to open to
approximately 70 degrees in order to allow a passenger to easily enter the vehicle. The motion
of the door will be a 70 degree rotation upward from the pivot point at an angle of 15 degrees to
allow for clearance of the door-body interface. This arrangement can be seen in Figure 56.
87
Figure 56: Door Opening Angle and Interface
The areas within the red circles indicate that the interface angles will allow for the door to move
in a nearly vertical motion. The actual angles of these surfaces will be perpendicular to the door.
This arrangement and range of motion was verified using a mock up of the door. Precise
dimensions of the door-body interface will be determined with further use of mock ups and
detailed range of motion analyses. Figures 57 and 58 show what the door would look like as it is
opening and is demonstrated on the prototype vehicle.
88
Figure 57: Chase and Ryan Looking Dead Sexy Mocking-up the Door (Sorry I had to leave
this in here…)
89
Figure 58: Demonstration of the Motion of the Door
90
Figure 59: Sealing Surfaces
Figure 59 depicts the 4 different sealing surface regions. In the blue region the door will have a
lip extending inward, which will seal on top of the body sealing surface. The two yellow regions
will seal in the same manner which most automobile doors currently do. In the green region, the
door will have a sealing strip on the bottom surface, which will contact the upper surface of the
body interface as the door is lowered. Figure 60 shows the mock up of the sealing surfaces for
the prototype.
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Figure 60: Mock-up of the Sealing Surfaces
Impact on Door Frame
Failure of the door of the vehicle due to a high impact or a low impact situation that causes the
door to be unstable or unusable or to completely break apart is an undesirable situation. Figure
61 shows what the vehicle frame structure would look like along with the door frame. In the
case of an impact on the door frame the force of the impact would be transferred through the
door frame to the body of the vehicle. Most of the force would be transferred into the frame of
the body with some energy being exerted onto the door hinge and the door strut. This could
cause problems in that the door strut may not be able to function properly or the hinge may
become misaligned so that it can not be opened.
92
Figure 61: Frame of Door and Vehicle
Function
The likelihood of a high energy impact occurring is rather low when compared with other likely
failures but can result in passenger injury or even death. More likely impacts that may occur
with the vehicles doors include situations when the door is hit by a low energy force such as
hitting the car next to the vehicle or the parking meter. Impacts may also be the result of
someone running into the door accidentally or a minor traffic accident. A high energy impact is
most likely the result of an accident involving on the vehicle or another vehicle impacting the
vehicle from the side. For the vehicle high energy impacts will be considered to be an impact by
another vehicle at a speed of 25mph. This is justifiable in that most of the intended use of the
vehicle will be for low speed areas. Figure 62 is an example of a side impact test as preformed on
an automobile.
93
Figure 62: Simulated Impact on an Automobile
While the team may not be able to perform such extensive testing as demonstrated above the best
way to prevent side impact injuries is to be proactive during the design process. The door frame
and material will be researched and tested with respect to functionality, FMEA, safety, cost
comparisons, design for manufacturability, economics and testing.
Several benchmarked vehicles were researched for how they handled the prospect of side impact
and door frame failure. Global Electric Motorcars produces several models without any doors
and a few with doors. Researching the vehicles with doors revealed that most of the door frame
structures were either canvas doors or hard doors. Also the doors were an added feature for the
vehicle which in turn means a greater overall price for the vehicle. The canvas doors would be
worthless in the case of a side impact large or small; they may even rip or tear if impacted upon a
shape object at very low speeds. The hard doors for the GEM vehicles were constructed out of
lightweight ABS plastic material and were removable. The ABS plastic would offer a greater
resistance to low energy impacts then the canvas style doors but would still be questionable in a
high energy impact. The American Electric Vehicle’s Kurrent was also researched and it was
determined that the Kurrent comes standard with doors that are removable. The doors appeared
to be constructed out of a frame of some type of metal material that could not be determined and
covered with either plastic or fiberglass. This door frame structure offers great resistance to high
energy impacts and low energy impact without failure then the GEM vehicle.
FMEA
An FMEA design analysis was preformed on the likely failures to occur to the door frame. Some
of the failures included weathering of the material such as rust and wear, fractures and other
failures of the chosen material, failure at the joints or welds of the frame, and several failures that
may result from an impact. Some other potential failures included cyclic loading, vibration, poor
94
attachments with the body panels, poor seal with vehicle frame, deformation of frame, flexing of
the frame material, and the potential of the door falling off completely. The root causes of many
of the failures would be a result of a poor choice of material, poor manufacturing, poor care, and
improper use. The different failure modes were then rated with respect to probability and
severity of failure. It was determined that the most likely failure would be dents in the door or
misshaping of the door frame. The most serious failure would be failure to protect the
passengers in the case of an accident. Some other negative situations include allowing elements
into vehicle such as rain, unable to open the door, poor insulation, improperly shutting, and
breaking off from the hinge. The best way to avoid some of the failures involves the proper
selection of material for the door frame, preventive measures such as a dent resistant material,
and attention to detail during the manufacturing process. Several recommendations for the
reduction of the risks were also proposed and included the selection of a door frame constructed
out of metals such as steel, titanium, carbon fiber, or aluminum.
Design Analysis
It was decided within the team that the material selection for the door would be made with
consideration to several important factors that would affect the other systems of the vehicle
without compromising too much of the functionality of the door frame during an impact. Table
29 is a comparison of several different steels and aluminum alloys which were considered for the
door frame.
Table 29: Comparison of Material Properties
Carbon
Steels
Alloy
Steels
AISI 304
Stainless
Steel
Density (1000 kg/m3)
7.85
7.85
8
Elastic Modulus (GPa)
190-210
190-210
Poisson's Ratio
0.27-0.3
190-210
0.270.3
Thermal Expansion (10-6/K)
11-16.6
9.0-15
Properties
Melting Point (°C)
Thermal Conductivity (W/mK)
9.0-20.7
Aluminum
6061-T6;
6061-T651
7.728.0
7.85
2.7
190-210
0.270.3
9.415.1
1371-1454
24.365.2
Specific Heat (J/kg-K)
Electrical Resistivity (10-9Ωm)
130-1250
Tensile Strength (MPa)
276-1882
Yield Strength (MPa)
0.27-0.3
Tool
Steels
AISI 4130
Chromiummolybdenum
steel
450-2081
186-758
26-48.6
4521499
2101251
7581882
3661793
17.2
1432
19.948.3
420-500
42.7
167
477
75.7-1020
515
6402000
205
380-440
655
276
310
One of the considerations of the door frame material selection is the need for a material that does
not have a high thermal conductivity because of the focus on the development of a heating
95
system in the vehicle. This means that when the density and tensile strength are relatively equal
the deciding factor would be the thermal conductivity of the material. Three materials were
chosen based on density, strength, and thermal conductivity. The three materials to be further
compared were 6061 Aluminum, 4130 Chromium-molybdenum steel, and 304 Stainless Steel.
While weight reduction is an important factor in energy conservation for the vehicle it was
determined that the low strength of aluminum was not a good choice for door frame construction.
The 304 Stainless Steel has a higher density, thereby a higher weight then the 4130 Chromiummolybdenum steel however it has a greater tensile strength and a far better thermal conductivity
rating then the 4130 Chromium-molybdenum steel.
Design for Safety
The selection and construction of the frame would have a very high impact on the safety of the
door frame during an impact situation. Further calculations need to be preformed to find the
magnitudes of forces that the door frame would be required to withstand in an impact situation.
Economics/Value
The different costs of 304 Stainless Steel, 4130 Chromium-molybdenum Steel, and 6061
Aluminum are shown in Table 30.
Table 30: Costs of Desired Tubing
Wall
Thickness
Material
Type
OD
Gage
Decimal
AL 6061-T6
tubing
1.05"
SST 304
SST 304
tubing
tubing
1.05"
1.05"
SST 304
tubing
1.05"
Steel 1018
tubing
1 3/8"
Galvanized
tubing
1.05"
.113"
4130
Chromiummolybdenum
steel
tubing
1"
.065"
ITW
Cost
.113"
16
16
.065"
.065"
McMaster
MSC
Carr Cost
Cost
Tubing
Lengths
$ 3.30 / ft
6'
$ 7.86 / ft
10'
6'
$1.29 /
ft
$12.15
/ ft
0.120"
$ 3.07 /
lbs
6'
?
$ 2.30 / ft
6'
$ 2.75
/ ft
8'
These costs are for individual purchases and the prices would generally be less for purchases in
lots of 5000. The diameter of tubing was chosen with consideration for cost, weight, and
strength. The wall thickness of the tubing will directly affect the strength and weight of the
96
frame as well. One idea is to place foam insulation inside the tubing to better reduce the heat
transfer from the inside of the vehicle to the outside environment. The 4130 Chromiummolybdenum steel tubing was selected to be used for the final design based on price, weight,
constructability, and strength. The diameter of the tubing was selected to be 1 inch with a wall
thickness of .065 inches based on the prototype impact testing.
DFMA
The cost of manufacturing and assembly were another area that was considered for the
construction of the door frame. Some important considerations include construction time to
assemble the door frame and being able to maintain the strength of the frame members after they
are welded. When metals are welded sometimes they will lose some of their strength at the weld
location. Another important consideration that came from the DFMA process was the shape of
the door that would be used for the vehicle. The shape plays a very important role in how the
door hinge is used. With a scissor door the shape of the door frame has to be just right to allow
for easy entrance and exit and to allow for the full range of motion that is require. A mock up
was preformed to demonstrate how the hinge would be attached to the vehicle and door frames
and how the shape of the door would affect its movement. Some special factors that effect the
door frame design and construction are how the frame and the hinge will be attached, how the
body panels will be attached to the door frame and how the door will lock shut when in the
closed position. The seal between the door frame and the vehicle was another important factor in
the door frame construction. During the assembly process excess waste of manufacturing
materials and harmful environmental processes should be reduced or eliminated. Since the idea
for this vehicle is energy conservation, it is important that the assembly process also uses energy
conserving processes.
Testing/Mockups/Prototypes
A mockup of the shape of the door was useful for further design of a prototype and is seen in
Figure 59.
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Figure 63: Mock-up of the Door Shape
A prototype of the proposed door frame was constructed using the selected material and tested
with respect to low energy impacts. A further analysis of the frame design is discussed in later
sections.
Safety Belt Design
The selection of the seatbelt was base on several design methods. Table 31 is the FMEA that
was preformed with respect to the seatbelt.
Table 31: FMEA for the Seatbelt
Failure Mode
Severity
Probability Of
Occurrence
Breakage of Latch
10
1
Breakage of Mounts
10
1
Retractor Fails
7
2
Harness Too Rigid
3
3
Breakage of Latch
This failure mode refers to the buckle disconnecting from the tongue. The severity of this failure
mode is high. If the seat belt latch fails during a crash, the force on the driver upon impact is
increased dramatically, giving rise to chance of serious injury. A severity rating of 10 was
assigned. However, the probability of occurrence is low; this component should have a very high
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factor of safety of purchased from a legitimate manufacturer. A value of 1 was assigned for
probability of occurrence.
Breakage of Mounts
This failure mode is also severe. It refers to the failure that may occur when the end bracket,
retractor, or loop guide disconnects from the vehicle due to impulse. If the seat belt mounts fail
they will probably break suddenly, precipitating a sudden impact upon the driver or passenger.
Without knowledge of exactly how the mounts would break to release the seat belt, a severity of
10 should be assigned. The probability of occurrence is low, considering that the system will be
mounted to the vehicle with connections having a high factor of safety in comparison to their
expected force. A value of 1 was used.
Retractor Fails
The severity of this mode of failure is moderate. If the harness does not lock during a crash the
driver may not fly out of the seat, but could lean forward and hit the steering wheel or dash. A
severity rating of 7 was assigned. The probability of occurrence is small; it depends on what
acceleration the retractor is designed to lock under, and the strength of the locking mechanism
itself. The exact probability of occurrence will have to be judged from a particular product's
specifications, but is generally expected to be low. A value of 2 was used.
Harness Too Rigid
It was decided that too rigid of a harness will prevent the seat belt from performing its necessary
function of sufficiently slowing the driver's stopping speed upon impact. A sudden impact could
bring the driver to a stop within a distance of less than a foot. A harness which stretches a few
extra inches will increase the stopping distance, which proportionately decreases the force on the
driver. A rigid harness still adds considerable safety value, so a severity of 3 was assigned. The
probability of occurrence is taken to mean the probability that the driver could be injured in a
crash that would be prevented by a less rigid harness. This was also assigned a value of 3.
Design for Safety
The safety of the latch and retractor components of the safety belt will depend on the quality of
the system purchased from the manufacturer. The mounts will be connected in a manner which
will support a large tensile impulse. The material properties of the harness will be chosen so that
it decreases the amount of acceleration on the driver upon crashing, while also eliminating the
chance of collision with objects in front.
The component of safety which will be affected directly by our manufacturing process is the
connections used for mounts. To determine how strong they need to be, a force analysis is done
on the seatbelt, using a worst-case scenario. A 200 lb. male is assumed to stop with the car in a
distance of 1 foot from 30 miles per hour. A completely rigid seatbelt is also assumed. For this
set of assumptions, the force on the driver is his mass multiplied by his deceleration, calculated
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as approximately 6,000 lbf. This force will be distributed over at least two points of connection,
so each should withstand a 3,000 lbf tensile force.
Design for Manufacturability and Assembly
Mechanical fasteners are a good choice in terms of simplicity and cost of manufacturing. They
leave more freedom of choice in terms of when they are introduced into the assembly process
because they do not require as specialized of working conditions as welding or adhesive
bonding. Mechanical fasteners also need to be used whenever a part may need to be replaced or
repaired, and there is some chance that a problem could develop with the seatbelt retractor or
latch. Rivet-type fasteners will probably be used. The material and required dimensions will be
calculated when the specific orientation and locations of connections are determined from the
layout of the seating.
Seating
Function
Seating for the vehicle is constructed with consideration to the safety and comfort of two
occupants. A comfortable position is desired for both drivers and passengers of different sizes
and shapes. A safe design is needed to prevent injuries to occupants and damages to the seats. To
make sure these aspects are incorporated in the vehicle’s seating, FMEA and DFMA analyses are
conducted in order to make appropriate decisions on the seat design.
FMEA
An FMEA analysis of the seat involves both failure modes of the seat and failure in the seat’s
connection to the vehicle. Table 32 shows all conceived modes of failure.
