Humble Inventions #2: Wheel

 Next up in the small inventions that make a huge difference, Roma Agrawal talks of the wheel in Nuts and Bolts. This may take you aback – what is there to write a chapter about the wheel? Don’t we even have the saying “Don’t reinvent the wheel”, which suggests that the wheel was perfected ages back?

 

Historical records suggest that the wheel was not invented for transportation. No, the wheel was invented for pottery! Why pottery? To create vessels to store food and water. What? As humans began to settle into agriculture and thus larger colonies, people found themselves further and further away from the fields or rivers, hence the need to store and carry food and water increased.

 

It was only after humans had domesticated animals and thus had something to pull a vehicle with that the “vessel-maker” wheel was transformed into a “destination-maker” wheel, writes Agrawal. But the early wheel had many drawbacks – cut from logs, they were heavy; they were uneven in shape; and not all parts of the wooden wheel were identical (since tree trunks are not uniform). Thus, spoked wheels evolved. They were much lighter allowing for faster vehicles. But spoked wheels were made of many different parts and brought new problems with them, including falling apart and breaking.

 

Once our knowledge and capabilities with metals evolved, a “flat metal hoop” was added to the outside of the wheel’s rim, giving it strength and uniformity. In the 1800’s, as humans started to try and build machines that could fly, aerodynamic aspects apart, they also needed to create a wheel strong enough to withstand the forces of landing (The spokes couldn’t withstand the enormous forces of landing). George Cayley came up with the idea of stretching thin wires between hub and rim – it made the wheel lighter (very important for flying machines), and also transferred the energy of landing impact without snapping and breaking. The wire wheel had just been invented. 

As with so many things, an idea for flying machines (wire wheel) found its first great application in something else altogether – the bicycle:

“Bicycles brought a huge change to the everyday lives of people.”

Don’t see why? The bicycle was light, cheap, and could be pedalled oneself (no need for horses and bullocks). Suddenly, compared to walking, anyone could move farther and faster, with minimal effort. It was the world’s first mass transportation vehicle.

 

I found all this fascinating, but Agrawal wasn’t done with the wheel. She looks at the wheel with her mechanical engineer lens. Gears are wheels, she reminds us. Wheels with “teeth”, but wheels nonetheless.

And gears are a game changer of colossal proportions. Because they can do 3 things:

“Change the direction of rotation, change the speed of rotation, and change the force acting at the rim of the gear.”

The applications of gears range from cars and trucks to the (mechanical) wrist-watch.

 

If you allow not just the wheel but also its axle to rotate (well ok, also add a few elements around it), she tells us, you get a gyroscope.

What makes the gyroscope useful is its peculiar property of maintaining its spinning orientation even when external forces act on it. The applications of this are not immediately obvious, so she gives examples all of us understand. Remember those fighter jets that spin and turn crazily? How do you think the pilot knows his orientation? If you pointed to that instrument on his dashboard with the artificial horizon line on it, well sure, but how does that instrument know the orientation? Via the gyroscope which, remember, maintains its orientation no matter what forces act on it, including those violent turns of the fighter jet and, yes, gravity. If you felt that fighter jets are too niche an application, well, how about satellites in space? They too rely on gyroscopes to know their orientation. And those satellites are how your GPS works, so all of us use the wheel in its gyroscope avatar, albeit indirectly.

 

A fascinating chapter on the oh-so-many uses of the humble wheel.

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