Feld-Hell photos

This page shows numerous photos of my first Hell Feldfernschreiber (Feld-Hell) machine. All photos have been down-sampled. They are available as full-resolution jpg files. You can contact me via the menu at the bottom of this page.

[Equipment set]
[Amplifier box]
[Keyboard and character drum]
[Base module]
[Motor-generator]
[Gear-box]
[Printer module]
[Tips for taking good photos]
[References]

3D/stereoscopic photos of my Feld-Hell machine (and other Wehrmacht equipment) are on this page. Historical photos of Feld-Hell machines are on this page.

Latest page update: 3 March 2023 (expanded the paper tape drawer part of the "base module" section)

Previous updates: 31 January 2017.

THE FELD-HELL SET IN ITS "TORNISTER" CARRYING CASE

Fig. 1: front-view of the Hell Feldfernschreiber

(compartment with paper tape rolls closed (left) and drawers slightly pulled out(right))

Fig. 2: electronics box partially pulled out of the case

Fig. 3: printer/keyboard and electronics units removed from the case

AMPLIFIER BOX OF THE FELD-HELL MACHINE

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Fig. 4: front of the electronics box of the Feld-Hell machine

Fig. 5: top of the electronics box

(the four vacuum tubes can be pulled out, without opening the box)

Fig. 6: top of the electronics box - vacuum tubes pulled out

Fig. 7: rear of the electronics box - cover removed

(note that all the wires/signals are numbered on the circuit board; all components have a sticker with a number)

Fig. 8: left-hand side of the electronics box with connectors from motor-generator and base-module

Fig. 9: top-view of inside of the electronics box - rear cover and module with circuit card and vacuum tubes removed

Fig. 10: top-view of inside of the electronics box - rear cover and module with circuit card and vacuum tubes removed

Fig. 12: rear-view of inside of the electronics box

Fig. 13: the die-cast box, all components removed

Fig. 14: bottom-view of the circuit card & vacuum tubes module

Fig. 15: front-view of the circuit card & vacuum tubes module

Fig. 16: left & right side-view of the circuit card & vacuum tubes module

KEYBOARD AND CHARACTER-DRUM OF THE FELD-HELL MACHINE

Fig. 17: the keyboard/character-drum module

Fig. 18: bottom of the keyboard - 3-pole connector to the base-module in lower right-hand corner

Fig. 19: left-hand side of the keyboard/character-drum module with gear that mates with the gear-box

Fig. 20: rear-view of the keyboard/character-drum module

Fig. 21: keyboard/character-drum module - character-drum removed

Fig. 22: the character-drum

MOTOR-GENERATOR OF THE FELD-HELL MACHINE

Fig. 23: cross-section of the Feld-Hell motor-generator

Fig. 24: the single-rotor motor-generator and the corresponding cross-section drawing

Fig. 25: top of the motor-generator - speed-adjustment cap removed

(the flat yellow capacitor is a modern replacement)

Fig. 26: speed-regulator disk with contacts (normal & overspeed) and EMI-supression components

(the flat yellow capacitor is a modern replacement)

Fig. 27: looking down into the top of the motor-generator - cap and speed-regulatro contact disk removed

(the

Fig. 28: the centrifugal part of the speed-regulator

Fig. 29: side-view of the centrifugal part of the speed regulator

(as rpm increases, the weight (far left) moves outward, the steel ball at the center moves up, and actuates the contacts of the disk above it)

Fig. 30: looking down into the top of the motor-generator - speed regulator removed, motor shaft visible

(the two electrolytic capacitors at the lower right-hand are are modern replacements)

Fig. 31: the single rotor of the motor-generator - separate commutators for the motor and the generator

Fig. 32: looking down into the motor-generator - speed-regulator, carbon-brushes, and rotor removed

Fig. 33: bottom of the motor-generator with pin-coupling (left) and top of the gear-box (right)

(note the thin red alignment markings (aid for re-assembly))

THE BASE-MODULE OF THE FELD-HELL MACHINE

The base-module contains the gear-box and the two drawers for rolls of paper tape, ansd is the mounting platform for the motor-generator,the keyboard/character-drum module, and houses the two-position locking mechanism for the carrying case.

