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.)

New spacebar for an Oliver 3 typewriter

The ends of the spacebar of an older Oliver typewriter are often broken off. The spacebar is made of a 'plastic' material and the ends are relatively thin and exposed. Not surprising then that the spacebar on this battered Oliver 3 was broken at both ends. Makes the machine look as if someone gnawed on it.

Only the thicker section between the pillars remains; and like the rest of the machine was slathered with black paint. And gnawed at both ends.

From the remaining 'stub' and pictures online of Oliver's that still have an intact spacebar, the dimensions were estimated and a 3D model was made. Included are pockets for the stop-buffer and threaded holes for the pillars.

This model (available on Thingiverse) was 3D printed in PLA (strong!) and painted. Unsure what the variations in color originally were; in pictures they vary between almost black to a mid-brown. This reproduction anyways painted brown (and waxed for good measure). Likely will be re-painted in a darker shade later, for now it'll do.

The pockets underneath are the buffers for the bottom-stops; originally these probably were leather. In this reproduction spacebar, rubber disks of 8 mm diameter by 2 mm thick are a press-fit. Disks of leather, furniture-felt or even simply card would also work. (Hole-punches are relatively costly, but a full set of hole-punches from 1 to 25 mm is one of the best investments in tools I ever made! These get a surprising amount of use.)

Mounted on the Oliver 3 it makes the machine looks more 'whole'. It also looks perhaps a bit too new and out of place on the battered black machine (a re-paint in olive-green may yet happen).

American National 14-20 screw thread and 7/8th Inch

The rubber 'stopper' feet of Underwood 5 typewriters are almost always 'gone'. The rubber is generally hard and the weight of the machine has compressed the foot. This is bad, not just because the rubber does not dampen any noise anymore, but also because it means the machine probably now rests on a sharp metal 'pin' on the head of the bolt that is inside the rubber 'stopper'. So; best replace with new feet.

To make new feet for an Underwood 5; a simple plastic cylinder was made to take original, salvaged bolts taken from disintegrated Underwood 5 feet. These could have been 3D-printed in rubber (TPU), but in this case printed from rigid PLA and given a pocket to take 3 or 4 mm stick-on furniture felt. The felt was given a rubber-coating for anti-slip.

These foot-bolt inserts are turned from square stock and have a ~6.15 mm threaded stud for mounting on the machine. Re-using these bolts is a good thing, because this is today an uncommon screw-thread. It's almost the same as UNC 1/4" with 20 tpi, but not quite. With tolerances of manufacture, a modern quarter-inch UNC screw may fit the machine, but it's about 0.2 mm too wide. (Outer diameter of UNC 1/4" is 0.250" (obviously) and #14 diameter is 0.242".)

An Underwood 5 has American N 14-20 threaded holes for mounting the feet; this thread was removed from ASME standards already in the 1940s. This used to be a fairly common screw size as I've read. To add to the diversity of threads, it exists both as 14-20 and 14-24 (i.e. 24 threads per inch). In either case, today nearly unobtainable. 

So it's a good thing to re-use the original bolt-inserts of the old, original feet if possible.

Sizing of the feet themselves is a guess - estimating from the remains of the old feet, chose a diameter of 20 mm (25/32 inch ?). On photographic evidence of the 1920s the feet do look similarly thin and cylindrical, but not quite as thin as all that.

Giving it some thought, a diameter of 7/8" is more likely. As we're 'anoraking' anyways and these being easily printed; manufactured a new set with the larger 7/8" diameter.

These look a bit more substantial - and less ridiculously flimsy on the machine. Now the Underwood 5 typewriter with new cylindrical feet that are probably similar to the original when-new feet. 

It remains to be seen how well these feet hold up over the years. The PLA material is very strong at room-temperatures, but will weaken when hot. At temperatures over 60 degrees C they will probably slowly 'collapse' and be squished (actually, just like the original feet did! Very authentic :-). That's where the felt-pads come in, they will prevent the bolts from protruding and scratching the table.

For now, this common Underwood is on a stable footing again. And with the cushioning felt, also much quieter on the table! :)

What are front left foot numbers on an Underwood 5 ?

The Underwood 5 typewriter has the serial number stamped on the frame-top near the right spool. The number itself is generally followed by a type-designation, so the pattern is xxxxxx-5 for a regular Nr. 5. The number is on a flat, machined surface and linear - feasible to stamp with an automatic numbering stamp.

