Engineers Create A Strong But Lightweight Isotruss Bike Using Carbon Fibers

Engineers used elements of architecture and geometry to create a strong but lightweight triangle-based isotruss bicycle frame. To make a road bike or mountain bike, the isotruss is first wound with carbon fiber using a sheet that holds the tension constant. The engineers then hand-wind Kevlar strands over the isotruss. The process creates a bike with a large strength-to-weight ratio.

Almost every kid has at one time or another asked for one for Christmas. Now, engineers have developed what may be the most technologically advanced bike to hit the road yet. It took ten years to develop a new incredibly light and strong model that will take cyclists into the future.

Karl Vizmeg has ridden his Delta 7 Arantix bike 1,700 miles. He has raced dozens of bikes, but says a new see-through model is the strongest and lightest.

"This is phenomenal," said Vizmeg. "I've had so much fun this year, particularly with the 'wow' factor, but [also] because it's such a great racing bike."

Vizmeg's $8,500 bike was handmade in Utah using geometry and architecture. To make bikes like his, workers first make an isotruss, a form made from isosceles triangles. Then, they wind carbon fiber around the form -- creating a great strength-to-weight ratio.

"We go back afterwards and hand-wind all the little Kevlar strands, inch-by-inch, over each isotruss," said Tyler Evans, program manager at Delta 7 Sports in Payson, Utah.

They then bake the bike to bond the materials. The mountain bike frame weighs 2.6 pounds. The new Ascend road bike weighs 1.8.

"This bike rides like bikes that are much heavier and stronger and built like a tank, but it's still in the featherweight category," Evans said.

You might think the open-lattice design wouldn't be aerodynamic, but Delta 7 says wind-tunnel tests prove the bikes are as aerodynamic as traditional ones. The Ascend bike has another advantage.

"You definitely feel like a rock star, like you're famous, like you belong in the Tour de France or some high-end race," cyclist Dan Weller told Ivanhoe.

Right now, that feeling requires patience. It takes about 100 hours to build each IsoTruss bike. Delta 7 produced only 200 IsoTruss models in 2008, but is working on ways to mass-produce them in the near future. To get one right now, you have to add yourself to the waiting list and put down a $1,000 deposit.

A SEE-THROUGH BIKE FRAME? The Arantix mountain bicycle and Ascend road bicycle have frames made from carbon fiber, shaped into a form called IsoTruss. The lattice structure is woven by hand into the form of pyramid-like shapes made of isosceles triangles (the kind with two sides of equal length). The design is specially designed to make the bicycle resistant to bending and twisting, with a greater ratio of strength to weight than metal frames. This technology is currently promoted as an alternative to heavier, weaker materials in everything from automobiles to building materials and utility poles.

HOW TO WEAVE A BICYCLE: To construct the bike, the artisans take a single strand of carbon fiber and wind it back and forth (by hand) over a cylindrical mandrill until it is the right size, then wrap Kevlar around the fibers to bundle it. Then they bake it in an oven, which bonds all the carbon together.

The Materials Research Society, the American Mathematical Society and the Mathematical Association of America contributed to the information contained in the TV portion of this report. This report has also been produced thanks to a generous grant from the Camille and Henry Dreyfus Foundation, Inc.

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