Designing a BAJA SAE Vehicle 3-10-2007!7!12 24 PM

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SAE TECHNICALPAPER SERIES 2000-01-2651

Rethinking the Design Paradigm:A Customer-Focused Approach to

Designing a Mini-Baja Vehicle

Brent Zollinger and Robert H. ToddBrigham Young Univ.

International Off-Highway & PowerplantCongress & ExpositionMilwaukee, WisconsinSeptember 11-13, 2000

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2000-01-2651

Rethinking the Design Paradigm: A Customer-FocusedApproach to Designing a Mini-Baja Vehicle

Brent Zollinger and Robert H. ToddBrigham Young Univ.

Copyright © 2000 Society of Automotive Engineers, Inc

ABSTRACT

This paper uses a case study to demonstrate howfocusing on customer needs improves the success ofproduct designs in the marketplace. A sampling oftrends in modern design is presented, showcasing somemethodologies that facilitate effective design. The workof the Brigham Young University mini-baja vehicle designteam is studied. The team used a customer-focuseddesign by developing the product specification directlyfrom customer statements, and using matrices toevaluate the capacity of concepts to meet thespecification. Lessons learned from the design processare considered.

INTRODUCTION

A BYU Capstone design team—composed ofmechanical and manufacturing engineers, engineeringtechnologists, and an industrial designer—designed avehicle for competition in the Mini-Baja West competitionsponsored by SAE. Mini-Baja is an intercollegiate designcompetition where teams of undergraduate studentsdesign, build, and race a "one-person, four-wheeled,recreational vehicle [1]." The vehicles must be poweredby an unmodified 5.97 kW (8-hp) engine and have aproduction cost of $2,500 or less if produced in 4,000annual units. Vehicles are judged on sales, design,safety, and cost; they are also raced to determineperformance capability in acceleration, hill climb,maneuverability, and four-hour durability. To ensure thevehicle would perform well in competition and becompleted in time, structured design methods were usedto define customer needs, create the productspecification, and make conceptual design decisions.Detail design decisions were made using traditionaldesign procedures.

Design is a term that can connote a number of differentmeanings. New engineers often enter industry with theidea that design is only concerned with product function[2]. The product realization process (also known as totaldesign and product design and development) is a catchphrase that refers to a holistic view of the designprocess. The term design in this paper refers to thisholistic view. Design from this point of view is a cycle of

information processing and decision making with theobjective of meeting the needs of customers andstakeholders throughout the entire product life cycle.The design is successful when it achieves a balancebetween factors—such as cost, performancespecifications, tooling, ecology, etc.—which best meetthe needs and wants of all the customers andstakeholders [3]. A good design concept has atremendous effect on the overall success of the product.It is estimated that more than 70% of the life cycle cost ofa product is determined by the design [4].

In 1991 the National Research Council published areport indicating, "The overall quality of engineeringdesign in the United States is poor." And, "The bestengineering design practices are not widely used in U.S.industry [4]." Engineering design in the U.S. lags behindcompetitors in addressing customer needs, decreasinglead-time, and accounting for the entire product lifecycle, including manufacturing, customer use, disposal,and life cycle costs [5].

To stay competitive in coming years, practicingengineers will be required to rethink their designprocesses. They must become more involved inresearching the needs and wants of customers andstakeholders (hereafter referred to as “customer needs”).It is hoped that the case study presented here will helppracticing engineers understand the effects of focusingtheir design processes around meeting customer needs,and become familiar with some of the methodologiesthat can help facilitate this objective.

THE CUSTOMER FOCUSED DESIGNPARADIGM

A large part of industry uses an outdated designparadigm, in which engineering designers act as problemsolvers who optimize designs to meet specifications theyhave been given by others. Generally, they design insidetheir knowledge base, not considering a broad spectrumof alternatives. Frequently a mathematical model is usedto decide upon values for design parameters. It isbelieved that the best possible design has been createdbecause it has been optimized within the mathematicalmodel. However, according to Pugh, over 95% of thesedesigns fail in the market place [6]. His researchindicates the vast majority of market failures occur

because the product specification does not accuratelyreflect customer needs [6].

