Formula Sae Final Report

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Formula SAEFinal Design Report

AdvisorDr. Sam Drake

Team

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Table of Contents

1 Executive Summary.......................................................................................... 53 Design Requirements...................................................................................... 12

3.1 Introduction............................................................................................................. 12

3.2 Functional Requirements........................................................................................ 123.2.1 Functional Requirements Formula SAE......................................................... 123.2.2 Chassis............................................................................................................123.2.3 Suspension...................................................................................................... 123.2.4 Brakes.............................................................................................................133.2.5 Safety..............................................................................................................133.2.6 Opportunities................................................................................................... 133.2.7 Assumptions.................................................................................................... 13

3.3 Physical Requirements............................................................................................ 133.3.1 Physical Constraints......................................................................................... 133.3.2 Chassis............................................................................................................13

3.3.3 Suspension...................................................................................................... 143.3.4 Safety..............................................................................................................143.3.5 Opportunities.................................................................................................... 143.3.6 Assumptions..................................................................................................... 14

3.4 External Requirements............................................................................................ 153.4.1 Opportunities.................................................................................................... 153.4.2 Assumptions..................................................................................................... 153.4.3 Constraints....................................................................................................... 15

4 Design Specifications................................................................................ 174.1 Chassis.................................................................................................................... 17

4.1.1 Problem Statement........................................................................................... 17

4.1.2 Requirements and Specifications..................................................................... 174.1.3 Concept Generation......................................................................................... 174.1.4 Design Refinement........................................................................................... 20

4.2 Steering................................................................................................................... 284.2.1 Problem Definition........................................................................................... 284.2.2 Requirements and Specifications..................................................................... 284.2.3 Concept Generation......................................................................................... 304.2.4 Design Refinement........................................................................................... 324.2.5 Final Selection................................................................................................. 35

4.3 Suspension A-Arms and Suspension Brackets....................................................... 374.3.1 Problem Definition.................................................................................... 37

4.3.2 Requirements and Specifications.............................................................. 374.3.3 Concept Generation.................................................................................. 374.3.4 Design Refinement........................................................................................... 384.3.5 Final Selection.......................................................................................... 39

4.4 Push Rod and Rocker Arm..................................................................................... 404.4.1 Problem definition. .......................................................................................... 404.4.2 Requirements and Specifications..................................................................... 404.4.3 Concept Generation......................................................................................... 40

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4.4.4 Design Refinement........................................................................................... 424.4.5 Final Selection................................................................................................. 42

4.5 Impact Attenuator................................................................................................... 444.5.1 Problem Definition........................................................................................... 444.5.2 Requirements and Specifications..................................................................... 44

4.5.3 Concept Generation......................................................................................... 444.5.4 Design Refinement........................................................................................... 454.5.5 Final Selection................................................................................................. 45

4.6 Engine Selection..................................................................................................... 504.6.1 Problem Definition.......................................................................................... 504.6.2 Requirements and Specifications.................................................................... 514.6.3 Concept Generation........................................................................................ 524.6.4 Design Refinement..........................................................................................554.7.5 Final Selection................................................................................................ 57

4.7 Intake Manifold....................................................................................................... 584.7.1 Problem Definition........................................................................................... 58

4.7.2 Requirements and Specifications..................................................................... 584.7.3 Concept Generation......................................................................................... 594.7.4 Design Refinement........................................................................................... 614.7.5 Final Selection................................................................................................. 61

4.8 Rear Drive............................................................................................................... 624.8.1 Problem Definition........................................................................................... 624.8.2 Requirements and Specifications..................................................................... 624.8.3 Concept Generation......................................................................................... 634.8.4 Design Refinement........................................................................................... 654.8.5 Final Selection................................................................................................. 66

4.9 Shift and Clutch Interface....................................................................................... 684.9.1 Problem Statement........................................................................................... 684.9.2 Requirements and Specifications..................................................................... 684.9.3 Concept Generation......................................................................................... 684.9.4 Design Refinement........................................................................................... 694.9.5 Final Selection................................................................................................. 72

4.10 Shift Handle.......................................................................................................... 754.10.1 Problem Definition......................................................................................... 754.10.2 Requirements and Specifications................................................................... 754.10.3 Concept Generation....................................................................................... 754.10.4 Design Refinement.........................................................................................754.10.5 Final Selection............................................................................................... 78

4.11 Controls................................................................................................................. 804.11.1 Problem Definition......................................................................................... 804.11.2 Requirements and Specifications................................................................... 804.11.3 Concept Generation....................................................................................... 804.11.4 Design Refinements....................................................................................... 824.11.5 Final Selection............................................................................................... 82

5 Recommendations...................................................................................... 835.1 Start Early...............................................................................................................83

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The biggest recommendation we have for this semester is to start early andkeep as organized as possible.6 Project Planning........................................ 84

6.1 Gant Chart............................................................................................................... 84

7 Resources and Reference Materials........................................................... 857.1 References............................................................................................................... 85

7.2 Resources................................................................................................................858 Appendix....................................................................................................86

Figure 1 Detail Drawing of Impact Attenuator............................................................. 86Figure 2 Detail Drawing of Honeycomb for Impact Attenuator................................... 87Figure 3 Detail Drawing of Clutch Pedal. .................................................................... 88Figure 4 Detail Drawing of Shift Handle...................................................................... 89Figure 5 Detail Drawing of Pushrod and Rocker Assembly......................................... 90

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2007 FORMULA SAE TEAM MEMBERSJosh Smith (Capt.) Kent Feda Colby Englund Brett GeorgeBen Opfermann Omar Saleb Josh Nell Guy PannunzioEliot Moellmer Tyler Child Eric Youssefi Lucas Sosa

Faculty Advisor: Dr. Samuel Drake

1 Executive Summary

The Formula SAE project started nearly 25 years ago as an informal mini Indy

competition between college design groups. Today over two hundred universities

participate in yearly competitions held in six different countries. The University of Utah

design team will be entering the Detroit, MI competition in May 2007. The premise of

the competition is that student teams have been hired to build a prototype car which will

be marketed to the weekend amateur autocross racer for under $25,000. Scoring will be

based on marketability to the target consumer group, racing performance, merits of the

design, cost, and ease of manufacturing and maintenance. This report will cover the

details and rationale for the teams design, the specifications of the prototype, and the

research done into the methods that are being employed to complete the design. Because

the car will be built for autocross racing the team chose weight, handling, and

acceleration as the most important design factors.

The first main design goal is to keep the car as light as possible. To accomplish

this, the team has decided to build the chassis and body out of carbon-fiber. Using carbon

fiber will permit the chassis to be structurally equivalent to a standard steel tube frame ata fraction of the weight. The teams chosen design will look similar to monocoque

designs used by most universities including previous University of Utah team designs. A

monocoque design, comparable to a fuselage, integrates the body and chassis, and carries

the major part of the stresses in the outer skin. In contrast, the 2007 University of Utah

car will have a separate chassis with a detachable body panel.

The chassis will provide the main support structure and side impact protection

similar to a boat hull. The front and rear roll hoops, which are required to be made from

steel tube, will be integrated into the chassis and will also provide additional support for

the suspension and spring mounts. The body will protect the driver from external

exposure but will require much less material to fabricate than the chassis. It will also be

detachable to offer easy maintenance access to internal components. This two-piece

design will provide the required side impact and rollover protections and structural

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support but will be much lighter than typical monocoque designs since less material will

be utilized. Less material will also mean less cost which, as previously mentioned, will be

an important part of the judging.

