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Author Topic: Restoring yet another antique Teletype machine  (Read 21982 times)
Prof Thadeus Q. Wychlock
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« Reply #25 on: September 04, 2014, 06:00:49 pm »

oldskoolpunk ....

am i correct in assuming that comms between devices now uses the aetherweb?
and therefore ....
were there to be a teletype machine connected to the aetherweb in the UK, message could be sent between the two ??

 Grin
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« Reply #26 on: September 04, 2014, 08:51:25 pm »

It makes me cringe to see that TTY called antique. The guy on the next bench fixed them, while I was fixing radios in the army.
This is a model designed in the 1920s and first produced in 1930. It's not that far from the steam era. A huge number of these machines were made for the military during WWII, and they were used well into the 1960s, and in some places later.
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« Reply #27 on: September 06, 2014, 06:29:36 am »

More progress today. Fully disassembled the main shaft. One clutch was so stuck that I had to use Locktite Fast Acting Corrosion Freeze and Release spray, which is not fun stuff.  (A reason to wear gloves and goggles, though.) All the main shaft parts are now cleaned, shiny, slide smoothly where they should, and sit in a little compartmented box in order of reassembly. This is what gear-driven technology is like.

Tomorrow, main shaft reassembly.

(Am I encouraging or discouraging people? Let me know.)
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« Reply #28 on: September 06, 2014, 07:01:36 am »

Enlightening people is what you are doing!
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« Reply #29 on: September 06, 2014, 05:29:18 pm »

Remember when radio stations used to play a recording of a teletype during newscasts?
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oldskoolpunk
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« Reply #30 on: September 06, 2014, 08:43:53 pm »


The main shaft components. A Place for Everything, and Everything in its Place. Reassembly starts from the lower left.

Getting all these off the shaft was difficult. They're supposed to just slide off. The subassembly at 2 down and 3 across took hours to get apart without damaging it. I had to use Locktite Freeze and Release Spray to get some of them apart. Once apart, each part gets cleaned and polished.

Several parts slide sideways on the shaft; those are the ones pushed by springs. That's how the clutches work. This isn't just a set of cams and gears.


Main shaft reassembly.

All the parts are back in their proper place. Everything that's supposed to slide now slides. The design is mechanic-friendly; if something is put on backwards or not engaged properly with the previous part, the stack will be too thick and the next locknut won't go on. Everything that needs angular alignment is self-aligning. As long as you put the right parts on in the right order, it goes together properly. After you've done it once, it's an easy job for a unit that hasn't been neglected. On heavily used machines, it was done once a year, and worn parts replaced if necessary.

Well-designed mechanisms which need field maintenance go together like that. Today, other than guns and military systems, that's not a major design consideration. The military is big on this. When I was in aerospace, a poster on design read: "When you have to fix it, it will be too hot or too cold, probably raining, and someone may be shooting at you."

It's a classic property of early 20th century American auto engineering, where it prevents parts being put together wrong on the assembly line. It's notoriously not a property of British designs, which were famous for being able to be put together with parts backwards. (There's a long discussion of this subject in "The Business of Tanks", which is a WWII book by the British representative for tank production who spent WWII in Detroit working on the Sherman tank project. His big contribution was pushing through a bigger gun for the Sherman; British combat experience indicated that more firepower was needed.)

There's a philosophy of mechanical design. Steampunk authors should get this. It adds verisimilitude to the story. Machinery is parts working together, not magic.

(They look like parts from a steampunk weapon, don't they?)
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oldskoolpunk
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« Reply #31 on: September 12, 2014, 12:51:10 am »

Further progress.


Main shaft re-installed in typing unit.

That's where it goes. This is the typing unit viewed from the bottom side. From top to bottom, the drive gear for the keyboard (engages with gear on removable keyboard), main bearing, drive gear from motor (engages with gear on removable base), spacing clutch and carriage advance gear, printing clutch, selector clutch, and the selector assembly at the bottom. To be useful, all gears must connect to at least two other rotating elements.

The alignment of this is a bit touchy. It has to be positioned vertically so that little cams near the bottom of the main shaft hit the proper parts in the selector unit.


The tiny pointy thing on the shaft, just below the bottom disc, has to hit the lever at its right.


