UCSB BAJA SAE - CHASSIS

Acknowledgments Nicole Holstrom Eric Matthys Nelson Bednersh Brighter Image Racing Ian’s Tire Company Nate True Andy Weinberg Glenn Beltz Stephen Laguette Makin’ Trax Suspension Fiberglass Hawaii Jasmine Batt

Sam Chapple, Rory Hofstatter, Kamala McNaul, Chris Prax, Colin Webb ME 189 Team 18A, June 6th, 2009

The 2009 Baja SAE® Design Series is a three day event which challenges student teams to design and build an off-road vehicle and pitch the design as a start up company. Our team focused on developing a lightweight, yet robust chassis. The tubular chassis has been optimized to meet performance and safety requirements while remaining lightweight. After conducting literature reviews, physical testing and FEA analysis we produced a final design that met our goals and performed competitively, placing 36th out of 95 teams.

Our final design resulted from a set of experimental and analytical factors. It was refined and finalized with weld strength and material tests and Finite Element Analysis.

Figure 1: Weld Testing and Data

Figure 2: FEA for calibration. [A] Front Impact of 579 lbs [B] Side Impact of 579 lbs

Figure 5: Finishing the Endurance Event

References

Maneuverability-34th Accleration-54th

Hill Climb-20th

ABSTRACT

PROJECT OBJECTIVES

RESULTS

DESIGN ANALYSIS

Adams, Herb. Chassis Engineering/Chassis Design and Building. Los Angeles: HP Books, 1993.

Meet or exceed all Baja SAE safety regulations Design lightweight frame to maximize power output Ensure driver safety with robust roll cage Optimize center of mass to increase stability and prevent vehicle rollover Use sound design methods to prevent structural failure Manufacture using basic tools for under $1200

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0 0.2 0.4 0.6 0.8 1 1.2

Load

(lbs

)

Displacement (in)

Average Weld Procedure Test Results

TIG

MIG

Annealed

Figure 3: Impact Calibration Testing

Design-31st

Sales- 50th

Rock Crawl-41st

Endurance-28th

Strain E (psi) Stress (psi) FEA Stress (psi) % Difference

FRONTAL LOADING Top 4.62E-05 1.41E+07 6.52E+02 6.83E+02 -4.54 Side 4.53E-04 1.41E+07 6.39E+03 6.61E+03 -3.33

Front 3.26E-04 1.41E+07 4.60E+03 4.75E+03 -3.16

SIDE LOADING Top 7.66E-05 1.41E+07 1.08E+03 1.13E+03 -4.42 Side 9.01E-04 1.41E+07 1.27E+04 1.29E+04 -1.55

Front 3.21E-05 1.41E+07 4.52E+02 4.67E+02 -3.21

ROLL OVER LOADING Top 1.55E-04 1.41E+07 2.19E+03 2.23E+03 -2.02 Side 2.94E-04 1.41E+07 4.15E+03 4.24E+03 -2.12

Front 4.67E-05 1.41E+07 6.59E+02 6.88E+02 -4.22

TIG (Tungsten Inert Gas) welding provides the strongest and most consistent joints. All tests verified that the material failed before the weld.

Calculations of the bending stiffness, bending strength, and mass per unit length for standard sizes of multiple materials led to selection of 4130 Chromoly Steel Tubing for frame construction.

Force (KN) / (lbf) Peak FEA Stress (psi) Yield Stress (psi) % Difference

FRONTAL IMPACT 11.1 / 2500 5.04E+04 6.31+04 20.1%

SIDE IMPACT 11.1 / 2500 6.16E+04 6.31+04 2.38%

ROLL OVER IMPACT 11.1 / 2500 6.24E+04 6.31+04 1.11%

BOTTOMING-OUT 15.5 / 3480 2.41E+04 6.31+04 61.8%

SUSPENSION LOAD 15.5 / 3480 6.19E+04 6.31+04 1.90% DESIGN DEVELOPMENT

Using FEA we are able to load the chassis according to likely impact scenarios. This allowed us to isolate and eliminate problem areas in our initial designs.

[A] [B]

Table 1: Calibration Results

PHYSICAL TESTING We calibrated the FEA model by physically loading the chassis and collecting strain readings which were compared to the measured values (Table 1).

After calibrating the model, we were able to test if the frame will experience plastic deformation during an impact, under several loading scenarios.

[A] [B]

A Special Thanks To Our Friends and Family

The peak stress induced in our five impact scenarios compared to the yield stress of our material to show that none of the applied forces compromised the integrity of the chassis (Table 2).

Figure 4:FEA for impact scenarios. [A] Bottom Out Impact of 4000 lbs [B] Suspension Impact of 4000 lbs

Table 2: Impact Testing Results

COMPETITION HIGHLIGHTS

OVERALL – 36th of 95

“This Baja vehicle was the most successful and robust in the history of UCSB.” -Associate Dean Beltz