Velox V specialised for sprint

The Human Power Team Velox 2015 presented their design for the new recumbent bike last Thursday. The student team chose to focus on the world speed record event next September.

Frankly, it is amazing how new student teams always find ways to improve upon the work of their predecessors. The Human Power team with students from TU and Free University (VU) Amsterdam won the world speed record (133.78 km/h) with Sebastiaan Bowier in the Velox III in 2013. Last year, the Velox IV with Rik Houwers was just a little slower (132.26 km/h). Former team manager Toine Hooijen blamed the strong wind for the slightly disappointing result.

And now, they’re back. Analysis has shown that Velox’s IV aerodynamics were critical, said the team’s current PR manager Dylan Kreynen. ‘Critical’ means the aerodynamic form was vulnerable to disturbances such as transverse winds. These would perturb the flow around the hull and increase the drag.

The large air-vent opening in the front, made especially for the hour speed record, also disturbed the airflow. During the ten-minute sprint for the world speed record, a smaller air opening would do.

The team now focuses on the World Human Powered Speed Challenge on Battle Mountain in September. That allows them to make a smaller air-vent and make the aerodynamics of the hull less critical. Another adaptation is the split line, where the two parts of the cocoon are joined. Instead of a horizontal line, the team now chooses for a ‘swoof’ running from below just behind the front wheel to the top of the hull at the back. That way, it’s positioned on the transition zone from laminar to turbulent flow. Here the influence of unevenness on the airflow should be minimal.

TU master student Rik Houwers will be this year’s pilot with a year of experience under his belt. Former rower Lieske Yntema will attack the women’s speed record; set by the French speed cyclist Barbara Buatois at 121.81 km/h in 2010.

Another novelty is the dynamic feedback system that will guide the cyclists in their ten-minute build-up to the 200-metre sprint. The system monitors the athlete’s heart rate and power and the vehicle speed. Based on these data, it calculates the ideal approach, which it then displays to the cyclist. Until now, the protocol was fixed. It couldn’t deal with deviances. The dynamic feedback system, as developed by the sport scientists from VU Amsterdam, will adjust to the circumstances and advise accordingly.

“We have to improve where we can”, says Kreynen. “The field of competitors has grown in number and in professionalism.”

Follow the team’s progress on their website.

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