Conceptual Car Project

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Concept Automobile Body

Geometric Design

Group AS01

April 6th

, 2009

Miaad Safari | 0365539

Simarjit Chouhan | 0363622

Mohamed El Defrawy | 0241065

Peyman Lashgari | 0459608

Saravanan Uthayalingham | 0357266

MECHANICAL

ENGINEERING

4M06FINAL REPORT DR. SPENCE


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Table of Contents

1 Abstract ................................................................................................................................................. 1

2 Summary of Interim Presentation ........................................................................................................ 2

3 Interviews with Sports Car Dealers ....................................................................................................... 3

4 Meeting at GM ...................................................................................................................................... 5

5 Concept Car Design Attributes .............................................................................................................. 7

6 Geometric Model Design Attributes ..................................................................................................... 9

7 Target Market ..................................................................................................................................... 11

8 Competitors ........................................................................................................................................ 12

9 Benchmarking ..................................................................................................................................... 12

9.1 Battery Placement: ..................................................................................................................... 12

9.2 Electric Motor: ............................................................................................................................ 14

9.3 Dimensions: ................................................................................................................................. 14

9.4 Specifications: ............................................................................................................................. 16

10 Work Flow Section .......................................................................................................................... 17

10.1 Initial Extrusion ........................................................................................................................... 17

10.2 Necessary Cuts ............................................................................................................................ 19

10.2.1 Top Cut ................................................................................................................................ 19

10.2.2 Front Cut ............................................................................................................................. 20

10.2.3 Revolved Cuts ...................................................................................................................... 21

10.3 Surfacing: Chamfers Edges & Surface Fillets ............................................................................... 22

11 Inventor to Alias to Catalyst ............................................................................................................ 24

11.1 Inventor’s Failure to Shell and Why ............................................................................................ 24

11.2 Alias to the Rescue ...................................................................................................................... 24

12 Surface Continuity ........................................................................................................................... 25

13 Car Features .................................................................................................................................... 26


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13.1 Side/Back Cameras – A Safer Drive ............................................................................................. 26

13.2 Bigger Windows, Bigger View ..................................................................................................... 26

14 Evolution of Interior Tub ................................................................................................................. 27

14.1 Stage 1 ......................................................................................................................................... 27

14.2 Stage 2 ......................................................................................................................................... 27

14.3 Stage 3 ......................................................................................................................................... 28

14.4 Stage 4 ......................................................................................................................................... 28

14.5 Comparison between initial sketch concept and finished interior cabin ................................... 29

15 Evolution of Steering Wheel ........................................................................................................... 29

15.1 Revision 1 .................................................................................................................................... 29

15.2 Revision 2 .................................................................................................................................... 30

15.3 Revision 3 .................................................................................................................................... 30

16 iMike Sizing ..................................................................................................................................... 31

17 Lessons learnt ................................................................................................................................. 35

Appendix A – Dealer Survey Questions ...................................................................................................... 36

Appendix B – Dealer Survey Results ........................................................................................................... 37

Appendix C – Sample Work-In-Progress Exterior CAD Drawings ................................................................ 39

Appendix D – Final CAD Images .................................................................................................................. 41


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List of Figures

Figure 1: Suspension Technologies............................................................................................................... 2

Figure 2: Chassis Technologies...................................................................................................................... 2

Figure 3: Cadillac CTS Coupe Concept........................................................................................................... 4

Figure 4: Canadian Household Income ....................................................................................................... 11

Figure 5 : Tesla Roadster`s Battery Placement ........................................................................................... 13

Figure 6 : Cadillac Converj`s Battery Placement ......................................................................................... 13

Figure 7 : Tesla Roadster`s Electric Motor Placement ................................................................................ 14

Figure 8 : Concept Version 1.0.................................................................................................................... 17

Figure 9: Top Half (Greenhouse) Profile Extrusion ..................................................................................... 18

Figure 10: Bottom Half Profile Extrusion .................................................................................................... 18

Figure 11 : Concept Version 2.0.................................................................................................................. 18

Figure 12: Top Half (Greenhouse) Top Cut ................................................................................................. 19

Figure 13: Bottom Half Top Cut .................................................................................................................. 20

Figure 14: Top Half (Greenhouse) Front Cut............................................................................................... 20

Figure 15: Rear End Cut-Revolve................................................................................................................. 21

Figure 16: Front End Cut-Revolve ............................................................................................................... 21

Figure 17: Location of Surface Fillets .......................................................................................................... 22

Figure 18: Final Model done on Inventor ................................................................................................... 23

Figure 19: Offset error ................................................................................................................................ 24

Figure 20 : Initial interior concept sketch ................................................................................................... 27

Figure 21 : Interior Cabin ............................................................................................................................ 27

Figure 22 : Finished Interior Cabin with center console detail ................................................................... 28

Figure 23 : Finished Interior Cabin with Colour .......................................................................................... 28


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Figure 24 : Comparison between initial sketch and final interior cabin..................................................... 29

Figure 25 : Steering Wheel Revision 1 ........................................................................................................ 29



Figure 28 : iMike.......................................................................................................................................... 31

Figure 29 : Driver’s view from iMike position............................................................................................. 32

Figure 30 : Driver's view from iMike position 2 .......................................................................................... 32

