Dissertation Hardcopy (My Version)

University of Brighton

Formula Student

Final Year Project

Christopher Blackman

XE 337

Supervised by:

Dr Nicolas Miché, Dr Steven Begg and Dr Khizer Saeed

20/04/2015

Final year report submitted in partial fulfilment of the requirements for

the degree of Bsc Honours in Mechanical & Manufacturing Engineering (Top-up)

Final Year Project XE337 Christopher Blackman

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Disclaimer

I hereby certify that the attached report is my own work except where otherwise indicated.

I have identified my sources of information; in particular I have put in quotation marks any

passages that have been quoted word-for-word, and identified their origins.

Print

CHRISTOPHER BLACKMAN

Signed

Christopher Blackman

Date

20th

April 2015


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Electronic copy of dissertation

Please find included an electronic copy of this Final Year Formula Student Project dissertation.


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Abstract

The findings of this report conclude that from the research and evaluation of existing Final Drive

systems, employed by the teams that currently enter the Formula Student Event an effective Final

Drive system in the form of a chain and sprocket set up has been derived. Through further critical

evaluations and designs in compliance with the technical regulations laid out by the Institute of

Mechanical Engineers (IMECHE). Along with requirements of other areas such as the gear ratios

and the differential which directly relate to the Final Drive package.

The findings also further concluded that the design can either be manufactured internally or provide

an option for the parts to be manufactured outside of the university. The conclusions also state that

the final designs may be subject to minor alterations for positioning purposes when the assembly

stages take place.


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Contents

Disclaimer Page 2

Electronic copy of dissertation Page 3

Abstract Page 4

Introduction Page 7

Project Management

1.1 Overall project management Page 8

1.2 Individual project management Page 10

Research

1.3 Formula Student Technical Regulations 2015 - 2016 Page 12

1.4 Initial research Page 14

1.5 Evaluation from 2014 Formula Student entries Page 17

1.6 Single 520 Chain Page 18

1.7 Spur Gear Page 19

1.8 Helical Gear Page 20

1.9 Final Drive decision matrix Page 21

Research Conclusions Page 24

Design

1.10 Initial design ideas Page 26

1.11 Design ideas decision matrix Page 27

1.12 Information from other team members Page 29

1.13 Design calculations Page 30

1.14 Final design Page 32

1.15 Shatter Guard design Page 33


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Conclusion Page 34

Appendices Page 35

Bibliography Page 49


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Introduction

The information documented in this report is based upon the Formula Student race car event

conducted by the Institute of Mechanical Engineers (IMECHE), looking at the Final Drive section

of the car.

Objectives:

Due to the size of this project the tasks were divided into seven different work packages. The area

that I was assigned to was the drivetrain package with the responsibility of the development of the

Final Drive system. So my individual objective is as follows:

Individual objective is to: Evaluate, develop and if possible produce an effective and

efficient Final Drive system that will be combined with other components to produce a

complete, effective drivetrain package which will be used on the university’s Formula

Student Car.

Limitations:

The limitations that I have encountered on this project are that the designs are constrained by the

Formula Student Technical Regulations 2015 – 2016.

Other limitations have been through the process of how my design will operate in relation to the

other components that it will be assembled to or work in conjunction with.

Document Summary:

This document covers the initial research into the Final Drive system. By evaluating the systems

used by the current entries, taking the recommendations of the research, to develop initial designs

and further evaluate the final design that will be taken forward to the manufacturing and assembly

stages of the project.


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Project Management

1.1 Overall project management

Throughout the duration of this project the management schedule was controlled by the use

of Gantt charts and a weekly progress log.

The initial Gantt chart that was included in the project proposal (Appendix A) for our work

package was only used as a reference point for our group. Upon feedback for improvements

of our Gantt chart we informed the supervisors that we were in the process of deriving

individual Gantt charts tailored to our individual tasks and requirements for this project.

Individual Project Gantt charts can be found in the appendices, Appendix A - D.

The use of the progress log was split into two sections. These two sections consisted of a

work packages feedback session and an individual feedback session with the assigned

project supervisors.

The whole team session consisted of all seven work packages involved in the project with a

different team member being nominated as the team’s project lead. The leads were

responsible for the feedback of their group’s progress to the other project teams each week,

by highlighting their current progress and where their team will be heading in the future.

The responsibility involved in the progress log was to ensure that the documentation was up

to date. This was then fed back to the other members on the project and questions that arose

either from the supervisor or the other work packages were answered.

As stated, the project lead rotated at every weekly review session and it was my

responsibility to be project lead on five occasions throughout the duration this project.

During this session after all feedback has been given, the opportunity arose to communicate

with the other teams freely to either obtain a better understanding of their progress for

personal knowledge, or to obtain information which would be relevant to their particular

part of the project.


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The session was also the opportunity to speak with our assigned supervisor, Dr Khizer

Saeed, about our current progress and problems that we may have encountered. This

meeting also highlighted the tasks that our supervisor wished to see the following week to

keep the project focused and on track with our completion deadlines.


