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The scope of this SAE Recommended Practice, trailer axle alignment, is to identify the dimensional limits of, and a method to, establish a perpendicular relationship between the king pin centerline and the axle centerline at its midpoint. Various types of equipment are commercially available which can be used for this measurement which provides varying degrees of accuracy, but none can be endorsed by SAE. The most fundamental methods of measurement will be described here, but other equipment is available if a greater degree of accuracy is desired.

This test procedure is used to determine the steady-state directional control response of vehicles by measuring steady-state cornering behavior. Due to the wide range of operational conditions to which a vehicle can be subjected, the results of this testing do not provide a complete description of a vehicle's total dynamic behavior; in particular, the procedure does not test the vehicle's response during transient maneuvers. To fully assess a vehicle's total dynamic behavior, it would be necessary to conduct other test procedures in order to evaluate the vehicle's performance as a whole. The extent of instrumentation and the required accuracy of the measurement will be dependent on the goals of the personnel conducting the test. If it is desired simply to determine the general performance characteristics of a vehicle, then this test can be conducted with minimal instrumentation and test item preparation.

This test procedure is used to determine the steady-state directional control response of vehicles by measuring steady-state cornering behavior. Due to the wide range of operational conditions to which a vehicle can be subjected, the results of this testing do not provide a complete description of a vehicle's total dynamic behavior; in particular, the procedure does not test the vehicle's response during transient maneuvers. To fully assess a vehicle's total dynamic behavior, it would be necessary to conduct other test procedures in order to evaluate the vehicle's performance as a whole. The extent of instrumentation and the required accuracy of the measurement will be dependent on the goals of the personnel conducting the test. If it is desired simply to determine the general performance characteristics of a vehicle, then this test can be conducted with minimal instrumentation and test item preparation.

There are two ways to assess the characteristics of ride vibrations of a vehicle during its operation. Subjective evaluation and objective measurement. Subjective assessments of the ride vibrations experienced by drivers during ride evaluations are generally performed by a panel of drivers and/or passengers who are instructed to operate or ride a group of vehicles in a predetermined manner in order to subjectively assess the levels and characteristics of ride vibrations. Figures 6A through 6C show examples of subjective evaluation forms presently in use. The disadvantages of the subjective method include need for careful experimental design, need for statistically unbiased samples, complexity of human perceptions of vibrations, and difficulty in comparing qualitative data of vehicles evaluated at different times and/or by different groups of people. Often ride characterization is not an easy task using only qualitative or descriptive terms.

There are two ways to assess the characteristics of ride vibrations of a vehicle during its operation. Subjective evaluation and objective measurement. Subjective assessments of the ride vibrations experienced by drivers during ride evaluations are generally performed by a panel of drivers and/or passengers who are instructed to operate or ride a group of vehicles in a predetermined manner in order to subjectively assess the levels and characteristics of ride vibrations. Figures 6A through 6C show examples of subjective evaluation forms presently in use. The disadvantages of the subjective method include need for careful experimental design, need for statistically unbiased samples, complexity of human perceptions of vibrations, and difficulty in comparing qualitative data of vehicles evaluated at different times and/or by different groups of people. Often ride characterization is not an easy task using only qualitative or descriptive terms.

The test procedure applies to roll coupled units such as straight trucks, tractor semitrailers, full trailers, B-trains, etc. The test is aimed at evaluating the level of lateral acceleration required to rollover a vehicle or a roll-coupled unit of a vehicle in a steady turning situation. Transient, vibratory, or dynamic rollover situations are not simulated by this test. Furthermore, the accuracy of the test decreases as the tilt angle increases, although this is a small effect at the levels of tilt angle used in testing heavy trucks. The test accuracy is accepted for vehicles that will rollover at lateral acceleration levels below 0.5 g corresponding to a tilt table angle of less than approximately 27 degrees. Even so, the results for heavy trucks with rollover thresholds greater than 0.5 g could be used for comparing their relative static roll stability.

The test procedure applies to roll coupled units such as straight trucks, tractor semitrailers, full trailers, B-trains, etc. The test is aimed at evaluating the level of lateral acceleration required to rollover a vehicle or a roll-coupled unit of a vehicle in a steady turning situation. Transient, vibratory, or dynamic rollover situations are not simulated by this test. Furthermore, the accuracy of the test decreases as the tilt angle increases, although this is a small effect at the levels of tilt angle used in testing heavy trucks. The test accuracy is accepted for vehicles that will rollover at lateral acceleration levels below 0.5 g corresponding to a tilt table angle of less than approximately 27 degrees. Even so, the results for heavy trucks with rollover thresholds greater than 0.5 g could be used for comparing their relative static roll stability.