Table 32: FMEA Analysis for Seating
System Component Failure Mode
Collapse
Interior Seats
Breakage of Mounts
Stuck/Failure to Adjust
Rust/Corrosion of Fasteners
Worn Out
The most prominent failure mode is the seat collapsing. Research has shown that most seat
failures occur during rear end collisions. The seats may totally collapse when occupants are
forced forward then slam back against the seat. Other times the seats partially collapse, turning
into a ramp that allows occupants to be ejected backwards. Both instances can cause bodily harm
and sometimes human loss of life. A thorough analysis is underway to understand ways of
designing the seats to prevent them from collapsing. It is recommended that the seat be tested for
adequate seat strength for rear impact. We will be considering designs that reduce the chances of
seat collapsibility.
100
Seat Design Analysis
Table 33: Conceptual Seat Design Rating (1-5)
Feature
Brad
Brandon
Camille
Chase
Damon
Jim
Kevin
Michael
Ryan
AVG
Bucket (separate) seats
4
4
3
4
4
3
2
4
3
3.44
Bench style seats
2
2
4
3
3
4
5
2
4
3.22
Seat w/ headrest
4
3
4
4
5
4
3
2
3
3.56
Seat w/o headrest
2
1
2
3
3
2
2
3
1
2.11
Adjustable Seat
4
4
3
5
5
4
5
5
5
4.44
Fixed Seat
3
1
2
2
3
3
4
2
2
2.44
Seat built by Goonies
2
1
1
1
1
2
1
1
1
1.22
Seat bought by Goonies
4
5
5
5
5
5
5
5
5
4.89
The team rated aspects of seating such as seat style, adjustability, whether or not to include a
head rest and building versus buying the seat (Table 33). After the rating, these aspects were
discussed by the entire team. Since the team was split between incorporating bucket or bench
style seats, further comparison of seat style is needed before making this decision. These
comparisons are shown in Table 34 and Table 35.
Table 34: Comparison of Bench Style Seats to Bucket Seats
Safety
Cost
Ergonomics
Style/Appeal
Assembly
Occupant
Fit
Compatibility
w/ Seatbelt
Designs
Adjustability
Bench
Seats
Limited
$100$400
(per
seat)
Limited
Limited/some
available
styles
few parts
Spacious
seating
Limited
Limited,
Affects all
occupants
Bucket
Seats
Designed
to
address
safety
$300$700
(for 2
seat)
Designed
to address
ergonomics
Many
available
styles
many
parts
Limited
seating
space
Many
compatible
designs
Several
types,
Affects
individual
occupants
101
Table 35: Build vs. Buy for Seat
Safety
Cost
Assembly
type
Ease of
Manufacturing
Features/Style
Compatibility
w/ Seatbelt
Designs
Build
fair - good
> $300
amateur
low - medium
custom made
high, flexible
design
Buy
good excellent
$100 $300
professional
medium - high
limited, addons cost extra
limited
Vehicle Fit
custom
made to fit
vehicle
May need
modifications
Dimensions of seating in relation to the vehicle were made by measurements taken from a golf
cart and adapted to our vehicle. The results are shown in Figure 64. Other methods included
comparing the seat design dimensions to those of benchmarked vehicles and measuring different
sized team members in the seated position.
102
Floorboard to Roof – 54”
Steering Wheel to Back of Seat – 20”
Length of Steering Column from Floorboard – 28”
Width of Bench Seat – 40”
15”
26”
23”
20”
15”
Figure 64: Dimensions of seat with respect to vehicle design
103
Seating Decisions
While bucket style seats offered more positive characteristics than bench style seats, it has been
acknowledged that the pros that bench style seats offered were important features to include,
such as lower cost in every aspect, more spacious seating in a small vehicle, and a 1 seat
assembly compared to the 2 bucket seats. It is still recognized that positive features from the
bucket seats like better safety and ergonomics must still be included in our seating. With this
knowledge and more research, we found that there are many styles of automotive seating that
incorporate aspects of both bucket and bench style seats.
A bucket back bench style seat will be bought and mounted to the vehicle with a simple
mounting system; i.e. by bolting it onto a box underneath of it. This seat will have one bottom
seat which allows for easy assembly and space for small cargo. It will also have the advantage of
two separate seat backs designed with lumbar support for personal space and comfort of the
vehicle’s two occupants.
Figure 65: Bucket Back Bench style Seat with Dimensions
7.1 Design Drawings, Parts List and Bill of Materials
Final Design
104
Figure 66: Final Design
Major Parts and Assemblies
Table 36: Sub-Assemblies w/ Associated Part Drawings
Sub-Assembly
Associated Drawing Numbers
Enclosure
Scissor Door Frame
Scissor Door Hinge
Rear Hatch
Cargo Drawer
Heater
Battery
ENC1 - ENC12
DR01 - DR12
BRKT01 - BRKT04
RH01 - RH05
CD01 - CD04
HB1
BB1 - BB2
Enclosure
Each enclosure panel will be fabricated using a mold. To achieve a smooth finish comparable to
that of an automobile body, the mold must have a superior, high-gloss surface with what is
known as a Class ‘A’ finish. Each part constructed in a mold with this finish will also have a
Class ‘A’ surface finish.
The tolerances chosen for the fiberglass panel dimensions are based upon the need for proper
sealing between panels and the positioning of the panels on the frame. Tight seals that are free
of large openings must be achieved at the panel joints to prevent leaking. In other words, a
maximum gap of 0.02” between panels may occur for the given tolerances. Rubber seals are
utilized to fill in these relatively small gaps to prevent any leaks. For assembly purposes, the
holes drilled into each panel must also be correctly positioned to allow secure connections to the
frame with screws.
105
Figure 67: Rear Hatch Enclosure Panel Part Drawing
106
Figure 68: Side Window Enclosure Panel Part Drawing
ENC11
ENC8
ENC6
ENC10
ENC12
Figure 69: Enclosure Assembly Exploded View
107
Table 37: Enclosure Sub-Assembly w/ Corresponding Part Numbers
Drawing Number
Drawing Description
Sub-Assembly Quantity
ENC1
Nose Panel
Enclosure
1
ENC2
Roof Pillar Panel - Left
Enclosure
1
ENC3
Roof Pillar Panel - Right
Enclosure
1
ENC4
Roof Panel
Enclosure
1
ENC5
Scissor Door Panel - Left
Enclosure
1
ENC6
Scissor Door Panel - Right
Enclosure
1
ENC7
Side Window Panel - Left
Enclosure
1
ENC8
Side Window Panel - Right
Enclosure
1
ENC9
Rear Quarter Panel-Left
Enclosure
1
ENC 10
Rear Quarter Panel-Right
Enclosure
1
ENC11
Rear Hatch Panel
Enclosure
1
ENC12
Rear Bumper Panel
Enclosure
1
Scissor Door Frame
The tolerances for the door frame dimensions were chosen to be ± 0.05”. This is due to the fact
that the tubing can be bent somewhat more when the subassemblies are welded together. There
is room for a small amount of error. However, the door frame as a whole needs to be flat with
respect to the vehicle so that it can be properly sealed. This is controlled using the jig with a
latch to hold the tubing down properly for the sub-assembly and final assembly.
108
Figure 70: Scissor Door Frame Part Drawing
Figure 71: Scissor Door Frame Assembly Displaying Location of Part DR01
109
Scissor Door Hinge
As shown in drawing BRKT01 given by Figure 72 below, the tolerance specified for all
dimensions of the bracket part, excluding the hole diameter, are ± 0.01”. This was chosen to
ensure that the bracket may be assembled properly to avoid misalignment issues of the pin that
must pass between them. The hole diameter was given a tolerance of 0.005” in order to avoid
clearance issues with the pin passing through the hole. The process of attaching the bracket
pieces to the frame will ultimately determine the alignment of the bracket, however, should the
brackets be grossly out of tolerance, alignment may not be possible.
Figure 72: Scissor Door Hinge Bracket Part Drawing
Figure 73 shown below depicts the two bracket pieces as they would be attached to the frame,
represented by the square block. The tolerance here for the vertical placement of the bracket
piece is 0.005” for each piece. This would allow for a total of 0.01” difference between the
alignments of the two pieces. A misalignment of this magnitude would not significantly affect
the motion of the door or its alignment with the sealing surface of the vehicle.
110
Figure 73: Scissor Door Hinge Bracket Assembly Drawing
BRKT01
BRKT04
BRKT03
BRKT02
Figure 74: Scissor Door Hinge Assembly
Table 38: Scissor Door Hinge Subassembly w/ Corresponding Part Numbers
Drawing Number
Drawing Description
Sub-Assembly Quantity
BRKT01
Hinge Bracket
Hinge
2
111
BRKT02
BRKT03
BRKT04
Flat Plate
Pin
Cotter Pin
Hinge
Hinge
Hinge
1
1
2
Rear Hatch
The tolerance for the length of the tubing is .025 inches. This allows for a maximum difference
in length between any two pieces to be .05 inches. There is a planned clearance of .1 inches
between the hatch frame and the surrounding vehicle frame, so the maximum allowable
deviation from the desired value should not cause the two frames to collide. The curved segment
of the part is defined by its radius of curvature and the angle it sweeps through. If either of the
two radii or angles of sweep are noticeably different, one end of the frame will be further into the
vehicle than the other, and the body may not seal properly. A difference in angle of sweep will
be amplified by the long, straight segment of the part. In order for the two ends of the parts to be
within .05 inches of a linear alignment, the angle of sweep must be within .0125° of 41°. The
offset from a linear alignment will also be equal to the difference between respective radii of the
members. The radii must be within .01 inches of the specified value. It is not important for the
hatch frame to meet a particular surface finish.
Figure 75: Rear Hatch Frame Side Bar Part Drawing
112
Figure 76: Rear Hatch Frame Bar Part Drawing
Cargo Drawer
113
Figure 77: Cargo Drawer Part Drawing
The cargo drawer is located in the back section of the vehicle on a base above the motor. The
drawer has dimensions of 36 X 18 X16 with a .25 inch wall thickness and a total volume of
738.6 in3. The drawer weighs 30 lbs when empty and can hold up to 65 lbs of cargo.
Heating System
Since the bracket is a simple part, the tolerances are relatively large. The bracket will be made
from 1020 cold rolled sheet metal. The heating system component will be able to fit properly
with these set tolerances. The angle tolerances are loose since the sheet metal is easy to
manipulate. A simple bending machine can provide the desired angles. They do need to be close
to 90 degrees in order for the heater to fit properly.
114
Figure 78: Heater Bracket
Battery Box
The battery box is part of the interior. It is located below the seat inside the car. This is a simple
part being made out of 10 gage ASTM-A366 cold drawn sheet steel. It will weigh around 65 lbs
and cost around $50. This product would be purchased from the HBSteel Company. The
tolerances that were assigned to the sheet metal were ± 0.020 inches. These values were chosen
because of the simplicity of the part. The only concerns are that there must be enough material
at the corners to have a proper weld and there must be enough metal to have the correct height
for the box after bending.
115
Figure 79: Heater Battery Box (Open)
Figure 80: Heater Battery Box (Closed)
116
Bill of Materials
Table 39: Bill of Materials
#
Part
Quantity
Description
2
3/4 oz. per ft Chopped Strand Fiberglass Mat, 38" wide,
0.020" thick
#77 Wax Free, General Purpose Polyester Molding
Resin
Weight
Cost
Subassembly
17.6 lb
$107.00
Enclosure
18.4 lb
$47.70
Enclosure
1
Fiberglass
42 yds
2
Resin
2 gal
3
Hardener
2.6 fl. oz.
#69 MEKP Hardener, Industry Standard
N/A
$1.27
Enclosure
4
Gel Coat
1 gal
#173 Super High Gloss Clear Gel Coat
8 lb
$57.49
Enclosure
5
Pigment
1/2 pt
Pigment - Resin Additive, Color Determined by
Application
N/A
$11.87
Enclosure
6
Hatch Frame
5 feet
CR Carbon Steel, 1" OD X 1/8" wall thickness
$15
Rear Hatch
7
Hatch Frame
10 feet
Bottom and top bars used to frame up rear hatch door
$30
Rear Hatch
8
Door Frame
38 feet
Entire Door Frame, 4130 Steel Tubing, 1" OD X .065"
Wall Thickness
.6576
lb/foot
.6576
lb/foot
.6576
lb/foot
$105.00
Door Frame
9
Heating
Bracket
1 piece
1020 CD Sheet metal, bent to hold heater
1.00 lb
$1.50
Heater
10
Hinge Bracket
2 pieces
1.8" long x 1"wide x 0.25" thick 1020 CR
.12 lb
$0.48
Door Hinge
11
Battery Box
1 piece
65.0 lb
$50.00
Batteries
12
Gas Strut
2
N/A
$10.89
Rear Hatch
13
Gas Strut
2
N/A
$10.89
Rear Hatch
14
Eyelet Fittings
8
.39” eyelet diameter, .39” thick, zinc
N/A
$2.27
Rear Hatch
15
Cam Latch
1
Handle 3 ¼” Lg. x 7/8” Wd.
N/A
$26.85
Rear Hatch
16
bracket
2
1.8" long x 1"wide x 0.25" thick 1020 CR
.12 lb
$0.48
Door Hinge
17
pin
1
0.5" dia x 1.25" long capped grade 5
.07 lb
$0.52
Door Hinge
18
cotter pin
1
0.0625" nom size, 0.12 Head dia., 0.03 prong
.01 lb
$0.08
Door Hinge
19
washer
2
0.5 regular grade 8
.02 lb
$0.41
Door Hinge
20
Top
1
ABS pellets, injection molded, (36X18X0.25)
6 lb
21
Drawer
1
ABS pellets, injection molded, (36X18X16)
30 lb
22
Hinge
2
Steel Take-Apart Hinge, hardware source
N/A
23
Latch
1
24
Handle
1
$
1.65
$
8.24
$
5.42
$
0.63
$
4.38
Cargo
Drawer
Cargo
Drawer
Cargo
Drawer
Cargo
Drawer
Cargo
Drawer
10 gage ASTM-A366 Cold Drawn sheet steel, vender
HBSteel Comp.
