Early membrane buckling spring hammer type in IBM 5441 keyboard

Karmel · 30 Jun 2021, 23:36

I'm not sure if this is common knowledge as I couldn't find anything about it.

I picked up a really good condition IBM Wheelwriter 5 (or IBM 5441 as it says on the back) from a thrift store a while back, the only flaw being a rather large crack in the case near the back. Despite how old it is all of the plastic rivets are still there. It's from 1984, so it has one of the first keyboards to use membrane buckling springs, seeing as the the Enhanced Keyboard came out in 1985.

Spoiler:

As for the keyboard itself, the keyfeel is super scratchy with the keycaps it came with, and it feels like the bottom out point is further down than a regular M, more like that of an F. I replaced the alpha keys with those from an F XT that I gutted for parts and now it feels almost identical to a Model F, same smoothness, tactility and travel distance. It's almost the same weighting as well, though weighting can be a bit inconsistent on these boards from my experience.

As for sound, it sounds just like a regular Model M but louder and it pings like crazy, it's almost on par with an F. I thought this was due to the large and open typewriter case, but another much younger Wheelwriter I have says otherwise.

I didn't think much of it until I decided to actually look inside the barrels of the switches with a flashlight recently, I noticed that the spring end of the hammer was shaped more like that of an F hammer, although I'm not sure about the rest of it as I can't see that far in there, though it doesn't have the upstroke sound of the hammer snapping back up like a F does, so I doubt it's any different in terms of size.

I placed a capacitive hammer and a membrane hammer next to a barrel for comparison. The difference may be a bit hard to see as I couldn't really get the best position with my camera.

Spoiler:

As I said before, I don't know if this is well known or not as I couldn't find anything about it. I'm not gonna take it apart and bolt/screw mod it since all the rivets are still there and it's overall really clean.

nickg · 01 Jul 2021, 16:46

kinda makes sense ibm would have a "missing link" for this stuff. really cool to see. those keycaps are BEAUTIFUL, makes me wanna try to grab a set of unicomp's new white ones.

sharktastica · 01 Jul 2021, 17:35

I think the fact that membrane buckling springs appeared in 1984 is known by most; the Wheelwriters 3 and 5 and the Quietwriter 7 were all released around 13th December 1984, although they were announced (and thus likely manufactured) in advance of that date. Nuances about the hammers aren't widely documented at present though, although others have reported seeing similar cut-outs on them from other Wheewriters. In a way, they resemble the hammers of Brother buckling springs as well, but they're definitely a relative (or, parent) of standard M hammers as per other dimensions (Brother buckling springs hammers are also taller heightwise and stubbier lengthwise).

I also have some later Wheelwriters, but those had standard flippers that were completely interchangeable with other Model Ms. In fact, I repaired one of the assemblies using brand-new Unicomp spring and hammer couples and the key feel was identical. For reference, I have a 1990 IBM 6783 Wheelwriter 10 Series II and an IBM Wheelwriter 3500 with a 2001-made Unicomp keyboard module (I also have late '80s Wheelwriter in storage that I haven't toyed around with yet, but should do soon).

: da27ac34-e344-4edd-b78e-fccbbac892e3.png (76.85 KiB) Viewed 1483 times

(Another early?) Wheelwriter hammer (photo credits: fricked)

: a01_m_bttm2s.png (111.42 KiB) Viewed 1487 times

Standard M versus Brother (from IBM 5576-A01) hammers (photo credits: J. Szybowski)

Regardless, it was definitely a good thing to post about! Cheers!

Edit: Almost forgot, pandrew (or purdeaandrei on DT and r/ModelM Discord servers) was attempting to track the variations in flipper design. Might be worth getting in touch with him.

fohat · 01 Jul 2021, 18:56

Those heavy 1-piece typewriter keys are excellent and I have used them quite a bit on my Model Fs that are daily drivers.

That "Code" key is quite desirable for people who want a divided space bar. I haven't done it but I think that it can be paired with a long Right Shift (buy a blank one from Unicomp and no one will know) without any other modifications.

Lastly, some of these have a spring around the space bar barrel that adds 10g-20g. Some people (such as myself) really like these and they are extremely hard to find.

Karmel · 01 Jul 2021, 19:35

fohat wrote: ↑
01 Jul 2021, 18:56
Those heavy 1-piece typewriter keys are excellent and I have used them quite a bit on my Model Fs that are daily drivers.

That "Code" key is quite desirable for people who want a divided space bar. I haven't done it but I think that it can be paired with a long Right Shift (buy a blank one from Unicomp and no one will know) without any other modifications.

Lastly, some of these have a spring around the space bar barrel that adds 10g-20g. Some people (such as myself) really like these and they are extremely hard to find.

This one did have o-rings around the barrels, which did nothing, but no space bar spring. On regular Ms I can usually bend the space bar stab a little to stiffen it, but with Wheelwriters it seems to not work as well for some reason.

As for the caps, this one might have just come with a bad batch or something, or it hasn't been used that much. The green legends do look really nice, and I have a much later Wheelwriter 30 board from a broken unit that I can get caps from.

fricked · 02 Jul 2021, 16:06

I found my "cushionless" wheelwriter flippers in my First Edition Wheelwriter 3. I assumed they were in all wheelwriters but they seem to be uncommon. I also find them to have a longer travel distance and harder bottom out, like an f. But they are just as heavy as any other m. Wheelwriters also omit the rubber sheet found in model ms which makes wheelwriters sound much louder and harder (?). I combined the cushionless flippers with the model m rubber sheet (a combination IBM never did as far as I know) and I really enjoy the result; definitely my favorite model m.
Here it is in action: