I think that the main problem is that the string lengths are different so you would need a different bender for each string. You can get away with it on a guitar with a whammy bar because the amount of tension adjustment is the same on the same length of metal. But with the changing length of string you would need a different amount. There is maths to it but it is reasonably well established.
The simplest approach is to do this with a grand, like the fluid piano. This uses delrin shoes to change the speaking length. If you listen to the piano ragas played by Ustav Lai you get a sense of what is possible https://www.youtube.com/watch?v=X7ti6HUX5xQ http://www.thefluidpiano.com/ But each string is adjusted in real time with no sense of "go and return" - it's a movable bridge effectively. And that hasn't been done with the FP. (Yes, I want one too)
For a "whammy bar" you'd effectively you need two positions (higher tone and lower tone) with a mechanism for locking them in place when done. On a guitar it is done by the higher tension in the spring holding against the tension in the string. Adrian Legg gets pedal-steel style bends+holds by using Keith d-tuners on his ovation (or whatever he is using now, I don't know). https://www.youtube.com/watch?v=OKctepuGY38 (Midwest Sunday, a classic if you don't know it). (I use Legg's trick and have d-tuners on several of my ukuleles, including nylgut ones)
So with the much greater tension in a piano string that with a guitar, that kind of change the length would be hard to maintain. Perhaps the mechanism that powers the Gibson self-tuning guitars could be used in principle but the problem is the tension required - you would need a seriously heavy duty stepper motor on each one.
An alternative would be to change the speaking length of the string - like an infinitely adjustable capo - this is how (I think, can't tell for sure) the guitar like things that sound like electric saws in Metheny's Orchestrion are done - pulley-rollers that push against a metal surface to change the length. But again, you would need one for each string.
Another approach (one I've not seen) would be to get a cam that rolled over the speaking string, but I worry that would make it sound like a jawari (sitar bridge) when in use. Mind you then you'd have a piano sitar which would be cool in an entirely different way.
Date: Fri, 9 Jan 2015 11:56:50 -0800
Subject: Re: Triple play again
As a mechanically challenged person, how hard would it be to build a pedal on a piano that did bend the notes when you stomped on it? Seems possible for at least the higher strings (if not the really heavy ones).Kevin
On Fri, Jan 9, 2015 at 11:52 AM, Ivodne Galatea <email@example.com> wrote:
Till now you seriously considered yourself to be the body and to have a
form. That is the primal ignorance which is the root cause of all trouble.
- Ramana Maharshi (1879-1950)