Engineering: quotes, facts and reflections - Page 2

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WonderArchitecture

Fujian tulou are huge round or square houses in south-east China with walls of pounded earth, built by Hakka and Minnan communities. One fortified ring could house a whole clan, sometimes several hundred people, around a shared courtyard.

Most tulou were built between the 12th and 20th centuries in the hills of south-western Fujian, where bandits and feuds between clans made a house that could be shut like a fortress worth the effort. Walls three to five storeys high were made by pounding earth between wooden boards, layer upon layer. The outside has a single gate and few windows; inside, timber galleries run round every floor. Each family had its own rooms from the ground to the top floor, while the courtyard held the well and the ancestral hall, where the clan honoured its forebears. The largest tulou could house up to 800 people. UNESCO listed 46 of them as a World Heritage Site in 2008.

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WonderEngineering

The Shushtar Historical Hydraulic System in Iran is a network of dams, bridges, tunnels, canals and mills on the Karun River, much of it built in the 3rd century CE. It watered farmland, supplied the town and drove water mills.

Tradition traces the first canals at Shushtar to the Persian king Darius the Great in the 5th century BCE, but the system's key works belong to the Sasanian Empire. The Band-e Kaisar, or Caesar's Dam, a weir about 500 metres long across the Karun, is said to have been built by Roman soldiers captured when the Sasanian king Shapur I defeated the emperor Valerian in 260 CE. It raised the river so that water could be led into canals and rock-cut tunnels, where it drove mills and fed fields before pouring down a series of falls into a basin below the town. Thirteen dams, bridges and other works operated as one system. UNESCO listed it as a World Heritage Site in 2009.

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WonderEngineering

A hypocaust was the Roman system of underfloor heating: a furnace sent hot air under a floor raised on small pillars and, in some buildings, up through hollow walls. It warmed baths and wealthy homes.

The name comes from Greek words meaning 'heated from below'. Under the floor stood rows of small brick or stone pillars, called pilae, and a furnace outside the room pushed hot air and smoke into this low space; hollow box tiles set into the walls could carry the heat upwards and out. Roman writers credited a wealthy businessman of the early 1st century BCE, Sergius Orata, with inventing heated 'hanging baths', but historians doubt he was the first to warm floors this way. The architect Vitruvius described how to build such baths late in the 1st century BCE, and the system spread across the empire, from Britain to North Africa. Keeping it going took a steady supply of fuel and enslaved workers or servants to tend the fires.

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WonderArchaeology

Nan Madol, off the island of Pohnpei in Micronesia, is a ruined city of basalt walls, tombs and ceremonial buildings on roughly a hundred artificial islets divided by tidal channels.

Islet-building began by the 8th or 9th century, and the great basalt walls went up from about 1180–1200. The site became the ceremonial and political seat of the Saudeleur dynasty, which ruled a united Pohnpei until about 1628; rival chiefs were made to live there, where they could be watched. The builders used long, naturally many-sided columns of basalt, quarried elsewhere on Pohnpei and brought to the site, stacking them in alternating crosswise and lengthwise courses around platforms filled with coral rubble. How they moved and raised such heavy stone is not recorded. The mortuary sector, Madol Powe, includes the walled royal tomb islet of Nandauwas. UNESCO listed Nan Madol in 2016 and placed it at once on its List of World Heritage in Danger, as silt and mangroves were choking the channels.

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WonderEngineering

Float glass, the flat glass in almost every modern window, is made by pouring molten glass onto a bath of molten tin. The glass spreads into an even sheet with smooth faces that need no grinding or polishing.

Before float glass, large clear sheets were made as plate glass: cast or rolled, then ground and polished on both sides, a slow and costly job. Alastair Pilkington and Kenneth Bickerstaff of Pilkington Brothers developed the new method at the firm's works in St Helens, Lancashire, between 1953 and 1957. It works because glass is lighter than tin and does not mix with it: floating on the molten metal, the glass flattens under gravity and surface tension, then cools slowly as a continuous ribbon. The company announced the process in 1959, reached profitable full-scale sales in 1960 and licensed it around the world during the 1960s, when it replaced the older methods.

