Blickensderfer platen testing, hardnesses

The platen of a Blickensderfer is a bit different from most typewriter platens, in that it has threaded rod-ends instead of a through platen rod. Also unusual is that its rubber surfacing is edged with metal side plates and it has a recessed diameter section for the line-ruler to run in.

The platen of a Blickensderfer is invariably rock hard. Even though the metal end plates and the recess make it a bit more tricky, Blick platens can be professionally re-surfaced for sure. Before perhaps doing that, first wanted to do some testing with new reproduction platens.

Wanted to find out if platen hardness has a noticeable impact on writing and if so; what hardness works well for the Blickensderfer. (The Blickensderfer with 'pressing down' of a Vulcanite type onto the paper is a different process than a typebar slamming a metal type onto the paper -and may have different requirements on platen.)

Using steel threaded rod as the basis, a new replacement platen construction was designed to allow different surfaces/sleeves to be tested. The two componenst that make up the 'core' are 3D printed in PLA - that is a very strong material at room temperature. Brass bushings cut from 4.5 mm OD by 4 mm ID tube form the bearings. For the threaded rod, M4 was used. It should be American 8-32 thread; this is still common and widely available in the US, but simply cannot be had elsewhere. M4 is a close match and will take 8-32 nuts.

The two component parts of the core, the main (green) and cap (pink), have threaded sections near the sides. The thread could be printed, but cutting makes for a cleaner and stronger thread in the plastic.

The threaded rod length is 268 mm with a hole of about 2 mm diameter drilled through at 27 mm from one end. This rod is screwed into the main core part to stick out from the flange-side about 8mm. A brass bush is then inserted, leaving a length of 3 mm sticking out. A small drop of cyanoacrylate glue on where the bush goes into the core will fix it in place.

The smaller core part, the 'cap', is also tapped and the brass bush inserted, leaving about 5.5 mm sticking out. With the sleeve and a nail, the new platen can be assembled.

The typing surface is a sleeve of rubbery material, i.e. a 3D printed tube from TPU of varying grades. The nail through the rod is used to positively lock the rod against rotating in the core. This way the plastic thread only needs to lock against sliding left-right and will not be loaded from rotating the platen. (Normal paper feeding could be fine, but e.g. when straightening paper by rotating the platen whilst holding the sheet the load on the rod is much larger than what a plastic thread could take.)

The brass bushes form the bearings of the platen in the carriage brackets (holes of about 4.8 mm). The core is held only at the threaded sections at both ends. Over most of the platen width, the threaded rod is free inside a larger hole, only loaded near the ends. In section mid-width, the new reproduction platen looks like this:

When the sleeve is over the core, the nail is locked in place. The right-hand 'cap' fixes everything in place with friction on the ends of the rubber sleeve. Everything can still be taken apart again. However, to eliminate any remaining rotation-play between rod and core, a drop of cyanoacrylate can be dropped into the nail-hole. The rod is then permanently fixed in the main core-component, but sleeves can still be exchanged.

Using the above construction a set of new, replacement Blickensderfer platens was made:

From left to right
 - an original rock-hard platen,
 - new TPU Shore 98
 - new TPU Shore 95
 - new TPU Shore 90
 - new saturated cork

Note that even though the TPU rubber platens look credible (from a distance), they require a lot of work to remove or lessen printing artefacts. There are of course the lines from the stacked layers of material, with 0.15 mm pitch this is not too bad and easy to mitigate.

Flexing is however a bigger issue. Because the material is rubbery, the part starts to flex under the printing-head drag as it gets taller. This means that towards one end the surface becomes less defined - it is rough, wavey. Another hard-to-avoid artefact is a bulge from the z-step of the printer, this will need to be filed away. (TPU does not like filing.)

After the artefacts have been mitigated a surface layer of black paint is applied plus a fine sanding to finish. This way a reasonably smooth, cylindrical surface can be achieved. It is nowhere near the quality of a professionally re-surfaced platen, but good enough for a typing surface -and testing.

Exchanging the platen on a Blickensderfer is unfortunately a bit involved. The left carriage bracket has to be taken off and the linespacing mechanism on the right-side of the platen also has to be removed. There are also washers to be placed back in the right order. (Note that one washer between right-flange of the platen and the carriage bracket.)

