REPLICA WEHRMACHT ENIGMA 1

Thank you Mr Nicotra for assisting me with the laser cutting and 3D printing as well as helping me to solve endless problems and pointing out problems with my ideas. Thank you Mr Gray for assisting with the laser cutting. Thank you Dad for you help, especially with the woodwork in making the box.

ROTORS

Technical Details:

The rotors are the key component in the Enigma cipher. In the Enigma 1, there are three rotors that work together. Each rotor is a substitution code that multiply to create a complex substitution. However, the substitution arrangement changes every letter, as the rotors rotate. The rotor in the right hand position does 1/26 of a rotation every letter. The second rotor does 1/26 of a rotation once for every full rotation of the 1st rotor. The third rotor does 1/26 of a rotation once for every full rotation of the 2nd rotor. The exception to this is known as 'double stepping' and occurred when the second rotor rotated on two consecutive key presses.

Each rotor comprises of 26 contact pads, arranged A-Z and 26 corresponding contact pins on the other side. Each pin is connected to a corresponding contact pad, creating the substitution. The letters are printed on a ring that rotates independently of the internal wiring. It is the rotation of the ring that is defined by the 'Ring Setting' or 'Ringstellung'. This ring setting is what determines the stepping of the rotors and a side effect of it is causing the phenomenon of double stepping. For further technical details and rotor wiring tables, read here,

Construction Details:

I used laser cut acrylic to form the components of the rotors. Modified galvanised pop rivets with springs acted as the contact pins. Pogo pins would have been better but I could not find ones with a large enough diameter to withstand the compression and rotational forces that the pins experience. M2 copper flat rivets (head dia: 4mm) were used for the contact pads and where countersunk. PVC pipe was used to form the ring that the letters are printed on. The same process is used on the reflector and in/out plate.

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LAMP BOARD

Technical Details:

The lampboad is a series of 26 lamps arranged in three rows of 9 8 9. The lamps are located under a panel of transparent material with printed letters, so that when a lamp is illuminated, the light shines through a letter shaped hole, creating an illuminated letter.

Construction Details:

I used laser cut 3mm plywood to form the structure of the lampboard. In interests of cost, I decided to use LED's instead of more tradition but less reliable lamps. The top panel was cut with 16mm holes to form the letters spaces. The letters were printed out on paper and laminated to achieve a similar look.

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KEYBOARD

Technical details:

The original Enigma keyboard used very complex mechanical switches made of many formed metal parts. Each letter, in the depressed position, connected their rotor letter to their lampboard letter. (ie. The rotor input A was connected to lamp A through switch A). In the pressed position, the switch connected the power to the rotor letter. (ie. The rotor input A was supplied with power). The plugboard just connected letters in pairs for additional encryption and did not change throughout the message.

Construction Details:

I decided to use simple contact microswitches which would enable far easier construction of the keyboard. the switches were mounted on a 3D printed base. The switches were then connected to IDC cable. There is one 26 pin IDC connector to the lampboard and one 26 pin connector the the rotors. The plugboard is decorative. (ie. It is set to have no plugboard connections).

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BOX

Technical Details:

The box was made of wood and was entirely independent of the Enigma machine. It was purely a carry case for protection over long distances. The box could be locked with a key.

Construction Details:

I chose to make the enigma rely upon the box for side walls. My enigma slides out of the box to reveal the inner working. Because my enigma is not made from metal, the rotors are compressed partly by the box itself. Therefore, the box is necessary for the function of the enigma. The box is made from Pacific Maple 12mm and is half-dovetailed at all joints. The box used a half mortise lock to secure it closed but they were too expensive so I will have a simple latch.

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