Figure 31 : Concept car seating configuration............................................................................................ 33

Figure 32 : Concept car available leg room................................................................................................. 34

List of Tables

Table 1 : 9-Box Concept Car Design Attributes............................................................................................. 7

Table 2 : 9 Model Car Design Attributes ....................................................................................................... 9

Table 3 : Tesla Roadster Dimensions .......................................................................................................... 14

Table 4 : Tesla Roadster Wheel & Tires Dimensions................................................................................... 15

Table 5 : Tesla Roadster Specifications....................................................................................................... 16


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1 Abstract

Our selected project involves the complete design and production of a scaled model concept car to be

released for production in 2012. This undertaking involves less obvious engineering aspects such as

creative design, in contrast with complex mathematical models that are ordinarily associated with

engineering projects. Our group’s goal is to develop a concept two passenger vehicle, which will includea CAD model design, a plastic prototyped exterior, and a painted interior cabin.

When designing the conceptual automobile design, the team decided to follow an Educated Creativity

model. The model is based on educated design principles where customer needs/wants are identified

and ensured to be feasible for implementation. In order to employ this model, the team decided to

divide the knowledge base as efficiently as possible, by creating experts in different automobile

segments. These segments included propulsion technologies; vehicle dimensions, engine and drive

layouts, body styles; chasses, steering and suspension; interior technologies and finally interior seating.

To aid in the design of the concept, external research on customer buying habits was required. This was

achieved by asking the Sales departments of various dealerships questions pertaining to theneeds/wants of the sports car segment. Dr. Fleisig also believed that it would be extremely beneficial to

sit down with a design expert in the automotive industry and learn how they develop their customer

needs and vehicle concept ideas. We were set up with a contact at GM, Rick Rajaie, who was kind

enough to devote an entire day to teaching us some of the basics in vehicle design and market profiling.

Mr. Rajaie showed us how to utilize a 9-box winning strategy tool which is extensively implemented by

design experts at GM.

The next step in our design process was to develop a list of competitors that target the same customer

base as our vehicle, thus giving us the chance to benchmark one of these competitors. The car that was

benchmarked was the Tesla Roadster. This was done due to the similarities in size and powertrainbetween the Roadster and our concept.

After conducting all the research required developing the concept, work was begun on the model. The

concept car was designed on Autodesk Inventor software. The work flow used to design the car was

outlined such as the initial extrusions, cuts and fillets used to obtain the shape required. Certain issues

arose while trying to shell the design in Inventor. This issue was corrected by importing the design in

Alias Studio and shelling the design there. While designing the interior cabin, iMike was used to ensure

that the interior dimensions were adequate to the driver and passenger. When designing around a

1/12th scale iMike, we were able to ensure that there was adequate head and leg room in our model.

Several features were incorporated into our design such as side-view cameras as well as large windows

to increase the driver visibility. The 3D CAD model was then rapidly prototyped using ABS plastic. The

result was a 1/12th scale model of the concept’s exterior and interior. There were errors associated with

the exterior prototyping. These errors were a result of surface discontinuities which was also evident in

the STL file.


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2 Summary of Interim Presentation

When designing the conceptual automobile design, the team decided to follow an Educated Creativity

model. This model aspires to produce a creative and aesthetically pleasing design. The model is based

on educated design principles where customer needs/wants are identified and ensured to be feasible

for implementation. In order to employ this model, the team decided to divide the knowledge base as

efficiently as possible, by creating experts in different automobile segments. These segments included

propulsion technologies; vehicle dimensions, engine and drive layouts, body styles; chasses, steering and

suspension; interior technologies and finally interior seating. Different propulsion technologies such as

gasoline and hydrogen combustion, gasoline-electric hybrids and electric propulsion were analyzed. An

electric propulsion technology was selected based on global trends (price of oil, demand for greener

technologies), its efficiency, performance and finally the available fuelling infrastructure. A variety of

engine and drive layouts were further studied such as front, mid and rear engine layouts as well as rear

and all wheel drive. The chassis dimensions were further studied but are now identified as irrelevant due

to the modified chassis that shall be incorporated into our design. The figures below outline the

different chassis and suspension technologies researched.

Figure 1: Suspension TechnologiesFigure 2: Chassis Technologies


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the future. This weighed heavily in our decision to adopt an all electric powertrain over a variety of

hybrid powertrains and both conventional & hydrogen combustion engines.

We had initially considered incorporating a pedal-free joystick steering system in our vehicle. However,

all the sales personnel at the different car dealerships felt that this technology would not be very

appealing. Firstly, this type of steering system would significantly depart from conventional steering

systems and would require individuals to re-learn the basics of driving and steering. Furthermore, sports

cars customers want to feel connected to the road via a physical linkage and this technology would

dilute the experience and feel noticeably artificial.

With respect to vehicle aesthetics, we found that the ideal choice of colour for the exterior of the car

would be gray, despite the popularity of black, red and white. Grey is a really good colour for showing

the lines of the car, and is commonly used by automobile manufacturers such as BMW in their concept

vehicles. Especially since our project is titled “Concept Automobile Geometric Design”. Furthermore, to

provide the clean, sleek look to the exterior that customers love, we decided to forgo the conventional

door handle in favour of a slot behind the trailing edge of the door as on the vehicle in Figure 3 below.

