AEG Mignon typewriter with Rheinmetall logo

In the process of giving a Mignon index typewriter a thorough cleaning, the carriage was taken apart. This particular Mignon was made by AEG sometime in the late 1920s and in keeping with the overall heft of the machine, the carriage frame is cast iron.

There is a shield with the machine serial-number riveted to the casting and the middle-tie has lettering "SMa" over the number 6001. The 6001 may refer to the pattern or drawing-number, the meaning of "SMa" could be a simple as "SchreibMAschine" or typewriter.

Castings sometimes also have a mark of the foundry, when not manufactured by the typewriter-factory itself and sub-contracted out. This casting indeed does have such a mark. Unexpectedly, the logo on this casting is the Rheinmetall logo.

Clearly marked with the circle and inverted quarter-circles, as also used strikingly on the front-panel of their typewriters of the same period.

(wordmark image from a user manual on The Classic Typewriter Page)

The factories of both companies were also 'next door' to each other, the Rheinmetall site at Sömmerda is not too far away from the AEG typewriter-factory in Erfurt. 

It's thus likely that in the 1920s Rheinmetall not only made their own typewriters, but was also a parts supplier to AEG, the later Olympia.

Refreshing a Mignon typewriter character field or keyboard

The 'keyboard' or character-field of a Mignon index typewriter is where the desired character is selected with the pointer. This map or field is a curved plate, covered with clear celluloid. After 90 years or so, on some key-boards, the celluloid is not so clear anymore - and what was worse on this specimen; the old plastic started to crack and crumble.

Because it was falling apart and catching the index-pointer, this 'keyboard' was taken apart for replacing the clear plastic with new. There are a great many tabs around the rim; after carefully bending these open, the stack of a fibre backing-plate, aluminium sheet with the characters and the celluloid top-sheet can be taken out.

A replacement top-sheet of about 81.5 by 128.5 mm was cut from clear plastic sheet. With this new sheet, the difference in legibility is very noticeable. Bending back all the tabs very gently, fortunately only one tab broke off. (If this new plastic sheet will last another 90-odd years before its starts to crumble and needs replacing, then the keyboard has enough redundancy in tabs to last it at least a few centuries ;-)

The index-pointer no longer snags on the keyboard-cracks; smoother sheet, smoother working of the cheap-n-cheerful Mignon :)

New typeshuttles for the Hammond - more iterations

It's getting there.

It's iterative development, almost every prototype uncovered something new to improve or a new fault-mode.

Now at version 14 of the reproduction typeshuttle, the mechanical function and interaction with the machine is fine. The design is now at the stage where precision of the type itself needs improving. The rapid prototyping strips can't create proper stems of e.g. the 'p' or 'h', as can be seen from the type-sample.

Original at the left, reproduction at the right.

The Hammond typewriter itself is an impressively complex (and finicky) piece of machinery - my Multiplex needs some work done too :)

Mignon index typewriter - oiling of roller wheels

The Mignon index typewriter is a pretty common machine still, many were sold and they are sturdy. (To quote Helen Howes: "They don't compost well, so there are lots still kicking about.") 

For an index typewriter it is also somewhat over-engineered - the cast-iron frame and overall sturdiness impresses. These machines do have several 'weak spots' however; it's prone to rust and the feed-rollers generally have deteriorated. The use of pins also is unfortunate, e.g. removing the platen can be hard. Nevertheless, as a cheap-n-cheerful common machine they're a good subject for tinkering. Well, actually these aren't all that cheap - despite being 'common as mud' overhere, their unusual appearance probably increases the market for these and they do sell for more than a comparable type-bar machine.

Anyhow - this late 1920s Mignon Modell 4 got a complete rebuild of the machine-base, but still did not work very well. The carriage moved very stiff, as it if was binding. That probably was the reason someone, decades ago, mangled the spring to increase the pulling-force. Bad.

Inspecting the carriage rail and guide, these all seemed straight. The carriage slides with its cast-iron frame over a steel rod in the front and rests on a roller at the back.

Could it be as simple as a stuck roller, that was being dragged over its race? The carriage of a Mignon can be taken off very easily; place the left margin-stop lever in an 'up' position to clear the central-stop, press down the 'space' and simply slide it off to the right.

This wheel was indeed firmly stuck. With a bit of oil, temporarily loosening its bolt and forcing it round it quickly whirred round freely again. One roller oiled.

The Mignon actually has two 'space' or 'carriage-release' controls. On the machine base, the space-key (a) will space the carriage when pressed. If it kept pressed down, it acts as a carriage-release. On the carriage, the lever (n) releases the carriage allowing it to be moved freely. Giving this carriage-release lever a single 'press' will however space the carriage.

When pressing down the 'space'-key on the machine itself, the carriage could now be moved freely - no binding or friction at all. When however pressing the carriage-release lever on the carriage itself, it still moved sluggishly - very stiff.

Some more peering into the mechanism revealed that the controls (a) and (n) act via a different path. The space-key (a) pulls back the ratchet, whereas the carriage-lever (n) pushes it back via a roller-wheel. It turned out that this roller wheel was also seized-up solid and sliding over the release-bar of the carriage.