Testing the new platens, the results varied.

The cork platen worked, but only when taking care and typing very lightly. A press that is only a little too hard would cause adjacent characters to smudge the paper. It is too soft for typing, even on a Blickensderfer (as others have noted too). Making a platen with cork probably is possible, but will require extra infusing of the cork and stiffening of the outer surface. 

The Shore 98 platen is almost as hard as the original. It may be TPU, but there is hardly any trace of resilience left. Finger-nail test fail. Also in writing with it on the machine there is no difference with the original rock-hard rubber platen.

The Shore 95 platen feels very stiff, but definitely is resilient. The Blickensderfer types quite well with the 95 platen, a noticable difference with the hard, original platen!

Also with the more legible typeface of a wheel 407 it types quite well. And less worry about the wear on an original typewheel, because the surface does conform. I.e. it passes the finger-nail test.

The Shore 90 platen felt very rubbery resilient, yet still firm. It is clearly softer than the 95 platen, just going by finger-nail measuring. The typing on this platen however was much less distinct than on the Shore 95 surface. That was not expected, this nicely rubbery surface was expected to be best for writing with the Blickensderfer.

Quickly swapping back to the Shore 95 TPU platen, this looks the most promising sleeve material hardness.

Outcome of the testing, answers to the questions!;
  - yes, new rubber does make a difference for typing. 
  - Shore 95 TPU is a good hardness.

There are still many details to be worked out on e.g. exact diameter of the sleeve, thickness of the sleeve itself and method of surface finishing. Things can be further optimized, e.g. the clunky nail-locking could perhaps be re-designed with captive steel nuts to take the torque. Another new platen knob with proper M4 thread perhaps to be made. And perhaps invest in importing a UNC 8-32 threaded rod all the way across the ocean :-)

Regardless, already a better typing Blickensderfer! 

Blickensderfer tweaking and starting on platens

The Blickensderfer 5 typewriter is a brilliant machine. It also has an almost endless set of adjustments to make it work. One of the issues that remained was an imperfect printing of the 'z' character. This I'd attributed to some remaining tuning of the typewheel rotation-stops or something wrong with my new typewheels.

Not so.

When the letters 'z' or 'j' do not print well (i.e. the most-rotated characters), then the ink-roller needs to be adjusted down. Imperfect or faint printing was caused by the ink-roller being too high; the roller had already passed over the wheel when the rotation to the correct letter had not been complete. I.e. the 'z' as a largest-rotation character would not get properly inked. 

The ink-roller arm is fortunately easily moved - one screw (the obvious one in above photo) holds the bracket and it can be moved up or down to find a spot where it all works best.

Similarly the forked bracket that holds down the paper has an adjustment; a screw on the front-face of the right 'leg' of the top-casting. When the fork is adjusted so that it hovers horizontally just above the sheet, it works wonders in keeping the sheet in place to get clean printing! (Otherwise the paper can lift and characters get smudged a bit until the sheet is held under the rear bail.)

These adjustments were found during first testing of alternative, new platens for the Blickensderfer. The original is rock-hard, as they almost always are. Don't yet dare to send it off for re-covering professionally, so first trying to cobble-up some test-platens to see if it can make a difference. And to find out what hardness a Blickensderfer likes.

This above line was typed using a fairly crudely made cork platen. The cork sourced from cutting up a 'placemat' and wound round a newly made core. The cork itself is much too soft, so first spray-lacquered. The cork absorbs the first few lacquer aplications, adding strength and stiffness. Then a layer of PVA 'painted' over the surface to add more stiffness and close the surface, to fill remaining 'potholes'. The whole surface then lightly sanded with very fine grit. This brought the cork-platen into the workable range of hardness, and not too grippy.

It works!, but still on the soft side of the practical working window. More test platens to be constructed and more methods of cobbling together a resilient platen surface to be tried (without a lathe :)

Project! :-D

Marchant Pony B calculator typeplate reproduction

The Pony B calculator was missing the distinctive Marchant brass nameplate.  As this is a very visible part of the 'look' of a Marchant of that period, a reproduction was attempted.

