TNMOC Blog V – The Turing Welchman Bombe

The Bombe just wasn’t Bombastic enough for The Imitation Game

Between the years of it’s now legendary creation in 1940 to the unveiling of the biggest secret in the British military history courtesy of F. W. Winterbotham’s The Ultra Secret (1974), Bletchley Park’s Enigma decryption machine, the Turing-Welchman Bombe was nothing more than a series of unofficial documents and hearsay.

Upon the official revelations that Alan Turing had indeed masterminded an electro-mechanical decryption device to break the German Enigma machine’s cipher, little information was available on how the machine worked, what it looked like, how it was constructed and how it sounded.

Research and Reconstruction

Following thirteen years of investigation into how the Bombe worked and what it looked by an expert group of fascinated engineers led by John Harper, a Bombe was built; using techniques and parts that mirrored that of their original construction. Unveiled as a fully working demonstration piece for use at its birthplace Bletchley Park, the Bombe reconstruction is modelled on photographs, literature, notes and genuine artefacts that pieced together a fascinating ‘mish-mash’ of a machine, developed quickly and out of necessity, using parts from existing pieces of technology such as electronic punch card sorting machines, to produce a quick and dirty solution; solving the most sophisticated cipher encryption device of its time.

Fast forward to 2015 and inside the Manor House of Bletchley Park, amongst the phenomenal carpentry of wood panelling and antique furniture, lays the latest homage to Turing and Welchmans’s Bombe, The Imitation Game ‘museum’. Following a significant period of filming at the Manor House, the film company gave Bletchley Park permission to keep many of the props used in the making of the 2014 blockbuster including the movies reimagined prop Bombe.

Mad Props

The Bombe Reconstruction, an originally crafted design of utter complexity and logical beauty sits a mere 150 metres away across the park, grease pouring from its axles onto a brushed steel metallic under-tray as it runs the same calculation task for fascinated onlookers, time and time again, always accurate; a testament to the solid design in principle. Beside it sits an earlier reconstruction… I should say ‘stage prop’. It was built, at face-value, faithfully in accordance with the original design, for use in Michael Apted’s 2001 movie Enigma. Despite featuring Hollywood starlet Kate Winslet alongside an acclaimed Dougray Scott, the film arguably lacked ‘global appeal’ and the prop today doesn’t even warrant a plaque or label to denote its origins. Nobody would know it was featured in a major movie unless you were ‘in the know’.

Meanwhile, inside the grand manor house, lies the Imitation Game’s ‘stage prop’ Bombe. It is Bombe 2.0 XL Edition. It is Bombe on steroids; bolder and more brash, but lacking the substance beneath its overtly adorned physique (It doesn’t work). As if the machine wasn’t already absurdly complicated in its original guise, Bombe 2.0 XL Edition comes with additional VU meter readers, valves, dials and other volumetric gage displays, additional cooling blocks and oh so much more of the vivid red wiring flowing over the dark metallic frame’s top and sides, wisping gracefully to the base like a Viking goddess. The mechanical display dials that cover the front panel seem almost ‘enhanced’ somehow. The colours more vivid, more Hollywood, pre-saturated to enhance the image in HD, far more striking than the original design bothers with.

It’s fascinating to see how one invention can garner so much attention. How Turing can be dubbed genius for his developments and contribution to logic theory and information systems, whilst just around the corner from Bletchley Park, the somewhat annexed National Museum of Computing, possesses another, far more impressive reconstruction of the first ever programmable electronic computer Colossus (also utilised at Bletchley Park) as designed by another maverick genius of his time, the much overlooked Tommy Flowers, sees a far fewer visitors, and a much lower level of appreciation than the Bombe.

The Imitation Game is a second stab at the major motion picture cherry for global recognition of the Enigma story but the true mystery cipher that needs decrypting is why the movie industry insists on making such a meal out of it. Is it really necessary to turbo charge the device? It’s already incredibly technical and complex to look at as it is, but along with much of the story about Alan Turing and the Bombe, it is dramatic, but not quite dramatic enough to deserve ‘movie status’, so the truth is embellished, and nobody is any the wiser.

Movie Poster for Imitation Game
Movie Poster for Imitation Game
"Bletchley Park Bombe4" by Antoine Taveneaux - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons -
“Bletchley Park Bombe4” by Antoine Taveneaux – Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons –

TNMOC Blog III – Powers Samas Obsolescence

Possibly one of the most powerful moments for me during my residency at The National Museum of Computing, Bletchley Park has been trying to record the Power Samas Punch Card Reader in full function.

The engineer who was with me was on his last day of volunteering at the museum before fully retiring had been obsessively restoring various mechanical and electro-mechanical counting machines such as the giant Powers Samas Card Reader that had previously been used by a large Chicken farm in the north of England during the 1940s.

As with so many of these now obsolete machines, there is no need or desire to maintain them with any kind of level of functionality, even just for posterity sake. This was particular machine was a unique example. Sadly when we tried to record the sound, just a few seconds into operation something broke.

This is the very last moment that anyone, anywhere is ever likely to hear the sound of the Powers Samas Model 041 Punch Card Reader in operation. It was the only known ‘working’ model in existence.

I was interviewed by Brian Anderson for the Vice/Motherboard blog where I discuss this and other activities if you would like to read more.


RCA AR-88LFI spent some time working through the process used to decrypt the cipher made by the Lorenz SZ40/42 in-line cipher machine used by The German Army in World War II. These were messages that came from the German High Command. High level stuff.

It’s a fascinating story of incredibly high level skill in logical analysis and something I couldn’t do justice describing myself. I recommend a visit to TNMOC to find out more. I’ve started off at the point of entry… The Radio Frequency transmission of wireless telegraphy.

I’ve recorded many sounds from the RCA AR-88LF at the museum, covering as many sonic aspects that I can. Here is a little teaser of a recording taken from the rear of the unit, picking up super low electromagnetic frequencies.