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November 22, 2017

Dolos

The humble dolos : From South Africa to the world, with love

The dolos, or dolosse (plural) was first designed & manufactured in East London, South Africa.  A common sight in South Africa for decades, they are catching on everywhere as the world tackles the symptoms of climate change.

The dolos is a concrete armour unit designed to protect breakwater areas.  They are cheap to build, easy to manoeuvre, & simple to install. as they can just be dumped on site in no particular order.

Dolos South African Invention

Dolos originate from  East London, Eastern Cape, South Africa

A breakwater that was built 1873-76, then extended in 1935 & completed in 1939 using 33 ton rectangular blocks was breached during an extreme storm in 1944.  Urgent rebuilding was required, but the work would be expensive & difficult using solutions available at the time.  Something had to be done.  A different kind of armour block was needed.

After considering options, it was decided that an armour block needed to be designed from scratch.  Conventional ones would have been costly due to patents & other issues.  Rocks of the right size were hard to find & even harder to transport.

The dolos was designed, produced & used in South Africa.  By the of 1965, there were around 450 of them in East London.  Their popularity grew due to their brilliant simplicity.  They have proved to be effective in the stormiest of conditions.  Due to their shape, even when battered by big waves, they move into each other & lock together where other armour either shifts or breaks.

What is a dolos, exactly?

Dolosse (they often hangout in gangs…) have a steel frame, & are made using concrete in moulds.

Why are they so cheap?

The authorities self manufactured them, thus saving contract surcharges. There was further saving in that they used less concrete than other armour, & were cheaper to transport.

Who designed the dolos?

The dolos design was never patented, & Merrifield has long been credited for the design.  Aubrey Kruger claimed, in the 1990s, that he made the first wooden model on which the dolos was based, after Merrifield told him the criteria (cost/mass/transport) that the new armour had to meet. It is likely that there was collaboration between the two men regarding the dolos, but it’s  Eric Mowbray Merrifield who won awards from Shell (for design) & the Associated Science & Technology Society SA.   Lack of patent means no legal right was ever claimed.

Where did the name come from?

The origin of the name is uncertain, but popular opinion is that they are named after Jacks – the game played with spiked brightly coloured  plastic shapes that resemble the dolos.  These toys are also called knucklebones, & the game has been played for many years, dating back to ancient Egypt when children used sheep bones & a wooden bowl instead of a ball.

True Story

Transnet National Ports Authority used around 26500 dolosse in building the Port of Ngqura near Port Elizabeth.  Ngqura became active in 2009, & was built to ease congestion at South Africa’s other ports.

Last word

The dolos has spread all over the world.  Global warming & strange weather patterns have caused havoc, & the humble dolos is being used to solve problems in places as far away as the  Oswego harbor in New York.  A modified version is being used in India, & I have a feeling we are going to be seeing a lot more of them, regardless of where we are in the world.

 

African Pool Cleaners Next

Sources:

Ecomomic Value of a New Breakwater Armour , E M Merrifield and J A Zwamborn                                                                                                               Image Durban Dolosse is Public Domain

© Donna Clarke –  Article first appeared in www.greatwhitetribe.com 11/14/2015

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