A lighter Model M

[Bjerrk]

Hi all,
Some Model Fs (Ellipse's New Model F, the Model F AT etc) feel significantly lighter than Model M buckling springs, and I have to say that I prefer the lighter keyfeel somewhat.

Since I had a few of Ellipse's Model F springs lying around, I decided to try and swap them into a couple of Model Ms (a 1987 IBM one and a 2000s Unicomp one). I had a bit of trouble getting it to work well in the IBM Model M (not sure why yet), but to my surprise the springs worked perfectly with the Unicomp one, and the spring-swapped keys (the arrow keys) now feel significantly lighter.

I'm pretty excited about this, since the stiffness of the keys is essentially the only complaint I have about the Model M.

The really exciting thing would be if it turned out to be possible to order similarly spec'ed springs (length, diameter, spring constant) without having to resort to harvesting old Model Fs ( ) or ordering spares at 1USD/piece from Ellipse (with uncertain delivery times etc). Let me know if you have any ideas or questions!

(Note: There is an old thread on Geekhack discussing this, where one person tries comparing with XT springs, and another conjectures that it would feel the exact same. I can only say that the difference is highly noticeable with Ellipse's F springs in this Model M)

[gianni]

Can you do a test with coins? I don't know if it's doable with buckling springs.

I'm interested in this since I have some old M that I'd like to convert.

Please test these:
- buckling of unmodified model F
- buckling of model M
- buckling of model M with F springs

[CallmeJohn]

I don't remember where I read this but the weight difference comes from the size of the flipper, since the f flipper is larger than the M's. Not sure if it's true but makes sense to me. I wonder how much a model f flipper weighs compared too a m flipper.

[Muirium]

Yeah, there's more going on between M and F than just differences in the spring. But investigate the things we can change, by all means.

I find the bigger difference between the two is the click. Model F is much snappier. Model M feels balky, and creaks a bit while going down, then the tactile event isn't as AUTHORITATIVE as Model F's magnificent click. Model F's both smoother and clickier, significantly so. It's all about the leverage on that great big flipper, and its hard landing on PCB instead of mooshy membranes.

[gianni]

I don't remember where I read this but the weight difference comes from the size of the flipper, since the f flipper is larger than the M's. Not sure if it's true but makes sense to me. I wonder how much a model f flipper weighs compared too a m flipper.

Agreed, I've always heard that, but hey, let's see how the coin test goes. I would be very interesting, if differences are small

[Bjerrk]

The differences are, as I mentioned, highly noticeable. Not in the "minutiae" department.

I'll see what I can do when it comes to testing, but I don't have any coins (using cash is uncommon here ... ).

[gianni]

deleted

[Bjerrk]

50-øre coin
Weight: 4.3 grams

1-krone coin
Weight: 3.6 grams

2-krone coin
Weight: 5.9 grams

5-krone coin
Weight: 9.2 grams

10-krone coin
Weight: 7.0 grams

20-krone coin
Weight: 9.3 grams

Nice But doesn't help given that I have 0 coins.
But I have some accurate scales - I'll find a way.

[Bjerrk]

Alright, the verdict is in. I found a bunch of Euro coins that I had from a holiday - knew they'd come in handy sooner or later.

I tested three configurations:
Unicomp Model M with original springs
Unicomp Model M with New Model F springs
New Model F with New Model F springs

I took the coins, stacked them and taped them together to prevent sliding.
I then placed the stack on a key, slowly so as to avoid imparting any momentum.





The results for the spring buckling (i.e. not bottom out) are:
Unicomp Model M with original springs: 66g
Unicomp Model M with New Model F springs: 44g
New Model F with New Model F springs: 53g

Now, better measurements could be made with an improved method, but it is at least clear that the swapped Model M keys are significantly lighter.
The measurements also fit well with the subjective experience: The swapped M feels much lighter than the unswapped one, and even a bit lighter than the Model F. Similarly, swapping an original M spring into the New Model F renders it stiffer than it was before.

So: It's possible to lighten up ye olde M, it's just a question of getting the right springs

[Yasu0]

Nice, thank you.

