BALL JOINT TRIBOLOGY

Powers and Sons LLC

PURPOSE

• TO ISOLATE CONTRIBUTIONS TO WEAR IN A BALL JOINT AND IMPROVE WEAR LIFE– LUBRICATION– BEARING MATERIAL– INTERNAL PRESSURE– SURFACE FINISHES– BALL HARDNESS

COMPLAINT BY CUSTOMER CODE PASSENGER CAR TIE ROD ENDS, PITMAN, IDLER ARMS

MILEAGE > 36,000 (17,518 RECORDS-SWIS DATA)

OTHER19%

RIDE/HANDLING4%

FREEPLAY22%

NOISE55%

Complaint Codes by Verbatims >36000 miles 3a130

Squeak

Noise

loose

rubbing

play

grinding

clunk

groan

vibration

worn

whines

other/no comment

SqueakNoiselooserubbingplaygrindingclunkgroanvibrationwornwhinesother/no comment

CAUSAL FACTORS RETURNED PARTS ANALYSIS

>36000 MILES 79 PIECES

GREASE46%

SEAL/FORGING8%

SEAL/STUD19%

CAP/FORGING14%

GOOD PART13%

P-DIAGRAM

Tie Rod Ball Joints

Noise Factors

Signal Factor (M)

Customer turns the wheel

Response (Y) Ideal Function

Error States

Transmit motion / load uniformly

Control Factors•Seal / forging interface•Seal material•Spin Pressure (cap to forging)•Cap to forging interface•Bearing surface finish•Selection of lubricant•Dunnage

•Seal / stud interface•Rotating torque of joints•Geometry•Bearing Material

•Excessive free play•Squeaks•High initial rotating torque

•Plant Grease on steering stop•Customer usage- Police/Taxi; demographics•Contamination•Proximity to brake rotor•In plant handling damage•Misdiagnosis

Design Variables Which Affect Ball Joint Life

• Seal Effectiveness• Grease Type• Static Internal Pressure• Bearing Material• Ballstud Surface Finish• Bearing Surface Finish

Development Testing

• Current industry standards– Bench wear test– Vehicle durability tests– Vehicle fleet tests

• Current designs pass ES and Vehicle Tests meaning current test methods are inadequate for identifying High Mileage concerns

Identify Team• Powers & Sons - Gene Messenger Talon Harvey

Chris Fink August Rose• Ford R&VT- Lou Mastrofrancesco • Dow Corning- Dr. Chris Hsu Gary McIntyre • Dupont Automotive• BASF• Bayer Chemical• Freudenburg - NOK• CAM-CAR TEXTRON Townsend Engineered Products• Defiance

BASELINE WEAR TEST SMOOTH NYLON 6/6, CLIMAX GREASE, Ra32 BALL, 10N NORMAL LOAD

TRAVEL +/-1MM, 5 Hz

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

150 15150 30150 45150 60150 75150 90150 105150 120150 135150 150150 165150 180150 195150 210150 225150

CYCLES

DR

AG

(N)

POINT AT WHICH WEAR BEGINS

Development of Test • Goal

– Develop Key Life Test– Simulate interaction between component materials in a ball joint

• First inputs were developed– The Normal load to apply between surfaces – Length of path travel – Frequency of path travel

• Then wear test began with the following DOE variables:– Grease type– Ballstud surface finish– Bearing material type – Bearing material surface finish

DOE - Full Factorial 32 runs (4x2x2x2) for Cameron Plint studyLoad of 10N, speed of 5 Hz, and stroke of +/- .5mm

