Tour de Speed: Designing the Ultimate Race Bike
| July 9, 2013
Inside a nondescript steel building in an industrial park just north of Charlotte, North Carolina, a cyclist leans over his handlebars, pedals as hard as he can—and stays precisely in place.
According to the complex data projected on the floor for the rider to track, his bike is going 40 kilometers an hour. But it’s doing that inside the A2 Wind Tunnel, a spinoff of a company founded primarily to test the aerodynamic efficiency of racing cars.
The engineering that takes place in this wind tunnel improves the cyclist’s efficiency by 24.1 percent. And as the Tour de France 2013 heats up, it’s just one way that this technology is being used to make huge advances in a 200-year-old invention that seems about as simple as they come.
“It’s a bike, it’s got two wheels, you pedal it. You’d think not much can change. But conventional wisdom has been challenged on that,” says Kevin Dessart, director of coaching education and athlete development at USA Cycling in Colorado Springs. “The manufacturers and the riders are always looking for the next advantage.”
The bicycle has been evolving since 1817, when the German baron Karl von Drais first built a wooden frame connecting two wheels, which the rider pushed along with his feet. It took until the 1860s for a pair of Frenchmen, Pierre Michaux and Pierre Lallement, to add pedals, which they attached to the hub of the front wheel. The Scotsman Thomas McCall moved the mechanical crank to the rear wheel in 1869.
Early bicycles were made of iron and wood with high seats and solid rubber tires, which made them particularly uncomfortable for the “bicycle jockeys” who rode them on the cobblestone streets of cities. That led to another breakthrough bit of mechanical engineering: the Bike Jockey Strap, the first jockstrap, which was invented in 1874.
The bicycle itself, meanwhile, continued to transform. The large front wheel was made smaller and the saddle was moved back. A chain drive replaced that original crank, and gearing was added. So were pneumatic tires—by another Scotsman, John Boyd Dunlop—to soften the ride, and a rear freewheel was developed to let the rider coast down hills. To help him stop, the cable-pull brake was invented.
And there things stood for decades, despite all of these impressive bursts of technological improvements, constrained largely by the limitations of steel frames.
Today, with international bicycle sales topping $61 billion a year and riders ready to confront the French Alps and the Olympic velodrome in London, engineers have returned to the challenge of improving the design of this seemingly simple machine. New materials have allowed them to reduce the weight of a road-bike frame to about two pounds, down from the 48 pounds of those cumbersome original iron-and-wood models, and shape its once-boxy form into a curvy and almost sensual work of art.
The ultimate goal, of course, is not to look good. It’s to go fast. And computer-aided design and the science of fluid dynamics are steadily increasing efficiency.
The use in bicycles of carbon fiber instead of steel and aluminum has not only reduced the weight of a bicycle frame by one third, says Jean-Luc Callahan, engineering manager for road bikes at Specialized. It also “opened a lot of doors on design—how we manufacture, and the ability to make the frame in different shapes.”
Next comes aerodynamic simulations and wind-tunnel testing. After 200 years, says Callahan—and more than a century of racing—“the industry is still in its infancy in terms of aerodynamic knowledge. There are a lot of theories out there, but even to simulate those properly requires skill, specialized software, and manpower.”
Even the minutia of bicycle design affects the aerodynamics, he says.
Tour de Speed: Designing the Ultimate Race Bike
| July 9, 2013
“The helmet is a huge percentage of your drag,” he says. That’s resulted in new styles of helmet, including egg-shaped models. Vertical shifting levers cause wind resistance, so manufacturers have incorporated shifters into the brake levers, and are developing push-button shifting. Some new bikes come with spaces for battery packs and other obtruding components in the frame or seat. Deep wheel rims extending inward toward the hubs are also meant to cut down friction, and can act like sails in a crosswind.
It takes as long as two years to design a new bike for the mass market, Callahan says. Engineers use rapid-prototype machines to build full-sized mockups.
The finished products go into a wind tunnel.
“The smallest change can make a big difference,” says USA Cycling’s Dessart. Aerobars, for instance, which let riders lean far forward, are credited with having helped cyclist Greg LeMond win the Tour de France in 1989. Since then, the space between them has been narrowed, further increasing their aerodynamic efficiency.
Competitive cyclists “are the product testers,” says Dessart, who is himself a cyclist and an Ironman triathlete. They’re the real-world R&D.”
They’re also a little different from the NASCAR drivers with whom general manager Dave Salazar usually works back in that North Carolina wind tunnel.
Sure, says Salazar, a mechanical engineer—there’s a cultural difference. But in the end, he says, “We’re all after the same goal: We’re all just trying to go faster.”
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