40 lb force, 13.74” extended lg., 8.27” compressed lg.,
5.47” stroke lg., steel
90 lb force, 13.74” extended lg., 8.27” compressed lg.,
5.47” stroke lg., steel
Nonlocking polypropylene draw latch, Mcmaster
#1891A48
Rectangular grip handle with threaded holes (screws
included), Mcmaster #1661A39
117
N/A
N/A
Cargo
Drawer
Cargo
Drawer
Cargo
Drawer
Cargo
Drawer
25
Slide
2
16" accuride C3832-C16SCP drawer slide
N/A
$16.72
26
hinge screw
4
#4 pan head screws
N/A
$0.06
27
latch screw
4
#2 screws
N/A
$0.08
28
handle screw
2
(included with handle)
N/A
$0.00
29
Seat
1
bucket back bench seat
N/A
$440.00
Seat
30
Bolts
1
Standard Hex Cap Screw McMaster # 92190A155
N/A
$3.66
Seat
7.2 How does it work?
Basic Operation
The campus/community transporter operates in a manner similar to existing Neighborhood
Electric Vehicles (NEVs) or the typical golf cart. The owner/user utilizes a standard key to
unlock the scissor door or rear hatch to gain entrance into the vehicle or access to the cargo.
Once inside, the driver places the key into an ignition switch and rotates it to turn the vehicle on.
A drive selector, with forward, neutral, and reverse positions, is used to choose the direction of
travel. With the vehicle in forward/reverse mode, the operator presses the long and slender,
right-hand pedal downward to accelerate the vehicle forward/backward. A short and wide pedal
on the left-hand side controls the braking mechanism which may also be locked in place for
parking. A standard steering-wheel is used to direct the vehicle’s course of travel.
With the key in the “on” position, the headlights, interior lights, dashboard controls, heater and
ventilation, and other accessories may be operated by their respective switches/knobs which are
clearly labeled with words and/or symbols.
The transporter has a range of travel around 30 miles. However, to avoid over-draining the
batteries for the propulsion system, it should not be operated to this limit. The range is highly
dependant on the operating conditions such as temperature, batteries’ state of charge, road
conditions, accessory usage, and many other factors. A battery charge indicator will give the
approximate level of charge but should only be viewed as a ballpark estimate.
Scissor Door Opening and Closing
The scissor door on the vehicle has the ability to be easily opened and closed by even a young
child, as demonstrated with the prototype on demonstration day. The door will be assisted by a
strut so it will be able to be opened to any position and will not fall back on the user. Also, the
strut will be employed so that the door does not open rapidly and hit the user when the locking
mechanism is released. Figures 81 and 82 show the scissor door in the open and closed
positions, respectively.
118
Figure 81: Scissor Door in Open Position
Figure 82: Scissor Door in Closed Position
Getting Into the Vehicle
In order to get into the vehicle the operator will need to first step up to the vehicle and place
there hand on the door handle. This handle will be very similar to door handles on current
automobiles and will operate in the exact same manner. The user will place their hand under the
handle and pull the handle towards their body. This will release the latching mechanism and the
door will move up and out a bit. The user will then lift the door slowly up and towards them
with the assistance of the strut. Once the door reaches its fully open position the user can step
into the vehicle and sit down. The user will then pull the door down and towards them until it
reaches the latching mechanism. The user will pull the door fully shut so that the latch engages.
Figure 83 shows a person preparing to enter the vehicle.
119
Figure 83: Person Preparing to Enter the Vehicle
Getting Out of the Vehicle
To exit the vehicle the user will place their hand on the handle and pull it towards them. This
action will release the latching mechanism and the door will open slightly. The user will then lift
the door up and away from the vehicle. Once the door reaches its fully open position the user
can step out of the vehicle and turn around. The user will then pull the door down and towards
the vehicle until it reaches the latching mechanism. The user will pull the door fully shut so that
the latch engages. The user may then insert their key and lock the door.
Scissor Door Removal
The vehicle door is secured to the frame via two removable pins. One pin connects the door to
the hinge bracket. The other connects the strut to the door frame. In order to remove the door,
the door must be in the upright (open) position.
The two cotter pins are placed through holes in each of the pin ends in order to prohibit the pin
from sliding out of the hinge. An image of the pin – cotter pin assembly can be seen in Figure
84.
120
Figure 84. Hinge Pin and Cotter Pins
In order to remove the pins from the holes, the cotter prong must be straightened and then
removed using pliers. After the cotter pins have been removed, the hinge pins may also be
removed; this may require a hammer and punch if they are bound. After removing the hinge pin
and the pin connecting the strut to the frame, the door may be lifted away. It is recommended
that a second person supports the door while the pins are being removed in order to avoid
possible injury.
Standard pliers and a small punch are the only tools required to remove the hinge pins. Should a
punch not be available, a screwdriver will suffice. If the door is frequently detached and
reattached, replacement of the cotter pins may be necessary. Additional pins will be included
with vehicle and are available at hardware stores.
Rear Hatch Operation
A 180° Turn Compression Cam Latch with a T-Handle will be used to open and close the rear
hatch door. The cam latch will keep the vehicle frame and door frame locked together. When the
user turns the T-handle, the cam will lose contact with the frame and the door will open. To open
the rear hatch door the user should grip the t-handle located at the bottom and in the center of the
door. Next, the user should proceed to turn the handle 90° to the left. Once the user turns the
handle, the door will unlatch. When the door is unlatched both the handle and cam will be
parallel to the edge of the door.
To latch the door, the user should grip and turn the t-handle 90° to the right. Once the user turns
the handle, the door will latch. When the door is latched both the handle and cam will be
perpendicular to the edge of the door.
The rear hatch is attached to the vehicle with two mortise hinges, connecting the top of the hatch
to a crossbar on the vehicle. The hinges allow the hatch to rotate in the vertical plane. The user
should lift the hatch by the handle at the bottom, pulling it up and away from the vehicle until it
121
is fully open. The hatch will be high enough in the fully open position for an approximately 6
foot person to stand underneath it. To close, the hatch should again be grasped by the handle, and
rotated back into the vehicle. The hatch frame will settle inside the vehicle frame, and its motion
will be halted by a stopper piece sitting immediately inside the vehicle. It is not necessary to
slam the hatch shut. The weight of the hatch is supported by two struts which allow it to open
and close by applying no more than about 5 pounds of human force. It will remain motionless
when fully open or closed, but the user should be aware that the hatch may move upward by the
struts if it is partially opened. Figures 85 and 86 show the rear hatch in the open and closed
positions, respectively.
Figure 85: Rear Hatch in Open Position
Figure 86: Rear Hatch in Closed Position
Cargo Drawer
As shown in Figure 87, the cargo drawer is manually pulled open and pushed close like a
common dresser drawer. After pulling open the rear hatch of the vehicle, a handle on the front of
the drawer is used to pull the drawer out from the back of the vehicle. Items can then be placed
in or taken out of the drawer with ease. The drawer slides back into the vehicle with a simple
push by the occupant.
122
Figure 87: Cargo Drawer Extended from Cargo Area
Seating
The seat is made to comfortably hold two occupants. The occupants open the scissor doors, and
step into the vehicle while gradually coming into a seated position onto the seat. The seat is
reliable and has an adjustable back.
Heating System
The vehicle’s climate control functions to heat the vehicle in cool weather, defrost the
windshield, and help ventilate the cabin on warmer days. An electrical resistance heater (24V
Back Seat Heat Plus) is the primary heat source and is powered by two batteries wired in series.
This system is easy to operate and is virtually maintenance free.
All of the controls for the system are located on the face of the heater, see Figure 88, which
allow the operator to select whether to heat or ventilate the cabin. A variable thermostat is also
included, which permits the heat output to be adjusted by the operator. To defrost, the heat
output is directed into the windshield by rotating the heater. The heater is able to rotate a
maximum of 30 degrees from the normal operating position.
123
On/Off Switch
Variable
Thermostat
Figure 88: Heater Controls
Although both the heater and the vehicle's propulsion system are electrically powered, the
heaters batteries are independent of the propulsion system. Operating the heating unit will have
no effect on the performance of the vehicle.
Maintenance
Heating System
While the heating system is virtually maintenance free, there are two items that should be
inspected every six months to ensure safe operation. For optimum performance and safety, the
air intake ducts of the heater should be clear of any obstructions and therefore need to checked
for dust and foreign objects, see Figure 89. In addition, the battery terminals are susceptible to a
corrosive buildup, most commonly on the positive terminal, which should be cleaned off with a
wire brush. Left unchecked, the build up will cause a poor connection and ultimately disable the
system. Do not attempt to add water to the batteries. These are sealed batteries and require no
maintenance other than inspection of the terminals. If the performance of the heater becomes
degraded, it is an indication that the batteries need replaced. This degraded performance
includes, lower heat output, shorter operational time between charges, and difficulty maintaining
a charge.
124
Heating Unit
Re-Circulation
Opening
Exterior Air Vent
Figure 89: Location of Air Intake Ducts
Battery Removal/Installation and Maintenance
The Optima batteries will be placed within the battery box before the vehicle is sold to
consumers. For maintenance purposes, the batteries may have to be removed from time to time
for inspection and/or replacement.
Every 6 months, the user should check for any visible damage to any wiring, terminals, or to the
batteries. The user should also check to make sure that all of the terminal connections are tight,
secure, and free of corrosion.
Battery Charger Recommendations
The Optima D51 batteries have specific charging requirements. These requirements can be found
at the Optima website. A copy of these requirements will also be supplied to the consumer.
For simplicity and ease of use, it is recommended that a high quality battery charger be used.
There are many battery chargers available, but the microprocessor controller chargers offer the
most advantages. These battery chargers can be set up to operate completely within Optima’s
specifications. A battery charger of this nature would provide the user with the best means of
charging and maintaining the vehicle’s batteries. Microprocessor controlled battery chargers are
an expensive initial investment, but in the long run, they enable the batteries to retain better
performance and longer operating lives. Regardless of the type of battery charger used, all
manufacturer’s specifications for the batteries and battery charger should be strictly adhered to
prevent injury and battery damage.
7.3 How is it made?
A design may look phenomenal on paper and may get great feedback from potential customers
however the design is worthless if it can not be manufactured easily. The job of engineers is to
125
constantly get feedback not just from customers but also from the manufactures that are building
and assembling the final design of a product. This feedback plays a very important role in the
further refinement of any design. The following section will introduce the preferred method by
which many of the previously shown parts are to be made. The descriptions given coupled with
the part and assembly drawings will give adequate information for complete part fabrication and
assembly of the vehicle’s subsystems.
Fiberglass Enclosure Fabrication
Composites may be produced by a number of methods including manual lay-up, automated layup, spray-up, filament winding, pultrusion, and resin transfer molding. Although all of these
processes will not be explained in detail, it is important to know that there are a variety of ways
to produce fiberglass and other composites. The fiberglass enclosure for the transporter is
produced by a commonly used manual wet lay-up procedure.
Some of the materials used throughout the fiberglass fabrication process are hazardous and
present safety concerns. Appropriate safety precaution should be taken to protect those in
contact with these fabrics and substances during all phases of the procedure. General guidelines
are given in the Design for Safety portion of the Enclosure Decision contained in Section 7.0.
(Note: The pictures below depict portions of the fabrication process for the prototype. However,
a non-hazardous resin was used. Appropriate safety gear should always be worn when working
with any of the hazardous materials associated with fiberglass.)
The manual lay-up process begins by cutting the fiberglass reinforcement to the appropriate size
and shape for the part being produced. This procedure can be observed in Figure 90. Four layers
of reinforcement are required for each panel. This is in the form of a ¾ ounce per ft2 chopped
strand mat. Chopped strand mat is made of small strands of fiberglass held together loosely with
a binder. This material saturates quickly and can be made to fit contours unlike heavier mat or
fabrics. The fiberglass may be cut using knives, scissors, disk cutters, power shears, rotary
power cutters, saws, or lasers. Multiple pieces of mat may be used to make one layer of a
laminate. The pieces should overlap no less than one half of an inch to ensure part strength and
proper bonding.
126
Figure 90: Cutting Fiberglass Reinforcement to Desired Shape and Size
The enclosure panels are constructed by layering the saturated reinforcement on the inside of a
mold with the desired part shape. A total of at least 12 molds, one for each panel, are required to
produce the entire enclosure. However, multiples are needed for production in lots of 5000 per
year. Molds may be made of various materials including steel, aluminum, nickel, copper, or a
composite. The surface of the mold will affect the surface finish of every part. So, the mold
surface must have what is known as a Class ‘A’ surface finish. This type of finish requires
detailed inspection and a great deal of polishing of the mold surface. This will give every
laminate that comes out of it the same smooth finished surface. This also reduces the amount of
finishing work needed. The mold is coated with a parting wax to create a durable high-gloss
surface. Before part fabrication, a release agent, such as polyvinyl alcohol (PVA), is applied in
thin coats to the mold to allow the removal of the fiberglass after curing. The application of a
release agent is depicted in Figure 91. This may also be applied by spraying a mist onto the
mold.
127
Figure 91: Application of a Release Agent onto the Mold
A specially formulated layer of resin, known as a gel coat, is then applied to the mold and
allowed to become tacky. A high-gloss gel coat is required to give the enclosure panels the
desired finish. This may also be sprayed onto the mold. Figure 92 shows a gel coat being
applied manually into the mold with brushes. Pigment is added to this layer to give the part
color. Pigments are available in a wide range of colors and types.
128
Figure 92: Manual Application of a Gel Coat onto the Mold
A polyester molding resin is used for this method of fabrication. 1% (by weight) of methyl ethyl
ketone peroxide (MEKP) hardener is added to the resin prior to impregnating the reinforcement.
It is a catalyst used to promote curing of the part.
After mixing the resin, a layer of the pre-cut fiberglass reinforcement is laid on a flat surface and
saturated with the resin mixture. This is done by pouring the mixture directly on to the mat and
spreading it with a brush or finned roller. The saturated mat is then placed into the coated mold.
Successive layers are similarly laid, and rollers are used to compact the layers and remove any
trapped air. The presence of air pockets can reduce part strength. If a particular thickness is
desired, additional layers may be added. This is known as a wet lay-up process since the pieces
are saturated when placed in the mold.
Once the part has cured, soft wedges may be used to remove it from the mold. A number of
these are placed around the perimeter and slowly hammered between the part and mold.
Usually, parts are designed with draft to allow easy removal from a mold. However, the panels
for the enclosure were not designed with draft because they are not totally rigid. Also, none of
the enclosure panels have a shape that necessitates draft. The flexibility of these panels will aid
in their removal.
129
Fiberglass may be machined by many of the methods used for metals. Although the mold will
control many of the panel dimensions, any excess material is trimmed from each panel. Final
machining of a fiberglass part is shown in Figure 93. Cutouts are made and holes are drilled to
the specifications found in their respective part drawings (ENC1-ENC12).
