Enigma Measurements

One of the first things you need if you decide you want to 3D model anything is relatively accurate measurements. If you want to 3D model something with gears, interlocking parts, that functions – you need very specific measurements.

So a few years ago, when I started Enigma research, I found the site Enigma-Replica.com. They sell and document a few reproduced parts as well as document one owner’s restoration process. However, it turns out that if you’re restoring an Enigma, you don’t need measurements: you just need parts. I kept scouring for a while, and eventually ordered the “Expanded Education Package” from Enigma-Replica.com. I received a few spiral bound notebooks with a few printouts from a CAD package, but no dimensions. And as I started trying to model something like the rotor, I realized the dimensions provided by Enigma-Replica.com were woefully incomplete. Searching the internet more and more led me to one of my new axioms of Enigma research:

Finding Enigma material on the internet is like stepping back to Geocities webpages from the early 2000s.

So I sat stuck for a while. Meanwhile, I had seen a few Enigmas in museums. I wondered if I could get my hands on one.

Through a few weird quirks, it turns out that I have worked with and do work with a great deal of people that work at a DOD agency that happens to have a museum dedicated to cryptography. I asked if anyone that’s worked there in the past knows someone in the museum and was told that the museum folks are pretty rad, and I should just call and ask if I can come measure the Enigma. From the NSA’s exhibit listing for the Enigma:

This exhibit showcases possibly the most well-known of all cipher machines – German Enigma. It became the workhorse of the German military services, used to encrypt tens of thousands of tactical messages throughout World War II. The number of mathematical permutations for every keystroke is astronomical. Allied forces were able to read most of the Enigma encrypted messages throughout most of the war as a result of the tireless effort of many Allied cryptologists. It is an electromechanical machine that used a combination of wired rotors and plugs to change each letter as it is typed. Today, many historians believe that the Allies’ ability to read the Enigma-enciphered messages and act on that information shortened the war by as many as two years, saving thousands of Allied and Axis lives.

So, I sent the NSA a message on Facebook asking if:

  • The Enigma in the museum had been dimensioned and measured before; and
  • If so, could they share the measurements; and
  • If not, would they let me … come take it apart and measure it?

Yes, you read that right. I sent the NSA a message on Facebook. I’m certainly on some sort of list now.

Yeah, this was a pretty naïve thing to ask. For one, OF COURSE THEY WON’T LET ME TAKE APART AN ENIGMA. The second reason: while I do own a bunch of calipers, I had no idea at the time how many little parts are included nor do I know how to accurately dimensions and understand tolerances of parts. I guess I should have paid more attention during the Industrial Engineering and Engineering Graphics/Design courses I took in college.

The NSA guys were pretty awesome: they responded quickly, explained it hadn’t been dimensions and ignored the second half of my question. So, of course, I responded again and asked if I could fly out there and measure it. The answer, as one might expect, is .. again to remind me they don’t have blueprints and ignore my request. 🙂 However, this time they suggested I talk to the Enigma-Replica.com guys because their website says something about AutoCAD Drawings.

So, I hadn’t noticed AutoCAD Drawings mentioned before, and sure enough, there was a AutoCAD logo buried on an image on the website. I emailed Jim, the site owner of Enigma-Replica, and asked him if AutoCAD files were available, and that I was willing to pay for them if so. This conflicted me a bit — if someone provided AutoCAD files, I wouldn’t need to learn to model, but at least I could start printing parts of an Enigma machine! Jim responded within a couple of days saying that they don’t have AutoCAD files available, but why not just download the mechanical drawings from the Enigma Nachbauprojekt website. I hadn’t heard of this site, browsed over it rapidly, and found a PDF for the rotors, reflectors, and rack! HOLY CRAP! DRAWINGS! FREE! AND THEY ARE GLORIOUS. It looks as though these drawings were done by someone that’s well versed in mechanical engineering or industrial design, and I found this reference handy for deciphering the drawings.

As best as I can tell, this site was done by a team in Germany back in 2003 when they were creating an authentic replica of an Enigma. The measurements are amazing: properly toleranced, all the radiuses and chamfers defined, and properly laid out. There is absolutely no way I could have accomplished this myself given many days and all the calipers in my collection. This was an awesome resource that I hadn’t found. Why? Because in all my research for Enigma collateral, I was searching for things in English only. Turns out, there are several sites in German that document these things well. Hindsight is 20/20, no?

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