Riding the Wind

From cyclists to race cars, the motion of an object is determined by the sum of the forces acting on it. Those forces have both strength and direction and they can be observed and measured to predict future motion. Watch how an aeronautics engineer works with Newton's three Laws of Motion to test the best posture and helmet for a cyclist in a wind tunnel.

MOORESVILLE - In the sport of racing, whether the athlete is running, cycling, skating or even driving, the phrase “every second counts” means a lot. That’s because one second, or even a tenth of a second, can mean the difference between winning the race or coming in second.

It turns out there’s a facility in Mooresville, NC that combines the latest research in aerodynamics, fit analysis and physiology to help athletes shave those tenths of a second off of their times. It’s called the A2 Wind Tunnel.

“You’re always trying to balance out the best aero-position and the best position for putting out power,” says Dave Salazar, the manager of the A2 Wind Tunnel. “You’re trying to match the two to get the best combination you can get.”

Sitting behind a bank of computers, Salazar helps cyclists ride like the wind, by riding the wind inside the tunnel.

The tunnel itself is located in a non-descript metal-framed, industrial looking building. A similar looking but larger building next door houses a larger tunnel used to test NASCAR vehicles. A2 focuses on bicycles and small vehicles.

The wind tunnel has five giant fans at one end that can pull wind through the 45-foot long tunnel at speeds of up to 85 miles per hour. Most people think those fans blow wind through the tunnel. In reality, wind is pulled through, because it flows much more evenly.

The tunnel boasts HD cameras - high-speed video cameras and motion capture technology, all tucked into indentations along the walls. A2 is the only facility in the world in the world that combines all of that technology with aerodynamic sensors. That means biomechanic and aerodynamic data can be gathered in real time, while the test in happening. So if a cyclist changes positions, or headgear, or alters anything during a test, the effects can be studied immediately.
Mike Byrd is a competitive cyclist who races across the state. He came to the tunnel for an evaluation to see what improvements he could make.

"And that just gives me a chance to see what I can do better, how can I get faster, make adjustments, take advantage of free speed,” Byrd says as he puts his gear on. His bike is already locked into the testing platform inside the tunnel. “How big a difference does it make if I wear an aero helmet versus a road helmet? It quantifies everything, you can actually see the numbers and it makes it real.”

And here’s why those numbers matter:

Cycling is good exercise because a rider has to overcome a lot of forces trying to keep the bicycle from moving. That’s why pedaling is work. Those forces include gravity, which is pulling the bike and rider down, as well as drag from air resistance that is pushing from the front. There’s also vertical ground reaction, caused by friction between the tire and the ground. And there’s propulsive and rolling resistance, which is created by braking and inertia or simply getting the bicycle moving.

And that’s just going straight ahead. Go around a corner and there are even more forces working against the drider, such as added friction on the wheel, along with torque and centrifugal forces.

Now here’s the bad news.

The laws of physics dictate that most of those forces that affect a cyclist really can’t be changed. Gravity is gravity, unless moving to another planet is in your future, there isn’t anything that can be changed there. There are different tires and bike designs that can reduce the friction with the road, but by only a fraction.

Fortunately for cyclists, aerodynamic drag is the largest force a rider has to overcome to get moving... And it’s the one force a rider can do something about.

“Eighty to 90% of the power they are putting out is just to overcome air resistance, so if we can help them overcome three, four, or five percent, it’s huge for them especially over long distances,” adds Salazar, as he checks to make sure Byrd is secured on his bike and give him the go ahead to warm up. “Racers are already putting out so much power, so whatever can be saved either helps them finish the race quicker or helps them to save power in one part of the race and be able to use that power in another area.”

Salazar then leaves the tunnel, locks the door, and after settling behind a bank of monitors and computers, sounds the safety horns before turning on the fans.

The test lasted about one hour, with Mike starting and stopping peddling to put on different helmets, and assume different riding positions on the bike. There were 12 combinations tested. The cameras and sensors captured every move. 

The biggest change was noticed between position one, in which Mike wore a road helmet and sat in a more upright position, and postion nine, in which he tried an aerodynamic helmet in a tucked position that lowered his torso, by three degrees.

The difference was very clear on the computer screen, as the positions were compared to each other.

“Looking at this image here, we’re looking at angles, but also his position, and I overlaid this from his baseline position,” says Salazar, clicking the mouse to bring up each image. “You can see how much we’ve brought down not only his head, but his back. That reduces the drag, which means more efficient peddling and a huge savings of energy and power.”

Mike maintains a fairly constant racing speed of 28mph. With a three percent drag savings, the computers calculate a savings of 44 watts of power. That would translate to cutting 57 seconds off of a race time in a ten-mile race.

Mike was stunned.

“That’s big time. Especially if you’re a triathlete, you’ll be able to run a lot faster, and further, during a race saving that 40 watts,” Mike added, shaking his head and repeating the time over and over. “Fifty-seven seconds. That’s a minute, that’s a lot of time when you’re racing.”

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