Team Xtreme 2017 Baja SAE Competition

MECT 4276 – Spring 2017

Senior Design II– Report V

March 30, 2017

Keith Hernandez

Team Lead

Enrique DeLeon

Mechanical Lead

Manjula Hodekar

Logistics Lead

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Abstract

Team Xtreme will research, design, analyze and build a vehicle that meets the rules and

regulations of the 2017 Baja SAE competition and participate in the competition that will take

place in Pittsburg, Kansas on May 25-28, 2017. Using the existing frame from the Baja Brigade

build, Team Xtreme plans to have the vehicle in rolling chassis form by the end of December

2016. The team plans to achieve a top speed of 30 miles per hour on a flat surface and implement

instrumentation capable of real time data acquisition. Currently the team is working on the

design of the suspension and the analysis of the frame is the next task at hand. The front

suspension will consist of an unequal double A-arm set up in the front and a trailing arm set up

in the rear. The project has an estimated cost of $11,600 which includes a 20% contingency and

fundraising is an ongoing process. The team has implemented several tools to help stay on track

and mitigate potential risks that may arise throughout the life of the project. A Gantt chart has

been developed to keep scheduling of tasks on track. The team’s progress is monitored

throughout the project via the timeline and work breakdown structure that has been created.

Weekly meetings and timesheets will also help the team schedule tasks and mitigate any

unforeseen risks.

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Executive Summary

During the duration of the Senior Design I term, Team Xtreme was able to accomplish several

tasks and goals that will aid in completing the project and the challenges proposed by Professor

Pascali. The main challenge of the project consists of taking the original design and frame that

the Baja Brigade senior design team fabricated. We will complete the vehicle with the parts that

the Baja Brigade team procured and raise funds throughout the senior design term.

The team was able to agree on deliverables for the duration of the project and conduct a

significant amount of research that will help in achieving the proposed deliverables. Team

Xtreme also agreed to split the process of designing and fabricating a vehicle into two stages.

The first stage was geared at meeting the deliverable of having a functioning suspension on the

vehicle by the end of December 2016. The team was able to establish communication and a

working relationship with Sean VanVactor, a key member of the Baja Brigade senior design

team. With his help, the team was able to get a better understanding of the vision they had for the

design and fabrication of the vehicle. Sean also agreed to be the team’s graduate advisor and

continues to assist with knowledge, resources, and support. In the second stage of the project the

team will focus on designing and fabricating the rest of the major components needed to

complete the vehicle such as: braking, steering, mounting of the engine, drivetrain and meeting

all safety requirements.

The research phase was a key part of the project that helped familiarize the entire team with the

knowledge needed to design and fabricate a Baja SAE compliant vehicle. Due to the unique

nature of the challenge the team faced, it was agreed to leave the research phase for all major

components of the vehicle open for the duration of the project. The team has a project

management plan in place to ensure timely completion of the goals. With the incorporation of a

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Gantt chart, project timeline, Work Breakdown Structure (WBS) and a Risk Matrix, the team

hopes to ensure a timely completion of the project as well as the ability to mitigate any risks that

may arise throughout the duration of the project. These tools will continually evolve from the

projects conception all the way to the end and serve as critical tools for the team’s success.

The team was able to finish fabrication on the frame by finishing the welding on all of the

members during the first semester. A selected design analysis was also done on the frame to

ensure the safety of the driver. The team agreed to conduct a design analysis for two different

crash scenarios. First, a roll over crash at a free fall height of 7 feet considering one of the

deliverables is to achieve a 7-foot jump. The second crash analysis simulates a head on collision

at 30 mph considering one of the deliverables is to achieve a top speed of 30 mph.

Team Xtreme has also been able to register for the 2017 SAE Baja competition in Pittsburg

Kansas. The funds that will aid the team in the fabrication of the frame for the first semester goal

have been raised. A website has been created to represent the progress of the team and also

serves as a resource to potential sponsors. All along the way the team has been able to document

our trials and tribulations via pictures and video to produce a short video summary of the

incredible ride to this point.

Some lessons learned from the first semester are time management and forward planning. These

two aspects of the project go hand in hand; the lack of forward planning has had a negative

impact on the project. The team failed to plan the presentation dates accordingly and as a

consequence left very little time to prepare and produce material for the second and third

presentations. The first presentation was on 11/8/2016 which was very late into the semester. The

second presentation was 11/29/2016 only three weeks after the first and the final presentation is

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on 12/10/2016 only 10 days after the second. In conclusion Team Xtreme will take these lessons

learned and correct them in the second term.

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Table of Contents

Introduction 8

Team Objective 8

Deliverables 8

History 9

Event Categories 10

Dynamic Events 10

Static Event 11

Winning Strategy 14

Major Components 14

Chassis 15

Suspension 23

Engine 33

Drivetrain 33

Steering 34

Project Management 38

Budget 39

Timeline and Gantt Chart 40

Work Breakdown Structure 41

Risk Matrix 42

References 44

Appendix 46

Timeline 47

Gantt Chart 49

Inventory 50

Weld Testing 51

Frame Dimensions 54

SAE/IMechE Memberships 55

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Engine Schematics 56

Competition Registration 62

Sponsorship Brochure 63

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Introduction

The Baja SAE Competition is one of the design series offered by the Society of Automotive

Engineers (SAE) that University students from around the world can compete in. University

students are required to design and fabricate a high performance off road vehicle. The

competition is a real world scenario that lets students demonstrate their knowledge in the design

and fabrication of a dynamic mechanism. The Baja SAE Competition has a long list of rules and

regulations to ensure the safety of all participants however students are allowed to use creative

and critical thinking to design their vehicle in an innovative fashion. The main focus of the Baja

SAE challenge is to promote teamwork and project management skills between team members.

