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- The typical weekend bicycle rider might think nothing of what goes into his or her casual purchase. But for the professionals of the cycling world, it's serious business involving complex design processes and custom engineered materials.Trek Bikes
of Waterloo, Wis., operates under tremendous pressure to get the job done using the best available technology for Lance Armstrong as he seeks a seventh consecutive victory in his final Tour de France.
While the average consumer bike costs a few hundred dollars, the higher-end professional models made by Trek, such as the SSLX, retail in the $8,000-$10,000 range, according to Trek public relations director Zapata Espinoza.
The standards of professional cycling mandate that the total bike weight, including the frame as well as other components, be a minimum of 6.8 kg. Armstrong prefers a frame weighing less than one kilogram, as compared to the average consumer frame of five pounds, according to Trek lead designer Michael Sagan.
"The two things that Lance says over and over again are `light' and `stiff'," said Espinoza. "Light and stiff, that's all he cares about. He wants a frame that's light and he wants one that's stiff for peddling."
Consumer bikes are usually built with steel or aluminum frames. High-end bikes tend to be made from lightweight carbon fibers to lower the weight while still retaining hardness and maneuverability. The company makes the material using a molding process called optimum compaction low-void, which removes air pockets within the material to both lower the volume and guarantee stiffness.
The grade of the material is measured in grams per square mater. Most of Armstrong's team use bikes made 110 GSM or 120 GSM fiber, while Armstrong himself is using the newest design, which uses a blend of different materials including the newest 55 GSM fiber.
Computer modeling supplements wind tunnels
The best materials, though, don't mean much unless the design is precise. One of the newer advances in design has come in the form of computer design. Not only can designers quickly make blueprints of bikes to experiment with different concepts, they can virtually test them, too.
"It's quite costly to make trips down to a real low-speed wind tunnel," Sagan explained, noting the best such facilities are all the way in California and Texas. "So what we do is have the software that can take our digital prototypes and we can analyze drag characteristics of frames and wheels and fork systems inside the computer."
Instead of just building prototype after prototype and testing them all at wind tunnels, programmers are able to build virtual bikes in CAD programs like SolidWorks
and then run tests through CFDesign
, a computational fluid dynamics program that simulates the flow of air in virtual wind tunnels.
The process is also helped along by top-of-the-line workstations. Damon Rinard, a Trek R&D engineer, credited the company's HP 9300 workstations, powered by AMD Opteron processors, with cutting the computation time in half over the previous models used.
After the initial design process is complete, perhaps three prototypes are built to confirm the results of the computer simulation, as opposed to the many prototypes that were built before.
According to Rinard, this offers some distinct advantages over wind tunnels in addition to the savings in time and effort saved over physical prototypes. Whereas a wind tunnel involves video-taping and analyzing the flow of smoke around the bike, the computer program is able to precisely map out every aspect of airflow for increased scrutiny, even down to the puff of air coming up from the back of wheels.
With the increasing precision of computer modeling and its contributions to efficiency, could CFD programs one day supplant the wind tunnel entirely?
"There's a feeling that the wind tunnel is the gold standard among a lot of people," Rinard said, noting some continued skepticism to CFD in and of itself. "It's not precise. It's a numerical simulation, which is an approximation of reality. However, there is an argument that CFD might be more realistic in some cases than the wind tunnel, because the wind tunnel itself is a simulation of the open road."
One concrete example of a drawback of the wind tunnel is that the bike must be held in place by a set of vertical struts, which can present their own variables in the airflow. In a CFD simulation, the virtual bike simply stands alone in the imaginary wind tunnel, held in place by programming fiat.
Nevertheless, Rinard said the wind tunnel will continue to be seen as the proving ground of choice for most professionals for many years to come, though CFD-modeling will offer its own advantages that are not to be discounted.
As the popularity of the Tour increases, bike designers are under increasing pressure to continually innovate and improve their products for each new race. In the end, they have to put every bit of knowledge and creativity they have into turning out the best possible bikes.
"It's not like a toaster where it spits out a piece of toast after a set period of time," said Sagan. "And so it takes a bit of expertise, it takes a bit of intuition, and it takes a bit of science, and it takes a bit of engineering."