ENIGMA I - Dora Reflector

Serial Number: 24b 656
Year of manufacturing: 1943
Chiffriermaschinen AG Heimsoeht & Rinke in Berlin-Wilmersdorf

• Project Status
  • TODO
• Rack/Plug Board - Gestell/Steckerbrett
  • Lever Assembly
  • Button Short Assy
  • Button Medium Assy
  • Button Long Assy
• Reflector - Umkehrwalze (UKW)
  • Reverse Roll
• Rotor - Walzensatz
  • Rollbody
  • Clamp
  • Complete Rotor
  • Rotors Stacking
• Internal Wiring
  • Reflector
  • Rotors
• Material Designation
• Acknowledgements

Why

This project was created to transfer the blueprints of every single component of an ENIGMA I cipher device in a digital format (.stl, in the future other formats will be available) useful for 3D printing and eventual production through Computer-aided manufacturing (CAM).

The idea originated from my desire to improve my skills in 3D modeling choosing a device that has always fascinated me. At the same time, the project was intended to be useful by providing the community with resources that were not yet available online.

Project Status

Module	Total Parts	Completed Parts	Percentage
Rack/Plug Board	73	17
Reflector	15	15
Rotor	19	19

TODO

• Lamp Holder
• Access Roll
• Compensator
• Roll Retainer Assy
• Axle Bottom
• Patch Panel
• Bent Low, Bent High
• Centering Device
• Axles
• Core
• Baseplate
• Contactor Plate
• Rack I
• Rack II
• Complete Rack (Entire ENIGMA Machine)

Rack/Plug Board - Gestell/Steckerbrett

Lever Assembly

Show Blueprint - 100 101

POS	Nr	Ref	Name	Material designation	Weight (g)
1	1	100 006	Lever	X12Cr13	56.06
2	1		Screw M3 x 6
3	1	100 043	Knob Lever	X12Cr13	4.48

Button Short Assy

Show Blueprint - 100 102

POS	Nr	Ref	Name	Material designation	Weight (g)
1	1	100 027	Button Head Top	X12Cr13	1.06
2	1	100 029	Button Head Glass	Glass	0.28
3	1	100 028	Button Head Bottom	X12Cr13	2.90
4	2		Spike
5	1	100 025	Button Short	X12Cr13	11.67
6	1		Nut M3 x 2.4
7	1	100 052	Spring	38Si7	0.84
8	1	100 026	Plastic Plug	POM-C	0.17
9	1		Screw M3 x 12

Button Medium Assy

Show Blueprint - 100 103

POS	Nr	Ref	Name	Material designation	Weight (g)
1	1	100 027	Button Head Top	X12Cr13	1.06
2	1	100 029	Button Head Glass	Glass	0.28
3	1	100 028	Button Head Bottom	X12Cr13	2.90
4	2		Spike
5	1	100 030	Button Medium	X12Cr13	13.57
6	1		Nut M3 x 2.4
7	1	100 051	Spring	38Si7	0.64
8	1	100 026	Plastic Plug	POM-C	0.17
9	1		Screw M3 x 12

Button Long Assy

Show Blueprint - 100 104

POS	Nr	Ref	Name	Material designation	Weight (g)
1	1	100 027	Button Head Top	X12Cr13	1.06
2	1	100 029	Button Head Glass	Glass	0.28
3	1	100 028	Button Head Bottom	X12Cr13	2.90
4	2		Spike
5	1	100 031	Button Long	X12Cr13	15.19
6	1		Nut M3 x 2.4
7	1		Screw M3 x 12
8	1	100 026	Plastic Plug	POM-C	0.17
9	1		Screw M3 x 16
10	1	100 054	Sleeve	S235JR	0.73

Reflector - Umkehrwalze (UKW)

The reflector known as the reversing drum or, from the German, the umkehrwalze (UKW) is a fixed wiring mechanism within the Enigma machine. After the input character is encoded by passing through a series of rotating cipher wheels (known as rotors, see below), the signal would then be sent to the Reflector and back to rotors again. Instead of producing a new letter substitution, the Reflector's purpose was to create a reciprocal mapping of letters, effectively ensuring that the encryption process is symmetric. This means that if a letter "A" was encrypted as "D," the decryption process would reverse this, decrypting "D" back to "A". Enigma can then be used to both encrypt or decrypt a message using the same initial settings. Unfortunately, incorporating a reflector into the system introduces an encryption vulnerability: the encrypted version of a given letter can never be that letter itself.

Reverse Roll

Show Blueprint - 300 100

POS	Nr	Ref	Name	Material designation	Weight (Kg)
1	1	300 009	Axle	S235JR	0.0004
2	1	300 002	Cabinet	S235JR	0.1364
3	4		Countersink M2 x 4
4	3		Countersink M3 x 6
5	1	300 003	Wedge Holder	S235JR	0.0529
6	2	300 004	Wedge	S235JR	0.0096
7	4		Countersink M3 x 5
8	3		Screw M1.6 x 4
9	1	300 008	Isolator Plate	PA6 (Black)	0.0002
10	24	300 005	Blank	CuZn40	0.0003
11	26	400 010	Contact Die	CuZn40	0.0001
12	6	400 013	Thread Bushing	S235JR	0.0011
13	3	400 019	Thread Bushing Small	S235JR	0.0004
14	1	300 001	Reverse Roll	PA6 (Black)	0.0044
15	2	300 007	Screw Plate	S235JR	0.0001
16	24	300 006	Bushing	CuZn40	0.0019
17	26	400 017	Spring	CuZn40	0.0000
18	26	400 018	Spring Pin	CuZn40	0.0003
19	1	400 015	Coping	PA6 (Black)	0.0065
20	3		Countersink M3x8

