Getting Down With the Luge

CurioCity
23 January 2012

In the movie Cool Runnings (1993) John Candy's character shows some film to introduce his newly formed Jamaican team to the sport of bobsledding. He states that “in bobsledding bones don't break…they shatter.” I guess there's no good way to introduce bobsledding. This goes double for the luge.

The luge is much like the more well-known sport of bobsledding; it uses the same track and follows the same basic idea: get down the hill as quickly as possible. However, instead of being contained within the limited protection of a bobsled, lugers race down the icy track on a toboggan about the size of two skate boards. Any collision during this 150km/h ride and it's the luger's body that is bearing the impact…Yikes!

The luge, a French word meaning “racing sled”, became an Olympic sport in 1964 in Austria. During that inaugural competition one rider died during a run. But that wasn't dangerous enough; nowadays, at least one of the four runs a luger must complete must be done at night.

The genius behind John Candy's plan in Cool Runnings was his idea that using sprinters as bobsledders would give their team an advantage with the start of the run. The premise was sound, since in both the luge and bobsled events one-tenth of a second advantage at the start ends up being three-tenths of a second advantage at the end.

Unlike bobsledding, in the luge the riders do not run with the sled to start; they propel themselves while holding on to two bars and then “paddle” using spiked gloves for extra speed. After the start the following factors affect the sleds speed:

temperature wind speed weight of the rider steepness of the track friction

There are three main forces that act on a luge as it whizzes down an icy track (here's the Physics we promised!): 1) Gravity pulls the luge towards the centre of the Earth (more on this later); 2) the Normal Force is exerted by the track pushing up against the luge and acts perpendicular to the surface of the track; and 3) Friction, which always acts opposite to the direction of motion, is caused by the rubbing of the blades against the ice (see figure).

There are rules to ensure that no team gains an unfair advantage, such as the maximum combined weight of sled + rider. This prevents heavier riders from having an advantage, since lighter ones can add weight to their sleds to make up the difference.

Other rules prevent riders from tampering with their equipment; in 1968 the German women's Olympic luge team was disqualified for heating the runners of their sleds. Why would this be a cause for disqualification? If you recall your physics classes, friction is the force that slows down moving objects since it acts opposite to the direction of motion. Ice is a surface that exerts very little friction on objects to begin with (as you've probably experienced trying to walk on icy sidewalks!), and the surface of the runners/blades on a luge are made of slippery substances to reduce this friction even further. But heat, as you know, would melt the ice beneath the sled and the end result would cause: 1) even less friction, 2) a very unfair team advantage…and 3) a disqualification!

Steering the sled as it barrels down the track is a whole other story. The only way to steer is for the rider to lean from one side to the other. This might seem simple enough but as the sled travels 150km/h down the track going around 180-degree curves it is common for the rider to experience gravitational force, or G-force, of up to 4-times that of the normal force of gravity! The force is so great it often causes riders to “lose their head”; a luge term to describe when your head is pushed back with so much force it hits the ice.

The gravitational force is responsible for increasing the luge's speed, or accelerating, down the track since it is the force that pulls the luge towards the center of the earth. It is also responsible for holding the sled (and the rider!) to the wall of a banked turn.

But, the faster the rider goes, the more air resistance occurs, causing drag, which slows the luge down. Although drag would seem like a bad thing, the good part is that it puts the breaks on the gravitational force to prevent the rider from speeding out of control. The drag is also important at the end of the race; after passing through the finish line's electronic beam the rider will sit up to decelerate. Sitting up decreases velocity by reducing the rider's aerodynamics and increasing resistance (i.e., drag) until the rider is able to come to a complete stop.

As you can see, there are a lot of forces acting on the athlete and sled during (and after) a ride, all of which are needed for a successful race.

Of all the sports in the Olympics the luge may seem like the one with the least skill involved. But, most people are unaware of the subtle strategies employed to increase aerodynamics, such as pointing their toes (again, reducing air resistance) and wearing specially designed skin-tight suits. Many do not realize the danger involved; in fact, it is amongst the most dangerous sports in the Olympics next to the skeleton, in which riders go down head first instead of feet first like the luge. It also is probably one of the sexiest sports when it comes to the double competition. Two people in spandex holding on to each other for dear life; as far as spectator sports go, it doesn't get any better than that.

For more luge information check out these websites:

http://btc.montana.edu/olympics/physbio/physics/phys-intro.html http://www.luge.ca/

Tristan Carter is a journalism student at the University of Toronto at Scarborough where he plays on the basketball team. In addition to writing, he is currently seeking an internship.

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