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1.2 Individual project management

Individual project management was monitored through a specifically derived Gantt chart

for my section of the drivetrain work package. This Gantt chart was accessible for my

fellow team members to review throughout the project.

This not only outlined my own objectives for the project, but it also combined the tasks

which had to be completed as a team, such as the progress review presentation and the

poster display.

Throughout this project my Gantt chart undertook amendments on numerous occasions.

These amendments included factoring in additional tasks as the project progressed and the

alteration to the existing tasks to ensure continual progression. Any extra available time

was to be factored in on tasks that could be considered a problem and delay the progress of

the project. These amendments can be seen in the appendices (Appendix B - D).

During the project, one task was highlighted as a concern as it was started a week later than

the Gantt chart allowed. The task in question was the initial development of conceptual

designs. This issue was recorded onto our progress log and my Gantt chart was amended

accordingly. The setback for this task was a direct result of the accessibility to the

computers on which the relevant Computer Aided Design software "Solidworks" was

installed. Once access was gained to the computers this issue was resolved and did not

develop into a further problem causing delay to the remainder of the project.

The change in the Gantt chart for this task can be found in the appendices (Appendix B -

C).

Improvements to the project management:

An area for improvement would be the communication within our own team. Although we

delivered the group tasks and produced our individual projects, combining them to make an

effective drivetrain system for the Formula Student project, there were times that the

communication lapsed.


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The areas where this lapsed were in the preparation of tasks such as the poster and

presentation reviews. Another area was in obtaining the required information, giving the

other members sufficient time to collate the information so that they could pass it on, rather

than having to rush to prevent the team’s objective from falling behind.

Others areas for improvement come down to effective time planning as there were minor

delays in obtaining information from other work packages. This impacted on the progress

for the design of the differential which in turn delayed my progress for the Final Drive.

The area where this impacted most was on the completion of my final design. Whilst

waiting for the other work packages to be completed, I made design assumptions which

were amended where necessary.

One area on the project management that worked well was the use of the progress log. This

had to be reported to the supervisors with other work packages involved in the project, as

this helped to keep the project focused and on track to achieve our own objectives. This log

also helped to bring the different work packages together so there was more involvement

across the whole project and not just in certain areas.

Minor monitoring improvements could have been made to our work packages to ensure that

the logs were completed and up to date as we approached the end of the project.


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Research

1.3 Formula Student Technical Regulations 2015 - 2016 [1]

(Part T General Technical Requirements, Article 8 - Transmission and Drive)

The most important stage that had to be addressed in this type of project were the regulations that

had to be complied with in order to produce an effective and competitive car.

By using the supplied reference document on the Formula Student Technical Regulations 2015-

2016, I conducted a search of the regulations to determine those that had the most relevance to the

Final Drive system.

This search leads me to Article 8 Transmission and Drive

The points from this section of the regulations are listed below, they detail what parameters must be

adhered to when the design and manufacturing stages take place.

T8.3 Transmission and Drive - Any transmission and drivetrain may be used.

T8.4 Drive Train Shields and Guards T8.4.1 Exposed high-speed Final Drivetrain

equipment such as Continuously Variable Transmissions (CVTs), sprockets, gears,

pulleys, torque converters, clutches, belt drives, clutch drives and electric motors,

must be fitted with scatter shields in case of failure. The Final Drivetrain shield must

cover the chain or belt from the drive sprocket to the driven sprocket/chain

wheel/belt or pulley. The Final Drivetrain shield must start and end parallel to the

lowest point of the chain wheel/belt/pulley. (See figure below) Body panels or other

existing covers are not acceptable unless constructed from approved materials per

T8.4.3 or T8.4.4.

NOTE: If equipped, the engine drive sprocket cover may be used as part of the scatter

shield system.

Comment: Scatter shields are intended to contain drivetrain parts which might separate from

the car.

T8.4.2 Perforated material may not be used for the construction of scatter shields.


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T8.4.3 Chain Drive - Scatter shields for chains must be made of at least 2.66 mm (0.105

inch) steel (no alternatives are allowed), and have a minimum width equal to three

(3) times the width of the chain..The guard must be centred on the centre line of the

chain and remain aligned with the chain under all conditions.

T8.4.4 Non-metallic Belt Drive - Scatter shields for belts must be made from at least 3.0 mm

(0.120 inch) Aluminium Alloy 6061-T6, and have a minimum width that is equal to

1.7 times the width of the belt. The guard must be centred on the centre line of the

belt and remain aligned with the belt under all conditions.

T8.4.5 Attachment Fasteners - All fasteners attaching scatter shields and guards must be a

minimum 6mm Metric Grade 8.8 (1/4 inch SAE Grade 5) or stronger.

T8.4.6 Finger Guards – Finger guards are required to cover any drivetrain parts that spin

while the car is stationary with the engine running. Finger guards may be made of

lighter material, sufficient to resist finger forces. Mesh or perforated material may

be used but must prevent the passage of a 12 mm (1/2 inch) diameter object through

the guard.