Rotor - Walzensatz

Rollbody

Show Blueprint - 400 101

POS	Part Nr	Name	Material designation	Weight (Kg)
1	400 012	Steel Bushing	S235JR	0.0084
2	400 016	Contact Pin	CuZn40	0.0003
3	400 011	Rollplate	PA6 (Black)	0.0090
4	400 010	Contact Die	CuZn40	0.0001
5	400 009	Center Toothed Wheel	PA6 (Black)	0.0345
6	400 019	Thread Bushing Small	S235JR	0.0004
7	400 017	Spring	CuZn40	0.0000
8	400 018	Spring Pin	CuZn40	0.0003
9	400 013	Thread Bushing	S235JR	0.0011
10	400 014	Toothed Wheel	S235JR	0.1140
11	400 015	Coping	PA6 (Black)	0.0065
12		Countersink M3 x 8

Clamp

Show Blueprint - 400 102

POS	Part Nr	Name	Material designation	Weight (Kg)
1	400 006	Clamp	38Si7	0.0013
2	400 007	Pin	S235JR	0.0004
3	400 008	Cap	S235JR	0.0004

Complete Rotor

Show Blueprint - 400 201

POS	Part Nr	Name	Material designation	Weight (Kg)
1	400 003	Bushing	S235JR	0.0540
2		Countersink M2 x 5
3	400 001	Kerfring	S235JR	0.0169
4	400 002	Digitring	X12Cr13	0.1130
5		Clamp
6	400 005	Bracket	S235JR	0.0020
7		Countersink M1.6 x 2.5
8		Washer M1.2
9		Screw M1.2 x 2
10		Countersink M1.6 x 4
11		Rollbody

Rotors Stacking

Show Blueprint - 400 301

POS	Part Nr	Name	Material designation	Weight (Kg)
1	400 004	Roll Shaft	S235JR	0.0270
2		Rotor III
3		Rotor IV
4		Rotor V

Internal Wiring

Reflector

The wiring of each rotor is referred to the sequence of the eintrittzwalze (ETW, entry disk) located on the right of the first rotor.

		Notch	Turnover
ETW	ABCDEFGHIJKLMNOPQRSTUVWXYZ	-	-
UKW-A	EJMZALYXVBWFCRQUONTSPIKHGD	-	-
UKW-B	YRUHQSLDPXNGOKMIEBFZCWVJAT	-	-
UKW-C	FVPJIAOYEDRZXWGCTKUQSBNMHL	-	-
UKW-D (Dora)	rewirable / custom	-	-

Rotors

		Notch	Turnover
ETW	ABCDEFGHIJKLMNOPQRSTUVWXYZ	-	-
I	EKMFLGDQVZNTOWYHXUSPAIBRCJ	Y	Q
II	AJDKSIRUXBLHWTMCQGZNPYFVOE	M	E
III	BDFHJLCPRTXVZNYEIWGAKMUSQO	D	V
IV	ESOVPZJAYQUIRHXLNFTGKDCMWB	R	J
V	VZBRGITYUPSDNHLXAWMJQOFECK	H	Z

Material Designation

S235JR

S235JR is a European standard non-alloy, low carbon, manganese-containing structural steel commonly supplied in the untreated or normalised condition. It is easy to weld and bend. Similar desginations are: SS1312, 1.0038, Fe 360 BFN, RSt37-2, 40 B, SB1312, IM2191.

X12Cr13

Martensitic grade chromium steel which exhibits good mechanical properties coupled with good corrosion resistance in moderately corrosive environments. It is used for the production of components working in contact with water and steam. It exhibits very good resistance to adipic, arsenic, benzoic, boric, maleic, gallic, and malic acid, or at low temperatures or concentrations to: nitric, chromic, gallotannic, carbolic, barium, aluminum, and potassium acids, and ammonium hydroxide. It is not resistant to salts and sulfur compounds. It does not exhibit significant strength properties compared to conventional structural steels due to its relatively low carbon content, but unlike steels with a higher carbon content, it is more resistant to corrosion.

38Si7

Medium-carbon spring steel used in quenched and tempered condition. The primary designation is to have high yield strength and resilience. For this, it is used for spring rings, spring plates, screw locks and load securing devices. It has a very low density among EN wrought alloy steels. In addition, it has a moderately low embodied energy and a very low base cost. Similar desginations are: EN 1.5023

CuZn40

A copper-zinc alloy with a duplex alpha-plus-beta phase structure and excellent hot-working properties. Service environment must be considered to predict corrosion behaviour. CuZn40 has somewhat better cold-working and joining properties, but is less readily machined, than the similar low-leaded alloy CuZn40Pb. The most commonly used wrought forms are plate, rod and sections/shapes.

PA6

Polyamide 6, also known as Nylon 6 is a widely used industrial polymer. Nylon 6 fibres are tough, possessing high tensile strength, as well as elasticity and lustre. They are wrinkleproof and highly resistant to abrasion and chemicals such as acids and alkalis.

POM-C

Polyacetal, also commonly known as acetal or polyoxymethylene, is a formaldehyde-based, semi-crystalline engineering thermoplastic. It is widely used in the production of precision parts for applications demanding good dimensional stability and sliding properties. The polymer serves as an alternative to metals due to its low friction and wear characteristics as well as its excellent balance of mechanical and chemical properties.

Acknowledgements

Thanks to Ms. Luzia Jans for providing all the drawings/blue prints in the context of the scientific project "DIE ENIGMA - Nachbau der legendaeren Chiffriermaschine". The original ENIGMA machine (serial 24b 656) on which all the drawings are based, is present in the Wehrtechnische Studiensammlung museum in Koblenz (Germany).