These qualities become a key to producing a successful project.

Team Objective

The objective is to design and build a vehicle that meets the rules and regulations of the 2017

Baja SAE competition. Team Xtreme will represent the University of Houston and participate in

the competition that will take place in Pittsburg, Kansas on May 25-28, 2017.

Deliverables

Register for the 2017 Baja competition in Pittsburg, Kansas by the November 14, 2016

deadline

Have a Baja vehicle that is mechanically complete with a functioning suspension assembled

by December 2016

Manufacture carbon fiber uprights for the suspension

Achieve a vehicle weight under 400 lbs.

Pass the Baja SAE inspection for the competition

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Achieve a top speed of 30 mph on a flat surface

Design a vehicle that can achieve a flat jump of 7 ft.

Implement instrumentation that is capable of data acquisition

The deliverables were approved by our instructor Raresh Pascali and are intended to be met by

May 2017. One important note is that in order to meet the second deliverable and have a vehicle

that is mechanically complete with a functioning suspension assembled by December 2016,

Team Xtreme will be using some of the components that were designed and fabricated by the

Baja Brigade senior design team.

History

The first Baja SAE Competition was held in 1976 at the University of South Carolina in Jackson,

SC. Ten teams registered for this event with ninety students participating. The competition was

eventually divided into 3 regions: East, Midwest, and West. In 1978, the first Midwest and West

regions competition was held in Milwaukee, WI, Arizona state university, and Phoenix, AZ

respectively. The number of teams that participated continued to grow every year after the first

event. By 2016, 100 teams registered with more than 1000 students participating in all three

regions. Over the years, the Baja SAE Competition has spread to other countries outside of

North America. Brazil’s first Baja SAE event was held in 1995 with 10 registered teams and 90

participating students. Korea’s first event was hosted by Yeungnam University in 1996 with 10

teams and 280 students. South Africa’s first event also started in 1996, hosted by the University

of Pretoria with 4 teams and 12 students.

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Event Categories

The dynamic event and static event are the two main categories in the Baja SAE competition.

The dynamic and static events are divided into separate sections. Some of the dynamic

subcategories vary from event to event based upon the place the competition is held. These

events with sub categories and possible points for each event are listed in Table 1.1 and Table

1.2 below:

Dynamic Events

Acceleration: Tests the vehicle’s ability to pick up speed quickly from a starting point.

Each vehicle may take two attempts in this event and they are tested on a flat surface for

100 ft. or 150 ft. The following equation is used to calculate the acceleration score:

Where:

tshortest = fastest time by any vehicle

tyours = time for the vehicle to be scored

longest = the lesser of: a) slowest time by any vehicle; b) 1.5tshortest

Land maneuverability: Vehicle should be able to go on bumps, sand, rocks, logs etc.

Hill climb/Rock climb: Vehicle should reach the destination point without stopping.

Traction event: Tests the vehicle’s ability to climb an incline surface or pull an object on

a flat surface

Table 1.1

Table 1.2

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Endurance: Ability to operate continuously in any weather conditions for a total of 4

hours.

Static Events

Design event: The objective of the design event is to evaluate the engineering effort put

into the design of the team’s vehicle. The vehicle’s design is expected to be safe and

ergonomic. This event is judged based on design specifications, analysis, testing

development, manufacturability and also serviceability. System integration is taken into

consideration. Design reports should contain a brief description of the team’s vehicle,

design objectives, concept details, and details of key design structures. Design and

specification reports need to be submitted on or before the due date listed in Baja SAE

website (www.bajasae.net) prior to the competition. Late submissions are accepted with

a 10-point penalty per day up to 5 days. After 5 days the team’s registration will be

cancelled.

Cost event: Teams must provide supporting documents to verify the cost calculations for

the proposed model and the actual cost of the particular prototype model. Cost reports

must be submitted including copies of price tags, receipts, invoices, catalog pages, online

prices for every item that costs more than $30.

Sales presentation: The objective of the presentation is to convince a hypothetical

company to purchase the team’s Baja SAE vehicle design and put it into production to

manufacture 4000 vehicles per year. One or more members can present the sales

presentation and it is limited to 10 minutes. Five minutes max for the presentation, and 5

minutes for questions and answers. Teams may get bonus points for this event if the

team’s scores are tied. Judges for this event may include a combination of corporate

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executives who may have experience in marketing, production and finance as well as

engineering.

Design event:

The design event consists of two parts: Design evaluation and the design report. The

design report needs to be submitted before the competition. It includes a brief description of the

vehicle, vehicle concepts, the team’s design objectives, and the details about important features.

The team should be able to provide backup data, analysis, and testing techniques as well as

documents on request at the competition. A design specification sheet needs to be prepared using

the standard template that can be found at www.bajasae.net/go/downloads and submitted

electronically in .xlsx file format.