According to the competition rules, the engine is limited to a 610cc, four-stroke,

piston engine with a restrictor on the air intake to limit horsepower. The restrictor also

makes it more difficult to maintain a smooth airflow necessary for a consistent air-fuel

mixture at different engine speeds. The team has purchased a 599cc, four-cylinder

motorcycle engine and will be building a new throttle body and air intake to meet these

restrictions. This engine was selected because it is compact in size, light-weight and is

designed to provide a broad powerband. The race focuses on acceleration rather than top

speed, and this engine will provide the low-end torque necessary for both the autocross

courses and acceleration events. In addition, a four cylinder engine, compared to a one

cylinder engine with a similar displacement, can pull in air more smoothly through the

restrictor and will not require the addition of a supercharger. Keeping the engine

normally aspirated will reduce the complexity, weight and cost of the intake design.

The suspension, steering, and wheelbase designs will all be optimized for quick

and responsive handling through the winding autocross course. The team has chosen to

use an unequal length, non-parallel, A-arm suspension layout. This concept is the most

commonly utilized design in open wheel racing. The team decided that this layout would

provide the most adjustability in camber changes and roll centers which will be discussed

in further detail in the report.

Because of the collaborative effort required to complete this project, every team

member is expected to have a general understanding of the entire project as well

specialized knowledge of a specific portion of the project. Scoring of the competition will

not only be based on how well the drivers do in the various races. Members of the team

will also be required to defend the decision making process for each aspect of the car and

will have to present the marketing strategy to the competition judges. To accomplish our

overall goal of winning the competition our strategy is to build a racecar that is light-

weight, quick, and responsive in the curves, while being low cost to manufacture and

maintain.

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2 Context

2.1 Need Statement

Formula racing is not only a sport for professionals; it is an attraction to a variety ofpeople. Besides the professional market, there is market oriented toward the non-professional weekend autocross racer. The Formula SAE team will take the hypotheticalidea that a manufacturing firm has contracted the team to develop a concept racing car formass production. The team will take this market and will design a car that will fulfill theneeds of an amateur racer. Some of these needs include: low cost, high performance,aesthetics, safety, and reliability.

But, this is not the only goal for this project; another motivation for successfullycompleting the design is that the team will present the finalized car in an intercollegiatecompetition to be held in April 2007 at Ford Proving Grounds in Dearborn, MI.

Therefore, the 2007 Formula SAE team will design a prototype car intended for theweekend amateur racer that posses all the attributes necessary to succeed in the nonprofessional market and will base the construction according to the 2007 formula SAErules manual.

2.2 Problem Statement

Developing a racing car capable to compete in the market is not an easy task; the teamwill have to face a series of problems and constraints that will challenge the successfulconstruction of the prototype. Since the intended market is the nonprofessional weekendautocross racer it is required that the car has high performance acceleration, braking,

easy maintenance, and reliability, as well as being aesthetically pleasing and comfortable.The vehicle must also be constructed according to the 2007 Formula SAE rules whichemphasize security. These rules can be found in the following website:http://students.sae.org/competitions/formulaseries/rules/rules.pdf. In the end, the teamwill take their prototype to Detroit in May 2007 to compete against other engineeringprograms in all these aspects.

Besides the technical needs, one of the most important issues that constrain theconstruction of the project is the budget. The total construction cost must be under$25,000, but the real challenge is raising this money for the construction of the prototype.

2.3 Design Team

Student Design Team MembersThe 2007 University of Utah Formula SAE Team is form by twelve students, as picturedin Figure 1.

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Figure 1: The 2007 Formula SAE Team of Utah

Top Row (From Left): Eric Youssefi, Omar Saleb, Lucas Sosa, Guy Pannuzio,Ben Opfermann, Tyler Child, Josh Smith, Colby Englund, Josh Nell

Bottom Row (From Left): Elliot Moellmer, Brett George, Kent Feda

Below is a description of each team members responsibilities and contact information.

Josh Smith - Team [email protected]

Josh has assumed the role of team leader. He is responsible for coordinating andoverseeing all the team efforts. This is Josh's third year in the Formula SAE team,which gives him valuable experience in leadership, racecar dynamics, driving,suspension, and composites.

Eric Youssefi - Safety and Ergonomics / Fund [email protected] will focus his efforts in designing the crash structure of the car, as well asraising money through sponsors and team activities. He brings creative problemsolving skills to the team.

Omar Saleb - Safety and [email protected] will be designing the front impact attenuator and the location of the driverinterface. He brings knowledge of design and manufacturing to the team and alsohas a great personal interest in race cars.

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Lucas Sosa - Safety and [email protected] is leading efforts in modeling and manufacturing the energy absorbingstructure as well as the front bulkhead and the car seat. He has a valuablebackground in safety, which will be useful in the overall design of the car.

Guy Pannuzio Chassis and [email protected] will be designing and manufacturing the cassis and suspension. He workedfor six years repairing automobiles, and one year as a design engineer. He isskilled in welding, solid modeling, and finite element analysis.

Ben Opfermann Engine and [email protected] will focus on ensuring that the engine runs properly and with maximumperformance. Ben brings skills in engine tuning and transmissions work to the

team.

Tyler Child Chassis and [email protected] will be designing the chassis and suspension of the car. He has beenworking as a design engineer and brings a background and working knowledge ofmaking prototypes, machine work, and CAD design to the team.

Colby Englund Engine and [email protected] will be working on the engine, and drive-train. He worked as a designengineer, and he brings solid modeling, as well as manufacturing skills to theteam.

Josh Nell - Engine and Drive-train / [email protected] will be working on the engine, drive train, and the electrical part of the car.He is skilled in 3D modeling, computer programming, computer control, andengines repair.

Eliot Moellmer Engine and [email protected] will focus his efforts working on the engine, and designing the drive-train.He has work experience with Chevrolet engines, muscle cars, manual andautomatic transmissions, and drive-trains.

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Brett George Chassis and Suspension / [email protected] will be designing the chassis, suspension, and the electrical part of the car.He brings three years of experience in auto mechanics to the team and is alsohighly skilled in electrical wiring and MIG and TIG welding.

Kent Feda Fund Raising / [email protected] will have the difficult task to raise many for the expenses of our project.Also, he will be designing the electrical part of the car. Kent brings goodcommunication, organization, and management skills to the team.

Dr. Samuel Drake Research Associate Professor / Faculty [email protected]

Teaching Team

William Provancher - Asst. [email protected]

Nick Sylvester - Teaching [email protected]

Sam Segal - Teaching [email protected]

Marlin Taylor - Written Communications Teaching [email protected]

Andy Dohanos - Oral Communications Teaching [email protected]

Corporate Liaisons and Sponsors

Formula SAE team receives support from the following sponsors:Tom Feda: in-kind donations for food handler's permits and IRS form 1023Brett George: in-kind donation of engineSolidworks: in-kind donations of 12 student versionsHuntsman Advanced Materials: miscellaneous supportLotus: SoftwareIndustritek (Rick McMillen): miscellaneous support

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The team is pending support from the following sponsors:Larry H. Miller Motorsports ParkHonda Suzuki of Salt LakeSpeed Street

Bolt and Nut SupplyMcLean Quality Composites

2.4 Team Circumstances

The Formula SAE project is a competition among teams from different universities. Thiscompetition challenges students to design and build a formula style car. This projectgives members the opportunity to apply and demonstrate their creativity and engineeringskills. The team consists of twelve talented students that are committed to designing,building and testing the car in an eight month period, while remaining within thedesignated budget. The team is highly motivated to win the competition and possesses

the skills and knowledge necessary to meet the challenges this project involves. Eachmember has committed to work in his area of expertise and to perform his tasks in atimely manner. The areas of expertise were divided in five categories with include:engine and drive train, chassis and suspension, safety and ergonomics, electrical, andfund raising. Every subgroup will present the whole design, including modeling,fabrication, and assembly, along with their confidence, in a successfully built race car bythe end of February 2007.

