There are those of us who get a little nervous driving at 90 miles per hour (140 kph) protected by steel, air bags and anti-lock brakes. And then there are those of us who ask, "Can we remove all protective mechanisms, get close enough to kiss the pavement and lie down so we can't see real well?" Replace "pavement" with "ice," and you've got yourself the makings of a luge team.
Luge is one of the most dangerous sports in the Olympic games, and the athletes who race down an icy, high-banked track at speeds typically up to 90 mph are a special breed.
Although it's very fast, luge might seem like a fairly easy sport to try. You just lie down on your sled and push off, right? Wrong! "It can also look as if an athlete is not doing that much when the sport is shown on the TV, but we're actually steering the whole way down and trying to be relaxed – there's so much to do, but when you're doing it right, the spectator at home doesn't get a feel for it," said British luger Adam Rosen in an interview for the International Olympic Committee (IOC) website
In this article, we'll learn all about Olympic luge and find out what it takes to finish first.
The Luge Track
In Olympic luge, the slider (usually not called a "luger") lies down on a fiberglass sled, with no braking system, and heads feet-first down an icy track.
There are actually two types of luge: natural track and artificial track.
- In natural-track luge (naturbahn), the track is made of packed snow and ice. The slope on a natural luge track is no greater than 1.5 percent (about 1 degree), meaning that for every 100 feet (30 meters) of track, the maximum elevation change is 1.5 feet. Speeds can reach up to 50 mph (80 kph). Anyone can make a natural luge track if he has enough snow to work with.
- In artificial-track luge (kunstbahn), the track is steeper and has high-banked turns, with an average slope of 8 to 11 percent (about 5 to 6 degrees). Speeds on an artificial track can reach 90 mph (140 kph) or even more -- Austrian slider Manuel Pfister holds the world record for fastest luge speed at 95 mph (154 kph).
Olympic luge is kunstbahn, and it's not for the meek. Two weeks before the start of the 1964 Innsbruck Games, a slider from the British luge team died on the luge track during a practice run. Crashing at 90 mph on an icy track can be very ugly, and luge athletes often face serious injuries if they come off the sled. In 2010, Georgian Nodar Kumaritashvili died while training for the Vancouver Olympics when he lost control of his sled. He flew off the track and into a metal pole. The types of artificial luge tracks used in the Olympics are tremendous structures that embody a lot of technology. There are fewer than two dozen artificial luge tracks in the world.
An Olympic track is artificially refrigerated. The course is usually a reinforced concrete track with evaporators buried in the concrete. The evaporators cool the track to 12 degrees F (-11 C). The track is then sprayed with water to create the approximate 2-inch surface of ice.
A typical luge course is less than 1 mile (1.6 km) long and drops about 300 to 400 feet (90-120 m) or 30 stories in the course of a one-minute run. The configuration includes straightaways, left and right turns, downhills (and sometimes a short uphill) and at least one S-type curve combination like the "labyrinth," which consists of three or four consecutive turns with no straightaways between them.
Just staying on the sled would be a feat for a highly trained athlete. But sliders don't just have to stay on the sled -- they also need to maintain a strictly aerodynamic form, watch where they're going and try to keep the sled in the "sweet spot" that will carry them smoothly between turns, all while facing up to 5 Gs on particularly strenuous courses. According to Canadian slider Jeff Christie in a CBC interview, the consequences of giving in to the G-forces can be pretty painful:
For the level of danger sliders face on each run, the amount of protective gear they wear is shockingly sparse. In the next section, we'll examine the equipment of luge.
For all the complexity of navigating a luge course, the equipment involved is pretty limited. There's a sled, a racing suit, gloves, boots and a helmet. Every piece of equipment in luge is designed for utmost aerodynamics, minimal friction and top speed.
A luge sled is a high-tech machine. It's made primarily of fiberglass and steel, and it's custom-built for each athlete based on his or her height, weight and proportions. Luge teams contract companies to design and build their sleds based on custom specifications. The sled weighs between 50 and 60 pounds (23-27 kg) and runs from the slider's shoulders to his or her knees, and there is no head support.
The sled consists of:
- Two steels - The steels are the only part of the sled that contacts the ice. Steels are made of metal and are very sharp.
- Two bridges - The bridges are made of steel. They connect to the runners and support the pod.
- Two runners (sometimes called kufens, which is German for "runners") - Runners are usually made of fiberglass and are the main steering mechanism of the sled. The curved section (the bow) of each runner is flexible. Using their legs, sliders apply pressure to one or the other runner bow in order to steer through the course (they can also steer by making small movements with their shoulders to shift their weight).
