why not

[Laser]

I wonder how is that nobody came up with some modifications/replacements for the Cherry MX (linears - red or black models) springs to resemble Topre with respect to the rubber/bubble feeling. Of course without the capacitive capability (how much does this affect the feeling of the key?)

[Daniel Beardsmore]

Well, you have these:

[wiki]Alps integrated dome[/wiki]

However, those use conductive domes, the surface of which wears with time and loses conductance.

I guess you could engineer one to have an integrated [wiki]buckling rubber sleeve[/wiki] with a small metal spring at the base of the slider:

Integrated buckling rubber sleeve.jpg (161.74 KiB) Viewed 9783 times

[Laser]

Thanks for info - and nice drawing/idea But how about doing it inside/around the Cherry MX switches?
Is there no place for a rubber sleeve, "spiral" like springs and so on? No solution to circumvent the small space / stem contact?

[Daniel Beardsmore]

I posted full disassembly shots of [wiki]Cherry MX Green[/wiki] — I am not sure how you'd get a dome in there anywhere.

When you say '"spiral" like springs', I presume you mean something other than a normal spring, which is spiral-shaped … I'm guessing you mean a bird's nest type spring like in an [wiki]Oki Gourd Spring[/wiki]?

Space inside an MX switch is indeed a bit cramped.

[Laser]

Actually i was thinking of the spring which accompanies the dome in a topre setup, but your pointers are very welcome and inspiring.



Yep, the space is an issue; but maybe a sharp-angled rubber cone should fit instead of (or around) the normal cherry spring (?). Just thinking out loud, maybe some idea comes up. Also, a cherry stem could be shortened from below, i think, to free some space and not reach the bottom.

[Daniel Beardsmore]

What would the Topre 5 cN spring do for you in this case? It's not there for feel, it's there to affect the capacitance. (In the Alphameric switch design, they appear to have gone for a rubber dome with a capacitor plate pad attached to the bottom — more on that next week hopefully.)

Capacitance doesn't affect the feel of the key. Some manufacturers (Cherry and Key Tronic at least) referred to capacitive switches as "solid state", though you do have moving parts — you just don't feel, see or hear anything.

From what I understand, you want to put a Topre dome inside a Cherry switch to get the Topre feel without paying the expense of Topre or being prevented from having discrete switches — correct? I assume your intent to adopt MX switches is so that you can make this a reality fairly easily. It's not an easy proposition, and it opens you up to a serious problem: what is it that makes Topre domes feel different to other dome keyboards? Rubber constitution? Rubber manufacturing process? Dome shape? Dome thickness? Where would you source all the spare domes? It's not like it's feasible to sacrifice real Topre keyboards for them (though Mr Interface appears to have destroyed a Realforce keyboard for his switch sample kits, which was an odd thing to do).

If you're only thinking hypothetically (which I think is where you're at, here, realistically) there's no reason to use an MX switch, since it's so inherently unsuitable for your end goals.

[Broadmonkey]

What are you exactly trying to accomplish? To modify an MX switch to contain the same components (rubber and cone spring) as a Topre? or just to replicate the feeling?

If it's the feeling then I'd guess lubed ergo clears is the closest you'd get without going insane (modifying the internals of >60 switches is no easy task).

[Laser]

what is it that makes Topre domes feel different to other dome keyboards? Rubber constitution? Rubber manufacturing process? Dome shape? Dome thickness? Where would you source all the spare domes?

Exactly, what is that makes Topre topre? My assumption indeed is that there is a combination of rubber and the specially shaped spring, giving a semi-mechanical feeling (springy, but also rubber-elastic). Of course, it's just speculation at this point. But if a good rubber and some springs can be fit inside a cherry mx switch, the cost of producing that rubber could be quite cheaper than a whole topre keyboard.

So the idea is to "toprify" the feeling by adding a rubber "intermediate" layer between the cherry spring and the bottom of the switch. Somehow. And tune that until it feels good.

If it's the feeling then I'd guess lubed ergo clears is the closest you'd get without going insane (modifying the internals of >60 switches is no easy task).

Thanks, i'll keep that in mind

[Broadmonkey]

Have you ever tried O-rings? Also, this mod might be of interest to you: http://geekhack.org/index.php?topic=50632.0

[Daniel Beardsmore]

A Dell KB1421 membrane keyboard has a similar feel. Topre feels so different because the force curve is so smooth, rather like a sine wave. I have no idea quite what does that. The only theory I've seen to date is that membrane keyboards require certain dome characteristics for switch operation, that Topre don't require because they only need to develop 5 cN of force instead of the ca. 20 cN required by membranes. I remain unconvinced. What I do know is that dome feel is extremely inconsistent between keyboards. One person noted that it's very hard to obtain consistency from manufacturing process.

Considering that dome keyboards are by and large made as cheaply as is humanly possible, it's hard to imagine what a typical Chinese manufacturer could do if they were being paid to make a decent product.