Comment: Finger guards are intended to prevent finger intrusion into rotating equipment while

the vehicle is at rest

This image was included in the regulations to illustrate how the shatter guard must cover the

sprockets on the system and what reference points it is taken from.


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1.4 Initial research

The initial stage of this project's research, after the focus on the Formula Student technical

regulations, was to investigate what the Final Drive system is. This was done to obtain a sufficient

understanding of this area and enable an effective delivery of the system for its required purpose.

The following statements were found when researching into the Final Drive system which looks at

the general overview and the types of drive that exist:

Straight Axel Drive

Pinion Gear Drive

Planetary Gear Drive

General overview of Final Drive system:

Power is transferred from the differential to the final work point. This power is passed through the

Final Drive.

On wheeled machines the Final Drive provides the final reduction in speed and increases the torque

used to drive the wheels. The location of the Final Drive can be found mounted near the rear driving

wheels on most machines.

With machines that have no driving wheels the Final Drive system carries the power through to

tiller tines by means of reducing the speed along with reducing the stress in the transmission and

other power-train components.


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Straight Axel Drive Systems

The Straight Axel Drive contains a rigid shaft connected to the differential by splines and supported

on the other end by a tapered bearing or roller bearing. The drive wheels receive their power from

the differential. For each revolution of the differential the axel shaft and wheels make one

revolution.

If a machines final work point uses implements such as tines, blades or an auger instead of drive

wheels the shaft will connect directly to the implement. Straight Axel Drives are simple in

construction and relatively easy to maintain and repair.

[2]


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Pinion Gear Drive systems

In Pinion Gear drive systems, the power is transferred to the drive wheels through pinion gears

connected directly to a differential.

The pinion gears then mesh to a larger Final Drive gear that drives the axel.

A pinion gear will be completely enclosed within a differential case.

[3]

Planetary Gear Drive

Planetary Gear Drive systems are more compact than the

Pinion Gear Drive system.

Planetary gear drives are very strong and durable because they

spread the applied load over several gears.

The power is then transmitted from the differential through a

final drive shaft to the sun gear.

As the sun gear turns it meshes with the planet pinion gears.

These are held in place by a planet pinion carrier which is

attached to the rear axle shaft. As the sun gear and planet pinions turn they turn the carrier and the

rear axle shaft.

[4]


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1.5 Evaluation from 2014 Formula Student entries

In order to determine the best Final Drive mechanism an evaluation of the type of mechanism used

on previous Formula Student entries was necessary.

The Formula Student 2014 event programme, [5] which was sourced from the race car engineering

website, contained all the key information on the Class One and Class Two entries. This proved to

be helpful in determining the best design to carry forward.

The evaluation table of the different drive mechanisms can be found in the appendices (Appendix

E).

The results of the evaluation of the 123 overall entries split across the Class One and Class Two

divisions are as follows:

Overall Conclusions:

The overall conclusions from the evaluation table showed that from the 123 entries across both

divisions, seven of the entries used a combination of either chain and gear systems or used two

different types of gearing for the Final Drive.

The most common Final Drive system that was used throughout the teams in this event was that of

the Single 520 Chain. With the gearing systems that were used, the most common format was that

of a Spur Gear followed by the Planetary Gear system.

Class 1 Entries:

From the entries in this division, one team who used the Single 520 Chain for their Final Drive

combined this with the use of a Planetary Gear system. As for the gear systems used three teams

used a combination of the Spur Gear and the Planetary Gear.

Class 2 Entries:

One of the entries that used a Helical Gear combined this with the use of a Planetary Gear.


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1.6 Single 520 Chain

Following the research evaluation of the different drive mechanisms used by the Formula Student

Entries in the 2014 event the most popular mechanism was the Single 520 Chain.

After conducting research into the Single 520 Chain, I found information on the Vortex 520 steel

sprocket chain kit. [6] So the design criteria for this product was used as a reference and is listed

below:

Vortex Front Sprocket 520: This is made from the highest quality steel and is case

hardened and on most applications has drilled

lightening holes.

Vortex Rear Steel Sprocket 520: The rear sprocket is laser cut from carbon steel with

the aim to provide extended chain wheel life over an

aluminium manufactured sprocket.

The rear sprocket is electroplated satin black to help

against corrosion resistance. The sprockets teeth are

hardened for increase durability and deeply cupped for

weight reduction. The application is both applicable

for street and race usage.

D.I.D 520 ZVMX Series X-Ring Gold Chain (100 Links):

This particular type of chain has increased rigidity which provides for a better power transfer and

greater resistance towards stretching under workloads. The design and overall improved

performance of the chain means that it meets the requirements for machines bigger than 1000cc.

The average tensile strength of this particular chain

in 8,745 Pounds. In relation to the product weight,

for every 100 links it weighs 3.59 pounds. The

master link is a rivet style design.