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3 Design Requirements

3.1 Introduction

Students are employed to design, fabricate and demonstrate a prototype car for evaluation of a

production item. The intended market for the car is the weekend autocross racer that is interested

in competing at a higher level. The design will be compared and judged with other competing

designs to determine the best overall car for production.

3.2 Functional Requirements

The functional requirements define how the car will perform. There are many different aspects of

the car that define the functional requirements and will be broken up into different sections to

cover each aspect.

3.2.1 Functional Requirements Formula SAE

Allow space for 95th percentile of Americans to fit in vehicle Have the ability to corner smoothly with large lateral gs Have braking ability to stop all four wheels at same time Must be able to protect occupant in event of a high speed impact Ability to accelerate very smoothly and fast3.2.2 Chassis

Requirements of the chassis are as follows:

Rigid Must contain a roll hoop for both the front and rear of vehicle Contain a front impact structure

The most important aspect of the chassis is the torsional rigidity of the car for cornering

stability. The suspension must attach to portions of the chassis that will allow the transfer

of forces to be absorbed by the stiffness in the chassis. It must be large enough to allow

each of the team members access into and out of the drivers compartment while

maintaining low weight.

3.2.3 Suspension

Suspension requirements define how well the car is going to handle in corners as well as

braking and acceleration. The suspension must support the chassis such that at no time

during a race, no part of the car will come into contact with the ground except the tires. It

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must have adjustability in order to allow tuning for different conditions of different

courses.

3.2.4 Brakes

The braking system must be employed such that the system acts on all four wheels and is

controlled by a single control. On a dynamic braking test, the system must be able to

lock all four wheels simultaneously while stopping the vehicle in a straight line.

3.2.5 Safety

Rider safety is the most important aspect of the design of the entire car. Safety measures

such as side impact retainers and a front crash structure will be employed to maintain

safety. Roll hoops will also be installed in the front middle and rear end of the car to

protect the driver in the event of a rollover.

3.2.6 Opportunities

The size of the car will be such that any weekend auto crosser can transport it from event to event

with as little amount of effort as possible. The car will have the performance to guarantee a

competitive run every time it goes out on the track. The seating of the car will be able to accept

nearly all people in the 95th percentile of Americans.

3.2.7 Assumptions

We are assuming that the weekend auto crosser will be using the car for a minimum of 26 weeks

out of the year for at least two days of the weekend for those 26 weeks. With such a demanding

schedule the car should be very reliable with parts that can be easily acquired from most any parts

store.

3.3 Physical Requirements

The physical requirements describe hot the FSAE vehicle will perform its specified function. All

of the physical requirements have been predetermined by the FSAE rule book.

3.3.1 Physical Constraints

The physical constraints are aspects listed in the Formula SAE handbook as to maintain a

car that will not be built outside the rules of competition. These restraints are listed

below.

3.3.2 Chassis

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The physical requirements of the chassis are based on the Formula SAE rules. The

following table lists the requirements for different materials used.

Material & Application Minimum Wall Thickness

Steel Tubing 2.0 mm (.079inch)

Aluminum 3.0 mm (.118inch)

Composites Equivalency Calculations

The chassis can be built of any of the listed materials individually or of a hybrid

construction of a combination of them all. In the composites sections proof of structural

integrity must be supplied to conform to the safety specification of the steel or aluminum.

3.3.3 Suspension

The car must be equipped with fully operational suspension system with shock absorbers,

front and rear, with a useable travel of 50.8mm (2 inches), 25.4 mm (1 inch) bound and

25.4mm (1 inch) rebound.

3.3.4 Safety

The front and main roll hoops must be constructed of a single piece of uncut closed

section of steel tubing specified in table 1. The side impact structures must have an outer

diameter of no less than 25.4 mm (1 inch) and must be located a minimum of 300-

350mm (11.8 13.8) from the ground line. The front impact attenuator must be at least

150 mm (5.9 in) long and must not allow more than 20 gs of deceleration felt by the

driver at a speed of 7 m/s (23 ft/s) in the event of a frontal impact.

3.3.5 Opportunities

The new FSAE car will appear different then the previous years vehicle. Many of the systems arebeing redesigned in order to meet all of the physical requirements set by the FSAE rulebook. The

systems are also being redesigned in order to achieve a much quicker acceleration, and much

better handling then the previous years vehicle.

3.3.6 Assumptions

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We are limited in the amount of acceleration that we can achieve by the size restriction placed on

engine displacement. We are also working under the assumption that any engine used will be in

existence, and the team will not design/manufacture its own engine. The suspension system will

be designed under the assumption that the difference in temperatures between summer and winter

will not greatly affect the damping factor of the shock absorbers. Also, it is assumed that the

vehicle will be driven on a smooth, level, hard surface, and will be designed accordingly.

3.4 External Requirements

The external requirements will describe the typical user of the FSAE vehicle, as well as the types

of situations the vehicle may be used.

3.4.1 Opportunities

Due to the limited space of the FSAE vehicle, the number of passengers will be limited to a single

driver. The internal compartment of the vehicle will enclose enough space such that a single

driver will have adequate room. The FSAE vehicles performance requirements require that the

chassis lays close to the ground which limits the driving terrain to smooth level surfaces.

3.4.2 Assumptions

It is estimated that the internal compartment will be large enough to accommodate up to a 95

percentile American male with respect to height. It is assumed that this driver will have physical

features that are not abnormal (e.g. abnormally disproportionately sized legs). It is assumed that

by lowering the ride height of the vehicle, the performance will not be negatively impacted, due

to the requirement that the vehicle must be driven on a smooth level surface.

3.4.3 Constraints

The average driver will not be subjected to severe discomfort

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The average drivers comfort should be accommodated according to modern ergonomic

principles. The driver should not be confined to operating the vehicle in severely

uncomfortable or awkward positions.

Safety will not be severely compromised for performance gains

Any objective that will enhance performance should not jeopardize the safety of the

vehicles user.

Performance tasks should not reduce the minimum amount of required space

Objectives implemented to enhance performance should not reduce the amount of

interior space in the vehicle beyond its set minimum needed to accommodate a 95

percentile male.

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4 Design Specifications

4.1 Chassis

4.1.1 Problem Statement

There are many goals when designing a racecar chassis but with any set of goals they aregenerally contradicting. Ideally the chassis would exhibit these characteristics:

1. Offer driver protection in the case of an accident2. Rigid3. Lightweight4. Inexpensive5. Allows easy access to internally mounted components6. Easy to manufacture

Goals such as lightweight and inexpensive and, Rigid and lightweight are in directcompetition with each other. To resolve some of these conflicting goals the 2007-08University of Utah Formula SAE team has developed some rather radical solutions whichwill be discussed in this report.

4.1.2 Requirementsand Specifications

There are many requirements that the chassis must be able to meet in order to be deemedsuitable for a racecar. There are the obvious requirement that is must be lightweight justas every component on a racecar must. Another major requirement is for the chassis tobe rigid. Having the chassis rigid allows the suspension to do its job more effectively.The more compliant the chassis is the harder it is to predict the dynamics of the racecar.It also needs to be easily manufactured in quantities of approximately four per day. Thiscar is designed to be for the armature, weekend autocross racer which in-of-its self hassome very demanding requirements. The car must be inexpensive yet have very highperformance capabilities. The target buyer also will most likely be doing all of themaintenance by themselves. This means that the car must be easy to maintain and thechassis must allow easy access to the cars internally mounted components. The chassismust also allow adequate space for all of the components of the car. This requirementseems obvious but, it is one of the most commonly overlooked requirements in theFormula SAE program

There are also some external requirements that are set by the sanctioning body SAE. Forthe chassis these requirements are mainly to ensure the driver and course worker safety.For a detailed list of theses requirements please refer to the 2007 Formula SAE Rules,specifically sections 3.1 through 3.5.

