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The Mini-Baja Project

Patrick Chittchang

Pratik Desai

Rehan Kazmi

Brian Mok

ENME 471, Dr. Panos Charalambides

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Outline

Project Objectives Design Methodology Boundary Conditions Mini-Baja Frames Results Conclusions Questions

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Project Objectives

To develop a frame that conforms to the SAE standards

To develop a frame that is streamlined, low-weight andsafe for the driver and other competitors.

Optimize the Stress-Weight tradeoff.

Cost effectiveness.

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SAE Specifications for the

Mini-BajaThe roll cage must satisfy SAE requirements for space andstrength (minimum size 1-inch ODx0.083 thickness DOM steeltubing).

Side bars with a height of 8-inches (min.) above the lowestpoint of the seat of the pants of the driver.

Maximum time for a driver to exit the vehicle is five seconds.

Transportable via standard pickup trucks with eight foot beds.

Consider the aesthetics of the frame as well as the strengthand size requirements.

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Design Tasks

Perform simulation on all Mini-Baja models.

Analyze and Evaluate the stress distributions.

Drivers safety First

Optimize Stress Vs Weight relationship.

Modify and finalize the model

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Model Development

Pre-Processing

Element: Linear Isotropic 1 D Beam Element withCircular Cross-Section

Material: 1020 DOM Steel (Driven Over Mandrel)

Apply Boundary Conditions Symmetry/ Anti-Symmetry

Processing

Meshing

Solve the model using I-DEAS

Post Processing

Data Analysis

Make informed choices to meet the design objective

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Loading Cases

Six loading conditions:

1. Rollover

2. Front Bump

3. Rear Bump

4. Frontal Collision

5. Heave

6. Twist Ditch

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Frontal Collision Test

Test: Frontal Collision

Model used: Half model

Condition: Symmetry

Loading: a uniformly distributed1680 lb force in X-direction at thefront of the vehicle

Boundary Condition:Rear corner:Trans X=Y=Z=0Opp.Rear corner:Trans X=Y=0Front corner:Trans Y=0Opp.Front corner: Trans Y=Z=0

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Heave Loading

Test: Heave Loading

Model used: Half model

Loading: Engine and Driver load =(100 +210)*3= 630 lbs

Boundary Conditions:

One rear corner: X,Y & Z =0Opposite rear corner: X &Y = 0One Front Corner: Y = 0

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Rollover Test

Test: Rollover

Model Used: Full

Loading: Rollover loadingconsidered is 9.42G acting onone of the top front joints ofthe frame

Vertical load: 4200lbs

Fore & Aft load: 3080lbs

Lateral load: 840lbs

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One Front Wheel Bump Test

Test: Front Bump

Model used: Full model

Loading: a point force of 1680lbs in the Y-directionof the front corner node

Boundary Conditions:Rear corner:Trans X=Y=Z=0

Opp.Rear corner:Trans X=Y=0Opp.Front corner: Trans Y=Z=0Other corner: Simulate the force equal

to 3 X Total Vehicle Weight = 1680lbs

F

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One Rear Wheel Bump TestTest: Rear Bump

Model used: Full model

Loading: 1680 lbs in Y-directionof the rear corner node

Boundary Conditions:

Front corner:Trans X=Y=Z=0

Opposite Front corner:Trans X=Y=0

Rear corner: Trans Y=Z=0 Other corner: Simulate the

force equal to 3 X TotalVehicle Weight = 1680 lbs

F

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Twist Ditch Test

Test: Twist Ditch

Model used: Half model (Anti-Symmetric)

Loading: Engine and Driver load =(100 +210)*3= 630 lbs

Boundary Conditions: One rear corner: X,Y & Z =0

Opposite rear corner: X &Y = 0

One Front Corner: Y = 0

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Designed Frames

Model 1- BubbleThis is the base model given to us by the problem

definition

Model 2-ButtercupAn over-designed version in order to first pass the model

successfully through the six severe loading conditions

Model 3-Blossom

Getting the right mix between stress reduction andweight optimization paradigm

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Model 1 - Bubble

Model 1 (the original frame)

Elements are all 1 x 0.083 inchtubing

Six loading tests

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Nodes and Elements-Bubble

Elements are 1 x 0.083 tubing throughout the frame

Nodes 26

Elements 46

Length (in) 75.74

Width (in) 27.35

Height (in) 44.83

Weight (lbs) 61

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Bubble Results

Failed:

Rollover :34 elements

Front Bump : 16 elements

Rear Bump : 25 elements

Passed:

Frontal Collision

Heave

Twist Ditch

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Rollover TestReal Time Model DisplacementVon-Mises Stress

Green: Pass

Red: Failed

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Model 1 test results andobservations

Roll over and Bump tests were the most severe

Von Mises Stress is used as a critical design parameter

The model needs to be beefed up in the drivers compartment

Decide viable way to increase the stiffness of the overallstructure

Essentially the major goal for the next step was to pass themodel

Minimization of overall weight

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Modeling Tasks for Model 2

Reconfigure the roll cage.

Making sure the frame passes rollover and bump tests.

Add cross members to the top of the drivers compartment and backwindshield in order to triangulate the stresses

Separate the drivers compartment from the engine compartment byadding a beam.

Add members to the side of the drivers carriage (below).

Resist the temptation to add a cross member that would block thedrivers access in and out of the Mini-Baja.

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Model 2- Buttercup

Tubing Chart

Color Tubes

Pink 1 x 0.083

Orange 1 x 0.15

Blue 2 x 0.125

Light Blue 2 x 0.100

Black 3 x 0.1400

Tube Sizes Induces Drastic Weight Changes

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Test results and Observation

Buttercup passed all the tests

Weight: 128 lbs

5 types of different Tubes

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Modeling Tasks for Model 3

Design Reform

Experiment with

curve beam

Difficulties

Solutions

Point Load Distributed Load

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Model 3

Curvature

Curve makes everything Beautiful

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Rollover Test Distributed Load

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Rollover Test Point Load

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Blossom Test Results

Strength: Weight and Aesthetic

The weight : 120lbs

4 different Types of Tube

Passed all the six loading cases

Aerodynamic shape

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ComparisonTubing Sizes Model 1 Model 2 Model 3

dia x wall thickness (inch)

1.0 x 0.083 46 41 44

1.0 x 0.15 0 9 0

2.0 x 0.083 0 0 0

2.0 x 0.1 0 6 02.0 x 0.125 0 2 0

2.0 x 0.145 0 0 1

2.0 x 0.175 0 0 4

2.0 x 0.21 0 0 23.0 x 0.14 0 4 0

Total Members 46 62 51

Weight (pounds) 61 128 120

Cost ($) 504 1250 1050

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Conclusions

Bubble was the lightest but it failed miserablyunder most of the loading conditions

The second model-Buttercup was developed bymodifying the first model making changes in thetube X-section and adding more elements. Itpassed all the loading conditions but was reallyheavy to be used as our final design

Blossom: Great Looks with Excellent Performance

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Questions?

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Credits

We extend our sincere thanks to all thepeople who made this project possible

We also would like to thank UMBC forproviding us with the facilities required tocomplete the project

AND FINALLY:

Our special thanks to Dr. Panos Charalambidesfor providing the opportunity to gain an insightinto the finite elements intricacies

We wish all the best to our classmates who aregraduating this semester .

-GOOD LUCK GUYS