Figure 3: Cadillac CTS Coupe Concept

Lastly, with respect to cargo capacity, both the BMW and Nissan dealerships stated that the sports car

should have at least enough space in the trunk for 2 sets of golf clubs, whereas the Honda dealership


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said a true sports car might only have enough room for an overnight bag. We ended up settling to a

compromise of a single set of golf clubs due to the reasons stated previously and also because the car

we decided to benchmark (the Tesla Roadster) has a cargo capacity of a single set of golf clubs.

4 Meeting at GM

One key comment that we received as feedback on our interim presentation was that we required a

better knowledge of our customer base and what they want in a vehicle. Dr. Fleisig believed that it

would be extremely beneficial to sit down with a design expert in the automotive industry and learn

how they develop their customer needs and vehicle concept ideas. We were set up with a contact at

GM, Rick Rajaie, who was kind enough to devote an entire day to teaching us some of the basics in

vehicle design and market profiling.

We first started the meeting by focusing on the customer. Rick stressed the importance of knowing

your customer base and matching their needs. He cemented this idea by giving a real life example

relating to international automaker TATA. He explained to us that TATA’s manufacturing ability was one

of the worst he had seen and that they had been dismissed by GM as an investment possibility.

However, TATA has grown to be a 54 billion dollar company, much larger than GM currently at 2 billion.

How did they achieve this? They understood their customer base and developed extremely cheap

vehicles with no bells or whistles that anyone could afford. With this concept, they were able to

overcome the shortcomings of manufacturing and thus the company grew at an incredible rate.

After reviewing our customer base, we turned our focus to the 2 door sports vehicle we will be creating.

Rick showed us how to utilize a 9-box winning strategy tool which is extensively implemented by design

experts at GM. The 9-box winning strategy allows the designers to choose the key attributes of the

vehicle at the beginning of the design process and then refer back to the key attributes at various stages

when making key design decisions. Thus, the designers are forced to develop a rough structure of


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vehicle characteristics that are set in stone. This is done as any major changes midway through a design

process will significantly affect project costs and durations.

The next step in our design process was to develop a list of competitors that target the same customer

base as our vehicle, thus giving us the chance to benchmark one of these competitors. We decided to

choose a vehicle that is similar to our concept in size and power train. Rick showed us that when looking

at the dimensions (wheelbase for example) of several cars in the same market, they all have similar

measurements plus or minus a couple of inches.

After developing a better understanding of our vehicle, our competitors, and our customer base, our

group took turns filling Rick in on the research we did in each of our respective researched sections. We

also included suggestions that we had developed to be included in our design. Rick gave us some real

life road blocks that could get in the way of our ideas. One example was ergonomics of not only the

design, but also for the installer of the device at the assembly plant. Another good example was to look

at the costs vs. benefits of using a certain technology; although a technology can increase demand, will

it offset the costs associated with the new technology? One more example was that some of the

technologies could be patented by other companies and you would need to purchase the patent first.

Although these are all valid issues and we are conscious of them, we will try to avoid them when

creating our concept car.

A last topic of discussion in our meeting was to draw on Rick Rajaie’s extensive project experience to

help us develop a project plan and complete this project successfully. Rick showed us some of the

technique’s that are usually used which include frequent project reviews at important project

milestones. Using this method, we will be looking to set our milestones for this project and arrange

review meetings with Dr. Spence at each of our milestones.


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To conclude, our meeting with Rick was very useful and gave us an industry perspective on how vehicle

designs are created. Rick energized us to not only create this vehicle, but also make sure it is something

that would actually be of value to customers.

5 Concept Car Design Attributes

The 9-Box Concept Car Design Attributes

PowerfulLuggage capacity:

Set of golf clubsTrack -worthy

Big wheels with fender flares Big moon roof $80,000 - $100,000

Fold away steering wheel Mid engine layout2 door

2 passenger

Table 1 : 9-Box Concept Car Design Attributes

After our meeting with our General Motors contact Rick Rajaie, we developed a 9 box concept design

attribute strategy. Table 1 indicates all the attributes we are trying to incorporate in the concept car. An

explanation for each of the design attributes follows:

Powerful: Power judged by the performance of the engine shall be the most important factor. This is

highlighted by the dealership research conducted by our team, which indicates above all other factors;

the car shall have significant acceleration and power. The car should be able to achieve high torque at

low RPM`s increasing the acceleration capabilities of the concept.

Luggage capacity: As noted by research, customers do not place great emphasis on the luggage capacity

of a sports car. At the minimum, the average customer would like to at least be able to fit in a set of golf

clubs in the trunk.


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Track-worthy: Capable of performing at a high level with respect to power and handling at a race track.

Big wheels with fender flares: The concept car shall include big wheels with low profile tires to increase

the handling performance of the car. The fender flares will also be added to increase the visual appeal of

the concept design.

Big moon roof : A big moon roof shall be a part of the concept design. This shall help in conveying an

open feeling to the concept, as in a convertible.

$80,000 - $100,000: The concept car will be priced within $80,000 - $100,000. This shall help in depicting

a high end performance oriented sports car.

Fold away Steering wheel: The design concept shall include a fold away steering wheel. This shall help

when the client ingresses or egresses from the car as well as creating a roomier interior.

