Sport science propels U.S. into medal
A freshly engineered bobsled design
makes the U.S. Olympic team a force to be reckoned with
by Laurie Peach, Associate Editor
four-man bobsled careens 90 mph down the 1,700-meter
long spiral track located in the foothills of Mt. Iizuna,
Japan. The track drops 113 meters from start to finish.
The driver deftly pulls the ropes left, then right to
steer through the 15 sharp curves. As the sled speeds
across the finish line, the brakeman expertly pulls
the lever, praying that their time was within that 1/100
of a second needed to take the lead.
All crew members except the driver crouch
down, reducing air resistance. They tilt their
heads about five degrees helping to turn corners.
Nicknamed 'Spiral,' the 1,700 track in Nagano
has 15 curves.
For the first time in almost 50 years, the U.S. bobsled
team is in contention for an Olympic medal, thanks to
the Bo-Dyn sled, a new design by Bob Cuneo, president
of Chassis Dynamics. With an infusion of $200,000 of
personal funds, NASCAR racer Geoff Bodine sparked the
project that led to the U.S.-built machine, now racing
in Nagano, Japan. "Prior to this, we were using
old European sleds that we had to weld back together,"
says Tim Conrad, principal engineer of the U.S. Olympic
Sport Science Technology Division in Colorado Springs.
The Bo-Dyn, originally introduced at the Lillihammer
Olympics in 1994, has undergone major revisions in the
last four years. "There were many factors we didn't
understand then that we do now," says Cuneo. "We
realized we hadn't taken into account the ergonomics
of the athletes' bodies. So we redesigned the frame
and cowling (the body) because the way the athlete rides
in the sled has a large effect on the performance of
the sled both aerodynamically and mechanically."
To develop a more aerodynamic design, Cuneo viewed both
the athletes and sled as a single unit. "These
weren't two separate items--they were one and the same,"
The key engineering issue was control. "There
are two elements of control--actual control and perceived
control," says Cuneo. It is actual control when
the car or sled does what the driver wants it to do
at a specific speed. It is perceived control when the
driver feels that he has dominion over the machine and,
as a result, will take more chances. Cuneo sees a definite
gain in racing performance when perception is increased.
A bobsled's speed is affected by three factors: the
start (push), weight, and ice friction. To increase
confidence in the sled, the athlete has to "feel"
the track. In other words, there must be communication
between the ice's surface and driver's body, "and
it has to be friendly," says Cuneo.
Much of this communication is transferred through the
sled's runners. "Runner technology really is a
black art," says Cuneo. "Many athletes will
have 20 or 30 sets of runners per sled depending on
conditions." Ice surface, sun or clouds, humidity,
and temperature--even changes of a degree or two--will
affect the speed of a race. Each set of runners is designed
with a slightly different curvature, cross sectional
radius, or chemical composition that corresponds to
the situation. Although no one yet exactly understands
why a particular shape or metal works differently under
varying conditions, Chassis Dynamics is "trying
to turn the black art into science," says Cuneo.
Another aspect of the ice-to-driver relationship is
sled stiffness. Because of the tight constraints set
by the International Bobsled Federation, there are few
components one can alter to improve the design, says
Conrad. Olympic rules confine the construction of sled
bodies to carbon fiber, Kevlar, or fiberglass. Only
steel can be used for the chassis and runners. By altering
the thickness and composite of the various materials
on the cowling, stiffness of the machine can be refined.
The thickness of the frame, shell, and runners all
contribute to the rigidity of the sled, says Conrad.
Because one can't build the frame stiff enough, body
hardness has to be added, while maintaining flex in
the machine. If the body is too stiff, the bobsled bounces
all over the track. If too soft, it is uncontrollable.
Chassis Dynamics worked with Ken Armstrong of Creative
Instrumentation (Davidson, NC) to develop an elaborate
testing package that helped determine the optimum design.