Design judges will review the report and inspect the vehicle on site for evaluation.

Design reports consist of eight (8) pages of A4 size paper with up to four pages of text and three

pages of vehicle drawings showing the vehicle’s front view, top view, and side view. Photos can

be included in the optional page. One optional page is allowed for photos, charts, graphs, etc.

Design reports must be submitted electronically in pdf format as a single file. Note: late

submissions will result in a ten-point penalty per day up to five days.

The design event is judged based on the design report, and the inspection of the vehicle

on site. Teams are allowed to bring supporting material such as photographs, drawings, plans,

charts, and sample components or materials. One or more team members can present the design

presentation. The design presentation is limited to a total of ten minutes, including one minute

for the clarification questions from the judges, and any team member can answer the questions.

Teams are allowed to bring a laptop, binders or posters to show documentation of the

engineering work they have completed.

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Cost event:

The cost event consists of two related sections, 1. Cost report and 2. Prototype cost. The

cost report includes the background information and calculations to verify the vehicle’s actual

cost. The prototype cost consists of the actual cost of the prototype. The cost report must contain

a one-page summery sheet and cost documentation including copies of price tags, receipts,

invoices, catalog pages, and online prices for every item that costs more than $30. Teams also

need to bring a hard copy of the cost report to the competition site. The prototype cost score will

be calculated using the following formula:

𝑃𝑟𝑜𝑡𝑜𝑡𝑦𝑝𝑒 𝐶𝑜𝑠𝑡 = 85 𝑝𝑜𝑖𝑛𝑡𝑠 x C max −Cyours

C max −𝐶𝑙𝑜𝑤

Where:

Cyours =Vehicle cost, as corrected

Clow = Lowest vehicle cost, corrected

Cmax = Highest Vehicle cost, as corrected

Previous Winners

2016 2015 2014

University Univ. of Michigan Cornell University Cornell University

Team Michigan Baja Racing Big Red Racing Big Red Racing

Dynamic 696.40/700 683.35/700 672.87/700

Static 311.03/300 293.70/300 257.16/300

Overall score 1007.43/1000 977.05/1000 930.03/1000

Table 1.3

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Winning strategy

Improvement: Most of the top ten teams are using the same vehicles for many

competitions. These teams are making continuous improvements on the vehicle from the

previous competition. They are focusing on the events that they scored low points in the

previous competition.

Funding: Many of the top 10 teams received a majority of the funds from their respective

university.

Vehicle Weight: Winning teams achieved a vehicle weight of less than 400 lbs. Some of

the top ten teams used ultra-high molecular weight polyethylene materials for the body,

light weight hammock materials for the seats, and light weight composite materials for

the floor. By using these materials, they were able to keep their vehicle weight under

400lbs.

Achieving maximum points in static event: They also used some electronic devices such

as LCD monitors, driver communication system, and speed sensors. Using these devises

effectively they were able to scored bonus points in the static events.

Major Design Components

The major components of the Baja SAE vehicle are the chassis, suspension, engine,

transmission, brakes, and steering. Each component was researched individually to calculate

https://www.facebook.com/CornellBajaRacing/photos

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costs, availability and standards used throughout other vehicles participating in the Baja SAE

competition.

Chassis

The chassis is a series of tubes connected together to form a coherent structure. The chassis

provides a rigid connection between the rear and front suspension and creates and overall

structural support for other necessary systems of the vehicle. The design of the chassis is

important to support the other components in their respective positions. It also serves as the base

of the entire vehicle. It is extremely important because it provides the necessary protection for

the driver if the vehicle is to receive a substantial amount off impact due to a crash or roll over.

There are also certain restrictions that the Baja SAE

competition regulates such as the dimensions of the

overall frame. The maximum length allowed is 108

inches while the maximum width allowed is 64 inches.

The dimensions are shown in Figure 1.1 to the left. The Baja SAE rules also state that the vehicle

must at least be able to fit a driver that is 75 inches tall and weighs 250 pounds.

There are two standard design structures that could potentially be used in the Baja SAE which

are the spaceframe design and a combination of a monocoque and spaceframe design. The design

of an entirely monocoque chassis would not be a design that is permitted to enter the competition

due to the rule that restricts the use of steel for all of the required frame members. The only

design that would be allowed would be a hybrid version of the spaceframe design in combination

with a monocoque design that would have the body panels double as stress members. Although a

hybrid version of that design would be innovative and advantageous, the spaceframe design is

Figure 1.1

Figure 1.1

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widely used for the vehicles that participate in the Baja SAE competition because of the ease of

fabrication of the structure and the ability to easily make modifications if needed.

In order to meet the deliverable of having a complete rolling chassis by the end of December

2016, under the approval of the instructor, the frame that was designed and fabricated by the

Baja Brigade senior design team will be completed by Team Xtreme. The team will complete the

welding on the frame and build on the design that was originally considered by the Baja Brigade

team. The team will reconsider the material and design in the second semester and make

modifications if necessary, in order to meet the weight requirement listed in the deliverables. The

frame is built with A513-5 DOM steel. The

frame was only tack welded by the previous

team. Team Xtreme completed the welding

on all member of the frame using an arc

welding machine with E6013 welding

electrodes. The welds were grinded down to

achieve a good finish and the frame was sanded down to remove the rust and painted with a

black color finish (Figure 1.2).