The new customer-focused design paradigm encouragesengineering designers to participate in market research,and consider a broad range of concepts. They focusefforts on identifying and meeting customer needs beforeoptimizing design parameters. This type of workrequires not only analysis, but also synthesis andcreativity. Design engineers work concurrently withmarketing and production specialists, continually strivingto improve designs. Continuous improvement in designis desirable since an “optimum” design is never possiblein a dynamic marketplace.

Despite the large array of design strategies that attemptto simplify design processes into a series of calculations,design is still very much an intuitive and creative activity[7]. Many design considerations require the use ofsubjective judgement. Because of this, optimizationtechniques may create a false sense of security, sincethey often ignore or inaccurately reflect importantsubjective design parameters, and may miss somecustomer needs. Also, optimization requires complexsystems to be broken down into smaller components.When the small components of design are optimized theresult is suboptimization of those components, often atthe expense of the design as a whole system. Whileoptimization strategies are a key to good design, theymust be used with wisdom.

Generating revenue is the primary reason for designingand manufacturing products. Revenue increases as thecustomers’ perception of value increases. Meeting theneeds of every potential customer is difficult, since theneeds of individual customers often vary and may evenchange over time. A successful product must not justmeet the needs common to most customers at thebeginning of the design process; it must have a shortlead-time and be versatile enough to meet the needs of avariety of customers, even as those customers maychange. Remember, the term customer is not limited tothe end user, but includes all product stakeholders, suchas marketing, production, and legal departments, theenvironment, and so on.

THE DESIGN PROCESS

The key to ensuring successful customer-focused designis using an appropriate design process. There are asmany processes as there are design teams. Eachcompany must establish and refine a process that worksto meet their situation [4]. In all cases, product design ismost effective when done in multidisciplinary teams.However, the development process may include anycombination of design tools and strategies, such as 3-Dmodeling, DFX, QFD, life-cycle analysis, functionmorphology, selection matrices, FMEA, or Taguchimethods [2,4,8,9,10].

The design methodology used by the BYU Mini-Bajadesign team focuses on satisfying customer needs. Thecustomer needs identified by the team are a product ofdetailed market research, and must be converted into aproduct specification that accurately reflects those needsin order to ensure a successful design. Concepts areevaluated using screening and scoring matrices, whichjudge the capacity to meet those specifications. Thequality of the concepts selected with matrices is

dependent on the chosen judging criteria, and the weightthat criteria are given [3].

The design process used by the BYU team was adaptedfrom Ulrich and Eppinger’s concept development model,as seen in Figure 1 [8]. The design process does notinclude steps for preparing tooling and production sinceonly one vehicle, a prototype, would be made. The stepsmost critical for ensuring a customer-focused designwere included. However, market research focused oncompetition requirements rather than consumer studiesbecause our end market was more oriented to the SAEMini-Baja West competition than the retail market.

To ensure the success of a structured designmethodology, care must be taken to foster anenvironment conducive to design. Providing ample timefor team communication and empowering teammembers with applicable resources encourages effectiveteamwork. In interdisciplinary teams, each membershould be a specialist in their field and have backgroundknowledge spanning other design fields [2].

Figure 1: Design process model used by BYU Mini-Bajateam. Adapted from Ulrich and Eppinger.

A CASE STUDY IN PRODUCT DEVELOPMENT:MINI-BAJA VEHICLE

Developing skill in design is best learned throughexperience. Case studies are an effective way to helpconvey lessons learned through experience to studentsof design. There is a danger in learning design throughcase studies however, since they must be presentedsequentially when documented, giving the reader theillusion that the design process is sequential rather thansimultaneous and iterative [9]. The case study

IdentifyCustomer

Needs

EstablishSpecifications

AnalyzeCompetitive

Products

GenerateProduct

Concepts

Select aProductConcept

Detail Designof Concept

PreliminaryAnalysis ofConcepts

AdvancedAnalysis andPrototyping

Cost Analysis

BYU Mini-Baja Team Design Process

presented here is used to showcase an example of oneteam's attempt to incorporate customer-focused designmethodologies into the design process.

