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[3D photos of my Feld-Hell machine are here ] [Historical Feld-Hell photos are here]
©2007-2009 F. Dörenberg. All rights reserved worldwide. No part of this publication may be used without permission from the author. It has taken considerable effort to create these pages. If you "borrow" content from them, at least reference the source. Look, but don't steal!
Some tips for taking good photos of equipment are at the bottom of this page.
These photos have been down-sampled.
All photos are available as full size, high-resolution jpg
files. Just ask!
Contact me.
Front view of the Hell Feldfernschreiber
(paper supply drawers slightly pulled out)
Printer/keyboard and electronics units removed from the case
Electronics unit partially pulled out of the case
Top view of the printer/keyboard unit of the
Feldfernschreiber
- cover of the character drum removed -
Top view of the printer/keyboard unit of the
Feldfernschreiber
- cover of the character drum removed -
The character-drum is 20.4 cm long and has a diameter of ca.
4.9 cm (≈ 8x2")
Rear view of the printer/keyboard unit of the
Feldfernschreiber
- cover of the character drum removed -
Rear view of the
Mechanical Unit with the Keyboard-Drum Unit removed
Left side of the
motor-generator
Top part of the
motor-generator with regulator cap and scale removed
Top part of the
motor-generator with regulator cap and scale removed
The
contact plate of the speed regulator
Top part of the motor-generator with
contact plate removed, centrifugal weight
mechanism visible
The
centrifugal speed regulator disk
Top of the
motor-generator - centrifugal regulator removed, ball bearing visible
Here is a diagram that I made it to illustrate the construction of the motor-generator, and to guide its disassembly and reassembly (see the "maintenance" page). It is available as a high-resolution jpg file here (2.3 MB).
The following diagram illustrates the installation of the various drive shafts in the Feld-Hell's gearbox. The diagram will be included in the overhaul manual for the gear train.
Top view of the drive shafts installed
in the Gearbox
(worm drives of the
input drive shaft are located below the ball bearing shown at the center)
Perspective
view of the drive shafts installed in the Gearbox
(also
available as red/green anaglyphic stereoscopic ("3D") photo
here)
Perspective
view of the drive shafts installed in the Gearbox
(also
available as red/green anaglyphic stereoscopic ("3D") photo
here)
Front view of the
Mechanical Unit with the Keyboard-Drum Unit and motor-generator removed
A
look into the gear-box of the
Feldfernschreiber from the rear of the unit
- cam wheel at lower right is for the pause character key;
several gears are molded or machined out of Harex® or Turbax® (ref. 1) -
Spur gear (1, 2), bevel gear (3), helical
My great-grandfather and his
gears (4), worm-gear (5) and pinion ( 6)
bevel-gear-driven chainless bicycle, ca. 1914
Bottom of the motor-generator, with tappet of the pin-coupling to the gear-box
(note red alignment lines on the tappet and the base ring)
Top of the gear-box, with tappet of the pin-coupling
to the motor-generator
(note red alignment lines on the tappet, base ring, and link for coupling pin
from motor-generator tappet)
Generator carbon brush (left):
– 5 x 6.4 x 15 mm (HxWxL)
– turned head: 2 mm
– spring length: 25 mm (1”)
Character drum carbon brush (right):
– 3.9 x 3.9 x 15 mm (HxWxL)
– turned head: 2 mm
– spring length: 25 mm (1”)
Click here for some general information on carbon brushes.
Carbon brushes of the generator (left) and the character drum (right)
(shown with carbon brush holder caps)
Keyboard of the Feldfernschreiber
Note the
special "pause character" key to the right of the "P" key (similar to "E") - it
is unique to the Feld-Hell! The "green dot" key on the far left is the "Morse"
telegraphy key. The blank key at the bottom right is the "space" key.
Keyboard-Drum
Unit, removed from the Mechanical Unit
Bottom view of the
keyboard
Paper trays pulled out of the unit
Printing mechanism of the
Feldfernschreiber
(spindle (electro-magnet
is in the small box below it), ink roller, paper transport rolls)
Printing mechanism without cover
Spindle-magnet box removed
The spindle-magnet box viewed from the equipment side
The inside of the spindle-magnet box
(electro-magnet, spring-loaded armature, various adjustment points)
The only "Hell" markings (4) that I have found so far, are inside the printer
The hammer moves up about 0.4 mm when the electro-magnet is energized
The
electro-magnet is marked "0,06 CuL", "4090", and "15000".
That is: 0.06 mm Ø "lackisolierter
Kupferdraht" (enameled solid copper wire), 15000 windings, 4090 ohms (I measured
≈ 4075 Ω).
