Trying another source for new 7/16" ribbons

A proper ribbon for the Hammond Multiplex should be 7/16" wide - about 11 mm. Older Oliver typewriters also use this ribbon size. On a Hammond it could be possible to use a standard 1/2" (~13 mm) ribbon with a modified shield, but it's a bad fit on the spools and besides that, it would be 'wrong' :-) An Oliver also could take a 1/2", but likewise a bad fit with crumpling of the ribbon in the ribbon-vibrator.

Inking a satin-weave 10mm ribbon does work, but these modern ribbons are fairly stiff and probably less ideal for use on a Hammond with its complex printing with a ribbon exposed through the small window in the shield.

Another source for non-standard ribbons is then cassettes made for dot-matrix printers. Also cash-registers, time-clocks or adding machines still use ribbons in cassettes. The vast majority of these cassettes contain a standard 1/2" ribbon of varying length (anywhere between 0.8 m and 40 m!), but some cassettes have unusual widths, such as 1/4", 8mm or 16mm. Conveniently, the cassettes for e.g. the Siemens Nixdorf NP06, the IBM 4212 or 4683 and for the Olivetti PR4 actually contain 7/16" typewriter ribbon!

From old stock, a generic cassette for the Olivetti PR4 was obtained online that should contain ~13 m of 7/16" black ribbon.

Opening up the cassette, the ribbon is not wound onto a spool, but crumpled into the cassette-box - it is spliced to form a continuous loop. The green gears grip and drive the ribbon.

The loop was cut - the ribbon taken out and then wound onto the old Hammond spools - a good fit. The ribbon still 'zig-zags' a little on the typewriter, but should straighten out in time.

Trying to type with it - this 7/16" ribbon is unfortunately very dry. It either is dried-out, or it is dry-by-design because it was made for the very firm 'wallop' of the needles of a dot-matrix printer. (The line-feed on this Hammond is by the way still unreliable, the rollers are cracked and glassy-smooth.)

The faint printing does show that it should be possible to get this Hammond to write again - next step perhaps is to try for a more heavily inked, wetter ribbon. (Because the type-shuttle is made of hard rubber, oil-based inks could risk damaging the shuttle. Something to be thought about.)

At any rate, even though not quite ready-to-use in a Hammond, printer-cassettes are definitely a source of finely-woven ribbon of non-standard sizes :)