The Brigham Young University 1999 Mini-Baja teamused a customer-focused methodology to design an off-road vehicle for the SAE Mini-Baja West competition.Focus was placed on meeting customer needs by givingthe multidisciplinary team of engineers the responsibilityfor performing market research. The team derived theproduct specification directly from the findings of theirresearch. Concept generation and selection processeswere focused on meeting the criteria required by theproduct specification. The early stages of the designprocess of the Mini-Baja vehicle provide an effectivemeans of studying the impact of the customer-drivenapproach to design. Competition of the vehicle at theMini-Baja West competition provides a mechanism fordetermining design strengths and weaknesses in acontrolled “marketplace.” For the team to win thecompetition, they must understand the needs of thisartificial “marketplace” and use a design process that isappropriate for the product and its market.

DEFINING CUSTOMER NEEDS The team’s maindesign goal was to produce a vehicle that met all of theneeds of the product stakeholders, especially the enduser, BYU’s Mini-Baja racing team. In order to identifyas many customer needs as possible, team membersinterviewed previous race participants, studiedcompetition rules, and reflected on personal desires forperformance. Direct statements from these sourceswere recorded and classified into a hierarchy. Thesecustomer statements were converted into statementsthat expressed product attributes clearly and in detail.Rankings were assigned to each product attribute toindicate its importance. Some of the desired attributesand their importance rankings are found in Table 1. Asignificant amount of time was taken to ensure the list ofproduct attributes reflected the true needs of customers,and that rankings accurately reflected customerpriorities. Putting together the list of product attributeswas done as a team, so the input of everyone thatparticipated in the research was available.

ID # Product Attribute Rank1 The vehicle is safe 52 The vehicle adheres to competition rules 53 The vehicle is fast 54 The vehicle accelerates quickly 55 The vehicle can climb steep hills 46 The vehicle is reliable 47 The vehicle is inexpensive 38 The vehicle is light weight 39 The vehicle is comfortable and fun to drive 3

10 The vehicle is stable 311 The vehicle is easy to service 212 The vehicle looks good 2

Table 1: Abridged list of vehicle attributes, indicating theirimportance to customers by a ranking on a 1-5 scale.

CREATING THE PRODUCT SPECIFICATION Amajor key to any successful design is generating aproduct specification that accurately reflects customerneeds and desires. Unfortunately design engineers donot always participate in the creation of the specification,

nor do they try to improve it. The specification shouldstate constraints as broadly as possible to avoidpremature elimination of possible concepts [10]. In ourcase, many constraints were imposed by the detailedrequirements of the competition rules. The 45 productspecifications the team created were classified as beingrelevant to the entire vehicle, including major sub-assemblies of the vehicle such as the frame,suspension, powertrain, braking, and steering sub-systems. The 12-member team was divided into sub-teams that were responsible for the design of each ofthese major sub-systems. Time was allotted for the sub-teams to communicate their intentions with the rest ofthe team. This communication helped in selecting sub-system concepts that could be neatly incorporatedtogether as a total system or vehicle.

An abridged specification, consisting of a metric, testprocedure and ideal value range, is found in Table 2.Each specification was taken directly from a productattribute, which is referenced by number. It is importantthat specifications reflect customer needs and desiresaccurately so compliance to the specification assuresmarket success of the product. Some specificationscannot easily be defined numerically. To enableevaluation of such specifications, a subjective rating wasused.

It is not uncommon for inexperienced designers to createproduct specifications that are worded in such a way asto prematurely eliminate possible solutions andincorrectly reflect complex design issues [10]. Theyoung BYU design team was no exception. Some teammembers felt the creation of the product specificationwas just a hoop to jump through, largely because theywere anxious to get to the decision-making designphase. One failure of the specification was meetingproduct attribute #10, which requires the vehicle to bestable. The specification required that the vehicle couldbe tilted a large angle statically on two wheels before itwould tip over. The team exceeded the requirementgiven in the specification, producing a design that couldbe tilted over 60º before tipping over, but the car still hadsome instability problems because the specification didnot take into account all of the suspension characteristicsnecessary for dynamic stability. A better specificationwould have been to require the vehicle to complete a U-turn of a 10-foot radius at a specified speed without thewheels leaving the ground. This specification wouldallow for more design freedom by testing all parametersthat contribute to stability simultaneously, rather thanindividually.

