The document describes the design of a four ball tribometer to test lubricants. A team was split into controls, structures, and fabrication subgroups. The tribometer tests lubricants under high contact forces and measures resulting wear scars. After several design iterations, the final design uses a pneumatic cylinder to apply force, an axial transducer to measure force, and additional controls for safety, temperature, and rpm. The team completed fabrication but additional work was needed on instrumentation and controls to obtain test results.

1. Four Ball
Accelerated Wear Tester
Department of Mechanical Engineering
Fall Semester 2014
Mechanical System Design
CONTROLS TEAM STRUCTURES TEAM FABRICATION TEAM
Ana Dungan Whitney Stregles Daniel Griffin
Kelsey Kaht Robert Nalecz Colin Holliday
Steve Soto Riley Shay Casey Sheppard
John Willis Jordan Ansley Michael Spaulding
Ibrahim Ahmed

2. Background and
Design Development

3. Four Ball Tribometer
❖ Tests a lubricant’s extreme pressure properties under high contact
in pure sliding or pure rolling motion
❖ In this design, a ½ inch diameter ball is pressed against three
similar balls at a set force. The top ball will spin against the three
lower balls creating wear scars on the balls.
❖ The force and torque applied to the system are measured and this
data, along with the appearance of wear
scars, enables the user to conclude
which lubrication is the most efficient

4. Example Set-Up
Note: This is not our 4-Ball Tribometer

5. Objectives
Successfully design and fabricate a four ball accelerated wear
tester:
➢ Thoroughly research and develop major concepts and compare
constraints
➢ Develop a design that rotates a top ball under a force causing friction
and wear on the bottom 3 balls
➢ Develop a prototype to test major concepts
➢ Develop methods for measuring wear, torque, load, and temperature
➢ Establish a budget for the project

6. ASTM Standards
ASTM D2266 ASTM D4172 ASTM D5183
Value Tolerance Value Tolerance Value Tolerance
Force Applied
40 kgf 0.2 kgf 15 kgf 0.2 kgf 40 kgf Not Given
392 N 2 N 147 N 2 N 392 N Not Given
Lubricant
Temp
75 C 2 C 75 C 2 C 75 C 2 C
167 F 4 F 167 F 4 F 167 F 4 F
Speed 1200 rpm 60 rpm 1200 rpm 60 rpm 600 rpm Not Given
Duration 60 min 1 min 60 min 1 min 60 min Not Given
Oil Level very top of cup 3mm above top of balls 3mm above top of balls
[1]

7. Design Process
❖ The design of the 4-ball tribometer was changed several
times.
❖ The initial design involved a lever and an inline motor.
❖ The second design included the drill press that was donated to
our team and the previous lever idea.
❖ The final design utilizes a pneumatic cylinder and was
upgraded from the use of a manual regulator to the
integration of a data acquisition concept and force sensor
components to control the applied force.

8. Initial Design
❖ Basic Concept
➢ Not technologically advanced
❖ Inline Motor
❖ Lever Arm
➢ Strategically placed fulcrum
➢ Force applied to the bottom
❖ Wear Measurement
➢ Microscope and Volume Displacement

9. Second Design
❖ Lever arm design incorporated onto
the drill press
❖ Existing platform mount retains
translating shaft
❖ Two Cups Inside One Another
➢ Increase Repeatability
❖ Weights used to apply load
❖ Wear Measurement via Camera

10. Second Milestone Design
❖ Air cylinder with manual
regulator to apply force from the
top
❖ Thrust bearing under the cup for
self-alignment
❖ Fixed bottom plate for improved
repeatability and accuracy
❖ Force sensors implemented on
the cup
❖ Wear measurement camera
❖ Hot plate for heating the

11. Concerns After Milestone Two
❖ Pneumatic Cylinder:
➢ Manual Air Regulation Accuracy
➢ Air Cleaning
❖ Data:
➢ No Way to Directly Calculate
Normal Load
➢ Controlling Motor Speed
❖ Cup:
➢ Dual Cup Design for Repeatability
Created an Extra Moment to
Consider
❖ Force Application:
➢ Not Constant Over Time
➢ Weights Capability to Fall
Decreased Safety Factor
❖ Heating and Cooling:
➢ Overheating would lead to
welding of balls
➢ Maintaining the temperature at
the standard without
overheating
❖ Safety:
➢ Temperature Intensity and Ball

12. Controlling Applied Force
❖ Manual Regulator
➢ Budget-friendly
➢ Not accurate
➢ Needs to be controlled better
❖ Controls Loop
➢ Continuously checks and displays data
➢ Maintains desired force output
➢ Costly

13. Final Re-Design Concepts
Design Changes:
❖ Added Filter to the Pneumatic Cylinder
❖ Added Electronic P-Valve
➢ Controls loop feeds data to constantly regulate pressure
❖ Redesigned for Addition of Axial Transducer
➢ Input Data relays to the DAQ for direct normal force measurement
❖ Self-Alignment Plate Design for the Axial Transducer
❖ Replacement 3-Phase Motor to Allow for the Addition of Variable Speed Drive
❖ Added Heating Elements and Temperature Controller
❖ Added Auto-Stop Controlled by the Temperature Controller

