Effects of Outriggers on Dynamic Rollover Resistance Maneuvers

Devin Elsasser Transportation Research Center Inc.

Garrick ForkenbrockNational Highway Traffic Safety Administration

Results From NHTSA’s Light Vehicle Rollover Research Program

3/05/03

Presentation Overview

Introductionl Dynamic testingl Objectives

Test Matrixl Vehiclesl Maneuversl Outriggers

Testing Locations and Conditionsl Locationl Ambient Conditions

Test Equipmentl Vehicle configuration,

Instrumentation and tiresl Comparison of three

outrigger typesTest Resultsl Results from VIMF datal Results from dynamic testing

Discussion of Resultsl Observations from dynamic

testingConclusions

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Introduction

Dynamic Testingl Essential part of the rollover-rating programl Mandated by TREAD Actl Severe nature of tests require outriggers for driver safety

Objective of Outrigger Studyl Preserve driver safetyl Evaluate outriggers with different weights and inertiasl Determine the extent to which different outrigger designs

influence test results of J-Turn and Road Edge Recovery test maneuvers

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Outrigger Criteria

Design criterial Minimize weight of outriggers

– Reduces center of gravity influencel Minimize roll inertial Lower pitch and yaw inertiasl Outrigger height adjustabilityl Straight forward installation

Center mount versus front and rear mounted outriggers

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Test Matrix

Test Vehiclesl 2001 Chevrolet Blazer 4x2l 2001 Toyota 4Runner 4x4

(VSC disabled)l 2001 Ford Escape 4x4l 1999 Mercedes ML320 4x4

(ESP disabled)Outriggersl Aluminum Outriggersl Titanium Outriggersl Carbon Fiber Outriggers

Maneuversl Slowly Increasing

Steerl NHTSA J-Turnl NHTSA Road Edge

RecoveryMore Maneuver and Vehicle Informationl In NHTSA

Phase IV report

3/05/03

Testing Locations and Conditions

Inertial Measurementsl S.E.A. Inc. – Columbus, Ohio

–VIMF (Vehicle Inertial Measurement Facility)Dynamic Testing Locationl TRC Inc. – East Liberty, OhioAmbient Conditionsl 36 to 71 °F

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Test Equipment

Test Vehicle Configurationl Nominal Loadl Equipped with

instrumentation– Further details in

Phase IV reportl Steering Controller

– Mounted to steering wheel– Electronics box placed in

rear seat footwall

Tiresl New, same make

model, size and DOT specification as supplied from manufacturer

l Pre-conditioned with 100 miles of initial service

l Inner tubes used in tires for Road Edge Recovery Maneuver

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OutriggersNHTSA Aluminum Outriggers

Designed at VRTCLowest costCan be produced in-houseHeight adjustmentl End of outriggerl Mounts

Castor wheelsWeight l 78 lbs per outrigger

(excluding mounts)

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OutriggersCarbon Fiber Outriggers

Carr EngineeringHighest cost Height adjustmentl Mounts

Load capacityl 3900 lbs vertical load

Castor wheelsWeightl 58 lbs per outrigger

(excluding mounts)

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OutriggersNHTSA Titanium Outriggers

Designed at VRTC1/3 cost of carbon fiberHeight adjustabilityl Mounts

Load capacityl 3900 lbs vertical loadl 1200 lbs friction load

Low-mu hemispherical skid padsWeight l 63 lbs per outrigger

(excluding mounts)

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Static Test Results VIMF

Effect of Outriggers on Static Parameters1 = least effect 3 = most effect

3(21-28%)

1(17-22%)

2(18-24%)

Roll Inertia

1(2-4%)

1(2-4%)

1(2-4%)

CG Height

3(8-21%)

2(8-20%)

1(7-20%)

Yaw and Pitch Inertia

3(78x2 = 156 lbs)

2(63x2 = 126 lbs)

1(58x2 = 116 lbs)

Outrigger Weight

AluminumTitaniumCarbon FiberCategory

l Average combined bumper assembly weighs 100 lbs l Instrumentation weighs approximately 150 lbsl Outrigger mounts weigh approximately 100 lbs

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Steering Angles

Slowly Increasing Steer maneuverMethods presented in previous presentationLargest difference 4.5%

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Dynamic Testing Two Wheel Lift Results

Two-wheel lift = 2 in. or more of simultaneous wheel liftDetermined from video dataEntrance speed for which two-wheel lift was first noticed

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ObservationsNHTSA J-Turns

Chevrolet Blazerl Carbon Fiber Outriggers

– Produced two-wheel lift at 62 mph– Test cutoff speed at 60 mph– Threshold speed not known

l Titanium and Aluminum Outriggers– No two-wheel lift at approximately 61 mph

l Carbon Fiber TWL when steered to leftl Similar responses when steered to right

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Chevrolet BlazerJ-Turn Test

0 2 4 6 8 10

-400

-300

-200

-100

0

Han

dwhe

el A

ngle

(deg

)

Tim e (s )

0 2 4 6 8 100

20

40

60

Veh

icle

Spe

ed (m

ph)

Tim e (s )0 2 4 6 8 10

-1

-0.5

0

Late

ral A

ccel

erat

ion

(g)

Tim e (s )

0 2 4 6 8 10

0

5

10

Rol

l Ang

le (d

eg)