4.1.3 Concept Generation

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When looking at the chassis of a racecar there are a few proven choices for both materialand also construction design. For material there is steel, aluminum, titanium, magnesiumand carbon fiber. For construction type there is space frame and monocoque.

Each of there materials and construction types have their benefits. Steel and aluminum

are relatively inexpensive but when compared to some of the more advanced materialssuch as titanium and magnesium they are heavier. Titanium can be welded but requires askilled welder and also an inert environment to weld in. Magnesium is largely limited tomachining and casting applications.

There are primarily two ways to manufacture a racecar chassis. The most commonmethod is space frame or tube frame construction. This method uses tubes which arewelded together to create a frame. These frames are usually highly triangulated and usevarying size tubing for the local requirements of the chassis. These frames can be madeextremely light weight but they often sacrifice serviceability and driver comfort. Theadvantages of this type of construction are: inexpensive, easily designed and easily

manufactured. Space frame construction requires a separate body to be produced andfitted which increases part count, complexity and weight.

Monocoque construction is the second primary construction type. This type isconstructed in one of two ways. The first more historic way is using sheet metal that iscut and bent into the desired shape then riveted, bonded and/or welded together. Thisallows rather inexpensive materials to be used but requires very skilled metal workers tomanufacture. The second more modern way is to produce a mold of the desired shape ofthe chassis. Then layer carbon, core material, and more carbon into the mold. Thisproduces a sandwich composite which has very desirable properties such as highstrength, low weight and also the ability to create complex shapes fairly easily. Oneadvantage to either monocoque method is it doesnt require a separate body to be fittedbecause the chassis its self can be shaped in such a way that it takes the job of the body aswell as the chassis. This reduces part count, mounting complexity and weight. Theprimary problem with this construction type is it is generally very difficult to service thecars internally mounted components because there is no direct access to them.

After looking at the two traditional construction types there was always a compromisewhen selecting one or the other. Some initial goals that needed to be met where:

1. It must be easy to manufacture2. It must be light weight3. It must be easy to work on4. It must be inexpensive5. It must be stiff

Composite monocoque chassis are primarily hard to construct because the manufacturingprocess requires that the chassis be constructed in a split mold or the chassis must bemade in separate parts that are bonded together after they are each constructed. Both ofthese methods require a tremendous amount of effort. The completely enclosed chassismake the completed car very hard to work on, requiring you work through small

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openings or creative body placement to access components such as the brake, steeringsystem or dash electrical components. Carbon fiber is also very expensive so if it is usedas a manufacturing material it must be used effectively and sparingly. So after looking atthese limitations of the materials and construction styles an alternative needed to becreated.

The following are some concept sketches that show the basic layout of several differentchassis designs.

Sketch by: Josh Smith

This design has some advantages in that it would be very accessible because of the opentop design. However, the rear sub frame that attaches the engine to the chassis wouldneed to be quite extensive to accommodate the rear suspension system. This halfchassis design makes it possible to create the entire chassis with out the use of eithersplit molds or multi part construction. This reduces the time and cost of producing acarbon fiber chassis. Another benefit to this design is that there is very little carbon fiberused in comparison to a full monocoque chassis, further reducing the manufacturingcosts.

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This design is unique because it has no sub frame to support the engine and rearsuspension. The monocoque chassis extends to the rear of the car and thus the engineand rear suspension can both be mounted directly to the monocoque chassis.

These two concepts can be contrasted with a traditional monocoque chassis with a rearsub frame shown below.


4.1.4 Design Refinement

The chassis and body are one of the most complex components to model on the car.Because of this all of the concepts could not be modeled as it would be too time

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consuming. Instead a surface model of the general shape was created and somemeasurements were taken from it. The measurements of interest are the surface area ofthe chassis, because the surface area is directly related to the amount of carbon that willbe needed. Below are the measured surface areas for the different chassis configurations:

Traditional Monocoque with Sub-Frame: 3.08 m 2 Hybrid Chassis with Sub-Frame: 1.95 m 2

Hybrid Chassis: 3.16 m 2

So it can be seen that the hybrid chassis only requires 2.5% more carbon to produce thenthe traditional monocoque chassis with a sub frame. This is impressive considering thatthe hybrid chassis extends from the front to the very rear of the car. There is a greatbenefit here in that every major component of the car will be bolted directly to a singlestructure, the carbon hybrid chassis. This reduces the associated hardware frommounting to sub frames and also reduces the part count of the car.

After deciding on the course of action the basic form of the chassis and body wheredeveloped.

Model created by: Josh Smith

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Final Selection

By utilizing the hybrid chassis it will be possible to create a chassis that has comparablestiffness to a full carbon chassis with several added benefits. The hybrid chassis will not

require the complex split molds or multi-body construction of traditional compositechassis, which reduces the time and cost of production. The hybrid chassis will also bemuch easier to service as all of the components of the car will be easily accessible fromthe top of the chassis. Utilizing a full length composite chassis also eliminates the rearsub-frame and associated mounting hardware, thus reducing the complexity, weight, andpart count of the car.

So by sacrificing some stiffness compared to a traditional monocoque chassis it ispossible to elevate the following problems associated with a traditional monocoquechassis:

1.

Expensive Tooling2. Complex Tooling3. Serviceability Issues4. Manufacturing Time5. Cost

After the general form was created it was then sectioned and the individual parts of thechassis were made. The picture below shows the nose, body and chassis.

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After the nose, body and chassis were created they were all assembled to observe all ofthe interactions between the various components such as the driver, steering wheel,display, engine, front and main roll hoops and front suspension brace. Shown below areall of the above mentioned components.

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Here it shows the completed assembly.

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4.2 Steering

4.2.1 Problem Definition

In order for the 2007 University of Utah Formula SAE vehicle to be competitive in this

years competition, the car must be able to handle very well. A large portion of thehandling of the vehicle comes from the steering system. This steering system mustconform to SAE rules and regulations, be safe, easy to use, lightweight, and most of all,allow the vehicle to maneuver through the course as quickly as possible.

4.2.2 Requirements and Specifications

There are a number of rules set forth by SAE directly affecting the steering system. Theserules appear below.

The steering system must affect at least two wheels.

The steering system must have positive steering stops that prevent the steeringLinkages from locking up (the inversion of a four-bar linkage at one of the pivots). The stops may be placed on the uprights or on the rack and must prevent the tiresfrom contacting suspension, body, or frame members during the track events. Allowable steering system free play is limited to 7 degrees total measured at thesteering wheel. Rear wheel steering is permitted only if mechanical stops limit the turn angle of therear wheels to 3 degrees from the straight ahead position. The steering wheel must be mechanically connected to the front wheels, i.e. steer-by-wire of the front wheels is prohibited.

Following these rules is the first and most important requirement, as breaking any of these

rules will result in disqualification from the competition.

Suspension and Steering Geometry

In order for this years vehicle to handle as well as possible, many issues involvingsuspension and steering geometry must be taken into consideration. Bump steer,Ackermann, and Toe are the three most important issues to design around whendesigning a steering system.ToeToe is perhaps the most important variable when designing a steering system for a racecar. Toe is defined as the angle between the forward direction of the vehicle, and the

direction of the tire when looking from a top view. Toe in is when the tires point intoward the center of the vehicles centerline, while toe out is when the tires point outaway from the vehicles centerline. The diagram below shows an example of both toe in(red) and toe out (green).