[Muirium]

Hmm. My instinct is that you're after the impossible.

Topre's feeling is 100% from the dome. You can easily remove the springs from a few switches when you take a Topre apart, and then reassemble and compare. The difference is barely perceptible, but those keys won't work! The springs are really just for the capacitance sensors. In fact, their conical shape is a crucial part in how they show up, electrically, rather than affecting feel. So long as a spring is a spring – whether it is conical or cylindrical or some other shape – it obeys the same law. And is therefore linear.

What capacitative sensing gets you is the ability to choose the actuation point. Or rather the people who make the keyboard get to choose. All MX switches activate at a fixed 2mm of travel. Topre switches can trigger elsewhere, and are typically set higher up so you don't need to press as far to register. Otherwise, cap sense gives: longer life, automatic NKRO at the matrix level, imperceptible actuation bump, and marketing bragging rights.

Now, the key to Topre is its smooth tactility. Look at the sinusoidal nature of its force chart:



MX can do tactile, too. But its much more of a notch than a smooth curve:



You really feel the mechanical bumps on all tactile ± clicky flavours of MX. (Well, except maybe MX brown, where it's a bit weak, but still the same shape.) Topre's difference is the dome. And there's just not the room to fit anything remotely like that inside of MX. You'd need a different shape entirely, like Alps integrated dome, to make a discrete Topre-like switch.

Topre's moving in the right direction with the NovaTouch (which I'm on just now) by aiming for the wider mech market in price and cap mount compatibility. But if what you're after is a discrete Topre switch, I wouldn't hold your breath. That's not the simplest thing to fake. MX has many strengths, but this is not one of them.

[Laser]

Ok, so what i get so far is that the whole topre feeling is given by a rubber dome (Muirium), and that we don't really know how other *good quality* rubber dome would feel (Daniel) ...

[sth]

The "new" (Kalih?) Razer orange switches look to have a parabolic curve that lowers in resistance (looks like from the leaf spring) rather than a linear surface after the actuation point (like clears and browns). i could be seeing things but from the pictures it does not look quite the same.

it might be just a bit closer to topre than other existing MX compatible switches.

[Muirium]

Maybe that will make a difference.

Or Razer / Kailh are just full of bull baloney. Until now, Kailh's switches have been all about cheap. Razer was cunning enough to send the marketing clowns as a defensive ass covering action when they switched. But so far nothing real to judge.

Ok, so what i get so far is that the whole topre feeling is given by a rubber dome (Muirinium), and that we don't really know how other *good quality* rubber dome would feel (Daniel) ...

Correct. The domes in Alps Discrete Dome switches are quite nice too (I ought to pull out that board and compare the feel) so the Topre feel isn't impossible to clone. It's just impossible with just a slider and no dome.

[Laser]

Correct. The domes in Alps Discrete Dome switches are quite nice too (I ought to pull out that board and compare the feel) so the Topre feel isn't impossible to clone. It's just impossible with just a slider and no dome.

Ok, so who wants to 3d print some sharp-angled conical domes that would replace or cover a cherry mx spring?
(is it possible to 3d print rubber shapes?)

[Muirium]

See that dome, attached to that spring?


http://deskthority.net/wiki/Alps_integrated_dome

The space inside of MX for the spring, which is enclosed so you can't exceed it, is about the same size as that spring above. But the dome is so much bigger! Change a dome's size, and you'll change its properties, big time.

Domes are kind of like a buckling arch. The wider the arch, the easier it is to buckle. So a really tiny dome would have to be made from some very weak material to have the same critical force. And it'd be tiny, so you wouldn't feel it nearly as much anyway.

[matt3o]

yes, it is possible to 3d print a rubber-like material.

[Findecanor]

Ok, so who wants to 3d print some sharp-angled conical domes that would replace or cover a cherry mx spring? (is it possible to 3d print rubber shapes?)

You won't fit it in there. It is possible to 3d-print in a flexible plastic, but I doubt that the material would be as durable as silicone, which is used in rubber dome keyboards.
I would instead look for rubber sleeves from a used Mitsumi keyboard from the mid '90s, and try them under OEM-profile keycaps. (Cherry keycaps have the internal struts too low)

Another reason for Topre's appeal is that it is smooth: High precision in manufacture, lubed sliders and no contact mechanism. You could use lube and stickers in Cherry MX switches to get closer, but you won't get all the way.

BTW. My ideal switch would be a smoother Cherry MX Clear, where I think the force characteristics would best be implemented as a rubber dome with a short spring. The rubber dome would give tactile feedback at the beginning of the stroke without adding scratchiness, and the spring's shortness would give it a steep force curve, thus coming into play after the dome's tactile bump.

[Halvar]

To replicate Topre feel, wouldn't it be best to start with a high quality rubberdome board and replace the membrane by a PCB with conductive paths that build capacitors like on a Topre board, and some electrolyte under the domes?