Product attribute #4, which requires quick acceleration,was converted to a specification inaccurately becausethe test method timed the vehicle on pavement, not ondirt as would be required in the race. While the vehicleperformed well on pavement, it did not do as well in theoff-road acceleration contest because there was notample brake friction on the rear axle to power brake atthe starting line, increasing times by half a second. Hadacceleration been tested off-road, the problem couldhave been corrected before the competition.

Even with shortcomings in the product specification, itwas a valuable aid to help focus the design on customerrequirements. Knowing how well the design measuredup against the specification indicated roughly how wellthe vehicle would do in its market—the competition.Confidence in a product requires both that the product

meets the specification and that the specificationaccurately describes customer needs. Since theshortcomings in the specification were relatively minor,they did not prevent the design from being successful.

CONCEPTUAL DESIGN Conceptual design wasdivided into sub-systems: frame, suspension, powertrain,braking, and steering. This division of responsibilityhighlighted the importance of communication betweenthe designers of the different systems. The decisions ofone sub-team affected the decisions of another.Constant communication was required so completevehicle concepts didn’t optimize one system at theexpense of others. For instance, tests performed by thepowertrain designers showed that using a differentialwith a small housing would increase track speed, but therear suspension concept that was chosen by otherdesigners would put too much stress on the smalldifferential housing selected. This problem required thesuspension and powertrain designers to work together tocome up with a solution that would allow for synergybetween the two systems. Working together thedesigners found that a trailing arm suspension designcould be set up so that one of the rear wheels wouldunload around turns, allowing it to spin freely. Thisdiscovery allowed a low-cost solid axle to be used inplace of the differential without eliminating the benefits

the differential would have provided. Through thislesson, the team learned that unnecessary divisions indesign responsibility are undesirable because theyrequire more iterations to ensure a successful compositedesign.

Designers used screening and scoring matrices toensure that a range of concepts was considered and thatthe chosen concept was the best alternative. Screeningmatrices ranked a large number of concepts, judgingeach to be better than, equal, or worse than abenchmark concept when evaluated against a series ofselection criteria (see Table 3). Scoring matrices wereused to further compare the concepts that faired well inscreening. For scoring, concepts were assigned anumerical rating for each of the weighted criteria, asshown in Table 4. The outcome of these matrices ishighly dependant on the criteria used to evaluate them,and the weight assigned to each criterion. Appropriatecriteria were determined by considering customer needsas stated in the list of attributes and the productspecification. A benefit of scoring matrices is that theydiscourage designers from jumping to a solutionunnecessarily. Young engineers, especially, have atendency jump to complicated or “high-tech” solutions[11].

Ref # Metric Test Procedure Target Values(Ideal–Acceptible)

1 Number of belts, chains, andsprockets without guards

Observation 0 – 0

Amount of fuel lost in rollover Turn vehicle upside down and look for drippingfuel.

0 – 2 drops

Stiffness of roll-cage material Calculate EI product of tubing 1,500 ksi – 760 ksiNumber of driver-restraintpoints

Observe number of harness attachment points 5 – 4

Distance to stop car from topspeed

Measure distance to stop from 50 yard accelerationon dry pavement

15 ft – 30 ft

2 Number of rules broken Race judges determine number of rules violated 0 – 03 Top speed Instrument vehicle with speedometer 50 mph – 30 mph4 50 yard drag race time Time 50 yard drag race on level pavement 6 sec. – 7.5 sec5 Climbable hill angle Drive vehicle up hills on hard-pack 35º – 22º6 Hours of driving without

failureTime hours driven since last design change orrepair

50 hrs. – 5 hrs.

7 Cost to manufacture vehicle Estimate cost based on 4,000 production unitsfollowing Mini-Baja guidelines for costing

$2,300 - $2,499

8 Curb weight Weigh vehicle 350 lbs. – 450 lbs.9 Ride smoothness rating Drivers will determine rating subjectively (1-10) 10 – 6

Size range of drivers that canfit into vehicle

Drivers of different heights will attempt to drivevehicle

4' - 6'10" –4'8" - 6'6"

Ease of steering rating Drivers will determine rating subjectively (1-10) 10 – 510 Angle of tilt when vehicle is

balanced on two wheelsTip vehicle with driver on two wheels and measureangle of frame with angle finder.