Figure 93: Final Machining of Fiberglass Part
Before another part is made, the mold is inspected. Repairs are made to the mold surface as
needed. Otherwise, the release agent is applied and the process is repeated. The details for the
enclosure fabrication process are given in Table 40.
130
Table 40: Production Cost Details for Enclosure Fabrication
Cost Details for Enclosure Panel Fabrication (one-at-a-time Production, 8 Hour Shift)
Operation 1
Operation 2
Operation 3
Operation 4
Cut fiberglass
fabric to
required
shape for
specific
panel, mix
resin, and
prepare mold
with gel coat
Apply
laminating
layers to
mold and
saturate with
resin
Final sanding
and
machining of
cured panels
Inspection,
cleanup, etc.
for the 8 hour
shift
a. Total time to complete operation(s) in hours
0.5
0.25
0.25
0.5
b. Labor rate for the operation (hourly)
$12
$12
$15
$12
c. Labor cost = a·b·(4 laborers)
$24
$12
$15
$24
1
1
1
1
0.5
0.5
0.5
0.5
0
0
0
0
$60
$30
$37.50
$60
$225.33
N/A
N/A
N/A
Four laborers are required for each operation, per
enclosure, for the enclosure panel fabrication process for
one-at-a-time production.
d. Basic overhead factor
e. Equipment factor
f. Special operation/tolerance factor
g. Labor/overhead/equipment cost = c·(1+d+e+f)
h. Purchased materials/ components cost
Total Cost = $412.83
Fiberglass Enclosure Assembly
The assembly of the fiberglass enclosure begins with the attachment of the acrylic windows,
latches, and other supplementary parts to the appropriate panels. To avoid cracking, the
windows may be bonded to the fiberglass with a strong adhesive that is safe for use with both
materials. Latches, lighting, and other devices are connected to the panels with properly-sized
nuts and bolts.
Each panel of the enclosure is then attached to the frame. The windshield will also be installed.
The details for this production process are given in Table 41.
131
Table 41: Production Cost Details for Enclosure Assembly
Cost Details for Enclosure Subassembly (Assembly Line Production, 8 Hour Shift)
Operation 1
Operation 2
Operation 3
Two laborers are required for each operation, per
enclosure, for the enclosure assembly process for
assembly-line production.
Attach
acrylic
windows and
door/hatch
latches and
hinges to
necessary
enclosure
panels
Attach
enclosure
panels to
frame, bond
insulation,
and install
windshield
Inspection,
cleanup, etc.
for the 8 hour
shift
a. Total time to complete operation(s) in hours
0.25
0.5
0.25
b. Labor rate for the operation
$12
$12
$12
c. Labor cost = a·b·(2 laborers)
$6
$12
$6
d. Basic overhead factor
1
1
1
e. Equipment factor
0.5
0.5
0.5
f. Special operation/tolerance factor
0
0
0
g. Labor/overhead/equipment cost = c·(1+d+e+f)
$15
$30
$15
h. Purchased materials/ components cost
$181
$160
Total Cost = $401
Scissor Door Frame
Part DR01 is the bottom portion of the subassembly DR-A of the door frame for the vehicle.
The whole door frame assembly as part of the vehicle was previously shown in Figure 71. The
frame subassembly DR-A is given in Figure 94 and part DR01 in Figure 95.
Figure 94: Scissor Door Frame Subassembly DR-A
132
Figure 95: Scissor Door Frame Part DR01
Part DR01 will be constructed using 4130 Chromium-molybdenum Steel tubing with a diameter
of 1 inch and a wall thickness of .065 inches. The dimensions for the part are given in the part
drawing in section 7.1. For the part to be constructed, it will first be cut to a length of 6 feet
using a horizontal band saw and then placed in the bending machine. Three bends will be added
to the tubing to form the shape that is desired. All the bends must be correctly completed so that
when the part is laid on its side it is completely flat. The bends will be completed using a jig that
will allow for the operator to consistently produce the same bends. The first bend will be made,
as seen in Figure 96, and then a part will be added to the jig, as seen in Figure 97, so that the
second bend can be completed. After the second bend is completed another piece will be added
to the jig, as seen in Figure 98, and the third and final bend will be made. The part will then be
welded to parts DR02-05 which are all placed in a jig to form subassembly DR-A. The
subassembly will then be welded to the other subassemblies in a jig and the door frame will be
complete.
Figure 96: DR01 Initial Jig, with Arrow Showing Direction of Force
133
Figure 97: DR01 Jig with Addition for Second Bend, with Arrow Showing Direction of
Force
Figure 98: DR01 Jig with Addition for Final Bend
Table 42 is an example of what the assembly of the door frame may cost during production in
lots of 5000.
134
Table 42: Production Cost Details for Door Frame Construction
Operation 1
Cuts bar stock
to length and
makes bends
on bender
Operation 2
Places cut
pieces in jigs
for the
welder and
removes the
welded
frame from
the jigs
Operation 3
Operation 4
Operation 5
Operation 6
Tack and
finish
welding of
prepared
pieces in the
jigs
Attach hinge
and door
lock, secure
to body
frame
Install
insulation,
body panels,
and windows
Inspection,
cleanup
.5 hour per
door
.25 hour per
door
0.5 hour per
door
0.5 hour per
frame
1 hour per
door
0.5 hour per
frame
b. labor rate for the
operation
$12/hr
$12/hr
$15/hr
$12/hr
$12/hr
$12/hr
c. Labor cost = axb
$6
$3
$8
$6
$12
$6
d. basic overhead factor
1
1
1
1
1
1
e. Equipment factor
0.5
0.5
0.5
0.5
0.5
0.5
f. Special
operation/tolerance factor
0.25
0
0
0
0
0
g.
labor/overhead/equipment
cost = c x (1+d+e+f)
$16.50
$7.50
$18.75
$15.00
$30.00
$15.00
h. purchased
materials/components cost
$105
$0
$0
$0
See Body
Panel section
$15
a. total time to complete
operation(s) in hours
Total cost for two door frames per vehicle: $450
Scissor Door Hinge
The scissor door hinge bracket will be manufactured as two separate pieces. Then, it will be
welded to a small flat plate attached to the vehicle frame. The assembly previously shown in
Figure 74 depicts the arrangement and indicates the bracket piece which the forthcoming
discussion pertains to.
Each of the brackets will be produced via a punching operation using 0.25 inch AISI 1020 cold
rolled sheet stock. The punching operation would be the most efficient for producing a great
number of identical parts out of a relatively thin sheet of metal. Punching will allow for
minimal post processing. This is due to the fact that relatively close tolerances can be held in
punching machines. The details of the hinge construction process are given in Table 43.
135
Table 43: Production Cost Details for Door Hinge Construction
Operation
4
Operation
5
Operation
6
Tack and
finish
welding of
prepared
pieces in the
jigs
Attach
hinge to
vehicle
frame
Join door
and frame
hinge
pieces and
insert pin
Inspection,
cleanup
0.25 hour per
vehicle
(4 hinges)
0.25 hour per
vehicle
(4 hinges)
0.5 hour
per
vehicle
(4 hinges)
0.75 hour
per vehicle
(4 hinges)
0.25 hour
per vehicle
(4 hinges)
$12/hr
$12/hr
$15/hr
$12/hr
$12/hr
$12/hr
$1.20
1
$3.00
1
$3.75
1
$6.00
1
$9.00
1
$3.00
1
e. Equipment factor
0.5
0.5
0.5
0.5
0.5
0.5
f. Special
operation/tolerance factor
0.25
0
0
0
0
0
$3.30
$7.50
$9.38
$15.00
$22.50
$7.50
$15.00
$0
$0
$0.00
$2.00
$0
a. total time to complete
operation(s) in hours
b. labor rate for the
operation
c. Labor cost = axb
d. basic overhead factor
g. labor /overhead
/equipment cost = c x
(1+d+e+f)
h. purchased
materials/components cost
Operation
1
Operation
2
Punches
bracket
pieces
from 0.25"
sheet
Places cut
pieces in jigs
for the welder
and removes
the bracket
assembly
0.1 hour
per vehicle
(4 hinges)
total cost
$80.18
Operation
3
per vehicle
Rear Hatch
A supply of one inch diameter, 1/8 inch thick cold rolled steel will be ordered for manufacturing
the frame for the rear hatch. It only requires the assembly of two types of parts: straight and
curved members. Skilled laborers will perform the following manufacturing processes.
The construction process for a curved member begins with cutting the tubing to the correct
length with a horizontal band saw. A grinding wheel will be used to remove burrs and sharp
edges. The end of the bar will be bent to a specified radius through a particular sweep.
The top and bottom steel bars of the rear hatch are also made by first cutting bar stock to length,
specified in the appropriate part drawing, with a horizontal band saw. A jig is used to obtain a
precise cut for each piece and to forego measuring before every cut. Burrs and sharp edges are
once again removed from the cut pieces with a grinding wheel. A CNC milling machine or
vertical band saw may be used to cut the semi-circles at the ends of each of the pieces. The
bottom steel bar will be bent according to the appropriate part drawing.
Once all of the parts of the rear hatch frame have been cut and bent to specifications, they are
fixed in a jig and welded together. Once the frame has been welded together the hinges and strut
136
brackets will be welded to the frame. Table 44 provides a breakdown of the production cost for
the rear hatch frame subassembly.
Table 44: Production Cost Details for Rear Hatch Frame Subassembly
Operation 1
Cut bar stock
to length and
make bends
according to
the correct
drawing.
a. total time to complete
operation(s) in hours
Operation 2
Place the cut
pieces in the
jig to be
properly
welded
together.
Also remove
the welded
frame from
the jig.
Operation 3
Operation 4
Operation 5
Tack and
finish weld
the cut
pieces that
were placed
in the jig.
Weld the
hinges and
strut
brackets to
the door
frame.
Inspect and
cleanup
.5
.25
0.5
0.5
0.5
b. labor rate for the
operation
$12/hr
$12/hr
$15/hr
$12/hr
$12/hr
c. Labor cost = axb
$6
$3
$7.50
$6
$6
d. basic overhead factor
1
1
1
1
1
e. Equipment factor
0.5
0.5
0.5
0.5
0.5
f. Special
operation/tolerance factor
0.25
0
0
0
0
$16.50
$7.50
$18.75
$15
$15
$45
$0
$0
$0
$0
g. labor/overhead/equipment
cost = c x (1+d+e+f)
h. purchased
materials/components cost
TOTAL COST: $118
Cargo Drawer
To make a cargo drawer and lid, ABS plastic pellets (shown in Figure 99) are melted to a
specified melting temperature between 218-262°F and injected into two molds; one designed for
the box shape of the cargo drawer and the other a hollow rectangular block designed for the lid.
Once the ABS is fully cooled and solidified, the molds are removed. The drawer and lid are trued
to remove extra material. Every few parts are measured to make sure they are the correct size
within the ±0.06 tolerance. This general tolerance is for molds with dimensions that are over 11.8
inches and is required for the drawer and top to properly align
137
Figure 99: ABS plastic pellets
Figures 100, 101, and 102 show the needed attachments to fully construct the cargo drawer. A
rectangular handle is attached to the front of the drawer and screwed into place. The drawer and
lid are then aligned. A hinge joins the back of the drawer and lid while the latch attaches the
front of each part.
Figure 100: Handle
Figure 101: Latch
Figure 102: Take-Apart Hinge
Two drawer slides (Figure 103) are screwed to the bottom of the drawer. The bottom half of each
slide is screwed into the floor board of the cargo area. The fully assembled cargo drawer easily
slides in and out of the rear of the vehicle.
Figure 103: Drawer Slide
The estimated cost for manufacturing the cargo drawer can be seen in below Table 45.
Table 45: Cost of Manufacturing Cargo Drawer
Operation Operation 1 Operation 2 138
Operation 3 Operation 4 total time to complete operation(s) in hours Injection Mold Drawer and Top Remove excess material Inspection, cleanup, etc. Assemble Parts 0.5 0.17
0.17 0.1
$12.00 $12.00
$12.00 $20.00
$6.00 $2.04
$2.04 $2.00
basic overhead factor equipment factor 1 0.5 1
0.5
1 0.5 1
0.5
special operation / tolerance factor 0 0
0 0
labor / overhead / equipment cost = 5 x (6 + 7 + 8) $15.00 $5.10
$5.10 $5.00
purchased materials / component costs Sum of total costs $37.18 $67.38 $336,900.00 labor rate for operation labor cost = (3 x 4) Annual cost at
5,000 units
Heater Bracket
The heater bracket physically attaches the heating unit to the dash board of the vehicle and
allows the heater to rotate up to 30 degrees. The bracket is made from 20 gauge 1020 steel.
Steel is used because it is able to withstand elevated temperatures, is easy to work with, is
relatively cheap, and its strength will easily keep the unit secure. The raw metal for the bracket
is estimated to cost $1.50 and weighs 1 pound. For lots of five thousand, the heater bracket,
given in Figure 104, is stamped out with the two hole features. The estimated process cost is
$1.0. A stamping process is fully capable of maintaining the specified tolerances.
139
Figure 105: Heater Bracket
Once the bracket is stamped and pressed into shape according to the specifications, it is attached
to the vehicle via a spot welder. The center of the bracket is 3.5 inches back from the front of the
dashboard and is welded to the bottom vent. Figure 106 shows the heater and bracket assembled
in the dashboard of the vehicle. The total time to attach the bracket is estimated to take 5
minutes and cost $2.00 for labor.
Figure 106: Heater & Bracket Assembly
Battery Box
The battery box has the main function of being the support structure for the 10 batteries required
to operate the power-train, provide auxiliary power, and to power the heating/ventilation system.
The battery box needs to be strong and rigid so that it provides protection for the occupants from
battery hazards. It should also shield the batteries from the elements. The battery box is designed
to be located under or behind the vehicle’s seat. The Solid Edge rendition of the battery box can
be found in Figure 107.
140
Figure 107: The Completed Battery Box
The box is to be made out of the sheet steel of gage and type as described by part drawings BB-1
and BB-2. To begin, the box will have to be trimmed from a 48”x72” steel sheet to the size and
specifications found within part drawing BB-1. This could be accomplished by many means.
Some options could include plasma cutters and hydraulic or manual sheet metal shears. The
cutting method will primarily depend on how the machine shop that will be producing the battery
box is equipped. For lots of 5,000, a hydraulic sheet metal shear would be the best option. A
hydraulic shear would be much more capable of mass production and would reduce the amount
of costs and skilled labor required.