Weld Testing

Two samples must be submitted and have to be approved in order to compete in the 2017 Baja

competition. The sample submitted must be fabricated with the same roll cage material used and

with the same welding process and tools. The inspection requirements and the images of the

passing welding and failing welds are listed in the Appendix, Figures A4-A6.

Figure 1.2

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Sample 1 – Destructive Testing

Figure 1.3 shows the sample that has to be fabricated and that will

need to be subjected to destructive testing that will cause the joint

to fail. The test should indicate the superior strength of the weld

with respect to the base material. The team can use pull testing in

a lab, or apply a moment to one side of the joint to test the weld.

Sample 2 – Destructive Inspection

Figure 1.4 shows the sample that has to be submitted during

the competition, so that it can be inspected by the national

technical inspectors. The figures in the Appendix show what

the inspectors will be looking for in the welds and the welded

members.

Chassis Material Selection

Some of the possible materials that the team researched if the frame was to be re-designed or

modified are listed below in Table 1.4. The materials will be looked at more in depth during the

second semester to finalize the decision on whether any modifications are needed to fit the frame

or whether a different material will be used on a new frame design.

Table 1.4

Figure 1.3

Figure 1.4

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Chassis Design Analysis

For safety reasons a finite element analysis (FEA) was performed on the frame the team plans to

use to construct the vehicle. Two different scenarios were analyzed using the ANSYS FEA

software package. The first scenario was constructed to mimic a roll over crash during our 7 ft.

jump we plan to achieve in our proposed deliverables. The dynamic calculations for this crash

are shown below:

A line model of the frame was created and the tube cross section of a 1.25” outside diameter and

a 1.01” inside diameter for the primary members and a 1.25” outside diameter and a 1.06” inside

diameter for the secondary members was assigned to the members of the frame. Next the frame

was fixed at four separate nodes at the bottom of the roll cage and the force that was calculated

for the roll over crash was applied to a single member at the top of the roll cage as shown in the

picture bellow:

Figure 1.5

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The analysis was run several times and each time the element size was reduced by a factor of ½

in order to create more elements on the frame. A result of the mesh sensitivity analysis is shown

below:

Graph 1.1

Figure 1.6

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The mesh sensitivity analysis shows the convergence on a max combined stress of approximately

33,145 psi. The total deformation is 0.171 inches. The contour plot of the max combined stress

and the results are shown below:

The second scenario mimics a head on collision at 30 miles per hour which is the top speed we

plan to achieve in our proposed deliverables. The calculations are shown below:

Figure 1.7

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The same line model with the same assigned cross sections was used for this analysis as well.

The frame was fixed at four separate nodes at the bottom of the roll cage and the force that was

calculated for the head on collision was applied to the front members of the roll cage as shown in

the picture bellow:

Figure 1.8

Figure 1.9

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The analysis was run several times and each time the element size was reduced by a factor of ½

in order to create more elements on the frame. A result of the mesh sensitivity analysis is shown

below:

The mesh sensitivity analysis shows the convergence on a max combined stress of approximately

34,704 psi. The worst case scenario that deals out the most stress and deformation is the head on

collision at 30 mph. The stress from this collision is a little more than half of the yield strength of

A513-5 DOM steel (60,200 psi). This scenario is highly unlikely but still leaves us room to

survive the crash with minimal damage to the frame. A total deformation of 0.383 inches is a

result of this crash. The contour plot of the max combined stress and the results from the head on

collision are shown below:

28568

32199

3349434140 34462

34623 34704

25000

27000

29000

31000

33000

35000

37000

0 10000 20000 30000 40000 50000 60000 70000 80000

Max

Co

mb

ined

Str

ess

(psi

)

Number of Elements

Mesh Sensitivity Analysis (Head On)

Graph 1.2

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Suspension

One of the major challenges of building an SAE vehicle for the competition is to design and

fabricate a suspension that is capable of handling the different terrains that will be present during

the competition. When designing the suspension of any vehicle there are three major angles to

consider that will affect the handling, steering and stability. The camber is the angle of the wheel

Figure 1.10

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relative to the road. In the figure below the angle of the wheel is taken by looking at the car from

the front view (Figure 2.1). Caster is the angular displacement of the steering axis from the

vertical axis of the wheel (Figure 2.2). The toe angle is the symmetric angle that a wheel makes

with the longitudinal axis of the vehicle (Figure 2.3).

Although there are different types of suspension linkages that could be designed and used

for a Baja vehicle, the most common suspension linkage used for the front suspension is a

double wishbone also known as double A-arm. The double wishbone suspension consists

of two A-arms, of either equal length, known as equal length A-arm setup or different

lengths, one shorter than the other, known as unequal A-arm setup as shown in the

Figure 2.1 Figure 2.2

Figure 2.3

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figures below:

In a double wishbone suspension each arm has three pivot points which connect the

suspension to the frame and the steering. One point is connected to the steering knuckle

and the other two points are connected to the frame.

Another common suspension design used for the Baja vehicle that is typically used for

the rear suspension is a trailing arm suspension. The main factors that are considered for

the rear suspension is weight, cost and functionality. The concept of the trailing arm

suspension is simple and its main characteristic is that it connects the frame to the

knuckle with a single arm.

