What's cold, weighs 300 pounds, has 10 legs (possibly broken),
and reaches top speeds of 50 to 70 kilometers per hour before
grinding to a halt, overturning, or colliding with an obstacle?
If you guessed "A concrete toboggan," you're right. If you
said, "There is no such thing as a concrete toboggan," you are
mistaken. In fact, dozens of concrete toboggans and more than a
hundred intrepid tobogganauts compete each year in Canada's
annual Great Northern Concrete Toboggan Race, a unique test of
the athletes' imagination, technical skill, and raw
courage.
On the slope (top), most toboggans
attempt to brake and steer with simple rear-mounted lever
brakes. Results are mixed: A team from McGill University
executes an unplanned maneuver (bottom).
Inspired by the concrete-canoe races sponsored by the American
Society of Civil Engineers, the concrete-toboggan race attracts
a very special breed of north-country engineering students. The
basic principle is simple: Whoever slides fastest, wins. There
are a few rules, however. The sleds must have a concrete
sliding surface, weigh no more than 300 pounds, carry a crew of
five, be equipped with a steel roll cage, and have — or
attempt to have — brakes. No horn is required, but it
might be a good option for when the brakes are less than fully
function-
al: In 2003, says the Web site of the Carleton University
toboggan team, "Our brake failed both times and we almost took
out the cooking tent and everyone else by narrowly missing the
propane tank."
Carleton's sled teams have a colorful history: Their first
entry in 1995 finished a disappointing 32nd out of 33 entrants,
but Carleton took second and sixth place with its two 1996
teams, Crash and Burn. Carleton's current team, the
Stonecutters, buoyed by a strong technical presentation, took
top honors overall at this year's event, held at Canada's
Olympic Park in Calgary, Alberta. The Waterloo University
Pirates had the fastest piece of concrete among official
entries, clocking in at 74 kph (approximately 45 mph), but the
noncompeting Mixed Nuts from host University of Calgary topped
that, hitting 78 kph in a demo performance. McMaster
University's team, the Rigid Members, ranked first for spirit
despite relatively slow times on the hill.
But what does all this have to do with concrete, a material not
usually prized for its velocity? Maria Guglielmino, who
captained McGill's 2004 team, says it's a challenge to adapt
concrete to this unconventional use. "We need a mix that is
strong and lightweight, and also we want something that is
smooth enough to slide on the snow," she told JLC. "What we've
done for the last few years is put a carbon fiber grid in it,
because it's good in bending moment resistance. And it's also
good with impact loads, which is basically what you're going to
be hitting going down that slope."