[Muirium]

…start with a high quality rubber dome board…

Like a Topre! What else?

[Hypersphere]

Hmm. My instinct is that you're after the impossible.

Topre's feeling is 100% from the dome. You can easily remove the springs from a few switches when you take a Topre apart, and then reassemble and compare. The difference is barely perceptible, but those keys won't work! The springs are really just for the capacitance sensors. In fact, their conical shape is a crucial part in how they show up, electrically, rather than affecting feel. So long as a spring is a spring – whether it is conical or cylindrical or some other shape – it obeys the same law. And is therefore linear.

What capacitative sensing gets you is the ability to choose the actuation point. Or rather the people who make the keyboard get to choose. All MX switches activate at a fixed 2mm of travel. Topre switches can trigger elsewhere, and are typically set higher up so you don't need to press as far to register. Otherwise, cap sense gives: longer life, automatic NKRO at the matrix level, imperceptible actuation bump, and marketing bragging rights.

Now, the key to Topre is its smooth tactility. Look at the sinusoidal nature of its force chart:

Spoiler:

MX can do tactile, too. But its much more of a notch than a smooth curve:

Spoiler:

You really feel the mechanical bumps on all tactile ± clicky flavours of MX. (Well, except maybe MX brown, where it's a bit weak, but still the same shape.) Topre's difference is the dome. And there's just not the room to fit anything remotely like that inside of MX. You'd need a different shape entirely, like Alps integrated dome, to make a discrete Topre-like switch.

Topre's moving in the right direction with the NovaTouch (which I'm on just now) by aiming for the wider mech market in price and cap mount compatibility. But if what you're after is a discrete Topre switch, I wouldn't hold your breath. That's not the simplest thing to fake. MX has many strengths, but this is not one of them.

However, the displacement of the switch takes place over time. The way the switch feels to us when pressed requires that we take time into consideration: i.e., the concept of impulse -- the change in linear momentum over time.

[Laser]

First, even with some delay - thanks everyone for your detailed input and pointers.
Broadmonkey's reference to the "trampoline mod" made me try it on a few switches, and i like the result.
And, embarking on it, i'd also like to "smoothen" the switches. Therefore, my next question is: where can i get a good, but not-so-expensive lubrification grease, ideally from Europe?

[Muirium]

I'd also like to know. Krytox is the stuff you hear about, but it's costly.

[Hypersphere]

Regarding lubricants, you might look into a comparison among lithium, molybdenum, and teflon varieties of grease, but it seems that most recently teflon-based lubricants (such as Mech2 from EK or Krytox from Dupont) are the ones favored for keyboards.

[Broadmonkey]

The Mechlube from Elitekeyboards is for stabilizers, not for lubing switches! The_Ed did just that, and it was reportedly horrible! This also goes to say that you can't just use any PFTE/teflon, silicone or whatever grease. Viscosity is of a really high importance as is the reason why people just don't use krytox grease, but uses a mixture of both the grease and oil.

I have lubed a fair few switches with a mixture of Krytox 203 and 105, and even though it is some of the best grease/oil for the job (so far), it is still easy to fuck it up. Too thick will make it sloppy, too thin and it will run off the stem or not have a big influence. This also goes when you apply a perfect mixture of grease/oil, too thick and it ruins the switch, too little and the difference is negligible.
I would recommend not taking the cheapskates route and instead just get the real and tested krytox lube in the first place, especially since it can be really hard to remove the lube afterwards, so you might end up with a bunch of ruined switches.

[Findecanor]

EliteKeyboard now has also a lower-viscosity MechLube 2 for switches.

[Hypersphere]

Yes, I meant MechLube 2 when I said Mech2 from EK. Even so, I think that Broadmonkey is saying that a properly done custom mix or the right type of Krytox is needed.

[Findecanor]

Oh, I interpreted him differently. The_Ed's experiment was about two years ago.

[Laser]

Well, little update - i tried the trampoline mod using ~1mm rubber discs with my Ducky TKL (which has 65g springs and mx brown stems, and a plate which allows for switch opening/modding). It works great - bottoming out (which i do a lot) becomes much nicer to the fingers, and *that* noise is also muffled. It feels especially nice when I hit the same key multiple times.
I keep thinking that a degree of sponginess in a somewhat "taller" rubber material would really top it - or something like small cones, ... micro rubber domes that can fit into the bottom of the switch? (and we're back to the topre feeling discussion).
But the combination is already excellent.

[Laser]

I just saw this, i find it quite relevant (and i do have a blue alps keyboard!)

http://geekhack.org/index.php?topic=588 ... msg1347946

I hope it's allright to also quote / post image here:

I recently modded some blue Alps with some rubberdomes instead of the spring to enhance tactility. I also removed the click leaf while I was at it since it only produces unecessary noise. Feels a lot better now, almost like Topre!

IMG_0813s.JPG (115.86 KiB) Viewed 8833 times