Mid engine layout: A mid engine layout shall be incorporated as used by the benchmarked Tesla

Roadster which is further highlighted in the benchmarking section.

2 door; 2 passengers: The concept car shall have 2 doors and be able to accommodate only 2

passengers.


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6 Geometric Model Design Attributes

The 9-Box Geometric Model Design Attributes

2 Door

2 Passenger

Mid-Engine LayoutLarge Windows for Increased

Visibility & Safety

Big WheelsAcceptable leg & head room

(iMike)

Technologically Advanced

Interior

Sports Seats with Bolsters Racing Steering Wheel

Luggage capacity:

Set of golf clubs

(CAD MODEL ONLY)

Table 2 : 9 Model Car Design Attributes

The above 9 box table differs from the previous one by outlining only those attributes that can actually

be incorporated into the geometric design. The following includes a detailed explanation of the new

attributes and they will be implemented:

2 door; 2 passengers: Please refer to the Concept Car Design Attributes for the reasoning behind

incorporating this feature.

Mid engine layout: A mid engine type layout shall be used for the model. This will have to account for

the propulsion technology used i.e. electric motor. The chassis will have to be modified in order to

account for the larger than usual batteries used in electric cars as explained below for the Tesla

Roadster.

Large Windows for Increased Visibility & Safety: Our concept design shall have large windows so as to

increase the visibility of the driver so as to decrease the blind spots and at the same time increase the

safety.


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20” wheels on R/C model or use existing wheels: The existing wheels and tires from the R/C model car

will be utilized.

Acceptable leg & head room: The concept model shall have acceptable leg & head room as judged by

the iMike CAD model. iMike is a 95th percentile human model, similar to a standard mannequin, that will

be used in the CAD model to ensure that the interior dimensions such as the H-point are adequate and

that the location of interior features are optimized. The H-point (Hip-Point) is a standard seating

reference point for the automotive industry.

Technologically Advanced Interior: The interior cabin of the model shall incorporate the latest

technologies to be readily available in high end sports cars by 2012. This will include a personal

computer on the dash for the passenger as well as an LCD monitor in the center console to control the

temperature climate as well as the entertainment system.

Sports Seats with Bolsters: The sport seats shall include bolsters so as to secure the driver and

passengers when cornering.

Racing Steering Wheel: A racing wheel shall be integrated into our final interior design. This will match

the customers’ expectations of what a sports car should include.

Luggage capacity: Please refer to the Concept Car Design Attributes for the reasoning behind

incorporating this feature. The luggage capacity shall be highlighted only in the CAD model and will not

be functional in the prototyped model.


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7 Target Market

The target market for this concept car design shall consist of the following:

• Males between the ages of 30-50 years

•

Individual Personal Income between $75,000 - $150,000

The market that we targeted as possible customers for our concept design is visualized in Figures 4

below.

Figure 4: Canadian Household Income

0

500,000

1,000,000

1,500,000

2,000,000

2,500,000

$0K -

$10K

$10K -

$20K

$20K -

$30K

$30K -

$40K

$40K -

$50K

$50K -

$60K

$60K -

$75K

$75K -

$100K

$100K -

$150K

$150K+

# o

f I n d i v i d u a l s

Personal Income [$]

Canadian Target Market

Canadian Personal Income Target Market


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8 Competitors

The list below outlines the different car manufacturers which have been highlighted as possible

competitors to our concept car design:

• Nissan GT-R

•

Chevrolet Corvette

• Porsche Cayman

• Porsche 911 Carrera

• Ford Shelby Mustang

• Tesla Roadster

• Fisker Karma

9 Benchmarking

For the concept car design, the Tesla Roadster was used as the primary benchmark. This was due to its

electric propulsion technology used within a sporty frame.

9.1 Battery Placement:

For the concept car design, the battery placement is one of the most significant issues encountered by

our group. Using a fully electric car places certain requirements on the design. These requirements

include a significantly larger battery pack than one which would be present in a Hybrid. Two different

battery placements were considered.


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Figure 5 : Tesla Roadster`s Battery Placement

The first battery placement considered, places the battery pack behind the passenger compartment as

in the Tesla Roadster. This layout is very similar to the mid-engine layout of conventional sports cars

which use gasoline combustion engines.

Figure 6 : Cadillac Converj`s Battery Placement

The above figure outlines the Cadillac Converj`s battery placement. The Cadillac Converj uses a different

propulsion technology than that of the Roadster. It is an electric vehicle with a gasoline engine

generator to recharge the batteries. The Converj uses a front engine, front wheel drive configuration. As

can be seen in the figure above, the battery pack is placed in the center tunnel.


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9.2 Electric Motor:

Figure 7 : Tesla Roadster`s Electric Motor Placement

In order to be consistent with our rear wheel design considerations, the electric motor shall be placed in

line with the placement shown in the Tesla Roadster as shown in the figure above.