[7]


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1.7 Spur Gear

Following the Single 520 Chain the more commonly used gear system was the Spur Gear. When

research was conducted into the Spur Gear the results were as follows:

From all the gearing systems the Spur Gear is the most common type that is used today. The gear is

mounted on parallel shafts and the gears themselves have straightened teeth. The teeth are

straightened because it allows for design simplicity and efficiency on low power and speed

applications.

In selected scenarios many of these gears will be used at any one time to create larger gear

reductions.

Due to the design simplicity of this gear it can be found in many applications such as washing

machines and electric screwdrivers but not many will be applied in cars.

The reason why this type of gear will rarely be found applied in cars is because the gear generates

too much noise when in operation. The increased noise level is a created every time the gear teeth

engage one another.

Alongside the noise level, the levels of stress applied though the gear teeth also increases, making

this design an inappropriate system to use in car applications.

A way to reduce the noise and stress levels within this gear system is to us a Helical Gear. The

Helical Gear system is commonly applied and located within cars.

[8]


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1.8 Helical Gear

As mentioned on the previous page the Helical Gear is the type of gear system that will be

commonly found applied in car transmissions.

The reason why this preferred gearing system is used in cars is because of the reduced noise levels

and the difference in the way the stresses are applied to the gear.

The reason for the differences in the stress and noise levels compared against the Spur Gear is

because on the Helical Gear the teeth are design and manufactured at an angle, this helps when the

two gears engage each other as the initial point of contact is made at one end of the gear and then

gradually spread across the remainder until both of the teeth are fully engaged making an overall

smoother quieter operation. Unlike the Spur Gear in which full contact is made across the gear

immediately applying higher stress levels.

The angled teeth on this gear design create a thrust load when they mesh to each other. Any devices

that use the Helical Gear system contain bearings which are capable of supporting the applied thrust

load. Another key advantage to the gear’s teeth is that if the angle of the teeth is correct they can be

mounted onto perpendicular shafts adjusting their rotational angle by 90 degrees.

This gear can be found in applications where the requirements for the power and speed are higher to

allow for a smoother operation such as car gearboxes and machine tools.

[9]


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1.9 Final Drive decision matrix

This decision matrix was used to evaluate the three popular Final Drive mechanisms that were

derived from the 2014 Formula Student entries (See page 40 and Appendix F respectively).

The three popular Final Drive mechanisms’ that are used in the matrix are:

1. Single 520 Chain

2. Spur Gear

3. Helical Gear

Detailed information on these three Final Drive designs can be found on pages 18 - 20.

The scoring for the decision matrix is based upon a one to five scale with the lowest overall score

being determined to be the most effective. The scoring criteria can be seen below:

1) Very Low: Designs that scored this are considered to be the best against the relevant

criteria

2) Low: This score is given to designs to which have potential to be the best but have

some factors making the design slightly complex.

3) Average: Designs that score this are considered to be neither the best nor

the worst, although in order to be the best modifications may be

required to the design on other surrounding parts.

4) High: This is scored on designs that are beginning to have an overall

effect towards the cars performance (Such as weight or the

complexity of their design).

5) Very High: This score reflects that the design against the relevant

criteria is to complex or has major implications towards the cars

performance and handling.


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The criteria which was used in the decision matrix to determine the most effective Final Drive

system was based upon:

Formula Student regulation requirements

Design effecting the performance & handling of the car

The criteria listed below was used to evaluate the three Final Drive mechanisms against each other:

1) Design Simplicity: How easy is the manufacture and

assembly of the drive system.

2) Accessibility for Maintenance: Is the design easily accessible for

maintenance requirements.

3) Efficiency: How efficient is the drive mechanism.

4) Is the use of a Shatter Guard required: This is a Formula Student regulation

for chain/belt driven mechanisms.

5) Does the mechanism require to be enclosed in a housing:

This is applicable to designs that are gear

based, as they are required to be enclosed in

housing as they use lubricants such as oil.

6) Is the drive design going to have an effect on the weight of the car:

This will be subject to the chosen design as the

car wants to be a light as possible for speed.

From reviewing the Decision Matrix (Appendix F) it is clear to see that the Final Drive method

which scored the lowest (10 points) and subsequently will be continued with to produce a Final

Drive design is the Single 520 Chain.


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The Spur Gear was the next with a score of 17. The Helical Gear had the overall highest score of

20.

The areas in the matrix where the two gear driven methods scored the highest were in the following:

1) Accessibility for maintenance

2) Does the mechanism require to be enclosed in a housing

3) Is the design going to have an effect on the weight of the car

The listed criteria where the two gear driven systems scored highly in the matrix was because they

would have to be enclosed into a housing unit making difficult access for quick maintenance

purposes.

The factor of the gears having to be enclosed in a housing unit then adds to the cars weight. This

additional weight of the gears would affect the overall weight distribution of the car and

subsequently have a damaging impact upon the handling and performance during testing and race

conditions.

Although the Spur Gear design scored well on its simplicity and efficiency, it was in the above

criteria that raised the score making it inadequate at this current time.

When looking into the simplicity and efficiently of the Helical Gear it scored an average mark as a

result of the teeth being at a slight angle. In order for the effective operation of this gear the angle

has to be manufactured correctly.

