Product Design Specification-REDESIGN OF THE OUTBOARD SUSPENSION-

Mechanical Engineering Design Team

Rick Rickert

Carole Gayley

Charles Larson

Efe Yıldırım

Jose Colin

Josh McCall

Industry Advisor: Evan Waymire

Academic Advisor: Dr. Lemmy Meekisho

ContentsProject Background.....................................................................................................................................3

Purpose of the Product Design Specification (PDS) Document....................................................................4

Mission Statement......................................................................................................................................4

Project Plan.................................................................................................................................................5

Customer Identification...............................................................................................................................5

Customer Interview and Feedback Summary..............................................................................................5

Design Criteria.............................................................................................................................................6

House Of Quality.......................................................................................................................................10

Technical Risk Management......................................................................................................................11

Risk Identification..................................................................................................................................11

Risk Assessment....................................................................................................................................11

Risk Mitigation.......................................................................................................................................11

Risk Monitoring.....................................................................................................................................11

Appendix A................................................................................................................................................13

Detailed Project Timeline......................................................................................................................13

Appendix B................................................................................................................................................14

Design Criteria Checklist........................................................................................................................14

Figure 1: Model year 2011 hub, showing complicated geometry and raw material used...........................3Figure 2: Model year 2011 hub, showing split plane mounting surface......................................................3Figure 3: Exploded view of the centerlock hub/wheel system prototype...................................................4Figure 4: House of Quality.........................................................................................................................10Figure 5: Technical Risk Management.......................................................................................................11Figure A1:FGantt Chart..............................................................................................................................13Figure B1:7Design Criteria Checklist..........................................................................................................14

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Project BackgroundDuring the 2010-2011 school year, the PSU Formula SAE team designed a new racecar from the ground

up. This car was raced in the 2011 Formula SAE Competition held in California. The new car had many

great improvements over the car raced in 2010. The outboard suspension was redesigned and featured

lighter uprights and a new hub. The outboard suspension of a race car consists of a hub, an upright and

the required bearings and installation hardware. For the 2011-2012 school year, the Formula SAE team

decided that the hubs and uprights were too complicated. Most machine shops were not willing to

build the hub which took hours to make and took a large chunk out of the team budget. The hub is

shown in Figure 1 and 2 below. An outboard suspension redesign would reduce the manufacturing

resources necessary to complete the outboard suspension. The new design would also provide an

opportunity to integrate a centerlock wheel retention system as desired by the Formula SAE team. In

June 2012, the FSAE team, racecar and improved outboard suspension will go to Nebraska for the

Formula SAE competition.

Figure 1: Model year 2011 hub, showing complicated geometry and raw material used.

Figure 2: Model year 2011 hub, showing complicated split plane mounting surface

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Shown in Figure 3 is the exploded view of the first revision prototype centerlock hub and wheel. From

left to right shown is the upright, hub, brake caliper, brake rotor, and wheel center. Not shown are the

wheel bearings, centerlock nut and clip, brake rotor bobbins, brake caliper fasteners and wheel shell.

Figure 3: Exploded view of the centerlock hub/wheel system prototype

Purpose of the Product Design Specification (PDS) DocumentThe purpose of the PDS document is to provide a defined goal for the FSAE Outboard Suspension Team

and provide measureable areas of achievement. The PDS document will be the written agreement

between the FSAE Outboard Suspension Team and the FSAE Team for what needs to be accomplished

during the 2011-2012 design year.

Mission StatementThe FSAE Outboard Suspension Team (FSAE-OS team) will design, validate and produce a new outboard

suspension that will weigh less, have a reduced part machining time and integrate a centerlock system.

The FSAE-OS team will produce all required drawings and BOMs along with a report of the design

decisions and FEA analysis used to produce the new system. Once the parts have been fabricated and

installed, the vehicle will be tested to verify proper functionality prior to June 2012.