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DriveEngineering

The Bessemer process, patented by Henry Bessemer in 1856, made steel by blowing air through molten iron to burn off excess carbon and other impurities. It made steel cheap enough to build railways, bridges and ships.

Bessemer's converter was a large pear-shaped vessel lined with heat-resistant brick. Air blown in from below burned away carbon, silicon and manganese, and the burning itself gave off so much heat that the iron stayed molten without any added fuel. Three to five tons could be turned into steel in 10 to 20 minutes, a job that had taken at least a full day of heating, stirring and reheating. The early process could not remove phosphorus, so it worked only with scarce phosphorus-poor ores until 1878, when Sidney Gilchrist Thomas and his cousin Percy Gilchrist introduced a converter with a basic, limestone-type lining. The price of steel fell from about £40 a ton to £6–7.

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DriveEngineering

Prestressed concrete has steel cables stretched tight inside it, so the concrete is already squeezed before any load arrives. Concrete cracks easily when pulled but is very strong when squeezed, so this lets beams and bridges span farther.

In ordinary reinforced concrete, loose steel bars carry the pulling forces, but the concrete around them still cracks as it bends. Prestressing goes further. In pre-tensioning, steel strands are stretched before the concrete is poured and released once it has hardened; in post-tensioning, cables run through ducts in hardened concrete and are then pulled tight and anchored. Either way, when traffic or weight later tries to stretch the underside of a beam, it first has to cancel that built-in squeeze. The French engineer Eugène Freyssinet patented a practical method in 1928, using high-strength steel so that the squeeze would not fade over time. From the mid-20th century prestressing became standard for bridges, car parks and floor slabs, allowing longer spans and thinner sections.

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WonderTechnology

Bakelite, invented by the chemist Leo Baekeland in 1907, was the first fully synthetic plastic. Heated in a mould, it set hard for good, and because it resisted heat and did not conduct electricity it was ideal for plugs, switches, radios and telephones.

Leo Baekeland, a Belgian-born chemist living near New York, was looking for a synthetic replacement for shellac, a natural resin made by lac insects and used to coat and insulate electrical wiring. He found a way to control the reaction between two chemicals, phenol and formaldehyde, using heat and pressure. Earlier plastics such as celluloid were made from plant cellulose; Bakelite was built entirely from laboratory chemicals. It is also a thermoset: once cured, its molecules lock into a rigid network, so it cannot be melted and reshaped. On its own the resin was brittle, so makers mixed in fillers such as wood flour. By the 1920s and 1930s it was everywhere, from telephones and radio cases to jewellery and pan handles.

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WonderEngineering

Weathering steel, often known by the trade name Cor-Ten, is an alloy that forms a tight, stable layer of rust when it is left out in the weather. That layer slows further corrosion, so the steel needs no paint.

Ordinary rust flakes off and exposes fresh metal, so corrosion keeps eating inward. Weathering steels contain small amounts of copper, chromium, nickel and phosphorus, which help the rust form a dense layer, called a patina, that sticks to the surface and keeps out much of the oxygen and moisture. Its colour darkens from orange to deep brown over a few years. US Steel introduced the alloy in 1933 for railway wagons carrying coal and ore. It only works where the surface can dry out between wettings; constant damp, sea salt or water trapped in joints defeats it. The first building to leave it bare was the John Deere headquarters in Moline, Illinois, designed by Eero Saarinen and completed in 1964.

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WonderEngineering

Wootz was a steel made in southern India and Sri Lanka by melting iron with carbon in small sealed clay pots. Traded west as ingots, it was prized because careful forging brought out flowing, watery bands in the blade, the pattern of famed Damascus swords.

Crucible steel of this kind was made in southern India from around the middle of the first millennium BCE. Because the metal melted fully in a sealed pot, it took up carbon evenly, giving a hard, high-carbon steel. In Sri Lanka, the archaeologist Gill Juleff found ancient furnaces built on hillsides to catch the monsoon winds, which blew air through them instead of bellows. Ingots travelled to Persia and Syria, where smiths forged them into the blades Europeans called Damascus steel. The wavy bands are sheets of tiny carbides, hard compounds of iron and carbon. In the 1990s J. D. Verhoeven and Alfred Pendray showed that traces of vanadium in the ore, together with repeated heating during forging, are needed for the pattern to form.

