Wednesday, July 12, 2023

An influx of Odhners and parts and tinkering

Because it looked very clean and with the paintwork intact, and it was the full-featured Original Odhner Model 39 version with tens-carry in the counter, back-transfer and check-register, and wanting to experience an Original Odhner descended from what started the pinwheel-type of calculators, took a chance and got it.

It was very well packed and arrived without any mishaps. Dusty on the outside, the internal mechanism was complete and really very clean - almost like new.

Not spotted on the listing images; the calculator had a wrong, stubby replacement crank-handle and a later-pattern left clearing-crank. Minor niggles, but still. Another thing was that the back-transfer did not work reliably - with larger values the back-transfer lever would snap out of its latch and not the full digit was entered into the setting-register. (Transferring a 9 from result would get a 7 in the setting.)

After some exploring, the likely cause was wear to the latch-faces made them slide off under the pull of the (strong) spring. 

The easy fix to try was replacing with a weaker spring. Here the box-of-bits from Remington Portable typewriter EV167240 again delivered! The bell-clapper spring has similar overall dimensions, but thinner gauge wire.

This must be the 6th machine that is fixed or completed with parts from this one Remington Portable :-)

With the numbers from the result-register again transferring correct to the setting-register, the stubby (uncomfortable to use) handle seemed next. 

Just then, a clearly broken Odhner was listed on the local classifieds site - just the thing to use as a parts-donor. Contacting the seller, it turned out that more parts were available - clearing-out of a halted restoration or demo-machine project. Net result; one Odhner purchase leading to another (with correct handles included).

It all arrived in a box in many bags and little boxes - approximately 1.8 calculator :-)

A 3D puzzle - these machines are fascinating puzzles anyways. The amount of interlocks and general ingenuity is impressive. The simple handle of the main crank is even a neat trick to assemble, easy when you know it.

Loosening the screw at the bottom allows the pin to be pushed all the way in. Then the C-clip emerges from the recess in the grip and drops off the pin. The grip can then be slid off the tube on the handle. Then the pin can be retrieved the other way and the spring comes out too. To reduce play of the grip on the handle, regular thin brass M3 washers can be used under the C-clip.

This handle-pin screw was a special pac-man screw - came out fine though :)

Being distracted by so many Odhner parts, there seemed to be enough to re-build a complete model 9, dating from around 1936. Another puzzle and no qualms about experimenting to fix things.

Some shimming of the left frame for clearances and replacing the right side-frame (one was shattered) made it rotate fine and even calculate correct. The button-mechanism for the quick-clearing of the setting-levers did not work and more concerningly, the left-most wheel of the counter register did not clear. This means a broken clearing pin - as it indeed was.

Taking out the register means removing the crank. Cranks are fitted with tapered pins (awful) and require targeted violence with a hammer to remove (scary). This is well described in the section on tapered pins on John Wolff's page on repairs. This pin fortunately came out fine and the register could be taken out, numeral wheels slid off the axle and indeed one broken pin (red arrow). Someone must've really forced the handle when this numeral wheel got caught on the notch-tip, Forcing the handle round, the notch was sheared off and the machine broken - instead of a wiggle with finger-tip of the numeral wheel that would've unblocked it. Oh well.

To repair: the spot drilled out 1.6mm hole with a hand-drill and a nail driven into this hole. The notch only needs to twirl round numeral wheel, so cyanoacrylate glue should be good enough to keep it from working loose.

The nail is then sawed off and the stub filed down to shape. The exact shape and accuracy isn't even that critical; important is that the sharp, chisel-edge tip is at the correct pitch - so 7mm tip-to-tip for this one. After several repeats of re-assembling the register, testing, dis-assembling and filing a bit more - the counter-register works beautifully again on all digits. Fix.

The machine's carriage was also 'blocked'. By the 1930s Odhner was using an alloy for the carriage base that can warp or swell a little over time. This wedges the carriage stuck in its guide, and makes the machine 'broken'. With fine-grade sandpaper, the bearing-sides can however be smoothed and made to fit in the guides of the cast-iron base. After some sanding and new grease, the carriage slides without effort.

The quick-clearing on this specimen probably hadn't worked for ages. This mechanism only works with the cover mounted, the clearing-bar that pushes against the large knob is attached to the cover. A small spring-loaded stud in the drum travels over a curved bracket, to catch it and push the knob-bracket from its latch on the way back. Simple, once you've seen it work. The knob-bracket needed a lot of forming (bending) and some filing to make it clear properly and pop-back.

The counter-direction occasionally does not fully re-set but hangs (red circle); the cause is known (wear) and a solution too (file a slight extra chamfer on cam), but for now this will be left as is. Anyways, giving the crank a little wiggle before a next turn also works to prevent a hang.

As a finishing touch, a comma-bar was mounted back on the cover. Instead of rivets, now fixed with M1.2 screws and tiny hex-nuts (carefully tightened with tweezers).

Not using the quick-clearing function matches the wear of the machine - the paint is worn away exactly where the user's thumb would push back all levers, with the hand resting also on the machine back and on the crank-support of the machine. The serial number 131568 on the back-cover places this calculator somewhere around 1936.

After this tinkering detour, an extra Original Odhner. This one a model 9 pinwheel calculator that looks well used. The worn look actually suits it, so probably this machine won't be repainted or touched-up at all. It again works ok and actually runs remarkably light. 

After this distraction, got back to the model 39 and finally replaced the grip with the correct pattern from the remaining parts. On this calculator the quick-clearing must've worked fine, because there is very little wear to the paint around the setting levers and on the back.

The wear of the lever tips on the right-columns however shows that it was well-used too. It still (again) works fine now. Not quite as light-running as the worn model 9, but very shiny!

Great puzzles to explore, and amazing feats of human ingenuity :)

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