EN0751 Interdisciplinary Engineering Project Shell Eco Marathon



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ACKNOWLEDGEMENTS


As a group we would like to take a moment to acknowledge the help and support received in the process of completing this project. We would like to thank the many companies who have provided supplies and insight to help us with this project. We would also like to thank Shell for processing our application, and the help they gave us both financial, and in their helpful tech videos. Dr Ulugbek Asimov oversaw the project and was instrumental in getting us both funding and recognition from the university. Dr Terence Liu was our groups’ personal tutor and offered much advice and help when we were struggling. Sayed Ebrahim and Richard Eke were volunteers on this project and their expertise and knowledge of their subject areas was invaluable to us in getting our ideas off the ground. Finally, thank you to the lab technical team for their constant help and work bringing our ideas to fruition.

ABSTRACT


This year, Northumbria University entered the Shell eco marathon contest for the first time in its history, aiming to take a vehicle from concept to track ready to compete over a period of 8-10 months. This is a project that required engineering application for the cars’ aero-dynamics design, simulation, testing and building as well as the commercial requirements such as acquiring funding, marketing, and project management.

This report details the work that was done on the vehicle power train by a team of five students working together to configure a small engine to run on ethanol fuel with the aid of electronic fuel injection and the final model integrated into the vehicle chassis. Details of the final results on the project, as well as significant milestones achieved through the duration of the task are documented as we continue. Some recommendations for future teams as to how to improve upon the results obtained and where to go next in improving the overall effectiveness of the vehicle are also discussed.


CONTENTS


ACKNOWLEDGEMENTS 1

ABSTRACT 1

CONTENTS 2

GLOSSARY 3

1.INTRODUCTION 3

2.AIMS AND OBJECTIVES 4

2.1Aims 4

2.2Objectives 4

3.TECHNICAL DETAILS 5

3.1Fuel Source 5

3.2Engine 5

3.3Clutch 6

3.4Electric Start 6

3.5EFI & ECU 7

3.6Fuel Tank 7

3.7Air tank 7

3.8Steering System 7

3.9Braking 8

3.10Exhaust 8

3.11Battery 8

3.12Body 9

4.PROJECT PLANNING 9

4.1Planning 9

4.2Communication 9

4.3Time Keeping 10

4.4Budget 10

5.PROJECT OUTCOMES 10

5.1Team Work 11

5.2Engine testing 11

5.3Powertrain system 11

6.DISCUSSION AND CONCLUSION 11

7.FUTURE WORK 12

8.REFERENCES 14

9.APPENDICES 15


GLOSSARY


C2H5OH Ethanol

CAN Controller Area Network

CNC Computer Numerical Control

CO2 Carbon Dioxide

ECM Engine Control Module

ECU Electrical Control Unit

EFI Electronic Fuel Injection

ICE Internal Combustion Engine

KPa Kilopascal

M Metre


Mph Miles per Hour

PSI Pound per square inch

PCI Peripheral Component Interconnect

PCM Powertrain Control Module

RPM Revolutions per Minute

SEM Shell Eco Marathon

US United States of America

  1. INTRODUCTION


With the depletion of fossil fuels, there is a high focus on the use of greener energy. Various industries are already in midst of applying changes. Our team has taken a specific interest in fuel source and efficiency, because we believe in the statement by Dr May Carter, (202020 Vision Plan, P52) “Investing in growing places, where people can live happy, healthy lives, and engaging communities in maintaining that investment, will benefit us all.” [1] In the US alone, transport is responsible for 27% of greenhouse gas emissions, thus changes are necessary to achieve a reduction in the amount of pollution caused by automotive emissions. [2] Two groups were selected to design and manufacture a vehicle with a goal of entering the Shell Eco Marathon, taking place at Olympic Park, London, in May 2017. The project was split into two sections, where each group has been assigned with the responsibility of completing a component of the car. For the purpose of this report, Group A will be used to identify the Power Train team, while Group B are responsible for the Chassis. For an automobile, a powertrain describes major parts of a vehicle that generate power and deliver it to the surface which can be either water, air, or land. Powertrain manufacturing for Engines includes multiple devices such as spark ignition, fuel injection, transmission, drive shaft, suspension, wheels etc. The power-train includes all of the car components used to convert saved (chemical, solar, nuclear, gravitational potential, etc.) energy into kinetic energy for propulsion purposes. The contents of this report detail the attempts of the group to both prepare and install a power train system into the chassis of a prototype vehicle (designed and built by Group B) to work alongside the other members of the team to enter a fully working vehicle at the London event in May 2017. It includes aspects of fuel usage, parts sourcing, difficulties in creating the system and future work for next years’ student team to build upon to improve the competitiveness of the vehicle.

