http://www.popsci.com/technology/article/2013-04/transportation-cardboard-bike: One day in 2009, Israeli engineer Izhar Gafni sat in a quiet library designing a machine to extract seeds from pomegranates when his mind drifted to cycling, his favorite pastime. Gafni admired bikes made from sustainable bamboo, but their high cost seemed prohibitive. He wondered, Why not make them from cardboard, instead? Over the next two years, Gafni learned to fold cardboard sheets into the strongest possible shapes; his experimentation led to robust structures resembling honeycombs and bird nests. He then spent another year crafting the material into bicycle components. "I almost felt like the Wright Brothers going into unknown territory," he says. The product of his labor is a single-speed bicycle with spokes, rims, and a frame made from cardboard. Varnish protects the glued paper core from moisture, while old car tires serve as puncture-proof wheels. Gafni used a car's timing belt as a chain and formed plastic bottles into pedal cranks. The 28-pound prototype, called Alfa, can safely support a rider nearly 20 times its weight.