Sunday, June 23, 2024

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.

No comments:

Post a Comment