Evaluation of ski-binding-boot system safety using torque testing

Abstract

This study evaluated release torque values for rental ski-binding-boot (S-B-B) systems that had one to four seasons use in a popular New Zealand commercial ski area. The proportions of S-B-B systems in classes of deviation from the reference release moment were determined according to the international equipment safety requirements from ASTM F1063-03, ASTM F1064-03, ASTM F939-06, ISO 13993: 2001, and ISO 11088-2006 (E). A randomly chosen sample of 9 % (124 skis/62 pairs) of S-B-B systems from the total ski rental fleet was tested using a Wintersteiger calibration machine. There were a high percentage of Class I deviations in the rental fleet: 50 % (2 seasons), 95 % (3 seasons), and 64 % (4 seasons). Class 1 deviations do not require corrective action; however, increased sampling is indicated. Based on the high percentage of Class I deviations the entire fleet should be inspected. Class II deviations that required immediate corrective action were found in 48 % of the S-B-B with two seasons of use. Only 8 % of the rental fleet had Class III deviations warranting removal from the rental fleet. The heel-pieces of S-B-B systems that had two or more seasons of use were nine times more likely to be out of tolerance than those with only one season of use; however, there was only a small increase in the proportion of toe-pieces out of tolerance for older compared to newer S-B-B systems. These differences may be due to age or to different models of S-B-B systems. The policy of retiring ski rental equipment after three or four seasons of use appears to be inadequate to ensure the supply of safe equipment.