Fig. 34: front of the base-module - printer module attached

Fig. 35: rear of the base-module

(the 3-pin connector on the far left connects to the keyboard/character-drum module)

Fig. 36: bottom of the base-module

(the spring-loaded lever on the left is for locking the base module in two positions in the carrying case)

Fig. 37: bottom of the base-module - covers and locking-lever removed, bottom of lower paper tape drawer fully visible

(note the bossed "T typ 58" at the lower left-hand corner of the casting and the Siemens-Halske logo at the top of the drawer)

Fig. 38: front of the base-module - paper tape drawers partially pulled out

Each paper tape drawer can easily be removed from the base module: fully push-in the black button next to it. This releases the drawer. Then pull the drawer straight out - as far as it goes. Push the buton in again, and keep it pushed-in while you completely pull out the drawer. You may have to wiggle it a bit while pulling To put the drawer back in, keep the associated black button pushed in, and insert the drawer. This typically takes some more wiggling.

Fig. 39: bottom of the base-module - cover and paper tape drawers removed

Fig. 40: Front of the base module - cover of drawer compartment and paper tape drawers removed

The actual drawer is diecast aluminum. A spring ring is mounted inside the drawer with four M3 screws. See Fig. 41. It is made of an aluminum strip. The paper tape roll is installed horizontally. So, the tape itself is oriented vertically. However, the paper tape has to enter the printer module horizontally. The unrolled tape passes though a slit in the ring. This pre-rotates the paper tape by 45°, before being rotated another 45° by the horizontal slit in the wall of the base module. See Fig. 430. The ring has a bump-out protrusion. This facilitates installing and removing of a full roll of paper tape with a thumb or finger.

Fig. 41: The paper tape drawer and the round spring

Two drawer sliders are mounted on the left-hand and right-hand sid of the drawer. They are slightly tapered at the rear - to facilitate insertion. There is a "catch" near the right-hand front corner of the drawer. See Fig. 42. When the drawer is fully inserted, this catch can be released with the black push button in the base module, to the the right of the drawer.

The paper tape roll is placed onto the thin turntable disk (aluminum). The disk has a ball bearing hub at the center. See Fig. 41. The ball bearing is held in place with two press-fit cylindrical inserts and a press-fit ring. See the left-hand diagram of Fig. 44. The somewhat flimsy cap of the hub can be twisted off with some effort. Be carefull not to squash the cap in the process! The turntable rotates very slowly, so this ball bearing basically never wears out - contrary to some of the other 11 ball bearings in the machine.

Fig. 42: The turntable disk inside the drawer

A small spring-loaded rod brake rides on the side of the turntable disk. It is mounted in the inside wall of the tray. See Fig. 42 and 43. Its purpose is to apply a small drag to the turntable, to maintain a slight tension on the paper tape. However, this seems to be an unnecessary luxury: there is sufficient friction on the paper tape, due to the slit in the ring spring, the slit in the side of the base module, and the blade spring of the ink roller lever arm. The latter spring pushes the paper tape onto the printer module. Also: the turntable will only turn if the roll of paper tape is full, or its core has an inside diameter (ID) that fits tightly on the hub of the disk. However, the official Feld Hell manuals (ref. 4A-4C) specify an ID of 30 ±1 mm [ = 29-31 mm] and 29 +1 mm [ = 29-30 mm], which is 1-3 mm larger than the 28 mm outer diameter of the hub (see Fig. 44)...

Fig. 43: The location of the rod brake and the components of the spring-loaded rod

There is a 2-step conical stud at the center of the drawer, for mounting the ball bearing of the turntable disk. See Fig. 43 and 44.

Fig. 44: Cross-sectional diagrams of the ball-bearing hub of the disk and of the mating stub at the center of the drawer

GEAR-BOX OF THE FELD-HELL MACHINE

The motor-generator is mounted on top of the gear-box, and has three output shafts: two on the front (printer spindle and paper tape transportation), and one on the right (character-drum).

Fig. 45: the gear-box

(motor-generator, pin-coupling, printer module, keyboard & character-drum removed)

Fig. 46: schematic top-view of the gear-box - ball-bearing at the center is for the vertically installed input shaft

Fig. 47: the gear-train of the Feld-Hell machine - ball bearings removed

Fig. 48: the gear-train of the Feld-Hell machine - ball bearings removed

In case you wonder how I took the above two photos of the gearing - it was not easy: I suspended all five shafts like marionettes, with mono-filament fishing line.