The next step would be the drilling of the four holes that are described within the BB-1 part
drawing. These holes require loose tolerances and only serve the purpose of eliminating sharp
edges after the walls of the box are bent. The holes provide an effective corner treatment for the
sheet metal at a two bend corner.
Now, the long walls of the battery box should be bent. Once the long walls are bent, the four
welding tabs located on the short walls should be bent. The two short walls should then be bent
to form the box found in Figure 107 above. All of the tolerances and dimensions after the walls
and tabs are bent can be found in part drawing BB-2.
For a production run of 5,000 units per year, it would be advisable to find a machine shop
equipped with a hydraulic press brake. If such a brake were located and used, costs could be
reduced and production quantity could be increased. While there is a chance that the dies
required for the press brake may have high initial costs, these overhead costs can be offset by the
high production rates that could be attained. It is also possible that moderately skilled labor could
be employed to operate the press brake. This could further reduce overhead costs.
The final construction step would be the welding of the tabs to the long walls. These welds
would be accomplished with the use of a spot welder. Each tab should have 10 spot welds along
the tab. The box should then be painted with flat black enamel to prevent any corrosion.
141
Table 46: Production Cost Details for the Battery Box.
Operation 1
Cutting sheet stock
to length per dwg
# BB-1 and
making bends on
press brake per
dwg # BB-2
Operation 2
Spot welding
corner tabs per
dwg# BB-2
Operation 3
Painting the
box with
enamel
Operation 4
Inspection, cleanup,
etc. for the 8 hour shift
1.5 hour per box
0.5 hour per box
0.5 hour per
box
0.5 hour per box
$15/hr
$15/hr
$12/hr
$12/hr
$22.5
$7.5
$6
$6
d. basic overhead factor
1
1
1
1
e. Equipment factor
f. Special operation/tolerance
factor
g. labor/overhead/equipment
cost =
c x (1+d+e+f)
h. purchased
materials/components cost
1
1
.5
.5
.5
0
0
0
$78.75
$22.5
$15
$15
$50
NA
$5
NA
a. total time to complete
operation(s) in hours
b. labor rate for the
operation
c. Labor cost = axb
Total Battery Box Cost = $186.25
8.0 Conclusions
After almost a year of work on the design of a “Goonie” vehicle a great deal has been learned
and much insight has been gain into the procedures and practices of a design engineer. There are
many conclusions that can be drawn from the design and prototyping work that has been
completed and most of the results are discussed in this section. This section will provide the
results from prototype testing as well as any subsequent changes to the final design. The actual
values for the final design will also be compared to the target specifications set in the formation
stages of the project. Finally, conclusions based on the true value of the design, specifications
met, and the impacts of the final design will be presented.
Prototype Testing Results
Prototype Fiberglass Testing
An assortment of test pieces of fiberglass, using various amounts of fabric or mat and nonhazardous Aqua-Resin, were constructed. From these, it was concluded that the enclosure for
the final design was possibly over-designed. Parts made with only a few layers of fabric were
extremely rigid compared to those made with mat. This resulted in very rigid, brittle behavior of
142
the parts made with fabric. The high cost and weight of fabric were also being taken into
account when speculating that the design was excessive. The design included eight layers of
woven fabric as the reinforcement in a polyester resin matrix. A newly-proposed design utilizes
mat rather than fabric to construct the enclosure.
The main factors contributing to the re-design of the enclosure are the following:
• Cost
• Weight
• Rigidity, flexibility, or deflection under static loading
• Impact Resistance
Prototype testing is needed to validate these conclusions, investigate each of the factors
mentioned, and determine a more appropriate design. A prototype scissor door panel and two
additional test panels of different thicknesses were constructed using ¾ ounce chopped strand
fiberglass mat and Aqua-Resin. These prototype panels were made with thickness ranging from
2 to 4 layers of mat.
The woven fabric design would have had more than enough strength, based on the experiences
with the sample fabric and Aqua-Resin, but its cost and weight were high considering its
application. The idea to re-design with mat comes with a tradeoff. Some strength of the
enclosure will be sacrificed by using mat. Chopped strand mat is nearly half the price of fabric.
It also weighs slightly less per square yard. The new design also includes half the amount of
layers of fiberglass further reducing the cost and weight of the enclosure.
Some flexibility of the enclosure panels is desirable so that they do not crack easily or exhibit
brittle behavior. However, too much deflection of an enclosure panel could cause it to protrude
into the passenger or cargo area when acted on by some external load. The test panels made of
2, 3 and 4 layers were each tested under a static load to determine their general stiffness. The
setup for the tests is displayed in Figure 108 below and is similar to that previously used for the
fiberglass gas tank. Results are given in Table 47.
143
Figure 108: Setup for Deflection Testing of Fiberglass Panels
Table 47: Results of Deflection Testing of Fiberglass Panels
Panel (layers)
Load (lb)
Deflection (in)
5
3/8
10
1
2
15
1 1/8
20
1 3/8
10
1/4
3
15
3/8
20
1/2
10
1/8
20
1/4
4
30
3/8
40
1/2
The high probability of the enclosure to be impacted results in a need for the fiberglass panels to
be somewhat impact resistant. To simulate an impact, an apparatus was constructed to hold a
variable amount of weight in a swinging battering ram. This device was also used to simulate an
impact for the door frame. The same principle to estimate the energy transferred to the door
frame was used for the fiberglass testing. The impacting apparatus is shown in Figure 109.
144
Figure 109: Apparatus for Impact Testing of Door Frame, Hinge, and Panel
The test panels were mounted to the door frame for testing. The battering ram was loaded with
the appropriate weights and released from a known height to simulate multiple impacts. Figure
110 shows the setup used for the fiberglass impact tests.
145
Figure 110: Setup for Impact Testing of Door Frame, Hinge, and Panel
From the fiberglass testing, the new design of the enclosure was determined. Upon inspection,
none of the test panels fractured or showed any signs of failure during or after the impact tests.
Given its stiffness, four layers of chopped strand mat will be used in the enclosure design.
Updated Cost and Weight Estimates
The total surface area of the enclosure was obtained from a SolidEdge model as approximately
93.95 ft2 or 10.44 yd2. This value was used to calculate the weight of a layer of mat.
(0.75 oz/ft2) * (9 ft2/yd2)*(10.44 yd2) / (16 oz/lb) = 4.4 lbs/layer
Four layers of mat will be used to construct the enclosure. The total weight of reinforcement was
calculated.
(4.4 lbs/layer) * (4 layers) = 17.6 lbs
Generally, a 50/50 reinforcement-resin (by weight) ratio is used to guarantee the mat is saturated.
So, the resin required will weigh the same as the total weight of the mat (≈ 18 pounds). From
these values, we can make an initial estimate that the total weight of the enclosure will be around
36 to 40 pounds.
Now, the cost of each material required must be calculated. Fabric and mat is generally sold by
the yard for a few different widths depending on the size of parts being made. A 38” wide mat
will be used for the following calculations.
146
Total Area of mat = (10.44 yd2) * (4 layers) = 41.76 yd2
So, about 42 yards of 38” wide, ¾ oz mat is required for one enclosure. For 10 or more rolls of
mat reinforcement, each containing 125 yards, the cost is $2.55 per yard.
(42 yards) * ($2.55 per yard) = $107 per enclosure
For molding and low cost part fabrication, a polyester molding resin will be used. The cost of
#77 Molding Resin is $2.65 per pound for 4 drums (500 pounds each) or more. Nearly 18
pounds of resin is required. This is equivalent to about 2 gallons.
(18 lb) * ($2.65 per pound) = $47.70 per enclosure
A 15 to 20 mil (0.015” or 0.020”) thick gel coat is required for all laminates. It is an unreinforced, clear or pigmented coating resin applied to the surface of a mold or part to provide a
smooth, more impervious finish on the part exterior (Composite Resources, 2007). 1 gallon of
gel coat mix covers 80 ft2 at 20 mils and weighs about 9 pounds. For the enclosure, which has a
total area of about 94 ft2, an acceptable 17 mil gel coat can be applied to the exterior surface with
one gallon. The #173 Super High Gloss Gel Coat Kit is fully UV resistant and compatible with
pigment. It costs $229.95 for a kit of 4 gallons and the necessary hardener.
($229.95 per kit) / (4 gallons per kit) * (1 gallon per enclosure) = $57.49 per enclosure
A pigment can be added to the gel coat to color the enclosure. They are added in at a ratio of ½
pint of pigment per gallon of resin. A ½ pint will be required for the 1 gallon of gel coat
required for the enclosure. 1 gallon of pigment costs $189.95.
(½ pint pigment) * (1 gallon/8 pints) * ($189.95 per gallon) = $11.87 per enclosure
A hardener is required in specific concentrations for each resin to promote the curing of the
resin. MEKP hardener #69 is needed for use with the chosen polyester resin in a 1%
concentration (by weight) and 2% for the gel coat. For 2 gallons of resin and 1 gallon of gel
coat, 5.0 oz of hardener will be used. A case of 4 gallons of hardener costs $129.95 which is
$34.49 per gallon.
(5.0 oz) * (1 gallon/128 fluid oz) * ($32.49 per gallon) = $1.27 per enclosure
Summing the cost of each material per enclosure, the estimated total cost of the materials for the
fiberglass enclosure is $225.33.
Fiberglass Fabric ≈ 18 lbs
Polyester Resin ≈ 18 lbs
Gel Coat ≈ 9 lbs
Hardener & Pigment ≈ 1 to 2 lbs
147
Summing the weight of each material per enclosure, the estimated total weight of the re-designed
fiberglass enclosure is 45 to 50 pounds.
Prototype Heater Testing
The The target specification for the heating system was to attain a 33 ˚F (18.3 ˚C) temperature
differential in less than ten minutes. To test the design, the prototype was enclosed with
insulation material, and the heater was installed. See Figure 111 below. To simulate real
operating conditions, an operator was in the vehicle during the test, and a fan was blowing air
over the vehicle. The test was also conducted on a windy day to help simulate the heat losses
associated with a moving vehicle.
Figure 111: Thermal Testing
The prototype test reached the target specification temperature (18.3 ˚C) in approximately 6.25
minutes. This is about 4.75 minutes before the 10 minute target specification. Comparisons are
given in Figure 112. The maximum temperature differential attained was 22.0 ˚C and was
reached at 11 minutes. The difference between the simulation model and actual data is due to the
fact that the model did not account for heat losses associated with mass transfer and radiation.
148
Figure 112: Thermal Testing Results
The prototype did have less exposed body and window area compared to the final design, but it
also did not have any fiberglass body panels and the windows were half as thick. Calculating the
effects of these discrepancies’, the final design had a lower total heat flux compared to the
prototype. This validates the final design. The conclusion that the thermal performance of the
design will be better than that of the prototype may also be drawn from these results.
Prototype Hinge
Following testing of the scissor door hinge operation, a lack of rigidity was observed. This may
be addressed by creating thicker, more rigid hinge brackets. An alternative solution may be to
use a double bracket arrangement as shown in Figure 113. This arrangement would provide
much more rigidity, while only increasing cost by about $10 per hinge. Further design and
testing is necessary to determine feasibility of this hinge.
149
Figure 113: Hinge Pin and Cotter Pins
Specifications
The project meet the needs statement that was presented at the beginning of this paper, and the
unique features of the vehicle will be very helpful in meeting the business opportunity presented
in the paper. The scissor doors add a very unique feature to the NEV design that is not present in
any other benchmarked vehicle. The scissor door design greatly reduces the parking foot print
needed for this type of NEV. The pull out cargo draw is also an unique addition to the vehicle
because it allows for easy access to the rear cargo area. The slide out battery box will allow for
easy maintenance and the fiberglass structure was proven to work for the vehicle design. Listed
in Table 48 are the target specifications for the proposed vehicle and the actual values that would
be expected for the vehicle.
Table 48: Target Specifications vs. Actual Values for Final Design
Specification
Target Value
Actual Value
Range
30 miles
≈ 28 miles
Gradeability
Can traverse grades up to 15%
Can traverse grades up to 15% at 15
mph
Max Speed
25 mph
25 mph
Acceleration
0 to 20 mph in 8 seconds
Simulation results in 0 to 20 mph in
2 seconds and 25 mph in 5 seconds
Parking
(Footprint)
4 ft x 8 ft
≈ 4.5 ft x 8.5 ft
Visibility
Clear line of sight for driver with
limited obstructions
Large windshield provides clear
view
Weather
Protection
Full waterproof enclosure with seals
Full waterproof enclosure with seals
150
Interior
Temperature
(Summer)
Interior
Temperature
(Winter)
90°F interior at 100°F ambient
Further testing needed
65°F interior at 32°F ambient
Reached within 6.25 minutes
Ventilation
Air flow of 75 ft3/min
Air flow of 104 ft3/min with use of
heater
Energy/Fuel
Charge time less than 10 hours
Charge time of the ten battery
system should be close to 8 hours
Vehicle Weight
< 1200 lbs.
≈ 1200
Cargo
50 - 100 lbs.
Up to 100 lbs.
Ground Clearance
> 5 in.
≈ 11 in.
Safety
Meets latest requirements in
passenger safety
Meets latest requirements in
passenger safety
Based on cost estimation it is assumed with some uncertainty that the overall price of the vehicle
would be close to $6,500 to manufacture. The major costs are shown in Table 49.
Table 49: Overall Cost Estimation
Item/Process
Cost per Vehicle Produced
Enclosure Costs
$
762.00
Scissor Door/Hatch
$
568.00
Seating
$
320.00
LCD
$
630.00
Climate Control
$
324.00
Propulsion System
$
1,828.00
Miscellaneous
$
750.00
Frame
$
1,000.00
Wheels/Shocks
$
400.00
Final Production Cost
$
6,583.00
Based on a mark up of 20% the selling price would be above $7,900. This cost proves a major
problem for the proposed market of college students. It would be much wiser to sell these
151
vehicles to universities and colleges and to retirement communities in colder parts of the country.
The vehicle could be offered as a rental to other potential users.
Some of the environmental impacts of the vehicle are still in question as a majority of the
designing for the final design went to systems other then the propulsion systems for the vehicle.