The typing unit on the base.

Here's the typing unit on the base. The base just got a new power cord and a correct sized fuse, along with the usual cleaning. The base has the motor, and when the typing unit is placed on it and three thumbscrews tightened, all the necessary mechanical and electrical connections are made.
This is enough to allow trying to operate the machine.  So, cautiously, the machine is turned on, and it "runs open"; the mechanism cycles, but it's not doing anything. Nothing seems to be jammed. That's a good sign.  A minute or two of this is enough to get the lubricants moved around and loosen up the mechanism.

(There's a keyboard which slips into the front, but it's needs more work. It's not necessary at this stage.)

Now to apply a input signal and see what happens.

First, we need a "loop supply" - 120VDC, 60mA.


Current loop test box.

As soon as the machine is plugged into this, the selector magnet pulls in and the selector clutch disengages. The machine is now idling properly - the motor and main shaft turn, but not much else happens.  That's a very good sign - the selector magnet and clutches work. Next we need a data source.


Model 14 tape printer, in steampunk case.

While I could drive this from a computer, I have an extra Model 14 tape printer handy, so I plug that into the loop. Now, anything I type on its keyboard should print on both machines. If they're working properly.

The first test is so-so. The big machine does respond to input from the little one, but it's not typing the right characters. Bits 1, 2 and 5 seem to be OK, but bits 3 and 4 are stuck. That problem seems to be in the selector mechanism. The spacing clutch isn't engaging and the carriage doesn't move. One typebar sometimes sticks. This is a reasonably good result for a first power-up.

« Last Edit: September 12, 2014, 01:18:18 am by oldskoolpunk » Logged
Flightless Phoenix
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« Reply #32 on: September 12, 2014, 03:05:01 pm »

This is a completely fascinating thread. I will be watching your progress eagerly. Thank you so much. It's wonderful to know that there are still people with the knowledge, skills and above all, patience to undertake these restoration projects =]
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« Reply #33 on: September 13, 2014, 07:29:01 pm »

This is a completely fascinating thread. I will be watching your progress eagerly. Thank you so much. It's wonderful to know that there are still people with the knowledge, skills and above all, patience to undertake these restoration projects =]

Ditto
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« Reply #34 on: September 14, 2014, 05:10:15 am »

Plugging away.  The selector is mis-selecting because one of the clutches is slipping. When I hand-crank the machine through a cycle, I can see the selector camshaft stop momentarily. And sometimes, especially right after motor start, that clutch won't engage at all.


Selector clutch assembly, showing Washer, Felt, 6861, and Washer, Felt 72563.

The left felt, sandwiched between the two discs, is 6861, and it looks OK. The right felt, 72563, which looks like a gummy mess, needs to be replaced.  Unfortunately, while I have two suitcases full of Teletype parts in numbered envelopes, and most of the main shaft parts, I don't have that one.  So I've sent a message out to the Teletype restoration community.

If that doesn't work, I'll have to make one.  I'll have to get a felt sheet of the right thickness and properties, and laser-cut some washers out of it.
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« Reply #35 on: September 15, 2014, 02:38:09 am »

Excellent.

Question: What solvents do you find to be effective for extreme amounts of rust....? I realize this particular project didn't have that issue. I'm vacillating between starting a 'typewriter restoration' thread of my own or just trying to figure things out from reading others' processes.

For context, I have an Underwood No. 5 in disrepair.
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« Reply #36 on: September 15, 2014, 05:13:49 am »

What solvents do you find to be effective for extreme amounts of rust....? ... For context, I have an Underwood No. 5 in disrepair.
There's Evapo-Rust. This is not a solvent; it's a chelating agent. It removes oxides, but not metal. The metal must be entirely immersed in Evapo-Rust; at the air surface, it will cause rust. So you need a lot of it. However, you can reuse an Evapo-Rust bath until it turns black, having consumed all the rust it can.

Evapo-Rust will leave you with bare metal. There may be voids where metal had already turned to rust, of course. Also, it will remove most oxide-type protective finishes, such as Parkerizing and gun bluing. Once removed from Evapo-Rust, the metal must be quickly cleaned and dried, or it will start to rust within hours. Then you'll need some form of rust protectant if it's not a oiled part. I've used this on a rusted Teletype Model 14 typing unit, and it worked, but it stripped the Parkerizing. I had to apply a spray-on rust protectant.