The system monitors articulation, front axle swivel
angle, rotation of runner shoes on axle, the lateral
G's on the machine, speed, acceleration, as well as
vibration on all parts of the sled. Any motion-control
technology was fair game--computer simulations, gyros,
accelerometers, and IR lasers, were all included in
the test program. The sled was originally designed using
CADKEY, a CAD software package from Baystate Technologies
"Last year we were the hottest team on the circuit,"
says Cuneo. "We've won more metals in the last
five years with the new design than we've won in the
past 50 years combined."
It began in America
"Bobsledding is the only Olympic winter sport
that we can claim is totally American," says Christopher
Lindsay, National Director of Youth Bobsled Programs
(Lake Placid, NY). Lindsay spent the last three years
researching the sport's precise beginnings.
The practical use of bobsleds in the U.S. dates to
1839, when loggers used them to haul wood. "Bob"
means "to shorten," says Lindsay.
Competitive bobsledding originated in Albany, NY, in
1886 when the loggers came to the city to sell the wood.
In an attempt to show off for the ladies, the men rode
the empty sleds through the streets. This event caught
the imagination of locals. One businessman, Stephen
Whitney, designed a two-section sled. A board, approximately
244 cm wide and 366 cm long, was connected to the rear
section with a round bolt. A thick wooden rod running
crossways through the front portion extended 20 cm on
either side to form the steering handles.
Built of solid oak with tempered iron-clad blades,
the original sleds weighed between 500 and 700 lbs empty.
Fifteen to 20 men and women added more than a ton of
weight to the 30-ft-long sled. An engineer at the time
calculated the projectile force of such a machine, traveling
at 40 mph, to be sufficient to carry the sled through
a two-foot brick wall.
At the sport's pinnacle, 20,000 people gathered in
Albany to watch the competition. The killing of a 14-year-old
boy by a runaway sled in 1889 put a stop to the sport.
Competitive bobsledding continued in Davos, Switzerland,
where Stephen Whitney introduced his sled after the
New York tragedy.
Volunteers wanted. In order to bring the sport to a
new generation, Lindsay is developing a "build-your-own
bobsled" education program for junior high and
high school students. Mechanical engineers are needed
to design blueprints that will be used to build a sled
from scratch. If constructed to Olympic regulations,
the children will be invited to Lake Placid to run their
sled on the Olympic training track. Not only will the
children learn about the sport, says Lindsay, they will
acquire mechanical engineering skills and master physics
laws, vectors, and G-forces while having fun.
Thin-wall bumper fascias save cost,
its 1998 LH platform cars, Chrysler wanted a redesign
that would differentiate the Dodge Intrepid from the
Chrysler Concorde. One component that set the Intrepid
apart from its "kissing cousin" is its bumper
Integral to the new look is a new material developed
by Solvay Engineered Polymers (formerly D&S Plastics
International), Auburn Hills, MI. The material, SEQUELr
1440 engineered polyolefin, was specifically designed
to reduce wall thicknesses in applications intended
for thermoplastic olefins (TPOs).
The 1998 Intrepid program includes three fascia tools:
two front fascias--one for the base model and one for
the ES upgrade--and a rear fascia common to both models.
The rear fascia and the base-level front fascia are
fully painted, as are dark-color versions of the ES
front. Four light colors of the ES front, however, are
partially painted, with a blackout panel of bare substrate
between the fog lamps.
Choosing the SEQUEL 1440 polyolefin over a conventional
TPO, or a competing RIM process, enabled Chrysler to
cut costs in several areas. Although all-new in design,
the 1998 front fascias are about the same size as their
1997 counterparts molded in a TPO. However, the new
fascia assemblies weigh six lbs less than the previous
iteration, with most of the weight loss attributed to
the thin-wall fascia skin. Victor Liu, engineering manager
at the molder--the Plydex division of Magna's Decomma
Exterior Systems--estimates the savings to Chrysler
over a run of 200,000 parts at more the $1 million.
The rear fascia is "the largest fascia anybody
in our company makes," notes Bob Stewart, supervisor
of exterior systems for Chrysler's large-platforms.
Still, it is much lighter. It also uses less material
than had it been molded with a 3.5 mm wall section typical
for traditional TPOs. In fact, wall thickness on the
rear fascia has shrunk to 2.9 mm, while the nominal
thickness for the front fascias now measures a slim
"With the higher flex