High Temperature Wheel Bearing Testing – an Electrifying Improvement Barbara Carfolite and Autumn Chadwick ExxonMobil Research and Engineering Technology Center Clinton, NJ 08809 USA Abstract ASTM D3527 Standard Test Method for Life Performance of Automotive Wheel Bearing Grease has been in place since the 1970s. While several ASTM sponsored programs have been conducted over the past 30 years within ASTM Subcommittee D02.G0.05 Functional Tests - Temperature to address what has been identified as variability in results generated using this equipment across multiple laboratories, the method remains virtually unchanged from its original issue. This is currently the only high temperature dynamic test in ASTM D4950 Standard Classification and Specification for Automotive Service Greases developed by the National Lubricating Grease Institute (NLGI) for the assessment of greases. This article provides a new perspective on the impact of motor selection on the precision of the test, based on the experience of one laboratory. Introduction In the 1960s and 1970s, as automotive OEM’s (Original Equipment Manufacturers) started using higher speed roller bearings instead of ball bearings in combination with disc brakes, bearing operating temperatures increased and the industry needed a test to measure the high-temperature performance of lubricating grease used in these applications. Such a test was issued by the American Society for Test and Materials (ASTM) in the 1970s. This test method, ASTM D3527, Standard Test Method for Life Performance of Automotive Wheel Bearing Grease, uses a modified front wheel hub/spindle bearing assembly that is subjected to cycles of elevated temperature for an extended time period.1 ASTM D3527 was modified in 1985 to increase the severity and improve the test precision and accuracy. However, after several decades and numerous efforts to improve the precision and accuracy of this test by ASTM Subcommittee D02.G0.05 Functional Tests-Temperature, the method remains relatively unchanged. An internal investigation was conducted by ExxonMobil Research and Engineering (EMRE) to evaluate means for improving the precision and accuracy of ASTM D3527. The findings are presented in this paper. Background ASTM D3527 was released over 40 years ago, and to this day, it remains one of the few, broadly available dynamic tests for measuring the high-temperature life of lubricating grease. However, due to the poor precision and accuracy of D3527, ASTM issued a ballot in 2017 to withdrawal this standard. The ballot was unsuccessful, mostly due to the fact that the test was included in several industry and military specifications. In addition, ASTM D4950 Standard Classification and Specification for Automotive Service Greases includes ASTM D3527 as one of the key tests for measuring the upper operating temperature limit of grease.2 However, the accuracy and precision of D3527 are limited.3 In addition, the D3527 method uses small tapered roller bearings that that are no longer used by the automotive industry. NLGI is evaluating alternative test options to replace D3527.
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