ASTM WK96156
The task group has worked for a number of years to improve the XY reversals criteria. The current limits don’t work as desired in all cases: they sometimes allow rides with dynamics that can be injurious and, more commonly, fail rides that have historically operated without producing any reversal related issues. The dynamics of hundreds of amusement rides were examined to develop the criteria proposed in this ballot. These revisions are harmonized with the newly accepted EN 13814 (2026). The proposed criteria are similar to the current criteria in characterizing the severity of a reversal by both the speed of the direction change and the magnitude of the accelerations, but the metrics have been adjusted to better quantify these aspects of the reversal. The reversal speed is currently determined by the time between the opposing acceleration peaks. The proposal uses the maximum rate of change of the acceleration during the reversal as the metric. The amplitude criteria are currently fixed positive and negative limits while the proposed criteria use the total amplitude change as the metric. The following diagram compares the current to the proposed criteria: Additionally, the proposal limits the range of the reversal analysis to +/- 200 msec of the 0 g crossing. This prevents the analysis from being influenced by dynamics that are not part of the reversal. The ballot includes the definition for “acceleration event” and an expanded figure to clarify the language and intent of the criteria.
Date Initiated: 08-20-2025
Technical Contact: Charles Monson