9.3 Dimensions:

DIMENSIONS

Overall Length (in/mm) 155.4 / 3946 Track-rear (in/mm) 59.0 / 1484.5

Overall Width - incl. mirrors

(in/mm)72.9 / 1851 Curb Weight (lbs/kg) 2723/1238

Overall Height (in/mm) 44.35 / 1126.5 Leg Room (in/mm) 42.0 / 1067

Wheelbase (in/mm) 92.6 / 2351 Head Room (in/mm) 36.7 / 932

Track-front (in/mm) 57.7 / 1455.6 Shoulder Room (in/mm) 26.0 / 660

Table 3 : Tesla Roadster Dimensions


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Our concept car design shall be based on the Tesla Roadster`s dimensions as outlined in the Table

above.

WHEELS & TIRES

Front Wheel 16 X 6

Front Tire 175/55 R16

Rear Wheel 17 X 7.5

Rear Tire 225/45 R17

Table 4 : Tesla Roadster Wheel & Tires Dimensions

In line with the big wheels with low profile tires intended to be used in our design, the Roadster`s

dimensions shall be used as the benchmark as shown in the table above.


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9.4 Specifications:

PERFORMANCE SPECIFICATIONS

Acceleration 0 to 60 mph in 3.9 seconds

Range 227 miles EPA cycle

Top Speed 125 mph / 201 km/h (electronically limited)

Charging As short as 3.5 hours for a complete cycle (partial cycles are faster)

TECHNICAL SPECIFICATIONS

BatteryCustom micro-processor-controlled lithium ion battery pack with useful life in

excess of 100,000 miles

Motor

3-phase, 4-pole AC induction air-cooled electric motor with variable frequency

drive, Redline 13,000 rpm, regenerative “engine breaking”

Horsepower (hp / kW) 248 / 185; 5000-8000 rpm

Torque (ft/lb. / N·m) 276 / 375; 0-4500 rpm

Transmission Single speed

Chassis Bonded Extruded aluminum monocoque chassis

Brakes 4-wheel ventilated disc brakes with ABS

Body Carbon fiber

Table 5 : Tesla Roadster Specifications

The concept car design will attempt to match the benchmarked specifications of the Tesla Roadster

shown above.


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10 Work Flow Section

10.1

Initial Extrusion

As the research phase of the project was completed with the 9-Box Geometric Model Design Attributes

selected, we were ready to start the CAD modelling phase of our design. In Concept Version 1.0, see

Figure 8 below, we faced various problems caused by the modelling limitations in Autodesk Inventor.

Problems such as: non-feasible fillets, unwanted surfaces and difficulty in modelling certain features.

Our first design was not chosen for many reasons. Most important of all, it failed to meet certain criteria

established before.

Figure 8 : Concept Version 1.0

Before initiating the 2nd (final) version of the model we decided to follow a different approach to

model the car which was more efficient and that addressed some of the initial approach’s shortcomings.

We decided to model the car in two halves as two separate extrusions. The top half, the greenhouse,

consisted of the front & rear windshields, windows and roof. The top and bottom half of the car was

separated by the beltline which is the line going from the hood, following the bottom edge of the

windows and continuing to the trunk. The bottom half included the remainder of the car from the

beltline and down. The profile extrusions of the top and bottom halves can be seen in Figure 9 & Figure

10 respectively. This approach allowed us to individually form, edit and modify the two sections of the

car. It was possible to increase the number of initial extrusions to three or even four to increase the


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level of detail. However, we decided to limit the initial extrusions to two to keep the model as simple as

possible to avoid any possible prototyping problems. Figure 11 shows the initial rough model of Concept

Version 2.0. It is evident from comparing Figure 8 and Figure 11 that the approach used to model

Concept Version 2.0 was significantly more realistic as noticeable by the depth of the roof top.

Figure 9: Top Half (Greenhouse) Profile Extrusion

Figure 10: Bottom Half Profile Extrusion

Figure 11 : Concept Version 2.0


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10.2 Necessary Cuts

In order to achieve the desired shape, we needed to smooth some of the surfaces and delete some

unwanted edges. One of the lessons learnt while using the CAD software was to correctly apply tools in

a certain order in order to achieve the desired result. Following the initial profile extrusions, we utilized

three major cuts done on the profile extrusions to define the shape we were after.

10.2.1 Top Cut

This was applied to both the top and bottom half profile extrusions. For the top half, see Figure

12, this cut helped define the edge of the green house from a bird`s point of view. For the

bottom half extrusion, the cut was used to round the front and rear ends and to create an

aggressive silhouette by making the car narrower from the area around the door while leaving

the edges near the wheels wider as can be seen in Figure 13. These cuts had to be carefully sized

to allow to the model to successfully fit the existing chassis. Too deep of a cut would result in

shortening the length of the model.

Figure 12: Top Half (Greenhouse) Top Cut


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Figure 13: Bottom Half Top Cut

10.2.2

Front Cut

This cut was applied to only the top half of the car to taper the edge of the windows relative to

the side of the car. The angle of this cut was carefully chosen since it would directly affect the

head room in the interior. We considered both comfort level of i-Mike and for aesthetic appeal

and chose an angle of 12.5°. Figure 14 below shows the details of this cut extrusion.

Figure 14: Top Half (Greenhouse) Front Cut


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10.2.3

Revolved Cuts

To create a realistic look to both the front and rear ends of the car, we utilized revolved cuts.

We used projected geometry from the bottom half profile of the car, to create the revolved

cuts. Figure 15 & Figure 16, show the revolved cuts for the Rear and Front Ends of the car

respectively.

