Shell Eco-Marathon 2013 urban concept vehicle: …...International Project 14.12.12 2 Executive...

International Project

Shell Eco-Marathon 2013 urban

concept vehicle: Project report

Mechanical Engineering

Author: Devon Barkway (184787) Supervisor: Per Ulrik Hansen

Pavel Sokolov (185352)

Jose Antonio Rodriguez Rodriguez (184882)

Juan Carlos Hurtado Sierra (181836)

Viacheslav Rostovtcev (184885)

Michiel Bosch (184793)

Kriss Lidumnieks (184852)

Josué Martínez Peña (184861)

Ana Isabel San Agustín (184888)

Ioana Costin (188052)

Project: Shell Eco-Marathon 2013 urban concept vehicle

Date: 14.12.12


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Executive Summary

The particular challenge that faces us as a team is to design, build and race an urban concept vehicle

for the Shell Eco Marathon 2013. The project has been executed according to the assumption that it

will be split in to two phases over two academic semesters. The first phase is reported below. The

project in its entirety that we have undertaken is by no means a small one and requires a lot of man

hours. New systems will need to be developed; unique parts will need to be designed and manufac-

tured; solutions to unseen problems will need to be solved; all of these challenges being tackled

whilst under the umbrella requirement of EFFICIENCY. Efficiency is the main issue; how to race the

required distance using as little electrical power as possible.

The answer to the issue of efficiency is to reduce the amount of power needed in order to propel the

vehicle to the required standards, i.e., to get as many kilometres as possible for each kilowatt hour of

electrical power. In order to do so, we have effectively had to develop a vehicle ‘from scratch’ in or-

der to meet these exacting standards. We had to first research current solutions, analyse our initial

concept ideas and proceed forward in to the main design phase with the knowledge we gained, albe-

it limited.

The group has done so by focusing our attention on one key factor, namely weight. The lighter the

vehicle, the less power needed. Therefore, we have in every area of the vehicle strived to reach solu-

tions that require only the essential components & parts and to use materials that have an excellent

strength to weight ratio (such as carbon fibre, flax fibre, balsa wood, composites of said materials,

polycarbonates, aluminium and varying grades of steel only where needed). We have used FEM anal-

yses in critical areas in order to reduce thicknesses and strip away material where it is not needed.

We have sourced parts and components based mainly on their light-weight characteristics, for exam-

ple, a mountain bike braking system and a carbon fibre racing seat. As the project proceeded further,

more problems emerged with trying to incorporate all of these bespoke systems and elements in to

one, viable, working, efficient machine. These problems were solved with good communication be-

tween individual group members, the groups themselves and more bespoke solutions, for example,

custom bearing pins and fasteners.

It was also decided to use an existing technology of hub motors in order to drive the vehicle, thus

eliminating the need for very heavy drive train components such as shafts, clutches, differentials and

transmissions. This was possibly the greatest contributor towards cutting the overall weight of the

vehicle and thus increasing efficiency. Further development of the incorporation of these motors will

need to be done in the second semester.

Another factor that was taken in to account briefly was the aerodynamic aspect of the vehicle design,

due to the air resistance and drag forces that can have a big impact on the overall efficiency of the

vehicle. The concept and design of the bodywork has as much as is practically possible adhered to

the principle of reducing theoretical resistive forces to an absolute minimum. For now, i.e., in phase

1, the aerodynamic design has been only theoretical and based on some rough air resistance calcula-

tions. In phase 2, further, more accurate studies and analyses of the aerodynamics of the vehicle will

be done in order to refine the shape to what the team sees as an ideal combination of performance

and design.


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The results, i.e., the answers to the problems that were faced, have been more than acceptable in

the opinions of all group members. In order to achieve the project goals required many hours of hard

work and determination by many individuals in a group-work context. In the beginning of the project

we realised the necessity of good group organisation as there were a total of ten members; a large

amount of people to be working as a group. We had to learn very quickly how to manage ourselves,

other members and the group as a whole in order to achieve our purposes. We feel that we have

gained valuable experience within the context of project based group work that we can take in to our

future careers.

We believe that by working as an organised group, we have created a solution for the problem of

how to create an efficient as possible urban concept vehicle within the context of a marathon race.

As mentioned previously, project and team organisation was good and the members of individual

groups worked well together under our project manager Kriss Lidumnieks, who was the driving force

and motivation behind this endeavour. In retrospect, it would have also been wise to have sub-

managers for each separate group in order to increase individual work efficiency.

A recommendation from the team is that this urban concept vehicle that we have developed for the

Shell eco marathon can (with our permission) be further worked upon in the coming years by stu-

dents of VIA University College, using our research, development and accomplishments as a founda-

tion for any further development. It would be a welcome legacy for our efforts.


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Table of Contents

Summary ................................................................................................................................................. 2

Table of Images ....................................................................................................................................... 5

1. Introduction......................................................................................................................................... 8

2. Literature survey ................................................................................................................................. 9

3. Enabling technologies ....................................................................................................................... 19

4. Own Work: Group 3 .......................................................................................................................... 20

4.1. Brake System, by Devon Barkway .............................................................................................. 20

4.2. Steering Bracket, by Devon Barkway ......................................................................................... 22

4.3. Braking Pedal, by Pavel Sokolov ................................................................................................. 29

4.4. Exterior design, by Rostovtcev Viacheslav ................................................................................. 33

4.5. Steering arm support, by Rostovtcev Viacheslav ....................................................................... 35

4.6. Steering system, by José Antonio Rodríguez Rodríguez ............................................................ 39

4.7. Rear attachment & Rear Braking, by Juan Carlos Hurtado Sierra .............................................. 45

5. Own work: group 4 ............................................................................................................................ 50

5.1 Roll cage, by Michiel Bosch ......................................................................................................... 50

5.2 Safety equipment, by Ana Isabel San Agustín ............................................................................. 55

5.3 Safety equipment, by Ioana Costin ............................................................................................. 67

5.2.1 Seat selection, fitting and anchoring .................................................................................... 67

5.4 Chassis/Cockpit of urban concept vehicle, by Kriss Lidumnieks ................................................. 80

5.4.1 Evaluating and choosing the concept .................................................................................. 80

5.4.2 Design ................................................................................................................................... 82

5.4.3 Materials .............................................................................................................................. 84

5.4.4 Structure ............................................................................................................................... 85

5.4.5 Manufacturing ...................................................................................................................... 88

5.5 Windshields, by Kriss Lidumnieks ................................................................................................ 89

5.5.1 Design ................................................................................................................................... 89

5.5.2 Material ................................................................................................................................ 89

5.5.3 Manufacturing ...................................................................................................................... 89

5.5.4 Attachment to Body ............................................................................................................. 90

5.6 3D model of the bodywork, by Josué Martínez Peña ................................................................. 92

5.6.1 Making the frame ................................................................................................................. 92

5.6.2 Modeling Phase 1 ................................................................................................................. 94

5.6.3 Phase 2 ............................................................................................................................... 101

5.6.4 Phase 3 ............................................................................................................................... 111

5.6.5 Conclusion .......................................................................................................................... 115

6. Conclusion ....................................................................................................................................... 116

7. Further work .................................................................................................................................... 119

Appendices

Appendix 1: Own work

Appendix 2: Other References


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Table of Images

Image 1: Hope M4 brake calliper. ......................................................................................................... 20

Image 2: Hope M4 post mount calliper render ..................................................................................... 21

Image 3: Brake disc render. ................................................................................................................... 21

Image 4: IS (International Standard) hole dimensions. ......................................................................... 21

Image 5: Preliminary rough design sketch. ........................................................................................... 22

Image 6: Calliper mount from post mount to IS. .................................................................................. 22

Image 7: First concept model of steering bracket. ............................................................................... 23

Image 8: Design sketch of original bracket concept. ............................................................................ 23

Image 9: Concept sketch of a new, revised bracket. ............................................................................ 24

Image 10: Initial, simplified steering bracket model used in FEM analysis........................................... 24

Image 11: Free body diagrams, predicted acting forces and subsequent reaction forces applicable to

the steering bracket. ............................................................................................................................. 25

Image 12: Applied forces and boundry conditions; plate thickness = 8mm. ........................................ 26

Image 13: FEM results for 8mm and 4mm plate thicknesses using ‘Ansys 14.0’.................................. 27

Image 14: Braking lever with master cylinder ....................................................................................... 29

Image 15: Mounting .............................................................................................................................. 30

Image 16: Mounting plate ..................................................................................................................... 31

Image 17: Rail ........................................................................................................................................ 31

Image 18: Pedal arm ............................................................................................................................. 32

Image 19: Early concept sketches ......................................................................................................... 33

Image 20: Refined concept sketches ..................................................................................................... 33

Image 21: Combination of Image 19 designs. ....................................................................................... 34

Image 22: Final concept sketch with altered rear. ................................................................................ 34

Image 23: 3DS Max model renders. ...................................................................................................... 34

Image 24: FEM analysis results using Solidworks. ................................................................................ 35

Image 25: CAD model and assembly using two arms. .......................................................................... 36

Image 26: Bearing drawing. .................................................................................................................. 36

Image 27: Steering support arm with associated fastenings and brake lever. ..................................... 37

Image 28: FEM analysis for arm with thickness of 7.5mm.................................................................... 37

Image 29: Displacement fro arm with thickness of 7.5 mm. ................................................................ 38

Image 30: Turning circle angle. ............................................................................................................. 39

Image 31: CAD representation of turning circle angle. ......................................................................... 40

Image 32: Steering arm. ........................................................................................................................ 40

Image 33: Steering arms. ...................................................................................................................... 41

Image 34: CAD dimensioning. ............................................................................................................... 41

Image 35: Rack and pinion system. ....................................................................................................... 42

Image 36: Steering column universal joint and shaft. ........................................................................... 42

Image 37: Steering wheel model. ......................................................................................................... 43

Image 38: Rack frame. ........................................................................................................................... 43

Image 39: Steering wheel frame. .......................................................................................................... 44

Image 40: First freehand drawing. ........................................................................................................ 45

Image 41: Inventor 3D drawing of first design. ..................................................................................... 45


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Image 42: Inventor 3D drawing of cicular design. ................................................................................ 46

Image 43: Inventor 3D Cross Section of Cockpit. .................................................................................. 46

Image 44: Inventor 3D drawing of second cicular design. .................................................................... 46

Image 45: Inventor 3D drawing of Axle Holder ..................................................................................... 46

Image 46: Inventor 3D drawing of accessory for the bracket ............................................................... 47

Image 47: Inventor 3D drawing of bracket ........................................................................................... 47

Image 48: Inventor 3D fasteners to the bracket. .................................................................................. 47

Image 49: Inventor 3D assembly Bracket & Attachement. ................................................................... 47

Image 50: Inventor 3D assembly nuts+washers wheel. ........................................................................ 48

Image 51: Inventor 3D assembly external connection.......................................................................... 48

Image 52: Inventor 3D assembly back inner connection ...................................................................... 48

Image 53: Inventor 3D Complete assembly of rear axle. ...................................................................... 49

Image 54: 3D assembly in SolidWorks. ................................................................................................. 50

Image 55: Roll panel idea sketch. .......................................................................................................... 51

Image 56: Roll bar idea sketch. ............................................................................................................. 51

Image 57: Roll frame idea sketch. ......................................................................................................... 52

Image 58: Carbon fibre monocoque. .................................................................................................... 52

Image 59: FEA of the rollbar .................................................................................................................. 54

Image 60: Simulink model for motor power calculation. ..................................................................... 62

Image 61: Simulink model resultant outputs. ....................................................................................... 64

Image 62: Selected hub motor specifications. ...................................................................................... 66

Image 63: TB1 mounted bracket ........................................................................................................... 68

Image 64: Chassis dimension ................................................................................................................ 69

Image 65: Seat dimension ..................................................................................................................... 69

Image 66: Anchoring kit ........................................................................................................................ 70

Image 67: Schroth Racing 5 point seatbelt ........................................................................................... 70

Image 68: Dimensions Profi III-5 seatbelt ............................................................................................. 71

Image 69: Shoulder belt connection to bar .......................................................................................... 72

Image 70: Bar with brackets Source: bracket designed by Michiel Bosch ............................................ 72

Image 71: Bar on the chassis Source: chassis designed by Kriss Lidumnieks ........................................ 72

Image : ap elt- olt in racket- olt 0 .......................................................................................... 73

Image 73: Bolt in bracket for anti-sub belt ........................................................................................... 73

Image 74: Side view-shoulder, lap and anti-sub seatbelts .................................................................... 74

Image 75: Top view chassis seat brackets sketch ................................................................................. 75

Image 76: Fire extinguisher bracket fitting. .......................................................................................... 76

Image 77: Front and lateral view. ......................................................................................................... 77

Image 78: Side view-visibility test ......................................................................................................... 78

Image 79: Top view-visibility test .......................................................................................................... 78

Image 80: Exit space .............................................................................................................................. 79

Image 81: Bulkhead and main dimension representation .................................................................... 82

Image 82: Luggage space and dimensions ............................................................................................ 83

Image 83: Composition of sandwich structure ..................................................................................... 84

Image 84: the dimensions of profile of cockpit ..................................................................................... 85


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Image 85: Free Body diagram of the simplified structure of cockpit .................................................... 86

Image 86: Shear stress diagram ............................................................................................................ 87

Image 87: Bending moment diagram .................................................................................................... 87

Image 88: Design of the body. The shape and size of the windshields................................................. 89

Image 89: Drape forming process. ........................................................................................................ 90

Image 90: Typical Pop-Rivet Assembly .................................................................................................. 90

Image 91: Side view ............................................................................................................................... 92

Image 92: Main line ............................................................................................................................... 92

Image 93: 3D lines ................................................................................................................................. 93

Image 94: Silhouette ............................................................................................................................. 93

Image 95: 2D sketch lines ...................................................................................................................... 93

Image 96: 3D sketch lines ...................................................................................................................... 94

Image 97: Lofting ................................................................................................................................... 95

Image 98: Surface & curve lofting. ........................................................................................................ 95

Image 99: Projection ............................................................................................................................. 96

Image 100: Curves results. .................................................................................................................... 96

Image 101: Loft creation ....................................................................................................................... 97

Images 102: Boundary patches ............................................................................................................. 98

Images 103: Loft creation ...................................................................................................................... 99

Image 104: Curve sections .................................................................................................................. 100

Image 105: Lofted result ..................................................................................................................... 100

Image 106: Preliminary result ............................................................................................................. 101

Image 107: Non-continuous shape ..................................................................................................... 102

Image 108: Wheel arch curves ............................................................................................................ 102

Image 109: Remodelled wheel arch .................................................................................................... 103

Image 110: Lofting differences ............................................................................................................ 104

Image 111: New wheel arch results .................................................................................................... 106

Images 112: Irregularities .................................................................................................................... 108

Image 113: New surface ...................................................................................................................... 108

Image 114: The final model. ................................................................................................................ 112

Image 115: Trunk creation. ................................................................................................................. 112

Images 116: Inside trunk creation ....................................................................................................... 113


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1. Introduction

Background

According to European Commission statistics, the transport sector produces 20% of all greenhouse

gas emissions in the world. It is obvious that there is a need for new innovations in the sector of mo-

bility to reduce the impact on environment. The present situation in the transport sector is that vehi-

cles are grossly inefficient. It is important that during production of a vehicle, energy waste is re-

duced, which means that more eco-friendly and more energy efficient processes and materials are

used, while at the same time maintaining the safety, comfort and performance of the vehicle.

By joining our project between groups 3 and 4, we are applying to compete in the Shell Eco-

Marathon competition which will be held near Rotterdam in the Netherlands, from the 16th to 19th

of May, 2013. Our goal is to participate in the electric, urban concept car aspect of the competition,

where the car must comply with specific competition rules.

Purpose

The purpose of this project is to take the first steps towards winning the Shell Eco-Marathon in a

joint group effort by designing and building the bodywork, chassis and safety systems of an efficient,

lightweight, electric, eco-friendly, urban-concept vehicle which meets official competition rules. We

eventually aim to achieve a result of 280 km/kWh which would be 5% higher than the previous best

result.

Problem formulation

General

Is it possible for our group to design the mechanical aspects of the urban concept vehicle which has

an efficiency of 280 km/kWh before the project deadline according to the competition rules?

How do we organise our work tasks efficiently in order to meet the purposes of the project by the

project deadline?

How do we share our results and the results of the other groups between each other?

Shell Eco-Marathon: design of brakes, steering system and wheels; group 3

How to select an appropriate brake system?

How to design an appropriate steering system?

How do we integrate these systems into our vehicle?

How to design and select viable wheels for the vehicle?

Which materials will be used to reduce weight as much as possible without a negative impact on the

strength and stiffness of the vehicle?


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Shell Eco-Marathon: design of the chassis, bodywork and safety equipment; group 4

How to design a lightweight bodywork and chassis within the competition rules?

How will we connect the bodywork with the chassis?

Which materials will be used to reduce weight as much as possible without having a negative impact

on the strength and stiffness of the vehicle?

What kind of safety equipment we should use in order to comply with competition rules?

2. Literature survey

The following are parts from the official Shell Eco-Marathon rules which apply to our vehicle and

have been referenced in the report.

Article 20: driver weight, paragraph b:

“b) Drivers of UrbanConcept vehicles must weigh at least 70 kg in full driving gear, including commu-

nication devices and luggage item, prior to an attempt. Ballast must be fitted in the luggage com-

partment of the vehicle in the event the minimum weight requirement is not met. This ballast must be

provided by the Team, and must be effectively tied down and secured to the vehicle to ensure no

danger for the Driver in the event of collision or roll-over. It must be easily detachable for weighing.”

