March 9, 2009 Super light structural materials such as carbon fiber and Kevlar have incredible natural strength in tension but are much weaker in compression. A good example of this is how the carbon fiber suspension on a formula one car can resist several tons of downforce but explodes when crashed into a barrier. The concept of tension has been a familiar sight in large engineered structures such as suspension bridges and now the same concept has been applied to a bike frame.

We have seen the down tube on a bike frame replaced by a steel cable in the Slingshot bike, now Romanian industrial designer Ionut Predescu has come up with a concept bike frame that uses just two carbon fiber tubes and takes advantage of the tensile strength of Kevlar wire to replace all other tubes usually found in a bike frame. He calls it a Tensegrity frame, a term invented by Buckminster Fuller of Geodesic dome fame which is a portmanteau of Tensional Integrity.

The idea is similar in concept to the spokes in a wheel where it’s actually tension on the spokes that holds the wheel together, not compression. The result is a super light, high strength frame where "elements seem to float one against the other", although as the designer himself admits, there may be issues with lateral stability. A prototype will tell the tale - we'd love to see one.

Paul Evans

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