Manufacturing process for a new Blickensderfer type wheel 407

How to make a new type wheel for the Blickensderfer; in this case a reproduction 'Small Roman' type wheel catalogue number 407, codename 'Table'.

To start with, take a 3D-model of the type wheel. This 3D-model is designed for 3D printing in PLA material on an FDM printer. The overhang-angles and outer contour are designed for the FDM process with a small nozzle (0.2 mm) and best printed with a fine layer-height of ~0.080 mm. The model does not require any supports.

The 3D model can be downloaded here.

After printing, the wheel needs some finishing to be usable - the top 'stub' that holds the spring-clip is far too weak to withstand any use and the important surfaces will need fine-tuning. The tools needed for this are a round file (small, ~3mm diameter), cyanoacrylate glue, a toothpick and a bit of scrap card.

To strengthen the stub on top, place a drop of cyanoacrylate on the toothpick and bring it to where the stub meets the top-plane. Cyanoacrylate will fill remaining gaps between the deposited filament layers. Use the toothpick to bring the drop all-around the stub, also in the corners of the spring-clip notch. Use the scrap-card to absorb any excess and wipe clean/flat the cyanoacrylate over the top face of the wheel. Then give the part a few hours, say 10, to let the cyanoacrylate set - do not disturb during hardening.

Any stringing or z-seam artefacts on the bearing-surfaces in the central hole can then be made smooth with the round file. The mounting-rod on the typewriter is ~ 3.2 mm diameter, the type wheel should fit on this rod without any friction and ideally without play. Any friction when rotating on the rod will cause the Blickensderfer to 'jam' or cause the typing-head to not come back up completely after a keypress.

Any cyanoacrylate that got into the central hole can also be filed away after setting. In case a hole turns out to be too large, an even application of some cyanoacrylate with the toothpick round the inner-surface can again reduce the diameter a fraction of a mm. A thin application of cyanoacrylate on the inner-surface of the central hole may be good anyways - it gives it a very hard and low-friction surface compared to plain PLA.

In case the square take-up hole is too tight, it can be filed wider. Note that the actual dimension of a printed part can vary slightly per individual 3D printer and also per filament used (and the condition, how well dried etc.) 

The spring-clip that fixes the wheel in-position can be formed from spring-steel wire of 0.020 gauge (approximately 0.5mm diameter). E.g. plain-steel guitar-string of 0.020 gauge is a good source of a practical length of suitable wire.

A few nails driven in a scrap bit of wood serves as a jig to create several clips. As always, taking care with springy wire that has sharp ends. Small pliers help to bend a new clip into shape.

The spring-clip is simply snapped on the stub - and the new type wheel is ready to be used on the Blickensderfer! 

The machine can now be typed on without fear of damaging an original vulcanite type wheel, even with rock-hard platen. An extra backing-sheet is a good idea anyways, also helps with the quality of the impression.

* Note that when actually using a Blickensderfer, it quickly becomes obvious that type wheels get covered in ink - especially the top where the ink-roller is pushed to when the type hits the paper. This makes swapping typefaces without getting ink all over your fingers tricky. Best to use a patch of tissue or waxed-paper to handle a type wheel when putting it on or taking it off the typewriter -and to wrap it in when stored in its wooden box.

* Note that on original vulcanite type wheels, the central tube is brass. It is a brass tube of ~4 mm with a ~3.4 mm (?) hole that is the wheel's bearing/mounting on the machine. This reproduction is all-plastic, but of course a reproduction could be designed to take a brass tube with a machined slot for the holding-clip.

* Note that the alignment of characters is from their position on the type wheel, so should be good. However, any play of the type-wheel on the shaft or with the take-up vane will result in alignment deviations. Also a loose or badly-fitting spring-clip can cause alignment irregularities.

* Note that the FDM printing process is not as high-resolution as a DLP resin-printing process would be, but it is good enough for typing and the material is much stronger and impact-resistant than a resin print. Another benefit is that FDM prints are much easier/cheaper to make - less hassle with unpleasant chemicals and this part should take about 4.6 grammes of PLA. For FDM process, the PLA material is a good one - compared to e.g. ABS or PET it is easier and usually gives a superior surface finish.

* Note that the baselines of the three rows of text do not seem to have an immediately obvious spacing. It is not like e.g. the Mignon that is spaced in tenths of an Inch (i.e. 2/10ths between rows). Comparing test-wheels with the typing from original wheels, the three rows baselines were set at experimentally derived distances from the top-face of the wheel. The current values seemed to work fine, but may not be correct or optimal for all Blickensderfer machines.

Excavating (or destroying?) a layer of history on a machine

This particular Underwood 5 was bought locally, originally meant as a reference machine to help with the restoration of an older 1920 Underwood 5.