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http://www.simpsonmotorsport.co.uk/uploads/files/SuspensionSetup.pdf

Bump SteerBump steer is directly related to the placement of steering components such as the rackand pinion and outer steering rod ends relative to the upper and lower control arms. Thefigure below is a diagram showing proper placement of components.

http://www.thedirtforum.com/bumpsteer.htmAs the diagram shows, Line 3 and Line 4 are imaginary lines created by the upper andlower control arms. The place where these lines intersect is called the instant center. Inorder to eliminate bump steer, the imaginary line created by the steering rod must alsointersect this line. This allows all of the suspension points to rotate about a fixed radius,keeping the wheels from toeing in or out depending on suspension travel.

Ackermann SteeringAckermann steering is a very important aspect of steering system design. Ackermann iswhen one tire is allowed to turn more than the other. The reason Ackermann is needed isbecause when a vehicle is executing a tight turn, both tires need to rotate about differentradii, and if nothing is done about this, one of the tires will scrub, causing unpredictablehandling. In order to compensate for this one tire(usually the inside tire) turns at an angle

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http://www.simpsonmotorsport.co.uk/uploads/files/SuspensionSetup.pdfhttp://www.simpsonmotorsport.co.uk/uploads/files/SuspensionSetup.pdfhttp://www.thedirtforum.com/bumpsteer.htmhttp://www.thedirtforum.com/bumpsteer.htmhttp://www.simpsonmotorsport.co.uk/uploads/files/SuspensionSetup.pdf


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greater than the outside tire, since the inside tire must turn a tighter radius than theoutside tire. The diagram below shows an example of ackermann steering.

http://www.auto-ware.com/setup/ack_rac.htm


Overview

During the initial brainstorming process, many different ideas were generated relating tothe steering system. While most previous Formula SAE teams have all used the sametype of setup, (i.e.: steering wheel input, rack and pinion to tie rod output) we decided toexplore different possibilities for driver input as well as the steering system output.

Concept 1:

Sketch by Brett GeorgeConcept 1 exhibits the most common steering design for Formula SAE vehicles. A rackand pinion setup is shown as the steering system output while a steering wheel is used forthe driver input. This design allows for easy and clean packaging of steering components,as well as a sense of familiarity for the driver, since they have experience with using asteering wheel; probably on a daily basis.Concept 2

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http://www.auto-ware.com/setup/ack_rac.htmhttp://www.auto-ware.com/setup/ack_rac.htm


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Sketch by Brett George

Concept 2 shows a slight variation on concept 1. The steering system output is the same,

however a set of handlebars are used instead of a steering wheel. While this idea mayhave some advantages, this is not a very practical design.Concept 3

Sketch by Brett GeorgeConcept 3 utilizes a steering wheel setup with a steering box output. While a steering boxis smaller and lighter weight, it is not as easily packagable as a steering rack would be,since a pitman arm must be used to actuate the steering linkage.

Concept 4

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Concept 4 uses a steering box setup with a handlebar input. This design is probably theleast practical of the designs. As mentioned above, the handlebars are not pracitcal due totheir size and required placement. The steering box is also not practical for reasonsdiscussed in the concept 3 explanation.


Overview

During the design process of the steering system for the 2007 Formula SAE vehicle, anumber of concepts were generated. While the brainstorming process was helpful instirring up new ideas for the steering system, the experiences of previous Formula SAEteams have shown that a rack and pinion type steering setup is the best choice for thistype of vehicle. For this reason, this section will focus mainly on two issues. The firstissue is the placement of the steering rack. The second issue is the material used tomanufacture the steering components, which include the rack and pinion, steeringlinkage, universal joints, and rod ends.

Rack Placement

High Mounted Rack

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Advantages

Mounting the steering rack high in the chassis allows for easy installation,maintenance and adjustment.

Mounting the steering rack high in the chassis makes eliminating bump steer easy,due to the fact that both the rack and the tie rod can be aligned with the uppercontrol arm.

Mounting the steering rack high in the chassis allows the steering rod from thesteering wheel to be straight, eliminating the need for a universal joint

Disadvantages

Mounting the steering rack high in the chassis can cause problems for the driverentering and exiting the vehicle, as the rack will extend the width of the chassisand present an opportunity for the driver to get their feet caught on the rackduring a quick exit from the vehicle.

Mounting the steering rack high in the chassis will effectively raise the vehiclestotal center of gravity. The lower some of the heavy components can be mountedthe better.

Mid Mounted Rack


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Advantages

NoneDisadvantages

Mounting the rack midway up the chassis will interfere with the drivers ability toenter and exit the vehicle in a timely manner

Mounting the rack midway up the chassis will make eliminating bump steerdifficult, since the angle that the steering tie rod must make is somewherebetween the angle of the upper and lower control arms. While this could be done,it would be difficult to perfect

Mounting the rack midway up the chassis would be unsafe for the driver in theevent of a collision. Since the rack is mounted in the same area as the driverslegs, an injury could easily occur from the drivers legs contacting the steeringrack.

Low Mounted Rack

Advantages

Mounting the rack low in the chassis eliminates the possibility for obstruction ofthe drivers quick exit from the vehicle in the event of an emergency.

Mounting the rack low in the chassis allows for easy elimination of bump steer,since the steering tie rod may be aligned with the lower control arm

Mounting the rack low in the chassis lowers the center of gravity of the vehicleDisadvantages

Mounting the rack low in the chassis requires the steering rod from the steeringwheel to travel through an angle such that a universal joint is needed

Material Selection

OverviewTwo materials were considered to make the steering components out of. These two

materials are 4130 Carbon Alloy Steel tubing and 6061-T6 Aluminum tubing. There aredefinite advantages and disadvantages associated with each. Examples are shown below.

4130 Carbon Alloy Steel

Advantages

Easy to weld, even for the amateur welder

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Readily available at a number of places, local and online Able to carry high tension and compression stresses Able to be purchased in large quantities rather inexpensively

Disadvantages

Heavy when compared to Aluminum6061-T6 Aluminum

Advantages

Very lightweight compared to steel Readily available Able to carry sufficient tension and compression stresses Able to be purchased rather inexpensively

Disadvantages

Very difficult to weld for the amateur welder Not as strong as steel

4.2.5 Final Selection

The first step in making the final selection for the 2007 Formula SAE vehicle steeringsystem was to eliminate some of the designs that will not work. This has been done in theprevious sections. Once eliminated down to a reasonable number of designs, a DesignSelection Matrix can be constructed. This matrix can be viewed below. As this worksheetshows, Welded steel tubing is the best material to use for the steering linkage. Thismatrix also shows that a low-mounted rack is best for our application. This design willallow for the best possible combination of packaging, strength, safety, dependability, easeof use, and ease of manufacturing. This design also allows for the high performancehandling characteristics that this vehicle will require, due to the convenient placement ofthe steering rack.

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DesignTrades

Engineering Metrics W

eights

Welde

A

luminum

WeldeSteel

MounteRac

MounteRac

MounteRac

1 Weight 3 3 12 Safety 9 3 9 3 3 13 Packaging 1 3 3 9 9 14 Ease of Manufacturing 3 3 9 9 3 35 Cost 3 3 96 Reliability 9 3 3 1789

101112131415

Rawscore

57

141

90

72

28

Relative

Rank 4 1 2 3 5

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4.3 Suspension A-Arms and Suspension Brackets


In order to navigate the autocross course quickly, the 2007 Formula SAE car needs tohave a well designed and adjustable suspension system. A key component of thesuspension design is the interface between the chassis and the suspension system. Thedevelopment of the suspension arms and suspension mounting brackets form animportant part of this system.


Brackets

2007 Formula SAE rules state that any threaded fastener used must meet or exceed SAE

grade 5, Metric Grade M 8.8, and/or AN/MS specifications. All fasteners must be securedfrom unintentional loosening by the use of positive locking mechanisms. Because thesuspension brackets will be fastened to the chassis as well as the suspension arms, theserequirements will dictate the design of the bracket. There are no specific rules for thesuspension bracket itself.

