The Mini-Baja Project

Patrick Chittchang

Pratik Desai

Rehan Kazmi

Brian Mok

ENME 471, Dr. Panos Charalambides

Outline

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

Project Objectives

• To develop a frame that conforms to the SAE standards

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

•Optimize the Stress-Weight tradeoff.

• Cost effectiveness.

SAE Specifications for the Mini-Baja

•The roll cage must satisfy SAE requirements for space and strength (minimum size 1-inch ODx0.083 thickness DOM steel tubing).

•Side bars with a height of 8-inches (min.) above the lowest point 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 strength and size requirements.

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

Model Development

Pre-Processing Element: Linear Isotropic 1 D Beam Element with

Circular 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

Loading Cases

Six loading conditions:

1. Rollover

2. Front Bump

3. Rear Bump

4. Frontal Collision

5. Heave

6. Twist Ditch

Frontal Collision Test

Test: Frontal Collision

Model used: Half model

Condition: Symmetry

Loading: a uniformly distributed 1680 lb force in X-direction at the front 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

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

Rollover Test

Test: Rollover

Model Used: Full

Loading: Rollover loading considered is 9.42G acting on one of the top front joints of the frame

Vertical load: 4200lbs

Fore & Aft load: 3080lbs

Lateral load: 840lbs

One Front Wheel Bump Test

Test: Front Bump

Model used: Full model

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

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

equal to 3 X Total Vehicle Weight = 1680 lbs

F

One Rear Wheel Bump TestTest: Rear Bump

Model used: Full model

Loading: 1680 lbs in Y-direction of 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 Total Vehicle Weight = 1680 lbs

F

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

Designed Frames

Model 1- Bubble This 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-BlossomGetting the right mix between stress reduction and

weight optimization paradigm

Model 1 - Bubble

• Model 1 (the original frame)

• Elements are all 1 x 0.083 inch tubing

• Six loading tests

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

Bubble Results

Failed:

•Rollover :34 elements

•Front Bump : 16 elements

•Rear Bump : 25 elements

Passed:

•Frontal Collision

•Heave

•Twist Ditch

Rollover TestReal Time Model DisplacementVon-Mises Stress

Green: Pass

Red: Failed

Model 1 test results and observations

• 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 overall structure

• Essentially the major goal for the next step was to pass the model

• Minimization of overall weight

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 back windshield in order to triangulate the stresses

•Separate the drivers compartment from the engine compartment by adding a beam.

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

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

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

Test results and Observation

• Buttercup passed all the tests

• Weight: 128 lbs

• 5 types of different Tubes

Modeling Tasks for Model 3

• Design Reform• Experiment with

curve beam • Difficulties• Solutions

– Point Load– Distributed Load

CS1_{Global}

Model 3

Curvature

Curve makes everything Beautiful

Rollover Test – Distributed Load

Rollover Test – Point Load

Blossom Test Results

• Strength: Weight and Aesthetic

• The weight : 120lbs

• 4 different Types of Tube

• Passed all the six loading cases

• Aerodynamic shape

Comparison Tubing 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 0

2.0 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 2

3.0 x 0.14 0 4 0

Total Members 46 62 51

Weight (pounds) 61 128 120

Cost ($) 504 1250 1050

Conclusions

• Bubble was the lightest but it failed miserably under most of the loading conditions

• The second model-Buttercup was developed by modifying the first model making changes in the tube X-section and adding more elements. It passed all the loading conditions but was really heavy to be used as our final design

• Blossom: Great Looks with Excellent Performance

Questions?

CreditsWe extend our sincere thanks to all the people who made this project possible

We also would like to thank UMBC for providing us with the facilities required to complete the project

AND FINALLY:

Our special thanks to Dr. Panos Charalambides for providing the opportunity to gain an insight into the finite elements intricacies

We wish all the best to our classmates who are graduating this semester . -GOOD LUCK GUYS