Saturday, September 30, 2023

More Zamac-trouble on a Mignon (and how to remedy)

Yet another Mignon, but this one with a serious Zamac-problem. (A small flock of Mignon Modell 4's have been passing by - giving good opportunity to learn how these can look fine and still be completely broken. Also to learn how these come apart - and go together again.)

The horizontal bearing on this machine was stuck solid in the cast-iron forked-lever from internal swelling. This meant that this Mignon could not type, as the index then won't budge vertically. When trying to remove this bearing to fix by sanding down, it unfortunately completely crumbled.

Then the only way to make the Mignon index-typewriter functional again, is to make a new replacement part. The dimensions of the horizontal bearing are metric and fairly standard; it essentially is a tube of 10 mm diameter with 8 mm internal diameter and 80 mm long. It has a flange to fix it to the main cross-casting, a large cut-out to accommodate the gear and one 'internal nail' to lock the rack.

The local DIY-store had 10 mm aluminium tube with 1mm wall-thickness and 2 mm thick strips of aluminium too. One metre lengths of both - to allow for several attempts at making replacement bearings :)

To get the pattern of the cut-out, papper was wrapped around the taped-together original. With a soft pencil, the cut-out was traced, like a brass-rubbing.

The pattern then cut out of the paper and traced onto a length of the aluminium tube. (A bit of extra length to allow clamping without damaging the bearing-surfaces.)

The pattern for the fixing-flange was also sketched and glued to 2 mm thick aluminium. The diameters of the holes are 10 mm (obviously) and 4 mm at a 10 mm pitch. The lug at top is 8 mm wide. This flange should be 3 mm thick. The DIY-store only having 2 mm strip, it'll be doubled to 4 mm.

All material having been marked, then patterns were drilled, sawed and filed. A lot of filing, actually. But then at the end of the filing, there is a replacement horizontal-bearing made out of solid aluminium.

As can perhaps be spotted in the image of the two side-by-side, I made a mistake when glueing the flange in-place on the tube (cyanoacrylate). It is placed ~1.5mm too close to the near edge. Another attempt new-part could be made, but after also shortening the far-end by ~2 mm  it's still functional and symmetrical. (Next time I'll measure twice before gluing once.)

At the very bottom of the fixing-flange a ~1.5 mm through hole must be drilled. From the inside, a short nail is driven into this hole. The ~4 mm head of this nail works as a guide for the gear-rack to stay aligned with the gear-wheel. Not an obviously visible feature of the Mignon mechanism, that nail.

The drawn 10 mm tube is a perfect fit for the cast-iron fork-lever, and allows the mechanism of the Mignon to again swivel back-n-forth for the vertical axis.

Also replacing the pin in this machine's shaft with a brass M2 bolt and nut (just visible), this Mignon index typewriter is again fully functional. Still not a speedy machine, but it writes again. To finish it off, the lettering of the ruler was touched-up and the machine given an overall polish. 

A fine machine. (Still wish that they hadn't used Zamac!)

Friday, September 22, 2023

Replacing a pin with an M2 screw on the Mignon index typewriter

To take apart the actuator arm of a Mignon index typewriter, a soft-steel pin has to be removed from the hollow main actuator rod. This 2mm pin holds the 'plug' with the ball-on-a-needle that is the vertical type-alignment bearing. Only when that is removed, can the parts be taken apart further; the actuator arm in bits:

This pin is in an awkward position. Pins are unpleasant to remove anyways, but this pin is very close to the delicate casting of the arm-assembly. Any stray hammer-tap on that part and it would shatter for sure. 

Also the horizontal bearing-tube is concerning; this also seems to be a fragile Zamac casting. Over time the material can swell and the part will then be very hard to slide out of the cast-iron forked-lever. On this machine only filing down of the centre-section was needed to get it out.

Putting it all together again, the needle-plug was fixed in the actuator-rod not with the pin, but with an M2 screw and nut. 

The brass M2 screw is a very tight fit (scraping), leaving no play between the parts. (Any play would introduce vertical type-alignment variation.) This screw is not authentic, but is normally not visible from the outside. More importantly; an M2 screw won't need hammering close to fragile Zamac castings and will make future repairs so much easier.

Also the soft pin that locks the horizontal-rod (right-end) was replaced with an M2 screw. The M2 nut is an exact fit in the slot of the horizontal-rod, making it an easy replacement. Again not authentic, but not very noticeable and much easier for future servicing. (Well, if there ever would be any, of course).

Most index typewriters were low-cost flimsy affairs, but the Mignon actually has a heavy cast-iron frame and is overall solidly-built.

It does have far fewer parts than a standard typewriter (and was about a third of the price), but it does have a similar build-quality. (Just wish that they hadn't used Zamac and pins!)

Sunday, September 10, 2023

American Typewriters catalogue, but who is it from?

A 'prospectus' or catalogue of 'Amerikaansche Schrijfmachines', i.e. American Typewriters.

And that's what it is, showing standard office typewriters from the major American makers. The booklet opens with the point that instead of only one make they sell all brands, so are better positioned to recommend the machine most suitable to your specific business needs.

The pages that follow have an illustration of a machine with a paragraph explaining that machine's commendable aspect. The major brands and types are all there, including even the Demountable and an Oliver. From the machines and features shown, the catalogues will date from about 1923.

Notable that the Woodstock has the briefest paragraph; unlike all other machines it gets no mention of a differentiating feature. It's a typewriter.

For private use or for small firms, also one portable machine is included; the Corona 3 folding portable.

This booklet may have lost an outer cover, because nowhere is mentioned who this office supply company is! There is no name or address anywhere. The staples however are tight around the current set of pages, no hint that a page or card cover is missing. When being given out back in 1923, it would have been accompanied by a letter, business-card or company circular - but even so, it seems strange to not have any mention of the trading company anywhere on the 16 printed pages.

