Yet another beamspring refurb (5251)

[AJM]

Rattling in the sense, that the switches don't sit tight and can be wiggled around: Yes, that is fixed now.
If you mean rattling in terms of sound: Sound was pretty much unchanged by the restauration.

[SneakyRobb]

Beamspring switches have the most play of any switches. You can rotate keytops like 5 degrees when they sit. You can press a 7U beamspring spacebar about 90% of its length with no stabilizer bar.

[SneakyRobb]

So I am now in the not sure what the keycaps are made of camp. I am waiting to hear back from the IBM archives guy. IBM developed acrylic injected keycaps in 1967 but I am fairly certain they are the clear relegendable ones on displaywriters, model f/ and pingmasters.

I tried the acetone on one black with white legend beamspring key and it sort of did something to the black outerplastic. No colour came off though onto the cloth. I could easily scrape off the slight discoloration and make it shiny again though on the black part so I don't know if it just has a laquer on it and the acetone did something to that laquer.

On the white plastic doubleshot inside of the same key, the acetone did nothing.

So the blackpart could be ABS although I have found no references to ABS being used in any manuals. It does say to never clean beamspring keycaps with alcohol of methyl chloride. This doesn't help much as we are not trying to tell the difference between pbt and abs. Most solvents will melt many candidates pretty equally. Also pbt wasnt really used until the 1970s.


The candidates I have been searching for are abs, acrylic, bakelite, polyimide, melamine, and other formaldehyde plastics. They could also be some variant of polycarbonate.

As for the PEI logo, I believe it is some kind of internal mold marking possibly a subdivision of ibm another company or an outdated material code. Most of the keys have mold marks like M-15 which is probably the specific mold to trace issues. The PEI mark doesn't look like those at all. From what I can tell Polyetherimide wasn't invented until the early 80s.

IBM did update their two-shot injection molding process in the early 80s for replacement keycaps, but it seems more likely they would have just used ABS. As well for some reason they decided to shoot the outer part of the key first then the insert. Perhaps there was some plastic bonding reason for this. Or maybe just nicer legends.

I do know that earlier IBM electric type writers had cellulose and bakelite keycaps that had laquer finishes. So I will wait for the archives guy to see if he has anything.

So the IBM archives guy Max got back to me and the IBM Archives can't find any reference to what type of plastic was used in the beamspring keys.

I may contact the original factory workers.

Through my own research I am now confident enough to say I don't know what they are. (Science!)

From what I have learned they are most likely one of several things. It is likely a thermoplastic. The list is too much, but basically short of me sending a key away for testing, which I am doing. It is likely ABS, Polycarbonate, POM, Melamine, Nylon, PVC, or other thermoset. Narrows it down right?



"Hi Robb,

I've searched the collection and found no indication of the specific plastic IBM used for the manufacturing of the key caps. I looked in the field engineering manuals, maintenance manuals, as well as the IBM Lexington News from that time frame but I did not see anything about the key caps. The same goes for the color. It most of the PR for these typewriters and computers, IBM uses standard language such as "gray" or "red." I think it is safe to assume that they used a specific type of gray or a specific type of red, it is just not mentioned what type.

As you know, it is possible that this info will turn up somewhere, so I will keep an eye out and let you know if I find anything!

Max

Reference Desk
IBM Corporate Archives
2455 South Rd
Bldg 04-02 Room CSC12
Poughkeepsie, NY 12601

"

[darkcruix]

Many thanks for the check - wonderful

[Ander]

Robb: Outstanding, inspiring work! Thanks for sharing in such detail. How did you make such neat holes in your padding? A metal punch that you tap with a mallet, so you can align it as accurately as possible? But even then... I can't imagine another way, outside of having an actual machine tool of some kind.

[lucar]

@matt3o: Oh, thank you.

@darkcruiz: Thanks. There is no wobble (at the moment). After cutting around on the foam to make it thinner (by about a good third), I hit the sweet spot: Thin enough to enable a correct assembly, and thick enough to hold the switches properly.

Could You Express that in mm ?
Very nice job! Congrats
Luca

[AJM]

Hi Luca,

In the end it was about 2 mm thick. But I fear that information isn't worth much, unless you have foam with the same firmness.
(And as I wrote - I can't say what kind of foam it is and where it came from.)
All I can say is that it's quite firm. (Some people write, that they're using 2 mm thick foam for a Model F XT. That would not be possible with 2 mm of the foam that I used in this case.)
And that I stuck that car paint protection film on the side of the foam, where the switches press against, certainly makes difference as well.

[lucar]

Hi Luca,

In the end it was about 2 mm thick. But I fear that information isn't worth much, unless you have foam with the same firmness...

Thanks for the information.

I'm restoring a Model F "BigFoot" and I used 1 mm thick Eva art foam and It works well after I failed with 3 mm insulation foam. The two plates still don't close by using bare hands but do using welding clamps help. So I take note that on those beauties foam must be 2mm or less thick.

Luca

[Excelso]

Hi Luca,

In the end it was about 2 mm thick. But I fear that information isn't worth much, unless you have foam with the same firmness...

Thanks for the information.

I'm restoring a Model F "BigFoot" and I used 1 mm thick Eva art foam and It works well after I failed with 3 mm insulation foam. The two plates still don't close by using bare hands but do using welding clamps help. So I take note that on those beauties foam must be 2mm or less thick.

