Simple Tech: Wheels explained

The wheel is perhaps the one thing, fire aside, that really set humanity on the road to progress roughly 6,000 years ago. Without wheels, even the Flintstones’ car wouldn’t budge an inch without considerable wasteful effort. Simple they may appear, but they’re absolutely critical.

In vehicles, the wheel connects the axle and tyre. It must be rigid because it has to carry the weight of the vehicle and strong so it can survive bad roads and hard bumps. But you cannot make it too heavy because then it wastes power and causes other...