Fig. 49: the gear shafts, suspended for taking photos

Fig. 50: pin-coupling between the motor-generator shaft (top) and input shaft of the gear-box (bottom)

Fig. 51: the large steel gear on this output-shaft of the gear-box meshes with the large gear on the character-drum

Fig. 52: the drive shaft to the printer spindle

(the greenish socket for the ball bearing is mounted into the front of the gear box)

Fig. 53: driver shaft of the paper tape transportation

Fig. 54: rear-view of the gear-box, cover removed

(the horizontal shaft is the output to the character-drum; bottom-right: timing/interrupter cam-wheel for the pause-character)

Fig. 55: bottom-view of the gear-box; main (vertically installed) shaft with bottom ball bearing (shielded), spindle & paper transportation shafts

(front of the unit is on the right-hand side)

Fig. 56: several types of gear (left) and my great-grandfather with his gear driven (chainless!) bicyle (ca. 1914)

(spur gear (1, 2), bevel gear (3), helical gears (4), worm-gear (5) and pinion ( 6))

PRINTER-MODULE OF THE FELD-HELL MACHINE

Fig. 57: the printer-module (left) and the front of the base-module without the printer

Fig. 58: front and rear of the printer-module

Fig. 59: bottom & front of the printer-module, cover removed

Fig. 60: the printer solenoid (electro-magnet) with hammer armature

Fig. 61: left-hand side of the printer-module and the spindle holder

(note the HELL marking on the spindle holder)

Fig. 62: the two-start Hell printer spindle

Fig. 63: top-view of the printer module, with paper tape

Fig. 64: felt ink roller with holder and two spares

TIPS FOR TAKING GOOD PHOTOS OF EQUIPMENT

Good photos of equipment are clear, evenly exposed, have true color, are undistorted (barrel, skew, fish eye), and have no shadows on the equipment. If you want to take good photos of equipment, there are some simple rules to keep in mind...

Make sure that the camera is not moving at all when taking the photo:
always use a tripod
always use timer-release
Equipment typically has parts that stick out (knobs, handles, ...). Shadows in your photo do not look nice, so only use diffuse lighting!
never use flash
never take photos in direct sunlight
best is outside on a very cloudy day
it is OK to have shadows that are not on the equipment, as they can be edited away afterwards
The color of all (!!) objects anywhere near the equipment (including the background and the surface underneath the equipment!!!!) are reflected on the equipment. This can not be removed from the image afterwards!
Use a non-glossy neutral background (white/grey/beige or darker color similar to that of the equipment) around & underneath the equipment. Never use bright, contrasting colors (neon green, orange, red,...).
We are not going for artistic effects, so large depth-of-field is preferred ( = the entire object is in focus, at all distances from the camera). This can be achieved by taking the picture form a greater distance (with zoom, if required), or - if your camera has a manual mode - select a small aperture and/or a longer exposure time.
Fill the image with the object of interest, but for depth-of-field reasons (and to avoid so-called "fisheye" distortion), use zoom rather than getting very close to the object. This also minizes keystoning and other undesirable perspective effects.
With a digital camera, only use optical zoom, never digital zoom.
If the equipment, or any of its visible parts, has a shiny (reflective) surface, then make sure that no undesirable objects are visible in the reflection.
Use image/photo editing software to remove all background and objects that are not part of the equipment (sorry, but Photoshop, etc., are not particularly suitable for this), and to correct distortions (fisheye, skew, perspective,...).

REFERENCES

Ref. 4: "Der Feldfernschreiber" - original military manuals
Ref. 4A: "Der Feldfernschreiber", document D 758/1 of the Oberkommando des Heeres, Heereswaffenamt, Amtsgruppe für Entwicklung und Prüfung, Berlin, 1 April 1941, [this is the official original Wehrmacht manual in German for model 24a-32 (a1 and a2)]. Here is another scan of this document, with high image quality. [30 MB]
Ref. 4B: "The Hell Feldfernschreiber", the above D 758/1 "Der Feldfernschreiber" document, translated into English and annotated by me, Frank Dörenberg; updated 2 May 2009.
Ref. 4C: "Der Feldfernschreiber", Luftwaffen Dienstvorschriften L.Dv. 702/1 Heft 213, "Luftnachrichtentruppe – Ausbildung am Gerät, Teil 1 - Gerätebeschreibungen", Reichsluftfahrtministerium (RLM), 21 November 1940 25 MB; this is the Luftwaffe Feld-Hell manual; counterpart to the Army manual D 758/1 below]
Ref. 4D: "Der Feldfernschreiber", LDv 702/1, Heft 213; pp. 8-27 in "Fernschreibmaschinen", Heft 2 of "Fernschreibgerätelehre", Fsg-2, Arbeitsunterlagen für nachrichtentechnisches Unterricht, Luftnachrichtenschule, Halle (Saale), 2. Auflage, July 1943, 107 pp. [high-resolution scan - 400 dpi; 47 MB]