Run Grease 0,1,2,3 Plastic 0,1 Stud finish 0,1 Bearing finish 0,11 Climax Nylon Ra32 smooth2 Climax Nylon Ra32 fine3 Climax Nylon Ra5 smooth4 Climax Nylon Ra5 fine5 Climax Acetal Ra32 smooth6 Climax Acetal Ra32 fine7 Climax Acetal Ra5 smooth8 Climax Acetal Ra5 fine9 Nye Nylon Ra32 smooth10 Nye Nylon Ra32 fine11 Nye Nylon Ra5 smooth12 Nye Nylon Ra5 fine13 Nye Acetal Ra32 smooth14 Nye Acetal Ra32 fine15 Nye Acetal Ra5 smooth16 Nye Acetal Ra5 fine17 LT278 Nylon Ra32 smooth18 LT278 Nylon Ra32 fine19 LT278 Nylon Ra5 smooth20 LT278 Nylon Ra5 fine21 LT278 Acetal Ra32 smooth22 LT278 Acetal Ra32 fine23 LT278 Acetal Ra5 smooth24 LT278 Acetal Ra5 fine25 PG75 Nylon Ra32 smooth26 PG75 Nylon Ra32 fine27 PG75 Nylon Ra5 smooth28 PG75 Nylon Ra5 fine29 PG75 Acetal Ra32 smooth30 PG75 Acetal Ra32 fine31 PG75 Acetal Ra5 smooth32 PG75 Acetal Ra5 fine

STATIC INTERNAL JOINT PRESSURE

• MEASURED JOINT ROT. TORQUE = .56 N-M• BEARING/BALL SURFACE CONTACT = 938 SQ. MM• EFFECTIVE TORQUE RADIUS = 9.44 MM• DRAG = TORQUE/RADIUS = .56/.00944 = 59N• NORMAL LOAD = DRAG/COEFF. OF FRICTION = 59/.02=2950N• STATIC INTERNAL JOINT PRESSURE= NORMAL

LOAD/SURFACE CONTACT AREA = 2950/938 = 3.15 N/SQ. MM

WORKING PRESSURE UNDER LOAD

• WORKING RADIAL LOAD = 600N• PROJECTED BALL AREA = 270 SQ.

MM.• PRESSURE = LOAD/AREA = 600/270 =

2.22N/SQ. MM.

NORMAL LOAD DETERMINATION

• TOTAL PRESSURE = STATIC + WORKING = 3.15+2.22 = 5.37 N/SQ. MM.

• CAMERON PLINT MEASURED CONTACT AREA = 2 SQ. MM

• NORMAL LOAD = PRESSURE * AREA = 5.37*2 = 10.74 N

• C-P WEAR TESTING RUN @ 10N NORMAL LOAD

TRAVEL DETERMINATION

• 90TH PERCENTILE ARTICULATION/ ROTATION TRAVEL < 6 DEGREES

• LINEAR TRAVEL FOR 22MM BALL AT 6 DEGREES = 1.17 MM

• C-P WEAR TESTING RUN AT +/- 1 MM TRAVEL

Climax Grease Failure Modes

• Oxidation instability• Poor moisture resistance• Reacts adversely under static design and

road load pressure

Oxidized Climax

CAMERON PLINT WEAR TEST NYLON 6/6, SMOOTH BEARING, Ra5 BALL STUD,

10N LOAD, +/- 1 MM TRAVEL, 5 HZ

0

0.5

1

1.5

2

2.5

3

3.5

0

3750

0

7500

0

1125

00

1500

00

1875

00

2250

00

2625

00

3000

00

3375

00

3750

00

4125

00

4500

00

4875

00

CYCLES

DR

AG

(N

)

LT2/78

CLIMAX

NYE 880

PG75

EFFECT OF BEARING MATERIAL ON WEAR LIFE CLIMAX GREASE SMOOTH NYLON 6/6 BEARING

Ra5 BALL STUD, 10N LOAD, +/- 1MM TRAVEL, 5HZ

0

0.2

0.4

0.6

0.8

1

1.2

0 75000 150000 225000 300000

CYCLES

DR

AG

(N

)

NYLON 6/6

ACETEL

EFFECT OF BALL SURFACE FINISH ON COEFFICIENT OF FRICTION CLIMAX GREASE, SMOOTH NYLON 6/6 PLATE,

10N NORMAL LOAD, +/- 1MM TRAVEL, 5HZ

0

0.2

0.4

0.6

0.8

1

1.2

0 60000 120000 180000 240000 300000 360000 420000

CYCLES

DR

AG

(N

)

