Lighter Model F Spacebar - The no-disassembly Ghetto Mod

[Bjerrk]

I am sure many of us have been through the ordeal that is Model F XT disassembly and reassembly.
It's a pain to get everything back together, especially the dreaded spacebar switch:


Photo courtesy of JBert.

JBert created a brilliant guide guide to bending the spacebar stabilizer wire to lighten the veeery heavy spacebar of e.g. an IBM Model F XT.
Perhaps you've tried that and want an even lighter spacebar, or perhaps you can't be bothered with the whole disassembly and reassembly at all.

I was in the former situation. I wanted an even lighter spacebar. mmm jokingly suggested that I could just place something heavy on top of the spacebar. It then occurred to me: Why not just put something heavy inside the spacebar?

I then proceeded to turn the assembly over, place four screws (total weight: approx 8g) inside the hollow space of the spacebar and started squirting hot glue into the space with a glue gun. This was possible without taking the assembly apart - the tip of the glue gun fit nicely in the space between the spacebar and the plate.

Since I suck at taking pictures, this is as good as it gets:



You can tell that there are a couple of screws in there along with some solidified hot glue. None of that is visible with the case back on, of course.

And it worked really well! The spacebar is now pleasantly light - or at least non-heavy!


(Disclaimer: Perform at your own peril)

[Yasu0]

THIS YES. That FXT space bar is beastly.

I will try this on my some of mx blacks caps to "turn them into mx reds" too. Maybe some of that silicone caulk in a tube would work I wonder.

[Go-Kart]

So jenk, yet so easy! My first F is in the post. Looking forward to seeing what the fuss is all about; with the key feel ...and this allegedly heavy space bar!

[Yasu0]

Yes physics don't care about jenkiness!

Poor overpriced XT needs so much to get on par with a $90 unicomp M101: Build/buy usb adapter, fix spacebar weighting, figure out where to prog F11 and F12, adjust to lack of home key bumps, adjust to strange modifier key position, adjust to vertical return key...

Not shillin, just sayin.

[Rhododendron]

Very elegant solution! I wouldn't have thought of that. IMO the best method yet, as some people seem to have damaged the wire while lightening it. I'll definitely try this on my F.
While we're at it: Does somebody know from experience what replacement foam works best in an AT or XT?
There are countless threads, in some of which they say their board starts chattering after the replacement (??). But there must be a viable solution, or else people wouldn't be doing it, right?

[mmm]

I'm amazed at how elegant this turned out! Did this have any affect on the sound of the spacebar? Does the spacebar seem sluggish in any way, since more mass has to be accelerated (or is this not the case due to physics I might not understand? )

While we're at it: Does somebody know from experience what replacement foam works best in an AT or XT?
There are countless threads, in some of which they say their board starts chattering after the replacement (??). But there must be a viable solution, or else people wouldn't be doing it, right?

For my AT I used some foam off ebay. A little pricey compared to just buying foam, but I didn't have to use any mental capacity figuring out which foam to buy or spend time cutting holes, which was nice. No chattering whatsoever.

[Bjerrk]

Did this have any affect on the sound of the spacebar?

It sounds tremendously thocky to me, but I have to admit I didn't pay that much attention to how it sounded before.

Does the spacebar seem sluggish in any way, since more mass has to be accelerated

Let's get physics-y! (and everybody went "Yayy ... ")

Recall that, above the buckling point, the spring behaves essentially like a Hookean (i.e. linear) spring.

Near the top of the switch (let's call the position x), the force on the spacebar has two terms: One due to the spring and one due to the weight of the spacebar:
F = k * x - m * g
with k being the spring constant, m the mass and g the acceleration due to gravity (approx. 9.82m/s² in this particular region of spacetime ).

Now, I'd like F to be on the order of 60 grams times the aforementioned 9.82m/s² (i.e. it should "feel like 60 grams" or thereabouts).

Anyway, the acceleration of the spacebar is then of course given by good ol' Newton: F=m * a, so
m * a = k *x - m * g
or
a = (k/m) * x - g.