The electric propulsion system of the vehicle would produce zero harmful emissions when
operating but would shift the energy consumption and pollution to power plants where the
energy is created. These plants still produce harmful emissions and a majority of power plants in
the United States are run off of fossil fuels. When looking at the big picture this is just shifting
the pollution and energy consumption to a different location. One option that was proposed at
the beginning of the year was to produce a charging station for the vehicle using wind, solar or
tidal energy. This would help to greatly reduce the overall energy consumption of the vehicle
and the pollution created to run the vehicle. On paper the vehicle would perform exceptionally
well but there are still many unknowns when it comes to that part of the design. This is a major
problem that needs to be addressed with further designing and prototyping. The “Goonie”
vehicle would be about as recyclable as most modern vehicles with over 75% of disused vehicles
being recycled. There is currently an infrastructure for this process and the system would be able
to recycle and resell most of the disused vehicles.
The political tide is slowly turning in favor of alternative energy vehicles and the “Goonie”
vehicle is well positioned to take advantage of this ground swelling. With ever rising gas prices
and questions of the longevity of fossil fuel supplies the world over, this is the perfect time to
begin to introduce such a unique vehicle. Under the existing tax code, the purchaser of a
qualified electric vehicle is eligible for a tax credit equal to 10% of the purchase price, not to
exceed $4000 (EDTA).
It has been determined that this vehicle offers a unique solution to the current energy problem
that addresses the needs and business opportunity presented in this paper. The proposed vehicle
is a solid solution that needs more design, development, and testing in some areas that were not
fully covered in this paper. It is recommended that more user feedback be gathered from
potential university and retirement community customers. If the cost or parts of the system are
not acceptable to the consumer and can not be changed, it is recommended that the project be
terminated or integrated into other potential designs.
152
Appendix A: Interview Questions
Transportation Director
Interview Question List
1. How important, on a 1 to 10 scale, is using energy efficient vehicles to the transportation
department?
2. Do you think OU could possibly implement energy conservation into more of its present
modes of transportation for students/faculty/staff?
3. Are there any major problems/issues existing with the current transportation mentioned?
4. Is parking or storage space an issue for vehicles in or around campus?
5. Is traffic an issue in or around campus?
6. Do you think a transporter could be used on campus at all by students/faculty/staff?
7. Would you prefer to rent/lease the transporter to customers?
8. What is the maximum speed needed for travel on or around campus by
students/faculty/staff?
9. What safety precautions would be expected for such a transporter?
10. Do you think a large number of these vehicles would improve/worsen parking or traffic?
11. What type of load would you want to be able to carry/tow?
12. Would a trailer hitch be a necessity for maintenance?
13. What type of terrain would the transporter be used on by maintenance?
14. Are there any other capabilities that would be needed for this product to be useful?
15. What features does a small vehicle need for it to be operable throughout the year
(weather protection, performance)?
16. What components of current transportation need no changing or could be used in our
design?
17. What are the most important features that might interest the university in buying such
transporters for students/faculty/staff?
18. GEM vehicles?
153
Customer Questionnaire
Our team is investigating the possibility of an alternatively fueled intra-campus vehicle to
help address the current energy crisis. We need input and suggestions from potential users and
customers. Thank you for your answers and ideas.
1. How many trips per week do you make that are less than 5 miles (walking, driving, etc.)?
2. How much are you willing to pay for transportation (bus fare, vehicle rental, etc.)?
3. How important, on a 1 to 10 scale (10 being MOST IMPORTANT), is having an energy
efficient vehicle to you?
4. What features of a small short distance transport vehicle would be important to you?
5. If possible, would you supplement a vehicle’s power with “human power”, such as
pedaling for these distances?
6. How many passengers would you want to be able to have?
7. What type of load would you want to be able to carry/tow?
8. What road conditions/weather would it be operated in?
9. Do you think you would use the transporter on or around campus at all?
10. Would you want climate controls and/or protection from weather?
154
Heating Feasibility Questions
Q1:
Q2:
Q3:
Q4:
Q5:
Are you willing to pay an extra $300 (my high estimate) to add this feature?
Are you willing to sacrifice on performance (approx. 1/2 mile of total 30 mile range)?
Is adding a heater worth it if an extra small step is required to charge the vehicle?
Do you have any safety concerns related to this design?
Any other input/concerns/recommendations?
155
Appendix B: Business Opportunity
Current product research and customer surveys/interviews have identified that college students
have a need for an all-weather, energy efficient, and alternatively fueled vehicle. This process
recognized that current products fulfilling a similar need are not appealing to college students
due to an improper balance of specific features, such as protection from rain and snow,
aesthetics, and utility (ability to carry cargo and passenger).
Our plan is to develop a vehicle that is appealing to college students by focusing on key elements
and features. The scope of the project includes the body, frame, and comfort/utility features.
Our team selected this scope based on research of similar products and customer input. Research
found numerous vehicles that fulfill the requirements for energy efficiency and are alternatively
fueled but fail to address all of the comfort and utility needs of college students. Therefore, it is
our intention that a power train, and other components necessary for operation, could be easily
integrated to our design or an existing model could be adapted to implement our design. While
similar vehicles addressing the energy situation are available, students are not buying them
because they only address the energy issue and overlook the other essential elements. While one
might suggest focusing on the performance of the vehicle we have concluded that significant
improvements in performance are not feasible within our budget and with available resources. In
addition, the customers desired performance level, maximum speed of 25 MPH, minimum range
of 30 miles, and ability to traverse most hills (15 degrees maximum) is satisfied by many current
products. The fact that these performance levels have been addressed in other products and that
there is little opportunity for a feasible improvement, further supports our decision to focus on
the key elements identified by the customer.
From our surveys it was determined that college students want a level of protection from rain and
snow that is equivalent to a traditional car. While many current alternatively fueled vehicles
have the level of weather protection desired by college students, they are plagued with problems
consisting of: poor ventilation, inadequate protection of cargo, and little to no defrosting
capability. Our team plans to incorporate weather protection into our vehicle that addresses
these problems. Utility of the vehicle is also important to college students. Even though
students want an energy efficient vehicle, they are not willing to sacrifice the ability to carry
cargo or an additional passenger. It is our intention to balance the needs for energy efficiency
and utility by designing the vehicle with the capability to carry a passenger and cargo while
making the vehicle as energy efficient as possible. Aesthetics of the vehicle is a concern that
consistently appeared on the student surveys and is something we plan to address by continually
consulting the customer during the design process. There are also a number of smaller features
that students desired in the vehicle which we plan to include, such as 12 volt outlets, radio, cup
holders, etc.. Since the customer needs to use this vehicle on current roadways and would like to
travel at a maximum speed of 25 MPH we have decided to follow the standards for a NEV
(neighborhood electric vehicle). NEV classification requires additional features such as head/tail
lights, turn signals, wipers, and break lights, all of which are included in our design.
Focusing the design of the alternatively fueled vehicle around aesthetics, weather protection, and
utility will result in an appealing product that satisfies the needs of college students.
156
Appendix C: FMEA and DMFA
Chase’s FMEA
157
Damon’s FMEA
158
159
Kevin’s FMEA
Ohio University ME Department Sr. Design
Failure Mode and Effects Analysis Worksheet (Adapted from Cincinnati Machine PFMEA)
Description of system and mode of operation: Heating and Ventilation
Systems. This includes the heater, ventilation fan, ducts, and nozzles.
Updated 3/10/07
Key Contact / Phone:
Core Team: Goonies, Interior Group, Kevin
Kirch
Date of Initial System Demonstration
Review Board Approval / Date
Location: Stocker center
Potential Failure Modes and Hazard Identification Discussion : Identify all potential failures and safety hazards for this system in
the applicable mode of operation. Complete a FMEA rating form for each significant item. Failure modes of heating and
ventilation system include: Overheating caused by short circuit, fan motor malfunction, thermostat malfunction, build up of dust or
foreign objects that ignite, impact causing deformation of heating unit/vents, fuse fails to function. Other heating failures/modes:
compensated cabin enclosure, clogged vents filters, not enough heat output, Vibration, large effect on range of vehicle, too loud, not
enough heat output. Safety Hazards: Fire, Electrical Shock, smoke inhalation, distraction from road.
FMEA rating form for a single Failure / Hazard
Categorize:
Identify subsystem
and mode of
operation
Heater and
Ventilation
Potential
Failure
Mode and 5
Whys 1
Potential
Effect of
Failure 2
Over heating
Fire, electrical
shock
S
E
V
Probability of
Occurrence of
Failure 3
O
C
C
9
Over a long period
of time it is
possible
4
Current Controls for
Detection /
Prevention 4
Current Controls for
prevention include
the use of fuses to
limit the amount of
current flowing
D
ET
R
P
N
12
Recommended
Action 5
Include a safety
thermostat.
Person
Responsible
&
Completion
Date
Kevin
Action Results
Action Taken
6
SE
V
O
C
C
D
E
T
Heaters being
selected have
a secondary
overheat
thermostat
1. Discuss root cause of the failure mode (based on the 5 whys): The overheating of the system is most likely due to the lack of a safety
thermostat .
2. Discuss/justify the severity rating (SEV): Since fire and electrical shock can cause bodily harm, the consequences of failure are
severe. Failure could also cause permanent damage to vehicle.
3. Discuss/justify the rating for probability of occurrence (OCC): Over a long period of time, it possible that the system could fail. This
probability of failure is reduced if an additional thermostat is added. The probability of occurrence is much higher for certain heating
units, in particular ones without thermostats.
5. Recommended actions: Make specific recommendations for action and include some discussion of the alternatives that were
considered. : The probability of occurrence is greatly reduced if a safety thermostat is used. Some small portable heaters do not have
this feature. It is recommended that the heating system implemented utilize a safety thermostat. Should the operating temperature
exceed its designed limit, the safety thermostat will turn off power to the unit.
6. Notes on Actions taken: The heating unit selected (600 W Back Seat Heat by Therm-Tec) incorporates a safety thermostat in
addition to the primary thermostat.
160
R
P
N
Ryan’s FMEA
161
162
Brandon’s FMEA
163
Jim’s FMEA
164
Brad’s FMEA
165
Camille’s FMEA
166
Michael’s FMEA
167
DFMA
Chase’s DFMA
Scissor Door Hinges
The purpose of the considerations presented in this report is to ensure the lowest possible
production cost of scissor door hinges without sacrificing the quality and reliability of the
mechanism. The two basic considerations are the manufacturing of the individual components
and the assembly of the components into the complete functioning mechanism. The following
guide will be used to consider all costs that may result from design decisions (Adapted from
Design for Manufacturing, Ulrich, Eppinger, 2000).
•
•
•
Components
o Standard
o Custom
ƒ Raw Material
ƒ Processing
ƒ Tooling
Assembly
o Labor
o Equipment
o Tooling
Overhead
o Support
o Indirect Allocation
With respect to the manufacture of the individual components, the first thing considered
in the conceptual phase of design was minimization of the number of parts in the mechanism
without sacrificing functionality. The pin and bracket hinge was chosen accordingly due to the
simplistic 3-piece design, which allows for the same basic function as more complicated hinges.
The next consideration was to minimize the number of custom parts. The specified thicknesses
of the bracket loops and pin diameter are standard sizes, which will minimize purchasing costs,
tooling cost, and required processing.
Several features of the hinge parts, related to manufacturing, have yet to be considered.
Tolerances will be determined following analysis of part connections and fitting. Analysis must
be performed to determine the proper clearances, or if an interference fit may be necessary. The
least precise tolerances that are able to meet the assembly and clearance specifications will be
chosen for the manufacturing drawings. Surface finish will also need to be considered for the
contact surfaces of the bracket loops and the pin. Part treatment options will be further explored;
however, presently none have been identified as beneficial to the part.
Damon’s DFMA
Subsystem
Fiberglass Enclosure
168
Important Considerations
ƒ
ƒ
ƒ
ƒ
Assembly
o Greater number of panels for maintenance/replacement purposes and smaller size
(ease of handling/working with) vs. fewer panels for less assembly.
Specific Features
o Connections to frames (make them easier for less assembly time)
o Joints with other body panels or windows (seals)
Tolerances and Surface Finish
o Fairly tight tolerances needed; maybe use slots instead of holes for connection to
the frame of the vehicle to allow larger tolerances and quicker assembly.
o Glossy surface finish with color similar to an automobile. If fiberglass is made in
a mold, a gel coating can be included for this.
Treatments
o Possible treatment for increased scratch resistance?
Detailed DFM Plan
ƒ Typical fiberglass production processes and their respective capabilities will be further
researched.
o Given process capabilities such as typical tolerances, surface finish, production
rates, size limitations, and our needs the best process will be chosen and
tolerances and specifications for individual body panels will be determined and
incorporated into drawings.
Kevin’s DFMA
System-level DFMA
Many optimization iterations have done to simplify the manufacturing and assembly process.
The approach for the system level DFMA is to simplify the design, remove unnecessary
elements, and assist the assembly and manufacturing process. The team noted that the
ventilation ducts in the first design would be difficult and time consuming to manufacture. They
involved multiple holes and cutouts to be made in the dash board. The system was redesigned,
eliminating the need for the ducts. The current plan to simplify the electrical connections is to
use 12 gauge spade terminals, with the exception of the main power connection to the battery
which is a ring terminal.
Component-Level
For the actual heating unit, the main consideration for simplifying the manufacturing process is
selecting the correct heating unit. From the target specifications, the vehicle design includes
ventilation with a variable speed fan, and a thermostat controlled heater. By selecting a heating
unit that includes variable heat and ventilation, many manufacturing and assembly steps can be
avoided. Essentially, the need for extra dash mounted control knobs has been eliminated in the
design.
Future Plans
169
Create wiring diagrams and complete part drawings for the dashboard including in ventilation.
Complete parts list and bill of materials. Define the allowable tolerances. Also collaborate with
the rest of the team to try to find commonalities in component fasteners, adhesives, wiring, etc.
Ryan’s DFMA
Subsystem
Door Frame
Important Considerations
ƒ
ƒ
ƒ
ƒ
ƒ
Assembly
o Maintain strength of members when welding.
o Construction Time
Design
o Allow for door frame to function without interference from body frame with door
hinge.
Specific Features
o Connection to door hinge.
o Connection with frame of the vehicle.
o Connection of body panels to door frame.
o Connection of window to door frame.
o Seal between door frame, door material and body of the vehicle.
Tolerances and Surface Finish
o The door frame requires tight tolerances in order to seal properly and function
properly.
o Proper surface finish allowing for the attachment of body panels.
Other
o Excess waste of materials.
o Harmful environmental processes.
o Energy conservation.
Brandon’s DFMA
Battery, Electrical Connection, Heating and Ventilation DFMA
I have responsibility for the batteries as well as parts of the heating and ventilation system.
