Simplified Enigma Replica

This is my attempt to build as accurate as possible Enigma machine using today's simplest tools and for little as possible.

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I've been researching and designing an Enigma encryption machine that I can afford to build. I started with the drawings most enthusiasts have found on the web. As incomplete as they are they were a great starting point. Those drawings and the various photo from Enigma rebuilds and on auction sites for machines being sold, have allowed me to design what I think is a very good approximation that should look very much like real Enigma. It is still a mechanical/electrical machine because i happen to think that that is much cooler than an electronic simulator.

To date I have what I think is a working design, that can be mostly 3D printed with a few parts that will be machined (mostly custom standoffs). The design has been done in FreeCAD.

I also think that my attempt is the most complete version to be found on the web, including rotors, reflector, keyboard, switches, lamp and patch panels, power switch, full case and wooden carrying box with latch and lid stays.

Just some more details about how the Enigma is designed.

You can find the FreeCAD files and STEP files on GrabCAD.

While researching the Enigma it became quite apparent that the machine went through multiple design revisions. Not just the obvious 3 to 4 rotor versions, but also various changes that were mostly likely caused by material shortages during the war. Also there were changes made to make use easier. As a result of the variations available I decided to try to keep the look and feel of the Enigma while using inexpensive parts and simple manufacturing methods, i.e. 3D printing and limited CNC routing/milling.

 For the switches I decided to use inexpensive micro switches with custom lever arms. This arrangement allowed me to use consistent keyboard key shafts. You might also notice that I decided to use black resin 3D printed key tops and fill the letter cut outs with white Miliput epoxy putty. They will look very similar to the key tops found on a lot of the Submarine Enigmas, and be a lot easy to manufacture than the brass key tops with letter inserts and glass lenses.

The original Enigma machines used spring board style switches and different key shaft spring arrangement for each row of keys.

Also I decided to use hex stock for the key shafts to eliminate a lot of parts used for anti rotation. The hex shafts will also allow for easy drilling cross holes for travel stops and spring/switch triggers. Using 3D printing it makes it easy to create the hex holes in both the switch stop plate and the switch cover plate.

For the Lamp panel I designed a circuit board to use E10 sockets to accept the bulbs and make all the common connections much simpler.

Also I plan on using E10 LED bulbs as they should be able to be more than bright enough, run cooler, have a longer life and still be short enough to easily replace the original flat top (squished) incandescent bulbs.

The next major simplification is the patch panel, and the banana jacks and plugs. After exhaustive searching I have found hardware for 2mm and 4mm banana jacks and sockets that can be made to work.

The shorting bar for the patch panel will be a pcboard with a guide block and nylon screws that feed down the barrel of the banana jacks. I will be tapping a piece of brass tubing that will act as the guide and nut for the 2mm banana jack.

The next major piece has to be the Rotors. The first generation rotors were beautiful and complex, so....

I designed the rotor to mimic the rotors used towards the end of the war, very similar to the ones seen in the recovered Submarine 4 rotor Enigmas. As the rotors were all backwards compatible I feel very comfortable they will look good.

My design "just happens" to be much simpler with fewer parts than the early versions of the rotors.

Using 2 pcboards in the design makes it very simple to do the wiring. The input contacts are high current Pogo pins that are very similar in size to the originals. The input pins are soldered to the input pcboard and cross connected with individual wires that can be wired as the various rotors were wired. The input pcboard connects to the output pcboard with smaller Pogo pins. The output contacts are 2.5mm brass standoffs that soldered to the output pcboard and sanded flush to the output contact plate.


For the reflector I have elected to use the programmable "D" style, as it could be used on the 4 rotor Submarine Enigmas in place of the 4th rotor and the thin reflector. The "D" reflector even has the D on the case to be visible in the 4th rotor's window. Using the "D" reflector in a three rotor Enigma essentially make's it the equivalent of the 4 rotor variation.

I designed the reflector to use a pcboard to connect the high current Pogo pins to the 3mm banana jacks, eliminating a bunch of parts from the original design.

The base, rotor supports and detent assembly were redesigned to make 3D printing easier and stronger while still...

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  • Sanding

    wooddragon4803/13/2022 at 23:48 0 comments

    So while I'm waiting on parts for my next stab on the rotor output contacts, I took a stab at the tooling that I will need to sand the output contacts flush to the output contact plate.

    The idea is to use a sheet of glass with sand paper glued to it and use the rig to keep the contact plate parallel to the surface of the glass. The three corner screws can be used to  adjust the parallelism. The shaft that the contact plate is mounted to will be free to float up and down in drill bushing pressed into the plastic frame. The spring between the pressure knob and the frame will allow the frame to keep the contact plate parallel to the glass when just pushing down on the knob and moving it around on the sand paper. I think it will work.

  • Let's Try That Again

    wooddragon4803/12/2022 at 17:42 0 comments

    I've often heard that no plan survives meeting the enemy, well some times a design doesn't survive meeting the hardware. This week I was attempting to put together an output contact plate for the rotors and discovered that the M2.5 standoffs that I was going to cut down for the contacts had the female holes drilled so deep that there wasn't enough material left after cutting them down to get a flat face. Now I could jut get some longer standoffs, but in looking at the physical parts I've come to the conclusion that the 4.67mm hex body on the standoff doesn't leave enough material in the contact plate to make me comfortable. This is an area that I was concerned about when I designed the part. I'm also not happy with the amount of waste I would generate if I use longer standoffs. So I decided to look at the design again. My first thought was to switch to using M2 standoffs, and to turn the standoff around so that the male threads would be the part being cut off. A M2 screw would then be used to hold the standoff in place and provide the electrical connection from contact to circuit board.

    But unfortunately that will not leave a very bit target for the next rotors input pins.

    So what I'm looking at using custom contacts that are made from 4mm brass rod.

    Now comes the problem of how to manufacture all the contacts without braking the bank. My solution is a custom 3D printed tool.

    The cutter is made from a piece of 1/4" high speed tool steel that will be ground to the required profile. The brass rod will be chucked in a drill to spin it, and I will just squeeze the cutter parts together by hand. The resulting parts should separate from each other easily.

    The tool is not complicated, nor is the profile that I will have to grind into the tool steel. So as soon as I can get my hands on the required 4mm bearings and some 4mm brass rod I will give it a go.

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Dylan wrote 11/12/2023 at 07:34 point


You have done a amazing job. Thanks for putting the design up for others.  Not to take away from it, just so you are aware. Here are some others doing something similar. If you wanted to compare.

The main one being R.D.E Enigma from hDM university in Germany. They have STL files available and manual for printing and putting it together. I'm currently in the process of printing their design. It's still in beta but probably will be made available for all soon.

Another one is here.


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