Ra 5 BALL

Ra 32 BALL

EFFECT OF BEARING SURFACE FINISH ON WEAR LIFE ACETEL BEARING, Ra32 BALL, CLIMAX GREASE

10N LOAD, +/- 1MM, 5 Hz

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

150 60150 120150 180150 240150 300150

CYCLES

DR

AG

(N

)

FINE BEARING

SMOOTH BEARING

EFFECT OF NORMAL LOAD ON DRAG CLIMAX GREASE, SMOOTH NYLON 6/6 PLATE, Ra32 BALL

+/-1MM STROKE, 5 Hz

0

1

2

3

4

5

6

7

0 60000 120000 180000 240000 300000

CYCLES

DR

AG

(N

)50N NORMAL LOAD

10N NORMAL LOAD

BASELINE TO BEST 10N NORMAL LOAD, +/- 1MM STROKE, 5Hz

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0

1500

00

3000

00

4500

00

6000

00

7500

00

9000

00

1E+0

6

1E+0

6

1E+0

6

2E+0

6

2E+0

6

2E+0

6

2E+0

6

2E+0

6

2E+0

6

CYCLES

DR

AG

(N

)

BASELINE GREASE, Ra32 BALL, SMOOTH NYLON 6/6 BEARING

PG75, Ra5 BALL, FINE ACETAL BEARING

39

CONTRIBUTION TO WEAR LIFE IMPROVEMENTSBASED UPON F DISTRIBUTION WITH TEST SUSPENDED AT 4000

MINUTES OR FAILURE

BEARING MATERIAL

STUD FINISH

BEARING FINISH

GREASE

Coefficient of Friction with Nylon 6/6 bearing and Ra32 ball stud at full temperature range measured on Cameron Plint at Dow

0

0.2

0.4

0.6

0.8

1

1.2

-60 -50 -40 -30 -20 -15 -5 0 15 25 30 40 50 65 75 85 95 10

Temperature (degrees Farenheit)

Co

effi

cien

t of F

rict

ion

ClimaxPG75LT 2/78NO-lube

Operating Temperature Range Rotating Torque on 2000 M.Y. Windstar Tie Rod Ends

0

20

40

60

80

100

120

140

160

-40 -20 0 20 40 80 100 120 140

Temperature (deg. Fahrenheit)

Ro

tati

ng

To

rqu

e (i

n. l

bs.

)

LT278

Climax

LT278/Climax

PG75/Climax

PG75

no grease

Climax grease, 10N load, 5Hz, Ra 32 on Smooth Nylon

0

1

2

3

4

5

6

7

8

9

10

0 10 20 30 40 50 60

time, min

For

ce, N

-70

-60

-50

-40

-30

-20

-10

0

Tem

pera

ture

, C

Frictional force, N

Temp, degree C

Point to fail

Conclusions from Cameron Plint

• Grease is primary constituent to improving joint life– Grease of choice is Dow Corning PG75

• Minor improvement is found with:– Acetel vs. Nylon 6/6– Polished ballstud surface – Fine texture bearing surface vs. current smooth

texture

• Lowering Ball Joint Internal Static Pressure will add to joint life

42

PN96 PITMAN ARM (3590) WARRANTY VS DATE OF PRODUCTION

0

5

10

15

20

25

30

35

Apr-9

6Jun

-96Au

g-96

Oct-96

Dec-96

Feb-97

Apr-9

7Jun

-97Au

g-97

Oct-97

Dec-9

7Feb

-98Ap

r-98

Jun-98

Aug-9

8Oct-9

8

DATE OF PRODUCTION

R/1

000

12MIS

18MIS

24MIS

REVISED GREASE FROM CLIMAX TO NYE 880

INTERIM GREASES VS BASELINE CLIMAX

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

400000 800000 1200000

CYCLES

DR

AG

(N

)

LT278/CLIMAX BLEND

92A/CLIMAX BLEND

CLIMAX GREASE

Design Solutions

• New Joint- bearings, grease, and ballstuddeveloped through:– Benchmarking– Cameron Plint Testing– ES Bench Testing– 150K mile AEMS fleet test