Here the Underwood 5 serial number on a 1920 machine (type "5" on the extra face/facet):

Probably on every Underwood 5 (or 4, 3, 46T etc.) there is another number stamped into the frame. This number is stamped in the flat, machined surface under the front left foot. The digits are arranged around the screw-hole for the foot, to fit in the area. This makes it less likely to have been an automatically incrementing numbering stamp, but more likely hand-stamped. 

Here the extra "front left foot number" on that same 1920 machine:

Another example; here the front-left foot and the top-right of the frame in one picture:

(Yes, it's in pieces. This Underwood was completely broken; dropped/tumbled onto a concrete floor from some height. The cast iron frame was shattered and all panels crumpled. The wreck is being salvaged for parts to fix other machines.)

From these and a few other machines, e.g. on The Database or mentioned on the net, some serial numbers with their front left foot numbers can be found. 

  serial number    year    front left foot number

        475,051    1912          541,824

        734,809    1914          874,286

      1,411,885    1920        1,812,200

      1,872,237    1924        2,461,255

      2,446,801    1928          389,092

      3,677,613    1930          111,938           (46T)

Can't help but wonder; what are these numbers? 

They don't look to contain dates. They do not correlate with the machine serial numbers. Come to that; are they actually serialised, another serial number range for the foundry? They are not all incrementing. 

Are they perhaps job-numbers; per order of a batch of finished-frames so that several machines within a range of serial numbers will have the same front left foot number?

Could the "24" on that 1924 machine be a year prefix to a job-number? But that wouldn't explain the "18" on the 1920 machine (late 1920, November-ish).

Update!: 

If the last two numbers are ignored, the range is actually nicely incrementing. That could be reasoned e.g. when the '28 and '30 numbers are after a change in the method. (E.g. restart at zero every year), after the number started to become cumbersome to stamp in the mid 1920s. Then the serial and left foot numbers correlate very well - they have a linear relation:

Left foot numbers rise 1.38 times the speed of serials. That could indicate that not all casting numbers are for machine frames - about 73% of stamped parts would be for Underwood 5 typewriter frames. The practice of stamping the casings would have started around Underwood 5 machine serial number 100,000 - about 1906. (Could be checked, will a pre-1906 machine have a front left foot number?) 

Could be that for the Underwood 5 the left foot numbers rise at 1.38 times the serials (i.e. take up 73%), because the other 27% is on other machines, such as 3's or 4's. Some serial and front left foot numbers of Nr. 4 machines could confirm or disprove that.  

Even so, most likely explanation is that these foot numbers are sequential serial numbering from the casting finishing-shop.

More insight, still curious :-)

Another update/addition:

As Mr Polt pointed out, there's also a number on the carriage-frame. On the 1920 Underwood 5 also pictured above, this right-side of the carriage frame number is identical to the foot number. On my 1928 machine it's different - but that was at first-sight. On further looking at the numbers, it's actually very informative :)

On the 1924 machine the carriage number was by the way also identical to the foot number 2,461,255.

On the 1928 machine however the carriage number is 3,389,092. The foot number is 389,092 - i.e. the foot-number is the last 6 digits of the carriage number. Ergo, let's assume that the foot number in full should be read as 3,389,092 too.

Extrapolating, the 111,938 of the 1930 machine is likely the last 6 digits of full machine-frame number 5,111,938.

When adding these extrapolated numbers to the graph, the linear relation holds very well!:

The R-squared goes down a tiny bit; suggesting that the proportions of different machine-types were shifting a little after the mid 1920s. I.e. less constant proportion of ~73% of Underwood 5 in the factory output.

On this still limited data, the theory would be that the carriage number is the same as the foot-number. 

This also gives a theory on the reason for stamping these numbers. The numbers being 'hidden' indicates they are only for use by Underwood in manufacture. The visible serial-number is the one that's intended for unique identification of the machine by trade and customers.

If the number was only on the frame, it could for example have been to track some measurements on paper that were needed for later assembly (stamping costs money, would have needed a reason). 

Now that the same numbers are on both frame and carriage, a plausible new theory is that they're simply for enabling (re-)matching carriage and machine-base. That would also make re-starting the numbers every year or indeed only stamping the last 6 digits not a problem (and saving a bit of money). (I.e. the purpose similar to the serials on K&E mahogany sliderules; serials rolling-over every decade or so was fine because they were created mainly to be able to re-match tongue and rule during manufacture.)

More data is indeed more insight and better theory on what and why - and still curious :-)