Article 21: helmets, paragraphs a and b:

“a) For practice and competition, Drivers must wear Motorcycle or Motorsport style helmets that

comply with the safety standards specified in Chapter II of the Official Rules of each Shell Eco-

marathon event (bicycle/riding/skating type helmets are not permitted). The helmet labels must be

clearly readable. Helmets worn by both the Driver and Reserve Driver will be subject to inspection.

b) Only full-face or three quarter helmets are permitted. Generally, the full-face and three quarter

style helmets can be affixed with face shields which are highly recommended. If a face shield is not

utilised, safety goggles are required. The helmets must correctly fit the Drivers; otherwise they will

not be approved for the event.”

Article 22: driver clothing, paragraphs a and b:

“a) All Drivers must wear a racing suit as the outermost layer of clothing (fire retardant highly rec-

ommended). Casual clothing and street wear are not permitted. Chapter II provides further guidelines

regarding the racing suit specifications and availability. Wearing synthetic outer clothes or underwear

is strictly forbidden for Drivers when seated in their vehicle.

b) Gloves and shoes are required and must be provided by the team; bare feet or socks only are pro-

hibited.”

Article 23: driver comfort, with paragraphs a through d:

“Please note that in the event of hot weather conditions high temperatures could be attained inside the vehicle, potentially affecting Driver comfort and / or causing heat stress. a) It is recommended to properly ventilate the inside of the vehicle to provide cooling to the Driver.


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b) It is recommended to provide sufficient drinking liquids to the driver for the duration of an attempt. If fluid containers are provided to the driver(s), these containers must be hands free, e.g. camel-back style or bottles secured inside the driver’s compartment with flexible feed straw. c) It is recommended to equip the vehicle with an effective sunscreen. d) The Organisers reserve the right to restrict individual driving time by any means at their sole discre-

tion, e.g. shortening the distance, requesting driver change (pit stop), limit maximum number of at-

tempts per driver per day, etc.”

Article 24: equipment and materials, with paragraphs a through h:

“Teams are required to provide and use the following at the event: a) Gloves for general work: leather or canvas material. b) Gloves for fuel or motor oil handling: Chemical resistant. c) Safety glasses for all Team members. (Disposable types are permitted). d) Hearing protection for all Team members. (Approved Earplugs or muffs). e) Duct tape to secure any cords or cables lying on the pit floor. f) Lift stands or appropriate raised platform for vehicle tuning and repairs. g) Own tools and materials. h) Each Team must provide an extinguisher for their paddock area with a minimum extinguishing

capacity of 1 kg in addition to the vehicle’s extinguisher suitable for “ABC” class of fires. The extin-

guisher must be accessible in the Team’s specific pit area in the garage. The extinguisher must be full,

and have a certificate of validity bearing the manufacturer's number, the date of manufacture, and

the expiry date.”

Article 25: vehicle design, paragraphs a through h:

“a) During vehicle design, construction and competition planning, participating Teams must pay par-ticular attention to all aspects of safety, i.e. Driver safety, the safety of other Team members and spectator safety. UrbanConcept vehicles must have exactly four wheels, which under normal running conditions must be all in continuous contact with the road. A fifth wheel for any purpose is forbidden. b) Aerodynamic appendages, which adjust or are prone to changing shape due to wind whilst the vehicle is in motion, are forbidden. c) Vehicle bodies must not be prone to changing shape due to wind and must not include any external appendages that might be dangerous to other Team members; e.g. pointed part of the vehicle body. Any sharp points must have a radius of 5 cm or greater, alternatively they should be made of foam or similar deformable material. d) The vehicle interior must not contain any objects that might injure the Driver during a collision. e) Windows must not be made of any material which may shatter into sharp shards. Recommended material: Polycarbonate (e.g. Lexan) f) Any cover of the energy compartment (engine / motor / transmission / battery, etc.) should be easy to open for quick inspection access. g) All parts of the drive train, including fuel tank, hydrogen system components, etc. must be within the confines of the body cover. h) All objects in the vehicle must be securely mounted, e.g. bungee cords or other elastic material are

not permitted for securing heavy objects like batteries.”

Article 26: chassis / monocoque solidity, paragraphs a through e:


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“a) Teams must ensure that the vehicle chassis or monocoque is solid. A monocoque is a construction that supports structural load by using an object's external skin as op-posed to using a frame. b) The vehicle chassis must be equipped with an effective roll bar that extends 5 cm around the driv-er’s helmet when seated in normal driving position with the safety belts fastened. c) This roll bar must extend in width beyond the driver’s shoulders when seated in normal driving posi-tion with the safety belts fastened. It is permissible to either use a tubular or panel type roll bar. If a ‘tubular roll bar’ is used, it must be made of metal. A panel roll bar is the rigid partition separating the cockpit from the engine compart-ment. Such a panel roll bar must be an integral part of the vehicle chassis or integrated in a mono-coque. d) Any roll bar must be capable of withstanding a static load of 700 N (~ 70 kg) applied in a vertical, horizontal or perpendicular direction, without deforming (i.e. in any direction). e) The vehicle chassis or monocoque must be wide and long enough to protect the driver’s body in

case of a frontal or lateral collision.”

Article 27: propulsion and energy storage system isolation, paragraphs a through e, bar d:

“a) A permanent Bulkhead must completely separate the vehicle’s propulsion and energy storage systems from the driver’s compartment. This means engines, fuel cells, fuel tanks, batteries (both propulsion and auxiliary), hydrogen cylin-ders, super capacitors, etc. must be placed outside the driver’s compartment behind the bulk head. The purpose of this bulkhead is that in the event of a fuel leak or fire, it prevents liquids and / or flames and / or smoke reaching the driver. Therefore, it is necessary to pay particular attention to avoid any gaps and holes between the body and the bulk head. It is recommended to seal gaps with materials such as metal / aluminium sheeting or aluminium tape. b) This bulkhead must be of fire retardant material and construction. c) In closed-top Prototype vehicles and in all UrbanConcept vehicles, the bulkhead must effectively seal the driver’s compartment from the propulsion and fuel system. e) The bulkhead must prevent manual access to the engine / energy compartment by the driver.”

Article 28: visibility, paragraphs a through d:

“a) The Driver must have access to a direct arc of visibility ahead and to 90° on each side of the longi-tudinal axis of the vehicle. This field of vision must be achieved without aid of any optical (or electron-ic) devices such as mirrors, prisms, periscopes, etc. Movement of the Driver’s head within the confines of the vehicle body to achieve a complete arc of vision is allowed. b) The vehicle must be equipped with a rear-view mirror on each side of the vehicle, each with a min-imum surface area of 25 cm² (e.g. 5 cm x 5 cm). The visibility provided by these mirrors, and their proper attachment, will be subject to inspection. An electronic device must not replace a rear-view mirror. c) An Inspector will check visibility in each of the vehicles in order to assess on-track safety. This In-spector will check good visibility with 60 cm high blocks spread out every 30° in a half-circle, with a 4 m radius in front of the vehicle. d) For UrbanConcept vehicles wet weather visibility is also mandatory ( Article 52:)”

Article 29: safety belts, paragraphs a through g, bar f:

“a) The Driver's seat must be fitted with an effective safety harness having at least five mounting points to maintain the Driver in his/her seat.


14.12.12 12

b) The mounting point(s) for the crotch strap(s) must be below the Driver’s torso to prevent the Driver from slipping forward. c) The 5 independent belts must be firmly attached to the vehicle's main structure and be fitted into a single buckle, specifically designed for this purpose. d) The safety harness must be worn and fastened at all times when the vehicle is in motion. e) The fitness for purpose of the harness and its fitting will be evaluated during technical inspection. For Prototype cars this will be done by raising the vehicle with the Driver on board using the safety harness for suspension. g) The UrbanConcept vehicle safety harness must be specifically manufactured for motorsport use.

(e.g. certified or compliant with FIA standards)”

Article 30: vehicle access, paragraphs a, d and e:

“a) It is imperative for Drivers, fully harnessed, to be able to vacate their vehicles at any time without assistance in less than 10 seconds. d) For UrbanConcept vehicles, the opening release mechanism must be easily and intuitively operable from the inside and the outside of the vehicle. The method of opening from the outside must be clear-ly marked by a red arrow and must not require any tools. e) It is forbidden to use adhesive tape to securely close the Driver’s opening from the outside.”

Article 31: horn, paragraphs a through c:

“a) Each vehicle must be equipped with an electric horn mounted towards the front of the vehicle, in such a manner that is effectively audible to other vehicles and track marshals. With the vehicle in normal running condition, it must emit a sound greater than 85 dBA when measured 4 meters hori-zontally from the vehicle. b) The horn must have a high tone (pitch) of equal or greater than 420 Hz. c) The horn must have a noise capacity/volume greater than 110 decibels (dBA).”

Article 32: on-board fire extinguisher, paragraphs a through d:

“a) Each vehicle must be fitted with a fire extinguisher (ABC or BC type). All Drivers must be trained in the use of said fire extinguisher. This extinguisher must have a minimum extinguishant capacity of 1 kg (2 lb for US application); equivalent size extinguishers are not permitted. It must be full and have a certificate of validity bearing the manufacturer's number and the date of manufacture or expiry. b) Plumbed-in extinguishers may be located in the engine compartment and must discharge into the engine compartment. Triggering systems must be located within the cockpit and be operable by the Driver in his/her normal driving position. c) Hand held extinguishers must be located within the cockpit and be accessible to the Driver once they have vacated the vehicle. These should be securely mounted to prevent movement while driv-ing/braking. In the event of a fire, Drivers should first exit the vehicle and then if possible, remove the extinguisher and attempt to extinguish the fire if safe to do so. d) The on-board fire extinguisher does not replace the need for an adequate fire extinguisher for the

team’s garage area.”

Article 33: driver position:

“For safety reasons, the head-first driving position is prohibited.”

Article 34: clutch and transmission, paragraphs b through f:


14.12.12 13

“b) For centrifugal / automatic clutches the starter motor speed must always be below the engage-ment speed of the clutch. c) For UrbanConcept only: The vehicle must have ‘idling capabilities’, i.e. the vehicle must remain sta-tionary with the engine running. d) For manual clutches the starter motor must not be operable with the clutch engaged. An interlock is required to facilitate this functionality. e) Please refer to Article 64: regarding starter motor requirements. f) The installation of effective transmission chain or belt guard(s) is mandatory. This is required to protect driver or technician when working on the car in the event of the chain or

belt breaking. It must be made of metal or composite material rigid enough to withstand a break.”

Article 36: sound level:

“The sound level of the vehicle must not exceed 90 dB when measured 4 metres away from the vehi-cle. Maximum sound levels will be measured and recorded at the start line and teams exceeding the per-

missible level will be notified with a request for correction within a reasonable timeframe.”

Article 37: emergency shut-down, paragraphs a and b:

“a) An emergency shutdown system, operable from both, the exterior of the vehicle and the interior driver position, must be permanently installed on all vehicles (not part of the detachable bodywork used to allow driver access). A red arrow (on a white background) at least 10 cm long and 3 cm wide at the widest point must be positioned on the vehicle body to indicate clearly the exterior position of the emergency shutdown actuator. This system must stop the engine / motor. b) For Battery Electric vehicles the emergency shutdown mechanism must provide a physical isolation

of the propulsion battery from the vehicle electrical system. If relays are used, the relays must be a

normally open contact type. The use of a power controller or other logic systems to drive an isolation

device is not permitted. It is suggested, but not required that the accessory battery be isolated as part

of an emergency stop action.”

Article 44: definition:

“Under the name “UrbanConcept”, Shell offers an opportunity to design and build fuel efficient vehi-

cles that are close in appearance to today’s production type passenger cars. UrbanConcept vehicles

must comply with the specific rule of the Shell Eco-marathon for this group. One particular feature of

this group is that vehicles competing in this group will require “stop & go” driving.”

Article 45: dimensions, paragraphs a through h:

“a) The total vehicle height must be between 100 cm and 130 cm. b) The total body width, excluding rear view mirrors, must be between 120 cm and 130 cm. c) The total vehicle length must be between 220 cm and 350 cm. d) The track width must be at least 100 cm for the front axle and 80 cm for the rear axle, measured between the midpoints where the tyres touch the ground. e) The wheelbase must be at least 120 cm. f) The Driver’s compartment must have a minimum height of 88 cm and a minimum width of 70 cm at the Driver’s shoulders. g) The ground clearance must be at least 10 cm.


14.12.12 14

h) The maximum vehicle weight (excluding the Driver) is 205 kg.”

Article 46: vehicle body, paragraphs a through j:

“a) Teams are requested to submit technical drawings, photographs or animations of their entire vehicle design to the organisers for approval at their earliest opportunity. This is strongly recommended to avoid upsets by failing the technical inspection at the event on grounds of design non-compliance. b) The body must cover all mechanical parts whether the vehicle is viewed from the front, the rear, the sides or from above. However, the wheels and suspension must be fully covered by the body when seen from above and up to the axle centre line when seen from front or rear. The covering for the wheels and suspension must be a rigid integral part of the vehicle body. c) It is prohibited to use any commercially available vehicle body parts. d) Access to the vehicle by the Driver must be as easy and practical as typically found in production type passenger cars. The “door” opening must have a minimum dimension of 500 x 800 mm. This means the door opening will be verified with a rectangular template of 500 x 800 mm. e) Any access opening mechanisms (e.g. doors) must be firmly attached to the vehicle body (e.g. by means of hinges, sliding rails, etc.). Adhesive tape, Velcro, etc. are not permitted for this purpose. f) The vehicle must have a roof covering the Driver’s compartment. g) A windscreen with effective wiper(s) is mandatory. Please refer to Article 52:. h) Luggage space must be available for a rectangular solid box with dimensions of 500 x 400 x 200 mm (L x H x W). This space must be easily accessible from the outside and must include a floor and sidewalls to hold the luggage in place when the vehicle is moving. This box must be supplied by the competitor and must be placed in this space during the competition. For drivers requiring ballast this box must contain the ballast in a safe and secure manner. i) Vehicle bodies must not include any external appendages that might be dangerous to other Team members; e.g. sharp points must have a radius of 5 cm or greater, alternatively they should be made of foam or similar deformable material. j) A towing hook or ring is mandatory on the front of the vehicle, under the body and easily accessible,

so that it can be towed with a cable by another vehicle. This hook or ring must resist a traction force

of 2,000 N (~200 kg).”

Article 47: turning radius and steering, paragraphs a through e:

“a) Vehicle steering must be achieved by one system operated with both hands using a turning mo-tion. It must be precise, with no excessive play. b) Steering must be achieved using a steering wheel or sections of a wheel. c) Steering bars, tillers, joysticks, indirect or electric systems are not permitted. d) The turning radius must be less than 6 m. e) A vehicle handling course may be set up in order to verify the following when the vehicle is in mo-

tion: driver skills, turning radius and steering precision. In particular, Inspectors will verify that steer-

ing is precise, with no excessive play.”

Article 48: wheels, paragraphs a and b:

“a) The rims must be between 13 to 17 inches in diameter. b) The wheels located inside the vehicle body must be made inaccessible to the Driver by a bulkhead.

Any handling or manipulation of the wheels is forbidden from the moment the vehicle arrives at the

starting line until it crosses the finish line.”


14.12.12 15

Article 49: tyres:

“The choice of tyres is free as long as they are fitted on the type and size of rims recommended by their manufacturers and have a minimum tread of 1.6 mm. The tyre / rim assembly must have a min-imum width of 80 mm, measured from sidewall to sidewall. The width is measured with the tyre fitted on its rim at its rated pressure. Caution: the manufacturer’s size indications should not be taken as measure, as the width of the rim

directly impacts the width of the rim/tyre assembly.”

Article 50: lighting, paragraphs a through g:

“The vehicle must have a functional external lighting system, including: a) Two front headlights b) Two front turn indicators c) Two rear turn indicators d) Two red brake lights in the rear e) Two red rear lights (may be combined with the brake lights) f) The centre of each headlight unit must be located at an equal distance and at least 30 cm from the longitudinal axis of the vehicle. g) The mandatory red indicator light for the self starter operation must be separate from any of the

above ( Article 64:c))”

Article 51: braking, paragraphs a through e:

“a) The vehicle must be equipped with a four-disc hydraulic brake system, with a brake pedal, which has a minimum surface area of 25 cm². b) The brakes must operate independently on the front and rear axles or in an X pattern (i.e. right front wheel with left rear wheel, and left front wheel with right rear wheel). c) A single master cylinder may be used, provided that it has a dual circuit (two pistons and dual tank). d) The effectiveness of the braking system will be tested during vehicle inspection for both Drivers. The vehicle must remain immobile when it is placed on a 20 percent incline with the main brake in place. Moreover, a dynamic inspection may be performed on the vehicle-handling course. e) Wet weather capability is mandatory (see Article 52:)”

Article 52: wet weather running, paragraphs a through i:

“a) During weather conditions of light rain/drizzle, the UrbanConcept vehicles (only) may be required to drive on the track during competition with approval from the Race Director. Therefore, all UrbanConcept vehicles must be adequate for running under such conditions. b) The vehicle must be equipped with an effective electric windscreen wiper(s). c) The operation of the wiper assembly must be activated by an independent switch easily accessible to the driver. d) The wiper operation must provide the driver a clear view. This means the wiper unit must function as designed, and remain on the vehicle during competition. e) The vehicle must be adequately ventilated to prevent driver’s compartment from fogging. f) The vehicle’s electrical system must be suitable for wet weather conditions (e.g. will not malfunc-tion during wet conditions). g) Tyres must have a minimum tread of 1.6 mm (refer to Article 49:). h) The vehicle’s brake effectiveness may be re-inspected before and/or after any run.


14.12.12 16

i) The effectiveness of the vehicle to run in wet conditions will be evaluated during the initial inspec-

tion phase.”