Again applying oil and forcing the roller round made it unstuck - again rolling freely over the long bar that pushes the ratchet away. 

Now, with both rollers oiled, the carriage moves freely and the machine spaces correctly - even with its mangled spring.

Instead of mangling the spring, oiling these two rollers would've probably been a better remedy - something at least - for a next time a Mignon-carriage advances sluggishly.

Remington Portable adding machine on its feet again

The rubber feet of 1930s Remington Portable adding machines are nearly always 'gone'. That is - they will be present, but invariably are hardened and/or completely squashed. As in this wreck-machine below:

As a finishing step of reviving this machine, the gone-to-goo old feet were broken off the machine. A hole may need to be pried in the centre of a foot to get at the mounting screw. When removed, the foot-remnants should be completely broken apart to retrieve the washer. (This washer would originally have been moulded into the rubber foot.)

New feet that are a decent-enough fit were modeled in CAD. In this case, printed in regular 'plastic' and not in rubber. The conical washer is needed as insert - designing the foot with separate washer makes it possible to print on an FDM 3D-printer. It's not a difficult or critical part, any printer should be able to create this fine - STL-files available for download here.

The tapering top of the foot is needed to clear the various pins and screw-heads that poke through the base into the foot-pocket of the machine-base. The pocket allows mounting the feet with the original, salvaged screws and washer.

Original feet had a circular 'tread' - as shown below. This pattern would actually be fairly easy to create with 3D-printed feet in rubber, but in this case settled for basic, hard feet to be soled with felt (or alternatively, a pad cut from self-adhesive rubber sheet).

The printed feet here finished with a 'sole' from furniture-pad felt, great for sound-dampening. Adding some latex-glue to the felt made the feet grippy. Had grey felt, so blackened the sides.

The Dalton adding machine thus on its feet again and fully functional.

These 1930s Brennan-type Remington Rand adding machines are pretty common today on the usual auction and classified sites. They can only really add numbers (which they do very well and they print a list too). Perhaps not very exciting machines and indeed they are not very valuable today. 

Still, if you can find a decent-looking and complete specimen: they are brilliant late-1920s digital-technology and can basically last forever.

Oiling the level too

After topping-up the oil level in an adding machine, also added oil to the spirit level :)

At 2.50 a relatively expensive thrift-store find, but it looked intact and had a brass "JNij" medallion; so made by J. Nooitgedacht & Zn, IJlst. A well-known (at least here) maker of woodworking tools and skates, started in 19th century and now defunct.

The tool is made of oak with brass fittings. The protective covers over the levels are 'plexiglas', so probably a 1950s item.

By coincidence, also this exact item is pictured in the 1950s tool catalogue.

The description fits, including the optional extra 'feet'; brass end-plates. The description also confirmed that it originally was delivered 'oiled'.

When picked-up from the tools-bin at the store, it looked rather dirty, dry and tired. After wiping with soft-soap to remove much dirt, a few helpings of boiled linseed oil were applied with a rag. After a good rubbing, the wood regains 'depth' and is protected for another couple of decades use as a tool.

New typeshuttles for the Hammond typewriter - iterations

The current state of the (slow, intermittent) effort to be able to use the Hammond Multiplex with new typeshuttles; two new, improvised shuttles on the machine:

Last year, when ordering 3D printed parts for a reproduction Hammond spool, also ordered some first test prints for a typeshuttle. These were printed from a fairly simple 3D model, with straight 'slugs'.

This was mostly meant as a test for the dimensions. The Hammond typeshuttle has an awkward design without obvious angles or dimensions (at least, not obvious to me). Despite this first-version typeshuttle strip being very basic, it showed promise and with an improvised flange it actually provided (somewhat) legible typing!

This first attempt was printed on a resin-printer with high resolution. Very crisp, no visible layering or artefacts at all! The first-version shown below on the Multiplex; it's also obvious that the strip is too thick.

As it did indeed look promising, an improved 3D model was created with tapered 'slugs'.

To make the iterations in design a bit faster, this was simply printed on an FDM printer. With a filament printer in PLA, the printed part does clearly show layers. However, with a layer-height of 0.08 mm and great horizontal precision this is not too much of an issue. With FDM, the parts are easily printed and good enough to validate the design.

An example FDM printed reproduction typeshuttle shown below on the right, next to an original on the left.

Again, reproduction with improvised flange on the right, original on the left.

The thin flange with the take-up for the vane to actuate the typeshuttle is a tricky part - that especially will require more thinking and probably several iterations to get right. Even this FDM-printed typeshuttle does actually type (somewhat):

Even though the print-quality is terrible still, this Hammond Multiplex typed a bit in 'script'. The bad print quality is probably also caused by a badly-inked ribbon; another thing to try to remedy on this machine.

More tweaking to do - and to get a better ribbon (more ink). A slow and intermittent project, but fun to do and still shows promise. Exploring this also gave more insight in the actual workings of a Hammond typewriter and how some of the first shuttle-design aspects 'echo through' in the anvil & shuttle - fascinating machine :)