Temperature Below a Gliding Cross Country Ski

Schindelwig, Kurt; Hasler, Michael; Putten, Joost van; Rohm, Sebastian; Nachbauer, Werner

doi:10.1016/j.proeng.2014.06.065

Cited by 16 publications

(11 citation statements)

References 7 publications

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“…The thermal theory presented here reveals an important result for skis and sleds: previous measurements of snow-slider interface temperatures effectively confirmed the lack of self-lubrication. Measurements on skis (Colbeck and Warren, 1991; Colbeck and Perovich, 2004; Schindelwig and others, 2014) and sleds (Lever and Weale, 2012; Lever and others, 2016) have consistently shown that contact temperatures remain below 0°C under the action of sliding friction. Colbeck and Perovich (2004) showed that sunlight absorption can bring contact temperatures closer to 0°C, but ski runs conducted at night raised contact temperatures to only −7.8°C from −9.2°C.…”

Section: Discussionmentioning

confidence: 98%

Evidence that abrasion can govern snow kinetic friction

et al. 2018

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The long-accepted theory to explain why snow is slippery postulates self-lubrication: frictional heat from sliding melts and thereby lubricates the contacting snow grains. We recently published micro-scale interface observations that contradicted this explanation: contacting snow grains abraded and did not melt under a polyethylene slider, despite low friction values. Here we provide additional observational and theoretical evidence that abrasion can govern snow kinetic friction. We obtained coordinated infrared, visible-light and scanning-electron micrographs that confirm that the evolving shapes observed during our tribometer tests are contacting snow grains polished by abrasion, and that the wear particles can sinter together and fill the adjacent pore spaces. Furthermore, dry-contact abrasive wear reasonably predicts the evolution of snow-slider contact area, and sliding-heat-source theory confirms that contact temperatures would not reach 0°C during our tribometer tests. Importantly, published measurements of interface temperatures also indicate that melting did not occur during field tests on sleds and skis. Although prevailing theory anticipates a transition from dry to lubricated contact along a slider, we suggest that dry-contact abrasion and heat flow can prevent this transition from occurring for snow-friction scenarios of practical interest.

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Section: Discussionmentioning

confidence: 98%

Evidence that abrasion can govern snow kinetic friction

et al. 2018

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“…Despite relatively low slider speeds (0.005–0.1 m s −1 ), they measured low friction ( μ = 0.03 at −2°C) but observed no water films thicker than their detection limit of 50 nm. Colbeck and Warren (1991) and Lever and Weale (2012) measured the thermal response of skis and sleds, respectively, to sliding over snow, and Schindelwig and others (2014) used infrared (IR) sensors to measure snow-surface temperature under a ski. In each case, several degrees of warming occurred, but the sensing areas were too large to confirm that melting occurred at the snow-grain contact points.…”

Section: Introductionmentioning

confidence: 99%

The mechanics of snow friction as revealed by micro-scale interface observations

et al. 2017

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The mechanics of snow friction are central to competitive skiing, safe winter driving and efficient polar sleds. For nearly 80 years, prevailing theory has postulated that self-lubrication accounts for low kinetic friction on snow: dry-contact sliding warms snow grains to the melting point, and further sliding produces meltwater layers that lubricate the interface. We sought to verify that self-lubrication occurs at the grain scale and to quantify the evolution of real contact area to aid modeling. We used high-resolution (15 µm) infrared thermography to observe the warming of stationary snow under a rotating polyethylene slider. Surprisingly, we did not observe melting at contacting snow grains despite low friction values. In some cases, slider shear failed inter-granular bonds and produced widespread snow movement with no persistent contacts to melt (μ < 0.03). When the snow grains did not move and persistent contacts evolved, the slider abraded rather than melted the grains at low resistance (μ < 0.05). Optical microscopy revealed that the abraded particles deposited in air pockets between grains and thereby carried heat away from the interface, a process not included in current models. Overall, our results challenge whether self-lubrication is indeed the dominant mechanism underlying low snow kinetic friction.

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“…In cross-country skiing, coefficients of sliding friction between 0.027 and 0.047 for unwaxed skis and between 0.021 and 0.029 for waxed skis were reported. 10,11 Current roller skis have resistance coefficients similar to those seen in cross-country skiing on good snow conditions. Therefore, roller skis allow training similar to cross-country skiing.…”

Section: Discussionmentioning

confidence: 90%

Determination of the rolling resistance of roller skis

Schindelwig

Mössner

Hasler

et al. 2016

Proceedings of the Institution of Mechanical Engineers, Part P:

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The rolling resistance of skis used in roller skiing competitions should resemble the gliding resistance of crosscountry skis to allow specific training and moving patterns for crosscountry skiing and to guarantee equal opportunities for athletes in roller ski races. Therefore, the purpose of this work was to develop a portable rolling resistance meter to precisely measure the rolling resistance of roller skis. Measurements were based on recordings of the angular deceleration of a flywheel due to the rolling resistance between a roller ski's wheel and the flywheel's steel surface. Rolling resistance coefficients of four roller ski types ranged between 0.019 and 0.025. Measurements of the rolling resistance coefficient showed a precision of 1.26%. Substantial rolling resistance coefficient variations (10%) were observed for wheels of the same type. Furthermore, the rolling resistance coefficient was found to be negatively correlated with normal load or ambient temperature. The proposed rolling resistance meter is appropriate to determine the rolling resistance coefficient of roller skis' wheels precisely.

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Temperature Below a Gliding Cross Country Ski

Cited by 16 publications

References 7 publications

Evidence that abrasion can govern snow kinetic friction

Evidence that abrasion can govern snow kinetic friction

The mechanics of snow friction as revealed by micro-scale interface observations

Determination of the rolling resistance of roller skis

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