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Carbon fiber seat post provides greater cycling comfort

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October 21, 2009

More rider comfort at 30 percent less weight thanks to the CFRP-based spring-loaded seat p...

More rider comfort at 30 percent less weight thanks to the CFRP-based spring-loaded seat post (Photo: Fraunhofer)

Carbon fiber composite materials (CFRP’s – or carbon fiber reinforced plastics) permeate society in many objects we now take for granted. Vehicles, airplanes and protective equipment all benefit from the material’s light weight and strength. Recently, bicycles have been taking advantage of CFRP technology where reducing weight can mean the difference between winning and losing – even a tiny reduction can be a big deal when Olympic gold medals are at stake. Fraunhofer researchers in Germany will present a spring-loaded bicycle seat post made of CFRP’s at the Composites Europe trade show in Stuttgart on October 27-29. However, for some cyclists, winning isn't everything. It's comfort that comes in at number one.

Professional and recreational cyclists know only too well the discomfort of riding over curbstone edges, potholes, streetcar tracks and cobblestones. Spring-loaded seat posts have been able to help absorb the worst shocks and make the ride more comfortable for the cyclist’s back, but for greater ride comfort, cheap off-the-shelf solutions don’t exist.

Fraunhofer researchers have just developed a functionally-integrated bicycle seat post from CFRPs that they say is ultra light and extraordinarily effective.

“A hardtail mountain bike with this new kind of CFRP seat post rides as if it were a full suspension bike,” says triathlon world champion Daniel Unger after a test drive. No surprise that in September, the component earned the Eurobike Award at the Eurobike 2009 trade show in Friedrichshafen and in Stuttgart, the high-tech post has been nominated for the 2009 AVK Award for Innovation.

The new seat post was designed at the Fraunhofer-Institute for Chemical Technology ICT in Pfinztal as part of Fraunhofer's innovation cluster known as “KITe hyLITE – Technologies for Hybrid Lightweight Construction”.

“The impetus for this came from our colleague and bicycle enthusiast, Sergei Belaew,” says group manager Oliver Geiger. “The component is based on two CFRP profiles that work like laminated springs. In this respect, the spring rigidity was calibrated to keep the deflection within the 10-10mm range. That tangibly augments rider comfort.”

Fraunhofer says the unique characteristics of carbon fiber composites are combined with a keenly intelligent construction approach and clever design that delivers noticeable added cushioning and resilience.

The deflection of the CFRP profiles influences the motion of the seat tip, and under ideal conditions actively supports pedaling. In addition, the post alleviates peak loads, even around minor superficial bumps – tar spots, damaged street surfaces and manhole covers are barely noticeable. “More ride comfort at 30 percent less weight,” says Geiger.

The outer radii of the profiles are designed to fit existing bike frames. Therefore, it is hoped that the CFRP seat post will provide high-end comfort at a low-end price tag if and when larger scale production commences.

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