Front panel of the electronics unit of the
Feldfernschreiber
The round connector at the lower right-hand corner of the amplifier box mates with a plug that has 11 signal pins and a keyed center pin. The latter actuates a switch behind the socket. The connector and plug are actually borrowed from the Luftwaffe. Hence, they carry an Fl-number (Fl. 32620-1 for the "Steckerdose" socket and -2 for the "12-pol. Stecker" plug). They were made by Siemens-Halske. The bell-shaped housing of the plug is made of aluminium, and the insert is bakelite.
Round plug
for the 12-pin front-connector
Dimensions of the pins of the front-connector
Round plug
for the front-connector
(home-brew insert with pins for the
Hellschreiber's transmitter keying output and center pin)
Original connector of audio patch cable
The original 12 Vdc plug that came with the Hellschreiber
Plug for the La-Lb/E phone jack
The voltmeter - switchable between battery voltage and anode voltage
(Siemens-Halske, part number "T. Bv. 45/150, II P1")
Top of the electronics unit of the
Feldfernschreiber
(6
amp fuse and switch between two 12 V power sources (via round front connector);
note that the tubes can be replaced without opening the unit, and that the pins
of the tubes are accessible with a voltmeter)
Top of the electronics unit of the
Feldfernschreiber
with the tubes
removed
- the tubes (considered to be the least
reliable components) can be replaced without opening the unit ! -
Rear
of the electronics unit of the
Feldfernschreiber
- the white numbers next to solder lugs correspond to numbered points in the
schematic; also each component has a small round sticker on it, with a number
that corresponds to the component number in the schematic - takes the guesswork
out! -
Left side of the electronics unit, with connectors for the cables to the
printer/keyboard
(connectors are keyed differently and color coded)
Top
of the electronics unit, top & rear covers removed
Bottom
of the electronics unit, top with circuit board removed
Rear view of the electronics unit, circuit board removed
The bare one-piece die-cast electronics box, all components removed
(in above photo, note the (upside down) marking "T typ 58 13M" on the inside of front panel)
Top and circuit
board of the
electronics unit
(upside down, two tubes removed; shield box removed from transformer Ü17
(SÜ) in foreground)
Bottom view of
circuit board and top cover of the
electronics unit
Front
side of the circuit card and top cover of the electronics unit (upside down)
Left side of the circuit card of the electronics unit
Right
side of the circuit board of the electronics unit
Bottom of the printer/keyboard unit - part of latching mechanism on the right
(cover plate of the lower paper tray removed; top of the image shows
spring-loading of the trays)
15 mm wide Feld-Hell paper rolls
(a original 250
meter (820 ft) roll suffices for 9+ hrs of operation (82k characters);
originally, paper was used that was lightly gummed on the side not printed - per
item 12c on p. 6 of
the 1941 manual, this was a moisture protection). More on Hellschreiber
paper tape on
this page.
Above photos ©2008 F. Dörenberg N4SPP
 |
Ref. 1: Turbax is a brand name dating back to Jaroslaw's Erste Glimmer-Waren Fabrik (Jaroslaw's First Mica Products Factory) of Berlin-Weißensee in the 1930s, for a "Hartgewebe" ("hard fabric"); here: a cotton-reinforced laminate of a particular thermosetting polymeric resin (phenol-formaldehyde, PF). PF is the basis of bakelite®, a moldable sawdust-reinforced PF that was invented in 1907 and patented in 1909 by the Belgian Leo Bakeland (1863-1944), who emigrated to the USA at the age of 26; his patent expired in 1927. PF patents date back to the late 1890s. In sheet form, the equivalent of turbax is often referred to as Harex®, a trademark of Resopal® Werk H. Römmler GmbH (founded 1935). Turbax/harex is still used today for gears due to its flexible and quiet-running properties. This material can be machined like wood and metal, or be molded. Novotext, Tenazit, Thesit, Taumalit, Esconit, Bernit, Resinol, Resitex, Tenatext, Trolitan, Tufnol, Celeron, and Micarta are (registered) brand names for similar materials of other manufacturers. Later on, an other polymer replaced PF for many applications: polyepoxide ("epoxy"); it was patented in Germany in 1939 by I.G. Farbenindustrie, a company that became infamous for other chemicals (derived from sugar beet molasses) during WWII. |
"TURBAX Hartgewebe. Aus Gewebe und Kunstharz", Jaroslaw, 1938, 8 pages,
15 x 21 cm.
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Ref. 2: “Der SH-Feldschreiber“, Siemens-Halske AG, Berlin-Siemensstadt, SH 7535. 1.2.39. TT1., 11 pp. (courtesy Siemens Corporate Archives, München). |
PHOTO TIPS
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.
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Make sure that the camera is not moving at all when taking the photo:
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Equipment typically has parts that stick out (knobs, handles, ...). Shadows in your photo are really ugly, so only use diffuse lighting!
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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!
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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. |
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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 top the object |
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With a digital camera, only use optical zoom, never digital zoom |
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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. |
©2004-2009 F. Dörenberg N4SPP
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