60° – 40°

11 Ease of service rating Team mechanics will determine rating subjectively(1-10)

10 – 4

12 Aesthetic allure rating Industrial designer will determine ratingsubjectively (1-10)

10 – 4

Table 2: Abridged list of product specifications including: metric, test procedure, and target value range.

The concept selection process for the frame/roll-cageresulted in a very successful design. The originalconcept drawing, drawn by the industrial designspecialist on the team, can be seen in Figure 2.Manufacturing engineers were excited about the

aesthetic appeal of the concept drawing and also foundthat the frame could be made more easily than otherconcepts. The final frame design uses relatively largediameter tubing: 1.5-inch diameter, .035-inch wallthickness, 4130 alloy steel. The tubing is much lighterand stiffer than other options, making it difficult to bend in

Frame Concept Screening MatrixA B C D E F

Selection Criteria

Varia

nt o

fLa

st Y

ear’s

Mod

el

New

Con

cept

1

New

Con

cept

2

New

Con

cept

3

New

Con

cept

4

Last

Yea

r’sM

odel

(Ben

chm

ark)

Conforms to rules 0 0 0 0 0 0Easy to exit 0 0 - - 0 0Fit all team members + + + + + 0Aesthetically pleasing 0 + - - - 0Comfortable to drive + + 0 0 0 0Manufacturability 0 + - - - 0Weight 0 + - 0 - 0Sum +'s 2 5 1 1 1 0Sum 0's 5 2 2 3 3 7Sum -'s 0 0 4 3 3 0Net Score 2 5 -3 -2 -2 0Rank 2 1 6 4 4 3

Table 3: Screening matrix used to narrow field of concepts. Concepts were compared against a benchmark (F). Concepts inbold were considered further in the scoring matrix.

Frame Concept Scoring MatrixF A B

Last Year’s Model(Benchmark)

Variant of Last Year’sModel

New Concept 1

Selection CriteriaWeight

(%)Rating Score Rating Score Rating Score

Conforms to rules 20 3 0.6 3 0.6 3 0.6Easy to exit 10 3 0.3 4 0.4 4 0.4Fit all team members 10 3 0.3 4 0.4 5 0.5Aesthetically pleasing 15 3 0.45 5 0.75 5 0.75Comfortable to drive 10 3 0.3 4 0.4 4 0.4Manufacturability 15 3 0.45 4 0.6 5 0.75Weight 20 3 0.6 5 1.0 5 1.0

Total Score 3 4.15 4.4Rank 3 2 1

Continue? No Backup Choice Develop

Table 4: Scoring matrix used to decide upon primary and secondary concepts.

small radii. This obstacle was overcome by using tubesbent in large 130-inch, and 70-inch radii. The large radiican be bent easily on a three-point roller bender beforecutting to length. This solution not only eliminates theneed for local bends; it provides aesthetic appeal,provides more room for the driver and powertraincomponents, and lightens and strengthens the frame byeliminating several welded joints.

Upon examination of the selection matrices in Tables 3and 4, one important criterion appears to be absent—rollover protection. The main function of the frame/roll-cage assembly is to protect the driver in the event of arollover, so it would be natural to include it as a primaryjudging criterion. However, rollover protection is includedin the "conforms to rules" criterion. Safety rules for theMini-Baja competition specify minimum strength andstiffness requirements for the tubing used, and alsoindicate the location and number of certain tubemembers [1]. While these safety rules all but guaranteesafety for the race participants, they do eliminate a largerange of alternate concepts that would provide amplerollover protection.

