How Luge Works

by Julia Layton

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Photo courtesy USA Luge

Introduction to How Luge Works

There are those of us who get a little nervous moving at 90 miles per hour 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 up to 90 mph (140 km/h) are a special breed. In this article, we'll learn all about Olympic luge and find out what it takes to finish first.

If you think the luge is dangerous, then you need to read the article on ice climbing and watch video from Discovery’s Fearless Planet to see what winter sports are really all about.

Lucy Hill naturbahn luge track in Negaunee, Michigan

Photo courtesy USA Luge

The 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 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) -- American slider Tony Benshoof holds the Guinness record for fastest luge speed at 86.6 mph.

Kunstbahn luge track in Turin, Italy

Photo courtesy ©2005 Torino 2006

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.

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 bobsled/luge course used in the 2002 Salt Lake City Games is 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) 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.

The 2002 Olympic luge track in Utah is 4,318 feet (1,316 meters) long and has 15 curves. The vertical drop is approximately 400 feet (120 m).

In Olympic luge, women start further down the track than men.

The luge course for the 2006 Torino Games is 4,708 feet (1,435 m) long with 19 curves and a 375-foot (114-m) vertical drop.

The course in Turin, Italy, took almost two years and 61.5 million euros (about $74 million) to build.

Reaching speeds up to 90 mph (140 kph) on the track, 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 g's 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:

When you go into a corner pulling five g-forces with your head hanging off the end of the sled, suddenly your head is five times your body weight. You've got to keep it up so you can see where you're going because, trust me, the worst feeling in the world is having your head dragging on the ice at 120 kilometres per hour.

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.

Sledding

Luge is the French word for "sled." Sleds have probably been around since about 800 A.D. in the Viking regions, and the first reference to sled racing came out of Norway in 1480. In 1964, luge became an Olympic sport at the Innsbruck Games.

The sled is designed to maximize speed while allowing for precise control by the slider.

The Equipment

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. Olympic slider Georg Hackl actually took his sled to the Porsche Engineering Group for some speed tweaks prior to the 2002 Olympics. But it's not just about design -- it's also about using the best materials. In 2004, the USA Luge Team called on US Steel to design a new type of steel for its sled runners in order to improve speed and performance.

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.

Luge helmet and racing suit

Photo courtesy ©2005 Torino 2006

• 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.

Olympic Rules

The basic rules of Olympic luge are pretty straightforward:

• Since weight is an advantage, male athletes must weigh at least 198 lbs (90 kg), and women must weigh at least 165 lbs (75 kg). This helps keep the playing field relatively even. Sliders weighing less than the minimum weight can attach extra weights to themselves to make up for the deficit.
• Singles sleds must weigh no more than 50.6 pounds (23 kg); doubles sleds cannot exceed 59.5 pounds (27 kg). Racing suits must weigh no more than 8.8 pounds (4 kg).
• Sleds cannot have any sort of mechanical brakes.
• Steels (the sled's blades -- the only part that touches the ice) cannot be heated. This would melt the ice during the run, decreasing friction between the steels and the ice to provide an unfair speed advantage. In 1968, the women's Olympic luge team from Germany was disqualified for heating the steels on their sleds.

Men's singles

Photo courtesy USA Luge

The Race

The Olympic luge competition has three divisions: Men's singles, women's singles and gender-neutral doubles. 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. Italian slider Armin Zoggeler holds the World track record for the 2006 Torino Games course: 1:44.586 for two runs, or an average time of 52.293 seconds per run.

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.

The initial push-off (top left); paddling through the start of the course (top right); lying flat on the sled (bottom left) and navigating a high-banked curve (bottom right)

Photo courtesy USA Luge

Approaching the start of the downhill, the slider lies down on the sled in a prone position. This is his body position for the remainder of the run. From this prone 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.

 

Doubles luge

Photo courtesy ©2005 Torino 2006

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.

Timing

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 -- see How GPS Receivers Work). 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.

                      Street Luge

You don't need ice to slide. Street luge uses asphalt roads for the track and a wheeled, 8-foot, skateboard-style platform for the sled.

Photo courtesy USA Luge

The Physics

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 g's 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 of the course in something like 2 seconds to achieve a really good start.

There are two people on this sled, meaning an extremely tight fit to minimize form drag.

Photo courtesy USA Luge

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 g's on a slider's body. Forces can reach up to 5 g's in banked turns, when centrifugal force* adds another dimension to the forces acting on the slider.

Photo courtesy ©2005 Torino 2006

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.

            Important Dates in Luge

• 1879: Davos, Switzerland, builds the first luge track.
• 1883: Switzerland hosts the first international sled race.
• 1935: Luge joins the International Bobsleigh and Tobogganing Federation.
• 1955: Oslo, Norway, hosts the first luge World Championships.
• 1957: The International Luge Federation (FIL) is formed to govern the sport.
• 1964: Luge becomes an Olympic sport at the Innsbruck games.
• 1979: Engineers build the first refrigerated luge track in preparation for 1980 Lake Placid Olympic Games.

A member of the USA Luge team works on his form in the Allied Aerospace Low Speed Wind Tunnel.

Photo courtesy San Diego Low Speed Wind Tunnel

The Training

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 g's 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 and camcorders, 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:

• Digital camcorders to record each run from start to finish
• Six digital cameras placed at intervals on the track
• Laptop computers
• Dartfish sports-analyzing software

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.

Training for luge is about strength and precision, but a slider has to have a certain temperament, too. In a CBC interview, Chris Moffat of the Canadian Luge Team explains, "The fastest people are the people that are out of control. It's the fact that you're not always in control that's nice." In luge, adrenaline junkies win.

Photo courtesy ©2005 Torino 2006

For more information on luge, including the 2006 Olympic schedule and venue information, check out the links on the next page.

For more common questions and expert answers on sports and athletic performance, visit Sharecare.com.

Need More Danger?

If flying through icy curves feet-first seems timid, maybe skeleton is your thing. Skeleton is a lot like luge, only the athlete navigates the course head-first and the sled weighs more. Oh, and skeleton suits may have some padding in the elbows. Skeleton racers are actually disqualified for even attempting to slow down during a run. See Olympic.org: Skeleton to learn about the sport.