Improved Preload Adjustment Methods

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					              | Guest Editorial |
                                                                                 By G. Allan Hagelthorn, P.E., President, Rather Engineering, P.C.




              Improved Preload
              Adjustment Methods
              Some actions can be anticipated
                 From personal observations while working in             For safety, it is my recommendation that             • Preload adjustment of tapered roller bear-
              the engineering world, I have found that it is not         attempts to adjust tapered roller bearings              ings will provide improved performance.
              unusual for engineers to explain complex technical         with preload not be made unless the manu-            • Maintenance can be simplified with
              requirements in ways that are not easily understood.       facturer involved issues specific instructions           improved practices.
              Service technicians have often developed their             for that purpose.                                    With the results of this survey in mind, the
              expertise logically without adequate instructions        • At the present time, the Recommended              following actions can be anticipated:
              from the engineers, and this has led to difficulties.       Practices (RPs) published by the Technology          • Manufacturers of axle nut systems will
                 Problems can occur if engineers fail to realize         and Maintenance Council (TMC) do not                    develop and publish simple installation
              that deviations of maintenance procedures might            describe how “controlled preload” can be                instructions to include identification of “an
              occur in a manner they did not anticipate.                 installed by service technicians. Rather, the           acceptable range of preload adjustment”
                  It remains for all engineers to be constantly          RPs state that the component manufactur-                and the description of how the process
              aware that the instructions they develop might             ers of axles, bearings, oil seals and axle nuts         should be accomplished.
              either be improperly presented or misunderstood.           should be requested to provide appropriate           • Personnel involved in maintenance of
                 It is also a primary responsibility for all engi-       instructions.                                           wheel-end assemblies will be advised
              neers to monitor product deficiencies and to              • There has not been any definitive infor-                 of when and how often periodic wheel-
              provide worthy assistance to maintenance provid-           mation published to inform those involved               end inspections should be performed.
              ers whenever necessary.                                    in commercial vehicle maintenance how                   (This recommendation was offered by the
                 None of us are perfect and mistakes will some-          wheel-ends should be inspected. Nor have                National Transportation Safety Board in a
              times happen. So, when unforeseen problems do              those who are responsible for preventa-                 1995 special investigation report, Medium/
              occur, it is necessary that everyone communicate           tive maintenance been instructed on how                 Heavy Truck Wheel Separations.)
              effectively to resolve the issue.                          often the wheel-end components should be             • This year, there will be action on the part
                 Having designed wheel-end systems for high-             disassembled and visibly inspected.                     of some trailer component manufacturers
              way trailers, and being exposed to numerous wheel                                                                  to introduce improved versions of precisely
              separation accidents over the past 25 years, I am                                                                  adjustable wheel-end fasteners.
              aware that it is a very complex situation.                                                                      • There will be efforts by some component
                 Because there are some obvious problems that                    Newly                                           manufacturers to provide the improved
              remain unattended, I feel compelled to make                                                                        maintenance instructions needed by
              recommendations to reduce the frequency of                      developed                                          mechanics involved in trailer maintenance
              problems associated with inappropriate adjust-                                                                     to accurately install a minimum of end play
              ment of tapered roller bearings.                              concepts and                                         within the wheel-end assemblies.
                 Within the engineering community dealing with                              
				
DOCUMENT INFO
Description: [G. Allan Hagelthorn] is a professional mechanical engineer with nearly 45 years of experience. Since 1982 he has owned and operated his own consulting business, Rather Engineering. He is a member of a number of engineering associations, including SAE and TMC. He has served on TMC committees developing new methods for improved trailer maintenance. As a member of SAE, he helped develop new standards applicable to trailer components.
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