With the results of this survey in mind, the following actions can be anticipated:
• Manufacturers of axle nut systems will develop and publish simple installation instructions to include identification of "an acceptable range of preload adjustment" and the description of how the process should be accomplished.
• Personnel involved in maintenance of wheel-end assemblies will be advised of when and how often periodic wheel-end inspections should be performed. (This recommendation was offered by the National Transportation Safety Board in a 1995 special investigation report, Medium/Heavy Truck Wheel Separations.)
• This year, there will be action on the part of some trailer component manufacturers to introduce improved versions of precisely adjustable wheel-end fasteners.
• There will be efforts by some component manufacturers to provide the improved maintenance instructions needed by mechanics involved in trailer maintenance to accurately install a minimum of end play within the wheel-end assemblies.
• A newly designed trailer safety nut having an automatic feature to assure precisely controlled preload adjustment using a simplified procedure will become available.
• Unfortunately, it is unlikely the National Highway Traffic Safety Administration will issue any regulations in the foreseeable future to change trailer wheel-end maintenance procedures for improvement of highway safety.
But, don't give up. Relief is on the way.
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. His inventions include equipment to facilitate measurement of camber and toe angularity of trailer axles. He holds patents covering axle spindle nuts for commercial tractor-trailer axles. These wheel-end systems provide superior methods for tapered roller bearing adjustment to assure controlled bearing preload for extended service operations.
Research on controlled preload for tapered roller bearing adjustment.
Allows controllable and repeatable preload in trailer wheel-end systems