The wheel

18 July 2022

Mankind's greatest invention, or is it?

In doing some deeper research into MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) we noted that a number of people have developed the view the transistor (the MOSFET in particular) is the most important invention ever devised; that it has stolen the number one spot from the wheel. Poppycock, we say. Sorry, you’ll have to forgive our language. It’s just that as the Victorian Automotive Chamber of Commerce we’re pretty passionate about the wheel.

Those who suggest the transistor has deposed the wheel and assumed the number one spot point out solid state technology has made possible all modern communication, manufacturing, commerce, computing, medical equipment, entertainment and, of course, the internet. In fact, virtually all of modern civilisation.

Without the transistor, where would we be?

Actually, the above question is easy to answer. We can make an accurate determination of what the world would be like without transistors because the first one wasn’t invented until 1947 (MOSFET in 1959). Widespread commercial utilisation of the transistor didn’t occur until 10 years later when Sony released its TR-63 radio in 1957. Other models were also available around that time but the Sony model became the most popular. The point is, a world without transistors exists in living memory.

What about the wheel?

Cars, trucks, ships and aircraft all existed before the invention of the transistor, but obviously not before the wheel. Certainly, all of these things have benefited enormously from the transistor, but they weren’t invented because of the transistor. Additionally, industry, commerce, science and communication all existed before the transistor. However, as it turns out, these endeavours also existed before the wheel. So, that’s a bit of an embarrassment for our argument. However, if the wheel isn’t mankind’s most beneficial invention, what is? 

A cursory examination of history and a bit of common sense shows the one thing that precedes everything else is fire. So, it looks like the wheel is actually in the number two spot but it’s a close-run thing. It’s true fire is a discovery rather than an invention but the various methods of creating fire on demand are, collectively, an invention. Fire gave us cooked food, which is important, but when someone noticed wood can be hardened somewhat by limited exposure to fire we have the beginning of technology in general and materials science in particular. Fire also gave us metal, which is essential for useful wheels, even wooden ones. Metal was used to reinforce wooden wheels but also to create the tools needed to cut and shape wood effectively. So, no fire, no wheel. In fact, no anything.

There’s a notion the idea of the wheel was born of rolling heavy loads on logs. Maybe. However, a direct progression from this sort of transport to the wheel isn’t correct. For instance, wheels were common in Mesopotamia (modern Iraq) around 3000 BC. Over in Egypt at that time they were not used, although the Egyptians knew about them. Indeed, the Egyptians had potter’s wheels. Many believe the potter’s wheel gave birth to the idea of the wheel in general. Again, maybe, but not every civilisation that made pottery on a wheel had the idea of attaching wheels to carts, even when they’d seen their neighbours do so. There were a number of civilisations around the world that knew about the wheel but chose not to use it for transport. Why not?

Technology will only ever be adopted and developed if it’s useful. The wheel was not always useful. Early roads were just dirt tracks  formed first by foot traffic, then herds of cattle and horses. They were uneven at best, and in winter and during rain they were muddy quagmires, not to mention things like fallen trees and other obstacles. Under these conditions wheels weren’t a lot of use. In fact, they made traversal of such ground even more difficult. It made much more sense to load whatever needed to be carried on sure-footed pack animals. This worked well for loads that could be divided and distributed across as many animals as needed.

Early wooden wheels needed to be wide to reduce cutting into soft ground. Also, a wide solid wheel is stronger than a narrow solid wheel. Uneven ground requires a large diameter wheel, which increases the effect of leverage between the road contact point and the hub. A wheel made from a single cross-cut piece of a large tree trunk is laterally weak. Effectively, the whole thing is cross-grained. Again, the answer is a wider wheel but the increased strength comes with the burden of greatly increased weight. This was particularly burdensome when carts were pulled or pushed by humans, as was often the case in ancient times, and in later times and cultures, too. Engineering solutions were needed.

Wheels made from planks strapped together side by side were better for a couple of reasons. First, when there were no trees of wheel-sized girth, planks from smaller diameter trees could be used. Second, planked wheels were only cross-grained in one direction. In the other, stresses were absorbed by the longitudinal orientation of the grains. In addition to holding the planks next to each other, the transverse planks also added longitudinal grain structure across the main planks. Consequently, the ideal compromise between strength and width for the prevailing service conditions was possible. All good, but there were other problems with ancient wheels.