- Racing pod - The pod is the platform on which the slider lies. It's usually made of fiberglass.
- Two grips - There is a handle on either side of the pod for the slider to hold on to during the race.
A slider's racing gear consists of:
- Helmet - A luge helmet has a rounded visor that extends all the way under the slider's chin to minimize air resistance.
- Racing suit - A luge suit is a smooth, rubberized, skin-tight suit designed to minimize air friction. Sliders typically compete in brand-new suits so there's no chance of flapping or rippling. Photo courtesy San Diego Low Speed Wind Tunnel
- Spiked gloves - Luge gloves have spikes sewn into the fingertips and/or knuckles to provide traction when the slider is paddling over the ice at the start of the race.
- Racing booties - The zippers on luge booties draw the sliders' feet into a straight position (as opposed to flexed). This position minimizes frontal drag (see "The Physics" section).
During a race, something like a snag in a racing bootie can affect the slider's aerodynamics enough to mean the difference between a win and a loss. Sliders typically race in brand-new gear to reduce the chance of an unnoticed imperfection.
In the next section, we'll put this all together and see what happens during a luge run.
The Luge Race
The Olympic luge competition has four divisions: Men's singles, women's singles, gender-neutral doubles and team relay. Since a higher weight is advantageous in luge (see the next section), doubles teams are typically all male. Most international races besides the Olympics have single sliders doing two runs each. Both times are added, and the winner has the lowest combined time. In the Olympics, singles luge competition consists of four runs instead of two (doubles still perform only two runs), all of which count toward the final time. In this way, the Olympics tries to weight consistency as a major factor in a win.
Since every luge track is different from every other luge track, there are no blanket World or Olympic records in luge. There are only track records.
At the start of the luge course, there are two handles, one on each side of the track. The slider grabs these handles and rocks back and forth to build momentum for the start. To begin the race, the slider propels himself onto the course and immediately uses his hands (in the spiked gloves) to paddle through the first 10 feet or so of the track. This helps him gain some speed before lying down on the sled.
Approaching the start of the downhill, the slider lies down on the sled on his back. This is his body position for the remainder of the run. From this position, with his head lifted only enough to have some idea where he's going, the slider navigates the twists, turns and straightaways with his body simultaneously tight and relaxed. This is not an easy state to achieve -- the body must be stiff enough to maximize acceleration (any wobbling or looseness would increase friction between the sled and the track) and yet relaxed enough to absorb the intense forces acting on the slider throughout the run. Since steering increases friction, the slider steers as little as possible, only pressing on the bows when necessary. Most of the time, control is a matter of being one with the sled and letting gravity do its thing.
If a slider crosses the finish line without his sled, the run is thrown out, which means automatic disqualification since all of the run times count toward the final score. However, the slider can cross the finish line carrying his sled, and the run counts.
In 2014, team relay was added to the Olympics. (It became a sport in 2010). Each team has a women's single, a men's single and a double sled. The next slide begins once the previous sled has pressed an overhead touchpad at the bottom of the track. The team with the lowest time after all three sleds have finished is the winner.
Olympic luge is timed to the thousandth of a second -- for comparison, the blink of an eye takes 12 thousandths of a second.
Luge is timed using photoelectric sensors at the start and finish. The setup has a light transmitter/receiver pair at each end of the run. The transmitter is on one side of the track, and the receiver is on the other. At the start, the slider triggers the timer when he crosses the line because he blocks the light beam. At the finish line, he stops the timer the same way.
At the 1998 Nagano Games, the time difference between the women's gold and the women's silver was two-thousandths of a second, the smallest margin in luge history. This miniscule difference between first and second place drew a great deal of controversy, and engineers were called in to calculate the system's margin of error. They found it to be approximately two-thousandths of a second. This triggered a high-tech addition to the timing setup. Since the 1998 Games, luge timing systems have been calibrated before each race using a GPS satellite with an atomic clock that's accurate to the 10-10 seconds (every GPS satellite has an atomic clock built in. The calibration process is basically about synchronizing the timers on the luge course with the atomic clock on the satellite. With a modified GPS receiver built into the timing system, the satellite can trigger the start timer and then trigger the stop timer after a certain interval. If the time noted by the satellite and the time noted by the ground system matches to at least the second thousandth of a second, the timing system is ready for a race.
Completing a luge run is an exhilarating and physically demanding task. Let's take a look at the physics involved in making it from the start to the finish.