Tim e (s )

0 2 4 6 8 10

-40

-20

0

Yaw

Rat

e (d

eg/s

)

Tim e (s )0 2 4 6 8 10

-20

0

20

40R

oll R

ate

deg/

s

Tim e (s )

Alum inum Outrigge rsTita nium Outrigge rsCa rbon Fibe r Outrigge rs

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ObservationsNHTSA J-Turns

Ford Escape, Mercedes ML320 and Toyota 4Runnerl Slight differences in responses for some testsl Nearly identical responses in others

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Mercedes ML320J-Turn Test

0 2 4 6 8 100

100

200

300

Han

dwhe

el A

ngle

(deg

)

Tim e (s )

0 2 4 6 8 100

20

40

60

Veh

icle

Spe

ed (m

ph)

Tim e (s )0 2 4 6 8 10

0

0.5

1

Late

ral A

ccel

erat

ion

(g)

Tim e (s )

0 2 4 6 8 10-8

-6

-4

-2

0

2

Rol

l Ang

le (d

eg)

Tim e (s )

0 2 4 6 8 10

0

10

20

30

40

Yaw

Rat

e (d

eg/s

)

Tim e (s )0 2 4 6 8 10

-20

-10

0

10R

oll R

ate

deg/

s

Tim e (s )

Alum inum Outrigge rsTita nium Outrigge rsCa rbon Fibe r Outrigge rs

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ObservationsRoad Edge Recovery

Roll Rate Feedback– Previous presentation by Garrick– More details in Phase IV report

Ford Escapel Roll responses varied as function of

which outriggers were installedl Aluminum Outriggers

– Extended dwell times at 40 and 50 mph

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Ford Escape Road Edge Recovery Test

0 2 4 6 8 10-300

-150

0

150

300

Han

dwhe

el A

ngle

(deg

)

Time (s )

0 2 4 6 8 100

20

40

Veh

icle

Spe

ed (m

ph)

Time (s )0 2 4 6 8 10

-1

0

1

Late

ral A

ccel

erat

ion

(g)

Time (s )

0 2 4 6 8 10

-5

0

5

10

Rol

l Ang

le (d

eg)

Time (s )

0 2 4 6 8 10-80-60-40-20

02040

Yaw

Rat

e (d

eg/s

)

Time (s )0 2 4 6 8 10

-60

-40

-20

0

20

40R

oll R

ate

deg/

s

Time (s )

Aluminum Outrigge rsTitanium Outrigge rsCarbon Fibe r Outriggers

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ObservationsRoad Edge Recovery

Chevrolet Blazer and Mercedes ML320l Produced two-wheel lift with each set of

outriggersToyota 4Runnerl Near identical responses

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Toyota 4Runner Road Edge Recovery Test

0 2 4 6 8 10

-200

0

200

Han

dwhe

el A

ngle

(deg

)

Time (s )

0 2 4 6 8 100

20

40

Veh

icle

Spe

ed (m

ph)

Time (s )0 2 4 6 8 10

-1

0

1

Late

ral A

ccel

erat

ion

(g)

Time (s )

0 2 4 6 8 10-10

-5

0

5

Rol

l Ang

le (d

eg)

Time (s )

0 2 4 6 8 10-40-20

0204060

Yaw

Rat

e (d

eg/s

)

Time (s )0 2 4 6 8 10

-20

0

20

40R

oll R

ate

deg/

s

Time (s )

Aluminum OutriggersTitanium OutriggersCarbon Fiber Outriggers

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Conclusions

Vehicle Inertial Measurementsl Influenced by outriggersl Titanium and Carbon

Fiber Outriggers have least overall influence

l Titanium Outriggers have least roll inertia influence

Slowly Increasing Steer Testl Outriggers had little

influence on the overall average handwheel angles

l Largest difference 4.5%

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Conclusions

NHTSA J-Turnl Blazer two-wheel lift

– Not clear that two-wheel lift is related to outrigger design or testing at vehicle’s dynamic threshold

l Other vehicles– no pronounced trends as

a function of outrigger installation

Road Edge Recoveryl Escape tests

– Differences in dwell timel Blazer and ML320

– Near identical TWL speeds regardless of outrigger installed

l Overall – Responses were very

similar

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Titanium Outrigger Chosen As NHTSA’s Preferred Outrigger

Highlightsl Safe for driverl Strongl Lowest roll inertia influence of

the three designs comparedl Cost less than carbon fiberl Use light-weight skid padsl Not much heavier than carbon

fiber design

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Outrigger Specifications

“Standard” Titanium Outriggerl 3500 to 7000 lb vehiclesl 3900 lbs vertical loadl 1200 lbs friction loadl 63 lbs per outrigger

“Short” Titanium Outrigger l Vehicles less than 3500 lbsl 2000 lbs vertical loadl 1200 lbs friction loadl 58 lbs per outrigger

3/05/03

Available

In Docket: NHTSA-2001-9663-75l Detailed Drawings

– “Standard” and “Short” Titanium Outriggers– Mounts and skid pads

l Outrigger CNC code– Files to machine exact replicas of NHTSA’s

“Standard” and “Short” Titanium OutriggersMore Information Contactl John Struble

– E-mail: jstruble@nhtsa.dot.gov– Phone: (202) 493-0246