Although the decision matrix proved that the Single 520 chain method was the most effective at this

present time, it may be possible in future Formula Student events for the university’s car to run a

gear driven system once sufficient data has been gathered about its reliability and the track and

racing conditions.


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Research conclusions

From the research carried out on the Final Drive mechanism it was evident (as represented in the

evaluation table Appendix E) that a Single 520 Chain driven mechanism was ultimately the

preferred choice amongst the teams from the 2014 event.

The most popular gear driven method that was chosen was that of a Spur Gear.

Upon further review of each drive method it was found that, for the Spur Gear:

Although this gear is used for its simplicity of design there is a considerable amount of

stress loads that pass through the gear when in operation combined with the generation of

significant amounts of noise. Whilst reviewing this gear the information listed above

showed that it is better used on lower powered applications, which then directed me onto the

Helical Gear for drive mechanisms.

Investigation into the Helical Gear has highlighted that this is the preferred option for Final

Drive mechanisms as this can be found in almost all car transmissions. Compared against

the Spur Gear the Helical Gear has angled cut teeth to provide for a smoother and quieter

operation, creating a thrust load when they mesh together. This in turn reduces the amount

of stress applied through the gear when in operation.

The review on the Single 520 Chain highlighted that, by using this method, it allows for better

performance and product life due to the manufacturing methods relating to how the sprockets and

the chain are developed, thereby making this the preferred option for the majority of the teams to

use in the Formula Student event.

Moving on from the research, the Final Drive method which will be carried forward is that of a

chain driven mechanism for several reasons:

1. This is the university's first attempt at this prestigious racing event and the reliability is

currently a high risk factor, so a drive mechanism which is easily accessible is by far the

most effective and safest approach as any problems can be fixed quickly without having to

dismantle big sections of the car wasting valuable time in the pits.


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2. The use of a gear driven mechanism may be a possibility in future events when the

reliability of the team’s car has improved. Using gear driven systems means that they have

to be enclosed into a casing making it harder to gain access to them in the event of a

problem, leading to either retirement or wasting valuable time in the pits trying to rectify

any problems.


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Design

1.10 Initial design ideas

With each of these design ideas they show a variety of mounting points. This variation was used as

a test to see how the positioning would work. The final total number of mounting points would be

confirmed prior to the final design being drawn up.

The same will apply for the number of teeth on the gear which will be set once the final gear ratio

has been determined.

Design 1 (Appendix G)

The first conceptual design for the gear uses a top flat tooth. By using the top flat tooth design it

allows for stability in the gear teeth and a wider surface area that will come into contact with the

chain when in operation.

Design 2 (Appendix H)

The design of this gear uses pointed teeth. The pointed tooth design is an improved version of

design 1 by using pointed teeth which are design to grip and prevent the chain from slipping when

in operation.

Design 3 (Appendix I )

This design uses a combination of designs 1 and 2. By using the flat base for increased strength on

the gear teeth with the pointed top on the tooth to help catch and grip the chain better when the

system is in operation.

Design 4 (Appendix J)

This uses a curled teeth design with the aim of catching the teeth better when the system is in

operation. Another advantage of using the curled teeth on this design is to prevent the chain from

slipping off the gear as it rotates.

A set back to this design is that if the angle of the teeth is not correct then the chain won't release at

the required time and can cause serious damage to the rest of the car.


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1.11 Design ideas decision matrix

Now the four initial conceptual designs have been derived the next stage is to determine which

concept is overall the most suitable to continue forward to the end of the project. To determine the

best concept the use of a decision matrix was necessary and the criteria and results from the matrix

can be found below with the matrix table located in the appendices (Appendix K on page 45).

The scoring is, again like the previous matrix, based upon a 1 - 5 system. Further details for this

scoring system can be found under sub heading 1.9 Final Drive decision matrix on page 21.

The criteria for this decision matrix is listed below:

1. Will the design of the gear teeth grip the chain: Will the teeth on the

gear grip the chain

sufficiently for the most

effective performance.

2. Is the design of the gear teeth practical: Is the gear teeth design

used appropriate to its

required application.

3. Is the overall design of the gear practical: Does the gear design

full fill its required purpose.

4. Are the mounting holes required: The mounting holes for the

Sprockets may not be required

as this is dependent upon the

differential design that will be

used


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From reviewing the conceptual four designs in the decision matrix it is clear to see that the best

design to continue the project with is design three.

On closer inspection of the decision matrix we can see that the third design was scored as the

overall best design as it was determined to be the clear winner at gripping the chain along with the

practically of the gear teeth themselves. The overall practically of the gear was considered to be

average in the matrix as the design is subject to amendments.

These amendments are constrained to two factors which are:

1. The Number of teeth the gear will have. – This will be determined through the Gear Ratio as

the number of teeth on the front sprocket determines the number of the teeth on the rear.

(See page 29 for the table showing the number of teeth required for the gear.)

2. The number of mounting holes on the sprocket – This will be determined by the type of

differential that will be used. (See page 29 for the information relating to the type of

differential used on this project.)