This machine was not only a newer 1928 version, it also showed evidence that it was refurbished and put to use in a later, very specific time-period in the British Isles. In archeological terms; it had acquired a 'layer of deposits'.

Taken off the machine and replaced with 'nicer' specimens. The knobs were replaced with Underwood knobs - albeit later, larger-diameter pattern. The green ruler and especially the wrong-pattern knob on the Underwood were 'jarring'.

The modifications are in principle all reversible; the removed parts are kept. But realistically, this machine viewed as a historical artefact has entered a new phase; 21st century collectable (though not rare). 

Sticking with the 'archeological' viewpoint - this removal of a layer has now, hereby been documented :-)

One mystery part - mildly disconcerting

After taking it apart and putting it back together, one spring that won't fit anywhere. 

This Blickensderfer 7 was also one key-lever spring short. The odd thing is, that the remaining spring will not work as a key-lever spring; it's the wrong shape and simply won't fit. In the end, a new replacement key-lever spring was formed out of piano-wire. This new spring is a great fit, in fact can't tell it apart from the originals, and all 28 levers are held up properly. But the left-over spring is a worry - no idea where it came from.

All 28 key-levers have their spring to keep them in the up position. In the middle of the machine then the two springs that work the left and right rotation-bars, these springs have a proper loop to go on studs. And finally there is one thicker spring to go on the universal bar.

Couldn't fit the mystery spring on any key-lever, just couldn't make it fit. 

Maybe later I'll discover how it can fit a special key-lever that needs it - maybe it simply was a 'wrong' replacement during servicing long ago. Or a 'whim' at assembly of the machine, even longer ago.

The other thing is that this Blickensderfer works flawlessly without this mystery spring. 

mildly disconcerting

:)

Swapping-out cellulose acetate keys on a Comptometer

To start, five columns of white keys for a Comptometer.

These are genuine, old keys. Not new reproductions, but relatively good originals. They do have some yellowing and have started to deform, but still very serviceable. These keys were harvested from a ~1930 Comptometer Model J with severe rust and -oddly- loss of many of the green keys.

 

Usually it is the white keys that degrade instead of the green. That's because the white keys did not have enough colorant in them to act as antacid to halt the decay of the cellulose acetate.

This very common 'key-rot' on Comptometer Model J machines was introduced by changing the keys material from cellulose-nitrate to cellulose-acetate. It would have seemed a sensible idea to change to this new material - just as film moved from cellulose-nitrate to cellulose-acetate (i.e. safety-film; not as flammable as the nitrate!). 

This change could have been fine. However, the unfortunate (in hindsight) choice was to also change from the completely opaque white nitrate keys to a slightly translucent white. This likely looked great and 'gem-like' when new and perhaps made the keys a bit cheaper, but with too little zinc-oxide the cellulose-acetate mass remained slightly acid. Then the acetate starts to degrade, adding more acetic acid (vinegar) to stimulate further decay. The acetic acid can even 'sweat' out of the key and then mingles with the (wax?) lettering, making it look like the lettering just oozes off the key. It also makes them sticky (yuck).

The green keys on Model J machines are fully opaque; i.e. seem to have much more pigment and these are generally fine. It is quite unusual for green keys to also have crumbled. The white keys all being fine on this machine suggests that these were already a replacement set, probably fitted sometime in the 1940s.

The replacing of keys requires removal of the entire key-stem. Removing keys-with-stem from a Comptometer in the usual manner. Then using a slotted wood-block and hammer to tap the key from the stem, as it is held in a vise. 

Replaced the keys one column at a time - not removing all stems from a column at once, to make re-fitting a bit easier. (Otherwise it can be tricky to ensure all the levers and rods go at their correct side of the stem.)

The right-most column with the new keys, the contrast with the raisin-like old keys is noticeable. After replacing the keytops on all the white (well, cream) columns, the Comptometer Supertotaliser looks much better.

At then end of this procedure and having done another machine earlier; we now have a jumble box of Comptometer keys in varying states of degradation. From almost ivory white to deep-brown.

Two of the green keys on the machine (circled in red) are already shrunk more than the rest; so a hunt through the box to find a potential replacement. There actually is a quite a bit of color variation in the green; the best quality 4-key is a distinctly different shade of green (dotted circle). For now, all green keys were left on the machine In case the keys really do fail in the future, there are some ok-replacements (circled white) in the box. 

As a final small step, the large engraved numbers '6' were removed from the typeplate. Or rather, the rusty keytop-donor Model J had exactly the same version of typeplate, so these were exchanged.

(Note that replacing typeplates on these machines carries a risk - the screws go into a threaded washer that is lodged in the cork-lining of the top-plate. If this washer should be pushed loose or lets go, it drops away into the mechanism and all keys need to be removed to take-off the top-plate to recover the washer and be able to re-fit the typeplate.)