Unnecessary weight in racing can cost a car precious seconds around the race track.Selected materials selection is critical in keeping the weight as small as possible.Materials will need to be lightweight and withstand the rigors of racing. The bracketsalone will need to withstand up to 2 Gs of lateral force. Adjustability of the brackets is aconcern. All components of a well-designed suspension system have some degree of

adjustability.

Suspension Arms

2007 Formula SAE rules state that spherical rod ends must be in double shear orcaptured by having a screw/bolt head or washer with an O.D. that is larger thanspherical bearing housing I.D. Adjustable rod ends must be constrained with a jam nut toprevent loosening.

On each end of the suspension arm is a rod end. The length of these rod arms will need tobe adjustable so that suspension characteristics are controllable. Inside each of the rod

ends is a spherical bearing. This bearing allows the suspension arm to pivot up and downwhile attached to the suspension bracket. The height above and below the rod ends willneed to be adjustable.


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Brackets and suspension arms were benchmarked from a variety of different sources.Formula 1, single seat racers, and other Formula SAE race cars were all inspected fordifferent ideas. Mind map brainstorming generated new design concepts and attempted toimprove on previous designs. Several rough sketches were made of possible concepts.


After benchmarking and brainstorming, two potential design ideas were selected andfurther developed for the suspension brackets. Solid models of these designs werecreated. The middle-out bracket concept can be seen in figure 1. Figure 2 shows anadaptation on last years bracket. However, the support arms of the bracket of the newdesign are horizontal, instead of the previous vertical design. The suspension arm cannotrotate in the rod end when the supports are vertical. Last years suspension a-arms weremodified to have a more swept profile.

Figure 1. Bracket 1(Tyler Child) Figure 2. Bracket 2 (Tyler Child)

Figure 3. Suspension arm (Tyler Child)Material selection for the bracket was narrowed down to aluminum 6061. This alloy islightweight, strong, and easy to machine. Last years team left some blocks of this alloyfor our team to use so this helps to eliminate further costs. The suspension arms werebuilt from steel tubing. Steel was selected due to its high strength, ease in welding, andavailability.

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The potential design ideas were placed in a selection matrix. These ideas were weightedand scored against certain metrics. There were four different designs; the middle outbracket, the vertical support, horizontal support, and a circular base bracket. These

designs were compared in a QFD. The metrics of high importance were adjustability andsafety. Safety of the driver comes first. The car must pass several safety inspectionsbefore being allowed to compete. As previously discussed, all components need to beadjustable. The middle-out bracket, shown in figure 1, scored the highest and wasselected for the final design. After further refining, the middle-out bracket wascompletely modeled. The complete assembly, seen in figure 4, shows the mating of thebracket and suspension arm.

Figure 4. Suspension assembly (Tyler Child)

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4.4 Push Rod and Rocker Arm

4.4.1Problem definition.

In a formula racing car traction is essential to for the cars performance throughout all

maneuvers. In order to have optimal traction all four tires must maintain as much contactwith the ground as possible through bumps and turns. In order to achieve these results thesuspension must absorb the changes in height that the tires see. The final design alongwith how this design was chosen is outlined below.

4.4.2Requirements and Specifications.

Requirements for this system are for the movement of the wheel to be translated to shockefficiently. The pushrod needs to be able to hold the tensile and compressive forces fromthe wheel upright to the Rocker Arm. The Rocker arm needs to hold the same loads andalso provide a progressive transfer curve to the shock by decreasing the moment arm

through the motion.

Push Rod

For the push rod the requirements are that it has to be able to withstand the max loads thatit could see in operation with a factor of safety of at least 2. The loads that it will see arethe static weight of the vehicle divided by four along with impact loadings from bump.From the calculations mentioned previously the load to which it must withstand isapproximately 2500 newtons.

Rocker Arm

The Rocker arm is required to create a ratio of linear movement from the push rod to theshock. Because the total travel of the tire will be 75 mm and the shock travel is only 30mm the rocker input needs to be longer than the output side. Because the exact locationand mounting of the push rod are not yet determined this ration was undetermined;however, I created an equation that would find the ratio by simply inputting the angle ofpushrod to the horizontal ground plane at the ratio is then found can be input to solidmodel. It must also carry the same load as mentioned above.

4.4.3Concept Generation

Concept generation was performed by benchmarking standard automotive designs as wellas looking at previous designs from years past. There are as many different designs on themarket as there are applications for them. In choosing designs to be compared the mostdiverse where chosen first to make sure that wide spectrum of possibilities were covered.

Benchmarking

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In order to get a good idea of a design many different designs were examined fromseveral sources such as: general automotive designs, last years Formula SAE car, otheruniversities formula cars.

Shock w/ no pushrod

Picture: Guy Pannunzio

A standard rocker

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L rocker


4.4.4Design Refinement

Design refinement was done by creating a design matrix. The design matrix was createdwith seven critical metrics, from weight to aesthetics. These metrics were then weightedand scored for each of the preliminary design found by concept generation. The design

with the highest score was the winner and final design.

Metrics Weights

Straightbar

L-

bar

Shockonly

Torsion

bar

Manufacturing 3 12 9 12 3

Performance 9 18 27 9 9

Weight 6 12 18 24 6

Size 5 5 15 20 5

Rate 4 8 12 4 4

Aesthetics 4 4 12 4 8

Cost 3 6 6 12 6

Raw Score 65 99 85 41

4.4.5Final Selection

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Final design was a Pushrod/Rocker arm combination which will be used to actuate theshock by transferring the bump energy from the wheel.

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4.5 Impact Attenuator


The Impact Attenuator is an energy absorber device. Its purpose is to absorb as much

energy as possible in case of collision. It provides a load path for transverse and verticalloads in the event of off-centered and off-axis impacts.The design of this device requires consideration of the followings engineering metrics:

1. Low weight2. Small size3. Fire resistant4. Cost5. Energy absorption capability


The Formula SAE 2007 Rules handbook has the requirements and specifications of theImpact Attenuator, and these can be summarized as:

1. It must be attached securely to the front bulkhead of the car2. It must be able to absorb an impact of a 300 kg mass at 7 m/s with a deceleration

less than 20 G3. It must have a minimum size of 100 mm high, 200 mm wide, and 150 mm long


To explore different possible design concepts of the Impact Attenuator a mind-mapbrainstorm was made as seen in Figure 1. Four main materials were explored for making

the Impact Attenuator: foam, honeycomb, impact panel, and a composite.

Figure 1: mind-map brainstorm of four different materials

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Size Calculations:The following symbols will be used for the size calculations:m=massw=weight

G=decelerationg=gravityv=velocityKE=kinetic energyA=areaT=honeycomb lengthW=honeycomb widthH=honeycomb highs=stopping distancef=honeycomb crush strength

The collision situation between a mass and the Impact Attenuator is described in Figure3. The honeycomb material is CRIII, the cell size is 3/16, the alloy is 5056, the foilthickness is 0.001, and the density is 3.1.

Figure 3: mass and Impact Attenuator

Given:m=300 kgf=1.172x10 3 PaG=15v=7 m/sw=200 mm

First, the stopping distance is calculated and then the honeycomb length:

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ms

T

Ts

mgG

vs

gs

vG

240.07.0

%70

1666.015*8.9*2

7

2

222

2

==

=>=

===

=>=

Next, the kinetic energy is obtained, which will allow calculating the area and finally thehoneycomb high:

mw

AH

wHA

mfs

KEA

fAsKE

Nmmv

KE

190.02.0

0376.0

0376.01666.0*10*1172

7350

73502

7*300

2

2

3

22

===

=>=

===

=>=

===

Mass calculation:mass=rho*A*T=50*0.0376*0.24=0.456kg

The final characteristics of the design are:

1. Size: 0.240.200.19cm2. Mass=0.456kg3. Deceleration=15g

The final design is shown in Attachment 1, Figure 4 and Figure 5.