The return acceleration thus only depends on the ratio of the spring constant to the mass of the spacebar.
It follows that the two following situations are equivalent in terms of acceleration:

1) Get a lighter spacebar by reducing the spring force by e.g. half (k -> k/2), keeping the spacebar mass the same (m -> m).
2) Get a lighter spacebar by keeping the spring force the same (k -> k) but doubling the mass (m -> 2m)

At least that's the "lowest order approximation". If there's significant friction in the switch, things change a bit, but my particular XT seems pretty smooth

Also, subjectively (yikes), it doesn't seem sluggish to me

[Go-Kart]

I think a nerd of any stripe can appreciate a good bit of physics.

[Bjerrk]

Very elegant solution! I wouldn't have thought of that. IMO the best method yet, as some people seem to have damaged the wire while lightening it. I'll definitely try this on my F.

I'll say one thing, though: remember to weigh whatever things you put in there beforehand, so you know how much you're reducing the force
Turns out that hot glue doesn't weigh all that much by itself. A whole stick of glue - which, admittedly, isn't that big (that's what she said? ) - only weighs 10g (at least the ones I have). That's why I added a few screws.

Looking forward to hear the results if anybody decides to try this!

[Muirium]

Honestly, I quite like the heavy spacebar on my AT. Gives it character, and helps to remind me I’m on an unusual bottom row. The extra long size of the spacebar is what actually bugs me. I’d only ever ANSI mod, and even then, the stabiliser story doesn’t look convincing.

Not shillin, just sayin.

That’s fighting talk! You bring your creaky Unicomp and I’ll bring my solid metal Kish, and we’ll resolve the matter in the manner of gentlemen.

I’d bring an XT but I sold mine because they’re not that great.

[Bjerrk]

Honestly, I quite like the heavy spacebar on my AT.

You're free to start a "Status quo spacebar" thread

[Muirium]

You excised the bit where I groused about it being extra long, mind. We just have different gripes. Its annoyance contains multitudes!

[Bjerrk]

I'm sure I can come up with a similarly ghetto spacebar decimation mod. Now, where's that can opener ...

[Rhododendron]

For my AT I used some foam off ebay. A little pricey compared to just buying foam, but I didn't have to use any mental capacity figuring out which foam to buy or spend time cutting holes, which was nice. No chattering whatsoever.

I'll look into those premade foams. Thx!

I'll say one thing, though: remember to weigh whatever things you put in there beforehand, so you know how much you're reducing the force
Turns out that hot glue doesn't weigh all that much by itself. A whole stick of glue - which, admittedly, isn't that big (that's what she said? ) - only weighs 10g (at least the ones I have). That's why I added a few screws.

Looking forward to hear the results if anybody decides to try this!

I had this idea floating around in my head yesterday of buying one or two long, thin steel/brass rods to fill the entirety of the spacebar's length. The spacebars weight is known I presume? So then, come up with a target weight, like 70-ish maybe, look up what diameter of steel they sell at the hardware store, and calculate how much you need exactly... maybe taking a bit of glue into account as well.
Easy enough, right

[mmm]

Does the spacebar seem sluggish in any way, since more mass has to be accelerated

Let's get physics-y! (and everybody went "Yayy ... ")

Recall that, above the buckling point, the spring behaves essentially like a Hookean (i.e. linear) spring.

Near the top of the switch (let's call the position x), the force on the spacebar has two terms: One due to the spring and one due to the weight of the spacebar:
F = k * x - m * g
with k being the spring constant, m the mass and g the acceleration due to gravity (approx. 9.82m/s² in this particular region of spacetime ).

Now, I'd like F to be on the order of 60 grams times the aforementioned 9.82m/s² (i.e. it should "feel like 60 grams" or thereabouts).

Anyway, the acceleration of the spacebar is then of course given by good ol' Newton: F=m * a, so
m * a = k *x - m * g
or
a = (k/m) * x - g.

The return acceleration thus only depends on the ratio of the spring constant to the mass of the spacebar.
It follows that the two following situations are equivalent in terms of acceleration:

1) Get a lighter spacebar by reducing the spring force by e.g. half (k -> k/2), keeping the spacebar mass the same (m -> m).
2) Get a lighter spacebar by keeping the spring force the same (k -> k) but doubling the mass (m -> 2m)

At least that's the "lowest order approximation". If there's significant friction in the switch, things change a bit, but my particular XT seems pretty smooth

Also, subjectively (yikes), it doesn't seem sluggish to me

Ah so it is indeed mathematically speaking more sluggish! Since doubling the spacebar weight reduces F significantly less than halving the spring force. A generous approximation would be that the spacebar was already 8g initially (but realisticly speaking probably much less?), thus the acceleration has been halved, while the total force is nowhere near halved!