Figure 15: Rear End Cut-Revolve

Figure 16: Front End Cut-Revolve


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Note, as mentioned above, it is extremely important to follow the sequence of these cuts since changing

the sequence would dramatically change the output.

10.3 Surfacing: Chamfers Edges & Surface Fillets

At this point our model was ready to be surfaced. Many surfaces had to be adjusted and some had to be

deleted. Three major tools were employed to achieve this goal. Most of the edges were filleted to a

small radius. This was necessary for two reasons: 1- to enhance the appearance of the model and 2- to

be able to successfully rapid prototype the model, since sharp edges would create problems during

rapid prototyping. Many of the edges we filleted in a variable manner using the variable edge fillet tool.

This tool would allow us to apply different fillet radii to different edges hence the term variable edge

fillet. An obvious example of this can be seen on the back lights of Version 1.0.

Figure 17: Location of Surface Fillets

We also needed smooth continuous surfaces joining each other. This was done by using the surface fillet

tool. This tool would allow us to merge various surfaces with different elevations into one smooth 3D

FRONT FENDER

REAR FENDER

SIDE FEATURE

FRONT LIP


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surface. The back window and fender flares are examples of this tool. Figure 17 above shows the

location of the surface fillets employed in our design. Chamfers were also used on the side door panels

to create a slanted plane which would give the model more depth. After finalizing all the changes the

extra surfaces had to be removed. Surfaces such as: side windows, back window, windshield, bottom

face and the head lights. This was simply achieved by utilizing the “delete face” function on inventor

2009. It is important to note that after employing this feature, the model appeared to be shelled. This in

fact was not the case since the program defines the surfaces shelled with no thickness. This could create

problems with the rapid prototyper since the machines will not recognize these shelled surfaces. A final

version of the model is shown below in Figure 18.

Figure 18: Final Model done on Inventor


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11 Inventor to Alias to Catalyst

11.1

Inventor’s Failure to Shell and Why

Our many efforts to shell our model in inventor were unsuccessful. The program would recognise the

entire model as a whole block, but would fail in creating the shell. This was understandable due to the

complex geometry of the model. Next we decided to try and offset the surfaces which would also result

in a shell. While doing so, we were able to offset individual faces successfully but were again

unsuccessful in trying to offset the entire structure. This is explained as follows. Consider the following

sketch in Figure 19. Suppose the two lines on the left side of the figure representing the side profile of

the two surfaces to be offset/thickened. The method that Inventor uses to thicken surfaces is by

applying a defined offset (e.g. 2 mm) in the desired direction (inward or outward). This offset is created

normal to the surface. Hence, while offsetting two adjacent surfaces there will be an overlap (shown in

red) which causes the error. Due to this reason Inventor was unable to create a shell after all.

Figure 19: Offset error

11.2

Alias to the Rescue

The only available option to shell our model was to use a different program. Alias Studio, which is mainly

used for surface designing especially car design, was used to reach this goal. Different types of files are

interchangeable between Alias and Inventor such as step files (.STP). It is important to remember that

due to dimension limitations of the rapid prototyping machine we had to cut the model in to three


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pieces to be within the required length dimensions. Creating three separate parts made the

manufacturing possible as well as minimized the cost of prototyping (since the three pieces could be

oriented in an optimal direction in space).The following instructions were done on all three parts in

order to import and shell each part.

1.

Save each part as STEP AP214. Do not include sketches.

2.

Open and import the STEP files into Alias Studio.

3.

In case of any improperly trimmed surfaces:

a.

Select everything and perform Surface Edit Unstitch (don't keep originals)

b.

Delete the improper surfaces

c.

Mirror the good surface from the other side if possible

d. Select everything and perform Surface Edit Stitch (don't keep originals)

4.

Mesh NURBS to Mesh using: Quality=0.03 mm and max length=2 mm.5. Mesh Offset= 3 mm. If it offsets in the wrong direction then Mesh Reverse Mesh

Orientation and offset again.

6. Select the offset Mesh Export to STL ASCII

The main fact which made this offsetting possible in Alias was the creation of the mesh. Triangular

meshes were used to define the surfaces. This allows the program to offset each mesh which results in

the entire surface being offset. Also by using the mesh function we can eliminate the overlapping

problem which we faced in Inventor. Instead of considering each face as an individual surface (Inventor),

Alias recognises each face as a series of refined meshes (quality 0.03).

12 Surface Continuity

After prototyping the final model, which consisted of three parts, we faced a major problem with the

middle section. It seemed as some surfaces were missing. After investigating the STL files on Catalyst we

realized some of these errors were visible in the preview and some were not. The flaws that were not

shown on the preview were simply machining errors, while the others were a result of surface

discontinuity. A surface typically has point continuity (no gaps), tangent continuity (no sharp angles) and

curvature continuity (no sharp radius changes). The presence of a point discontinuity, which later on

became a surface discontinuity due to the creation of the mesh, was the main reason for these


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discrepancies. One way to avoid this from happening is to insure the number of the surfaces is kept to a

minimum.