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Project PlanThe FSAE-OS team will complete the project in a few major stages. Each stage will have a strict timeline

in order to meet the necessary dates. The overall stages are as follows:

Stage 1: Develop the PDS document, complete external and internal searches for design ideas and have

a conceptual design for both the hub and upright by February 2012.

Stage 2: Develop a detailed design and validate the design using engineering practices by March 2012.

Stage 3: Complete manufacturing, assembly and installation in order to begin testing by April 2012.

A detailed timeline (Gantt chart) has been provided in Appendix A.

Customer IdentificationThe primary customer for our outboard suspension design in the PSU FSAE team, and because we are a

sub-division of the FSAE team, our primary customer is internal. The secondary customer for this project

is the Portland State University Capstone Program. This external customer has a different set of

requirements for our project. They include proper documentation and design process in order to prove

our knowledge of proper design technique.

Our end product for the FSAE team will be physical parts that will help the team to win the FSAE

competition. The end product for the Capstone Program is proper documentation and test results to

verify our design.

Customer Interview and Feedback SummaryMultiple meetings were held with FSAE team leaders, Jack Slocum (Technical Advisor) and Evan

Waymire (Industry Advisor). In addition to formal meetings, ongoing email conversations were used in

identifying specific project goals. The result of these meetings and discussions was the decision to

redesign the outboard suspension. The new design is to decrease weight, decrease manufacturing cost,

decrease rolling resistance, and improve wheel mounting design. There was extensive discussion and

compromise during the process of forming the specific measurable design specifications. During the

discussion process the FSAE team made certain the goals set were reasonably obtainable, but still

provided an educational challenge to the outboard suspension design team. The specific product design

specifications agreed upon during the interview process can be seen below.

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Design CriteriaPerformance

Priority Requirements Primary Customer Goal Metric Target Target Basis Verification4 Hub weight FSAE Team Decrease weight Pounds 2lb Customer

definedPrototype

3 Rolling resistance FSAE Team Decrease Resistance Ft-Lb <1in*lb Customer defined

Prototype

4 Load capacity FSAE Team Withstand racing conditions

G 1.5 G lat/long 2G vertical

Customer defined

Prototype

ManufacturingPriority Requirements Primary Customer Goal Metric Target Target Basis Verification4 Ease of hub

manufacturingFSAE Team / manufacturing

Decrease complexity Machining time (min)

80 minutes Customer defined

Prototype

Life in ServicePriority Requirements Primary Customer Goal Metric Target Target Basis Verification2 Service life FSAE Team /

driverEnsure sufficient reliability

Operating life (years)

Minimum 5 year life Customer / group

FEA / prototype

SafetyPriority Requirements Primary Customer Goal Metric Target Target Basis Verification5 Centerlock nut

retentionDriver Keep the wheel on the

carOn/Off On Driver’s

safetyNut cannot be removed by using cotter pin

5 Factor of safety FSAE Team Safe operating range N/A 1.5 Driver’s safety

FEA

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EnvironmentPriority Requirements Primary Customer Goal Metric Target Target Basis Verification4 Operating

temperature range

FSAE Team Operate within operating temperature

°F 600°F Driver’s safety

FEA/ prototype

3 Operating environment

FSAE Team Operating in dust/water

N/A N/A Customer defined

Prototype

Maintenance and PartsPriority Requirements Primary Customer Goal Metric Target Target Basis Verification3 Wheel

bearingMechanic Ease of assembly Time and

tools required

No specialized tools/fixtures

Mechanic crew

Assembly

InstallationPriority Requirements Primary Customer Goal Metric Target Target Basis Verification5 Suspension link

connecting pointsFSAE Team Must provide same

geometry as 2011N/A N/A Customer

definedPrototype

5 Must interface with 2012 wheels

FSAE Team Must be able to mount 2012 wheel to the hub

N/A N/A Customer defined

Prototype

5 Drive axle FSAE Team Integration with existing equipment

N/A N/A Customer defined

Prototype

5 Floating Rotor FSAE Team Floating N/A N/A Customer defined

Prototype

3 Hub/wheel assembly

FSAE Team Easy to assemble Assembly time

Hub: <50minWheel: <1min

Customer defined

Prototype

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CostPriority Requirements Primary Customer Goal Metric Target Target Basis Verification3 Hub Cost FSAE Team Lower cost Dollars ($) $200/Hub Customer

