Reduction of Friction on Artificial Ski Surfaces: Athlete Surface Interactions
Reduction of Friction on Artificial Ski Surfaces: Athlete Surface Interactions Professor Peter Styring EPSRC Senior Media Fellow Chemical & Process En...
Reduction of Friction on Artificial Ski Surfaces: Athlete Surface Interactions Professor Peter Styring EPSRC Senior Media Fellow Chemical & Process Engineering The University of Sheffield STARRS, Loughborough, 18 September 2007
Waxing the Bases • Without a wax there is high friction between the ski base and the plastic (less so on alpine snow, but still a factor). • What about artificial snow? • The wax is usually applied using a hot iron to get the wax into the porous base. • Excess wax is scraped off and the base then polished with a fine horsehair brush. • This process requires a workshop and toolkit to carry it out effectively. • It is a very time consuming process that requires experience for it to be done well consistently.
What Happens to the Wax as we Ski on an Artificial Slope? • Friction and abrasion on the base of the ski causes the wax to be lost. • Performance decreases as we ski due to these losses. • On a plastic slope waxes are lost quickly. • Artificial snow is more abrasive than alpine snow. • Plastic slope and snow slope skiing are really two different sports. • What we need is a way to constantly replace any lost wax as a thin, renewable layer
A Continuous Waxing System
Flowrate of lubricant Q Q
U
W
h
Drag Force ~ Area x shear force L ~ W L μ U/h Lubricant Q ~ Viscosity (User Control)
Fdrag Ski Contact Area (Discipline Dependent)
hWU
Fdrag ∝
ηA Q
Lubricant Flowrate (User Control)
How Does it Work? • Skiers apply pressure to the skis • Reverse camber causes the Wildfire rise plate to bend which forces fluid through a pipe to the ski base • The more pressure that is applied, the greater the flow • No external energy source is used, just the skier (FIS Equipment Rules Compliant) • The lubricants are environmentally friendly and biodegradable • The continuous flow, continually reduces friction
How Can We Confirm it Works? • Glide tests are carried out to measure the time taken between two points to simulate a Downhill track (DH). We can also look at Giant Slaloms (GS) and Super-Gs. • The skier must adopt a tuck position to minimise wind resistance. • Consistency is essential for the results to be statistically acceptable • Controls are run at regular intervals (Fair Testing) • Mountain tests would be ideal but for initial studies we can use UK artificial facilities at Sheffield Ski Village and SNO!zone Castleford
Data from Bob Kirk
Abrasion and Flow 4.8
No Fluid Flow
4.7
Fluid Flow On 4.6
4.5
Time (s)
4.4
4.3 Hot Wax Continuous Wax
4.2
4.1
4
3.9
3.8 0
100
200
300
400
Distance (m)
500
600
700
Weight & Balance
Artificial Snow Moguls
‘How Science Works’
‘How Science Works’
Engineering Gold! TeachersTV 17 October 2007
Relative Performance of the Wildfire System in Different Tests Test
GS
DH
DH
DH
DH
Surface
Dendix
Dendix
Snowflex
Artificial Snow
Alpine Snow
% Speed increase
23
32
48
8
1-2
Data taken from Snowsport England Validation Tests
Wildfire on Artificial Snow WF50W
Comments
Averages
%improve
4.80
0.0
4.55
5.3
4.58
4.6
Tank drained 4.57 4.61 4.57
Run History 5.10 5.00 4.90 Time (s)
Run 1 2 3 4 5 6 7 8
Time (s) Race wax PP3 4.64 4.82 4.95 4.55 4.69
Race Wax
4.80
PP3
4.70
WF50W
4.60 4.50 4.40 0
1
2
3
4
5
6
Run Number
7
8
9
Athlete Perception • Phil Smith at SSV: “It feels like I’m skiing on snow!” • Holly Cutler at SSV: “Much faster and smoother” • Graham Bell (Laterns, Austria): “There was no loss of edge control” • Becky Hammond at SSV: “I got much higher out of the pipe!” • Phil Smith at SSV: “I can feel when the system is switched off. Without it the drag is greater and bits of the slope start to melt on to my skis!”
Wear on SnowFlex
Summary • Controlled blind tests have been validated by Snowsport England. • Results show enhanced performance on all surfaces while adhering to FIS Equipment Regulations. • In addition to performance enhancement there is added base and slope materials protection. • We are looking to using the technology in the FIS World Cup but our prime objective is at the 2010 Winter Olympics in Vancouver.
Special Thanks • Dr Alex Routh (Cambridge) • Graham Bell, Hannah Handford-Styring, Becky Hammond, Phil Smith, Jon Smith, Holly Cutler • Bob Kirk (MechE) • Head Skis GmbH & Atomic Skis GmbH • Glasshead Ltd • The Polymer Centre • Sheffield University Enterprises Limited
