Tridem Drive Tractors:Research & Operational

Experience

TridemTridem Drive Tractors: Drive Tractors:Research & OperationalResearch & Operational

Experience Experience

Forest Engineering ResearchInstitute of Canada - Vancouver, BCForest Engineering ResearchForest Engineering ResearchInstitute of Canada - Vancouver, BCInstitute of Canada - Vancouver, BC

FERIC’s Tridem ResearchFERIC’sFERIC’s TridemTridem Research Research

• Started in 1990• Initially undertaken to address

mobility challenges• Steering / vehicle dynamics• 20+ reports• Configurations with tridem drive

now approved - BC(8) Alberta(9)

•• Started in 1990Started in 1990•• Initially undertaken to addressInitially undertaken to address

mobility challengesmobility challenges•• Steering / vehicle dynamicsSteering / vehicle dynamics•• 20+ reports20+ reports•• Configurations with Configurations with tridemtridem drive drive

now approved - BC(8) Alberta(9)now approved - BC(8) Alberta(9)

Evolution of Western CanadianLog Truck Configurations

Evolution of Western CanadianLog Truck Configurations

1960s1960s 1980s1980s

Available to IndustryAvailable to Industry

Tridem Drive55% Traction Improvement

Tridem Drive55% Traction Improvement

Regulatory ApprovalRegulatory Approval

Preliminary SteeringTesting: Alberta

Preliminary SteeringPreliminary SteeringTesting: AlbertaTesting: Alberta

Development of SteeringPerformance Measure:

Lateral Friction Utilization (LFU)

Development of SteeringDevelopment of SteeringPerformance Measure:Performance Measure:

Lateral Friction Utilization (LFU)Lateral Friction Utilization (LFU)

Vertical Load on Steering TiresVertical Load on Steering TiresVertical Load on Steering Tiresxxx <<< 0.80.80.8

coef of adhesioncoefcoef of adhesion of adhesion

Lateral Friction UtilizationLateral Friction UtilizationLateral Friction Utilization

111Side Force at Steering TiresSide Force at Steering TiresSide Force at Steering Tires

Sensitivity AnalysisTridem tractor / tridem pole trailer

Sensitivity AnalysisSensitivity AnalysisTridemTridem tractor / tractor / tridemtridem pole trailer pole trailer

-20

-15

-10

-5

0

5

10

15

20

-20 -15 -10 -5 0 5 10 15 20

Parameter Variation (%)

Cha

nge

in L

FU (%

)

Drive group load Trailer group load Steering axle load Drive group spread

Tractor wheelbase Trailer group spread Interaxle spacing Hitch offset

Influence of tractor wheelbase on steering axleload

Influence of tractor wheelbase on steering axleInfluence of tractor wheelbase on steering axleloadload

5000

5500

6000

6500

7000

7500

6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9Tractor wheelbase (m)

Rec

omm

ende

d st

eerin

g ax

le lo

ad (k

g)

BC - Pole trailers BC - Semi-trailers Alberta - Pole trailers Alberta - Semi-trailers

Influence of drive group spread on steering axleload

Influence of drive group spread on steering axleInfluence of drive group spread on steering axleloadload

5500

6075

5200

5300

5400

5500

5600

5700

5800

5900

6000

6100

6200

2.74 3.02

Drive group spread (m)

Rec

omm

ende

d st

eerin

g ax

le lo

ad (k

g)

Tridem Tractor/ Tandem Pole TrailerTrailer group load 17 000 kgDrive group load 23 000 kgTractor wheelbase 6.6 m

Lateral friction utilization of selectedconfigurations

Lateral friction utilization of selectedLateral friction utilization of selectedconfigurationsconfigurations

0.6390.690

0.785

0.714

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

B-train (5500 kg steers) B-train (5000 kg steers) Tridem tractor/ tridemsemi-trailer (7300 steers)

Tridem tractor/ tandempole trailer (7300 steers)

Late

ral F

rictio

n U

tiliz

atio

n

Performance Standard < 0.80

Steering testsconducted by

B.C. Gov’t

Steering testsconducted by

B.C. Gov’t

VehicleDynamicAnalyses

VehicleDynamicAnalyses

25

30

35

40

45

0.25 0.3 0.35 0.4 0.45

SRT (g)

Payl

oad

(tonn

es)

5 Axle TRI/TRI TAJ QUAD DDOG TA/JP/TR

Static Rollover ThresholdStatic Rollover ThresholdStatic Rollover Threshold

Better

25

30

35

40

45

1.70 1.80 1.90 2.00 2.10 2.20 2.30

RWA

Payl

oad

(tonn

es)

5 Axle TRI/TRI TAJ QUAD DDOG TA/JP/TR

Rearward AmplificationRearward AmplificationRearward Amplification

Better

25

30

35

40

45

0.4 0.45 0.5 0.55 0.6 0.65

LTR

Payl

oad

(tonn

es)

5 Axle TRI/TRI TAJ QUAD DDOG TA/JP/TR

Load Transfer RatioLoad Transfer RatioLoad Transfer Ratio

Better

B-Train trials begin in Alberta: 1995 / 96B-Train trials begin in Alberta: 1995 / 96B-Train trials begin in Alberta: 1995 / 96

Use with pole trailers approvedin Alberta - 1996

Use with pole trailers approvedUse with pole trailers approvedin Alberta - 1996in Alberta - 1996

Use with pole trailers approvedin BC – October 1997

Use with pole trailers approvedin BC – October 1997

Verification of5th wheel

offset limits

Verification of5th wheel

offset limits