Luca

I'm using EVA also for my bigfoot/XT project and it gets just the right after some time pressed. Right now I have a new sheet under weigh load so I can work better with it later without clamps or other tools.

[lucar]

I'm using EVA also for my bigfoot/XT project and it gets just the right after some time pressed. Right now I have a new sheet under weigh load so I can work better with it later without clamps or other tools.

Hi, if you didn't already, I strongly suggest You to release some spacebar stabilizer tension to have a lighter spacebar and absolutely make a floss mod. It's tediuos, but the spring ping disappears completely and the resulting sound and feeling is superb on the Bigfoot

[AJM]

And to finish my thread off - a few pictures with a new set of German keycaps, which I got through swapping with a well-known forum member.
They're a bit yellowed, but I simply call them ivory-coloured = problem solved.

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[darkcruix]

The keyboard looks awesome. I am still waiting for a few parts, before I make my restoration post
Thanks for sharing the pictures!

[nickg]

Dude that is one of the most beautiful boards I've ever seen! I can't wait until mine gets here this week.

[Ander]

I'd still like to know how you made such precise holes in your foam. (Maybe I should ask in German?)

[Wingklip]

Beamspring switches have the most play of any switches. You can rotate keytops like 5 degrees when they sit. You can press a 7U beamspring spacebar about 90% of its length with no stabilizer bar.

How can one minimize this play in the switches? Are there any known modifications to the keyboard to accomodate for this? I love the feel of beam spring switches but my biggest disdain is the fact that I can't accurately type in what I want as the switches keep moving everywhere and catching my fingers' edges when I try to type on another key.

But judging from the full restore photos, it seems that better foam does affect how much play there is? Correct me if I'm wrong pls

[darkcruix]

Beamspring switches have the most play of any switches. You can rotate keytops like 5 degrees when they sit. You can press a 7U beamspring spacebar about 90% of its length with no stabilizer bar.

How can one minimize this play in the switches? Are there any known modifications to the keyboard to accomodate for this? I love the feel of beam spring switches but my biggest disdain is the fact that I can't accurately type in what I want as the switches keep moving everywhere and catching my fingers' edges when I try to type on another key.

But judging from the full restore photos, it seems that better foam does affect how much play there is? Correct me if I'm wrong pls

I had the same issues. The replacement with a good foam (2mm) and re-seating the switch housings so they sit really tight, makes all the difference. In my case it solved the issue in multiple restorations already. The worst was my 3278 - you can find my restoration guide here also (viewtopic.php?f=7&t=19775)

[AJM]

@Ander
The holes themselves are quite precise, because they're made with a hole punch (in my case not in the "perfect" size 15 mm, because I couldn't find a tool in that size - instead I used 16 mm).
The placement of the holes isn't actually very precise. Mainly because the markings, which I made through the metal plate, are of course smaller than the hole punch so you can't see the markings when you place the tool on top of it. So because of this and because my foam didn't stretch, because I put this car paint protection film on one side of it, it was a good thing, that my hole punch was a bit bigger than planned. During the fitting I also enlarged a few holes, that were too far off.


@Wingklip
- There is - of course - a bit of play in the switch itself, but I would say, that's not more than any MX switch.
- Then there is the main problem that the whole switch rattles, if the foam isn't good or thick enough to press the switch against the PCB. This should be rectified completely by a proper foam replacement.
- And finally there is the peculiarity of beamspring boards, that the switch can be rotated by a few degrees, because the little prong in the top plate, that limits a rotation, is quite a bit smaller than the related notch in the switch. That small possible rotation is again limited by the friction with the foam. I'm very happy (and lucky), how this turned out in my case - as I have descripted in my first posts.

[badjona7an]

Got mine for 7‎€ from a a guy that wasn't even listed it for sale. Sadly(or not) it had no top presumably removed to be sold to some scrap depot for like less than 10c, which is likely the reason I was the lucky one, since seller knew IBM keyboards were trending to be expensive, but apart from a stamp on the inner side of the top he couldn't have known it's an IBM If you remember the commercial of the Logitech G710+, this one looked like it did it for real and in therms of build quality and longevity these keyboards have no analog, not even close, I can only compare such with the Great Pyramids of Giza

[AJM]

As I wrote at the end of my initial post - The 5251 keyboard looks a bit bloated in front of a 27" Apple Display.
In front of a 13" inch display it's fine though - provided you choose the original terminal :

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And if you like that kind of thing - here is also a little typing demo. (Copyright for the channel name belongs to vometia )
[youtube]https://youtu.be/WSLx1TKn6XA[/youtube]

[User101]

As I wrote at the end of my initial post - The 5251 keyboard looks a bit bloated in front of a 27" Apple Display.
In front of a 13" inch display it's fine though - provided you choose the original terminal :

5251-b-1.jpg

5251-b-2.jpg

5251-b-3.jpg

5251-b-4.jpg

5251-b-5.jpg

5251-b-6.jpg


And if you like that kind of thing - here is also a little typing demo. (Copyright for the channel name belongs to vometia )
[youtube]https://youtu.be/WSLx1TKn6XA[/youtube]

Beautiful