A multilink suspension is another type of suspension linkage that can be used but it’s

more complex than a double wishbone suspension or a trailing arm suspension. It has

better functionality as the suspension is made of two or more links that change the shape

Figure 2.6

Figure 2.4 Figure 2.5

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of the arm as the wheel is turned instead of using two solid upper and lower A-arms. The

figure below shows the concept of a multilink suspension linkage:

Suspension Material Selection

The process for the material selection for the suspension was initiated by comparing the three

most common materials that would be the best fit for the original design idea by the Baja

Brigade senior design team as well as incorporating the design ideas of Team Xtreme. The major

characteristics that were analyzed were cost, weight, strength, and workability. Those

characteristics were ranked beginning with the most important with a multiplier of 4x down to

the least important with a multiplier of 1x. Each was given a score of 1-5, 1 being the least

favorable and 5 being the most favorable. Overall, 1020 DOM steel was chosen as the best fit

material due to the resources available and the time frame the team has to complete the

suspension arms. 1020 DOM steel has high strength and stiffness in addition to its ease of

welding and machining. Although carbon fiber has great mechanical properties and would have

been excellent in reducing weight, the cost was too high compared to the resources the team has

available at the moment. Chromoly was also another great option as far as weight and strength of

the material, but it also fell behind in cost. Table 2.1 below shows the selection material matrix

for the suspension’s upper and lower arms.

Figure 2.7

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Preliminary Suspension Design

Figure 2.8 shows the preliminary design of the front upper and lower A-arms and Figure 2.9

shows the preliminary design for the rear trailing arms. The suspension design is still ongoing

and more analysis must be completed before the fabrication phase can begin. The only decisions

that have been made are on the material that will be used to fabricate the front and rear linkage,

1020 DOM Steel, and the type of linkage that will be used.

Table 2.1

Figure 2.8

Figure 2.9

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Front Suspension Design and Fabrication

Using the software provided by Optimum Kinematics, the suspension geometry was designed

and several calculations were made by inputting some of the parameters that were established. In

order to successfully design the geometry, the tire and wheel data were inputted into the software

such as the tire diameter, the tire width, and rim diameter (26x10-12). The ride height of the

vehicle was established to be 9 inches from the floor to the edge of the bottom frame tube. The

hard points of where the control arms would be attached to the frame were also inputted in xyz

coordinate form. The camber was set to 3 degrees and the track width to 50 inches for the front

and 47 inches for the rear. Figure 2.10 shows the front and rear suspension in Optimum

Kinematics. From the data inputted the following results were gathered:

From the data inputted the following results were generated: a kingpin inclination of 15.4

degrees was a result of this set up. The upper a-arms will be a length of 14.75 inches and the

lower a-arm is a length of 15.5 inches. The kingpin, when viewed from the front, is the

Figure 2.10

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inclination of the steering axis with respect to the center of the tire. The scrub radius is the

distance between the kingpin angle and the center line of the tire where they intersect the ground.

When designing a suspension, you want to minimize the scrub radius to ensure the greatest

contact patch between the tire and the road thus ensuring optimal steering and handling

characteristics for the vehicle. The scrub radius for the suspension design was a distance of 1.1

inches. The roll center is another key factor that must be taken into consideration to ensure good

handling characteristics. The distance between the roll center and the vehicles center of gravity

should be minimized. This distance acts as a lever arm for the vehicles mass the longer it is the

greater the body roll when cornering. Our roll center comes in at 3.95 inches from the ground.

You can see in figure 2.11 the outputs of the suspension that were calculated in Optimum

Kinematics.

Figure 2.11

After getting some preliminary data points and suspension outputs from the Optimum

Kinematics software fabrication of the front suspension was started. Double a-arms of unequal

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length were fabricated and the fox racing air shocks were used as a damper. The a-arms also

have adjustable ball joints that can be used to adjust the camber of the vehicles front wheels. In

figure 2.12 you can see the progression from design to manufacture of the a-arms for one side of

the front suspension. Figure 2.13 shows the suspension progress to date with half of the front

suspension complete

Figure 2.12

Figure 2.13

Rear Suspension Design and Fabrication

The original design for the front suspension consisted of a double wishbone set up. However, the

double wishbone suspension requires more bushings, rod ends, and steel tubing. So, the team

decided to redesign the setup and fabricate two trailing arms instead due to a lack of funding.

Our design eliminated the need for rod ends to connect to the knuckle because we welded the

knuckle straight to the trailing arm and created one solid piece. The Fox Float Three racing

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shocks will provide damping for the system and the Mud Wolf tires will be used in the rear. The

team manufactured a solid steel pivot bar for the trailing arm. A progression of the assembly is

depicted below in Figure 2.14.

One more link from the knuckle to the frame needs to be added to the rear suspension for

support.

