Thank you Ed, I am trying today to understand the hardening or not hardening if the iron.
I suggest that the string is well when it creates it place in the iron, but on a very small deep.
Irn specialist told me that the iron used for plates is homogenous, so, unless some hardening have beenn done at the factory, shaping the capo would not lend to a more fragile metal, while I heard that theory more than once (an external layer being harder than the inside)
I am unsure of what you mean with V shape, in my view most capo have that V shape, simply the top of the V is a small 2-3 mm max rounded surface - SOme pianos have a larger one and inverted U shape, but they are not the most common ones.
I am investigating on eventual hardening, knowing it can be detrimental to tone, I just wonder if a light hardening is possible, I was said that heating old semi phosphorous iron can lend to deformation s I certainly will not try that on a real plate.
If you mean shaping the capo in V with a sharp edge, can you tell me how deep the strings make imprints then ?
ABout quadratic effect, I first have seen the term in the Pianotec software, Philippe Guillaume , the designer and developper, explained me it was a pure frequency related to the speaking lenght, and created by the rocking motion of the bridge. making a 4th partial pitch above a certain level of power. A non linear effect
I may admit I hardly perceive it in real pianos, but I perceive a tone change occuring around the action saturation level, that allow to shape a different tone, I always wondered if this was related.http://www.forum-pianoteq.com/viewtopic.php?id=2269