We see wheels everyday, but have you ever stopped to think about how they work?
According to ExplainThatStuff.com:
Why we need wheels
“In modern times, we assume there have to be roads for wheels to travel on. But wheels were first used on carts precisely because there were no smooth tracks to use for reliable transportation. Before carts were invented, people dragged loads on sledges and frames hauled behind animals such as horses and dogs. Sledges were an effective way to move heavy loads before wheels were invented, but friction slows them down. Frames, where a load is part dragged and part carried, help to solve this problem. The A-shaped dragging frame, known as a travois, is thought to have been invented thousands of years ago and Native Americans used it up until the 19th century. Even with animal power to help, friction between the rough ground and the frame made the going difficult.
Who invented the wheel?
“People were using animals for transportation long before the invention of the wheel and even before the development of human settlements and agriculture in the Middle East around 8,000–9,000BCE. Dogs are believed to been tamed and domesticated in China around 13,000BCE; horses were domesticated much more recently around 4500BCE. Animals used for human transportation in this way are called beasts of burden.
“No-one knows exactly when, where, or how wheels were invented. Potters wheels are believed to have been widely used around 7000 years ago in Mesopotamia (a region of the Middle East now largely occupied by Iraq): it’s easy to imagine how a potter might have hit upon the idea after repeatedly rotating a stool to work on a pot from different angles. We don’t know when the potter’s wheel was invented either, but some historians believe it may date from as far back as 8000BCE. In its early form, it was little more than a turntable or “tournette” mounted on a central support.
“Perhaps someone eventually turned a potter’s wheel through 90 degrees to make a new kind of transportation, or perhaps the wheel was completely reinvented for this new purpose, but another 1000–1500 years elapsed before wheels were first used on carts. Most likely, someone using tree trunks as rollers realized their job would be easier if the logs could somehow be fixed in place underneath the load, sliced up like salami so they would pass more easily over and around obstacles. Such an effective idea was bound to spread widely and the wheel found its way to Europe and Asia during the following millennium.
“Wheels work more effectively when they have a smooth road surface to travel on. The Romans pioneered road-building from around 300 BCE onward as a way of linking disparate parts of their empire. Roman roads were built in a similar way to modern ones from layers of different materials, including large boulders to support weight, and smaller stones, sand, and tiles to allow drainage. Often cement and concrete (another important Roman technology) were used to bind loose materials together. On top, there was a hard-wearing surface made of flattened stones cut and pieced together like a jigsaw. Roman roads were famously built in straight lines to minimize traveling time.
“Development of the wheel
“In terms of their basic science, the wheels that carry our vehicles today are virtually identical to those first used in ancient times: though built with more sophisticated materials, they are still essentially flat discs rotating on solid axles. More interesting is the way wheels have evolved in other ways in a range of increasingly complex machines.
“With the addition of teeth around their rim, wheels become gears, capable of changing the torque (rotational force) of a machine or its speed: gears enable a bicycle to go fast or climb a hill very slowly—with the rider pedaling at exactly the same rate in both cases. Extended into drums, wheels can be used as winches to raise water from wells, rocks from mines, or anchors into ships: simple machines of this kind are known as capstans and windlasses. Winches that use several wheels, linked by multiple lengths of rope, become pulleys: powerful machines that greatly magnifying pulling forces, allowing a person to lift many times their own weight.
“Wheels form the heart of turbines (machines that capture energy from a moving liquid or gas): waterwheels and windmills, civilization’s most important sources of machine power in the Middle Ages, both evolved from a basic wheel turning around an axle. Engines too rely on wheels to convert fuel into energy and drive a vehicle: in a modern car engine, for example, fuel burning in the cylinders pumps pistons back and forth, turning an off-center axle known as a crankshaft, which then powers the gearbox and the road wheels.
“In 7000 years, the wheel has gone far beyond its original use as a pottery-making tool. By helping us to move loads, harness energy, and transform forces, this simple but amazingly effective invention literally made it possible for people to conquer the world!”