Article 57: vehicle electrical systems, paragraphs a through m:

“a) For safety reasons, the maximum voltage on board of any vehicle at any point must not exceed 48 Volts nominal and 60 Volts max (this includes on-board batteries, external batteries, super capacitors, fuel cell stack, solar cells, etc). Battery definition: A ‘battery’ is defined as a source of electrical energy, which has exactly two con-nectors and comes as a single unit. This single unit may contain more than one sub-unit. b) If Lithium-Ion based batteries are used, Battery Management Systems (BMS) tailored to this chem-istry must be installed to control and protect the battery against risk of fire. The BMS must provide cell balancing and overvoltage protection during off-track charging. For e-mobility vehicles, the addi-tional requirement of overdischarge, over-current and over-temperature must be provided as part of the on-vehicle system. The BMS must AUTOMATICALLY isolate the battery, without operator interven-tion, if a limit or out of range condition is reached on any of the above parameters. For Li-Ion based accessory batteries, the BMS cell balancing and overvoltage protection may be contained as part of the off-board charger. c) All batteries and super capacitors must be short circuit protected. Protection may be in the form of a fuse, fusable link, or a current interrupting device (circuit breaker). Automatic reclosing current in-terrupting devices are not allowed. Short circuit protection devices must be located on the positive conductor and as close as possible to the battery or super capacitor itself. The rating of the short cir-cuit protection device must be such that the battery or super capacitor will be able to supply enough short circuit current at all times to open the device. d) All vehicle electrical circuits must be protected against electrical overload. Overload protection may be in the form of fixed current limits within electric controllers or by the insertion of individual circuit fuses. e) The accessory battery (refer Article 57:h)) must maintain a negative ground. f) For safety reasons, the propulsion battery or super capacitors, both positive and negative circuits must be electrically isolated from the vehicle frame and the accessory battery circuit. This only applies to Hybrid and e-mobility vehicles which have a propulsion battery. g) Only one propulsion battery (for e-mobility vehicles only) and one accessory battery per vehicle are allowed. h) The accessory battery must operate all safety devices (e.g. horn, hydrogen sensor) for the duration of the competition and may also operate, only for internal combustion engine, the starter motor, the ignition, the instrumentation and electronic management systems. All other additional sources of electricity are forbidden. i) The accessory battery is not allowed to power compressors, blowers, engine cooling systems, mo-tors, etc. It may however be used to power a ventilation / cooling fan for the driver. j) The Organisers reserve the right to request Teams to install one joulemeter, intended to measure the quantity of energy provided by the accessory battery. If this amount of energy exceeds the power typically required to operate the starter motor, horn and safety devices the competitor will be dis-qualified. k) Both propulsion and accessory batteries must be installed outside of the driver’s compartment be-hind a bulk head. (See Article 27:) l) The following devices may be powered by batteries other than the propulsion or accessory battery provided they use built-in batteries: radio communication system, GPS system, data loggers excluding engine management units, driver ventilators.


14.12.12 17

m) All electrical / electronic enclosures built and populated by the teams must be made of transpar-

ent material or at least have a transparent cover to allow the technical inspectors to view the con-

tents.”

Article 58: technical documentation, paragraphs a through c:

“a) Competitors must provide the Organisers with a precise technical description of the vehicle’s fuel system and electrical circuitry. This documentation serves only to verify that the teams have an un-derstanding of the Rules. Admission to the competition in no way constitutes a pre-approval for the Technical Inspection phase. Final technical approval is only granted at the event. b) Technical Documentation – prior to event. i) Competitors must provide, through the online submittal process, documentation on the fuel and vehicle electrical system. iii) For all vehicles, the electrical systems documentation may be in form of one or more block dia-grams / electrical circuit diagram containing the following: 1. Point to point vehicle wiring diagram showing the location of all major relevant electrical compo-nents of the system, such as batteries, super capacitors, fuses/circuit protectors, lights, alternators, horn, starter motor (for e-mobility vehicles this should also include drive train components such as fuel cells, motors, controllers, solar cells, MPPTs, joulemeters), etc. 2. Component voltage, current, and power ratings of major components. 3. Locations and ratings of all circuit protection devices. 4. Illustration of how the emergency stop system works, and presence of both external and internal emergency switches in the electrical circuit. A separate sheet may be used to illustrate this if neces-sary. 5. A description of any battery(s) or ultra (super) capacitors being used in the system, including type, rated voltage, max charge voltage and capacity in amp-hours or capacitance. 6. Starter motor, starter light connections (for vehicles with starter motor). c) Technical Documentation – at event (to be reviewed during Technical Inspection) i) Competitors must have available for inspection with the vehicle, a printed copy of the latest version of the documents submitted above ( Article 58:b)) and the additional documentation as defined be-low. ii) For all vehicles, if a Lithium-Ion battery is used as accessory battery, printed / written documenta-tion on the BMS operation must be provided. (Note, the requirement for BMS system operation data is independent of whether the BMS is integrated into a purchased battery, part of the charger or spe-cial built.) The BMS data MUST include: 1. Cell over-voltage protection limits. 2. Operation of cell balancing (how and when). 3. Battery operation when over-voltage, limits are reached. (that is, what will the BMS/Battery do when these limits are reached) iii) For all E-mobility vehicles printed/written documentation on the BMS operation must be provided. (Note, the requirement for BMS system operation data is independent of whether the BMS is inte-grated into a purchased battery or special built.) The BMS data MUST include: 1. Cell over-voltage and under-voltage protection limits. 2. Battery over-current limit. 3. Operation of cell balancing (how and when). 4. Battery over-temperature limit. 5. How the BMS will protect the battery when an over-voltage, under-voltage, over-current or over-temperature condition is reached. (That is, how will the BMS isolate the battery when these limits are reached?)


14.12.12 18

iv) For E-mobility vehicles the additional printed technical documentation must include: 1. Any additional information not submitted prior to the event on the battery type, energy capacity and nominal voltage ratings (both propulsion and accessory if used). 2. Any additional information not submitted prior to the event on the motor(s) and motor controller(s) power and voltage ratings. 3. PV data sheet power and voltage ratings (Pmpp, Isc, Voc, Vmpp) (if used). 4. PV controller (MPPT), power and voltage ratings (if used).”

Article 67: battery electric vehicles, paragraphs a through q:

“a) This category is open to both Prototype and UrbanConcept entries. b) The drive train in the ‘Battery Electric’ category is restricted to a maximum of one electric storage device, and up to two electric motors, with associated control units. c) Only Lithium-Ion batteries are permitted as electric storage devices. d) The vehicle must be equipped with a Battery Management System (BMS) to control and protect the battery against risk of fire as defined in Article 57:. Please do note that as of 2013 any BMS for propulsion Batteries must provide an AUTOMATIC isola-tion of this battery in the event of any measured parameters getting out of their designed range. e) The Lithium-Ion battery and any accessory circuits are subject to the maximum voltage defined in Article 57:a) f) An accessory battery as defined in Article 57:h) is permitted. If one is used, all accessory circuits must not be connected to any of the electric circuit(s) involving any power train components and must only be used to power safety related components and only those systems mentioned specifically in Article 57:. g) Solar cells MAY be integrated into the vehicle electrical circuit. If solar cells are included they must meet the following requirements: 1. The solar cells must be fully integrated into the bodywork of the vehicle. They must NOT form an independent structure or be part of any other structures protruding from the vehicle. 2. The maximum voltage present at any point in any circuit, whether before or after the maximum power production (MPP) controller, must not be greater than that defined in Article 57:a). 4. For an UrbanConcept vehicle, the total combined surface of the solar cells shall be less than 0.65 m2 (e.g. 40 cells of 5x5 inches or 27 cells of 6x6 inches). 5. The output of the solar cells will be measured through a joulemeter. The joulemeter will be con-nected in the vehicle electrical circuit before the motor joulemeter and after the solar cell MPP con-troller, if equipped. 6. The calculation of the race result (expressed in km/kWh) will be based on the Net propulsion energy supplied by the battery only, excluding the energy contributed by the solar cells, i.e. Net propulsion energy = motor propulsion energy – solar energy. The motor propulsion energy includes both, the energy consumed by the motor and the motor controller. h) The competitors will be required to present electrical schematics at the competition technical in-spection. (See Article 58:) i) All Batteries must be placed outside the driver’s compartment behind the bulkhead and securely mounted. Bunge cords or other elastic material are not permitted for securing the battery. (see Article 27:) j) All vehicles must be equipped with one joulemeter located between the battery and the motor con-troller(s), and, if equipped with solar cells, a second joulemeter for the solar output as described in Article 67: g) 5 above, to measure the vehicle propulsion energy consumption. k) The Organisers will provide the joulemeter(s) for the duration of the event. A security deposit may be required for the joulemeter. l) The joulemeter(s) must be positioned so that its display can be easily read from outside the vehicle.


14.12.12 19

m) The joulemeter(s) must be inaccessible to the Driver in his or her normal driving position. n) All electrical circuits must be protected as defined in Article 57:d). o) On the starting line, Fuel Marshals will reset the joulemeter(s) to zero, and then the vehicles will have access to the track to start their attempt under the same distance and time conditions as speci-fied for their respective vehicle class. p) At the finish line, Fuel Marshals will read the joulemeter(s) display. q) All ‘Battery Electric’ vehicles which complete a successful run will be classified in descending order

of fuel economy, expressed in km/kWh.”

3. Enabling technologies

CAD software (SolidWorks, Inventor, 3DS Max)

Ansys 14

MS Office (Word, Excel, PowerPoint, Project)

XMind

MatLab 2012

Hub motors

Composite materials (carbon fibre, flax fibre, combinations, reinforcements, seat)

The internet (Google Search, Google Calendar, Google Drive, Google Mail, Dropbox, Face-

book, Twitter, YouTube)

Prototyping

Mountain bike braking systems

Rack and pinion


14.12.12 20

4. Own Work: Group 3

4.1. Brake System, by Devon Barkway

Introduction

One of the tasks designated to me was developing a solution within the front wheels braking and

steering system. Choosing the type of braking system became the first priority, with all subsequent

components and systems within this section of the project being designed around it.

Requirements

In short, according to the Shell Eco Marathon rules1, the braking system needed to be a four disc,

hydraulic system with independent operation of a master cylinder split between two line pairs.

Needless to say, the system should also, for our requirements, be as light as possible in order not to

add too much weight and thus increase overall efficiency.

Selection

It became quickly apparent that the best possible solution for the braking purposes of our vehicle

would be to use mountain bike breaking system components. They are very light, powerful, highly

standardised and cheap, having a lot of development history; to develop a brand new hydraulic brak-

ing system to meet our requirements would have been far be-

yond the scope of this project. Another advantage would be

that the braking mechanisms, i.e., the hand levers which include

the master cylinders for the hydraulic fluid, would also be part

of the system and that they would be able to be easily incorpo-

rated in to a foot operated pedal. The process of the pedal crea-

tion is further described in chapter 4.3.

Thus, it was decided to use, in the opinion of at least one of the

team members who is an avid mountain biker, the best compa-

ny for mountain iking raking and wheel components, ‘Hope’2.

Components - Callipers

It was decided that the braking callipers should be sourced first.

After researching the many options provided by Hope3, the M4

model was selected (Image 1), due to its powerful stopping per-

formance and double piston actuation.

From this point, a CAD model needed to be sourced in order to proceed with the design of the brak-

ing system. Unfortunately, a model was not available from the suppliers directly, but one was ob-

tained nonetheless from GrabCAD4, which is claimed to originally be from the suppliers. After a few

1 Competition Rules: Article 51

2 http://www.hopetech.com/

2 http://www.hopetech.com/

3 http://www.hopetech.com/page.aspx?itemID=SPG28

4 http://grabcad.com/library/hope-mono-m4-is-mount-caliper

Image 1: Hope M4 brake calliper. (http://www.chainreactioncycles.com/Models.aspx?ModelID=26213)


14.12.12 21

dimension checks, it was deemed suitable for the purpos-

es of using it in the CAD assembly (see Image 2).

Components – Discs

Fortunately, mountain bike brake discs are highly stand-

ardised, with various set diameters and the same screw

mounting arrangement regardless of the make and model

of disc chosen. A brake disc CAD model was obtained

from, once again, GrabCAD5 (see Image 3). This particular

disc was initially used more as a reference than a perma-

nent solution, as later on in the project a wheel was

sourced which did not have a standard mountain bike

brake mounting. More than likely, we would need to de-

sign and manufacture our own brake discs to mountain

bike specifications, apart from the mountings which would

be the same as the

wheel’s mountings.

Once the calliper and the disc were selected and CAD models ob-

tained, the design work could then continue. The next step was to

design the steering bracket, on to which the brake calliper will be

mounted. The design process for both the calliper-disc assembly

and the bracket was intertwined, with constant need of design,

trial and re-design, thus making it fairly difficult to report on the

process. It would be more suitable to mention at this point that as

work on the system progressed, it was found that a standard calli-

per adapter used in mountain biking for mounting the calliper in

the correct position in relation to the brake disc was not suitable.

Thus, a bespoke calliper mount needed to be designed.

Components – Calliper Mount

Using previously existing standardised calliper mounts as inspiration, a new, bespoke mount was

designed for the purposes of this vehicles braking system. The function of the calliper mount is to use

the standard post mount set-up of the calliper and convert it to an IS (international Standard) mount

of the steering bracket that the calliper mount would be attached to (IS mount dimensions consist of

two 5mm holes with 51mm distance from centre to centre, as shown in Image 4).

5 http://grabcad.com/library/bicycle-standard-230mm-disk-brake-rotor

Image 3: Brake disc render.

Image 4: IS (International Standard) hole dimensions.

Image 2: Hope M4 post mount calliper render


14.12.12 22

After some preliminary sketching of the idea (see Image 5), the faces of the post mounting on the

brake calliper and the faces of the IS mounting on the bracket were used as references to design a

mount in Solidworks. The final design, which was pleasingly close to the original design idea, is shown

in Image 6 and the technical drawing can be seen in Appendix 1.1. The material used is the same

material that is used for the steering bracket that is Aluminium 6061-T6. It has fair machinability and

so difficulties in producing the mounts are unlikely (See chapter 5.2. for more detailed material de-

scription and properties).

Standard bolts and washers that are widely used and available in mountain biking were used as fas-

teners for the fastenings of the calliper to the mount, and the mount to the steering bracket.

4.2. Steering Bracket, by Devon Barkway

Introduction

A bracket needed to be designed that would have the specific purpose of being the point of connec-

tion between the wheels and the chassis, as well as incorporating mounts for the brake callipers and

steering rods.

Once again, the key issue for the racket (as is with the vehicle as a whole) is weight, as the vehicle’s

total weight needs to be as light as possible in order to increase its efficiency. Traditionally, these

particular wheel assemblies have the potential to add a lot of weight with heavy housings for calli-

pers, thick metal plates for mounting and so on. The goal was to use components with sufficient abil-

ity that added as little weight as possible.

Image 6: Calliper mount from post mount to IS. Image 5: Preliminary rough design sketch.


14.12.12 23

Foundation Ideas

In the initial phase of idea generation for group 3, the systems were broken down to highlight their

main requirements and functions. These were designated as being:

Brake discs

Brake callipers

Wheels

Steering rods

Brackets with mountings

The majority of the other components for the systems mentioned were to be sourced from estab-

lished manufacturers and their models used in our assemblies. The design of this bracket would be

mainly according to our braking components.

Once it was decided that the best solution for braking would be to incorporate a high-end mountain

bike braking system, work could commence on the steering bracket design, which is a bespoke part

of my own, original design.

A sketch similar to some initial rough ideas for the design of the bracket is shown in Image 7. Once

the basic idea was in place, I used the brake disc CAD model as the main design reference and began

to design the bracket according to my original sketches. It quickly became apparent that this idea

was not going to work, as it wouldn’t e the est solution for mounting the rake callipers due to the

severe angle of the side of the bracket (see Image 8). To create a workable calliper mount (detailed in

Chapter 5.1.), the angle of the side of the bracket that contained the IS mounting holes had to be less

steep.

Image 8: Design sketch of original brack-et concept.

Image 7: First concept model of steering bracket.


14.12.12 24

A re-think had to be done and a new idea was generated; the

base shape of the bracket would have less angular sloped sides.

It’s left to right symmetry was discarded, as it would have re-

sulted in superfluous material and extra weight. A sketch of the

new idea is shown in Image 9.

The reiterating of this part had an unforeseen yet welcome re-

sult; the solution to another issue in the system was refined and

improved. Initially, there was going to be a separate steering

arm/knuckle, to which the steering rod would connect. This

would have had to be welded on to the bracket. However, by

changing the shape of the bracket from the original idea, it oc-

curred to me that it would be possible to incorporate the steer-

ing rod mounting in to the bracket itself, and gave me a new

focus of designing the bracket so that it required as little machining and welding as possible; this is

obviously a favourable development.

From there, a CAD model was created. Fortunately, the opportunity presented itself to perform some

FEM analysis on the newly created part, the details of which are as follows

Basic FEM Analysis

In order to further refine the design of the steering bracket, a FEM analysis was used as a means of

possibly reducing the amount of material used and maybe even the geometric design as well. It is an

important component of the vehicle and thus it is important to simulate the forces it would incur and

how it responds to said forces. A FEM analysis would also accomplish this. Reported below is a sum-

marised version of the findings. For the full report, please refer to Appendix 1.2.

All FEM analyses were accomplished using

Ansys 14.0. The model used in the simulation

is shown in Image 10. This version of the

steering bracket is a simplified version, the

initial model used in the development of the

steering system. It was initially thought that a

new type of mounting for the connector rods

could be developed within the scope of this

project. However, as the project progressed

and time constraints became a limitation, it

was decided to use a slightly altered model

(as in in ‘Final Concept’) to the model used in

the FEM analysis. It is believed, however, that

the analysis was still valuable and that there

would not be too big a difference between

the initial and final steering brackets.

Image 9: Concept sketch of a new, re-vised bracket.

Image 10: Initial, simplified steering bracket model used in FEM analysis.