DefinedMachine Shop Invoice

Production QuantityPriority Requirements Primary Customer Goal Metric Target Target Basis Verification4 Assembly

QuantityFSAE Team Sufficient Part Quantity Quantity

of assemblies

3 front and 3 rear assemblies

Customer Defined

Delivery Receipt

MaterialsPriority Requirements Primary Customer Goal Metric Target Target Basis Verification4 Hub Material FSAE Team Must be steel ANSI

Grade4340 Steel or similar Customer

DefinedPrototype

4 Upright Material FSAE Team Must be aluminum ANSI Grade

6061-T6 Aluminum or similar

Customer Defined

Prototype

DocumentationPriority Requirements Primary Customer Goal Metric Target Target Basis Verification4 Full Engineering

DocumentationFSAE Team Project must be fully

documentedN/A N/A Customer

DefinedSolidWorks CAD files

3 Installation Instructions

Mechanic Full assembly instructions

N/A N/A Customer Defined

Word Document

Rules and RegulationsPriority Requirements Primary Customer Goal Metric Target Target Basis Verification

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5 Must adhere to all FSAE rules and regulations

FSAE Rule Book Must pass tech inspection

N/A N/A Customer Defined

Prototype

Legal (Patents, Product Liability)Priority Requirements Primary Customer Goal Metric Target Target Basis Verification4 Minimize product

liability issuesDesign Team Avoid legal

ramificationsN/A Use practices to

minimize catastrophic failure

Design Team Prototype

4 No patent infringement

Design Team Avoid legal ramifications

N/A Design must be unique

Design Team Patent Search

AestheticsPriority Requirements Primary Customer Goal Metric Target Target Basis Verification2 Aesthetically

pleasingFSAE Team Must look well

engineeredN/A N/A Customer

DefinedPrototype

DisposalPriority Requirements Primary Customer Goal Metric Target Target Basis Verification1 Recyclable

MaterialFSAE Team Minimize Disposal Cost N/A N/A Customer

DefinedMSDS

TestingPriority Requirements Primary Customer Goal Metric Target Target Basis Verification5 Must complete

testing sequence before first use

FSAE Team Verify assembly integrity

Hour 4 Design Team Complete Testing Checksheet

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House of Quality

Critical design parameters are identified and targets were set through benchmarking against other outboard suspension designs. A summary of these comparisons is shown in the house of quality shown in Figure 4 below.

Customer Needs

Hub

Cost

($)

Hub

Mac

hini

ng

Tim

e (m

in.)

Hub

Wei

ght (

lbs)

Asse

mbl

y Ti

me

(min

)

Num

ber o

f Lug

s

Life

(yea

rs)

2011

PSU

FSA

E O

utbo

ard

Susp

ensio

n

2010

PSU

FSA

E O

utbo

ard

Susp

ensio

n

Tayl

or R

acin

g O

utbo

ard

Susp

ensio

n

1. Performance Driver Handling2. Ease of Manufacturing FSAE Team 2 **** ** * ** ****3. Ease of Assembly FSAE Team 1 * **** * ** ***4. Ease of Use Speed of Tire Changes5. Production Cost FSAE Team 1.5 **** ** * * ** **6. Life In Service FSAE Team 0.5 **** **** **** ***