Since you can buy a non-rusted Underwood No. 5 on eBay for $50, I'd suggest buying a clean one and keeping the rusted one for the parts. You're going to spend more than that repairing a rusted machine.
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« Reply #37 on: September 15, 2014, 07:48:45 am »

The selector clutch wasn't the problem. It's fine. The selector levers are sticking. Intermittently. I don't know why yet. I'd already soaked the selector in Simple Green, and oiled it. I see a full disassembly of the selector in my near future.


Model 15 selector mechanism, simplified drawing. (Only one bit of 5 is shown.)

This is the decoder that takes serial bits and turns them into parallel bits. There are really five selector cams, selector levers, swords, T-levers, and vanes. There's only one selector magnet, armature, and armature extension.

The selector cam(s) are at the end of the main shaft that was just disassembled and reassembled.  The selector cams start rotating when a character starts (a 1 to 0 transition on input) and rotate for one character time. That's all handled by other parts of the machine. Here, assume this is bit 1 of 5 (they didn't number from 0 back in the 1920s). The selector magnet is in the 1 or 0 position, and its extension arm has two projections, which line up with the sword arms. When the cam lobe comes around and pushes the selector lever, the sword is pulled back.
If the selector magnet is in the 1 (MARK) position, the upper sword arm hits the upper selector magnet extension. This tilts the sword so that the point of the sword moves down and hits the down limit stop. If the selector magnet is in the 0 (SPACE) position, the lower sword arm hits the lower selector magnet extension, and the point of the sword moves up. One bit has now been decoded and mechanically amplified. (The selector magnet is weak, but the motor driving the camshaft is 1/40 HP. However, there are oiled felt clutches. If something sticks or jams, the clutches will slip. That's happening here.)

When the cam lobe passes the selector lever, the sword moves forward, powered by a spring, and pushes on either the upper or lower half of the T-lever. This sets the selector vane to the upper or lower position. One bit of data has now been transferred to one of the five vanes, which are a mechanical 5-bit bus leading to the carriage and typebars.

This process repeats five times, for five bits. The vane positions then represent the 5 bits of the character.
Then a sixth cam, not shown, operates a trip latch which causes a big clutch to engage and the printing mechanism cycles, to print one character. 

Something in the selector cam/sword pullback mechanism is sticking.  That's my project for tomorrow.

(There's a manufacturer's manual which gives a detailed description of how this all works. If you're really interested.)

If you write steampunk fiction, try to give a feel of this level of complexity. Steampunk is not magic. Steampunk is moving parts. This is what moving parts are like. Technology where you don't need to know how it works is very, very recent. Post-1970, at least. Much later than steampunk. To use technology, characters must understand much of it.

Here endeth the lecture.
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« Reply #38 on: September 15, 2014, 09:55:39 pm »


Selector cleaning, first try.

Here's the selector mechanism, the part shown in the drawing above. This is it being cleaned last week. The electromagnets should not get wet, so they're above the water line. The problem is, so are the five selector levers and the tops of the plates they slide between. Those are the selector levers that are sticking. After that bath, the selector levers moved, but probably only because the soapy cleaner was helping. Cleaning fail.


Selector cleaning, second try.
Second time around. The big bolt holds the magnets above the water line, while all those close-fitting plates, selector levers, and swords get a good soak. I'm going to give them a few days in this bath.

The green liquid is Simple Green, a mild citrus-based solvent that dissolves most oils and greases. Stronger solvents are available but I don't like to use them unless necessary.
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« Reply #39 on: September 17, 2014, 08:24:05 am »

After even more cleaning (Simple Green, distilled water rinse, CRC brake cleaner, compressed air) the selector is unstuck.  So everything gets reassembled and tested.  Selecting is still wrong.  Bits 1-2 select OK; the others are often wrong.