A larger diameter wheel applies greater bending force to an axle through the hub. This is because the distance between the ground contact point and the hub is effectively a lever. Bigger diameter wheel, longer lever. If a wheel and its hub are the same width, making a hub wide enough to resist lateral stress will again result in a heavier wheel. The solution was simply to make the hub wider than the overall width of the wheel. This allowed the hub to resist bending forces induced by lateral strains on large diameter wheels more effectively. It was another of the first engineering solutions to emergent problems from the basic form of simple wheels. All narrow rimmed, large diameter wheels commonly seen on wagons and carriages have hubs much wider than the width of the contact area of the rim. Interestingly, modern wheels have the opposite form, that is, contact patches much wider than the hubs supporting them.

The next engineering milestone in ancient wheels was reducing weight by cutting away unnecessary wood between the rim and the hub. Initially, this was done by first making a solid wood wheel and then cutting semicircular holes around it resulting in considerable weight reduction. However, it seems this would also have reduced strength in such wheels considerably by reintroducing cross-grain weakness issues at the section of the rim adjacent to the holes. Cross-bracing would probably have been the answer to this problem.

Although we haven’t seen examples of cross-bracing on wheels lightened as described above, we like the idea because it brings us, and perhaps brought ancient wheelwrights, to the notion of spokes. Spoked wheels are about as light as you can get and they allow the use of much smaller pieces of wood joined together to form rims. In most spoked wheels each section of the rim is held in place by at least two spokes. By reason of geometry each of the spokes in each section of the rim is splayed in relation to the other, which creates firmer fixing less prone to loosening. As with plank wheels, spoked wheels with segmented rims could be made from much smaller sections of wood. 

There are theories that, as land was cleared in enormous measure, the shortage of large girthed trees necessitated the development of spoked wheels. Perhaps, but we like to think it was a pure engineering development in the quest for lighter wheels for wagons and chariots. Speed and responsiveness was then, as now, everything in battle. Chariot racing also became a sport so perhaps we can think of those race chariot builders as predecessors to modern race engineers.

Of course, wheels need axles. The earliest wheels were fixed to axles and the entire assembly rotated. The problem was wagons and carts with such wheel-sets couldn’t be steered very easily because both wheels were forced to turn at the same speed. The next development was wheels that turned independently on fixed axles. The differential wheel speeds made possible by this arrangement allowed two wheeled carts to turn easily. The swivel axle had to be invented before drag-free turning was possible on four-wheeled wagons. Again, iterative engineering improvements on the path to the modern vehicle.

Wheeled wagons and carts need well maintained roads for greatest efficiency, so the wheel and purposely built and maintained roads developed roughly in unison. Metal working expertise was also developing simultaneously and eventually the Celts, it’s suggested, were the first to add an iron band to the outside of the rim. This meant larger diameter wheels with even narrower and radially thinner rims were possible. In turn, this allowed smoother passage for goods and passengers.

As we mentioned, metalcraft had also been under continued development during the history of the wheel and this culminated with gears of all sizes, flywheels and myriad mechanisms that made the industrial revolution possible. This period takes its name from the revolutionary change that occurred in industry. However, it could just as easily refer to the revolving iron and steel wheels and gears that made it all possible.

In 1808, the first wire spoked wheel was made. The first self-powered car, the Benz Patent-Motoragen, had wire spoked wheels in 1886. The first pressed and welded steel wheel was invented in 1908 and brought to market in 1910. This represents the birth of the modern automotive wheel. Cast alloy wheels appeared in the 1930s (cast centres bolted to rims) and fully cast wheels appeared in the late ’40s. So, in broad terms and excepting carbon composite wheels, like those from Carbon Revolution, the wheel had reached its final stage of development at about the same time that the first transistor was created. The rest is recent history. The transistor may own the future, but never without the wheel. The wheel owns all human history and it always will.

Words: Paul Tuzson.

To be featured in Australasian Automotive August 2022. 

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