Conceptual design of the powertrain differed greatly fromthat of the frame. Many concepts were studied, andmost of them had previously been used in thecompetition by other teams. Research and analysis wasperformed to identify the strengths and weaknesses ofeach design. The screening and scoring matricesenabled the designs to be evaluated according to thecriteria that were established by customer needsresearch. The concept that was selected consists of acontinuously variable transmission (CVT) driving the rearwheels through a gearbox transmission and a chainreduction. The gearbox transmission adds two speedranges and a reverse gear to the CVT, whichautomatically adjusts its gear ratio depending on enginerpm and torque resistance of the gearbox input shaft.This concept was determined to be the least risky choicebecause the shift-on-the-fly gearbox transmissionincreased the gear range to exceed customer needs fortop-speed and also hill-climbing performance. Thesecond gear range was a critical factor in allowing thevehicle to place in the top three in the hill-climb event ofthe competition. The chain reduction was required to getthe overall gear range low enough for the 5.97 kW (8-hp)engine, and to allow for gear range adjustably through achange in rear tire diameter choice.

Since the power-source is limited by the competitionrules, the rest of the powertrain must manage the limitedpower to achieve the desired specifications.Mathematical models and benchmarking were used to

determine appropriate gear-ratio ranges. Powertrainconcepts were created in conjunction with suspension,frame, and braking to take advantage of anyopportunities for function integration. For instance, thedrive axle incorporates an inboard disk brake and acts asa suspension member in the trailing-arm rearsuspension. A single, non-telescoping, universal joint oneach side of the axle allows it to move with thesuspension. Axial motion of the rear axle is prevented bymounted bearings, placed directly inboard of each U-joint, which transfer thrust loads to the frame. Figure 3shows a shaded Pro/Engineer CAD model of thepowertrain components.

DETAIL DESIGN During the conceptual design stagethe design team amassed a list of hundreds of detaildesign questions that had to be answered. By this stage,the major components and concepts had already beenfinalized. Remaining questions included such details as,“What bearings should be used on the front wheels?”“What diameter should the steering wheel be?” and “Howshould the throttle connect to the pedal?” The marketsuccess of products greatly depends on the quality ofdetail design [12]. The vehicle excelled in some areasdue to good detail design, but poor detail design in otherareas prevented the vehicle from winning thecompetition. A major factor in the quality of the detaildesign is the design methods used. Some detail designwork required standard engineering analysis techniques,some required good intuition and judgement, and somerequired critical concept selection.

Figure 2: Frame concept drawn by industrial designstudent Josh Thurber. This concept is referred to inmatrices as “New Concept 1.”

Figure 3: Shaded Pro/Engineer model depicting thelayout of powertrain components.

Pro/Engineer, a solid-modeling software package, wasused extensively in both the conceptual and detail designstages. The software allowed for various designiterations to occur quickly. It also was used to work outassembly details and clearances. One of the mainbenefits of virtual design is facilitation of communicationbetween designers. The creation of the solid modeloccurred before construction began, facilitatingsimultaneous design of the separate sub-systems.Designers of the separate sub-systems worked outassembly and interface issues early, resulting in lesstime lost due to useless iterations. CAD models wereused for the design of major detail, and were not used forless-significant details.

When deciding what bearings should be used on thefront wheels, standard engineering analysis techniqueswere used. Loads that would be imposed on thebearings were calculated and the desired life to failurewas decided. Bearings were then selected using theselection procedures recommended by the bearingmanufacturer. Selecting the bearings was a traditionalengineering problem, and the bearings performed well,as predicted.

The design of the steering wheel did not require anyengineering calculations, rather it was an exercise ofintuitive judgement. Since the wheel would be rotatedover 180° to either side, a traditional circular style waschosen, as opposed to a butterfly or ¾ circle. Twodiameters were readily available: 25 cm (10 in.) and 36cm (14 in.). The 25 cm diameter steering wheel waschosen to allow more room for drivers to enter and exitthe vehicle. It was also judged that the car was easyenough to steer that a larger lever-arm wasunnecessary. Even though using intuitive judgement asa design tool involves some risk, it can never be avoidedin any design task. Risk can be reduced when a largersampling of people are used to give subjective input, andwhen multiple prototypes are constructed for testing. Inthis case, two alternatives where considered as well asthe opinion of most of the potential drivers. As a result,the steering wheel performed very well, and wascomfortable for all of the drivers.