There were a number of constraints to the project that could both hamper progress and assist to push the project in certain directions; primarily, the project budget of £10,000 was provided to be split between the body and powertrain development which had to be factored into the planning process; secondly certain processes and ideas would have to be passed by the university health and safety departments while all ordering had to be done though a university account. Most importantly, Shell’s rules had to be adhered to which dictated how the fuel could be added to the system, and how the car can be powered.


  1. AIMS AND OBJECTIVES





    1. Aims


  1. Convert an engine to run on Ethanol

  2. Build a working power train system for a single seat vehicle

  3. Tune engine and power train system to run as efficiently as possible

  4. Work with body development team to build SEM vehicle

  5. Compete at Shell eco marathon Europe

    1. Objectives


  1. Research is required to source out different engine and fuel types. Upon making selection, further research will be required to look into any possible modifications required.



  1. Each member of team has limited technical knowledge of vehicle manufacture, and thus everyone will need to learn what the powertrain entails, how it works and how it can be built.



  1. Upon achieving the first two aims, the team will modify the engine and develop the powertrain system, and test to see if the engine has enough power and endurance to run at a level capable of competing in the SEM event.



  1. The powertrain system needs to fit with the chassis and body of the vehicle, therefore both teams need to work together for decisions to be made in regards to the car’s dimension, specifications and components.



  1. Over a short period of 8-10 months, the team will have to work hard to research, design and manufacture a running vehicle. This must be done within SEM and university guidelines dictating both health and safety practices, budgeting and project timelines. All rules must be adhered to prevent disqualification from the event.

  1. TECHNICAL DETAILS



    1. Fuel Source


Petrol engines emit large amounts of pollutant gases, having an adverse effect on the environment. A green alternative to petrol is beneficial for this project. Multiple fuel types and propulsion systems were researched and a decision made to run the vehicle on Bioethanol. Ethanol or ethyl alcohol (C2H5OH) is a clear colourless liquid which is biodegradable, low in toxicity and causes little environmental pollution if spilt. Ethanol burns to produce carbon dioxide and water. [3] Some of the emissions will be reduced as the energy crops absorb the CO2 they emit while growing. Ethanol is biodegradable and far less toxic than fossil fuels. In addition, using bioethanol in older engines can help reduce the amount of carbon monoxide produced by the vehicle thus improving air quality. [4] A key limitation is that ethanol has a lower energy per unit volume- 34% less than petrol. Since ethanol has a higher octane rating, the engine can be made more efficient by raising its compression ratio. [5] The engine will require modification in order to run on this type of fuel. This renewable energy source and could potentially play a key part in the future of on and off-road machinery fuelling, hence it’s selection as the fuel for the eco car being produced. See appendix for detailed information relating to ethanol.

    1. Engine


The engine will need to reach speeds of 20mph, and be reliable enough to be switched on and off repeatedly during the race as a fuel saving technique. These properties are typically found in engines used in appliances such as garden lawn mowers and water pumps, all of which are capable of delivering a reliable, easy starting, and fuel-efficient performance on a regular basis. A cautious approach to engine selection was in place, due to this being the first time for the university to participate in SEM and available funding, the decision finally led to the purchase of Honda GXH50 due to the fact that It has previously been used successfully by other universities for the competition and based on reviews, appears to be a very reliable and fuel efficient ICE. The power graphs provided by Honda for the engines compared can be seen in the Appendices.

The engine was initially chosen with a belief that it would be easy to work with but after further research it was discovered that there were two major factors of concern:



  • The length of the crankshaft necessitated that only one type of clutch could be used

  • As per shell rules, the carburettor and pull start had to be replaced with an Electronic fuel injection kit and electric starter motor

    1. Clutch


A chain-saw style clutch was used, as it was the only type of clutch that could fit on the engines short crank shaft. This was designed and built by the company “Max Torque engines” [6] (See appendix 4). A 12 tooth sprocket has been drilled and tapped into the crank, connected by a chain to a 24 tooth on the drive shaft, giving a 2 to 1 reduction in engine RPM. This is held in place on a mounting plate, on which the engine would sit using 2 self-aligning bearings, giving great flexibility in the clutch location. The clutch itself was a small centrifugal clutch which would engage at roughly half the max engine revs, around 4500rpm. More chain would then connect this to the rear wheel sprocket. Initially the use of a gearbox was required however, following from the information provided by max torque the decision was made to remove a gear box entirely, as the reduction on the clutch would be sufficient. The engine crank shaft has a small key machined and placed on it to ensure that the sprocket was held in place.