Dampers

The dampers that the team will be using for the

suspension are the Fox Racing Shocks Float 3. They

are high performance shock absorbers that use air as

springs, unlike heavy steel coil springs. The dampers

Figure 2.10 Figure 2.15

Figure 2.14

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contain high pressure nitrogen gas that ensures consistent fade-free damping in most riding

terrains. The shocks are built using 6061 – T6 aluminum which is a lightweight and strong

material that provides a great advantage. Each shock weighs approximately 2-2.5 lbs. which is

beneficial to keeping the components lightweight and the overall weight of the vehicle under 400

lbs. Another great advantage of using Fox Air Shocks is that they have the ability to be adjusted

by changing the pressure in the air chamber to make the shock stiffer or softer depending on the

terrain, giving it a huge advantage over a coil-over shock. By adjusting the air pressure in the

shock the rider can fine tune the shock’s spring curve which can allow for use in different riding

terrains. The air shocks provide a progressive suspension which provides a “bottomless” feel by

eliminating any hard bottoming of the suspension. According to the graph data gathered from

Fox Racing, (Graph 2.1) it shows a comparison of the spring forces at three different initial air

pressure settings of the air shock compared to a coil spring. As it can be seen in the graph, the

coil spring forms a linear line while the air shocks have a progressive build. One disadvantage of

using air shocks is that they are temperature dependent. The shocks have about a 10 psi air

pressure change over a 100-degree temperature change. One important note to consider is that

the endurance event during the competition is a constant run of 4 hours. The performance of the

shock might be affected due to the temperature increase which is a variable that the team will

account for and continue to research in order to be fully prepared.

Graph 2.1

Graph 2.1

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Engine

Every vehicle participating in the 2017 Baja SAE competition is required to use the Briggs and

Stratton Model 19 engine during the event (Model# 19L232-0054-G1). Any modifications to the

engine are strictly prohibited and will result in disqualification of the team. The Model 19 is a 10

HP, four cycle, air cooled engine that is donated by the Briggs and Stratton Corporation to all

participants that register for the competition. The teams are in charge of paying the $250 fee for

shipping and handling of the required engine.

Drivetrain

The drivetrain is a very crucial component of the vehicle. It is the component that delivers the

power from the engine to the wheels. One major factor to consider is that every team in the

competition will be using the same engine without any modifications, so in order to achieve

more efficiency in the power that is delivered to the wheels; the team must closely look at the

design of the drivetrain. Another aspect that is important to the team is meeting the deliverable

which states that the Baja vehicle will be able to achieve a top speed of at least 30 mph on a flat

surface. In order to successfully design a vehicle that not only meets that deliverable but can also

deliver enough power to handle the rough terrains of the competition certain design constraints

must be considered such as the engine limitations that have been specified. The need for a

lightweight and compact transmission that is susceptible to the space allotted in the frame and

that has the ability to adjust from high to low gears depending on the terrain encountered during

the competition. The two possible options for the drivetrain that the team is currently considering

are either a manual transmission or an automatic transmission and the advantages and

disadvantages that each one has.

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Automatic transmissions such as a Continuously Variable Transmission (CVT) are the

most commonly used in the vehicles that participate in the competition. CVT’s are very

effective in the competition due to their ability to automatically adjust to the traction

requirements. A CVT has a greater shifting range than manual transmissions and it is best

suited for acceleration. The challenge with CVT transmissions is that tuning is a very

crucial aspect and in order to tune it expertise and knowledge are required.

In manual transmissions, torque and speed are restricted on gear shifting but they are less

complex than CVT’s and tend to be less costly as well. Manual transmissions also require

less maintenance and give the driver more control on the performance of the vehicle.

Another benefit is that manual transmissions tend to also weigh less than their

counterpart automatic transmissions.

Steering Design

The steering connects to the vehicle’s suspension and allows the driver to gain control of the

vehicle maneuver and guide it through the desired course. The steering system essentially

connects the front wheels, to the steering wheel that is located in front of the driver via the

steering column. Factors such as the turn radius and steering stability are affected depending on

the design of the steering system therefore it is essential that it is design effectively.

The rack and pinion design is the most common design used for steering in the Baja SAE

vehicles. The design is simple and consists of the steering wheel, attached to the steering

column, the rack and pinion, tie rod and kingpin. The figures below show the setup of the

rack and pinion.

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The advantage of the rack and pinion system is that it has relatively fewer parts than other

steering systems therefore it is lighter and easier to repair. Having fewer components also

allows for more responsive turning and control over the vehicle. One disadvantage is that

the system transfers more vibrations to the driver and although it provides great handling

on smooth terrain, it needs a greater force to turn the wheels on uneven or rough terrain

which causes the system to wear out faster.

Recirculating-ball steering is another type of steering design which the steering column

turns a large screw which meshes with a nut by recirculating balls. The nut moves a

sector of a gear causing it to rotate about its axis as the screw is turned. The pitman arm

which is connected to the steering linkage is moved by the arm that is attached to the axis

sector. Figure 5.3 below shows the recirculating-ball steering design.

One advantage of this design is the ability to have more or less steering travel than a rack

and pinion system and it is also less expensive. One drawback is that is less efficient than

Figure 5.1

Figure 5.3

Figure 5.2

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a rack and pinion system and it has so many components that it makes it heavier. Due to

friction it is more prone to wear.

Steering Selection

The thin line rack and pinion will be used as the main component for the steering of the vehicle.