The physics concepts involved in a luge run are fairly basic:
- force and inertia - A great amount of force is required to get the slider moving at the start of the course.
- gravity - The force of gravity pulls the slider and the sled down the track.
- friction - The amount of friction between the sled and the track works against gravity and is a prime determining factor in speed.
- aerodynamic drag: Aerodynamic drag acts on the slider/sled combination to resist its motion through the air. The lower the drag, the higher the speed.
- G-force: A G is equal to the force exerted by gravity. It is the force acting on a body that is accelerating. If a slider is facing 3 Gs through a turn, his body feels three times heavier than his actual weight when he is at rest.
At the start of the course, the slider/sled unit is at rest. The slider's goal is to begin the run with the utmost speed, so he needs to propel the racing unit onto the course with as much force as possible to overcome its inertia (its desire to remain at rest). If the slider weighs 198 pounds (89 kg), and the sled weighs 50.6 pounds (23 kg), that's a combined mass of about 247 pounds (112 kg). By rocking back and forth at the top of the track, the slider needs to generate enough momentum to propel 247 pounds through the first 10 feet (3 meters) of the course in something like 2 seconds to achieve a really good start.
As the slope begins, the slider lies down on the sled and lets gravity take over. In luge, higher weight means greater speed. The greater the weight of the athlete, the greater the force of gravity pulling her down the track. One of the forces standing in the way of gravity is friction. To reduce the amount of friction between the sled and the track, the steels are polished with numerous substances, including sandpaper and diamond paste.
Another force acting against the pull of gravity throughout the run is aerodynamic drag. Aerodynamic drag consists of air friction and form drag. In luge, when air runs over the top of the rider, it interacts with the materials of the helmet and racing suit. This results in air friction. To reduce air friction, racing suits are slippery and skin-tight, and the visor on a luge helmet is rounded and extends all the way under the slider's chin so there are no air pockets. The interaction between the air and the frontal shape of the slider/sled combination results in form drag. In addition to using the most aerodynamic shapes for the sleds, the slider tries to further minimize form drag by maintaining an aerodynamic body position. The less area he presents to the oncoming air, the better. Lifting the head an inch so the slider can better see the track increases form drag and can add several thousandths of a second to the run time. In doubles luge, the taller athlete lies in front, between his partner's legs, to achieve a smoother profile. Many sliders spend hours training in wind tunnels to find the ideal body position to minimize drag.
Probably the most physically battering points on a luge run are the turns, and especially the turn combinations, when G-forces increase. Acceleration and deceleration throughout a luge course puts an average force of up to 3 Gs on a slider's body. Forces can reach up to 5 Gs in banked turns, when centrifugal force* adds another dimension to the forces acting on the slider.
Centrifugal force pulls the slider outward in the turn. To maintain speed, the slider must perfectly balance the centrifugal force with the force of gravity pulling him downward through the course. This means finding the "sweet spot" and staying there. If the forces are balanced, the sled will smoothly move through each turn and back into the straightaways. If they are unbalanced, the slider will have to steer too much, slowing down the run.
With so much at stake in so little time, luge athletes train all year to shave a few thousandths of a second off their time. In the next section, we'll find out what's involved in luge training.
*Centrifugal force does not actually exist. It is a way of describing what happens to the body when it encounters high-speed rotation -- see University of Virginia Physics: Centrifugal Force to learn more.
The start is the most important part of the race. It's the time when the slider is most in control, so his or her training can have the greatest affect on the outcome. Luge athletes build tremendous upper body strength for the start, when they'll propel themselves, their sled and any extra weights onto the course. Hand strength is also required for the start, when the slider paddles as quickly as possible for the first several feet of the course. Since a slider's body faces up to 5 Gs during a run, he must be in overall excellent physical and mental condition to manage the 50-second attack on his body and his focus.
In the summer months, luge athletes train hard to build upper body muscles through swimming, weight training and calisthenics. In the winter months, typical luge training includes practice runs every day. Sometimes, they'll practice only starts, developing strength, agility and technique. While the athletes are doing practice runs and starts, coaches are analyzing it all using footage from digital cameras, specialized software and prior reports from athletes about what they're feeling on the course. Luge coaches have a deep understanding of sleds and luge physics, and they use the information they gather to make tiny adjustments to the sleds to maximize speed and control for each slider.
The training technology for the U.S. luge team includes:
Luge training also involves sessions in wind tunnels, during which athletes figure out the form that achieves minimum aerodynamic drag. Monitors above the slider's head and at his feet display a number that represents the amount of drag he's experiencing. During the session, with wind blowing over and against him at 90 mph, the athlete makes minute adjustments to his position to lower the drag number.
