Reinventing the Wheel

bob zee sent in this link about reinventing the wheel, err, tweel, err, whatever. Wheels are an interesting challenge in engineering design: they need to be hard to be durable, soft for a smooth ride, grippy to grab the road, but smooth to reduce rolling resistance, flexible to absorb shocks, yet stiff to reduce heat build-up, and so on. Rubber tires are a relatively recent invention.