Alan Turing's World War II codebreaking Bombe is best invention, says Institution of Mechanical Engineers

By Culture24 Reporter | 06 October 2014

Engineers vote the Bombe codebreaking machine their top invention

A photo of a complicated computing machine full of colourful switches and wires
© Courtesy IME
Alan Turing’s Bombe, an electromechanical masterpiece instrumental in cracking the German Enigma code during World War II, has pipped Concorde in an expert vote to decide the best of the best engineering innovations ever made.

Built in the Hertfordshire town of Letchworth by the British Tabulating Machine Company - a group loosely linked to IBM - all of the 210 Bombes built were dismantled after playing a vital part in the war.

But a fully-functioning replica, tailored to Turing’s original blueprints during a 13-year mission by retired engineers and supporters, was completed in 2007 to the joy of heritage enthusiasts.

A photo of a complicated computing machine full of colourful switches and wires
© Courtesy IME
A mathematical genius who was perhaps only afforded the widespread admiration he deserved during a programme of events marking what would have been his 100th birthday, in 2012, Turing built the Bombe with Gordon Welchman.

The pair passed their design and construction concept to Harold Keen, an engineer at the Tabulating Machine Company. Soon the machines were decoding 5,000 messages every day.

“The Bombe machine industrialised the process of breaking Enigma,” said Iain Standen, of the Bletchley Park Trust, whose Buckinghamshire house, where the Codebreakers carried out their heroics, now hosts the rebuilt version.

“It enabled the World War II Codebreakers to decipher high volumes of messages at speed and while still relevant.”

Known to some as the Turing-Welchman Bombe, the intricacies of the machine were little-understood before the recreation was made.

“We were very fortunate to talk some of the veterans – gentlemen who’d either work on or maintained these machines,” said John Harper, who led the team behind the project.

“They gave us all the clues as to how the machine fitted together, how it worked.

“Unfortunately most of them have passed on now. We were very fortunate to get that information.

“We were also very fortunate because DCHQ sent back here a whole set of engineering drawings made by the factory.

“We had to redraw these drawings in such a way that we could manufacture the machine on paper, if you like, by putting all these individual drawings together and making complete assemblies.”

The “very keen” modern engineering team created a machine with a comparable reliability to the original Bombe – an achievement Harper called “very satisfying”.

“There were so many people at the time who knew little about the machine but knew a lot about the actual war effort. They became very keen to see how the technology worked.

“The main thing is it’s a tribute to all those who have worked on this machine – operating, developing, manufacturing, maintaining. We’ve never had much problem with getting support when we needed it.”

“These machines, which each weighed about a ton, illustrate the genius of Turing and Welchman, but also the vision and ingenuity of Keen, who made these concepts a reality,” said John Wood, the Chairman of the Institution of Mechanical Engineers’ Heritage Committee, whose members voted the Bombe the finest winner of all their 100 Engineering Heritage Awards issued since 1984.

“Estimates suggest that they could have helped cut the war by as much as two years – saving countless lives.

“The award was presented to the replica Bombe in 2009 on behalf of Turing, Welchman and Keen and also in recognition of the fantastic work of enthusiasts who rebuilt the Bombe with such care and passion.”

The Bombe received 19 percent of a vote open to 105,000 people.

It edged out Concorde by two percent, while the Rolls Royce RB211 came third with 11 percent, fractionally beating the Mallard locomotive into fourth.

The 100th award will be presented at the Old Furnace at Ironbridge this week, coinciding with the 30th anniversary of the scheme.

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