There are many manufacturing and assembly considerations for the batteries, heating, and
ventilation systems. The simpler that all the components are designed the easier they will be to
make and assemble.
•
•
•
•
•
•
DFMA Considerations for Batteries and Electrical Connections
Standard wiring will be used whenever possible.
Wiring with pre-made connections will used whenever possible and cost effective.
Only vital connections will be soldered.
Less important connections will be crimped.
Batteries will be located in a manner that allows them to be easily installed and anchored.
Whenever possible wiring will be zip tied to the frame rather than using rigid wire looms.
170
•
When necessary, wire looms will be riveted rather than welded.
•
•
•
•
•
•
Some DFMA Considerations for Heating and Ventilation
The interior will be designed so that the heater can easily be installed.
The wiring will be installed before the heater is installed.
All the necessary ventilation and ductwork will be installed after the heater is installed.
The heater controls and switches will be installed after the heater in place.
Standard screws or bolts will be used.
All necessary switches will snap into mounting bosses.
Jim’s DFMA
This section is to go over my plan to implement DFMA into one of the subsystem for our team
project. To start, I am working with the body panels and specifically how we will be connecting
the pieces to the frame and also how other pieces will be connected to the fiberglass. This part of
the subsystem will decide many things like what type of connections we use, whether it is
screws, rivets, glues or sealants, etc. Something I have to consider is how we might want to have
multiple types of connections to be used for the project. It would make sense for us to have
some permanent connections to the frame, but possibly have places where panels could be
dismounted quickly for maintenance reasons.
I have to consider whether I want to make all the panels removable in case of an impact to only a
section of the panels. If it were to be a permanent bond, it would be harder to a customer or
repair shop to disassemble and return the product in a fair amount of time. I do know that if I do
go with a certain connection I want to keep the material the same throughout the model. Such as
using screws to set the panels in place, I want to use the same screw for the everywhere I am
using them. Keeping cost is important because the more panels there are the more connections
are needed and the more time and effort it takes to properly install the panels. On the other hand,
having too little number of panels can hinder customers if in a minor impact that requires a
whole side to be replaced. It is a balancing act to go back and forth.
Some other things I need to consider is to think about how the connection can affect the frame or
other parts like the door frame. Using screws creates holes that can cause higher stresses along
the frame tubing and the more holes the worse the case can get. On the other hand I want to keep
safety in mind and I were to use a glue in order to not use hole I need to make sure that there will
not be any chance for a panel to fall off exposing the customer to harm.
I will apply DFMA by looking into all possible styles of connections to the frame and what
proper ones I should implement for the most effective manufacturing to the project. For the
drawings, I will show examples of connections where possible, such as showing a strip for glue
or use Solid Edge to draw up some screws for examples. By doing all these steps I will be able
to properly use DFMA for this class and use it for future knowledge.
Brad’s DFMA
171
Subsystem
Safety Belt
Important Considerations
Assembly
1. Seat belt components must be connected to frame/seating before working space is
restricted from other components.
Design
2. Allow for areas of connection; make sure there is space on the frame and around
the seats to connect end brackets and retractor.
Specific Features
3. Connection of buckle
4. Connection of retractor.
5. Connection of seat belt loop.
Machining
6. Cost of machining the specified shape.
7. Machinability of the chosen material.
Camille’s DFMA
Subsystem
Seating
Important Considerations
ƒ
ƒ
ƒ
Assembly
o Simple yet safe mounting assembly
o Combine parts in the mounting assembly and in the framework that can easily be
combined without sacrificing reliability of assembly
o Reduce number of fasteners in seat assembly to those that are necessary for
manufacturing, safety, and reliability
Design
o Use materials of appropriate strength, size, and endurance
o Design seat to be assembled in a unidirectional manner from the ground up
o Reduce complexity of seat to only justifiable parts
o Reduce adjustability of seat to only justifiable needs of occupants
o Investigate different materials that can be used for the seat structure, seat filling,
and seat covering. Different materials can offer advantages such as lower costs,
higher manufacturability, better safety, and more comfort.
Specific Features
o Connection of mounts to vehicle floor
o Connection of seat base, seat back, and headrest
o Frame/Structure design
o The seat fit in the vehicle with consideration to the door, back partition, and front
dash and wheel.
Michael’s DFMA
172
The pressurized gas struts will be used to assist in opening and closing the rear hatch and the
scissor doors. Although the gas struts will be supplied from a vendor, the end connections for the
struts still need to be determined. Also the required design parameters for the struts need to be
determined. The required design parameters are the following: lift force, total extended length,
total compressed length and the specific type of end connections. For simplicity we will try and
use the same struts for the rear hatch and both of the scissor doors (2 struts for the rear hatch, and
1 strut for each of the scissor doors). The placement of the struts in the vehicle is another big
component of designing the struts (placement of the struts on the vehicle and also on the doors).
173
Appendix D: Calculations
Scissor door hinge calculations
Equivalent Area Equations
Abearing =
π
4
wd
Ashear = 2πr 2
Atearout = 2 wt
Eq. X
Eq. X
Eq. X
Where d is the diameter of the hole and pin, r is the radius of the hole and pin, w is the width of
the bar or twice the width of the bracket material, and t is the distance from the edge of the hole
to the edge of the bracket.
Factor of Safety Equations
FSductile = max(FS1 , FS2 , FS3 )
Eq. X
FS1 = 2 (representative material test data available)
FS2 = 3 (moderately challenging environment)
FS3 = 4 (model is a crude approximation)
Therefore,
FSductile = 4
Material Yield Strength
Syshear = .577Sytention
Eq. X
For AISI 1020 CR Sytention = 44 ksi, therefore:
Syshear = .577(44 ksi) = 25 ksi
Stress Analysis
174
Eq. X
S ys
FS
=
F
Amin
Eq. X
With a factor of safety of 4, a material shear yield strength of 25 ksi, an applied force of 400 lbs,
the minimum area can be calculated.
Amin = (400 lbs)*(4) / (25 ksi) = 0.064 in2
Substituting Amin into the equivalent area equations, all dimensions were calculated. An identical
process was used for horizontal load application.
Matlab Simulation/Model for Heating
%Created By Kevin Kirch
1/27/07
%ME SRD Goonies
%Thermal analysis of Vehicle
clear
%unit conversions 1in=.0254 m
Kin=.03;
%Thermal conductivity of insulation w/mK
%insultation material: insulpink by owens corning, extruded polystryrene
%closed cell foam panel
Lin=.0127;
%Thinckness of insulation m.
Aw=3.4266;
%Area of windows m^2
Kw=.24;
%Thermal Conductivity Windows W/mK
Lw=.00635;
%Thickness of windows m.
Kb= .288;
%Thermal conductivity of body W/mk
Lb= .00635; %Thickness of body panels m.
Ab=7.345;
%Area of body panels m^2
hin=5;
%Convection Coeff. interior
ho=150;
%Convection Coeff. exterior.
Vcab=3.7346;
%Volume of air in Cab m^3.
Cp=1007.;
%Speific heat capacity of Air @ 0 degrees celsius j/kgK
dens=1.237;
%density of air @ 0 degrees centigrade kg/m^3.
Mair=Vcab*dens; %Mass of the air
tstep=.05;
%Time step sec.
loss=0; ttime=0; i=0;
%Inital heat loss,time=0; i=0;
anim = menu('Select system input','Inside and outside temps','Heater power (w):');
if anim==1;
get=input('Specify the Outside temp (deg C) and required Interior temp(deg C): [Tout,Tin]: ');
Tin=get(2);To=get(1); disp(''); %Required temps Celsius.
Ti=To;
Qlossw=((Tin-To)/(1/hin+Lw/Kw+1/ho))*Aw; %heat loss windows at steadystate
Qlossb=((Tin-To)/(1/hin+Lin/Kin+Lb/Kb+1/ho))*Ab; %Heatloss body @steadyst
Qh=(Qlossw+Qlossb); %steady state the net change is 0 so losses=required heat input.
else
To=0;Tin=0;Ti=0;
green=input('Enter the Heater Output (W): '); disp('Note: the final cab temp assumes outside
temp of 0 deg C');
Qh=green(1);
end
delT1=(Qh*tstep)/(Mair*Cp); %Qh*tstep=Mair*Cp*delT1. Change in air temp with no losses.
while Qh-loss>=1
i=i+1;
ttime=(i-1)*tstep;
Totime(i)=ttime;
Tin(i)=delT1+Ti;
%New interior temp with no losses
Qlossw(i)=((Tin(i)-To)/(1/hin+Lw/Kw+1/ho))*Aw; %heat loss windows
Qlossb(i)=((Tin(i) -To)/(1/hin+Lin/Kin+Lb/Kb+1/ho))*Ab; %Heat loss body
175
loss=(Qlossw(i)+Qlossb(i));
%Total Heat loss using interior temp assosiated with no heat
loss.
QlossT(i)=loss;
delT(i)=((Qh-QlossT(i))*tstep)/(Mair*Cp); %Actual temp change assuming losses
Ti=Ti+delT(i);
%Set real total Cabin Temp
Tin(i)=Ti;
end
disp(' '); disp(['Required Heater Output is ',int2str(Qh),' Watts']);
disp(' '); disp('Final Cab Temp, Total time (min)');
disp([Tin(i)
Totime(i)/60]); figure;
plot(Totime/60,Tin);
grid; xlabel('Time (min)'); ylabel('Interior Temp (C)');
title({'Cabin Temp vs. Time For a';[int2str(Qh),' Watt Cab Heater']});
figure; subplot(2,1,1);
plot(Totime/60,QlossT); xlabel('Time (min)'); ylabel('Heat Loss (W)');grid;
title({'Losses vs. Time For a';[int2str(Qh),' Watt Cab Heater']});
subplot(2,1,2);
plot(Totime/60,(Qh-QlossT)); xlabel('Time (min)'); ylabel('Net Heat into the System (W)');
title({'Net heat into the cabin vs. Time For a';[int2str(Qh),' Watt Cab Heater']});grid;
figure; hold on;
plot(Qlossb,Qlossw);
title({'Heat Lost Through Body vs. Heat Lost Through Windows';[int2str(Qh),' Watt Cab Heater']});
xlabel('Heat Lost Through Body (W)'); ylabel('Heat Lost Through Windows (W)');
axis('square');grid;
Figure: Simulation of Experimental Parameters
176
177
178
179
Dynamics Modeling
Motor Selection
The Perm PMG 132 Electric Motor was chosen for its versatility, available torque, and
efficiency. It can operate on a 24-72 volt system. It is a pancake-style motor weighing 24.8 lb
and able to supply 6 horsepower continuously. It retails for around $825. It is shown in Figure
X. The performance specifications for 48 volts are given in Table Y.
Figure X: Perm PMG 132 Electric Motor
Table Y: 48 Volt Performance of Perm PMG 132
86%
Peak efficiency
15.1 hp
Peak power
6 hp
Continuous power
2380 rpm
No-load speed
960 A
Stall current
133 ft-lb
Stall torque
Dynamics Simulation
Dynamics modeling for the campus transporter can be performed given the specifications for the
chosen motor. Table X, given below, displays the constants and parameters used for the
dynamics modeling of the campus transporter. The calculations performed with these
parameters are more accurate, due to the refinement of the transporter design, than the basic
power and energy calculations done previously. The MATLAB code for the simulation is shown
below.
180
Table X: Constants and Parameters for Dynamics Modeling
Parameters
Value and Units
Justification
Wheel Radius (RW)
0.152 m
Size of standard golf carts and NEV wheels
Maximum Velocity
(VMAX)
25 mph = 11.1
m/s
15 mph = 6.67
m/s
Slope Velocity (VSLOPE)
Maximum speed allowed for NEVs
Estimated average speed for travel on a 5% slope
tACCEL
10 seconds
Time to accelerate to VMAX based on target
specification for acceleration
Frontal Area (AF)
1.67 m2
Calculated frontal area of transporter
Coefficient of Drag (Cd)
0.45
Coefficient of Rolling
Friction (CR)
Total Vehicle Weight
(WT)
0.02
1800 lb = 8028 N
Total Vehicle Mass (mT)
818 kg
Gravity (g)
9.81 m/s2
Density of Air (ρAIR)
1.18 kg/m3
Motor Efficiency (η)
86%
Torque Constant (KT)
27 oz·in/A
Estimate based off automobiles with similar shape and
frontal area
Conservative estimate of friction between rubber and
concrete
Estimate based on benchmarked vehicles and weight
of two 95th percentile males with cargo
Estimate based on benchmarked vehicles and weight
of two 95th percentile males with cargo
Calculated by Sir Isaac Newton in Philosophiae
Naturalis Principia Mathematica
Density of air at sea level
Peak Efficiency of Perm PMG 132 Electric Motor at
48 Volts http://www.thunderstruckTorque Constant of Perm PMG 132 Electric Motor
http://www.thunderstruck-ev.com/perm132.htm
%---------------------------------------------------------------------function ydot = dtransporter(t,y)
% dtransporter.m - Campus Transporter Differential Equations of Motion
% Dynamics Modeling
% Team 1 - The Goonies
% ME 470/1/2 - Senior Design
% Last Modified by Damon Givens on 2/13/07
% from Dr.Iz (Urieli) 02/14/04 (modified 2/16/04 to include ke)
%---------------------------------------------------------------------% y(DIS) = distance covered (m)
% y(VEL) = velocity (m/s)
DIS = 1;
VEL = 2;
% Constants
g = 9.807; % Gravity [m/s^2]
Air = 1.18; % Density of Air [kg/m^3]
% Transporter Parameters
rw = (.5)/3.28; % Wheel Radius [(feet)/3.28 feet/m]
Vmax = (25)*4/9; % Maximum Velocity [(mph)*9 mph/4 m/s]
181
Af = (16)/3.28^2; % Frontal Area [(feet^2)/3.28^2 feet^2/m^2]
Cd = 0.45; % Coefficient of Drag
Cr = 0.02; % Coefficient of Rolling Resistance
Wt = (1800)*4.46; % Total Weight [(pounds)*4.46 N/lb]
mt = Wt/g; % Total Mass [kg]
Friction = 0.7; % Coefficient of Friction for Braking
tAcc = 10; % Time to Accelerate to a Specified Velocity [seconds]
VAcc = (25)*4/9; % Velocity after Acceleration [(mph)*9 mph/4 m/s]
Vs = (15)*4/9; % Velocity for Travel on a Slope [(mph)*9 mph/4 m/s]
slope = 0; % Slope
% Battery Voltage:
vbat = 48; % [Volts]
% Motor Specs:
winding = 0.0255; % Terminal Resistance [ohms]
kt = 0.191; % Torque Constant [Nm/A]
noload
=
2380*2*pi/60;
%
No-Load
Angular
Velocity
[(RPM)*2pi/(60
second/min)]
ke = vbat/noload; % Back Emf Constant [volts/(rads/s)] (from no-load rpm)
% Wheel/Motor Transmission Ratio:
n = 3.3; % Wheel Torque / Motor Torque
% Applied Torque at Rear Wheel:
tw = (n*kt/winding)*(vbat - ke*n*y(VEL)/rw);
% Current Drain (how can we display this?)
