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In memory of Aubrey Krüger, ocean tamer

Aubrey Krüger, the draughtsman who helped bring into existence one of the great South African inventions, the dolos, died recently in East London. This entry on him (and Eric Merrifield, who was initially given all the credit) is an extract from 50 Flippen Brilliant South Africans.

Eric Merrifield & Aubrey Krüger

Eric Merrifield: 1914 ­– 1 December 1982

Aubrey Krüger: 1935 – July 2016

Harbour engineers; inventors; ocean tamers

Sometimes in life the simple route is best. Take the mousetrap, for example. In 1894 William C Hooker, of Abingdon, Illinois, patented the first-ever spring-loaded snap-trap. It is a “spring-actuated jaw” attached to a wooden board, with a hinged trigger on one side and a locking bar on the other. Bait is placed on the trigger, the jaw is primed, and when your resident mouse comes tiptoeing along for a nibble the locking bar disengages and the jaw slams shut. Bye-bye, mousy. This simple device is so effective at what it does that in more than a century since its invention no-one has come up with a better, more efficient, more cost-effective way of catching mice. Not for nothing the phrase, “Build a better mousetrap and the world will beat a path to your door.”

In the 1960s, South Africa came up with an invention that is not only simpler than the mousetrap, but one that has a far mightier role to play around the world. It is the dolos, a giant, oddly shaped concrete construction with no moving parts whatsoever, and its job is to tame oceans. Plonk several hundred, or even several thousand, of them in a row along a harbour breakwater or a shoreline and they offer immense protection against the relentless erosive power of the sea.

The dolos takes its name from the Afrikaans term for an ox’s knucklebone because of their similarity in shape, often described as “an H with one leg turned through 90 degrees”. It is slightly more refined than that – there’s a bit of a taper in the design and there are usually eight angled surfaces, not four – but that’s pretty much it. The key to success is the way they interact with each other when packed together. Unlike rectangular breakwater blocks that aquaplane and move about in heavy running seas, dolosse scatter the energy of the waves and actually lock closer together over time. Even though they can weigh up to thirty tons, they are also easier to handle than rectangular blocks.

About the only thing complicated about the dolos is working out who invented it. For a long time the East London harbour engineer Eric Merrifield was given all the credit. Dolosse were originally known as Merrifield Blocks and he received the international Shell Design Award, among other prizes, for his efforts. But after Merrifield’s death, the unheralded Aubrey Krüger, a junior draughtsman, claimed to have come up with the prototype of the dolos, using several sections of broomstick and some string. Merrifield, so this version of the story goes, was simply the man in charge who had dished out the instructions for a new concrete structure to be designed, and then managed the invention into being. Either way, they both worked for the South African Railway & Harbour Services at the time and, since it was invented on company time, the dolos was considered its property. And it was never patented. Given that there are – from Tristan da Cunha to Hong Kong harbour and throughout more than a hundred countries in between – millions and millions of the things holding back the ocean all around the world, that was probably not the soundest financial decision ever made.

So, to Merrifield and Krüger and whoever else was involved in the creation of the dolos go great kudos and acknowledgment – but no financial fortune. Between them, they built a better ocean-restraining structure, but the world did not beat a path to their doors.


50 Brilliants cover _mini
Book details:

50 Flippen Brilliant South Africans by Alexander Parker & Tim Richman

Book homepage

EAN: 9780987043719

Buy the book here


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