Even though not an exact replica, a good lookalike nameplate could be drawn. The recreated design then to be implemented in relief. This should of course be brass (etching?), but noit having the chemicals and kit for etching some simpler methods were tried.

The Old English typeface is not an exact match for the originals. From browsing Marchant advertisiments of the period and some other publications however, the company itself was also not that strict on the exact typeface for the wordmark.

A while ago, had tried pressing soft paperboard into a mold to create a textured surface. This had worked well to re-create the missing sides of the pouch for a Golden Gem adding machine.

With the image flipped mirror-image, a mold was 3D printed. Half mm paperboard was soaked in hot water and then pressed against the mold. A clamp and bits of wood to distribute the force.

Left for several hours to allow the paperboard time to dry via the sides. Then opening the mold, there is a fairly crisp impression of the mold. It even showed the 3D printing artefacts; the diagoinal lines of the filament-path.

Experimenting with the 3D printing parameters/orientation and some sanding of the molds, the artefacts can be reduced. The cards are immediately fixated with spray-lacquer when they are taken out of the mold, dried. The paperboard is best placed on a curved surface (jam-jar) held in palce with masking tape. The lacquer permeates the paperboard, making a surprisingly stiff and strong part. 

After first fixating, the parts are cut to size and the four riveting holes are punched out. As final make-believe step, they are given a brassy finish.

The results with this method were very crisp, however the relief fairly shallow. The photographs of genuine Marchant machines show that the lettering is quite deep. The paperboard is also prone to warping.

To try a different method to get deeper lettering, also direct 3D printing of the typeplate was tried. The part is  printed flat and then placed over a curved surface (that jam-jar). With a hairdryer they are then softened and settled in the curve needed. A few variations were tested, with different printing parameters and thicknesses. The part then finished with a brassy finish.

These plastic direct-printed typeplates looked very similar to the originals in pictures found online.

A couple of these plates were made - these use almost no material, are very fast prints - and finished with different hues of 'brass'.

Some judging next to the genuinely brass dealer-plate to select a colour that is not too jarring on the machine.

Then fitted on the cover. Not with rivets, but with tiny hex-nuts and domed-bolts.

Very bright. It won't tarnish like the dealer-plate, so later it may be swapped for a darker fake-brass to stay in-range with the dealer-plate.

Another possible method could be to press thin brass sheet (possibly with paperboard backing) into the mold - that would give the correct material. Unsure if that'd give the desired depth of lettering, even with proper glowing of the brass. Perhaps something for a next project.

The Pony B may not work all that great, but it is a 'decorative' machine - on display for now :-)

Marchant Pony B calculator continued tinkering

After refurbishing a Model B Comptometer and playing with the Blickensderfer, returning to the Marchant Pony B Special calculator. The Pony B still had issues.

The reason for originally buying a Marchant Pony was to experience what these were like, it was local and they're rare hereabouts. They've been described as very light, and was curious how an American-made pinwheel machine would be. Unfortunately the machine was seriously damaged, and only after getting a parts-machine was it possible to try a repair.

Though it now looks complete and mostly worked, it still occasionally blocked. It'd block hard - not just more resistance, but no way that a turn could be completed, the only way out is to reverse the handle. (That would explain why on machines the full-turn pawl is missing or the back-plate removed, not statistically significant and all that, but from looking round online this seems common on these Marchants.)

The first hypothesis was that one of the short-ish pins in a carry-lever would sometimes jam. To test/fix this, the pins of suspected levers were replaced with long pins. From having a donor-machine, there's an assortment of springs and pins to choose from :)

By driving in a rod from the right pushing the gears axle, only one lever can be carefully released (hold something over hole, to prevent pin shooting out and get lost inside the carriage). Then the lever with replaced spring and pin can be moved back in-line and the axle pushed back in place.

That did not solve the problem of randomly blocking on a carry.

Observing the blocked machine with covers removed, it turned out that the carry-lever was actually stopped by the adjacent dial of the drum. 

The replacement drum-axle is of slightly different dimensions than the original and the drum is a few tenths of a mm too far to the right, relative to the carriage position. These Marchant calculators are truly a feast of interdependent adjustments. Finicky.