14.12.12 25

The material defined for the model is Aluminium 6061-T6. As mentioned above, it is a widely availa-

ble and commonly used material within bicycling with the following applicable material properties6:

Modulus of Elasticity: 68,9 GPa

Poisson’s Ratio: 0,33

Yield Strength (tensile): 276 MPa

Ultimate Strength (tensile): 310 MPa

Density: 2,7 g/cc

In order to gain some initial understanding of the forces acting on the bracket, some simple hand

calculations were done in order to obtain the reacting forces at certain points. With reference to the

free body diagrams in Image 11, the following equations were made and solved:

⁄

⁄

Image 11: Free body diagrams, predicted acting forces and subsequent reaction forces applicable to the steering bracket.

From these two simple equations, we can see the reaction forces present in the bracket along two

different planes. There are two support rod mounts whose faces are closer to the steering rod force

6 http://asm.matweb.com/search/SpecificMaterial.asp?bassnum=MA6061t6


14.12.12 26

than the hole for the shaft, thus it is assumed that the reaction force will occur at these faces and be

split in to two as the geometries are symmetric.

The bracket will be subjected to changing loads due to nature

of its function, namely to support a portion of the load of the

vehicle on the axel of a wheel. The maximum expected loads

that the bracket will be subjected to of 200N along the XY

plane and 1000N along the ZY plane have been used in the

analysis as static forces (see Image 12). The initial plate thick-

ness of 8mm was used in the first simulation.

Once the test was run, the results for the stress analysis and

the deformation analysis were interpreted. The maximum

equivalent von Mises’ stress was roughly 17 N/mm2 resulting

in a maximum deformation of 0,045mm. There is no question

that the bracket can withstand the expected applied loads

used in this simulation; the resulting stress present is a little

over 6% of the material’s yield strength and the deformation is

negligible. On the basis of these result, a second analysis was

performed on a bracket with a reduced thickness of 4mm.

The second analysis was run with the same boundary condi-

tions and applied forces as in the first analysis. The results

revealed that the equivalent von Mises’ stress was roughly 77

N/mm2 and a resulting maximum deformation of 0,12mm. The

results for both analyses are displayed graphically in Image 13.

These values are more optimal for the purpose of both manufacturing the part when considering

material price, manufacturing and, most importantly, the weight of the part in total. The resulting

stress relating to the material’s yield stress produces a factor of safety for the racket of approxi-

mately 3,5. The maximum deformation in my opinion is also within requirements with regards to the

accuracy of the steering function of the bracket.

It was thus decided to reduce the thickness of the steering bracket to 4mm. Further re-modelling of

the bracket in the form of cutting material away in areas of very low stress was considered. However,

due to the fact the model is a simplified version and the desire to keep the bracket versatile in terms

of assembly (i.e. the ability to drill holes in various places for the mounting of other parts), it was

deemed unnecessary. Also, the total weight of the bracket had already been reduced by half due to

the reduction in thickness; yet another reason to exclude further reductions.

Image 12: Applied forces and boundary con-ditions; plate thickness = 8mm.


14.12.12 27

Image 13: FEM results for 8mm and 4mm plate thicknesses using ‘Ansys 14.0’.


14.12.12 28

Final Solution

In the final solution, I managed to achieve a design of the steering bracket that would incorporate

the brake calliper mounts (International Standard [I.S.] mounting), a steering rod mount, support rod

mounts and the axle. I am quite satisfied with the final result of this particular system and the inno-

vation exercised in reaching a good solution. For the technical drawing of the bracket, as well as an

assembly drawing for the bracket-mount-calliper assembly, please see Appendix 1.1.


14.12.12 29

4.3. Braking Pedal, by Pavel Sokolov

Introduction

Main task, assigned to me was the development of breaking pedal, which could fit within our design

philosophy and met the requirements of ShellEco Marathon 2103 rules.

Requirements

According to ShellEco Marathon 2103 rules1, the vehicle must be equipped with a four-disc hydraulic

brake system, with a brake pedal, which has a minimum surface area of 25 cm².

General design and idea description

As was descri ed a ove, in chapter 5.1, for our raking system we shall use “Hope”2 mountain bike

hydraulic brakes, specifically M43 model. For pedal design 4 levers with master cylinder were used,

one lever per each wheel. This concept fits the ShellEco Marathon 2103 rules1 for brakes operation:

b) The brakes must operate independently on the front and rear axles or in an X pattern (i.e. right

front wheel with left rear wheel, and left front wheel with right rear wheel).

c) A single master cylinder may be used, provided that it has a dual circuit (two pistons and dual

tank).

We also have concluded additional requirements for our pedal:

As our monocoque will be made from composite material it must be easy to attach the pedal

to body.

The overall design of the pedal must be kept as simple as possible.

It must be easy for driver to interact with the pedal.

Component description – Braking lever with master cylinder

As we made our pedal with already existed part, we needed its precise dimensions. Unfortunately,

the model of the part wasn’t availa le from manufacturer, so we look for it on another we sites. We

managed to find it on GrabCAD4 site5. This detail has all necessary dimensions.

Image 14: Braking lever with master cylinder


14.12.12 30

Component description – Mounting

In our design four consecutive braking levers aligned vertically. It was necessary to design simple

construction, which would keep it aligned properly. After reviewing some possible solutions, we have

decided that best option is to mount braking levers onto four aluminium 6061-T66 tubes with match-

ing diameter, welded to the additional plate of the same material at the bottom to ensure stability of

the construction.

Image 15: Mounting

Component description – Mounting plate

Further question to solve was “How to attach the pedal to the ody?” As stated a ove our ody

would be made from composite materials, which highly limits possibilities to solve this problem. Only

two viable options existed – either glue the construction or bolt it to the body. We decided to stick

with the later, as more reliable choice. Thus the special plate was designed with dimensions

160x50x8 mm made from aluminium 6061-T6. To this plate above highlighted construction would be

welded and plate itself would be attached to body using 4 M8 bolts7 positioned in the corners of the

plate.


14.12.12 31

Image 16: Mounting plate

Component description – Rail

For proper pedal operations the simultaneous work of all 4 braking levers must be ensured. To solve

this problem two rails were designed, which would be situated at top and bottom of breaking levers.

Rails connected with each other with the help of three M8 bolts. Material for the rails is the alumini-

um 6061-T6. This simple construction ensures the proper functionality of the pedal and keeps weight

addition at minimum.

Image 17: Rail

Component – Pedal arm

The final part of the breaking pedal assembly is the pedal arm. This part consists of two sub-parts –

the plate with dimensions 70x40x20 mm, which serves as pedal itself and fits within the rules and

small arm with dimensions 10x17.3x5.14 mm, which is used to connect the arm to rails. This non

standard dimensions chose on the basis that arm must fit precisely into the central gap with zero


14.12.12 32

clearance to ensure suitable rigidity of the construction. The whole pedal arm is the single part, made

from aluminium 6061-T6.

Image 18: Pedal arm

Conclusion

The whole pedal assembly consists of simple parts, easy to manufacture, made from aluminium

6061-T6. This material has several advantages, which is crucial to our design – its availability, relative-

ly low weight, good machinability and weldability and moderate price. As the breaking levers with

master cylinders is the only details needed to be bought, the overall design was based on minimum

weight addition and complexity, which ensures that the whole pedal can be made fast and without

much skill required. Please see Appendix 1.1. for all technical drawings and assemblies.

References 1Competition Rules: Article 51 2http://www.hopetech.com/ 3http://www.hopetech.com/page.aspx?itemID=SPG28 4http://grabcad.com 5http://grabcad.com/library/hope-hydraulic-front-master-cylinder 6http://asm.matweb.com/search/SpecificMaterial.asp?bassnum=MA6061t6 7http://www.konarik.cz/en/products/connection-accessories-screws-wood-screws/hexagon-head-

screws-din-931/


14.12.12 33

4.4. Exterior design, by Rostovtcev Viacheslav

Introduction

The final exterior design is a product of group discussions and designer work. Idea behind the con-

cept is an urban concept car working on electrical power and the main look of car would represent

our sense of design and innovation.

Design concepts

Actual design procedure started with some simple sketches which would set the direction of design

and represent our individual sense of urban concept car.

Image 19: Early concept sketches

First sketches were showed to the rest of the group and the direction of design was set. In order to

give our car our own look every member of a group presented their own ideas on how the car should

look like. Then I have made some more detailed sketches based on inspirations and expectations of

my team members and presented two different options.

We have chosen to take something from first option and something from other option and combine

them. So I made the final sketch.

Image 20: Refined concept sketches


14.12.12 34

Image 21: Combination of Image 19 designs.

But then we agreed that aerodynamics properties of body

shape were not so good due to the rear part of a car.

Hatchback style trunk creates a lot of turbulence at the

back of the car and increases drag force coefficient. I tried

to stick to water drop shape but it is not as simple as it

sounds but anyway final sketch was done and approved by

the rest of the team.

Image 22: Final concept sketch with altered rear.

Based on the sketch a model in 3ds max was created. Some renders were done as well in order to

represent main look of a car which we are going to stick to in our design job. Model is made with two

seats in cockpit in order to make it more close to road cars. This car has a rear wheel electric drive

and trunk under the hood. Concept idea was to make doors out of transparent material like fiber-

glass and polyester but this is just a concept idea.

Image 23: 3DS Max model renders.


14.12.12 35

The whole idea and concept development took a lot of effort and full concept design evolution can

be seen in Appendix 1.3., concept design evolution.

4.5. Steering arm support, by Rostovtcev Viacheslav

Introduction

Another task was to design a front arm supporting the wheel and a bracket which would be attached

to the chassis. There are many different options available which would include many moving parts

and many bearings. However we decided to create car without any suspension as it would reduce

weight and would comply with the rules of the race in category for urban concept vehicle.

Concept design

At first one steering arm was created and it was conducted to FEM analysis to withstand theoretical

weight of vehicle. For FEM analysis I used theoretical weight of vehicle divided by four. This force is

one which would be supported by each wheel and each bracket. So I have taken weight of 300kg in

order to make calculations with some safety capacity. Bracket material is Aluminum 6061-T6 which is

widely used for Mountain bikes components. FEM analysis showed that one arm is not enough to

withstand possible loads as it would exceed materials yield strength of 275 N/mm2.

Source: Aerospace specification metals Inc., Materials online database [Online]

Available at: http://asm.matweb.com/search/SpecificMaterial.asp?bassnum=MA6061t6 [Accessed 4

December 2012].In fact it showed that two same arms would perfectly support the force.

Image 24: FEM analysis results using Solidworks.


14.12.12 36

My decision was to make it in two parts from each side but in that way that actually I would design

one universal part. So it ended up like seen on the sketches below.

Simplicity and universality of the construction are advantages as only four equal parts should be

manufactured. However After I selected the bearing I had to decrease the thickness of bracket from

10mm to 7,5 mm to fit the bearing. The bearing I have chosen is one which have a slight angle of

horizontal movement. Bearing name Spherical plain bearing GE-8 EC from French manufacturer FLI-

Industrie.

Source: FLI-Industrie Inc., Product catalogues [Online]

Available at: http://www.fli-industrie.fr/fli_fr_catalogues.html [Accessed 14 November 2012].

Thickness of bearing is 8mm and further information could be found in

Appendix 2.1. To fix the bearing at the position and avoid slipping I de-

signed system which is very similar to what is used in bicycle to attach

levers to handlebar. The idea of a system very simple as there is a hole

where the bearing must fit in and this hole have an all-through cut of

1mm till the arm end. At the end there is a hole for M4 bolt which is

screwed inside and tightens the main bearing hole at the same time de-

creasing its diameter and fixing the bearing at the position needed. System

is seen on the picture with bike brake lever. There are three M10 bolts in

assembly which would be fit into the holes on chassis and tightened with

nuts from other side and one M4 bolts which fixes the bearing in position.

Image 25: CAD model and assembly using two arms.

Image 26: Bearing drawing.


14.12.12 37

Image 27: Steering support arm with associated fastenings and brake lever.

After changing the thickness of support arm I applied a FEM analysis to the end part with the re-

quired force of 306 N which is relevant to overall car weight of 250 kg. Results were acceptable which

meant that overall part design with thickness decrease is also good. The result is shown that overall

stress does not exceed the yield strength of material (Image 28) and maximum possible displacement

is 6 mm (Image 29).

Image 28: FEM analysis for arm with thickness of 7.5mm.


14.12.12 38

Image 29: Displacement fro arm with thickness of 7.5 mm.

For technical drawings of a steering arm and assembly drawing please refer to Appendix 1.1.


14.12.12 39

4.6. Steering system, by José Antonio Rodríguez Rodríguez

Introduction

The steering system for this vehicle was designed by José Antonio Rodríguez Rodríguez. The steering

system is responsible for moving the wheels of the car when the driver wishes to do it by turning the

steering wheel. This design consists in four main parts:

- Tie rod and knuckle arms.

- Rack and pinion.

- Steering column.

- Steering wheel.

It also has two structures that support the steering system with the chassis. The first structure

support the rack and it do of guide it to get the required movement by the rack. The second structure

support the steering column connect by the steering wheel.

Source: ARIAS-PAZ Manual de Automóviles 55º Edición

Tie rod and knuckle arms

We are going to design the tie rod and the knuckle arms, for this we based in Shell Eco-Marathon

rules where the turning radius must be less than 6 meters. We know that the front wheels turn with

angle differents because the angle forming by the turning center with the front wheels are

differentes while the angle forming with the rear wheels is the same.

Image 30: Turning circle angle.


14.12.12 40

The turning radius is the distance smaller from the turning center till each one of the four wheels. If

we turning for the left like in the picture, this distance is from O till the rear left wheel. Therefore, it

calculated the turning center and we knew the wheelbase, F, and the track, E, we can calculate the

angles C and D.

Then, we have the maximum angles that our vehicule it can turning in a curve. A factor important for

dimensioning the knuckle arms is the drift angle. If the knuckle arms cut ahead of the center the rear

axis, we are in a case of oversteering, so, the rear wheels have a drift angle greater than the front

wheels, then the vehicle take the curves more closed. However, if the knuckle arms cut behind of the

center the rear axis, we are in a case of understeering, so, the front wheels have a drift angle greater

than the rear wheels, then the vehicle take the curves more open.

For my design, I have choosen a behavior of oversteering because I think that our vehicle will be

more competitve. Nevertheless, I have choosen a tie rods which can be regulated manually with a

threading system.

Image 31: CAD representation of turning circle angle.

Image 32: Steering arm.


14.12.12 41

One time it chosen of the angle it

formed by the front axis with the

knuckle arm, we can to design the

correct mechanism that when it turning

the wheels it turning their

corresponding angles. With this design,

we achieve that the angle of the

external wheel the rotation it

approaching to the required angle.

Finally, I have selected the tie rods and

knuckle arms of carbon steel because it

have resistance to various stresses (both static and dynamic forces).


Rack and pinion

The system rack and pinion is

one of the system more used in

the industry of the auto,

thereby and for simplicity we

have chosen it.

For selecting the rack and

pinion, first we have to know

how much distance it walk the

mechanism.

Therefore, we have drawn it and we have calculated the distance of 73.376 mm

For selecting the ideal pinion we have to know the maximum turning angle of the steering wheel and

we have considered 180 degrees is a optimum angle for our driver.

Calculate the pinion:

- Selecting a module of 2.

- Selecting a pressure angle of 20 degrees.

- We know that it have that walk half of the teeth of the pinion.

- We know that the rack that walk 73.376 mm.

Therefore:

so one time calculated the pitch, we can calculated the number of teeth.

have to have the pinion.

Image 33: Steering arms.

Image 34: CAD dimensioning.


14.12.12 42

With this data, we can choose a pinion with its rack.

Finally we select a rack with 32 teeth in total and it walk 11.68 teeth in both sides.


Steering column

The steering column is shaft of transmission from the steering wheel till the system of gear. This

design is composed by a Hooke joint to bend the shaft and to have the pinion parallel to the

horizontal.

The Hooke joint as well it can to work like a system for security because in case of collision the driver

no have the risk of penetrate himself the steering column in the thorax.


Image 35: Rack and pinion system.

Image 36: Steering column universal joint and shaft.


14.12.12 43

Steering wheel

The steering wheel is designed for to be ergo-

nomic for the driver with a diameter of 330

mm made for aluminum and rubber.

As the driver is of thin corpulence and he has

short shoulders, we have decided to choose a

steering wheel of this dimensions and we

believe that it is the more optimum for our

conditions.

Source: ARIAS-PAZ Manual de Automóviles

55º Edición

Frame of rack

The frame rack is very important because it do of guide for the rack. On both of sides of the ends it

has an element that it works for that when the driver turning the steering wheel 180 degrees, the

rack stop with this device. It is attachment with the chassis.

In the picture below, you can to see how it is design this frame to cut it for a plane.

Image 37: Steering wheel model.

Image 38: Rack frame.


14.12.12 44

Frame of steering wheel

The frame for the steering wheel is need it because the Hooke

joint it cannot sustained only, therefore for our design is the big

important. It composes by a bearing that it works for that the

steering wheel it can turning correctly. Also it is attached to the

chassis.

Conclusion

In my opinion I think that the steering system it is good designed

for this competition, I have worked hard for to think a system

simple and efficient. Finally I achieved to design a mechanism

that it could turn the necessary angles to the requirements of

the rules. For all technical drawings of parts and assemblies for

the steering system, please see Appendix 1.1.

Image 39: Steering wheel frame.


14.12.12 45

4.7. Rear attachment & Rear Braking, by Juan Carlos Hurtado Sierra

Introduction

The rear attachment for the vehicle was designed by Juan Carlos Hurtado Sierra. It was being im-

proved along the process of design to make it more resistant. In the worst case and take into account

the Shell Eco-Marathon rules, the total weight of the car would be 205 kg (excluding the driver).

Then, to verify the behaviour of our structure, it is considered that the rear axle hold 80% of the total

weight, whereby each structure corresponds 40% of total weight. The material used to manufacture

it will e “Al- 0 5 T6”. This alloy has high strength and offer good welda ility.