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Attachment 1

Figure 4: fiber carbon outer-shell

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Figure 5: honeycomb

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4.6 Engine Selection


This report focuses on the aspects of choosing a proper engine for the 2006 University ofUtahs Formula SAE competition car. It will include comparisons of various different

engines that were considered as well as the design selection for choosing the best possible

engine for this years car.

Summary

At the beginning of the semester it was decided that a new engine for this years car was

needed to keep up with newer technologies and be competitive. For this year we have

selected the engine from a Honda CBR 600 RR which complies with the size restrictions

applied in the formula SAE rule book. A picture of the actual engine that will be used inthis years car can be seen in Figure 1. Since this is a new engine all the modeling has to

be redone from last year for mounting points and size so chassis design team will know

how large to build the engine compartment to fit the new engine. Also a new drive train

assembly needed to be designed to fit on this engine meaning the alignment of the

mounting holes needed to be reconfigured on the side plate of this new engine.

Figure 1: Honda RR Figure 2: Honda F3

From a comparison of the two engines it is noticeable the more compact nature of the RR

compared to the F3 engine. Features of the RR include a larger angle on the cylinder

head which allows the exhaust manifold to drop vertically down, creating more space anda more compact design. Another key feature of the RR that is much better than the F3 is

that it is standard fuel injection, making tenability much easier.

Key features of this engine over the Honda F3 that was used last year is power increase,

weight savings, and more compact design.

1. Power increase =15 hp

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2. Total weight savings =5.3 lbs

3. Length minimization =3.5 inches


Engine

According to the Formula SAE rule book the engine for the car cannot exceed 610 cc per

cycle. Meaning two revolutions of the crankshaft cannot draw more than 610 cc worth of

air into the engine, otherwise a team will be disqualified. The engine however can be

modified within the restrictions of the rules. Also if a team were to use more than one

engine the total still could not exceed more than 610 cc and the air for both engines

would have to pass through a single air intake restrictor.

Engine InspectionOrganizers will measure or teardown a substantial number of engines to confirm

conformance to the rules. An initial measurement will be made externally with an

accuracy of 1 percent. A measuring tool may also be used which has dimensions of 15

inches long by 1.2 inches in diameter. Should this inspection show nonconformity to the

rules for engine size the team will be disqualified immediately.

System Sealing

The engine and transmission must be sealed to prevent leakage. Any crankcase or engine

lubrication vent lines routed to the intake system must be connected upstream of theintake system restrictor.

Separate catch cans must be employed to retain fluids from any vents for the coolant

system or the crankcase or the engine lubrication system. All the catch cans must have a

volume of at least 10 percent of the fluid being contained.

Cooling Limitations

Water-cooled engines must only use plain water, or water with cooling system rust and

corrosion inhibitor at no more than .015 liters per liter of plain water. Glycol-based

antifreeze or water pump lubricants of any kind are prohibited.

Fuels

During any part of the events the engine must be operated with the fuel provided by the

organizer at the event. Fuels will include 94 and 100 octane unleaded gasoline and E-85

which is an ethanol fuel.

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Fuel Temperature Changes Prohibited

Fuel Additives Prohibited

Air Intake and Fuel System Location RequirementsAll parts of the fuel storage and supply for the engine, and all parts of the intake system

for the engine must lie within the surface defined by the top of the roll bar and the outside

edge of the four tires. An example of the envelope can be viewed in Figure 3.

Figure 3: Air Intake Envelope


During the brainstorming process a mind map was used to open up ideas for all the

different types of engines that could be used for this project. Although there is not a lot

of concept generation involved in selecting an engine there are many aspects related to

how the engine performs that are concepts, such as the drive train and the intake system,

all from which has to be custom built for this engine. Concept sketches were made to

better understand what types of engine designs would work for this years car and can be

seen in Figures 4-7.

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Concept 1

The BMW boxer engine makes a very good platform from which to build a car out of, but

the major problem that you encounter with this type of setup is the engine mounting.

With this style of engine it makes mounting a transmission very difficult also because of

the way the crankshaft exits out of the engine.

Figure 4: BMW Engine

Concept 2

The Harley Davidson engine would be a fun engine to use but the vibrations from the

engine itself would cause extreme forces on the chassis and possibly cause handling

issues.

Figure 5: Harley Engine

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Concept 3

A single cylinder engine with a pretty good displacement would give good off the line

torque, but the major problem that you run into using this engine is it is not a four stroke

meaning the fuel economy and noise is going to be a rather large issue.

Figure 6: Honda Engine

Concept 4

The Honda CBR 600 RR is an ideal motor for a mini formula car because it creates

enormous power for its weight and size. The transmission output shaft also comes out

the side of the block making setups for the drive train rather simple.

Figure 7: Honda CBR Engine

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Design 1

The Honda F3 engine puts out reasonable power for its weight, but one of the major draw

backs to the engine itself is that it does not come fuel injected. With last years car they

converted everything to fuel injection meaning all the engine sensors had to be integrated

somehow in order to use the Motec engine management. Some good aspects about theF3 are existing knowledge and parts availability, since the F3 has been around for many

years prior to the RR almost any junkyard will have the F3 or parts for it. The F3 is also

more cost effective than the RR, but much more difficult to tune.

Figure 9: Honda CBR F3

Design 2

From the concept screening matrix the Honda CBR RR engine stands above the rest in

the most important categories mainly in reliability and size. Although the power rating is

not the highest, being that it is very light weight the power to weight ratio brings it to the

top of the list anyway. The RR is one of the more expensive engines to use in both theinitial cost and in parts, but for this project that is a good portion of what we are allotting

our funds to. The RR is also entirely aluminum with nickel coated cylinder walls making

it very light weight. Also the dimensions from the forward most point to the rear most

point is 3.5 inches shorter than that of the F3 and considerably shorter than the other

engines considered.

Figure 10: Honda CBR RR

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Using again a final design screening matrix the Honda CBR RR was chosen for the

engine to use in the 200607 Formula SAE car. A finalized drawing of the engine is

shown below along with dimensions and tolerances.

Figure 11: Honda CBR RR engine drawing

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4.7 Intake Manifold


The 2006 University of Utah Formula SAE team has been challenged to build anautocross race car that the weekend autocross racer can afford. To race this car inCalifornia at the FSAE West race the intake air for the engine must pass through a 20mmin diameter restrictor that is built into the intake manifold. The engine that we havechosen to use is a CBR 600 RR bullet bike engine. Because this engine is fuel injectedthe intake manifold needs to hold the fuel injectors and fuel rail. The OEM throttle bodyfor this engine has four throttling butterfly valves, one per cylinder. Since all the air mustpass through the same restrictor a new throttle body will be manufactured with only onethrottling butterfly valve. The intake manifold must fit within the profile created by themain roll hoop and the wheels of the car.


From the problem definition section the requirements and specifications of the intakemanifold are as follows:

Evenly distribute air to each cylinder Incorporate the 20mm restrictor Allow the maximum airflow pass the restrictor Incorporate mounting for the fuel injectors Lightweight Compact Easy to install

Intake Manifold OverviewIntake manifolds usually consist of a one or more throttle bodies controlling air flow tothe engine. The airflow then enters the plenum which is like a reservoir of air. When thevalve of any cylinder opens the air from the plenum quickly travels down the intakerunner to that cylinder. Because the air pulses into each cylinder instead of flowingsteadily over time it is necessary to have the storage of air in the plenum. Without an airstorage each cylinder would have to pull the air charge through the restrictor. Themaximum velocity of air through a venture is the speed of sound regardless of thepressure difference across it. The plenum allows the airflow through the restrictor to be

smooth rather than pulse allowing for a greater average air flow than without a plenum.