The rack and pinion system is part of the current inventory and will be mounted horizontally on

the plate that is mounted to the frame as seen on the image below. The rack and pinion system is

11 inches from the center of the eye to the center of the

opposite eye. It will connect to a 3/8 in x 36 spline shaft

that will be attached to the steering column. The rack

and pinion has a gear ratio of 1.5:1. The gear ratio is the

distance the rack moves, measured in inches, in relation

to one full revolution of the pinion. By measuring the distance from the end of the rack to an

arbitrary point and turning the pinion one full revolution and then measuring the distance again,

that difference is the gear ratio. The total travel for the rack is 4.5 inches to one side. One

advantage of the rack and pinion system is that it’s reliable and has less chance of failure

compared to other steering systems. In order to successfully design the steering system, the team

has to calculate the wheel base, track width, center of gravity of the vehicle, turning radius,

Ackerman’s angle and steering ratio as the parameters. The wheel base is the distance between

the center of the front wheel and the rear wheel. The track width is the distance between the

center of the front right wheel and the left front wheel. The turning radius is the distance between

the center of gravity and the point about which the wheel turns during a turn. The Ackerman

angle is calculated by dividing the track width by the turning radius. By mounting the rack and

pinion horizontally behind the upright and tie rod connection, an Ackerman steering geometry

can be achieved which prevents the wheels from slipping during turns. The team will continue to

Figure 5.4

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research, design and analyze the steering components by the second semester to achieve the best

possible steering geometry.

Steering Fabrication

The rack and pinion steering fabrication was completed and the steering tie rods are too close to

the front air shocks. The team must redesign the steering by cutting off the plate that the rack and

pinion mounts to. Once this plate is removed a new one will be welded in further up towards the

front of the vehicle giving it enough clearance to operate. The team still needs to acquire a

steering column and mount it in the vehicle to complete the assembly. A picture of the assembled

steering system is shown in Figure 5.5.

Figure 5.5

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Wheels & Tires

4 - Mud Wolf Tires (Figure 5.6)

26 x 10.00 – 12 NHS

4 Lug wheels – fit the current wheel hubs that will be

used

Provide great traction, stability and control with

minimum roll

Fit for the different terrains that will be encountered

during the Baja competition in Pittsburg, Kansas

Project Management

In order for Team Xtreme to successfully complete the project on time and meet the other

proposed deadlines and goals certain constraints were laid out as the foundation of the project.

The scope, time and budget are the primary constraints of the project. In the initiation process, all

through the planning, execution, and closing of the project, the potential risks were identified, the

work break down structure was created and the timeline was generated to increase productivity

and to allow the team to successfully manage the project from start to finish.

Figure 5.6

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Budget

After considering the donated parts listed in the Appendix (Figure A3) the highest costs for the

entire project includes the transmission, registration fees and the travel expenses for the 2017

Baja SAE competition in Kansas. The mitigation for these high costs include making fundraising

a weekly focus throughout the semester to raise enough funds for the registration fees and use a

members’ vehicle and borrow a trailer to reduce the cost of travel. The team will also check

online routinely for deals on lodging. The team has also been able to secure donations that will

help with these large expenses as well as provide funding for any materials needed to fabricate

the vehicle.

Table 6.1

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Timeline

Listed in the Appendix (Figure A1) at the end of the report is the timeline for the entire project

which is designed to help the team stay on track. One of the keys to having a successful project

build is time management coupled with strong team work. The timeline has been developed to

keep everyone on track and aware of our current position as well as how much work still needs

to be done. So far we have left the research of the major components open considering we will

tackle most of those tasks in the second semester. Currently we are finishing up the first

fabrication phase. The team has also started the second design phase for the steering and braking

of the vehicle.

Gantt Chart

The project Gantt Chart is featured in the appendix (Figure A2). Note the difference in time

between presentations from Senior Design I to Senior Design II. This was a major lesson learned

in the project and was not repeated in the second term.

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Work Breakdown Structure (WBS)

The Work Breakdown Structure above shows an exploded view of the entire project as well as

the tasks the team has completed, the tasks that are in progress and the tasks that have not been

started. As of presentation 5 the team has finished the suspension fabrication. We are in the

middle of the second design phase as well. At the moment we are slightly behind schedule but

hope to get back on track during the rest of the project.

Figure 6.2

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Risk Matrix

The risk matrix above shows the progression from the beginning of the project up to the fifth

presentation on March 30th. The teams greatest risk is still funding which was reduced slightly

due to a donation that will cover our largest costs which include travel, lodging, and registration

fees. The team was also able to secure another small donation that was used for the suspension

fabrication. The fabrication risk was mitigated when the team secured an experienced welder

who has agreed to help for the duration of the project. The team agreed that time management

should be increased as a reminder that this is a critical part of the projects success and that we

Figure 6.3

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need to do a better job managing our time and planning ahead. We will also weekly goals and

increase the number of hours we work on the project for the rest of the final semester. Two new

risks have been added to the risk matrix since the beginning of the project the first one is the

vehicle weight. The mitigation for this risk is to use light weight components as much as possible

to meet our deliverable of fabricating a vehicle with a curb weight under 400 pounds. The second

risk that was added is the possibility that some of the parts we acquired from Baja Brigade could

be defective. The parts we acquired have been sitting around for over a year and may not be in

working condition any longer. Our mitigation for this risk is to find out these parts can be used as

soon as possible and if they can’t we must reorder them in a timely fashion.

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References

"BAJA Automotive Enthusiasts." Baja Tutor Knowledge Base for BAJA Automotive Enthusiasts.