After trying to fix it with washers, ultimately swapped the original drum-axle back in. (Washers fixed the blocking, but created new issues with the clearing-lever. Plus the donor-axle had a broken full-turn gear.) 

Replacing the main axle and keeping the donor-handle meant that the gears of drum and handle-axle were now off. To mitigate that, decided to 'cheat' and change the handle position on the rod. The pin is now merely decorative and the fixing is with cyanoacrylate. Of course, the drum needed to be taken out (and apart) and thus the right sideplate needed to come off and because the locating-pins are missing the whole machine then needs tweaking to run freely.

 

Having the covers off, had another look at the interlock of carriage-clearing. This does not work. Looking at the pin that is pushed out of the carriage-frame when clearing, it is hard to see how it could have worked when new.

This is the original carriage, all parts are for this machine. Yet clearing simply doesn't push out the pin anywhere far enough to reach the dimples in the extra horizontal rod on the machine base. Can't see anything that could be adjusted, this is entirely from dimensions of the parts. We'll accept this interlock doesn't work - just take care to not clear and turn at the same time :)

Because the blocking problem is solved, now daring to fit the full-turn or anti-reverse mechanism. Trying to move the parts of the 1919 donor-machine over to the 1920 machine it turns out that the screw-threads are different! Both the lock-screw and the shoulder-bolt have different threads! (Why?? I'd now really like to talk with the Marchant factory design office of 1919.)

By shortening the shoulder-bolt, a lot of careful filing of threads and an extra washer, the full-turn lever is in-place.

After this extra round of fixing (attempts) the calculator still 'mostly works'. It is ok on addition and reasonably light in operation, but it is not smooth. Some carries in subtraction need work. It also is fairly noisy; the full-turn lever makes a ratchety clinkety-click as it dances over its gear. This maybe was another reason to remove this part in the past, it adds an annoying tinkle.

The clearing-nut for the setting register started to work - partially. It also is a mystifying mechanism - can't make sense of it.

The check-wheels are geared with the setting-dials via intermediate gears. When the handle is pulled out, the intermediate gears are shifted to the left to allow the drum to rotate and check wheels to remain static. The check wheels are held by a spring-loaded ratchet in a valid 'digit' position, nevertheless an extra hard-lock is engaged when the lever is pulled. In below photo the slotted bar is holding the intermediate gears, positively blocking any rotation.

When the handle is back in the rest position, the intermediate gears are back in engagement with the setting dials and the gear teeth now run through the slots in the locking-beam - below photo.

Adjusting the positions of all these shifting axles is finicky, any wear or deforming can block things. The scratches on one check wheel suggest that it had blocked and a violent attempt was made to get it moving again. (Forcing a wheel was a bad idea - wiggling the setting level can already help. Turning the clearing nut while at the same time pulling-out the main crank will unblock the lock-bar and set all check wheels to zero. That is also the way to re-sync the drum and chek wheels if they ever get out of sync.)

The locking-bar arrangement seems a bit over-complicated and superfluous - the machine should work fine also without this extra lock, the sprung ratchets will hold the digit. Another thing that is perplexing me still is that during clearing the lock-bar is shifted to the left as well - and then the intermediate gears need a nudge to the left too. The intermediate gears however also need to remain in engagement with the setting dials. This adds to the complexity of finding all the right adjustments, so many more ways for the mechanism to fail and block! 

With the machine at-rest, the intermediate gear should engage the setting dial, but must not foul the path of the pins. I.e. must be in-line, see below photo:

When clearing the drum with the wingnut via the check wheels, the intermediate gear must shift slightly to the left - just enough to remain clear of the left-shifting lock bar. But the gear must also remain in engagement with the setting dial. See below photo:

Frankly, the reasons for this complexity is not clear to me - plus that the way it is engineered makes the design 'brittle'.

After many attempts of adjusting, it now works - mostly. The column 7 and 9 do not clear, the pins on the axle must have been sheared off (again evidence that violence was applied in the past to a blocked check register). This whole mechanism is fixed with pinned collars - have not been able to remove any of the steel pins in the brass collars. Drilling out is an option, but so far that's deemed too much effort for this 'rough' machine.