The clutch would drive the rear wheel by connecting to a rear sprocket by a number 35 chain, though for future versions a rubber tooth belt would appear to be much lighter and less likely to slip off, improving the use of the vehicle. Calculations had to be carried out to determine the size of this rear sprocket, and it was decided that a 105 tooth sprocket was required.


    1. Electric Start


The selected engine was initially fitted with a pull start motor, but for the purpose of the competition an electric start motor will need to be mounted. The smallest size available was purchased, which was designed for a larger Engine in the form of a GX160 model, thus requiring further modification to match specifications due to the motor’s size and weight. The flywheel was 3.5kg, measuring 175mm in diameter, with 86 teeth originally, however, once modified the weight was reduced by over 2.5kg.

The new flywheel was thin enough to mount directly onto the engine crankshaft unlike the original, however, further alterations to the engine are still required. Reducing the weight will improve the efficiency of the car as a lighter load will result in less fuel being burnt to achieve propulsion, and as such less emissions will be produced- having a less detrimental effect on the environment.


    1. EFI & ECU


As stated in SEM 2017 official rules (Article 62, page 35), “Engines with carburettors are not allowed. Fuel injection is mandatory.” [7] An EFI kit contains a 28mm throttle to replace the carburettor, together with fuel and air lines. An ECU, used to control the ICE with the use of sensors, is attached to various EFI components. Each controller has the capability of controlling temperature, pressure and other variables, which is particularly important for modifications made to the engine, as control of the air and fuel pressure is essential to running ethanol in a gasoline engine.

    1. Fuel Tank


Shell will provide a 100ml glass fuel tank due to measurement purposes. The engine comes with a fuel tank already attached, therefore further modifications are made to allow an alternative fuel tank to sit in its place.

    1. Air tank


After a great deal of research, it was found that a two-litre plastic soda bottle can withstand pressures of up to 1,034 KPa or 150 PSI. [8] This ties in with SEM 2017 official rules (Article 59, page 34) “Pressurisation is done by means of a translucent compressed air bottle fitted with a safety valve set to 5 bars maximum.”[7] This would not only fit the vehicles in terms of space used, but also be able to take the pressure of the air it needed to withstand. It also re-uses old plastic materials- meaning they can be saved from landfill and reduce environmental effects, as well as being very lightweight to help improve vehicle fuel burning.

    1. Steering System


The vehicle runs on three wheels, two in the front and one in the back, known as a ‘tadpole’ or ‘reverse trike’. [6] The choice for this model was based on better aerodynamics, so as to fit in line with the overall ‘teardrop’ shape body, while also taking into consideration improved braking capabilities over those designed whereby the vehicle has only one front wheel and two back. One point of which to be wary is that compared to a four-wheeled car, the three-wheeler is more susceptible to over-steer.

With the current wheelbase at 1.6m and front track at 0.52m from wheel to wheel, the inward angle of the steer arms with the steering rods in front of the axle centreline is approximately 9.23 degrees, allowing a turning radius of 6m. A maximum turning radius of 8m is allowed, therefore, on top of research, CAD drawings, and CAD assembly, calculations were carried out to validate the expected outcome of building a working steering system with the various components, ensuring all dimensions had been accurately noted.



The stub axle, made up of wheel bearings, has the job of supporting one of the front wheels, using a manner of bolts, joints and kingpins to connect the front wheels with the back, while simultaneously coming together at the steering column, thus providing the driver with the means to turn wheels in one motion without the need to separately control each wheel individually.

Figure 3: Rear Axle

The stub axle and steering knuckle arms need to be manufactured to fit. For this job to be completed correctly, a CNC milling machine is needed to manufacture these components. This has resulted in the need to out-source the work to a 3rd party company.