There is on corners a medallion logo with an L, C, M and an '&'. That may well have been the initials of the trading company, but am mystified who that could have been.

This LC&M (or L&M C or etc...) becomes even more mystifying when seeing that this same logo is also on the back-cover of a ~1920 Comptometer instruction manual

To my best understanding Felt & Tarrant had their own offices in Amsterdam to sell and service Comptometers. The manual also is clear that it's by the Felt & Tarrant company in Amsterdam.

Was the Amsterdam office of Felt & Tarrant in reality a local dealership, i.e. a trading company also masquerading as a local F&T office? Or was the Felt & Tarrant office in Amsterdam selling a sideline in typewriters too - they already had a sales staff visiting larger offices and had repair capabilities. (Or is the logo merely a printer's way of making his mark?)

Either way; it's a nicely illustrated catalogue of American standard typewriters with their differentiating points - now available on The Archive

And it's also a little mystery; who was this published by? 

With archives being placed online, perhaps another booklet or newspaper advertisement will show up in time to clarify the logo :)

Monday, September 4, 2023

Refurbished Comptometer model H

This Comptometer model H got refurbished, again, in 2023 :)

The old, drab paint from a late 1930ies or 1940ies re-build was stripped from the panels.

The top-panels were re-painted in a matching brown copper-colour.

New keys were manufactured.

The new keys were fitted to cleaned key-stems.

The decimal-markers riveted back on the front display-cover.

The top-cover place back onto the mechanism and keys re-mounted.

New window and feet improvised and fitted.

And then the whole machine is put together again, clean and cosmetically very acceptable.

However, the column 6  had been malfunctioning - caused by sticky old lubricant. Closely watching what was going wrong to identify the cause (peering into the mechanism, operate machine, use flash-light). Then some prodding with a wooden skewer to get suspect parts unstuck. This fortunately confirmed that old grease was the cause. Hopefully with frequent exercise the problem will be solved, exercise is anyways important for all mechanical calculators. (Am not confident to take a Comptometer mechanism fully apart to get at the levers inside the 6th column!)

The view from the side gives a pretty good indication of the density of levers, rods and springs throughout the whole machine. It is amazing in its complexity, very clever - mechanically rather marvellous :-)

For example the holes-pattern in the intermediate gear in the register (only a small section visible) is functional (less mass, more speed) - it also is a mechanical detail that's just very nice to see.

This particular model H had been bought (cheaply) in a rather bad condition. On the (bad lighting) images of the listing it had looked fine, but seeing it in daylight after picking it up its drab finish was clear.  That, with  its decaying J-model plastic-keys were evidence that this was older rebuild.

It probably was rebuilt and re-sold already in the late '30s or 1940s. The calculator itself has serial number 209,945 and dates from around 1921. These were expensive office-machines (entry-model was about twice the price of a large standard typewriter). There was a market for rebuilt Comptometers, both by the manufacturer and third-parties. Rebuilding was especially common in the immediate post-war period, but also happened in the 1930s - the F&T company even advertised that they would not guarantee rebuilds by others.

The internal mechanism of this specimen had luckily survived quite well; almost no rust and clean with relatively little gummed-up old lubricant. Overall, Comptometers are amazingly durable - especially considering their complexity and the amount of fine-adjustments in the mechanism. 

So, after the initial disappointment of buying a badly-ageing rebuild machine; now it's a shiny clean Comptometer model H that calculates just fine. Perhaps almost as clean and as fast as it was back in 1921 :-)

Saturday, September 2, 2023

Improvising new feet for the Comptometer and a window-sheet

Comptometers have feet - although today many are sat flat on the table like a shoebox, they'd originally have had rubber feet. These feet were press-fits into holes in the bottom of the case, found in grey or black and usually completely decayed. They're either completely lost or pressed flush with the base of the machine, the rubber being pushed with a bulge into the interior. (Remnants of a foot can also sometimes be found floating about the inside of a case. Or stuck to the cork lining.)

To make a quick-fix set of feet, these were built-up from rubber. Of itself, the feet could be a good candidate for 3D printing replacements (FDM, PU rubber), but disk-stacking works gooed-enough. Using small drops of cyanoacrylate glue, disks of 10mm (one), 16mm (one) and 18mm (several) were glued together in a stack.

Using hole-punches, disks are cut from a sheet of 2mm rubber. Place dot of glue, place disk on top, centre properly and then press together firmly. As final element, self-adhesive felt-pads to get 'dampening' feet. 

These improvised feet are almost a press-fit into the recessed holes with the 10mm disk (10.5 would've been good, but no such hole-punch :-). To keep them in place, some extra hobby-glue is good enough (not cyanoacrylate!). This stacked method is a quick, improvised alternative to 3D printed feet. They simply work and Comptometer feet are not too visible anyways.

The windows over the numeral-wheels are covered with a single sheet of celluloid. The original sheet of celluloid on this machine was very yellow. Now that the keys were bright again, also wanted to have clear windows over the numeral wheels. A strip of 0.2mm thick clear-plastic was cut from a sheet - it was sold as 'mica-sheet' for crafting. No idea what plastic it really is, but it's fairly clear and can be cut easily. It is also flat, the window must be curved to fit under the front window-panel.

To create the curvature needed, it was placed over a ~33mm diameter tube held in place with elastic-bands. A hair-dryer then was used to heat the new window-strip to have it relax and settle in a curve. This sort-of worked; it is correctly curved, but it got some extra 'wrinkles' as well from the elastic bands. 

With better clamping of the sheet and better temperature control (oven?) this method could probably be improved on, but the quickly improvised new window looks fine. More importantly, it works: gives a clear view of the numerals and will stop dust and dirt getting into the mechanism.