Abstract

The sliding mechanism of alpine skis has been explained basically by means of meltwater lubrication (Bowden & Hughes, 1939). The sliding speed dependence of the kinetic friction coefficients (µk) were characterized by using three types of measuring apparati (Tomizawa et al., 2001). The obtained µk-values at the speed of 1 m/s of the short model ski (20 cm length) reached the same order with those of a normal ski in the literature (Colbeck, 1992). Therefore, just after a ski starts to slide, at probably very low velocity, the dominant sliding mechanism would be different from that of the normal speed of alpine skis, because there is no expectation of meltwater. Of interest to alpine skiers would be the relationship between the µk-values at high speed sliding and snow conditions. But it is difficult to analyze the effect of the snow parameters (crystal types, temperature, etc.) in obtained µk-values, because the values are very small (less than 0.05) and those contributions would be within the range of observed error. Further, unless the sliding conditions of gears or journal bearings are different from those of skis, the µk-values are of the same order (Stribeck, 1902 and Haizuka et. al., 2002). It has been suggested that small µk-values like 0.05-0.005 for ski sliding on snow would be controlled by the lubricant (meltwater) at the interlace between ski surface and snow. In these sliding conditions then, it is difficult to discuss the relationship between µk-values and snow parameters. In this paper, ski sliding features at very low speeds with a very short model ski are observed for typical natural snow types (new-snow and compacted snow) by means of two methods: (a) rotating snow track with a static model ski method and (b) natural sliding at a snow slope with a short model slider method. The specific behavior of low speed sliding, so-called “stick and slip phenomena” was observed for various sliding conditions by method (b). The effects of snow parameters on ski sliding were measured for several snow conditions by means of the slow speed (slower than 0.05 m/s) sliding with a short ski method. Einleitung