Also the entire machine has now become 8 grams less luggable. Keep that in mind when bringing it to the library.

[Muirium]

Anyone using a Model F in the library deserves it around the head. Bad form! People are reading here! Take your bloody racket elsewere.

(This from a Model F lover. But still, that's between consenting adults…)

[mmm]

Anyone using a Model F in the library deserves it around the head. Bad form! People are reading here! Take your bloody racket elsewere.

(This from a Model F lover. But still, that's between consenting adults…)

Just feels weird to attach another keyboard to the 5155. How else would he get work done??

[Bjerrk]

Anyone using a Model F in the library deserves it around the head. Bad form! People are reading here! Take your bloody racket elsewere.

I'll make a note not to invite you into my library.

[Muirium]

You will know me by my silenced HHKB…

[Bjerrk]

Ah so it is indeed mathematically speaking more sluggish! Since doubling the spacebar weight reduces F significantly less than halving the spring force.

Ah yeah, that's true! You only need to reduce the spring tension by ~10-15% to go from e.g. 70 to 60g of felt force at the top of the keystroke, but you'd need to roughly double the spacebar mass. Good point.

Based on a quick calculation, you probably wouldn't want to add much more than 15-ish grams to the spacebar, before it would get noticeably more sluggish. (and that's based on the estimate of the spacebar weighing 8g, which we should still actually weigh at some point )


Does this mean I need to get another XT with a fresh, annoying stabilizer wire, and test the ghetto mod on that?

[Yasu0]

That’s fighting talk! You bring your creaky Unicomp and I’ll bring my solid metal Kish, and we’ll resolve the matter in the manner of gentlemen.

Doing my part spreading M gospel for those unwashed rubber gomers out there that would hear the word.

Mine board stayeth on mine mount. No creaketh shall be heard lest it be removed.

[Bjerrk]

[Muirium]

IS IT NOW? I HOPE YOU DIDN'T SQUIRT NASTY GLUE SPOOGE INSIDE A CLASSY PIECE OF KIT LIKE THAT.
>

[Bjerrk]

Oh, I absolutely did. Anything to anger the Scotsman.

The best part is that it is fully reversible - one of the advantages of hot glue.

[Palatino]

Honestly, I quite like the heavy spacebar on my AT.

I mostly like my XT spacebar too: it's good for slow, considered typing, when you have to finish each word with a THUMP of approval. But for when I want to type faster, I use one of the following two tweaks:

XT1.jpg (185.33 KiB) Viewed 5215 times

This is even jenkier than hot glue and screws, but it's more easily done and reversible in seconds. Two slim brass ingots sellotaped to either end of the spacebar with some foam underneath to prevent them knocking. Each weighs 13g so 26g overall extra weight to the spacebar, which is now medium-heavy. I bought slightly wider pieces too which were 17g each and experimented with all the combinations of one to four pieces (13g, 17g, 26g, 30g, 34g, 43g, 47g, 60g). 26g or 30g seemed to me to give the best balance between retaining the original feel of the spacebar whilst reducing its stiff feel. Going for all four pieces (60g) meant every other word the spacebar would stay depressed. Other weights worked fine but the highest ones made the bar a bit too loose for me: it would accelerate too quickly down, and at 47g not spring back up so nicely. Obvious caveat: it's not so attractive, but I don't mind that, plus I can remove the weights in seconds. Another caveat: I only ever hit the spacebar with my left thumb, and always underneath the B or N key, so the weights never get in my way. If you have a different typing style, it might be tricky to place weights on a section of bar you never hit.

XT2.jpg (143.9 KiB) Viewed 5215 times

Visually cleaner, but I imagine this is even more dependant on having a certain typing style: remapping Right Shift to Spacebar. Since I always use my right hand for spacebar, and never use Right Shift at all for Shift, this works fine for me. It takes a minute or two of getting used to it if I'm switching straight from the usual spacebar, but I can type almost as fast with this configuration.