The two conceptual designs which scored the highest were designs two and four. Although it was

reflected in the matrix that the concept of design four would grip the chain better, because of the

curled teeth it was determined that this could also hinder the release of the chain from the gear as it

rotates. Also in relation to the complexity of this design concept the manufacturing would take

longer. This would be as a direct result of the shape of the teeth, as the angles would have to be

correct in order for it to function fully.

It was also considered that design two would grip the chain sufficiently because of the point on the

tip of the teeth.

Reviewing conceptual design one, this scored the highest points on the design of the teeth and their

practically as the chain could be seen not to grip the teeth to allow for an efficient and effective

operation of the components.

With the remaining criteria looking at the practicality and mounting holes, all the designs scored the

average rating. The reasons behind this average rating was because whichever design would be

taken foreword would be subject to a redesign of the number of teeth once the gear ratio's have been

finalised and the number of mounting holes once the differential has been chosen.


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1.12 Information from other team members

Following the four initial conceptual designs before a final design could be constructed certain

information is required from other team members. The required information consists of the Gear

Ratio which will determine the number of teeth for the Final Drive sprockets.

The other piece of required information was how many mounting holes the sprocket is required to

have so that it will join to the differential.

The design assumptions below will be made for my final design until the exact parameters have

been confirmed:

Number of teeth:

This assumption has to be based upon the chosen Gear

Ratio so the number of teeth for the front sprocket will

range from 11 - 16 and for the rear sprocket the range will

be from 45 up to 55.

(As shown in the table opposite.)

Mounting holes on the sprocket to connect to the differential:

The mounting holes for the sprocket are also dependent upon another factor, in this case its reliant

on the differential setting used. Although the final number is still to be confirmed the assumption

can be made that the minimal required mounting holes will be 2.

After my fellow team members had concluded their results the final parameters for my design is as

follows:

Number of teeth on sprocket:

As the desired Gear Ratio has been determined as 3.4375:1, which means the

number of teeth for the sprockets are as follows, 16 teeth on the front sprocket and

55 teeth on the rear sprocket.

Mounting holes to connect sprocket to differential:

The differential that was used is a Drexler differential package. This package

requires the sprocket to have twelve mounting points.

Front Sprocket Rear Sprocket

11 45

12 46

13 47

14 49

15 51

16 55


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1.13 Design calculations

Following the supplied information of the derived gear ratio and the number of teeth for each of the

sprockets some simple calculations were done to determine the basic dimensions. By using a

website that calculates the sprocket dimensions and chain requirements the following was derived.

Basic Sprocket Dimension:

By entering the number of teeth on the sprocket the calculations determined the chain pitch and the

diameter of the sprockets.

Chain Pitch = 0.625

Number of teeth 16 (Front sprocket) = Ø 81.372 mm

Number of teeth 55 (Rear sprocket) = Ø 278.075 mm

Distance between sprockets centre to centre:

This was calculated by entering the number of teeth on the front and rear sprockets and the number

of links that the chain will have. An assumption was made that 100 links would be used for the

chain this assumption may change during the assembly of the package.

Front Sprocket 16 teeth

Rear Sprocket 55 teeth

Number of Links 100

Distance centre to centre = 502 mm

Chain Length:

This is a simple calculation done by entering the number of links that the chain will have.

Number of links 100

Chain Length = 1587.5 mm


31

The conclusions that can be taken from these calculations are:

Front Sprocket (16 teeth) Ø 81.372 mm

Rear Sprocket (55 teeth) Ø 278.075 mm

Distance centre to centre 502 mm

Number of Links 100

Chain Length 1587.5 mm

In the appendices (Appendix L) is a table with the above calculations and velocity ratios for the

chosen sprocket package. The table also shows a set of calculations for a sprocket package that uses

a 14 tooth front sprocket and a 49 tooth rear sprocket. This new package was considered as it gives

the car improved performance. Although this package improves the performance, the selected

engine which will be used for this car is already supplied with a front sprocket of 16 teeth hence

why the above package was chosen.

The new package could be developed to replace this chosen one on the car at future events.

The link to the website for the calculations can be found listed in the bibliography. [10] [11]


32

1.14 Final design

Taking the above information relating to the number of teeth and mounting points, along with the

design calculations, a final design for the rear sprocket has been created in Solidworks (Appendix

M). The front sprocket does not require a design as this was already included on the engine

purchased for the car.

As shown in the final design (Appendix M) there are 12 mounting points which will be used to

connect the sprocket to the differential package during the assembly. The rear sprocket has 55 teeth

as constrained by the final gear ratio of 3.4375:1. Also shown are 7 cut outs which have been

incorporated to help reduced the overall weight of the sprocket but also to keep sufficient strength

in the component when in it is in operation.

This design can now be carried forward to the manufacturing stages on this project.

At the manufacturing stage there is a decision as to whether to manufacture the component in house

or to purchased it externally. The preferred option would be for the component to be manufactured

in house as the required facilities are present, thus saving cost and time on the production and

delivery if it was purchased elsewhere.