13 Car Features

13.1

Side/Back Cameras – A Safer Drive

In our concept, the side/back view mirrors were replaced by side/back view cameras. This simply means

that there will be cameras installed on both sides of the car as well as the back window. This concept,

which is already available in many high end cars, is advantageous in various ways. The first and foremost

advantage is that it eliminates the existence of blind spots since the designer could easily define the

range of visibility as desired. Also, cameras need not be as large as mirrors; therefore improving the

aerodynamics of the car. It is widely known, as it is mentioned on every mirror, that objects appear

closer than what they actually are in the side mirror. This could impair the judgement of the driver in

making decisions such as changing lanes and could possibly lead to accidents. On the other hand, using

side view cameras would fix the distancing issues associated with side view mirrors. Many other

integrated features can be added to the car using these mirrors; for instance, the live feed from the

cameras, both side and back, can be constantly used along with a motion detection software and warn

the driver if an object is getting too close to the car. In some cases this could prevent accidents and give

the driver more time to respond.

13.2 Bigger Windows, Bigger View

Since we are dealing with a fully electric car where there will be very little dedicated engine space due to

the relatively small electric motors used to drive the wheels, we had some room to spare in the front

and back end of the car. This extra space was integrated into larger windshield and back window. Being

able to see the road wide and clear can make a big difference in the quality and safety of driving,

especially in case of sports cars where high speeds are expected.


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14 Evolution of Interior Tub

14.1 Stage 1

To start the design process for the interior, a concept sketch was made to visualize the interior ideas

that were developed as shown in the figure below.

Figure 20 : Initial interior concept sketch

14.2 Stage 2

At this stage, the interior hub was made with its main components. As can be seen, the finer details of

the interior (LCD monitors, Gear Shifter, Center compartment, Cup Holders) had not been added yet.

Figure 21 : Interior Cabin


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14.3 Stage 3

In stage 3, details to the hub were added such as LCD monitors, a gear Shifter, center compartment and

cup holders.

Figure 22 : Finished Interior Cabin with center console detail

14.4 Stage 4

At this stage, colours were added to the hub along with the carpeting. As you can see, the main colour of

the hub is tan, and the trim is mainly black. We also used chrome for some of the trim.

Figure 23 : Finished Interior Cabin with Colour


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14.5 Comparison between initial sketch concept and finished interior cabin

Figure 24 : Comparison between initial sketch and final interior cabin

The figure above compares our initial sketch with our final painted interior cabin. As can be seen, the

final design is very similar to our initial concept where we believe we successfully incorporated our ideas

into 3D.

15 Evolution of Steering Wheel

15.1 Revision 1

The first revision of the steering wheel consisted of a sport concept wheel with fireball logo to indicate

the car name. However, after deliberation, it was found that this logo would be much too complicated

to be prototyped at such a small scale.

Figure 25 : Steering Wheel Revision 1


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15.2

Revision 2

The second revision incorporated better steering spoke placement for easier use as well as a more

aesthetically pleasing design. The fireball logo was also replaced with a logo which would be easier to

prototype.


15.3 Revision 3

The third and final revision added minor parts to the past revision. The logo was redesigned to

incorporate the “PHI” letter which is part of our car name. As well, the rear part of the steering wheel

was designed to be able to properly attach the wheel to the vehicle.



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16 iMike Sizing

Figure 28 : iMike

In designing our conceptual automobile design, we had to insure that it would be feasible for

implementation. One way to ensure that was to prototype the interior design with the passenger in

mind. iMike was used to aid us in sizing the interior,. iMike is a 95 th percentile human model which aids

in the design of the interior. It is similar to a standard mannequin who is used in the automotive industry

to insure that the interior dimensions are adequate as referenced by the H-point of the driver and

passenger. The H-point (or hip-point) is the relative vertical location of an occupant's hip, specifically the

pivot point between the torso and upper leg portions of the body, either relative to the floor of the

vehicle or relative to the height above pavement level. With the help of iMike, we were able to ensure

there was adequate visibility from the vehicle into traffic as well as predicting the driver eye level as

shown in Figure 28 & Figure 29 below. Sports cars usually have lower H-points, in essence so as to

enhance the driving experience by being as close to the road as possible.

http://en.wikipedia.org/wiki/Hip_%28anatomy%29http://en.wikipedia.org/wiki/Hip_%28anatomy%29


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Figure 29 : Driver’s view from iMike position

Figure 30 : Driver's view from iMike position 2


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iMike was scaled down to 1/12th of its original size in order to fit our 1/12th scale model. As can be seen

in the figures below, iMike seems to be comfortable in the seating configuration effectively reaching

both the steering wheel and the shifter as well as having enough leg room.

Figure 31 : Concept car seating configuration


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Figure 32 : Concept car available leg room


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17 Lessons learnt

In designing the concept car, there were a couple of lessons learnt that we believe would be useful to

any upcoming engineering students interested in partaking in such a project.

1.

The simpler the better. When designing a car, there is more than what meets the eye. Dr Spencehas always informed us to keep the design simple since implementing all the features we initially

planned would have complicated the project beyond the time given.

2.

Working with specialized car design software like Alias Studio is preferred. We created our

design in Inventor but we soon realized that although we had the added advantage of knowing

how to design in Inventor, the program had some limitations. These problems mainly included

trying to shell the exterior so that it would only have a thickness of a couple of millimetres. We

were unable to fix the exterior in Inventor and as a result had to export it into Alias Studio

where the process was done. It is recommended to perform all the CAD work in Alias Studio so

as to take advantage of the power of Alias Studio as well as being able to effectively shell thedesign.