im = tw/(n*kt);
% Resistive Forces: Drag, Slope, Rolling Resistance
Fd = .5*Cd*Air*y(VEL).^2;
Fr = Wt*(Cr + slope);
ydot(DIS) = y(VEL); % Velocity
ydot(VEL) = (tw/rw - (Fd + Fr))/mt; % Acceleration
ydot = [ydot(DIS); ydot(VEL)]; % Must Be Column Vector
%---------------------------------------------------------------------% transporter.m - Campus Transporter Simulation
% Dynamics Modeling
% Team 1 - The Goonies
% ME 470/1/2 - Senior Design
% Last Modified by Damon Givens on 2/13/07
% from Dr.Iz (Urieli) 02/14/04
%---------------------------------------------------------------------clear; clc;
tspan = [0,10]; % Time Span to Integrate Over
y0 = [0;0]; % Initial [Position;Velocity] (Starting from Rest)
[t,y] = ode45('dtransporter',tspan,y0);
size(t) % Number of steps being evaluated
velo = y(:,2).*9/4; % Velocity [mph] (9mph = 4m/s)
plot(t,velo,'b'); grid on; axis([0 10 0 30]); set(gca,'FontSize',14);
xlabel('Elapsed Time(sec)'); ylabel('Velocity(mph)');
title('Dynamic Simulation of Campus Transporter')
182
Figure X: Results of Dynamic Simulation
The simulation results display that the transporter would reach a velocity of about 25 mph in less
than 6 seconds. This simulated performance meets the target specification for the acceleration of
the transporter.
Basic Power and Energy Calculations
Below is the MATLAB code used to perform basic power and energy calculations for the
vehicle. The constants and parameters for these calculations are the same as those used for the
dynamics modeling. This script program was created to determine the amount of energy
required for the transporter’s full range of 30 miles. An average trip, like that used in
preliminary energy calculations consisting of accelerations and decelerations, travel on a slope,
and maximum velocity travel, was used to make a better estimate of the required energy.
%---------------------------------------------------------------------% Basic Power and Energy Calculations
% Team 1 - The Goonies
% ME 470/1/2 - Senior Design
% Originally created by Damon Givens on 1/29/07
% Last Modified on 2/13/07
%---------------------------------------------------------------------clc; clear; % clears cursor and variables
183
% Variables and Constants
Dw = (1)/3.28; % Wheel Diameter [(feet)/3.28 feet/m]
Vmax = (25)*4/9; % Maximum Velocity [(mph)*9 mph/4 m/s]
Af = (16)/3.28^2; % Frontal Area [(feet^2)/3.28^2 feet^2/m^2]
Cd = 0.45; % Coefficient of Drag
Cr = 0.02; % Coefficient of Rolling Resistance
Wt = (1800)*4.46; % Total Weight [(pounds)*4.46 N/lb]
g = 9.807; % Gravity [m/s^2]
Air = 1.18; % Density of Air [kg/m^3]
Friction = 0.7; % Coefficient of Friction for Braking
tAcc = 10; % Time to Accelerate to Vmax [seconds]
Vs = (15)*4/9; % Velocity for Travel on a Slope [(mph)*9 mph/4 m/s]
slope = 5; % Percent Slope
Eff = .86; % Motor Efficiency
% Drag Force [N]
FdVmax = .5*Air*Vmax^2*Af*Cd;
FdVs = .5*Air*Vs^2*Af*Cd;
% Rolling Resistance Force [N]
Fr = Cr*Wt;
% Force due to a Slope [N]
Fs = Wt*(slope/100);
% Gross Power at Vmax on Level Slope[W]
PgVmax = (FdVmax+Fr)*Vmax;
% Gross Power to Accelerate to Vmax [W]
PgAcc = (.5*(Wt/g)*Vmax^2)/tAcc;
% Gross Power for Travel on a Slope [W]
Pgs = (FdVs+Fr+Fs)*Vs;
% Average
ta = 144;
ts = 345;
tv = 626;
Trip
% Time Spent Accelerating [sec]
% Time Spent on a Slope [sec]
% Time Spent at Vmax [sec]
% Energy = Power*Time
Ea = PgAcc*ta; % Energy Used Accelerating [J]
Es = Pgs*ts; % Energy Used Traveling Up a Slope [J]
Ev = PgVmax*tv; % Energy Used Traveling at Vmax [J]
Etotal = Ea+Es+Ev; % Total Energy Used on Average Trip [J]
Erange = Etotal*3.6364 % Total Energy Used for Range of 30 Miles [J]
% Energy Supplied
Vbat = 48;
Ebat = 41;
Esupp = 2*41*48*3600;
Eactual = Eff*Esupp
if (Eactual<Erange)
'NOT enough energy for the transporter to travel the full range of 30
miles'
else
'There is enough energy for the transporter to travel the full range of
30 miles'
end
184
Figure X: Results of Basic Power and Energy Calculations
(ERANGE - EACTUAL) / (ERANGE) * 100 = 5.97%
The lack of supplied energy would only cause an estimated 6% reduction in the target range for
the vehicle. This amounts to about 1.8 miles of travel. These calculations are mainly for
feasibility purposes. The operating temperature and conditions as well as the actual payload and
form of travel (acceleration, top speed, flat ground, etc.) may have large impacts on the actual
range of the vehicle.
185
Appendix E: References
Rodrigue, J-P et al. (2006) The Geography of Transport Systems, Hofstra University,
Department of Economics & Geography, http://people.hofstra.edu/geotrans.
U.S. Department of Transportation(1998), Low Speed Vehicle Ruling [WWW Document] URL
http://www.nhtsa.dot.gov/cars/rules/rulings/lsv/lsv.html (visited 2006, September 28)
Ohio Bureau of Motor Vehicles, Ohio Traffic Rules [WWW Document] URL
http://www.bmv.ohio.gov/misc/traffic_rules.htm (visited 2006, September 28)
Ohio Bureau of Motor Vehicles, Motor Scooter Information [WWW Document] URL
http://www.bmv.ohio.gov/driver_license/motor_scooter_info.htm (visited 2006, September 28)
Ohio Revised Code, 4519.01. Special Vehicle Definitions [WWW Document] URL
http://onlinedocs.andersonpublishing.com/oh/lpExt.dll/PORC/1cc60/1dc3b/1dc3d?f=templates&
fn=document-frame.htm&2.0#JD_451901 (visited 2006, September 28)
Carney Jr., R. U.S. Patent 6,260,649 Energy conserving electric vehicle Filed: 1999, March 10.
Chaney, G. U.S. Patent 6,631,775 Electric vehicle chassis with removable battery module and a
method for battery module replacement Filed: 2000, July 6.
Wakitani , T. et al. U.S. Patent 7,116,065 Electric vehicle Filed: 2004, October 14.
Kocher , M. et al. U.S. Patent 7,117,044 Alternative energy system control method and
apparatus Filed: 2003, December 30.
United States Department of Energy, 2006 Strategic Plan.
http://www.energy.gov/media/2006StrategicPlanSection5.pdf (visited 10/4/2006)
186
U.S. Department of Energy, Transportation Energy Data Book: Edition 24-2004.
http://www.eia.doe.gov/kids/energyfacts/uses/transportation.html Last Revised: July 2006
(visited 10/3/2006)
U.S. Department of Energy, Field Operations program, Electric and Hybrid Vehicle Testing,
http://avt.inel.gov/pdf/prog_info/futurecarslides2002.pdf (visited 10/15/2006)
Ohio Department of Transportation, Roadway Engineering Standards,
http://www.dot.state.oh.us/roadwayengineering/standards/Publications/LDM/2006-0421/200_apr06.pdf Last Revised: January 2006 (visited 10/15/2006)
CSG Network, Stopping Distance Calculator
http://www.csgnetwork.com/stopdistcalc.html Last Revised: 2006 (visited 10/15/2006)
Hints and Things, Approximate Stopping Distances
http://www.hintsandthings.co.uk/garage/stopmph.htm (visited 10/15/2006)
Weather.com, Local Monthly Averages(Used for various cities)
http://weather.msn.com/local.aspx?wealocations=wc:USAZ0166 (visited 10/15/2006)
Athens Cycle Path, Local places to ride, http://www.athenscyclepath.com (visited 10/15/2006)
Wood, John H., Long, Gary R., Morehouse, David F.; “Long-Term World Oil Supply
Scenarios”; Energy Information Agency, Department of Energy.
http://www.eia.doe.gov/pub/oil_gas/petroleum/feature_articles/2004/worldoilsupply/oilsupply04.
html (Visited 10/26/2006)
Figure 1. http://www.gemcar.com (Visited 10/5/06)
Figure 2.http://www.twike.com/ (Visited 10/5/06)
Figure 3. http://www.aerorider.com/nl/aerorider.html (Visited 10/5/06)
Conversions. http://www.petrik.com/PUBLIC/library/conv/conversionsFH.htm (Visited
10,24/06, 11/1/06 ,11/4/06
Optima Batteries Tech Specifications [WWW Document] URL
http://www.optimabatteries.com/publish/optima/americas0/en/config/product_info/automotive/d
eep_cycle.html (visited 2006,November 3)
Deka Dominator Product Specs [WWW Document] URL
http://www.eastpenn-deka.com/default.aspx?pageid=454(visited 2006,November 3)
AutoCraft Deep Cycle Marine Battery Product Page [WWW Document] URL
http://www.partsamerica.com/ProductDetail.aspx?categorycode=3583&mfrcode=ATC&mfrpart
number=27DC2 (visited 2006,November 3)
187
Advances Vehicle Testing: ParCar.http://avt.inel.gov/pdf/nev/parcar2pass.pdf (Visited
November 18,2006)
Advances Vehicle Testing: GEM.http://avt.inel.gov/pdf/nev/Gem2pass.pdf (Visited November
18,2006)
Carquest Batteries [WWW Document] URLhttp://www.carquest.com/partsBatteryTypes.html#1
(visited 2006,December 18)
Determine The Root Cause: 5 Whys.
http://software.isixsigma.com/library/content/c020610a.asp (visited 1/31/07)
The Cause and Effect Diagram (a.k.a. Fishbone).
http://www.isixsigma.com/library/content/t000827.asp (visited 1/31/07)
Fishbone Template [Excel Document]
http://www.isixsigma.com/library/content/t000827.asp (visited 1/31/07)
Functional Analysis System Technique – The Basics.
http://www.value-eng.org/pdf_docs/monographs/FAbasics.pdf (visited 1/31/07)
Value Analysis and Functional Analysis System Technique.
http://www.npd-solutions.com/va.html (visited 1/31/07)
Zero Emission No Noise – ZENN Specifications.
http://www.zenncars.com/specifications/specs_index.html (visited 12/21/06)
Neighborhood Electric Vehicle Company – Gizmo Specifications.
http://www.nevco-ev.com/gizmo-specs.html (visited 12/21/06)
Global Electric Motorcars – GEM Vehicle Models – Standard Features.
http://www.gemcar.com/models/default.asp?ID=358 (visited 12/21/06)
Dynasty Electric 2006 IT Sedan,
http://www.itiselectric.com/section.asp?catid=53&pageid=220 (visited 12/21/06)
American Custom Golf Cars, Inc. – California Roadster.
http://www.californiaroadster.com/roadster_features.html (visited 2/19/07)
American Custom Golf Cars, Inc. – Hummer H3.
http://www.californiaroadster.com/hummer_features.html (visited 2/19/07)
“The Barton” LSV by B.I.G. MAN Specifications.
http://www.bigmanev.com/2003/specs.html (visited 2/19/07)
188
Twike – An Overview.
http://www.twike.us/TWIKE_an%20_overview_usa.pdf (visited 2/19/07)
Aerorider – Ultralight Vehicle – Electric Hybrid Tricycle – Specifications.
http://www.aerorider.com/en/aerorider.html (visited 2/19/07)
Physical Properties of Composite Materials.
http://www.composite-resources.com/technology-and-resources/technology/default.html (visited
1/3/07)
The Fundamentals of Fiberglass – Fibre Glast Developments.
http://www.fibreglast.com/content.php?URLID=41&trksrc=FreeInfo (visited 2/6/07)
Why fiberglass is better for your parts and components.
http://www.fiberglasssales.com/index.php/why_use_fiberglass (visited 2/6/07)
Overview – Acrylonitrile Butdiene Styrene (ABS), Impact Grade, Molded.
http://www.matweb.com/search/SpecificMaterial.asp?bassnum=O1103 (visited 2/6/07)
Parma Plast as – Material Descriptions – ABS
http://www.parmaplast.no/gml/uk/deafult.htm (visited 1/31/07)
Source of Reinforced plastic source:
http://www.patentstorm.us/patents/4875710-description.html (visited 1/30/07)
Example of installing fiberglass to golf cart:
http://www.diynetwork.com/diy/ab_small_engines/article/0,2021,DIY_13693_3184049,00.html
(visited 2/8/07)
Source of images for Screws and Bolts
http://www.nevatiasteel.com/images/pic_cold.jpg (visited 3/8/07)
http://img.alibaba.com/photo/50535699/Rivets_And_Self_Tapping_Screws.jpg (visited 3/8/07)
Wikipedia, Acrylic Glass
http://en.wikipedia.org/wiki/Polymethyl_methacrylate (visited 3/13/07)
Wikipedia, Polycarbonate
http://en.wikipedia.org/wiki/Polycarbonate (visited 3/13/07)
Acrylics & Polycarbonates, J. Freeman, Inc. distributor - Plastics
http://www.jfreeman.com/acrylic_polycarbonate.html (visited 3/13/07)
Acrylite® Acrylic Abrasion Resistant Sheeting, United States Plastic Corporation
http://www.usplastic.com/catalog (visited 3/13/07)
EDTA - About Neighborhood Electric Vehicles http://www.electricdrive.org/ (visited 5/28/07)
189