The next stage is to decide from what material the sprocket will be made. By following the

information listed in the report on the Single 520 Chain (Page 18) it shows that the sprocket has

been made from carbon steel over aluminium in order to provide extended chain wheel life. From

using the carbon steel, the sprockets are then electroplated to prevent corrosion and the teeth are

hardened to increase durability.

Carbon steel would be a suitable material to use as it is cheap to purchase and easy to machine but

the extra processes required to protect the component make it a long manufacturing process. An

alternative material that could be used is carbon fibre. Although carbon fibre is more expensive to

purchase it the most preferred material to be used in racing as it is lighter in weight, stronger and

more durable. This means it holds a higher resistance under impact and against corrosion. The

overall manufacturing process is quicker as the material doesn't have to be plated and treated as in

the case of carbon steel.

By manufacturing the sprocket this will result in the Single 520 Chain being the only part of the

Final Drive package that will be purchased.


33

1.15 Shatter Guard design

The design of the Shatter Guard for the sprockets is constrained by the Formula Student Technical

Regulations 2015-2016.

The most relevant section is listed below with all the overall points from this section of the

regulations listed under heading 1.3 Formula Student Regulations Pages 12 & 13.

The design of the Shatter Guard that must be used with the chain driven system is constrained in

design by the requirement below:

Chain Drive - Scatter shields for chains must be made

of at least 2.66 mm (0.105 inch) steel (no alternatives

are allowed), and have a minimum width equal to

three (3) times the width of the chain. The guard must

be centred on the centre line of the chain and remain

aligned with the chain under all conditions.

[12]

Following the design of the Shatter Guard the next stage was to figure out how this will be attached

to the car. This will be done by the use of three brackets.

Two of the brackets will be positioned on the top of the guard at the rear of the suspension and the

third bracket will be attached to the Shatter Guard underneath so that all areas of the guard are

secured to reduce the amount of vibration that will be imposed on the component.

In manufacturing, at the point where these brackets will connect to the chassis, they will have to be

rolled so that more of the bracket comes into contact with the chassis to improve stability of the

shatter guard.

The drawings of the Shatter Guard and the supporting brackets can be found in the appendices

(Appendix N).

The areas where the bracket will attach to the chassis of the car can be seen in the appendices

(Appendix O) with the proposed area for attachment highlighted by red boxes.


34

Conclusion

The conclusions which can be drawn from this report on the Formula Student project, focusing on

the Final Drive system, is that analysis has been conducted into the type of systems that current

Formula Student teams apply on their cars. This has been evaluated to derive the best system to use

along with factoring in the reliability and performance issues that are faced by the university's team

upon entering the event for the first time.

Based on the above research an effective and efficient Final Drive system has been designed which

will be applied to the car once the manufacturing is complete.

The final design that has been produced, following the conclusions drawn from the research and

decision matrices, have been constrained by other factors on the race car such as the gear ratios, the

differential used and the Formula Student Technical Regulations. The constraint imposed by the

technical regulations means that as the chain and sprocket system has been applied a Shatter Guard

would also be required.

This reports also recommends that it may be possible to use a Final Drive system operated by gears

for future events once the reliability has been tested and sufficient data has been collated on the

track conditions and then simulating how the gear system will stand up to the event requirements.

The other recommendation is that the manufacturing is completed in house to reduce costs and

production times imposed through purchasing the product. The use of carbon fibre material for the

sprocket instead of carbon steel has also be suggested because of the materials lightweight and

strength.

Also mentioned is the use of another sprocket package that could be used to replace the chosen one

at a future events. The alternative uses a 14 tooth front sprocket and 49 tooth rear sprocket to

improve the speed of the car. (This data can be found in the appendices Appendix L page 45.)


35

Appendices

Appendix A Initial Gantt Chart Page 36

Appendix B Gantt Chart version 1 Page 37

Appendix C Gantt Chart version 2 Page 38

Appendix D Gantt Chart version 3 Page 39

Appendix E Evaluation table of 2014 Formula Student entries Page 40

Appendix F Final Drive decision matrix Page 40

Appendix G Sprocket drawing 1 Page 41

Appendix H Sprocket drawing 2 Page 42

Appendix I Sprocket drawing 3 Page 43

Appendix J Sprocket drawing 4 Page 44

Appendix K Design ideas decision matrix Page 45

Appendix L Design calculations table Page 45

Appendix M Final sprocket design Page 46

Appendix N Shatter Guard with supporting brackets Page 47

Appendix O Photo's of the current chassis Page 48


36

Appendix A Initial Gantt Chart


37

Appendix B Gantt Chart version 1


38

Appendix C Gantt Chart version 2


39

Appendix D Gantt Chart version 3


40

Appendix E Evaluation table of 2014 Formula Student entries

Type of Drive

Mechanism

Class1

Class 2 Total

Single 520 Chain 50 (1) 5 55 (1)

Single 428 Chain 5 1 6


Single 425 Chain 1 - 1


Single 420 Chain 1 - 1

Spur Gears 6 (3) - 6

Planetary Gears 4 (4) 1 (1) 5 (5)

Epicycle Gears 1 - 1

Helical Gears 1 1(1) 2 (1)

Other 18 12 30

N/A 2 1 3

123 (7)

The rows that have a number enclosed within the brackets means that it's combined

with another mechanism.