3. There are limits to what the 3D printer is capable of prototyping. We designed everything while

factoring in the machine’s thickness limit which was understood to be 0.01 inch. If this fact was

not taken into consideration then there would have been noticeable details missing in the

completed parts.

4. One more issue to keep in mind is surface discontinuity. While prototyping our concept, there

were flaws detected with some parts of the exterior. Due to surface discontinuities in the CAD

model, the rapid prototyping machine was unable to create the exterior as expected. The result

was support material integrated into the areas where there was supposed to be ABS plastic.

5. After the completion of the model it was noticed that the surface finish was not of great quality.

This is expected from the prototyping machine. While layers are being laid on top of each other

the inaccuracy of the machine ultimately results in a rough surface with small differences in

elevation in areas in contact with the support material. Before we proceed to painting the

model some sanding and plastering was done to achieve the desirable surface finish.


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Appendix A – Dealer Survey Questions

1. Rank the following criteria for buying a sports car. Score from 1(not important) -10(very important)

- Power

- Aesthetics

- Fuel Efficiency- Level of Luxury (Power seats, power windows, heated seats, A/C)

2. What are some trends you are seeing in regards to what customers want in their vehicles?

3. In terms of aesthetics, what are key features that customers like?

(Ex. Wheel Size, Color, Spoilers, # of exhaust pipes)

4. How do you feel in regards to joy stick steering systems? Do you think customers would be able to

conform to a new system like this?

(Brake, gas, steering all on one joystick)

5. How important is fuel efficiency (environmental impact) to your customers?

6. Do your customers prefer coupes or convertibles?

7. What is the level of interest for electric or hybrid sports cars?

8. What is a sports car you offer which is ideal to your customers in regards to space requirements

(Leg room, head room, trunk size)?

9. What is the preferred engine layout to your customers (front, mid, rear engine)?


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Appendix B – Dealer Survey Results

The following is a summary of feedback from the sales departments of various dealerships collected on

January 14th, 2009. The feedback contains responses to our survey questions as well as from additionalcomments regarding sports cars.

Summary from Dealer Interviews

BMW

Survey Question Feedback:

1.

Rankings: 1st - Aesthetics (customers willing to sacrifice comfort for looks)

2nd - Power

3rd - Level of Luxury

4th - Fuel Efficiency (customers don’t really care about it)

2. Trends: - Personalization; everyone want to make their car unique via aftermarket rims,

spoilers, body kits, etc...

- More and more automakers have a variation of BMW’s I-Drive (a computer

user interface used to control secondary vehicle systems such as climate

control, the audio system, the navigation and communication systems)

- Keyless entry (smart keys)

-Dual-clutch transmissions

- Small thick steering wheel

3. Aesthetics: - Big wheels with low profile tires

- Black (1st) and white (2nd) are the popular colours; grey is a really good for

showing the lines of the exterior (most BMW concept cars are gray in colour forthis reason)

- Dual/quad exhaust tips

4. Joystick Steering System: can’t see customers embracing the technology; customers want to feel

connected to the road via a physical linkage; such technology would feel artificial

5.

Fuel efficiency: rank a 3 or 4 on a scale of 1 to 10

6.

Coupe preferred over convertible

7. Level of interest for hybrid sports cars: rank a 1, 2, maybe 0 on a scale of 1 to 10 (hybrids are

viewed as sacrificing performance for fuel efficiency); electric cars are the future (lots of torque)

8. Interior space requirements: good leg and head room; trunk space for 2 sets of golf clubs (1/10)

9.

Front engine layout

Additional Comments:

50/50 weight distribution

High horsepower; efficient power via turbo or supercharging

HONDA



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1.

Rankings: 1st - Power (10/10)

2nd - Aesthetics


4th - Fuel Efficiency (5/10)

2. Trends: - Bluetooth

- Voice activated navigation system

3.

Aesthetics: - Wheels; the bigger the better

- Black is the most popular colour followed by red

- Leather interior

3. Joystick Steering System: NO

8.

Interior space requirements: trunk space - minimum of an overnight bag

9.

Mid or front-engine layout

NISSAN


1.

Rankings: 1st - Power

2nd - Aesthetics


4th - Fuel Efficiency

4. Aesthetics: - Big wheels with low profile tires

- Black and red the popular colours

5. Joystick Steering System: NO

6. Fuel efficiency: not important

8. Interior space requirements: trunk space - minimum of 2 sets of golf clubs

9.

Front or mid-engine layout

Additional Comments:

The 350Z has a 53/47 weight distribution; which shifts to 50/50 once the car is in motion

Leather interior; suede inserts in seat back for convertibles to absorb sweat

If you could design a sports car, what would it be like?

Tight creases on the exterior; with few reflectors for a clean, sleek look

Low to the ground

Lots of power; high power-to-weight ratio

2 available transmissions

AWD

Front engine layout

Hatchback body style for a better shape profile

50/50 weight distribution


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Appendix C – Sample Work-In-Progress Exterior CAD Drawings


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Appendix D – Final CAD Images


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