In preparation for the 2018 Winter Olympics, Dow Chemical worked with the U.S. team to tweak the sled's bridge to allow the athlete to control it better, as compensation for the very frigid temperatures in PyeonChang, South Korea. Very cold temps make the sled materials more rigid.
Training for luge is about strength and precision, but a slider has to have a certain temperament, too. In luge, adrenaline junkies win.
"The run might only be 50 seconds long, not more than a minute, and you're absolutely knackered after the run because you're focusing mentally and physically," British luger Adam Rosen told the IOC. "You're putting your body through so much and you're doing all this while taking the bumps and steering precisely through all these curves going down. But the more you do it, the more you get used to it, [as] you're constantly navigating the sled."
More Great Links
- Agenzia Torino 2006: Bobsleigh, luge and skeleton facility – Cesana Torinese http://www.agenziatorino2006.it/eng/opere/media/u10/indext.htm
- Alberta Luge Association: Types of Luge. http://www.calcna.ab.ca/luge/luge.html
- "All About Skeleton Luge." RevoLUGEn'. http://www.revolugen.com/iceluge.htm
- Booton, Jen, "How Dow Chemical Is Prepping Team USA For Luge In PyeongChang." Sport Techie. (Feb. 13, 2018) https://www.sporttechie.com/dows-engineers-helping-team-usa-luge-pyeongchang-olympics/
- Boyle, Alan. "The high-tech race for Olympic gold." MSNBC. February 1, 2002. http://www.msnbc.com/news/693675.asp?0si=-&cp1=1
- CBC.ca: Torino 2006 - Luge. http://www.cbc.ca/olympics/sports/luge/essentials/index.shtml
- "Centrifugal Force." University of Virginia Physics. http://phun.physics.virginia.edu/topics/centrifugal.html
- Chang, Gloria. "The science of sliding." EXN.ca. February 19, 1998. http://www.exn.ca/Stories/1998/02/02/01.asp
- "Digital gear gives luge the edge." BBC News. http://news.bbc.co.uk/1/hi/sci/tech/1795747.stm
- "Everything You Need to Know About Luge." WashingtonPost.com. http://www.washingtonpost.com/wp-srv/sports/olympics/longterm/2002/howitplays/text/luge.htm#critical
- Great Britain Luge Association. http://www.gbla.org.uk/about.php
- HAE Streetluge Webcenter. http://www.skateluge.com/stluge.htm
- International Olympic Committee, "Adam Rosen's Guide to Luge at PyeongChang 2018" (Feb. 13, 2018) https://www.olympic.org/news/adam-rosen-s-guide-to-luge-at-pyeongchang-2018
- Leo, Alan. "New Olympic Clocks Go for the Gold." TechnologyReview. February 20, 2002. http://www.technologyreview.com/BioTech/wtr_12752,304,p1.html
- "Luge: How do engineering and technology play a role in the Olympics?" ReachOutMichigan.org. http://www.reachoutmichigan.org/funexperiments/agesubject/lessons/newton/luge.html
- NBC Olympics. "Luge 101" (Feb. 13, 2018) http://www.nbcolympics.com/news/luge-101-rules
- Olympic.org: Luge. http://www.olympic.org/uk/sports/programme/disciplines_uk.asp?DiscCode=LG
- Roberts, Selena. "Luge." The New York Times Online. February 5, 2002. http://www.nytimes.com/2002/02/05/olympics/05LUGE.html? ex=1137128400&en=4cca5f848bf3e077&ei=5070
- Technology Award: Olympic Bobsled and Luge Track. ASHRAE. August 2000. http://resourcecenter.ashrae.org/store/ashrae/newstore.cgi? itemid=6040&view=item&categoryid=134&categoryparent=134&page=1&loginid=4497344
- Torino 2006 - Cesana Pariol - Bobsleigh, Skeleton, Luge http://www.torino2006.org/ENG/OlympicGames/vieni_a_torino2006/cesana_pariol.html
- "US Steel Team with USA Luge Team to Build Faster Sled." AZoM. http://www.azom.com/details.asp?newsID=1572
- USALuge.org. http://www.usaluge.org/TeamInfo/aboutluge.htm
- "Winter Olympics: Luge." Infoplease. http://www.infoplease.com/spot/winter-olympics-luge.html
- "The wrong side of the tracks." BBC News. January 11, 2002. http://news.bbc.co.uk/winterolympics2002/hi/english/luge_and_skeleton/newsid_1750000/1750493.stm