To celebrate the opening of our new exhibition ‘Hut 11A: The Bombe Breakthrough’, take a closer look at some of the technical drawings and blueprints for Bombe machines featured in the exhibition. These original drawings were selected from several thousand in the collections of Bletchley Park. Beautifully detailed and incredibly precise, they were all created by hand by the engineers at the British Tabulating Machine Company in Letchworth, who were tasked with building the Bombes. The drawings relate to some of the different types of Bombe machine which were developed over the course of World War Two in response to changes in design and operation of Enigma cipher machines. Together they are testament to the enormous effort that went into producing the incredibly complex Bombe codebreaking machines.
1 / 9 — Detail from Brush Holder Assembly. This whiteprint shows how each Bombe drum holds 104 spring wire brushes arranged in sets of four, with 19 wires per brush. The brushes make and break electrical contact with brass plates as the drums rotate. These wire brushes were manufactured at the Spirella factory in Letchworth as the workers there were accustomed to using wire for making corsets. This particular drum was used for testing for faults on the machine.