Stability & Vibration Damping in Alpine Skiing
For alpine skiers Heath Calhoun and Julia Mancuso the engineering and design of their skis will be critical to success at the 2014 Olympic Winter Games, especially when it comes to hard packed snow surfaces where vibrations on the slope impact speed and performance. “Science and Engineering of the 2014 Olympic Winter Games” is produced in partnership with the National Science Foundation.
LIAM McHUGH, reporting: For alpine skiers Heath Calhoun and Julia Mancuso, it's all about speed.
JULIA MANCUSO (Alpine Skiing Gold Medalist): Going 80, 90 miles an hour feels just awesome.
McHUGH: Mancuso has won eight major championship medals, including three Olympic medals, the most ever by a woman alpine skier. Paralympic skier and Iraq War veteran Heath Calhoun competed in the 2010 Winter Paralympics in Vancouver and is a medal favorite in Sochi.
HEATH CALHOUN (U.S. Paralympic Alpine Skiing Team): As a beginner skier, it’s about making it down the hill so that you can have fun and at this level it’s so much different.
McHUGH: For both athletes, the engineering and design of their skis will be critical to their success at the 2014 Winter Olympic - and Paralympic – Games, especially when it comes to hard-packed snow surfaces where vibrations and bumps on the slope impact speed and performance.
MANCUSO: The vibrations definitely vary between snow conditions if it’s really icy or bumpy.
McHUGH: On the alpine ski slope, vibration is unavoidable and too much can be a bad thing, impairing performance and potentially costing athletes like Mancuso the gold.
KAM LEANG (University of Nevada, Reno): Vibration causes the ski to lose contact with the surface of the snow and that intermittent contact causes a problem in terms of the skier being able to control the ski.
McHUGH: Kam Leang is an engineer at the University of Nevada, Reno, who is funded by the National Science Foundation. He and his team of graduate students are using nano-composite materials to reduce unwanted vibration in high performance skis.
LEANG: It allows you to go faster and feel more comfortable and you could control the ski better.
McHUGH: A ski is already a composite. It is made of two are more materials, like fiberglass and steel, that when combined together form a new material with different chemical or physical characteristics. But what makes Leang's research so innovative is his use of NANO-scale carbon tubes.
LEANG: If you take your hair, the diameter of your hair is on average about 100 microns, okay?
McHUGH: The carbon nanotubes Leang's team uses are between 10,000 and 100,000 times smaller in diameter than a hair on your head. When combined with larger materials, nano-materials can be used to improve the strength, flexibility and increase the stability of anything from skis to car parts. Stronger than steel and lighter than fiberglass, long, thin carbon nanotubes are added to a glue called epoxy. The mixture holds the layers of the ski together and helps spread out energy that travels through the ski when a force is applied to it, reducing unwanted vibrations.
LEANG: We’ve seen about anywhere between 10 to 15 percent improvement in damping. That may not seem like a lot but it can add up.
McHUGH: For Heath Calhoun, the vibration issue is more complex because he does not have knees to help stabilize himself. Instead, he must rely on his specially designed mono-ski to do this for him.
CALHOUN: It never occurred to me that there was, you know, disable ski racing. And so I went in and I asked, “where can I take this?”
TOM WATSON (Watson Performance): We’re basically using technology between the seated position and the ski to absorb bump forces.
McHUGH: Tom Watson is an off-road motorcycle engineer who works on the Paralympic A team mono-skis. He designed a new shock absorber system optimized for Health Calhoun.
WATSON: So I have to take into consideration what’s happening all the way from the snow to the rider’s seated position.
McHUGH: Using a shock absorber that he initially created for off-road motorcycles, Watson was able to tweak Calhoun's mono-ski to help maintain contact with the snow.
WATSON: The ski can’t go faster unless it’s contacting the snow. So the shock absorbers duty is to keep the ski in contact with the snow as much as possible.
McHUGH: The shock absorber uses flexible plates to control the amount of fluid that travels through the chamber. When Calhoun hits a bump, fluid fills the chamber and helps him glide over it, keeping him stable.
WATSON: The shock absorber doesn’t actually control the speed, but what it does do is controls the athletes potential to go faster.
McHUGH: On his mono-ski, Calhoun is able to reach speeds up to 70 miles per hour.
CALHOUN: Looking back on, I mean, everything – I’ve completely changed everything I did from then; the equipment, skis, to my entire technique has changed.
McHUGH: With each Olympic Winter Games, engineers are improving equipment, helping athletes like Heath Calhoun and Julia Mancuso reach higher speeds, and perhaps even reach the medal podium.
MANCUSO: And now going into Sochi, I really feel, you know, ready to perform and ready to win those gold medals.