To complete the steering assembly, components need to be connected to one another. This is achieved by using a sprocket, comprising of a metal disk with teeth around it, comfortably able to hold a chain, which is linked to a second sprocket attached to the engine.


    1. Braking


The Vehicle must maintain an average of 15mph. As such, a large braking force is not needed to bring the vehicle to a halt. As specified in the SEM 2017 official rules (Article 43, page 21), “The vehicle will be placed on an incline with a 20 percent slope with the Driver inside. The brakes will be activated each in turn. Each system alone must keep the vehicle immobile.”[7] Shimano Deore M615 brake are high end bicycle brakes. With one attached to each of the wheels, the force should be sufficient to hold it at a standstill.

    1. Exhaust


The engine came with a small noise reducing exhaust but this had to be rotated to allow the electric starter to be mounted. A new exhaust system was designed by 3rd year project student Richard Eke and was worked on in conjunction with the main powertrain system.

    1. Battery


Available in house, a 12V Lead acid battery, 35 Ah, weighing 12kg meets requirements of the EFI and has sufficient charge to run this vehicle during the event. A Lighter lithium-ion alternative is available if budget allows for it. Again this reduction in weight will help to improve the overall efficiency of the car, and the 35Ah stores enough charge to sufficiently run for the full engine drive period without needing to recharge or implement an alternator- reducing the electricity usage of the vehicle.

    1. Body


All body and chassis work was completed by group B, and as such will only be touched upon briefly here. A tear drop shape was required for the vehicle due to its aerodynamic properties [9] and the need to reduce drag to as low as possible as it is heavily affected by the frontal area of the vehicle.[10] The chassis was manufactured externally due to the difficulty associated with aluminium welding. The body was to be manufactured externally as well, however the price was deemed to be too high, and as such an in house foam mould was created which, when completed, will be wrapped in either fibreglass or carbon fibre depending on available funds. This mould can then be kept in the lab and re-used in the following years for other university teams, saving time on projects but also on materials cost and tooling.

  1. PROJECT PLANNING



    1. Planning


A successful project is based on excellent planning skills, and monitoring two groups each containing five members, required constant communication and frequent weekly meetings. A team manager was allocated, partially due to the need for someone to oversee every aspect of the project, and as a requirement for SEM.

The team managers’ job included setting out a list of tasks to be completed, creating a schedule by when things were to be completed and, most importantly, looking ahead for future obstacles for which an alternative plan may be required, amongst other such tasks.

A Gantt chart was put together, where each individual was provided with certain tasks, showing dates by when their tasks were to be completed.

Each week a meeting was held, the team was able to discuss the progress of the week, and look to see what was required in the coming week while discussing ideas of any further ideas relating to the project. A second weekly meeting was held just for group A, to discuss more in depth developments on the powertrain and set a more technical task list.


    1. Communication


A big key in a successful project is communication. When someone stops communicating and updating others on how their task is panning out, subsequent work can be impacted as it requires a prior task to be completed before continuing. Group A often stayed up to date with their schedule, as through communication spoke to each other about what needed to be done, and ensured all involved were able and willing to carry out jobs that needed to be done. This was completed through a number of mediums, including the meetings as touched upon in 4.1, email and mobile communication (calls, group messages), and social media through the team page, almost allowing a group meeting to run continuously. Lastly, a google drive for the team was created for media and file sharing, ensuring access to all parts of the project were available to any one team member at any time.

    1. Time Keeping


Interruptions whilst in the midst of a meeting can be incredibly distracting when important topics are being discussed. Furthermore, the meetings often follow a certain schedule, therefore if certain people are not there in time to provide their update, it causes a knock on effect. Time keeping was very much encouraged within the team, so as to allow everyone to continue with work at a time agreed by all. Regular email invites were sent for meetings to ensure everyone knew well in advance, and could plan their daily activities accordingly. Each meeting had a pre-set agenda and attendance and minutes were taken to ensure a record of all that was discussed were available on the google drive to avoid confusion.

    1. Budget


This project required a lot of funding for the purpose of manufacturing a car.

The university part provided the budget, with the rest coming upon successfully being accepted by SEM to compete- the team was granted additional funding toward the manufacture of the vehicle.

One person in the team was appointed the finance manager, who gave rough allocation of funds for each aspect of the vehicle, i.e. bodywork, chassis, powertrain, etc.

An excel file was set up, showing what needed to be ordered, approximate cost of each component, and remaining budget available for additional items.




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