Aerodynamics of the edco Aerosport Rim

edco rim shapes

Dispersive Effect Termination

In 2010, Paul Lew developed an aerodynamically efficient airfoil rim shape which created an airflow characteristic he named Dispersive Effect Termination. His rim shape challenged the trend of the large-radius spoke face, and deep-V rims. Large-radius spoke face rims test well in the wind tunnel where they produce high-lift in wind conditions of 40 kph and higher. Athletes rarely compete in such high-wind conditions. The best-known high-wind course is the “Queen-K”, Kona, Hawaii, where wind conditions gust to 30 kph, so 40 kph or higher is reserved only for the wind tunnel. Lew knew there was a flaw in the traditional wind tunnel testing.

In the spring of 2016 Lew went to work in the new edco-Faster Wind Tunnel and he realized that there is a better way to test, and a faster wheel system design for real-world conditions. Lew identified a common misunderstanding about wind-tunnel testing and airflow that lead to a better way to wind-tunnel test, and a better way to design an aerodynamic wheel system. Lew shared his ideas with edco CEO Rob van Hoek who tested Lew’s rim profile for himself, and after one ride he was convinced of the benefits of Lew’s design.

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Real World Wind Tunnel Testing

The common misunderstanding is that if a cyclist can maintain a constant speed of 40 kph in the real-world, then the wind tunnel wind velocity should be 40 kph. In fact, the wind tunnel wind velocity should be 40 kph only at zero degrees yaw to simulate a real-world velocity of 40 kph. If the yaw angle changes to 5 or 10 degrees yaw, the wind velocity should be slower than 40 kph, although the rotational wheel velocity should remain at 40 kph. In essence, the higher the yaw angle, the lower the wind tunnel wind velocity. At 90 degrees yaw in the real-world, the wind effectively creates no resistance to the cyclists’ forward progress. Therefore, in the wind tunnel, in theory, testing at 90 degrees yaw the wind velocity would be 0 kph.

What Lew learned is that while the large-radius spoke face rims produce high-lift at wind velocities of 40 or 50 kph in the wind tunnel, they do not perform well in the wind velocity range of the real-world. Lew’s new design was a better solution for real-world performance, and the AeroSport was born.

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"What I really love about the wheels is their stiffness and how they respond in cross winds. Previously before using edco, I found that I was very unstable on the front end because the wind would hit me and it would just shake me around, whereas with these wheels, when I go into a head wind or side wind, it's not making me move, I can just lean in and stay steady. It's very important because when you are wiggling all over the road, you are losing energy and your watts aren't going to be consistent."

- Leanda Cave, 4 Time World Champion

Designed to Generate More Forward Thrust

The shape of AeroSport is highly efficient in real-world wind velocities, and generates thrust in the same way a boat generates forward thrust from a high-efficiency airfoil sail. Because of the efficient low-drag airfoil shape, like an efficient boat sail, AeroSport wheels can generate forward thrust more efficiently in real-world wind conditions than other rim shapes.

Enhanced Stability in Cross Winds

In higher cross-winds AeroSport performance is enhanced by their inherent stability. Cyclists who compete with deep-section carbon wheels are familiar with the “cross-wind shift”. This is the phenomenon where the wheel typically steers into the wind at low wind angles, and then “shifts” to steer away from the wind at higher wind angles. The cross-wind shift is unpredictable and dangerous, and can often destabilize a cyclist, causing a competitive cyclist to brake to slow down and regain control of the bicycle. The idea of using an aerodynamic wheel to enhance speed, but having to slow down to control the wheel is unacceptable.