7. SafetyDriver, FSAE Team 2 *** *** ****

200 120 3.1 60 4 5

35 0 4 40 4 10389 0 4 30 1 5200 80 2 50 1 5

Invoice Test Test Test Inspection Test

**** - Strong Correlation* - Weak Correlation

FSAE Outboard Suspension: House of Quality

Market Competition2011 PSU FSAE Outboard Suspension

2010 PSU FSAE Outboard SuspensionTaylor Racing Outboard Suspension

Target

* * *

** ****

End

Use

r

Impo

rtan

ce

Engineering Criteria Market Competition

**

Defined by Competion Rules

Verification

** ** *

****FSAE Team

2

1

Figure 4: House of Quality

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Technical Risk Management

Frequent Likely Possible Unlikely RareCatastrophic Extreme Extreme High High ModerateSevere Extreme High High Moderate LowMarginal High Moderate Moderate Low LowNegligible Moderate Low Low Low Low

Missed delivery date Parts undersizedParts cost too high

Figure 5: Technical Risk Management

Risk Identification The parts cost too much The team is unable to deliver parts on time The parts are improperly sized

Risk Assessment Frequently manufacturing costs are higher than first estimated, but the consequence is

marginal. The team can rearrange the budget. The probability of not meeting deadlines is likely and the consequence is severe. Without parts,

the team can’t compete. The probability of the parts being undersized is possible and the consequence would be

catastrophic. Driver injury could result.

Risk Mitigation The parts will be designed with simplicity in mind. The team will review the parts before being

machined and get quotes in writing. The team will follow tight timelines using the Gantt chart found in Appendix A.

Interchangeability with previous models is maintained. Detailed FEA and extensive on vehicle testing will be done before the car is released for use.

Risk MonitoringBy watching timelines, getting written quotes and performing careful testing of the car, we

expect to maintain a reasonable level of risk during our project.

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ConclusionThe goal of the Portland State Formula SAE team for 2012 is to improve racing performance while maintaining car reliability. To achieve these goals an outboard suspension redesign proved necessary. It is the desire of the FSAE Outboard Suspension team to implement a centerlock hub design to aid in reducing weight while reducing the complexity of the machined parts. By reducing the complexity of the machined parts, the machining time will be reduced which will result in a lower cost end product.

Though the goals and targets of the project are clear, there are many challenges to overcome. The largest of the foreseen difficulties are the high rotational bending stresses in the hub. Heat transfer from the break system into the outboard suspension components will require in-depth analysis. With unknown amounts of heat transfer and variations in thermal expansion between the various materials, press fits will be difficult to determine. These challenges will be overcome using knowledge gained through the mechanical engineering curriculum and advise of experienced professionals.

.

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Appendix A

Detailed Project Timeline

PDS

PDS

Pres

enta

tion

Inte

rnal

Sea

rch

Exte

rnal

Sea

rch

Conc

ept S

elec

tion

Deta

il Des

ign

Prog

ress

Rep

ort

Man

ufac

turin

g

Asse

mbl

y an

d Te

sting

Fina

l Pre

sent

ation

s

Fina

l Rep

ort

Inte

rnati

onal

FSA

E Co

mpe

tition

30-Jan8-Feb

15-Feb22-Feb

12-Mar21-Mar

16-Apr

1-Jun6-Jun

20-Jun

Team Members Member TotalsRick 20 10 10 10 5 40 5 5 40 10 30 30 215Carole 5 2 10 10 5 30 20 5 60 20 20 30 217Josh 5 2 10 10 5 50 15 5 40 15 30 30 217Chip 20 10 10 10 5 30 5 5 40 10 40 30 215Jose 5 2 10 10 5 40 15 5 40 20 30 30 212Efe 5 2 10 10 5 40 20 5 40 20 30 30 217Task Totals 60 28 60 60 30 230 80 30 260 95 180 180 1293

Figure A1:FGantt Chart

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Appendix B

Design Criteria Checklist

Criteria PageAesthetics 9Disposal 9Documentation 8Environment 7Installation 7Legal 9Life in Service 6Maintenance 7Manufacturing 6Materials 8Performance 6Product Life Span 7Production Cost 8Quantity 8Rules and Regulations 8Safety 6Testing 9Weight See Performance

Figure B1:7Design Criteria Checklist

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