The calculator assembled back together again after this round of explorations. Has to be admitted that it still looks better than that it actually works.

Even though this Marchant is not a representative experience of what these were originally like, it has given a much better understanding of how these calculators work. Also of how the Marchant factory operated and how their design evolved - the impression frankly is of two design cultures. There is the solid 'core' of the original Odher machine essentially unchanged, and then bolted on are the convoluted constructions of e.g. the carriage movement or the check wheel register.

During the 1917 to 1922-ish period Marchant would have sold every calculator they made so it may not have mattered all that much, but the impression is that they were not at 'world class' level of engineering competence for calculators.  In 1920 not yet, anyways.

This machine purchase is definitely delivering on the goal of experiencing the Marchant Pony! Oh and the Pony B still has issues :)

Blickensderfer Blackletter (blue fingers)

Starting with typewheel 407...

....and then swapped to a Blackletter wheel.

To make it easier to see how the ink is spread over a typewheel, swapping in a white typewheel:

It needs 'wetting' for the first characters, but then starts to be properly inked and type:

On a white wheel the blue ink clearly shows up.

The pattern of ink on the wheel nicely illustrates the Blickensderfer scientific layout; the most inked are the most frequently used letters that have the smallest rotation of the wheel.

This Blickensderfer 7 now back to the black wheel - it perhaps makes sense that Blickensderfer wheels were black, even if only for appearances sake :)

Model B - final step, all assembled

With all the bits cleaned, it's fairly quick and straightforward to put the Comptometer model B mechanism into the case again.

The photo exagerates the whiteness of the keys, they are still fairly grey in reality. The machine however really does look much better than it did:

It still shows signs of its age, with old repairs and old (and new!) refurbishments.

The '3' keys of columns 3 and 4 are not original, but are 1920s replacements. These keys may yet be replaced by new reproductions that are closer match for the composite keys of a model B. These celluloid replacements are however also 'original' and likely a century old themsevles - they are of Felt & Tarrant manufacture and an example of normal repairs that would have happened over the machine's lifetime. 

(The likely reason for these replacements could be seen on the remaining black 3-key. The composite material has ground stone (mica?) mixed with the resin; the black 3-key showed that cracks were starting where porous particles were embedded. It looked like the batch of 3-keys had too-large particles (sawdust?) embedded that weakened the part.)

Also the typeplate is a later, probably 1930s, replacement. It shows a 1921 patent number (for features not on this machine) and looks to be chrome, not nickel. It also shows this is a French machine, exported and sold in France.

Below found image of Comptometer 30680 shows what the original plate would have been, with a 1904 patent as most recent. 

These plates were however already often replaced for export machines, or swapped by the importer, with a localised typelate. Dutch machines often got a neutral plate without patent numbers, with text either in English or in Dutch. In the collection of Comptometers here, one ~1921 model H had just such a plate.

Because the French patent 528,226 of 1921 actually does describe the improved clearing mechanism of the H and would be correct for it, the plates were swapped out between the two machines. (No longer 'original state' now, but the B's plate wasn't original already. Fitting new/different plates and panels was routine during refurbishment of Comptometers, judging the configurations of several observed machines.)

This particular Compptometer was used; the holes for the keystems do have wear. Especially the colum 2 had a lot of 9's entered.

Placing the model B (left) next to a model C-light (right) shows some of the changes made, their development path of Felt & Tarrant. The keys were of course changed from composite to celluloid with a slightly different design and different front panel mounting.

Internally the very noisy B clearing mechanism was completely re-designed in the C (light) and more oiling holes were added to the case (lots of them).

Also an unexpected, small difference is in the subtraction cut-off tabs. On the B they are bent to the right, whereas on the C they are bent to the left. This probably make sense, an improvement - it visually links the tab more obviously to the column it is blocking the carry of.

On a model B the serial number is on the front panel between columns 4 and 5. This model B has serial number 30639 that places manufacture around 1908.

Thinking about that, 1908 is actually quite a long time ago.

Ladies at the Longchamp Hippodrome, Paris, 1908

Looking at it again, it is neat to be able to own and operate such a machine, calculating fine at well over a century old!