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WonderEngineering

A Fresnel lens replaces the thick curved glass of an ordinary lens with thin concentric rings, each shaped to bend light at the right angle. Invented for lighthouses in the 1820s, it focuses light just as strongly with far less glass and weight.

In 1819 the French physicist Augustin-Jean Fresnel, working for France's lighthouse commission, proposed a stepped lens to replace the metal reflectors then in use, which returned only about half of a lamp's light. A full-size lens was tested in Paris in 1822, and on 25 July 1823 the first lighthouse Fresnel lens was lit at Cordouan, at the mouth of the Gironde; its light could be seen more than 32 kilometres out to sea. A solid lens of the same power would have been impossibly thick and heavy. Later improved with glass prisms that also sent stray light towards the horizon, the design spread to lighthouses around the world, and it has been called the invention that saved a million ships.

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WonderEngineering

Near the top of Taipei 101 hangs a 660-tonne steel sphere that swings against the tower's sway in strong wind, so people inside feel much less movement. Engineers call this device a tuned mass damper.

Taipei 101, a 508-metre skyscraper in Taiwan's capital, opened in 2004. Its gold-painted sphere is 5.5 metres across and hangs from the 92nd down to the 88th floor, where visitors can see it. The ball is tuned to the tower's own natural rhythm of swaying but moves out of step with it, so each push of the wind is partly cancelled, while hydraulic dampers turn the motion into heat. It can reduce the building's movement by up to 40 per cent. During Typhoon Soudelor in August 2015 the ball swung a record one metre. Smaller tuned dampers steady bridges, chimneys and power lines; London's Millennium Bridge was fitted with them after it wobbled under crowds when it opened in 2000.

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DriveEngineering

Some buildings in earthquake zones do not sit directly on their foundations but on flexible bearings made of rubber and steel. When the ground shakes, the bearings take up most of the movement and the building above sways far more gently. Engineers call this seismic base isolation.

A conventional building is tied rigidly to the ground, so it takes on almost every jolt. In an isolated building, bearings separate the structure from its foundation. They are usually stacked layers of rubber and steel, often with a lead core that soaks up energy; the lead-rubber bearing was invented in New Zealand by Bill Robinson in 1974. Because the building shifts slowly on its bearings, upper floors feel much weaker shaking and equipment inside is more likely to keep working. The building needs a gap around it so that it can move, and its pipes and cables need flexible joints. San Francisco City Hall, Wellington's Te Papa museum and, in Istanbul, the Sabiha Gökçen Airport terminal and Başakşehir Çam and Sakura City Hospital all stand on isolators.

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WonderDesign

Cut an A4 sheet in half across its length and you get two A5 sheets with exactly the same proportions. This works because the international paper standard ISO 216 sets the sides in a ratio of 1 to the square root of 2, about 1 to 1.414.

The idea is old. The German scientist Georg Christoph Lichtenberg pointed out the advantages of the square-root-of-two ratio in a letter in 1786, and revolutionary France listed similar formats in a tax law of 1798. The modern system came from the German engineer Walter Porstmann, whose proposal became the German standard DIN 476 in the early 1920s and later the international standard ISO 216. The largest size, A0, has an area of one square metre; A1 is half of it, A2 half again, and so on down to A4 and beyond. Because every size has the same shape, a page can be enlarged or reduced on a photocopier without cropping. The main countries that still mostly use other sizes, such as Letter, are the United States and Canada.

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WonderDesign

The Anglepoise desk lamp, designed in 1932 by the British engineer George Carwardine, stays at whatever angle you set it. Springs balance the weight of its jointed arms, so the shade moves with a light touch and then holds still.

