A field investigation of the friction between cross-country skis and snow

TL;DR

This study introduces a novel mobile linear tribometer for field testing ski-snow friction, providing real-world data to better understand and optimize cross-country ski glide performance.

Contribution

It develops and validates a new experimental setup for measuring ski-snow friction in realistic conditions, and shares it as open source for further research and development.

Findings

Good agreement with previous experimental results

Provides real-world validation of laboratory data

Open source design for broader use

Abstract

Cross country skiing is an interplay between the active motion of the body of the skier and the physical interaction between the surface of the skis and the snow. Friction and glide between the ski base and the snow depend on the snow temperature, ski surface chemistry and roughness, dry friction with the snow crystals and liquid meltwater film flow properties. Although a great amount of resources are being spent on understanding glide and friction, a basic physical understanding of the phenomena at play is still at large and the methodology used for assessing the gliding quality of different full scale configurations is still coarse in real world applications, which limits novel development of robust methods to control and optimize glide. Such understanding and full scale testing is particularly important for designing new ski gliders. In the present work, we develop a novel experimental setup and use it to investigate through field experiments the basic mechanical phenomena that influence glide and friction of full scale skis on snow. The field setup features a mobile, novel linear tribometer allowing investigation with whole skis in realistic cross-country conditions (speed and load). The coefficient of friction between the skis and snow is obtained from a load cell, which reports the force necessary to pull a ski sled along a flat track. Simultaneously, thermistors measure the temperature at the ski-snow interface. In addition, a GPS measures displacement and velocity. The results obtained are in good agreement with several measurements reported from similar experiments, and provide a real-world validation of results obtained in the laboratory. In addition, we release the general tribometer setup as open source material in order to provide a foundation on which other research teams as well as cross-country teams can further iterate when designing later experiments.