Source: Alcoa Mill Products, Alloy 7075 Plate and sheet [Online]

Available at: http://www.alcoa.com/mill_products/catalog/pdf/alloy7075techsheet.pdf [Accessed 12

November 2012].

First Design – Rectangular

It was a simple structure with rectangular profile section, as you can see in the Image 41 and the

appendix 1.1.7 the structure had to be modified with respect to Image 40 because the track width

must be 80 cm measured between the midpoints where the tyres touch the ground. Then, it needed

an inclination angle of its bars.

In order to check how big was the stress and compared to yield stress of our material, it used ANSYS

Workbench 14.0. The union between bars and rectangular support will be done by welding. Structure

needs to be improve because the stress ANSYS results are too high8.

Second Design – Circular

For the purpose of improve our first design, it will be changed into circular bars. It is selected a circu-

lar section normalized of 16x13mm. This design has a lot of improvements comparing it with the

7 Appendix 1.1.: Dimensioned Drawings - Rear attachment and rear brakes

8 Appendix 1.1.: Dimensioned Drawings - Rear attachment and rear brakes

Image 40: First freehand drawing. Image 41: Inventor 3D drawing of first design.


14.12.12 46

previous. The inner bars have not angle and consequently the rectangular support will be narrower.

This is an important breakthrough because it needs to be attached to the cockpit in a small pink

space as you can see in the cross Section of the cockpit in the image 43.

The moment of inertia is the same on different planes so behaviour of this design will be better to

hold axial loads when the car takes a curve. But it should still stiffen between the two parts because

Von Misses Stress is still too high.

Third Design – Reinforced Circular

The third design is an improvement of the previous prototype. It was added horizontal bars to avoid

the relative displacement between two parts and vertical and diagonal bars to give more strength

and get down the stress. It was added an axle holder for the wheel by welding. The diameter will be

18 mm. Now, as you can check in the Appendix 1.2.: ANSYS Calculations, the stress is acceptable con-

sidering our material and its yield strength.

Calliper Bracket

It needs to install the calliper brake for the disc brake. At the end of our structure it will make acces-

sory (Image 46) in order to mount our calliper bracket. The calliper bracket is an own design depend-

Image 42: Inventor 3D drawing of cicular de-sign.

Image 43: Inventor 3D Cross Section of Cockpit.

Image 44: Inventor 3D drawing of second cicular design.

Image 45: Inventor 3D drawing of Axle Holder


14.12.12 47

ing on the position of our brake disc as you can see in the Image 47. It is shown in detail in the Ap-

pendix 1.1.: Dimensioned Drawings.

System of mounting and fasteners used

To the connection it used a couple of olts “DIN 6 1 M4 x 1 ” and nuts “ISO 4035 M4” as you can

see in the Image 48. More details in the Appendix 1.1.: Dimensioned Drawings.

Now, it can be installed our calliper brake. The calliper brake will be a standardized one and the disc

brake as well. The calliper rake is the model “Hope M4 calliper” and disc brake is taken from

“Gra Cad”.

The disc brake will be attached to our hu motor wheel y means of 6 olts “ISO 380 M5 x 10”.

Source: GrabCad [Online] Available: http://grabcad.com [Accessed 5 November 2012].

Image 46: Inventor 3D drawing of accessory for the bracket

Image 47: Inventor 3D drawing of bracket

Image 49: Inventor 3D assembly Bracket & Attachement.

Image 48: Inventor 3D fasteners to the bracket.


14.12.12 48

Fasteners to hold the wheel on the rear attachment

To fix our wheel to the structure it is needed a couple of nuts and washers. The nuts will be “ISO 4032

M18” and washers will be “ISO 7089 18 – 140 HV”.

Connection system of the rear attachment

The connection of the rear attachment to the chassis it will use 8 olts “ISO 401 M8 x 30” 16 wash-

ers “ISO 0 8 8 – 140 HV” and 8 nuts “ISO 403 M8”9.

The placement and tightening nuts and bolts will be complete before to the full mount chassis be-

cause later it will not have access. It is possible to enable an access for possible future repair. It is

used the application “Calculation of olted connections from Inventor 013” to know how many

bolts it will need. You can see that in Appendix 1.2.: ANSYS Calculations.

Complete assembly with motor hub

The motor hu will e standardized one and the model will e “ 000W 13 inches rushless hu mo-

tor”. This hu motor has 13’’ of rim according to the Shell Eco Marathon Rules. Here in the Image 53

9 All fasteners and fastening components used above are made from the li rary “Autodesk Inventor 013”.

Image 50: Inventor 3D assembly nuts+washers wheel.

Image 52: Inventor 3D assembly back inner connection

Image 51: Inventor 3D assembly external connection


14.12.12 49

is the final solution taken. You can take a look in more detail in the Appendix 1.1.: Dimensioned

Drawings in sheet 10/10.

Source: DIYSite.com Limited, 2012, 2000W 13'' brushless hub motor [Online]

Available: http://www.diytrade.com/china/pd/7980427/2000W_13_brushless_hub_motor.html [Ac-

cessed 7 December 2012]

Conclusion

According to the calculation Von Misses Stress, the structure should suffice for future loads and re-

quirements. I think I have oversized structure sufficiently, giving it a high safety factor, as you can see

in the Appendix 1.2.: ANSYS Calculations, to make sure that this is enough stiff but considering

weight gain involved. Thinking about the race and my aspirations are to participate and win it, I

would like to improve this design in the next semester and everything pertaining to the manufacture

of the car. We have come a long way and we have made great progress in our design, but this is just

the beginning and new goals for the car are on the way in the next step.

I hope this comes to fruition and we can participate and win.

Image 53: Inventor 3D Complete assembly of rear axle.


14.12.12 50

5. Own work: group 4

5.1 Roll cage, by Michiel Bosch

Introduction

The roll cage for the vehicle was designed by Michiel Bosch. The roll cage is a combination of person-

al design and group discussion, based on research and studies of existing roll bar and roll cage solu-

tions. The Shell Eco-Marathon rules state that the elements of the roll cage need to withstand a force

(no impact) of 700 N from any direction. The most important property of the vehicle throughout the

entire project is the total weight. For this purpose a hollow tubular profile was selected for the roll

cage elements, using aluminium grade 7075-T6. This alloy is used for structural purposes (including in

the automotive sector) and has high strength at a low weight while offering good weldability.

Source: ASM Aerospace Specification Metals Inc., ASM Material Data Sheet [Online]

Available at: http://asm.matweb.com/search/SpecificMaterial.asp?bassnum=m4130r [Accessed 5

October 2012].

Research

The research10 involved in the design of the roll cage was all performed on the internet. In the first

stages of the research work, existing roll bar, roll cage, roll panel and monocoque solutions were

examined by browsing images available on Google Search. Retailer websites showed solutions which

did not match our needs; they were either too big or too heavy. The ideal solution would be to ac-

quire the raw elements and assemble them into a working product ourselves.

Design concepts

Image 54 visually represents the main elements of

the roll cage implemented into the vehicle chassis.

The roll cage consists of five straight hollow tubes

welded together at intersection points, one bent

hollow tube and six brackets made of the same

aluminium alloy. The endpoints of the roll bars are

welded to the brackets which are attached to the

carbon fibre frame using bolts and resin.

The final profile which was used has an outer di-

ameter of 30 mm and an inner diameter of

25 mm, though the initial idea was to use a

40/30 mm profile.

10 Appendix 1.4.: Roll-over protection

Image 54: 3D assembly in SolidWorks.


14.12.12 51

Below are some of the original concept sketches for the roll cage design.

One option was to create a solid roll panel

behind the driver seat. The roll panel would be

attached to the frame and separate the driver

from the motor compartment behind him.

This would not only function as rollover pro-

tection, but would also provide a solution to

another rule which says the driver should be

separated from the motor compartment. The

panel would effectively work as a bulkhead

and keep the driver safe in case of motor fire.

The downside to this design was the massive

weight; estimations ranged from 30 to 80 kg

based on the material and thickness of the

panel. This idea was scrapped during one of

the project meetings due to its weight.

A second idea was to use a single hollow metal

tube to act as a single roll bar. The rules are

unclear as to whether such a design is suffi-

cient, ut several pictures from other team’s

cars show similar designs. This was the lightest

proposed solution to the problem. The team

found the design too insecure and thought it

could yield many attachment problems; hence

this idea was also scrapped during one of the

meetings.

Image 55: Roll panel idea sketch.

Image 56: Roll bar idea sketch.


14.12.12 52

A third idea was to use an entire

frame consisting of stiff square-

shaped hollow metal bars welded

together at intersection points.

This design also resulted in a high

weight, as the original designs only

took steel alloys into account as a

material choice. This idea formed

the basis of the final design.

One more idea which was generated but not sketched was based on the image 58 below; a mono-

coque11.

The concept of a monocoque was

mentioned in the competition rules.

The idea is to create the frame and

roll cage as one part, made out of

reinforced carbon fibre composites.

Although interesting, this idea was

scrapped due to its immense com-

plexity, costs and the unreliability of

carbon fibre composites during im-

pact. Technical drawings of the final

design can be found in Appendix

1.1.

11 Source: carbon-fibre coating the monocoque [Online]

Available at: http://paulsf1.wordpress.com/2012/05/18/carbon-fibre-coating-the-monocoque/ [Accessed 5 October 2012].

Image 57: Roll frame idea sketch.

Image 58: Carbon fibre monocoque.


14.12.12 53

Analysis

The most critical element in the entire roll cage is the front tube due to its length. Calculations were

performed to find the bending moment stress, shear stress and the equivalent von Mises stress in

the original 40/30 mm profile with a 700 N force applied in a perpendicular direction to the middle of

said tube. This provides a reaction force of 350 N at each endpoint of the tube. While ignoring the

effect and strength of the welded connections, the calculations yielded the following results:

= 165095Nmm

(

)

Normal bending stress ⁄

(

)

Shear stress ⁄

√

Equivalent von Mises stress ⁄

Since these results are very low, the decision was made to change the profile size of the tubes to

30/25 mm to further reduce the overall weight of the vehicle. The new calculations yielded the fol-

lowing results:

= 165095Nmm

(

)

Normal bending stress ⁄

(

)

Shear stress ⁄

√

Equivalent von Mises stress ⁄


14.12.12 54

A finite element analysis was done using ANSYS Workbench 14 to support the calculations. Using the

same setup as was used for the calculations, the following result was achieved:

Image 59: FEA of the rollbar

The Von Mises result near the middle of the diagonal bar is roughly 35 N/mm2 which shows a differ-

ence of 26 N/mm2 compared to the calculated value. The reason for this difference is unknown, but

can be due to several reasons which have been discussed in Michiel’s finite element method course

project which is not part of this report.

Conclusion

According to all calculations and analyses, the 30/25 mm profile should suffice for the roll bar struc-

ture. I do not posses enough practical experience to be able to assess these results properly; I am not

certain if I want to trust such a thin aluminium profile to be able to hold a force as specified in the

Shell Eco-Marathon rules. Since this roll bar assembly is one of the things which will be checked be-

fore we are allowed to participate in the race, I would not want our team to get disqualified due to a

failure on my part. Hence, to be on the safe side, I will consult with experts before actually using this

(or any other) profile for the roll cage. Had our group been accepted already to participate in the

race, we would have been able to buy the materials (with the help of sponsors) and assemble and

test the roll cage solution.

The final result will include a bulkhead polymer made out of a mixture of aluminium sheets (for

structural support) and a synthetic material called aerogel, separating the driver from the mo-

tor/battery compartment. Aerogel offers protection against fire and heat while being extremely

lightweight.

Source: Wikipedia, Aerogel [Online]

Available at: http://en.wikipedia.org/wiki/Aerogel [Accessed 5 October 2012].


14.12.12 55

5.2 Safety equipment, by Ana Isabel San Agustín

The driver equipment

According to the rule, teams are required to provide and use the following at the event:

a) Gloves for general work:

Source: sportsbikeshop ltd. 2012, Spada Freetime Glove – Black [Online]

Avaliable at: http://www.sportsbikeshop.co.uk/motorcycle_parts/content_prod/52052 [Accessed 3

December 2012]

b) Gloves for fuel or motor oil handling: Chemical resistant.

We chose nitrile gloves because nitrile is a synthetic rubber that has anti-microbial properties and is

resistant to acid, chemicals, oils, solvents, greases and petroleum-based fluids.

Source: MSC Industrial Direct Co., Inc., 2012, Chemical Resistant Gloves [Online]

Available at:

http://www1.mscdirect.com/cgi/NNSRIT2?PMAKA=00255661&PMPXNO=1658223&cm_re=ItemDeta

il-_-ResultListing-_-SearchResults [Accessed 3 December 2012]


14.12.12 56

c) Safety glasses for all team members. (Disposable types are permitted).

Source: DX.com, 2012, Safety Goggles Glasses with Elastic Strap – Black [Online]

Avaliable at: http://dx.com/p/safety-goggles-glasses-with-elastic-strap-black-121659 [Accessed 3

December 2012]

d) Hearing protection for all team members (approved earplugs or muffs).

Source: Parker Industrial Safety, 2011, QM24+ Quiet® Muff Earmuffs [Online]

Avaliable at: http://www.parkerindustrialsafety.com/GroupInfo/GroupID/26 [Accessed 3 December

2012]


14.12.12 57

e) All Drivers must wear a racing suit as the outermost layer of clothing (fire retardant highly recom-

mended) norm DIN EN 531.

Source Pegasus Auto Racing Supplies, Inc., 2012, OMP Sport Single Layer Suit, SFI-1 [Online]

Available at:

https://www.pegasusautoracing.com/productselection.asp?Product=2634&utm_expid=10520551-

1&utm_referrer=https%3A%2F%2Fwww.pegasusautoracing.com%2Fgroup.asp%3FGroupID%3DSUIT

NONNOMEX [Accessed 3 December 2012]

f) Full-face helmet

Source: Motorcycle Superstore Inc., 2012, Vega Altura Lock 'n Load Helmet [Online]

Available at: http://www.motorcycle-superstore.com/14/67/905/36677/ITEM/Vega-Altura-Lock-n-

Load-Helmet.aspx [Accessed 3 December 2012]


14.12.12 58

g) Boots

Source: Wesco Performance Inc., 2012, Sprint Car Racing Boots by Crow [Online]

Available at: http://wescoperformance.stores.yahoo.net/drivingshoes.html [Accessed 3 December

2012]

Safety separator

The main thing with building this car is providing the driver with good security. For this reason it is

very important to separate the driver from the motor and batteries.

To increase the safety, some areas can be reinforced by additional woven carbon fiber laminates

(CFRP-crash) made of foam, attached to both sides of frame and body. This will decrease the danger

of critical injuries of the driver in case of a side crash.

The lithium ion battery is mounted ehind the driver’s seat and should e fit in a stainless steel ox

to avoid damage. In case of an impact, the attery won’t e damaged. To protect the driver against

possible danger from the battery, the rear of the vehicle is equipped with a self-extinguishing separa-

tion-wall. A metal coating in the rear prevents heat from getting to the driver’s compartment.

These security actions will decrease the danger of critical injuries of the driver in case of a side crash.

Source: Schluck specht (A student project of the University of Offenburg), 2011, safety improvement

[Online]

Available at: http://www.schluckspecht.net/index.php?page=safety_2011 [Accessed 21 November

2012]


14.12.12 59

Connect the chassis with the body

Bolt:

Advantages

Can be easily removed (for inspection or packaging)

Can join different materials, with different types of manufactured composite laminates, heat

treatment, etc.

No residual stresses or warping of the structure

Does not change the thermal treatment of the bonded parts

Disadvantages

The board is weak in the parts to be joined

Concentrations bring tension into the holes

Can loosen or weaken against dynamic stress and to changes in temperature

corrosion may occur in the nut or bolt head

They usually require binding supplements

Glue:

Advantages

Produces no deformation in the pieces

Noise and vibration are reduced

Disadvantages

The connectors are not removable

You have to wait till the glue is dry

Rivet:

Advantages

Cheaper than other joining methods

Can join two or more pieces and not necessary the same material

No action loosened by dynamic stress (vibrations in general)

Disadvantages

Used in permanent structures

Requires the creation of holes, which can damage the composite material

There is a concentration of stresses in the area of holes

Welding:

Advantages

Sealed from fluids


14.12.12 60

Have equal or greater strength than the base metals

Allows the construction of highly complex parts, impossible or dangerous to other manufac-

turing processes while being lighter than their counterparts (casting)

Disadvantages

You can change the heat treatment of the parts to be joined

The connectors are not removable

Items can warp

Residual stresses can occur

Few kinds of metal can be joined

These are the ways to connect the chassis with the body. I think the best way to connect it is by

knowing where put the joint after considering the advantages and the disadvantages.

For example:

Jacking points are the best suited place to mount pull clamps as they are very strong due to rein-

forcements. The most common method of clamping a composite chassis is a clamp that fits into ex-

isting holes in the chassis. It may also be done by clamping the chassis with a vice type system but

the vice system is less secure and may slip when pulling to straighten the chassis.


14.12.12 61

Calculating the motor power

P = power

= air density

A = car area (width x height)

Vw = velocity of the wind

Cv =aerodynamic coefficient, which is dimensionless

k = rolling resist coefficient

g = gravity

v = reference speed

θ = angle

a = acceleration

Therefore:

After knowing these formulas we started to create the Simulink model

v

θ

v · sinθ


14.12.12 62

Image 60: Simulink model for motor power calculation.

PD: control action proportional-derivative, is defined by:

where Td is the derivative time constant. This action has an anticipation character, making the con-

trol action faster, but has the major disadvantage that it amplifies noise signals and can cause actua-

tor saturation. The derivative control action is never used alone, because it is only effective during

transient periods. The transfer function of a PD controller is:

When a derivative control action is added to a proportional controller, which allows obtaining of a

high sensitivity controller, this is, it responds to the rate of change of the error and causes a signifi-

cant correction before the error magnitude becomes too large. Although no derivative control direct-

ly affects the steady state error, the system adds damping and therefore allows a larger value than

the gained K, which causes an improvement in the precision in the steady state.