At least some of the time, the selector clutches are slipping. I can see this when hand-cranking the machine.
Each selector clutch is two discs with an oiled felt washer between them. There are two, one on each end of the selector cam sleeve, with a spring to compress the whole stack. The selector doesn't have much load on it, so these are just slip clutches; there's nothing that engages or disengages them. There's an arm that sticks out and runs into a stop, and that stops the rotation. This setup starts and stops on every character.  Amazingly, the felts rarely wear out,
as long as they're kept oiled.

There's a detailed "adjustments manual" for the machine, and it specifies that the force required to stop the selector arm should be 14 to 18 ounces.


Measuring selector clutch torque.

It's 300 to 400g, which is 10.6 to 14.1 oz.  Too low. That may be why it's slipping.
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« Reply #40 on: September 17, 2014, 12:27:01 pm »

Continue to enjoy watching this.  I have one of those gauges (got is 30 years ago) and never knew what they where for. Now I know.   Learn something new everyday.

Thanks.
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« Reply #41 on: September 18, 2014, 12:06:33 am »

I have the whole machine together, with the keyboard, and when I press a key on the keyboard, a letter types and the carriage advances. But it's usually the wrong letter.

With the keyboard in place, driven from the same driveshaft, it's possible to slowly crank the machine through a typing cycle by turning the motor by hand. The keyboard and typing unit have no mechanical connection other than the motor they share. Data is encoded in the keyboard, with five contacts set up by a key press, and read out in sequence mechanically.  This generates the bit stream. The selector magnet decodes the bits, timed by the same motor shaft that's driving the keyboard. So the whole encode/decode process works when hand-cranked very slowly.

Hand-cranked, things mostly work. The right letters are selected. The FIGS/LTRS shift works. Spacing works. Line feed works. Carriage return doesn't work, so there's something stuck in the spacing clutch. Haven't tried the bell yet.

But at full speed, the bits get garbled. Something is slipping or binding so that it won't work right at full speed. I need to work on the selector clutch tension, the trip lever tension, and maybe replace the clutch felts. The keyboard also needs work. 
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« Reply #42 on: September 19, 2014, 06:44:31 am »

Plutus Sar, (or anybody) if you are in the South East US, please let me know if you find one of these that's about to be trashed or given away.  I will be glad to give it a good home.
Stan
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« Reply #43 on: September 19, 2014, 11:00:13 pm »

At last, the typing unit is picking the right letters.


The lever coming in from the left isn't going far enough up to stop the curved sword end.

Notice how the shiny curved arm on the right almost slips over the vertical lever extension. That's supposed to be a solid hit. Right there is the problem. At hand-crank speed, it works, but at full speed, it slips past. (For a full explanation of what the selector does, see Teletype Model 15 Description).

There's an adjusting nut for this. So I backed that nut off by two flats. That was enough to fix the problem. The lever now gets a solid hit on the sword end, all 5 bits decode properly, and the right typebars hit the paper.

This is what steampunk-era technology is about. You can look at the thing, see how it works, and fix it.

Getting this working is a relief. There are other problems. The spacing clutch that advances the carriage isn't working, so I can't put in a ribbon and type something yet. There's lots of cleanup (keytops, more cleaning, touch-up paint). Typing unit selection is the most finicky part of the machine, and now that's fixed. The rest is easier. 
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« Reply #44 on: September 20, 2014, 12:08:46 pm »

Brilliant stuff. Please keep us posted!

Thanks,

HP
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« Reply #45 on: September 21, 2014, 08:50:54 am »

Working on the spacing mechanism today. The front spacer pawl was stuck; this is, again, a lubricant problem where a collar rides on a smooth shaft. I thought I'd fixed all of those; I previously got the rear spacer pawl un-stuck by oiling it and pushing it back and forth a few hundred times until it moved smoothly. I had to do that to the rear spacer pawl, which was harder, because it's not in a finger-accessable place. I had to hook a loop of wire around it so I could pull on it. Not fun to work it free that way.

After that, spacing still doesn't work.  Now the spacing clutch is being blocked by the right margin mechanism.


The downward-pointing stop is running into the disc with projections.

The bracket which carries that mechanism is out of position. It's about 1mm low and 2mm to the left of where it should be. It's held by two screws on the other side. I suspect one of them has sheared. Probably because someone dropped the machine on its right hand side, or it was transported without the carriage locked, and the carriage ran into the right margin. Nothing looks bent; I suspect a sheared screw. I've already found and fixed one of those.