[gianni]

This is a breakthrough.

Given that the new model F should be nearly identical to the old Fs, I'll be able to use the springs of an old and unusable bigfoot F to make my M (which I hate) much nicer. Not silent, but finally light and snappy.

What's the best way, do you just pull the springs with a tweezer? Or disassamble everything (I hope not).

A memo about the correct position of the spring:
https://www.youtube.com/watch?v=Evn6vmrfD4M

[gianni]

Removing the springs from the model m seems quite difficult:

viewtopic.php?t=19677

It’s possible. I’ve done Ms and Fs with a sharpened matchstick. The “chopstick method” can be fiddly but once you’ve got the hang of it, you’ll have a slow and fiddly skill you won’t need very often, for life!

I believe the "trick" is to really squeeze the spring right down into a little cylinder of wire and *then* turn it around and around until it comes off its plastic peg. When there's any air-space between the coils, the spring's too tight at its base. To make it budge, you need it good and compressed. Nothing violent, it's more a skill of coercive precision.

F spring in M
https://geekhack.org/index.php?topic=77902.0

[Bjerrk]

I use the chopstick method (or, rather, some kind of wooden meat skewer or cocktail stick) as well - hasn't failed me yet

[Bjerrk]

But yeah, for some reason it worked flawlessly on the Unicomp Model M, but I had some difficulty getting the F springs to work in an 1987 IBM Model M. I'll have to look more into that (try again with more tenacity ...), though.

What happened was essentially that the spring somehow didn't buckle, but just felt linear. Like when the keycap doesn't catch correctly on the spring. However, it still worked in the Unicomp if original IBM keycaps were employed, so it doesn't seem to be a question of subtly different keycap geometries.

[gianni]

Any update, how does it feel after a month of use? Would you suggest people to try the mod?

Hi all,
Some Model Fs (Ellipse's New Model F, the Model F AT etc) feel significantly lighter than Model M buckling springs, and I have to say that I prefer the lighter keyfeel somewhat.

Since I had a few of Ellipse's Model F springs lying around, I decided to try and swap them into a couple of Model Ms (a 1987 IBM one and a 2000s Unicomp one). I had a bit of trouble getting it to work well in the IBM Model M (not sure why yet), but to my surprise the springs worked perfectly with the Unicomp one, and the spring-swapped keys (the arrow keys) now feel significantly lighter.

I'm pretty excited about this, since the stiffness of the keys is essentially the only complaint I have about the Model M.

The really exciting thing would be if it turned out to be possible to order similarly spec'ed springs (length, diameter, spring constant) without having to resort to harvesting old Model Fs ( ) or ordering spares at 1USD/piece from Ellipse (with uncertain delivery times etc). Let me know if you have any ideas or questions!

(Note: There is an old thread on Geekhack discussing this, where one person tries comparing with XT springs, and another conjectures that it would feel the exact same. I can only say that the difference is highly noticeable with Ellipse's F springs in this Model M)

[Bjerrk]

Any update, how does it feel after a month of use? Would you suggest people to try the mod?

No updates, unfortunately. I only had 10 extra F springs, so I couldn't mod a whole keyboard, only a few keys. Until I have many more springs, I won't really be able to test it longer term.

I certainly recommend to try it - it's easily reversible in any case. The only "caveat" is that, as I mentioned, I had problems getting the F springs seated correctly in my 1987 IBM Model M, whereas it was easy in my Unicomp. But I would love to hear the results of others.

[CollapsedKeycap]

It would be nice if there was an affordable source of model f springs, Ellipse only sells them with the flipper, and offers no bulk discount.
Even broken model F keyboards are quite expensive.

I suspect the trouble with getting them working in an IBM model M might be from the thicker rubber sheet over the membrane.

[Bjerrk]

I suspect the trouble with getting them working in an IBM model M might be from the thicker rubber sheet over the membrane.

I suspect you're right, given that both Unicomp and IBM keycaps work with an F spring in the Unicomp keyboard. Luckily, those "blankets" are not essential for the operation of the Model M, as I understand it.