Designing the link between the engine throttle and theaccelerator pedal required generating and implementinga concept. The novice designers felt this linkage was a

detail, and left its design to intuitive judgement, a detaildesign method. In theory this concept should have beendecided following the procedure described previously inthe Conceptual Design section. A bicycle brake cablewas used as the link because that was the firstreasonable concept the designers thought of. Noanalysis was done on the cable because the designerswere not familiar with applicable analysis techniques,and judged that the cable would be under similarstresses as on a bicycle. The design failure occurredwhen the cable attachment points were decided upon atthe last minute. The attachment point at the pedalconsisted of a bolt and washer. The washer wasmodified with a groove for the cable to seat in. When thebolt was tightened, the washer pressed the cable againstthe pedal to secure it. This attachment point was locatedat the bottom of the pedal to allow concealment of thecable assembly. Since the pivot of the pedal was locatedtowards the bottom, the cable was pulled along an arcwith a 5 cm (2 in.) radius when the pedal was actuated.This radius proved to be too small, forcing the cable tobend at the bolt from 0º to 90º along the throw of thepedal. This bending caused a fatigue action that causedthe cable to fail after only 20 hours of service.Unfortunately, the failure occurred in the beginning of thedurability competition.

The failure of the throttle cable took the vehicle out ofcontention for first place, and the vehicle finished 12th outof 72 registered entrants. Previous to the durabilityportion of the race, the vehicle was 5th overall, andbefore the failure, it was on track to win the overall event.These results are remarkable considering none of thedesign team had participated in the Mini-Bajacompetition in previous years. The vehicle performedwell in the hill-climb and maneuverability competitions,but perhaps the most significant indicator of the designquality is the number of complements received. Thegeneral consensus of those who drove the vehicle is thatit is comfortable, easy to control, capable on variousterrain, and attractive (See Figure 4).

The lessons that were learned from this failure should benoted. First, all conceptual design is important, andshould be carried out using conceptual design strategies.These strategies require that a range of concepts beconsidered and compared with criteria identified bymarket research. Second, if design or analysistechniques do not exist, research and testing is requiredto identify failure modes and how to guard against them.Third, design concepts should always be reviewed toprevent poor designs from being implemented.

Reducing product development time is often at odds withimproving the quality of detail design. Achieving bothrequires more time be taken initially to ensure thatcustomer needs are understood by all involved in thedesign. Designers who take the time to understandcustomer needs will be able to screen out poor conceptsmore quickly, and will not waste time developing productattributes that do not add value to the customer. Thedetail design phase requires designers to know whenintuitive judgement can be used. Testing of a full-scaleprototype can provide information on every detail,eliminating the need for individual prototypes for eachdetail. However, each component of a full-productprototype must be evaluated individually to determinehow close to failure it will come during testing, sincetesting a full-product to failure will not reveal componentsthat are near failure. Product development time isreduced when steps are integrated and decisions are

Figure 4: Photo of finished vehicle prototype.

made carefully so that numerous iterations are notrequired. Just as with production processes, makingsure things are done right the first time reduces waste inthe design process.

CONCLUSION

The product realization process for various products anddesign teams differs greatly, as it should. Improvementsto this process must be made on a case by case basis.Some principles apply to all processes, and can be usedto help identify areas in which to make improvements foreach case. One such principle is making sureengineering designers understand the needs and wantsof all product customers and stakeholders. This oftenrequires engineers to become involved with marketingand manufacturing activities. Tools, such as conceptselection matrices and customer-focused specifications,help engineers incorporate the needs of their customersin their designs. And while subjective decisions willnever be eliminated from design work, a betterunderstanding of customer needs will always improve thequality of such judgements, producing designs withgreater market success.

ACKNOWLEDGMENTS

Thanks to the 1999 Brigham Young University SeniorMini-Baja Team and Coaches: Robert Todd, ChrisJones, Andrew Woodings, McKay Asay, Geoff Carlson,David Comstock, Rogelio Flores, Brett Hassell, RyanHubbard, Scott Johnson, Barry Lewis, Benjamin Pack,Kevin Paulson, Josh Thurber, and Brent Zollinger.

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