We used these parameters:


14.12.12 64

And the outputs we obtained are:

Image 61: Simulink model resultant outputs.

The power we need is a bit more than 3000 W, but maybe after building the car the mass increases

and sometimes the reality is worse than the calculations; so we decide to choose a motor with 4000

W of power.

We chose a wheel hub motor because it has several advantages. Some of them are:

A wheel hub motor means that the whole motor is integrated in the rim of the wheel. You do not

need a gearbox, a clutch and other things, to transmit the power of the motor to the wheels. The rim

is designed and built by ourselves. The special thing about our rim is that it will be made of carbon

fibre.

Eliminates drivetrain losses, harmonics and gear backlash

No gears – extremely quiet

Electric motor can compensate for gear-shift torque disturbances from ICE to enhance

driver comfort

Provides lots of low-end torque

Enables higher level of vehicle control flexibility (natural tie-in to AWD and stability con-

trol and capability to control torque at each wheel independently and selectively)

More even mass distribution for better handling and driver comfort


14.12.12 65

Universally applicable to anything with wheels

How it works:

The coil, which is the non-rotating part of the motor, is attached to the axis. The magnets are fixated

on the rim, which is the rotating part of the motor.

The direct current, which is supplied by the fuel cell is modulated by the motor controller and sent to

the coil with a specific frequency. Due to that, the single phases of the coil get the current at differ-

ent times. The current through the phases exerts a force to the magnets, which makes the motor

turn.

Source: Schluck specht (A student project of the University of Offenburg), 2011, wheel hub motor

[Online]

Available at: http://www.schluckspecht.net/index.php?page=motor-city-eng [Accessed 28 November

2012]

Conclusion

According to all calculations and analyses and in accordance with the Shell Eco-Marathon rules, for

safety reasons the maximum voltage on board of any vehicle at any point must not exceed 48 Volts

nominal and 60 Volts max.

All of the wheel hub motors with this power have a rated voltage of 60V, so we decided to put 2 hub

motors with 2000W each.

The best solution for a hub motor with these characteristics and with 13 inch rims (the rim of our car)

can be seen on the next page.


14.12.12 66

Image 62: Selected hub motor specifications.

Source: DIYSite.com Limited, 2012, 2000W 13'' brushless hub motor [Online]

Available at: http://www.diytrade.com/china/pd/7980427/2000W_13_brushless_hub_motor.html

[Accessed 7 December 2012]


14.12.12 67

5.3 Safety equipment, by Ioana Costin

Introduction

This part of the project deals with ensuring the main safety requirements specified in the Shell Eco-

Marathon rules12. It refers to seat selection, locating and anchoring the seat within the chassis, seat-

belt selection, connecting it to the chassis and study of driving visibility and ensuring safe exit from

the vehicle. In addition, other required safety equipment is taken into account such as the driver’s

racing outfit, team mem er’s equipment and positioning of hand held fire extinguisher within the

cockpit.

5.2.1 Seat selection, fitting and anchoring

Introduction

The main concerns regarding the driver’s seat were to ensure the safety of the driver during the race,

to choose the material from which it is made so that it contributes to the lightweight general concept

of the vehicle and the way to connect it to the chassis. Along the development of the project, the

chassis has been modified and so the seat had to be refitted and resized.

Source: Tillett Racing Seats [Online]

Available at: https://www.tillett.co.uk/shop/shopDisplayCategories.asp?id=9&cat=Car+Racing+Seats

[Accessed 6 October 2012]

The rules do not mentioned anything specific about the type of seat, which gave us a lot of options

and at the same time taking into account the driving position article13 which prohibits head first driv-

ing position and the fact that a safety harness must be mounted onto the seat14.

As time was a limiting factor and the available resources were also limited we decided not to design

and manufacture our own seat. Instead, we would select one from a manufacturer.

In the beginning of the process the choice of material was debated15, the main criteria which were

taken into account were:

the driver’s safety

the weight of the material used for the seat

small dimensions

The two most safe and lightweight materials taken into account were aluminium and carbon fibre.

The two options were ranked using a grading scale from 0 to 5, zero being the worst and 5 being the

best rating attributed for that property.

12 Appendix 2.2.: Shell Eco-Marathon Rules

13 Literature survey: Article 33

14 Literature survey: Article 29, paragraph g

15 Appendix 1.5.: Presentations: Seat and seatbelt.pdf


14.12.12 68

This can be seen in the following table:

Table 1 – Evaluating Options

Options Aluminium Image source: HRP Aluminum Road Race Seat [Online] Available at: http://www.proracestore .com/ index.php?main_page=index& cPath=3446_3830 [Accessed 6 October 2012]

Carbon fibre Image source: tillett-car-seat-brochure [Online] Available at: https://www.tillett.co.uk [Ac-cessed 6 October 2012]

Light weight 2 4

Safety 4 4

Smallest size 3 4

Choice(Total) 9 12

Therefore, the carbon fibre seat is the one which has been decided to use.

The product which complied with our needs has been chosen from Tillett Racing Seats16.

The manufacturer provided an online brochure17 from which we picked the B2 racing seat model

along with the corresponding aluminium TB1 brack-

ets18 because it provided the balance between: low

dimensions, possibility of fitting the required safety

harness, low weight (only 2,75 kg19 for the seat and

1,06kg for the brackets) and because it can be adjust-

ed in different positions on the bracket as can be

seen in Image 63.

The next step after having selected these two com-

ponents was to fit the seat and aluminium brack-

ets20onto the chassis and finding out if they match the

space of the chassis and if they do not interfere with

the design of other major components.

16 https://www.tillett.co.uk/

17 Appendix 2.3.: tillett-car-seat-brochure

18 Appendix 2.3.: TB1 - bracket info

19 Appendix 2.3.: Tillett Seat Dimensions Catalogue

20 Appendix 1.4.:Calculations for seat fitting

Image 63: TB1 mounted bracket Image source: tillett-car-seat-brochure [Online] Available at: https://www.tillett.co.uk/ [Accessed 6 October 2012]


14.12.12 69

Because the manufacturer hadn’t made the seat using a CAD model, but by direct hand sculpture of

the material for more accuracy21 we were able to make a rough CAD model22 of the seat using the

given dimensions8.

Framing the seat onto the chassis has een done using the dimensions given in the manufacturer’s

catalogue8 (Image 65) and the dimensions established in the chassis design part23 (Image 64).

The calculations24 use basic geometry rules aiming to find out how much space is left after the seat

and brackets are installed and where exactly they are located in comparison to the cockpit dimen-

sions.

Therefore, the location of seat anchors is defined.

Image 64: Chassis dimension

Connection of the brackets with the chassis floor is done by using bolts from the anchoring kit25 pro-

vided by the manufacturer as shown in Image 66.

21 Appendix 1.4.:Mail

22 Appendix 1.1.:Seat-CAD model

23 Appendix 1.1.:Chassis:Technical drawings of cockpit: Chassis column

24 Appendix 1.4.:Calculations for seat fitting

Image 65: Seat dimension Source: Tillett Seat Dimensions Catalogue [Online] Available at: https://www.tillett.co.uk/shop/documents/downloads/B2-Info-17052012.pdf [Accessed 6 October 2012]


14.12.12 70

Conclusion

To sum up, after selection of material type, seat and bracket type and calculations of seat framing

the left space between the front edge of the seat and the front panel is of 27.5 cm. This leaves

enough space for the driver’s feet, for the steering column, pedals and an easy exit from the vehicle’s

cockpit without getting injured.

Also, on both sides between the bottom of the seat and the column of the chassis without taking into

account the space left y the curvature of the seat’s ottom there are left 5, 5cm.This space is ig

enough for anchoring the safety harness.

5.2.2 Seatbelt selection, fitting and anchoring

Introduction

The seatbelt limits the forward motion of the driver. It

slightly stretches to absorb energy, to lengthen the time of

the occupant's deceleration in a crash therefore, reducing

the load on the occupant’s ody. It prevents the driver from

being ejected from the vehicle and ensures that they are in

the correct position.

Source: Schroth Racing [Online]

Available at:

http://www.schrothracing.com/competition/latch-link-

16.1/LL-III-5 [Accessed 6 October 2012]

The rules26 specify that the seatbelts must have at least 5

mounting points which meets FIA Standards. As a conse-

quence, a 5 mounting point seatbelt has been chosen27 from

Schroth Racing. It weighs 1,98kg.

A fitting manual has been provided by the manufacturer28 which was used as a guide for fitting the

harness. In this manual dimensions of the selected safety harness are given.

25 Appendix 2.3.: Tillett-features-pricelist


27 http://www.schrothracing.com/competition/latch-link-16.1/LL-III-5

Image 66: Anchoring kit Source: Tillett-features-pricelist [Online] Available at: https://www.tillett.co.uk/shop/documents/downloads/TB1%20with%20B1%20bracket%20info.pdf [Accessed 15 November 2012]

Image 67: Schroth Racing 5 point seatbelt Source: Schroth Racing [Online] Available at: http://www.schrothracing.com/competition/latch-link-16.1/LL-III-5 [Accessed 6 October 2012]


14.12.12 71

Another thing which has een taken into account is how the elts should pass across the driver’s

body when they are fitted. All in all, each belt should pass over the strongest bone in the aimed re-

gion of the body, such as:

the shoulder belt must pass over the clavicle

the lap belt must pass over the iliac crest

the anti-sub belt(anti-submarining belt) should pass over the pelvic bone

The five point seat belt is an important component of the safety measurements which must be taken

because each of the belts protects certain vital organs or areas of the body from serious or even fatal

injuries:

Shoulder elts protect the driver’s torso and vital organs such as heart, lungs etc.

Lap belts together with the anti-sub belt protect from internal injuries to the kidneys,

liver etc.

The next step was anchoring the belts as follows:

28 Appendix 2.3.: seat-belt-fitting-information-2012

Image 68: Dimensions Profi III-5 seatbelt Source: Schroth Racing [Online] Available at: http://www.schrothracing.com/competition/latch-link-16.1/LL-III-5 [Accessed 6 October 2012]


14.12.12 72

Shoulder belts are wrapped29 (Image 69) around a 53cm aluminum alloy bar30 located

at a maximum distance etween the wall of the cockpit and the seat’s ack rest of

27, 31 cm .The bar is situated at 48,5 cm above the floor of the chassis and it is weld-

ed on each end to 1cm thick brackets of the same alloy as shown in Image 7031.

The square shaped brackets32 are connected to the inner space between the chassis

columns33 in the rear part of the cockpit as it can be seen in the first sketch34.


30 Appendix 1.1.:Bar and bracket

31 Appendix 1.1.: Bar and bracket dimensions

32 Appendix 1.1.:Bracket drawing-Michiel

33 Appendix 1.1.:Chassis assembly-Kriss (Appendix1.1.-technical drawings)

34 Appendix 1.3.:Bar sketch

Image 70: Bar with brackets Source: bracket designed by Michiel Bosch

Image 71: Bar on the chassis Source: chassis designed by Kriss Lidumnieks

Image 69: Shoulder belt connection to bar Source: Schroth Racing [Online] Available at: http://www.schrothracing.com/competition seat-belt-fitting-information-2012 [Accessed 20 October 2012]


14.12.12 73

Lap belts are anchored to the floor of the chassis this way

respecting the competition rules35 and the guide rules36.

A bolt in bracket B23C has been chosen according to the

guide, which will e olted in the chassis floor using ½’’

bolts from the installation kit provided by the manufac-

turer.

It will have a 0 turn as shown in Image 37.

Anti-sub belt is also connected through a bolt in brack-

et to the floor chassis but in this case the 0 turn will

be as shown in Image7326.

35 Literature survey: Article 29:c)


Image 72 ap elt- lt in acket- lt 0 Source: seat-belt-fitting-information-2012 [Online] Available at: http://www.schrothracing.com/competition seat-belt-fitting-information [Accessed 20 October 2012]

Image 73: Bolt in bracket for anti-sub belt Source: seat-belt-fitting-information-2012 [Online] Available at: http://www.schrothracing.com/competition seat-belt-fitting-information [Accessed 20 October 2012]


14.12.12 74

Along with these measurements, the routing38 of the belts has been taken into account in order to

ensure a maximum efficiency of the elt in case of an accident and also to ensure the driver’s com-

fort:

For lap belts the maximum distance between the 2 anchors is the outer dimension of

the seat’s ottom which is less than 44,5 cm.

Also, the elts have to e set at 60 -80 downward angle, measured through the hor-

izontal plane.

For shoulder belts the setting angle is maximum 0 measured through the horizon-

tal plane.

For anti-su elt it is recommended to have a maximum 0 angle measured to the

vertical plane so that it is tangent to the driver’s chest.

After taking into account all of the above mentioned measurements, the following decisions have

been made:

The shoulder belts are placed at a hori-

zontal angle because the straps are

wrapped around the aluminium bar

(Image 69).The distance between the

seat backrest and the middle of the bar being about 25,81 cm. In reality ,it will

be less because as mentioned before

the calculations are based on rough models of the seat and chassis.

This can be seen in Image 7439 and

Image7540.



39 Appendix 1.3.: Bar_sketch

40 Appendix 1.3.: Top view chassis seat brackets sketch

Image 74: Side view-shoulder, lap and anti-sub seatbelts Image source: seat-belt-fitting-information-2012 [Online] Available at: http://www.schrothracing.com/competition seat-belt-fitting-information [Accessed 20 October 2012]


14.12.12 75

The anti-sub belt and an-

chor are placed tangent to

the driver’s chest (Im-

age7428) on the midline of

the chassis at 58,5 cm from

the front of the chassis (Im-

age 7529).

The lap belts and anchors

are placed at a 60 angle

measured from the horizon-

tal plane, 44,5 cm apart and

in line with the seat’s rack-

ets (Image 74 and 75)

Conclusion

To sum up, by taking into account the competition rules41, the guidelines42 provided by the manufac-

turer, personal sketches43 and calculations44, it can be concluded that the chosen model of seatbelt

and method of anchoring provide optimum protection against accidents during the race.

5.2.3 Selection of fire extinguisher

Introduction

A fire extinguisher is also important safety

equipment which may prevent a disastrous

event from happening. The requirement for a

fire extinguisher is specified in the rules45.

Taking into account these requirements and

with the help of Table 2 a hand held 1 kg fire

extinguisher has been selected Table 346.



43 Appendix 1.3.: Bar_sketch

43 Appendix 1.3.: Top view chassis seat brackets sketch

44 Appendix 1.4.: Calculations for seat fitting


46 Appendix 2.3.: Fire extinguisher bracket catalogue

Image 75: Top view chassis seat brackets sketch

Table 2 - Types of hand held fire extinguishers Image source: Wikipedia – Fire extinguisher [Online] Available at: http://en.wikipedia.org/wiki/Fire_extinguisher#United_Kingdom [Accessed 15 November 2012]


14.12.12 76

In addition, a bracket into

which the tube is held is

mounted on the wall of the

chassis in the cockpit, so that

it is accessible and does not

harm the driver while the

vehicle is moving.

The racket’s length is given

by the manufacturer as being

387,5 mm and with a base

diameter of 144 mm.

The bracket will be bolted into the wall as shown in the following sketch (Image 7647):

47 Appendix 1.3.: Fire extinguisher bracket fitting

Image 76: Fire extinguisher bracket fitting.

Table 3 - Selected ABC type fire and fire extinguisher bracket Source: Amerex fire extinguishers [Online] Available at: http://amerex-fire.com [Accessed 15 November 2012]


14.12.12 77

5.2.4 Study of driving visibility

Introduction

While driving, the road visibility must not be impaired. Also the peripheral vision plays a significant

role in driving, so it is most important that the cockpit’s structure allows clear viewing of the sur-

rounding space and of the side mirrors.

The competition rules48 require clear visi ility ahead and to a 0 arc on the longitudinal axis of the vehicle (Image 7749). Taking these facts into account a sketch was made on the basis of a practical simulation using the

handmade model in order to ensure the conformity with the rules.

By measuring the mirrors50 on the 3D model of the vehicle it was concluded that they have an inner

area of 43,41cm2, therefore a higher value than the minimum required by the rules (25 cm2)51. Also

the distance etween the driver’s eyes and the mirror has been measured while simulating on the

model (Image77) and it is about 95,5 cm.

In Image 78 and 79 sketches have been made to verify if our concept of the vehicle passes the visibil-

ity test which will be conducted by a competition inspector, according to the rules52. At a 4 m radius

from the front of the vehicle, at every 30 over half a circle 60 cm high locks have een situated and

48 Literature survey :Article 28

49 Appendix 1.3.: Front and lateral view

50 Appendix 1.1.: Mirror dimensions

51 Literature survey :Article 28:b)


Image 77: Front and lateral view.


14.12.12 78

from the driver’s seat lines have een traced to the locks in order to o serve if the lines interfere

with parts of the body. In which case, it would mean that the required visibility is reduced and

changes of concept must be made.

Because the body of the car is only in the state of concept53 and the accurate length is not yet known,

an assumed length of 3 m has been used, which is between 2,2 m and 3,5 m which are the limits

imposed by the rules54.

53 Appendix 1.3.:Concept car Slava


Image 78 : Side view-visibility test Source: vehicle exterior designed by Viacheslav Rostovtcev

Image 79: Top view-visibility test Source: vehicle exterior designed by Viacheslav Rostovtcev.


14.12.12 79

Conclusion

From all of the above sketches and actual simulations on the handmade model, in this stage it can be

concluded that the future visibility test will have a favourable outcome. Furthermore, it is safe to say

that the driving visibility will not be impaired.

5.2.5 Fast exit

According to the rules55 of the competi-

tion exiting the vehicle should take less

than 10 seconds. After several adjust-

ments in chassis dimension, refitting and

resizing we were able to simulate on the

real scale model seen in Image 80 how

comfortable, fast and easy it is to exit the

space.