The two screws at the center need to come out.

The screws I need to remove are 5/16" hex-head with screwdriver slots. Getting them out is difficult. They're stuck hard. There's no straight-in approach; those parallel rails (the printing bail) are in the way. Taking out the printing bail is a big deal, although not impossible. I can get a 5/16" socket onto them, but the socket handle is too big. A small end wrench might do it, though flat access is blocked by the projecting rack rail above. A 5/16 offset-end wrench will probably be necessary. Or a small right-angle handle for 1/4" drive sockets.  Like this.


L-handle, for 1/4" socket. Exactly what I need, but the manufacturer is in India.

I'll look for the right tool on Monday. Fortunately, I'm two miles from the intersection of Commercial St. and Industrial Blvd, where there are several tool stores.
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« Reply #46 on: September 22, 2014, 05:01:22 am »


Always use the right tool for the job. 5/16" angled box/end wrench, from O'Reilly Auto Parts.

Nothing was bent or damaged; it turns out those two screws fit into large holes in the bracket to allow easy adjustment. They just needed to be loosened, the bracket placed in the proper position, and the screws retightened.


Margin stop lever now hits the cam only when the carriage is at the right margin.
(The margin mechanism on this model just stops the carriage from advancing further. It doesn't cause a carriage return or inhibit typing. If input continues without a CR, you just get lots of letters typed on top of each other, and eventually a hole in the paper.)

At this point, typing and spacing are working. It's possible to type something.


Hello world

First typing! (Without a ribbon, so it's indentation in the paper.) This is going to work.

Lots of little problems remain - the next one is that carriage return doesn't work properly; the CR character releases the spacing clutch and the carriage moves back some, but the clutch re-engages before the left margin is reached. I have a list. There's no permanent damage to this machine, and it will live again.
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« Reply #47 on: September 22, 2014, 05:12:36 am »

I remember when I got my little basket-case Royal portable (found at a rummage sale) to work for the first time. Sat down and typed three whole pages - er, fraught with mistakes, of course. Wink
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« Reply #48 on: September 24, 2014, 06:42:49 am »

Finally ready to put in a ribbon and a roll of paper.  Printing works, but the print quality is poor.


Impact printing, the early years.

This doesn't look good, but it can probably be fixed. The problems have to be dealt with one at a time.

1. The first two characters are spaced too close together. That's easy to fix. the left margin stop screw has to be adjusted to be consistent with where the carriage spacing gear advances for each character.

2. Only the lower part of letters prints for the first part of the line. This is due to a problem with the "ribbon oscillator", which lifts up the ribbon during typing and lets it down otherwise so the operator can see what they typed. Something in the rail that drives the ribbon oscillator has to be misadjusted, bent, or broken. There are bent parts in the ribbon oscillator. I can get replacements if necessary.

3.  The vertical spacing is sometimes single, sometimes double, and sometimes in between. The mechanism that advances the platen roller needs some attention.  I haven't looked at that part of the machine in detail yet.

4.  The letters "S" and "X" are not printing properly. The "S" typebar is binding at one point in its travel. I haven't looked at the "X" typebar yet.


The "S" typebar. Something is sticking in there. It's not just dirt; there may be burrs on the metal.

Other than print quality, there's a whole list of minor problems that need attention.  The bell doesn't work. Ribbon reverse doesn't work. Some keycaps on the keyboard have fallen off.

Onward.

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« Reply #49 on: September 25, 2014, 11:28:47 pm »

It's not looking good for the type basket. There may be too much damage there to fix. The rightmost four type bars show signs of having been bent and then straightened, not too well. The typebar segment, which is a machined casting that supports and guides all the typebars, has one slot (for "S") that's too wide. Somebody must have used a file to widen that, trying to un-jam the "S" typebar. Now the "S" typebar flops around and hits the "X" typebar.

I've found two sources for a new type basket, and may just swap out that whole section. Worst case, I have to remove the type basket and replace the typebar segment, for which I have a spare, and clean up and straighten the bent type bars. That means a full teardown of the type basket, all 26 typebars, pull bars, and springs.   
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