Engineering at Cambridge:
Alumnus Hal Evans shows off the fully-functioning replica of a 1930s Polish cyclometer he has built.
Engineering at Cambridge:
Alumnus Hal Evans using the lathe in the Department of Engineering's main workshop.
Engineering at Cambridge:
Milling the front panel of the cyclometer replica on the XYZ milling machine in the Department of Engineering’s main workshop. The panel is made from an insulating material.
Engineering at Cambridge:
Rolling of a rotor cover. The work is carried out in one of the Department of Engineering’s workshops, located in the Dyson Centre for Engineering Design.
Engineering at Cambridge:
The underside of the cyclometer replica during its construction. The mass of silk-covered wiring can be seen on the right.
Engineering at Cambridge:
Use of modern rapid prototyping to test and refine designs.
Engineering at Cambridge:
Underside of the cyclometer replica's lampboard, displaying the cable harness. The wires are solid core and silk-insulated as used in original Enigma machines. The wires are bound together using waxed linen lacing.
Engineering at Cambridge:
During operation of the cyclometer replica, bulbs illuminate to indicate the ‘characteristic’ cycle lengths.
Engineering at Cambridge:
The front panel after it has been engraved and cleaned, and before the rheostat is fully installed. It is made from a hard, vulcanised rubber material that predates Bakelite and is now seldom used. The raw material was sourced from Germany.
Engineering at Cambridge:
The rheostat, used to control the brightness of the bulbs. Rotating the arm clockwise reduces the number of resistors engaged (located on the underside of the panel), thus increasing the brightness of the bulbs.
Engineering at Cambridge:
Soldering the wires to one of the input connector plates. The position of each wire on the plate is critical, and thus careful continuity testing was vital to ensure that the machine was wired correctly.
Engineering at Cambridge:
A view of the input connector plate which conducts electrical voltages to and from the rotor system. Note there is no stepping mechanism in the cyclometer, unlike in an Enigma machine.
Engineering at Cambridge:
Reflector ‘A’ in place in the cyclometer replica.
Engineering at Cambridge:
A set of Enigma rotors, numbered I, II and III. These are exact genuine copies, sourced from a specialist machinist in Germany.
Engineering at Cambridge:
Reflector ‘A’. This was the reflector in use until 1937, when the Germans exchanged the reflector for another, reflector ‘B’, with different internal wiring.
Engineering at Cambridge:
The reverse side of the reflector with the external metal casing removed, exposing the maze of silk-covered wiring interconnecting the brass pins.
Engineering at Cambridge:
A rotor system lever, exactly as it would have looked in an Enigma machine.
Engineering at Cambridge:
Reflector (left) and rotors (right) in situ in the cyclometer replica.
Engineering at Cambridge:
A similar view to the previous image, but with the locking lever in its closed position. This slides the reflector to the right, compressing the rotors together.
Engineering at Cambridge:
Setting the right-hand rotor system to be three steps ahead of the left. The finger wheel of each rotor is moved until the appropriate letter appears in the window.
Engineering at Cambridge:
An example output from the cyclometer replica. Here, 14 bulbs illuminate, indicating a ‘characteristic’ cycle length of 14 (more accurately, this is two cycles of length 7).
Engineering at Cambridge:
The other ‘characteristic’ cycle from the same starting settings as in the previous image: the other 12 bulbs illuminate. Note the use of the rheostat to adjust the bulb brightness.
Engineering at Cambridge:
Another example with a different rotor starting position (FJU with the right-hand system as FJX, three steps ahead. Rotor order III, II, I; reflector A). 8 bulbs illuminate.
Engineering at Cambridge:
The finished and complete cyclometer replica. Rotor lid open, displaying the Enigma rotor system inside.