This is in the "just musing" category . . .

We assume that a DP key has a _pivot point_, and that, as you play closer to the pivot point, the leverage of your finger changes. (That is, the key becomes hard to press down, near the pivot point.)

So the distance from the end of the key, to the pivot point, is an important parameter. And the longer it is, the deeper the DP has to be, and we know about those trade-offs.

But there are _thousands_ of "linkages", known to mechanical engineers, that let a designer _simulate_ a longer lever than is physically present. One could (for example) devise a linkage that would let a key move _straight down_, along its whole length:

. . . simulating an infinite-length keystick.

I can see that there's a trade-off between the (relative) simplicity of existing key mechanisms, and a mechanism with multiple joints (including possibly sliding joints).

. . . With modern materials and production techniques, is such a key action feasible ?

. . . Might it be cost-effective ?

. . . Has anyone (or any manufacturer) tried to make it work ?

This idea is on the other end from "haptic keyboards" -- there's no software at all.


Thanks --

I do recall that some synth boards do have a straight up/down path for the keys, making for the same keypress weighting front to back.

But I will say that on several of my laptop and desktop trackpads have simple lever pivots, making it nearly impossible to press down from the top half of the trackpad; it's such a usability compromise you'd think they would move on to one of these different joint systems.

I imagine it would be impossible mechanically. Electrically, you could have "variable power steering" towards the pivot end of the keyboard.
On all 88 keys!
I'd been thinking the same as you. And on cars, differential gears reflect a not dissimilar age old problem.
When turning right, only the right driving wheel grips; the other freewheels. Since the car tends to lift at the right, traction is partially or completely lost from the driving wheel.
You try solve that one! But there'll be an electrical solution.

Yes! Peter is on the right track.
FOUR WHEEL DRIVE PIANOS, WITH POWER STEERING AND TRACTION CONTROL !!!

Probably the mechanical designers would want to avoid any sliding things.

When Casio first mentioned their PXS series and it had such a short key length I secretly hoped that they had attempted something of that kind, but, well, it's just another short distance to the pivot. It can't be an impossible problem - can get people onto the moon but can't simulate a longer pivot? No, that just isn't right. Come on, NASA, get cracking on it!

Maybe the moon thing is easier.

To some extent they are simulating a longer pivot by the vertical offset between the actual pivot point and the key surface. (Which of course exists in acoustic piano keys too due to their thickness.)

But the effect is quite small. And if you make a huge offset it then also makes the tip of the key move front to back more.

Related:
https://forum.pianoworld.com/ubbthre...ion-thread-lets-do-this.html#Post3021455
https://forum.pianoworld.com/ubbthre...ion-thread-lets-do-this.html#Post3021598

I already posted this idea about 12 months ago I believe... I even registered the trademark:

InfinitePivot

Sorry, it was actually 15 months ago, and it was actually CyberGene:

http://forum.pianoworld.com/ubbthreads.php/topics/2866428/burkey.html#Post2866428

And then blatent trademark infringement here:

http://forum.pianoworld.com/ubbthreads.php/topics/2985278/clothearednincompo.html#Post2985278

Actually clothearednincompo may have beaten CyberGene to the idea by a couple of months:

https://forum.pianoworld.com//ubbthr...ure-of-dps-in-the-2020s.html#Post2835990

I think a lot of us have had this idea (and posted it) over the years here, I bet the first few mentions probably predate the tenure of many of us!

Peter, I wondering what aspect would impossible (or difficult from a physics perspective) here? Most buttons and keycaps out there have a linear path of motion. I suppose it's mainly a problem of complexity and cost associated with having ensuring even pressure along rectangular shaped keys, but that's kind of a mechanical tolerance issue, a solvable problem...just maybe not economical or easy to build.

I had in mind some laptop keyboard where under each key, there is sort of X which lower a side of the key if we press it at the other side.
Such an action can be difficult to build then more expensive, perhaps inefficient (a key is quite long compared to a laptop key) and can interfere with the touch/feeling.

Like a scissor or butterfly switch? Let us all agree that Jony Ive should not design the next DP action

Yes, a scissor.

I didn’t know about the scissor vs. Butterfly switch

Yes, I expect he'll be convicted of crimes against humanity if he makes any such attempt!

Is the advantage of the scissor less friction than the butterfly?

On a «InfiniteLength » piano action, the scissors will press the opposite side down which is important if we want the hammer pushed.

On the butterfly, the opposite side may not have enough force to push the hammer and we could have a key which is not horizontal.

I thought of using a scissor mechanism too. It does have sliding contacts, but the weights on a digital piano have a small amount of sliding action as well. Noise may be an issue with the increased number of bushings that can go loose.