Web. 15 Oct. 2016. <http://bajatutor.org/>.

"Baja SAE Kansas." - Baja SAE. Web. 1 Sept. 2016. <http://students.sae.org/cds/bajasae/east/>.

CADmantra Technologies Follow. "Chassis Design for Baja SAE." Chassis Design for Baja

SAE. 26 Sept. 2015. Web. 26 Sept. 2016. <http://www.slideshare.net/bholapatel/chassis-

design-for-baja-sae>.

"Intrax Racing." Intrax Racing. Web. 20 Oct. 2016. <http://en.intraxracing.nl/techniek/camber,-

caster,-toe-intoe-out/>.

Isaac-Lowry, By Jacob. "Suspension Design: Types of Suspensions - Automotive Articles .com

Magazine." Suspension Design: Types of Suspensions - Automotive Articles .com

Magazine. Web. 6 Sept. 2016.

<http://www.automotivearticles.com/Suspension_Design_Types_of_Suspensions.shtml>.

Michael, John. "The Advantages of Rack & Pinion Steering." EHow. Demand Media. Web. 01

Nov. 2016. <http://www.ehow.com/list_6102863_advantages-rack-pinion-

steering.html>.

"Rack and Pinion Steering System | Advantages | Application." Mechanical Engineering World.

Web. 1 Nov. 2016. <http://www.mechengg.net/2015/03/rack-and-pinion-steering-

system.html>.

"Recirculating Ball." Wikipedia. Wikimedia Foundation. Web. 07 Nov. 2016.

<https://en.wikipedia.org/wiki/Recirculating_ball>.

"SAE Baja Car." MiniBuggyNet The Ultimate OffRoad Buggy Community RSS. Web. 20 Oct.

2016. <http://www.minibuggy.net/forum/show-off-your-toys-here/6776-sae-baja-car-

7.html>.

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Singh, Avinash. Off-Road Suspension Design. 2016. Amazon Inc.

"Trailing Arm or Semi Trailing Arm." Official Baja SAE Forums. Web. 22 Sept. 2016.

<http://forums.bajasae.net/forum/trailing-arm-or-semi-trailing-arm_topic1834.html>.

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APPENDIX

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Figure A1 – Timeline: Semester 1

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Timeline: Semester 2

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Figure A2 – Gantt Chart

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Figure A3 – Inventory

Item Description Quantity

Fox Racing Shocks Float 3, 7.94 Travel, 24.13 Extended 4

Wheel Bearing Kit Front Honda TRX350FE 00-06 2

Wheel Hub 2-1986 Honda TRX350 4x4, 2 Rear 4

Rack & Pinion Thin Line Rack & Pinion - 5/8 x 36 Spline 1

Tie Rods 2

CV Axles Honda TRX 350 Rancher 2

Lug Nuts DF-54010S, 10mmx1.25RH 16

Offroad Rims and Tires 4

Side Mirrors Black circular 2

Backup Alarm 2012 Series Back-up Alarm 87dB, Model:210238-S Volts: 12/24 VDC 1

Tee Gauge Fitting 1/8" NPT Tee Gauge Fitting - 50138 1

CVT Transmission CVT Magnum 40 1

Steering Column (Does not fit rack and pinion) 1

Racing Seat Black 1

Battery 12V 6AH Battery 1

Brake AssemblyWilwood Dual Master Cylinder Brake Assembly -

Pedal, pistons, & Lines1

Kill Switch 2

Steering Wheel 1

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Figure A4 - Examples of Failing Welds: Sample #1 (Destructive Testing)

http://students.sae.org/cds/bajasae/rules

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Figure A5 - Examples of Failing Welds: Sample #2 (Destructive Inspection)

http://students.sae.org/cds/bajasae/rules

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Figure A6 - Examples of Passing Welds

http://students.sae.org/cds/bajasae/rules

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SAE/IMechE Memberships

In order to participate in the competition, team members must be members of at least one of the

following societies: (1) SAE International or an SAE International affiliate society, (2) ATA, or

(3) IMechE or (4) VDI. Proof of membership, such as a membership card, is required at the

event.

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Engine Schematics

MODEL 19L100 VANGUARD

DIMENSION UNITS ARE IN INCHES [mm] UNITS ARE FOR REFERENCE ONLY

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MODEL 19L100 VANGUARD

DIMENSION UNITS ARE IN INCHES [mm] UNITS ARE FOR REFERENCE ONLY

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MODEL 19L100 VANGUARD

DIMENSION UNITS ARE IN INCHES [mm] UNITS ARE FOR REFERENCE ONLY

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MODEL 19L100 VANGUARD

DIMENSION UNITS ARE IN INCHES [mm] UNITS ARE FOR REFERENCE ONLY

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MODEL 19L100 VANGUARD

DIMENSION UNITS ARE IN INCHES [mm] UNITS ARE FOR REFERENCE ONLY

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MODEL 19L100 VANGUARD

DIMENSION UNITS ARE IN INCHES [mm] UNITS ARE FOR REFERENCE ONLY

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Competition Registration

The team has registered for the competition in Pittsburg Kansas taking place in May 2017. The

team is currently on the wait list but has the obligation to submit the paperwork and documentation

required for the competition. Four weeks before the competition, the team will be notified whether

there is room to advance into the competition phase.

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