14. Final Design
❖ Drill press was further modified
❖ Pneumatic cylinder added to apply force
❖ Axial Transducer incorporated for direct
force measurement
❖ Auto-Stop Controller incorporated for
increased safety
❖ Addition of plate to platform for mounting
cup and axial transducer

15. Theoretical Testing
and Equations

16. Theoretical Testing
❖ Finite Element Analyses (FEA) were performed to determine the
theoretical stresses and deformation results based on the designed
components under the standard conditions determined.
❖ Theoretical Calculations were used to determine the dimensions of the air
cylinder
Given:
➢ Lever Arm Length= 4 in.
➢ Bore Size= 7/16 in.
➢ Gear Ratio= 13:1
➢ Pinion Diameter= I in.
➢ From ASTM D2266 Standards, Applied Force= 88.18
lbf

17. Collet FEA

18. Thermal FEA
Thermal analysis
determined that no
insulation is necessary.

19. Theoretical Calculations
❖ Tangential Force at Pinion:
➢ By considering the relationship between
forces and the mechanical advantage of
the gear ratio, Ft was calculated.
❖ The Moment about Pinion, M :

20. Theoretical Calculations
❖ Required Force Output from Air Cylinder:
➢ Using the Equation for Moment at the End of a
Rotating Rod as a Result from the Air Cylinder
Force, FA:
➢ Working Area of Cylinder, A:
❖ Required Internal Pressure of 7/16 in. Bore Air
Cylinder:
➢ From Pascal’s Law, P:

21. Budget

22. Budget
❖ The initial budget presentation was
estimated at $1,575.31
❖ The budget was re-presented based off
of the concerns presented by Dr. Vlcek
and Dr. Molina at $3,538.70
Original Total Budget:
$1,575.31
Proposed New Budget:
$3,538.70
Difference:
$1,963.39

23. Force Components Budget

24. Control’s Budget

25. Fabrication Components Budget

26. Final Budget

27. Technical Drawings
Components Designed by the Group:
❖ Chuck/Collet Set-Up:
➢ Chuck
➢ Stopper
❖ Cup Set-Up:
➢ Cap
➢ Retainer
➢ Cup

28. Stopper
**Note: All Dimensions are in Inches

29. Chuck
**Note: All Dimensions are in Inches

30. Cap
**Note: All Dimensions are in Inches

31. Retainer
**Note: All Dimensions are in Inches

32. Cup
**Note: All Dimensions are in Inches

33. Centering
Plate
**Note: All Dimensions are in Inches

34. Fabrication Issues
❖ Collet Design Problem 1: Threads caused DA collet to become
non-concentric
➢ Solution: Eliminated threads that tighten down on collet
❖ Collet Design Problem 2: Not enough friction to keep DA
collet from turning during operation
➢ Solution: Use dowel to hold collet in place with a hex cap
screw that will pull DA collet into chuck

35. Fabrication Images

36. Cup/Transducer/Plate Assembly

37. Cup/Transducer/Plate Assembly

38. Pneumatic Piston Set-Up

39. Chuck Set-Up

40. Instrumentation/Controls

41. Review:
❖ Block Diagram
❖ Temperature
❖ Torque
❖ RPM
❖ DAQ
❖ Power Supplies
Instrumentation and Controls
Recent Additions:
❖ Axial Force
❖ New Motor
❖ RPM Control
❖ Emergency Stop

42. Instrumentation block diagram
Instrumentation and Controls

43. Force/Torque Controls
Torque Transducer
Force Controller
Pressure Valve
DAQ

44. ❖ Single Phase Induction Motor
❖ No Control Available
❖ Encoder would be counting
total revolutions
Original RPM Controls

45. New RPM Control
❖ New 3 Phase, ½ hp motor
will reach speed specified in
standards
➢VFD controller will
maintain constant RPM AC Motor 0.5 HP

46. Emergency Stop
❖ Arduino
controller and
programming
were used to
implement this
feature Arduino Controller

47. Measuring Torque and Axial Force
❖ Thrust and torque load cell
simplifies torque and axial
force measurement
❖ No longer rely on calculated
axial force and torque
Thrust and Torque Load Cell

48. Force/Torque Controls

49. Temperature Controls
Temperature sensor Temperature controller Temperature actuator

50. Temperature Controls

51. ❖ Torque and Thrust Biaxial Sensor
❖ Thermocouple
❖ Microcontroller
❖ Power Relay
❖ Miniature Relay
Power Supply Controls

52. Power Supply Controls

53. Calibration and Testing
❖ Signal Conditioning
❖ Force
❖ Temperature
❖ Auto-shutoff
❖ RPM

54. Calibration and Testing
❖ Signal Conditioning
➢ Built three inverted op-amp circuits to amplify
temperature, torque, and force signals
❖ Force Sensor
➢ Calibrated by using calibration charts
➢ Tested by listening to pressure change as actuator
or valve is activated by controller

55. Calibration and Testing
❖ Temperature
➢ Tested by boiling
water and
observing heating
element activation

56. Calibration and Testing
❖ Auto-shutoff
➢ Tested auto-start by observing activation of
drill
➢ Tested auto-stop by boiling water and
observing deactivation of drill
❖ RPM
➢ Ordered three-phase motor and VFD controller
➢ Encoder temporarily set-up for RPM counting
until new motor arrives

57. Results
The Results of the tribometer were unfortunately not
able to be recorded due to the DAQ set-up being
incomplete.