[NeK]

Very interesting. I too hate the stiffness of my model M. I always thought though that if it was light I probably would love it. What's so special about the springs of M/F ? Shouldn't be easy to order to spec, from one of the hundrends of manufacturers or something?

[Bjerrk]

Very interesting. I too hate the stiffness of my model M. I always thought though that if it was light I probably would love it. What's so special about the springs of M/F ? Shouldn't be easy to order to spec, from one of the hundrends of manufacturers or something?

Yeah, nothing about them is *that* special, I guess. It's fairly easy to estimate the spring constant and of course measure the diameter and length, but I don't personally have the tool to measure the wire gauge at home. Should take a few springs into the lab some day, I guess.

But yes, my thinking has been in the same direction, I just haven't been able to find any good prices for custom springs - you know of any?

[NeK]

I don't know any, but that is more of a procedure issue. If we find one, we can just send them a spring and tell them "I want an exact copy of that, ok thanks bye"

[Bjerrk]

I don't know any, but that is more of a procedure issue. If we find one, we can just send them a spring and tell them "I want an exact copy of that, ok thanks bye"

Alright, I'll take on the task of going to a mechanics lab and measuring what I can on the F springs Won't be this week though.

(The funny thing is, Ellipse of course knows the specs)

[gianni]

I don't know any, but that is more of a procedure issue. If we find one, we can just send them a spring and tell them "I want an exact copy of that, ok thanks bye"

Alright, I'll take on the task of going to a mechanics lab and measuring what I can on the F springs Won't be this week though.

(The funny thing is, Ellipse of course knows the specs)

There are a couple of guys that can help you?

Pylon has a github repository; if I'm not wrong he was going to sell a force / displament measure tool too.
https://github.com/bluepylons/Open-Swit ... e%20curves

https://geekhack.org/index.php?topic=112430.0

[JCMax]

I am looking to do a bolt mod and upgrade the controller on my New Model M. After hearing you talk about this I SO want to upgrade the springs too.

I was thinking of ordering extras from Ellipse, but it's $1.00 per spring/rocker and I don't want to have to spend $108 bucks for each key.

What kind of places were you thinking of that could custom make these springs, after figuring out what specs to give them of course?

[Bjerrk]

What kind of places were you thinking of that could custom make these springs, after figuring out what specs to give them of course?

Yeah, I was asking the same question a few posts back! The only places I've found so far were tremendously expensive.

[JCMax]

What kind of places were you thinking of that could custom make these springs, after figuring out what specs to give them of course?

Yeah, I was asking the same question a few posts back! The only places I've found so far were tremendously expensive.

, sorry. I must have missed it among the sea of posts! I am thinking about biting the bullet and ordering the extras from Model F labs. I can't find any place online where the springs can be made.

[Bjerrk]

, sorry. I must have missed it among the sea of posts! I am thinking about biting the bullet and ordering the extras from Model F labs. I can't find any place online where the springs can be made.

Have to admit, I ended up doing the same thing. We'll see how it goes when they arrive.

Something I've thought about in the meantime:
As I mentioned earlier, I had no problems at all getting a Unicomp to "work" with the lighter springs, but my old IBM Model M failed to buckle correctly. By now I've convinced myself that it's the heavy "blanket" in the IBM Model M that makes the difference. I have one of the thin Unicomp-made sheets that I can put in my old IBM Model M, so I can test it. It just feels weird to replace the parts of this old beauty

[JCMax]

Do you know of any good tutorials for how to swap out the springs? BTW, I am planning on trying it on my New Model M.

[NeK]

A (much) simpler way to measure the force of the key presses, is to put they keyboard *on* a good kitchen scale and measure the weight difference when you press the key. IMHO I think it is pretty accurate method.

[Seirin-Blu]

A (much) simpler way to measure the force of the key presses, is to put they keyboard *on* a good kitchen scale and measure the weight difference when you press the key. IMHO I think it is pretty accurate method.

If you do this you’re going to cause a moment/torque to form if the switch you’re pressing is at all off center. This is not a very accurate way to measure.