It has been concluded that the driver has

enough space to rotate his body towards

the exit, enough door opening through

which to pass and no other parts of the

assembly are present which could injure

him while exiting.


Image 80: Exit space


14.12.12 80

5.4 Chassis/Cockpit of urban concept vehicle, by Kriss Lidumnieks

5.4.1 Evaluating and choosing the concept

In the beginning of the project one of the first steps in the design process of the vehicle was to

choose and develop the concept of the chassis and cockpit. It is critical in the design of the vehicle as

other parts’ designs follow the chosen concept.

Three different concepts were created, based on already existing solutions in vehicle chassis design.

Other designs of vehicles in the Shell Eco-Marathon competition were studied and considered.

Version 1

The structure would be made out of composite material to make it as light as possible. The chassis

would consist of 3 parts. The different parts are connected with structural glue or bolts between the

sections. In the places where the structure is not stiff enough it could be stiffened with more rein-

forcement. The bulkhead which separates the driver from the engine compartment would be inte-

grated into the chassis design.56

Version 2

In the second concept design version the cockpit would be made using composite materials to make

it as light as possible. The frame structure would be attached to the cockpit for front and rear wheels.

The big sections on the both sides of the cockpit would carry most of the load. The bulkhead would

be integrated in the cockpit design the same way as in the first version.57

Version 3

The last version which was created is more common in the designs of other competitors. It would

have a frame structure made of steel or aluminium bars or tubes which carry all of the loads.58

Selection criteria and importance

The chassis should be as light as possible and at the same time be strong and stiff. It should be easy

to manufacture and analyse and the material should be available locally. According to these re-

quirements the following selection criteria were chosen:

As light and strong as possible –the most important factor as the main goal is to design a light

weight vehicle;

Strength and density chart is used to compare the material used to manufacture the chas-

sis;59

56 Appendix 1.3. – Kriss Lidumnieks, image 81



59 Appendix 2.3. – Material selection Charts, image 81


14.12.12 81

As light and stiff as possible – for making a rigid structure, this factor is also important con-

sidering the weight of the chassis;

Young’s Modulus and density chart are used to compare the material used to manufacture

the chassis;60

Manufacturability;

The material’s manufactura ility and processes used in manufacturing the chassis are com-

pared;

Ease of analysis;

For analyzing a composite structure, a more complex FEM analysis is needed compared to a

metal structure;

Material availability;

Most of the materials are available in a wide range from local suppliers.

The material availability was ranked as the least important because it is easy to get materials all

around the world from online suppliers and local distributors. Manufacturability and ease of analysis

are weighted equally. It is important that the structure can be analyzed to improve and optimize it.

The manufacturability has to be considered as the car will be built in the laboratory of the university

using the equipment available.

Ranking the concepts

The concepts were discussed in the group meetings and a rating was given for each criteria. The total

score and rank of concepts can be seen in the table below.

Table 4: Evaluation of concept designs

The concept with the highest score was chosen for further development.

60 Appendix 2.3. – Material Selection Charts, image 82

Version 1 Versioin 2 Version 3

Rating Weighted score Rating Weighted Score Rating Weighted Score

Light and strong as possible 30% 4 1.2 3 0.9 2 0.6

Light and stiff as possible 27% 4 1.08 5 1.35 2 0.54

Manufacturability 18% 1 0.18 3 0.54 5 0.9

Ease of analysis 15% 2 0.3 3 0.45 5 0.75

Material Avalability 10% 4 0.4 4 0.4 4 0.4

3.16 3.64 3.19

3 1 2

NO Develope NO

Total Score

Rank

Continue?

Concepts

Selection Criteria Weight


14.12.12 82

5.4.2 Design

The design of the cockpit is critical in the overall structure of the car. At the beginning of the project

the dimensions and design of the cockpit were specified to know how other parts can be designed.

The requirements were set from the Shell Eco-Marathon rules which have to be fulfilled during de-

velopment of the chosen concept:

place for the driver;

safety requirements;

place for luggage;

load carrying structure;

must be stiff and strong;

A real life model was created in the design lab using plywood, cardboard and other materials to un-

derstand the limiting dimensions. The team started first to make the drivers compartment depending

on the height and length of the driver while in driving position. By using this method the size of the

cockpit could be optimized depending on an ergonomic position of the driver.61

Main dimensions and propulsion and energy system isolation

The rules state that a permanent ulkhead must completely separate the vehicle’s propulsion and

energy storage systems from the driver’s compartment. This ulkhead must e of fire retardant ma-

terial and construction as well as prevent manual access to the engine compartment by the driver.

The bulkhead will be integrated in the design of the cockpit and will be one part.

According to the rules, the driver’s compartment must have a minimum height of 88 cm and mini-

mum width of 0 cm at the driver’s shoulders.

61 Appendix 1.3. – Kriss Lidumnieks

Image 81: Bulkhead and main dimension representation


14.12.12 83

The real life model showed that using the minimum dimensions mentioned in the rules would not

ensure an ergonomic position for the driver or allow for a quick exit. The dimensions were defined as

00 mm for the width and 1050 mm for the height of the driver’s compartment.

Doors and space for the driver

The minimum dimension for the doors must be 500x800 mm. In the cockpit design it is ensured that

there will be space for doors. When making the design it was also tested on the real life model how

easy for the driver it would be to exit the vehicle. The rules state that the driver has to be able to exit

the car in less than 10 seconds.

The required space for the driver was measured and adjusted in the 3D CAD model. It is necessary

that the driver feels comfortable while driving. The planning of dimensions can be seen in the Ap-

pendix of the real life model of the cockpit.62

Luggage space

Luggage space must be available for a rectangular solid box with dimensions of 500 x 400 x 200 mm

(L x H x W). This space must be easily accessible from the outside and must include floor and side-

walls to hold the luggage in place when the vehicle is moving. For drivers requiring ballast this box

must contain the ballast in a safe and secure manner.63

Image 82: Luggage space and dimensions

The designed luggage space can be seen in image 82 above. The decision was made to put the lug-

gage space in the front of the vehicle and to make a separate cabin for it. People will be able to ac-

cess it from the outside of the vehicle and there is room for a bag of size: 500x400x200 mm. The

structure made for the luggage can also be used to attach the front wheels brackets to.

62 Appendix 1.3. – Kriss Lidumnieks

63 Appendix 2.2. - Shell Eco Marathon Rules


14.12.12 84

5.4.3 Materials

The cockpit of the vehicle would be made out of composite materials. First the reinforcement and

composition of the materials have to be chosen.

The cockpit will be made of carbon fibre and flax fibre composite polymers. The matrix material used

to impregnate the fibres will be epoxy resin. Together with fibre reinforced polymer there will be a

balsa wood core material between the layers of fibres. The core material will be used to ensure the

stiffness of the structure. The total wall thickness of the sandwich structure is estimated to be 7-

10mm. The composition of the sandwich structure is explained in the picture below.

Image 83: Composition of sandwich structure

Balsa wood core is used because it has very good bonding with epoxy glue and it is very light. The

average density is 152 kg/m3.

Source: Dura Composites Ltd., 2008, Balsa Core Specifications [Online]

Available at: http://www.balsacore.com/balsa_core_specifications.html [Accessed 27 November

2012].

Carbon fibres are very strong and light. Use of this material will ensure that the structure can with-

stand loads while driving and light impacts during a crash. For withstanding the higher loads in case

of a crash there is roll bar design that will be attached to the cockpit.

Carbon fibre reinforced polymer density is approximately 1600 kg/m3 when having an epoxy matrix

with 70 % of fibre fraction.

Source: SubTechs, 2007, Epoxy Matrix Composite reinforced by 70% carbon fibers [Online],

Available at:

http://www.substech.com/dokuwiki/doku.php?id=epoxy_matrix_composite_reinforced_by_70_carb

on_fibers&DokuWiki=5794b57fe11ab873bdeac37bf21ed07a [Accessed 5 December 2012].

Flax fibres are a relatively new material in such applications. It is an organic fibre that has been used

for many centuries in the textile industry. Nowadays it has found a place in applications in car-, wind-

sport- and furniture industries. It has good strength to weight ratio and in our car’s cockpit the


14.12.12 85

weight is important as we tend to decrease the total weight in order to decrease the energy con-

sumption. Carbon fibres will be used to ensure the strength of the structure in all directions.

The use of flax fibre in automotive industry is also a very new process. The use of organic fibres re-

duces the overall CO2 footprint of vehicle construction as the energy used in producing the material

is low.

The approximate density of the chosen flax fibre reinforced polymer material is 1250 kg/m3. This

density value is determined from the values of the density of epoxy resin (1120 kg/m3, taken from

the data sheet of Axon technologies, epoxy resin: Epolan 5015) and the density of flax fibres (1450

kg/m3). This value was approximated for the density of the design to get the average weight of the

chassis and cockpit construction.

Source: LINEO Ltd., 2010, Discovery, density [Online],

Available at: http://www.lineo.eu/#!discovery [Accessed 5 December 2012].

The total density of the structure was calculated by taking a percentage of the different composite

materials in the sandwich. It was assumed that balsa wood thickness will be 5mm, carbon fibre layers

1mm and flax fibre layer 1mm. In total it makes for a 7mm thick laminate consisting of 72% balsa

wood and 14% carbon fibre and flax fibre polymer volume fraction. The densities of each material

are multiplied by volume fraction and the results are summed up. The total density of the sandwich

structure is 529 kg/m3. This design value is used to determine the weight of the cockpit made of

composite materials.

5.4.4 Structure

The main purpose of the cockpit in the design is to carry loads and secure the driver and passenger

from a possible crash or accidents. It is necessary to make the cockpit strong and stiff enough. In

order to make the cockpit stiff there are two big columns in the sides of the part. By making them

very thick in the whole length it is very stiff. The high and wide bulkhead separates the driver and

passenger from the motor and battery.

Stress Calculations

The stresses in the cockpit composite structure were calculated by simplifying it and assuming it as a

simple supported beam with a uniform profile.

Image 84: the dimensions of profile of cockpit


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There were two different loads assumed. One is the weight of the driver which is about 80 kg. The

other load is the weight of the car and the cockpit itself. This was assumed as a distributed load of

800 N/m. The total length of the cockpit is assumed to be 1,5m and the position of the driver 0,6m

from the right end.

Image 85: Free Body diagram of the simplified structure of cockpit

The reaction forces were calculated, and the shear force and bending moment diagrams are shown

below.


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Image 86: Shear stress diagram

Image 87: Bending moment diagram

The critical points in the structure were evaluated. The stresses were calculated where the highest

bending moment and shear forces appear.

The highest stress in the structure is 1.4MPa which is really small so the assumption can be made

that the structure is going to withstand the loads applied.


14.12.12 88

5.4.5 Manufacturing

In the design process it was important to think how it would be easier to manufacture the cockpit of

the vehicle. One of the ways is to make a square shape of the cockpit. The cockpit is divided into

many different composite parts which are manufactured separately and then glued together at the

end. By using this technique the manufacturing is simpler and more cost efficient.

A vacuum bagging process will be used in manufacturing the cockpit which is one of the available

polymer composite processing techniques.

For fabricating the cockpit, different parts will be made and then glued together with structural

epoxy glue. Moulds for different parts will be made. For some of the parts it might be necessary to

make multi sectional moulds because of the geometry of the parts. Drawings of different composite

parts of the cockpit can be seen in the appendices.64

64 Appendix 1.3 - Drawings of cockpit


14.12.12 89

5.5 Windshields, by Kriss Lidumnieks

5.5.1 Design

The designs of the windshields are taken from the final design of the body. The viewing angles are

assumed and the right size and shape windows are drawn up.

5.5.2 Material

The windshields must not change shape or vibrate while driving. According to Shell Eco Marathon

rules the windows must not be made of any material which may shatter into sharp shards. The wind-

shields will be made from Polycarbonate (Lexan), which is recommended by the competition organ-

izers.

Polycarbonate is easy to shape, has good impact resistance and is transparent. The properties make

it a good choice of material for the windshield.

University of Cambridge, 2002. Material Selection [Online] (Updated 24 Oct 2002)

Available at: http://www-materials.eng.cam.ac.uk/mpsite/materialsdb/default.html#Polycarbonate

[Accessed 3 December 2012].

5.5.3 Manufacturing

A drape forming process will be used to manufacture the windshields.

Drape forming is the simplest of the techniques used in thermoplastic forming. In the process guide

the technique is explained in more detail: “Using a male or a female mould, the sheet is heated and

allowed to conform to the shape of the mould under its own weight or with slight mechanical pres-

sure. The process involves placing the sheet (without the masking) and mould in a hot-air circulating

oven. The temperature is raised to the point where the sheet sags (between 140°C-155°C) and con-

Image 88: Design of the body. The shape and size of the wind-shields


14.12.12 90

forms to the shape of the mould. Both items can then be removed from the oven and allowed to

cool.”

GE Structured Products, 2001. Lexan Processing Guide. [internet] England: Gilbert Curry Industrial

Plastics Co Ltd.

Available at:

http://www.theplasticshop.co.uk/plastic_technical_data_sheets/lexan_polycarbonate_sheet_proces

sing_guide.pdf [Accessed 3 December 2012].

5.5.4 Attachment to Body

Rivets will e used to attach the windshield to the ody. Use of rivets won’t increase the air re-

sistance significantly as the head is smooth. The requirement is also that there are no sharp objects

in the driver’s compartment. The use of screws instead of rivets would introduce sharp objects into

the cockpit.

Image 90: Typical Pop-Rivet Assembly

GE Structured Products, 2001. Lexan Processing Guide. [Online] England: Gilbert Curry Industrial Plas-

tics Co Ltd.

Available at:

Image 89: Drape forming process.


14.12.12 91

http://www.theplasticshop.co.uk/plastic_technical_data_sheets/lexan_polycarbonate_sheet_proces

sing_guide.pdf [Accessed 3 December 2012].


14.12.12 92

5.6 3D model of the bodywork, by Josué Martínez Peña

The model of the bodywork is based on the design sketches created by Viacheslav Rostovtcev.

5.6.1 Making the frame

The frame lines

Once we had the concept car, I started to work on the model using the CAD software “Autodesk In-

ventor” which is the software I have een using this year for CAD modeling. I needed to e sure that

our design fits the dimensions established in the competition rules and that the chassis can be put

inside it. For that purpose, some pictures of the concept car were taken and put in Inventor. As can

be seen in the images below, the roof, the wheel size and the distance between the axes were rede-

fined in order to fit the conditions mentioned above.

Image 91: Side view

Next, perpendicular lines from the side view were drawn in order to

get the line frame for the surface modelling.

For making these lines, I wanted to draw lines in 3D sketch mode, but

I didn’t know how to make them perpendicular to the side-view

plane.

The solution was making these lines in 2D sketch mode. But for mak-

ing this kind of sketches, they should be placed in planes. So a plane

had to be created in each point where the lines were needed. Image 92: Main line


14.12.12 93

After the planes were created and each line was drawn in its plane, the 3D lines were drawn, as can

be seen in the picture below.

Image 93: 3D lines

Once the side view was redefined, it was time to do the same with the top view:

- Take the picture from the concept

- Draw an approximate silhouette of the car taking into account (Image 94):

o The competition rules

o The side-view drawing (including the points that are used for building the frame)

o The chassis silhouette

- Put the planes in the points in order to make the line frame

- Make the lines in 2D sketch mode into the planes (Image 95)

- Make the lines in 3D sketch mode (Image 96)

Image 94: Silhouette

Image 95: 2D sketch lines


14.12.12 94

Defining the main lines of the body work

When the line frame is done, it is time to define the main lines of the bodywork. For that, 3D splines

have been used. For our purpose, these splines are constrained to be in touch with the 3D lines of

the line frame.

5.6.2 Modeling Phase 1

Front part

With these curves, the first surfaces were made. For making the surfaces, first I tried creating small

patches but I realized that:

- For making the patches, the curves must be split and redone in order to get the boundaries

of each patch.

- The tangencies between the patches were not good, so I decided to use the Loft command.

First, two or more sections are needed for making the surface. Second but optional, rails can be used

in order to guide the Loft trajectory. These rails must be touching the sections.

Image 96: 3D sketch lines


14.12.12 95

Image 97: Lofting

One thing that has to be taken in mind is the tangencies between surfaces. For that purpose I decid-

ed to make sections that are tangent to the existing surfaces. As can be seen in the second picture, it

is hard to define the boundary between both surfaces

The command Project to Surface was used to create these curves. For that command it is required:

- Surfaces on which to project the curves and/or lines

- Curves and/or lines

- Direction of the projection

Curve tangent to the existing surface

Section curve belonging to the new Loft

Image 98: Surface & curve lofting.


14.12.12 96

In this case the line will be projected

onto the surface. For that, both lines are

selected and then the direction is chosen.

In this case that will be the X axis.

Here is the projected curve:

After making these surfaces, more curves were created using as reference the edges of the existing

surfaces and the curves belonging to these surfaces, in order to use the same procedure as has been

explained before. The results can be seen below.

In order to create some Lofts, some curves must be done again. For example, in the pictures, this

curve was discontinuous; but for making the Loft, it is an indispensable condition that either the rails

or the sections have to be continuous. So I needed to make a new 3D sketch including the geometry

of the curves that must were put together.

Image 99: Projection

Image 100: Curves results.


14.12.12 97

Here is how the Loft was made:

Image 101: Loft creation

Side surface

After making the surfaces of the front part, it was time to make the side part of the bodywork. In the

next picture, there are shown the curves that will define the shape of the side surface.

The result of the Loft can be seen in the picture below.

Curves made creating new sketches

based on discontinuous segments

Curves tangent to

the curves belonging

to the existing

surfaces

Curves belonging to the

existing surfaces

Curves attached to the

previous curves


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The Zebra analysis below consists of a surface continuity analysis using a stripe pattern. If stripes

edges are not continuous in a boundary, it means that the surface is not tangent. But, as can be seen

in the picture, the stripe edges in the boundaries are quite good. So the continuity between both

surfaces is quite good.