Carwardine was a car designer and consultant who specialised in vehicle suspension, so he knew how springs could hold a load steady. He worked out a balance of springs and arms that let a lamp keep its position at almost any angle, and applied for a patent in July 1932. In 1934 he licensed the design to Herbert Terry and Sons, a spring maker in Redditch, and their four-spring model 1227, released in 1935 for use at home, proved very popular. In 1937 a Norwegian company, Luxo, began making its own version. A Luxo lamp later starred in Pixar's first short film, Luxo Jr. (1986), which is why a desk lamp still hops across the studio's logo.

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WonderDesign

Thonet's No. 14, launched in 1859, is the classic bentwood café chair. It was built from six pieces of steam-bent beech, ten screws and two nuts, with a cane seat, so it could be mass-produced, shipped in pieces and assembled where it was sold.

Michael Thonet, a German-born cabinetmaker who settled in Vienna, spent years learning to bend solid wood with steam into strong curves that could be repeated exactly. That removed most of the carving and joints that made chairs slow to build, and let his company, Gebrüder Thonet, make identical parts in large numbers in factories in Moravia, in today's Czech Republic. The chair was cheap, light and tough enough for busy cafés, and Thonet's firm sold about 50 million of them between 1859 and 1930, making it the best-selling chair of its time. Because the parts could be packed tightly, chairs travelled by rail and ship to customers around the world. Versions of it are still made today.

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DriveDesign

A plug that fits only one way cannot be put in wrongly. Designing products and processes so that mistakes are impossible, or noticed at once, is called poka-yoke, Japanese for “mistake-proofing”.

The Japanese engineer Shigeo Shingo, who advised Toyota, developed the idea in the 1960s. In one factory, workers assembling a small switch sometimes forgot to fit one of its two springs. Shingo had them first put both springs in a small dish, then fit them from the dish; if a spring was left over, the mistake was obvious at once. He first called the method baka-yoke, “fool-proofing”, but changed it to poka-yoke, from poka, an inadvertent mistake, and yokeru, to avoid, because the old word seemed insulting to workers. Everyday examples include a memory card that goes in only one way and a microwave that stops when its door opens. Shingo argued that preventing a defect costs far less than finding it later.

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WonderDesign

Cat's eyes, the small reflectors set into the middle of many roads, were invented by Percy Shaw of Halifax, England, and patented in 1934. They send headlight beams back towards the driver, and when a wheel rolls over them a rubber wiper cleans the glass.

Shaw said he had found his way home on dark nights by the shine of tram rails; once they were removed, he needed something else to follow. The name comes from the way a cat's eyes glow in headlights. Each stud holds glass lenses in a rubber dome set in a cast-iron base. A passing wheel pushes the dome down, a fixed rubber wiper cleans the lenses as they sink, and rainwater collecting in the base helps rinse them. Shaw set up his company in Halifax in 1935. During the Second World War blackouts, when street lights were off and headlights were partly covered, their value became obvious, and after the war a Ministry of Transport committee backed their use across Britain's roads. Similar studs are now used around the world.

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WonderTechnology

In the 1790s Claude Chappe built a chain of towers across France whose movable wooden arms signalled coded messages. Operators watched the neighbouring tower through a telescope and copied each signal, so one symbol could cross the 230 kilometres between Paris and Lille in about nine minutes.

Chappe worked on the system with his brothers, and in 1792 the revolutionary government asked him to build the first line, between Paris and Lille. In 1794 it brought news that French troops had taken the town of Condé-sur-l'Escaut from the Austrians to Paris less than an hour after it happened. A beam and two smaller arms on top of each tower could form many different positions, standing for letters, numbers or entries in a codebook, and the operators copied them without knowing what they meant. The word “telegraph”, Greek for “far writer”, was coined for the system by the French statesman Miot de Mélito. At its height the network had 556 stations covering about 4,800 kilometres. Darkness and fog stopped it, and in 1846 France decided to replace it with the electric telegraph.

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WonderEngineering

The Plimsoll line, a circle with a line through it painted on a ship's hull, marks how deep a loaded ship may safely sit in the water. Extra lines beside it allow for fresh water, tropical water and winter seas, where the safe limit is different.