The intake runners in conjunction with the plenum forms a Helmholtz Resonator. AHelmholtz Resonator consists of a cavity (plenum) with a volume V, and an opening(intake runner) of cross sectional area A with length L. Basically a Helmholtz resonatoris like a coke bottle, the sound that it makes when you blow across it has a distinctfrequency. The sound is caused by the air moving back and forth trough the inlet of thecoke bottle. If the timing of the pressure wave of air is synchronized with the intake valve

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opening in the intake manifold. The air will be forced into the cylinder rather than drawnin by the piston causing an increase in power output of the engine. The frequency of aHelmholtz resonator is.

VL

AvfH

2= (1)

Where v is the speed of sound in air, A is the cross sectional area of the intake runner, Lis the length of the intake runner, and V is the volume of the plenum. Often for intakemanifolds the speed of sound in air v is multiplied by a constant that is less than 1 tocompensate for viscous effects in the runners.

Maximum mass air flow through the restrictorThe maximum mass air flow through the restrictor can be calculated from equation 2where A is the area of the restrictor, P0 is the atmospheric pressure, k is the specific heatratio of air, T0 is the ambient temperature of the air and R is the gas constant for air.

))1(2/()1(

0

0max1

2+

+=

kk

kRT

kAPm& (2)

From equation 2 the maximum air flow through the restrictor is 0.074kg/s. This massairflow rate corresponds to a pressure difference across the restrictor of 49.7% ofatmospheric pressure. Basically there will be 7.4psi vacuum in the intake manifold withan atmospheric pressure of 14.7psi. At this intake vacuum level the engine will stopproducing power and this will occur at about 14,800 rpm. Because of this we will governthe engine at about 10,500 rpm because above this we will only produce a small amount

of power.

Intake runner length and plenum volumeUsing equation 1 and choosing the desired rpm to tune the pulse of the intake manifoldwe get one equation with three unknowns, A, L, V. A good assumption to make is thatthe cross sectional area of the runners should be the same as the factory intake manifold,leaving only two unknowns. As previously stated the volume of the plenum (V) acts as areservoir of air, the larger the volume the smoother the airflow past the restrictor.However the length of the intake runner determines the mass of air resonating which inturn determine how much effect the pulse tuning will have on the power output. Wecould approximate the optimum V and L by using LTI system model techniques but for

now we just need to understand the dynamics of the intake manifold for the designrefinement.

Either concept 2 or 3 would be the best choice or maybe even a combination between thetwo. Based on this we will redesign an intake manifold to give us the best performance.


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After benchmarking different designs for intake manifolds both on production cars andother FSAE cars, different intake manifold designs were considered and only threedifferent designs met the requirements.

1. Concept 1 (small plenum)a.

Plenum is small and molds into the intake runnersb. Intake air has a smooth transition into the intake runners

c. Intake runners may be unequal length

2. Concept 2a. Plenum is simple and easy to manufactureb. Intake runners may be unequal lengthc. Possibility of adjustment in plenum volume

3. Concept 3a. Plenum can be any shape and size but cannot be adjustedb. Even air flow to intake runnersc. Intake runners could be changed outd. Intake runners are equal length

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From the previously stated information the intake manifold should have a tuned plenumand runner length. This excludes concept 1 which does not account for a plenum and hasdifferent length runners. Concept 2 would work very well for tuning the plenum volumebut the runners couldnt be easily tunable since they will probably be made from fiberglass or carbon fiber. Concept 3 would work for tuning the runner lengths and with aslight modification could possibly be used for changing the plenum volume.


The final selection was based on Concept 2 and 3 only with some modifications to unboltthe plenum from the intake runners for changing length and unbolting the restrictor for

access to the plenum for changing the volume. Also these changes are necessary forgetting the buck out of the part during assembly.

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4.8Rear Drive


Due to the considerable changes being made to the 2007 Formula SAE chassis, a

redesign of the rear gear-drive assembly was in order. For the past several years, the U ofU Formula SAE teams have used the same side plates and steel tube frame assembly tohouse the engine and final drive. However, this year the 2007 Formula team has decidedto employ a carbon fiber chassis which extends all the way to the rear of the vehicle.Therefore, the engine and rear drive assembly will need to mount directly to the carbonfiber, and a change in how the rear drive assembly is designed is required.


The 2006 Formula SAE vehicle utilized two side-plates which mounted the engine andthe rear drive assembly together, and connected them to the steel-tube chassis. For the

2007 car, we decided to incorporate a carbon fiber chassis which completely enclosed theengine compartment, rendering the previous side-plate design obsolete. Basically, therear drive housing needs to enclose the rear drive proper, which consists of the geardrive system (which is connected to the output shaft of the motor), and the limited slipdifferential (which is connected to the axles).

Original DesignThis sketch shows how the rear drive assembly was set up on the 2006 vehicle. The sideplates were attached on one side of the gear housing, and the far side of the axle housing.In this design, the entire axle was completely enclosed within the housing. Even whenutilizing the side plates, this isnt the most efficient design due to the extra material used

to cover the extended axle. When it comes to racecar design, the key is keeping itLIGHT. Also, due to the many mating surfaces fluid leaks were an ongoing problem withthis design.

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Sketch by E. Moellmer


Due to the fact that all of the systems on a Formula SAE racer are closely interrelated, avery close relationship must be observed between each of the different design teams.Because of this, the chassis and suspension team cooperated significantly during theinitial concept generation phase. The major issues which needed to be addressed were thelack of an easy mounting point (i.e. the side-plates) and the excessive amount of materialwhich went into the 2006 rear drive.

Mind MappingOne of the early brainstorming techniques used to generate ideas was mind-maps. Thistool facilitates a free-association of ideas, and is easy to read long after the exercise wascompleted.

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Sketch by E. Moellmer

Decision Matrix

Out of the many different ideas brainstormed by the group, the best were kept for further

refinement. One of the key ways the 2007 Formula SAE team decided on which ideas to

keep, was the use of QFD decision matrices.

Decision Matrix by E. Moellmer

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This decision matrix was used to narrow the most popular competing designs down tojust a couple (with the 2006 design as a reference). The Design Refinement section willaddress how these remaining concepts were handled.


It is at this point in the design process that the critical thinking really begins. Whereasbefore, the emphasis was on lots of varied ideas, now the focus shifts to ensuring that thefew ideas youre left with are sound. Using the methods outlined in the ConceptGeneration section, the candidate design ideas were whittled down to only two.

Final Competing Designs

Attached Differential Design

Sketch and Drawing by E. Moellmer

These photos show the gear drive housing attached to the housing for the differential. Theadvantages and disadvantages with respect to the Separate Differential design are listedbelow.

Advantages Lightweight design Fewer leak-prone surfaces More compact mounting

Disadvantages Fewer mounting options (geometry cant be changed) Un-even length axles, so the axle angle must be considered

Separate Differential Design

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Sketch and Drawing by E. Moellmer

From this sketch one can see how the housing for the differential is mounted separatelyfrom the gear box. This design has its own advantages and disadvantages, which neededto be weighed against those of the other competing design.

Advantages Modular mounting options (since geometry can change somewhat) Could keep both rear axles the same length

Disadvantages Prone to leaks (due to more mating surfaces) Heavier design (more parts, and extra axle shaft) More difficult to machine


The final ste

Formula Sae Final Report

Documents

Transcript of Formula Sae Final Report