It’s full speed ahead for engineers when it comes to enhancing bicycle performance. Learn how they’re building lighter and stiffer bikes, starting from Lance Armstrong’s ride:

Few people realize just how efficient bicycles are. “To put things into perspective, a car realizing the efficiency of a man on a bike at 15 mph would get around 900 mpg,” Doug Cusack, senior research and development engineer at Trek, tells Design News. But the bike’s intrinsic efficiency hasn’t stopped those at Trek, a Wisconsin-based company that’s been building bikes for more than a quarter century–and many other engineers–from continually tweaking its design.

For example, engineers are looking beyond alloy steel–which is found in most frames–and using materials such as aluminum, titanium, and carbon fiber composites to make bikes lighter, stiffer and better able to shift the peddler’s energy to the back wheel. And aside from material modifications, engineers are implementing geometry changes to enhance performance.

In fact, Trek’s use of lightweight carbon fiber has earned it a role in one of sport’s most dramatic triumphs–Lance Armstrong’s six straight wins in the Tour de France, starting in 1999. The company utilized lightweight carbon fiber in Armstrong’s bikes, improving performance while still adhering to the rules established by the UCI–a Swiss federation that oversees bicycle racing worldwide.

In particular, the company manufactures the carbon fiber frames using a patented process that keeps void content at less than half a percent, according to manufacturing engineer Scott Nielson. Since voids can result in cracks, minimizing their occurrence is key. In fact, the company’s manufacturing process produces aerospace-quality frames.

The company was also able to take advantage of the fact that carbon fiber is anisotropic–meaning its strength differs according to the direction of measurement–unlike isotropic alloys employed in frame making. As a result, engineers have to follow a particular pattern during the lay-up process to derive benefits from this trait. “Each ply goes into the mold in proper order according to a recipe,” Nielson tells Design News.

Trek is certainly not the only one in the business of improving bikes. California-based Kestrel is modifying the triangular frames for its triathlon and mountain bikes, which aren’t as rigorously regulated as road bikes. For example, its newest triathlon bike not only cuts through the air but also gathers the energy in it. According to Preston Sandusky, product and marketing director, the bike’s aerodynamic frame achieves lift in cross winds. But while this diminishes drag, it also increases instability. In response, engineers placed the frame’s center of pressure as far back as they could to exploit the sail effect without compromising handling. They did this by using a monocoque carbon frame, which allowed them to do away with the seat tube.

Indeed, engineers are putting the pedal to the metal to give bikes more oomph. And both road racers, like Lance Armstrong, and weekend warriors are benefiting.

Source:

Breaking Away
Design News, January 10, 2005
http://www.designnews.com/article/CA491475.html