Everyone loves a good mystery. This is probably why Stonehenge has captivated people’s imaginations for so long. Built and altered by pre-historic civilizations over hundreds of years, the myths and theories surrounding Stonehenge have grown far larger than the stones themselves.
However, as Vivian will explain, anything is possible when people set their minds to a common goal. And as John will TRY to explain, alien intervention isn’t off the table either…
In engineering, every bit of progress is important — especially when it’s fraught with difficulties. The Kansai International Airport in Kyoto, Japan is the first airport to be built on reclaimed land and the people involved discovered that building on clay is not always as easy as you hope. However, thanks to some clever considerations, they were able to make space for one of the busiest international airports in the world.
Join us as Vivian explains the innovations, frustrations, compromises, and triumphs of creating new land where before was only water.
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Here’s one that turned out to be more interesting than John expected. Building a road seems like a pretty easy task, right? But imagine having to do it without proper equipment! Can you think of how to make it work? John sure couldn’t. But long ago in Ancient Rome, a clever proto-engineer figured it out using the power of triangles — and by just lining people up (seriously).
Join us as John learns that trigonometry does, in fact, have real-world uses.
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iTunes: https://podcasts.apple.com/…/measured-in-metric/id1465660121
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Additional Technical Background:
Shout out to one of the papers that I used to learn about Roman surveying methods, titled “Designing Roman Roads” by Hugh E. H. Davies.
This first image shows one of the methods they might have used to approximate the distance and bearing of a straight line between two points. This is an example of a basic problem where you might want to dig a tunnel through a mountain (from point D to point B). To do so, you would pace out distances in right angles, getting closer and closer to the other side, then adding up the distances or calculating the hypotenuse to get the total picture of what point D to B looks like. To use the above example, you could get the distance and bearing from P to D by going from P to Q, then D to Q, and finding the hypotenuse. By pacing out the right angles, you can lay out an approximate grid around the mountain that lets you measure the shape of the mountain and then calculate the distances you’d need between points.
Survey lines could be laid out using this exact method, as shown in the second image. Once you have a survey line across two high points, you could also identify features (like a river) based on the survey line. This lets you draw a fairly accurate map of the area you’re trying to build across.
Finally, using multiple survey lines and a rough map of the terrain and area, you could lay out your proposed road alignment. The road alignment can then be relayed back to the survey staff by linking it to the survey lines. To do this, draw lines perpendicular to the survey line to the key points along the road alignment. This way, you can tell the survey staff “go 10 paces along the survey line, then turn 90 degrees and walk 20 paces, that will be one point of the road.” Connect all the points and you’ve got your proposed road laid out on the site!
Get ready for a gross one. Believe it or not, the concept of safely transporting and disposing of waste is relatively recent; prior to the innovations discussed in this episode, people would just sort of get it as far away as they could and hope for the best. Needless to say that large cities like London became olfactory affronts on a hot day… Thankfully a brave engineer dared to dream of a better-smelling future, and braved endless political feuds and construction headaches to make it happen!
Join us as we discuss bad smells, good engineers, stubborn leaders, cholera, and the thrilling world of sewage treatment!
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iTunes: https://podcasts.apple.com/…/measured-in-metric/id1465660121
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Additional Technical Background:
So I did do some math to validate Bazalgette’s sewer using the Manning Equation for uniform open channel flow. Although the sewer was an enclosed pipe and not open channel, this applies because the sewer is not designed to flow as pressured, which means it flows as more or less an open channel.
In metric: V = (1.00/n)(Rh2/3)(S1/2)
where n = roughness coefficient, Rh = hydraulic radius (cross-sectional area / wetted perimeter), and S = slope.
Roughness coefficient for brick & mortar is 0.015.
Looking at some photographs of construction of the sewer, I estimated the sewer to be at least 1.8m in diameter, which equals 0.9m in radius.
A = 3.14 * 0.9^2
A = 2.54 m^2
Wetted perimeter = 2*pi*r = 2*3.14*0.9 = 5.65m
Rh = 2.54 m^2 / 5.65m = 0.45m
Slope was as mentioned in the podcast, 2 ft / mile which equals to 0.00038 m/m
Put it all together.
V = (1.00/0.015)(0.452/3)( 0.000381/2)
V = 0.76 m/s
(Yes, I know I said 0.77 m/s in the podcast. This is just rounding discrepancy. In case you haven’t noticed so far, us civil engineers aren’t super concerned with decimal places and absolute values.)
Remember that this is compared to a rule of thumb that pipes should be designed to have minimum flow of 0.5 to 0.6 m/s, and this formula I used wasn’t developed until 1890, some 25 years after Bazalgette’s sewers were built!
In this, the very FIRST EPISODE of Measured in Metric, we explore the Panama Canal. Many still regard this project as one of the most impressive feats of engineering in the modern world, but its complicated legacy covers issues of worker’s rights, colonialism, economic ethics, national sovereignty, and environmentalism. We also get to talk about trains for a little bit, which is Vivian’s jam.
Join us as we celebrate the defeats, the triumphs, and the reckonings associated with a world marvel centuries in the making!
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iTunes: https://podcasts.apple.com/…/measured-in-metric/id1465660121
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Additional Background:
Here’s a great graphic from a January 22, 1921 publishing of Scientific American that shows just how much travelling distance is shortened by the Panama Canal. Notice how New York to San Francisco was shortened by more than half!
Remember that the Canal was completed in 1914, so by the 1920s, people were still just marveling at the ingenuity and benefits that the Canal is providing. Notably in a 1925 edition of the The Military Engineer where a front page column celebrates the monumental achievement of the Canal and ends with “We are doing more than an engineering job with our dredges and dams. We are building and reshap-ing the industrial life of the nation. On a tiresome overtime evening at the office, it is worth while to remember this.” Indeed, next time you find yourself staring late into the night at a CAD drawing, remember the Panama Canal!
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Welcome to Measured in Metric, a bi-weekly podcast about engineering marvels and the people who built them. We often take for granted the tremendous infrastructure that fuels our daily lives. But regardless of whether we fully appreciate it, engineers have contributed to virtually every aspect of our societies.
Vivian Yu is a professional civil engineer working in Toronto, Ontario, Canada and John Julius is her husband. He is also emphatically NOT an engineer. Join us as he tries to understand how things work and why it matters.