Rear part

Lofting was used instead of patching because the obtained surfaces are better. But here is an excep-

tion: for making the back part. As there is neither continuity nor tangency needed, the Patch com-

mand was used as can be seen in the pictures below.

Wheel arches edges

- First, the shapes of the wheel arches from the first sketch were extruded as a surface.

- Second, the cylindrical surfaces were cut using the same plane as which was used in the top-

view sketch

Images 102: Boundary patches


14.12.12 99

- Third, bodywork surfaces were trimmed by using them as cutting tools both cylindrical sur-

faces.

Top of rear part

For closing the back part, another Loft was used as can be seen in the pictures below.

Image 103: Loft creation

The roof

For making the roof, I decided to make a one-piece roof. The procedure was as in the previous sur-

faces. That is: creating the sections, creating the rails, and putting them in touch.


14.12.12 100

One thing that had to be kept in mind

was, obviously as can be seen in the

picture, the dimensions and position

of the chassis.

Other things to highlight are the

straight lines that are in touch with

the Loft sections.

These lines are used to make the

boundary between the two sides of

the bodywork as smooth as possible.

The curve sections are tangent to those lines which are parallel to the X-axis

The image below can be used to understand the process more easily:

After making the Loft, this is the result:

Image 105: Lofted result

Symmetry plane

Loft section curve

Lines parallel to

X Axis

Image 104: Curve sections


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One side is done, but the other one is still missing. For doing the other one, a mirror pattern was

used.

For using the mirror pattern two things are needed. First, the features that are going to be mirrored,

and second a mirror plane, which in our case was the plane used to create the side-view 2D sketch.

In the first attempt of making the mirror, there were some errors with some of the curves that

should be fixed. Those errors prevented the mirror from being created.

Once those errors were fixed, the model looked as follows:

Image 106: Preliminary result

5.6.3 Phase 2

As can be seen in the previous picture, the wheel arches are not good because they are outside the

body work. The edges between the side surfaces of the front of the car and the wheel arches are also

irregular. These issues have a negative impact on the aerodynamics of the vehicle.

As can be seen in the picture below, the surface has an irregular and non-continuous shape despite

the fact that in the zebra analysis it seemed good.


14.12.12 102

Image 107: Non-continuous shape

The roof surface had some dents that would also worsen the bodywork aerodynamics. Hence, it was

quite necessary to make changes to the body shape.

Front Wheel Arches

More curves were needed for making the new surfaces as can be seen in the images below.

The main criteria for making the curves in the front wheel arches was to make them tangent to:

- The plane created by the edge of the wheel arch

- The previous criteria of making tangent to curves belonging to the surfaces

For making the Lofts, I took the circular edge as a common rail for almost all of them.

Here are some of the Lofts:

Image 108: Wheel arch curves


14.12.12 103

Note: the sections of the last Loft shown (and the others between them) are not tangent to the plane created by the wheel arch edge. This is because in case of doing it that way, the surface shape would harm the aerodynamics.

In the picture below, the remodelled wheel arch is shown:

Image 109: Remodelled wheel arch

In the right picture above can be appreciated the

difference between the remodelled wheel arch and

the old one.

Rear wheel arch

For the rear wheel arch Loft, I made the surfaces as

follows.

First, I tried to make it just by doing two Lofts, as it

is shown in the next picture. It was good with the

first Loft, but I had problems establishing the rails

and sections of the Loft. This is because one of the

rails, as can be seen in the picture, is not a contin-

uous curve. That is, there is a sharp point there.

The solution for this problem was splitting Loft 2,

using as splitting point the sharp point from the

previous rail. So now there are 3 Lofts, as is shown

in the picture below.

Loft 1

Sharp

point

Loft 2

Loft 1 Loft 2 Loft 3


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For doing the Loft curves (sectors and rails), the procedure used is the same as in the previous sur-faces.

Below is shown the difference between the old and the current rear arch wheel.

Arriving to this point, this is how the model looks:

Image 110: Lofting differences


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Front part

If the model is seen in a more detailed way, using the curvature analysis, there are some problems

that must be fixed.

I realized that the fewer Lofts are created, the more continuous and higher quality the entire surface

will have. So I edited and deleted some of them in order to reduce the amount of Lofts (left picture).

Sections are neither parallel to each other nor tangent

to the next surface


14.12.12 106

Here is the front wheel arch Loft

As can be seen in the pictures above, the Loft sections are tangent to the radius of the wheel arch

edge. I found out that the results from this procedure are better than the other ones by making the

curves tangent to vertical and horizontal lines belonging to the plane created by the wheel arch edge.

Image 111: New wheel arch results


14.12.12 107

After making the rear wheel arch, I realized that the upper part of the rear wheel arch could be done

with less Loft patches, improving the quality of the surface.

Here is the difference:

In the pictures shown above there is not so much difference, but a deeper insight using the Zebra

analysis reveals an important difference between them


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Body side (1)

One of the things that I realized after having the wheel arches done was that the side part of the car

was quite irregular. Since the wheel arches and the roof were modified, the side part of the body

must be also modified. Because as is shown in the pictures below, there are some holes and discon-

tinuous surfaces that must be fixed. Note: colours have been changed in order to appreciate the

problems mentioned above.

In order to fix that problem, I tried to create a new surface between both wheel arch edges.

Images 112: Irregularities

Image 113: New surface


14.12.12 109

For making this surface, I had the same problem as when I made the rear wheel arch. This is, I had to

make this new surface making more surfaces.

For making Loft 1, I created some sections that are tangent to the planes created by the wheel arch-

es.

Unfortunately, there are still some problems (see red

circle in the picture) so additional modifications were

needed. In the shown case, it was enough to suppress

some surfaces (black circle in the picture).

Another problem that was found was that I was una-

ble to create the second surface using just one Loft. So

I tried to modify the Loft features, and as some of that

features affect the roof, I decided to redo the roof

also.

Loft 1

Loft 2


14.12.12 110

Roof remodelling

As has been said before, there were problems with the roof. For that, I decided to make a new one.

One thing that has to be said is that the roof curves are only tangent between them. They are not

tangent to the surfaces that do not belong to the roof ones, with the exception of the highlighted

edges in the right picture above.

Body side (2)

After making the new roof, it is time to finish the body side. This is how the side looks at the mo-

ment.

Despite of modifying the Loft feature, I could not create the surface using just one Loft. So the sur-

face was made in two parts, as is shown in the pictures below.


14.12.12 111

This is how the model looks:

5.6.4 Phase 3

This is how the model looks in the side-view:

The highlighted curves in the picture above were modified in order to get a better shape:


14.12.12 112

Now that the model shape has been finished, it is time to define the gaps where the different doors

will be placed (trunk, driver-, motor- and battery access).

Trunk

For making the trunk the procedure was quite simple. I just projected the edges of the part of the

chassis part belonging to the trunk to the body surface. The intersection between the body surface

and the newly generated surface will be the boundaries of the trunk gap (left picture).

These 3D curves were made using the Intersection Curve command (center picture).

Image 114: The final model.

Image 115: Trunk creation.


14.12.12 113

Once the trunk door was defined, it was time to make the trunk hollow. This is also quite simple. It

was done by trimming the body using the new surface. For that purpose, first the surface was split

into two parts (the part that has to be removed and the one that has to be kept). So the Split com-

mand was used, using as a splitting tool the trunk door boundaries.

Once the body surface was split as required, the split surfaces were deleted.

To create the inside of the trunk, it was necessary to trim the surplus surface of the last surface

made. This was done using the same “Split-Delete face” system used efore, using as a splitting tool

the body surface. The result can be seen in the right picture above.

Images 116: Inside trunk creation


14.12.12 114

Doors

For creating the doors holes, the procedure is quite similar to the one used for making the trunk.

First of all, the door shape was drawn in a 2D sketch taking in mind the chassis shape and the compe-

tition rules. After that, the sketch was extruded as a surface for splitting and trimming the different

surfaces later, in order to create the door gap.

Finally, the surfaces were trimmed giving the result below:

Chassis

side view

Door shape


14.12.12 115

Access to the engine and batteries

To provide access to the engine and batteries so that the race officials can check them, adding a new

door in the body is required.

The procedure was exactly the same as with the driver door. That is: making the sketch of the shape,

and then extruding the sketch as a surface, which will be the cutting tool.

5.6.5 Conclusion

As a conclusion, working in the bodywork has improved my skills in surface modeling a lot. I never

worked with surface modeling, so it was a big challenge for me. As can be seen through the whole

report, it has been a continuous going backwards and forwards in order to get the final model. Hav-

ing errors, fixing them, once it seems the model it is ok more errors were found. Despite having spent

a lot of time in developing this model, it has been worth it.

Another thing that I discovered is that it is not so easy working with surfaces in Inventor, so probably

the next time I have to do surface modeling I will use a different software programme.


14.12.12 116

6. Conclusion

General

Is it possible for our group to design the mechanical aspects of the urban concept vehicle which has

an efficiency of 280 km/kWh before the project deadline according to the competition rules?

We have throughout our project maintained the highest goal as efficiency. In doing so, we have in

every task strived to cut weight whilst maintaining strength and stiffness. We have designed systems

in order to complement one another and work together. On paper, we are confident that our vehicle

will perform without failure in all mechanical aspect whilst maintaining the highest efficiency possi-

ble. The actual efficiency is dependent upon many external factors outside of our control, such as

weather, track design, driver ability and many other unforeseen problems.

How do we organise our work tasks efficiently in order to meet the purposes of the project by the

project deadline?

From very early on in the project we divided ourselves in to two sub-groups that focused on different

aspects and systems of the vehicle. With the help of ‘Microsoft Project’ we adhered to the schedule

as best we could in order to meet miniature deadlines; this way we did not fall too far behind the

main schedule.

We also made sure to meet as a group (on average) twice a week, in order to get an idea of what

everyone was doing and what still needed to be done. There were no sub-managers for each group;

the dynamic of the groups worked well and they seemed to manage themselves concerning work

tasks.

How do we share our results and the results of the other groups between each other?

As mentioned previously, we had on average two group meetings per week; this was invaluable for

understanding at which point each group and each individual were at.

Facebook and Dropbox were invaluable tools for when we were not in meetings and working alone.

We were able to ask questions, share ideas and display results with ease and receive feedback, en-

couragement and advice from one another.

Information, data, results, questions and answers were shared in these meetings and using these

digital platforms, all working towards the common goal of completing the project with a good result

and on schedule.


Everything begins with research. Research allowed us to find multiple options to solve specific prob-

lems. These options were discussed at length during the project meetings – discussions which added

even more (and previously unexplored) options to the table. The combination of research,

knowledge from studies, discussions and feedback resulted in optimal choices concerning lightweight

materials and design for the vehicle.


14.12.12 117


Several options to connect the bodywork with the chassis have been explored, and their benefits and

disadvantages have been listed by Ana. This list will allow us to choose the best option(s) depending

on the final material and thickness of the bodywork, which will be solved at a later time. We do know

already that welding will not be an option, as the chassis is made of fibre composites.

Which materials will be used to reduce weight as much as possible without having a negative im-

pact on the strength and stiffness of the vehicle?

The main materials used in the vehicle are carbon fibre and flax fibre composites in a special sand-

wich structure combined with balsawood for extra support and stiffness, and several grades of alu-

minium depending on the purpose of the parts.


Obviously the driver requires the entire safety outfit as described by Ana, and the driver must also

have access to the on-board fire extinguisher. The roll cage made by Michiel is a critical component

in the safety of the driver and will be thoroughly tested during and after fabrication. The seat and

seatbelt system selected by Ioana come from well-established providers of safety equipment for

racing purposes.

Shell Eco-Marathon: design of brakes, steering system and wheels; group 3

How to select an appropriate brake system?

The key issue was weight, and we had to ask ourselves two questions in this order: “What is the

lightest possi le solution?” and “Does it have enough stopping power?” After sifting through the

options, we agreed that the lightest solution was a mountain bike braking system, which has more

than sufficient stopping power for our purposes. All other options, such as brakes designed for mo-

peds, go-karsts etc. were deemed unsuitable; even though they have more stopping power, they are

by far too heavy.

How to design an appropriate steering system?

With steering, control is equally as important as the weight of the combined components. The light-

est solution turned out not to be the best, as it is a possibility that the quality of steering would have

been very poor. We did not want to gamble in this area in order to shed a few kilograms of weight! It

was decided to use a tried and tested rack and pinion system with professionally manufactured com-

ponents; the extra weight is a cost worth paying for the quality of steering.

How do we integrate these systems into our vehicle?

We had to design many custom parts in order to integrate these different systems. Much time was

used in in doing so, even though the rack & pinion steering as well as the mountain biking braking

systems were pre-manufactured and were ‘ready to use’. The parts included steering rackets, rake

calliper mounts, support arms, a pedal, a pedal mount, fastenings etc. This design process was all for

the purpose of designing our vehicle to run smoothly, efficiently and without failure.


14.12.12 118

How to design and select viable wheels for the vehicle?

Once again, a key issue was weight. Once it was decided that the front and rear wheels would be

different (as the rear wheels would contain hub motors that will drive the vehicle), we could begin

our search. Most importantly, we had to find wheels within the dimensions given in the Shell Eco

Marathon rules. After a lot of searching, we found a type of wheel that was suitable from the field of

‘pit iking’. From there, it was just a matter of finding one which was light and tough enough for our

purposes.

The rear wheels were slightly different, in that we would first need to select a hub motor and then

design a wheel rim around it, as other pre-assembled hub motor wheels that we found were not

suitable for our purposes.

Which materials will be used to reduce weight as much as possible without a negative impact on

the strength and stiffness of the vehicle?

The main materials we will use within group 3 is Aluminium 6061-T6 (due to its high strength to

weight ratio and ease of availability) and varying grades of steel dependant on the purpose for which

they are intended.

Shell Eco-Marathon: design of the chassis, bodywork and safety equipment; group 4


Everything begins with research. Research allowed us to find multiple options to solve specific prob-

lems. These options were discussed at length during the project meetings – discussions which added

even more (and previously unexplored) options to the table. The combination of research,

knowledge from studies, discussions and feedback resulted in optimal choices concerning lightweight

materials and design for the vehicle.


Several options to connect the bodywork with the chassis have been explored, and their benefits and

disadvantages have been listed by Ana. This list will allow us to choose the best option(s) depending

on the final material and thickness of the bodywork, which will be solved at a later time. We do know

already that welding will not be an option, as the chassis is made of fibre composites.

Which materials will be used to reduce weight as much as possible without having a negative im-

pact on the strength and stiffness of the vehicle?

The main materials used in the vehicle are carbon fibre and flax fibre composites in a special sand-

wich structure combined with balsawood for extra support and stiffness, and several grades of alu-

minium depending on the purpose of the parts.


Obviously the driver requires the entire safety outfit as described by Ana, and the driver must also

have access to the on-board fire extinguisher. The roll cage made by Michiel is a critical component

in the safety of the driver and will be thoroughly tested during and after fabrication. The seat and

seatbelt system selected by Ioana come from well-established providers of safety equipment for

racing purposes.


14.12.12 119

7. Further work Due mainly to project structure (assuming a spring semester completion), there have been tasks that

have been left for a later date. Time limitations have also played their part and have prevented us

from doing some tasks we would have otherwise wanted to complete this semester. These tasks are

as follows:

Sponsors:

Not enough time was available to make a determined effort for seeking sponsorship of the vehicle if

it were to be manufactured in the second semester. We also felt we had very little experience in this

area and require further assistance.

Part acquisition:

Left for the spring semester once the main design of the vehicle is complete.

Vehicle construction:

Left for the spring semester once design is complete and all parts acquired.

Motor selection:

Left for the spring semester, although some preliminary calculations have been made in this report

to gain an idea of what we will need to look for.

Battery selection:

Left for the spring semester once we select the motor.

Electrical systems:

Including windshield wiper, lights, horn, gauges, indicators and the engine control unit will be left for

the spring semester.

Wiring:

Left for the spring semester when all electrical components are selected.

Emergency shut-off:

Left for the spring semester.

Testing & tuning:

Left for the spring semester once the vehicle has been constructed.

Additional FEA:


Tow hook:

Time constraints prevented us from incorporating a tow hook in accordance with the competition

rules, as we would need to consider many different design factors whilst trying to include it. It has

been left for the spring semester.


14.12.12 120

Suspension:

More of a consideration whether or not to include suspension, as it is not compulsory. It will be de-

cided in the spring semester.

Aerodynamic simulation:

Left for the spring semester, once the final design of the body work is complete.

Energy recuperation:

Including solar panels and regenerative brakes. These concepts will be considered in the spring se-

mester as to whether they will benefit our vehicle.

Front wheel axle:

Due to time constraints, the final solution for attaching the front wheels to the steering brackets was

not met, although it should be a simple case of a threaded end shaft with some specific clips and

grooves; the details of which have not been examined. This will be done in the spring semester.

Race qualification:

We will wait to see once submitting our phase 2 registration information whether we have qualified

for the race.

Expert consultation:

Consult with experts about the roll cage size and construction and verify calculations.

Electrical systems selection:

We will leave the engine selection, engine control unit programming, battery installation, wiring etc.

for the spring semester.

How to divide the body for manufacturing:

An important issue that should be taken in mind is how the body it will be built. The body cannot be

built in one piece, because the price of the manufacturing process will be quite expensive. In order to

make easier and cheaper the manufacturing process, the solution took is splitting the body in differ-

ent parts and attach them later. We will consider this in the spring semester.

Body Material:

The choice of material is an important point in the bodywork. In this car, one of the most important

points is use the lightest material possible, always getting a balance with the stiffness. We will con-

sider this in the spring semester.

Attaching the doors to the body:


Attaching bodywork to the chassis:


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