The mark is named after Samuel Plimsoll, a British member of parliament who campaigned in the 1870s against “coffin ships”: vessels sent to sea overloaded and often over-insured, so that owners could profit even if the ship sank and its crew drowned. His 1873 book Our Seamen stirred public anger, and the Merchant Shipping Act of 1876 made the load-line mark compulsory on British ships. International conventions in 1930 and 1966 extended load lines to ships worldwide. The letters beside the mark stand for tropical fresh water (TF), fresh water (F), tropical (T), summer (S), winter (W) and winter North Atlantic (WNA). Canvas plimsoll shoes are said to take their name from the band where the upper meets the sole, which recalls the line.

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WonderTrade

On the Pacific island of Yap, large limestone discs with a hole in the centre, called rai, have long served as valuables in important exchanges. Some are taller than a person, so ownership changes without moving them: everyone knows who owns each stone.

The stones were quarried mainly on Palau, hundreds of kilometres away, and brought back by canoe and raft on dangerous voyages. A stone's value depends on its size and workmanship, but above all on its history: who fetched it, and whether lives were lost bringing it home. The largest surviving stone is 3.6 metres across and weighs about four tonnes. In the 1870s the Irish-American trader David O'Keefe helped bring stones to Yap on his ship in return for dried coconut and sea cucumbers. An old account tells of a rai that sank during transport yet kept changing hands, since everyone agreed it was still there. The economist Milton Friedman compared this to gold that stays in a bank vault while its ownership changes. Rai are still exchanged in traditional ways today.

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WonderScience

The Struve Geodetic Arc is a 2,820-kilometre chain of survey points running from Norway to the Black Sea. Between 1816 and 1855, surveyors used it to measure a long north-south line across the globe and work out the size and shape of the Earth.

The survey was led by Friedrich Georg Wilhelm Struve, a German-born astronomer who directed the observatory at Dorpat, now Tartu in Estonia, where the chain's first point still stands. It used triangulation: surveyors measured a base line very precisely, then worked out every further distance by measuring the angles between distant hilltops and towers. The finished chain has 258 main triangles and 265 station points, from Hammerfest in Norway to a point near the Black Sea in Ukraine. When it was built it crossed only three states, Norway, Sweden and the Russian Empire; today it crosses ten. The results, published in 1858, put the Earth's flattening at the poles at about 1 part in 294, close to today's figure of 1 in 298. In 2005 UNESCO listed 34 of the station points as a World Heritage Site.

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WonderScience

The Great Trigonometrical Survey of India, begun in 1802, found that a Himalayan summit called Peak XV, later named Mount Everest, was the highest mountain then known. Surveyors worked this out by measuring angles from stations on the plains, far from the peak.

The survey was begun by William Lambton, an officer of the East India Company, and took until 1871 to finish; its maps served British rule as well as science. In 1852 the mathematician Radhanath Sikdar, chief 'computer' (the job title for staff who did the calculations) in the survey's Calcutta office, combined six observations of Peak XV and found it to be the highest summit known, at exactly 29,000 feet (8,839 metres). According to the usual account, the surveyor general, Andrew Waugh, added two feet so that the figure would not look like a rounded guess, and announced 29,002 feet in 1856. Waugh proposed naming the peak after his predecessor, George Everest, although Tibetans already called it Chomolungma. Its official height today is 8,848.86 metres.

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DriveBiography

Mary Jackson became NASA's first Black woman engineer in 1958. To qualify, she had to petition the City of Hampton, Virginia, for permission to attend evening classes held at a school for white students only.

Jackson joined the West Area Computing unit at NACA's Langley laboratory in 1951, as a 'human computer' doing calculations by hand. In 1953 she went to work for the engineer Kazimierz Czarnecki in the Supersonic Pressure Tunnel, a wind tunnel that blasted models with air at almost twice the speed of sound, and he urged her to train as an engineer. The courses she needed were run by the University of Virginia at Hampton High School, which was for white students only, so she asked the city for permission and won it. She wrote or co-wrote 12 technical papers, many on the thin layer of air flowing next to an aircraft's surface. In 1979, having reached the most senior engineering title open to her, she took a demotion to run programmes helping women and minorities advance at NASA. NASA named its Washington headquarters after her in 2020.

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