58. Summary
❖ Completed:
➢ Concept Development
➢ Multiple Design Changes
➢ Final Design Approval
➢ All Fabrication
❖ Incomplete:
➢ Three Phase Motor
➢ VFD Controller
➢ Auto-Stop Controller
➢ DAQ Output Results
➢ Final Set-Up and Wire
Organization

59. References
[1] ASTM Standards:
ASTM D2266-01(2008), Standard Test Method for Wear Preventive Characteristics of
Lubricating Grease (Four-Ball Method), ASTM International, West Conshohocken, PA, 2008,
www.astm.org
ASTM D4172-94(2010), Standard Test Method for Wear Preventive Characteristics of
Lubricating Fluid (Four-Ball Method), ASTM International, West Conshohocken, PA, 2010,
www.astm.org
ASTM D5183-05(2011), Standard Test Method for Determination of the Coefficient of
Friction of Lubricants Using the Four-Ball Wear Test Machine, ASTM International, West
Conshohocken, PA, 2011, www.astm.org

60. Gantt
Timeline

61. Concept Comparison Results
Comparison Constraints: Ease of Use, Cost, Size, Safety,
Accuracy, Maintenance, Repeatability
Table 1: Concept Comparison Group Totals

62. QFD

63. Air Cylinder Set-Up
Figure 15: Air Cylinder Model (Side View)

64. Air Cylinder Set-Up
Figure 16: Air Cylinder Detail Drawing

65. Air Cylinder Set-Up
Table 3&4: Air Cylinder Calculations and Possible Scenarios
Rough Calculations
Total Needed Downward Force 150 lb
Tang. Force from Pinion (1" Diam) 11.53 lb
Moment Produced at Pinion 5.765 lb*in
Rack/Pinion Gear Ratio 13:01

66. Air Cylinder Set-Up
Table 5: Air Cylinder Details

67. Air Cylinder Set-Up
Table 6: Air Cylinder Set-Up Parts List

68. Temperature Measurement
ASTM D2266, D4172, and
D5183 Standards require a
lubricant temperature of 75℃
maintained within 2℃.
Figure 18: Omega Thermocouple [3]

69. Temperature Measurement
LabVIEW writes Excel file
that contains time and
temperature data.
Figure 19: Temperature Output

70. Temperature Measurement
Manufacturer Price Specifications Quantity
Omega $35.00 -200 to 1250 ℃
1McMaster-Carr $35.00 -200 to 1250 ℃
TEMPCO $35.00 -200 to 1250 ℃
Table 9: Thermocouple Manufacturer Comparisons

71. Temperature Control
PID control provides more
accuracy
Figure 20: AUTONICS temperature
controller [4]

72. Temperature Control
Manufacturer Price Specifications Quantity
AUTONICS $143.00 +/- 1 ℃
1
Omega $195.00 +/-0.5 ℃
Table 10: Temperature Controller Manufacturer Comparisons

73. Heating
Manufacturer Price Specifications Quantity
Omega $25.00 10W/in2
2
McMaster-Carr $26.00 10W/in2
Table 11: Heating Element Manufacturer Comparisons

74. RPM Measurement
Real time RPM:
❖ LabVIEW program
creates Excel file
❖ Excel file contains time,
encoder counts, and
RPM
Encoder
Figure 23: Encoder Motion
Schematicω = (θ2-θ1)/( T2-T1)

75. RPM Measurement
The max RPM required
by the three standards
used is up to 1200 rpm
and the smallest
accuracy required is ±60
rpm.
Figure 24: Karlsson Robotics Rotary
Encoder [7]

76. RPM Measurement
Figure 28: Display of LabVIEW Data

77. RPM Measurement
Manufacturer Price Specifications Quantity
Karlsson Robotics $50.00 up to 6,000 RPM
1
Automation Direct $90.00 up to 5,000 RPM
Table 13: Rotary Encoder Manufacturer Comparison

78. Data Acquisition
❖ Sampling rate is an
important factor for
DAQ selection.
❖ Digital counter required
for easier RPM
measurement.
Figure 30: National Instruments DAQ [8]

79. Data Acquisition
Manufacturer Price Specifications Quantity
National Instruments $300.00 48 kS/s
1
LabJack $114.00 50 kS/s
Table 14: DAQ Manufacturer Comparison

80. Power
❖5 Volts provided to the
encoder and force sensors
by a DC power supply.
Figure 34: Power Supply [11]

81. Power
Manufacturer Price Specifications Quantity
TDK-Lambda $18.00 5V
1
CUI $28.00 5 V
Table 16: DC Power Supply Manufacturer Comparison