The rows with a dash in them represent a 0.

Appendix F Final Drive decision matrix

Scored from 1-5 with 1 being the better score (the lower the total score the better)

Final

Drive

Methods

against

Design

Criteria

Design

Simplicity

Accessibility

for

maintenance

Efficiency Is the use of

a shatter

guard

required

Does the

mechanism

require to

be enclosed

in a housing

Is the design

going to have

an effect of

the weight of

the car

Total

Single 520

Chain 1 1 1 5 1 1 10

Spur Gear 1

5 1 1 5 4 17

Helical

Gear

3

5 2 1 5 4 20


41

Appendix G Sprocket drawing 1


42

Appendix H Sprocket drawing 2


43

Appendix I Sprocket drawing 3


44

Appendix J Sprocket drawing 4


45

Appendix K Design ideas decision matrix

Scored from 1-5 with 1 being the better score (the lower the total score the better)

Appendix L Design calculation table

Designs

against

criteria

Will the design of

the gear teeth

grip the chain

Is the design of

the gear teeth

practical

Is the overall

design of the gear

practical

Are the mounting

holes required

Total

Design 1 4 4 3 3 14

Design 2 3 3 3 3 15

Design 3 2 2 3 3 10

Design 4 3 3 3 3 15

Information for Existing

Front & Rear Sprocket

Package

Information for

New Front & Rear

Sprocket Package

Number of Teeth on front Sprocket 16 14

Number of Teeth on Rear Sprocket 55 49

Final Drive Ratio

(Front Sprocket: Rear Sprocket)

3.4375:1

3.5:1

Distance between Sprockets

(Centre to Centre)

502.30mm

743.69mm

Diameter (Ø) of Front Sprocket 81.372mm 71.341

Diameter (Ø) of Rear Sprocket 278.075mm 247.775mm

Chain Pitch 0.625

No of Links 100

Chain Length 1587.5mm

Velocity Ratio 1:0.29 1:0.28


46

Appendix M Final sprocket design


47

Appendix N Shatter Guard with supporting brackets


48

Appendix O

These photos’s are of the current chassis of the university’s car.

The arrow on this image represents the

position of the front sprocket and the

area covered by the red box shows

where one of the three supporting

brackets for the shatter guard will be

positioned.

The arrow on this image represents

the position of the front sprocket

and the area covered by the red box

shows where the other two

supporting brackets for the shatter

guard will be positioned.

The arrow on this image represents

the position of the front sprocket and

the area covered by the red boxes

shows where all of the supporting

brackets will be positioned.


49

Bibliography

[1] SAE International Formula Student Technical Regulations 2015 -2016

Part T General Technical Requirements, Article 8 Power train Pages 62 / 63

[2] Straight Axel Drive Image

http://maybach300c.blogspot.co.uk/2012/09/rigid-and-semi-rigid-crank-axle.html

[3] Pinion Gear Image

http://goldwingdocs.com/Images/HowTo/RearWheel/RearWheel98.jpg

[4] Planetary Gear Image

http://www.china-reducers.com/planetary-gearboxes-china-made.jpg

[5] The Formula Student 2014 event programme

http://www.racecar-engineering.com/formulastudent

[6] Single 520 Chain Information

http://www.motosport.com/vortex-520-steel-sprocket-chain-kit

[7] Single 520 Chain Image

http://www.mopartsracing.com/parts/ram/chain.gif

[8] Spur Gear Image

http://cf.ydcdn.net/1.0.1.30/images/main/spur%20gear.jpg

[9] Helical Gear Image

http://s.hswstatic.com/gif/gear-helical2.jpg

[10] Design Calculation Information

http://www.f650gs.crossroadz.com.au/Calc-Chain.html

http://goldwingdocs.com/Images/HowTo/RearWheel/RearWheel98.jpg

http://www.china-reducers.com/planetary-gearboxes-china-made.jpg

http://www.motosport.com/vortex-520-steel-sprocket-chain-kit

http://www.mopartsracing.com/parts/ram/chain.gif

http://cf.ydcdn.net/1.0.1.30/images/main/spur%20gear.jpg

http://s.hswstatic.com/gif/gear-helical2.jpg

http://www.f650gs.crossroadz.com.au/Calc-Chain.html


50

[11] Design Calculation Conversion

http://www.metric-conversions.org/length/inches-to-millimeters.htm

[12] Shatter Guard Image

SAE International Formula Student Technical Regulations 2015 - 2016

Part T General Technical Requirements, Article 8 Power train Page 62

http://www.metric-conversions.org/length/inches-to-millimeters.htm

Documents

Dissertation Hardcopy (My Version)