I totally forgot. Last time I wondered, why the black keys play okay near the fallboard, but the white ones are bad, I did some "scientific" research. (Without disassembling my keyboard action):

The red and black pile are the same distance away from the fallboard, and the key-downweight is about similar. But the grey pile is sitting on the white key is way heavier than the blue one. Therefore I am quite sure, my subjective impression is objective correct.

A laid back pivot point for the black keys is the only conclusion.

    I tried this on my ES920 which also has the RH-III action. I also found the black keys are easier to play near the fallboard than the white keys.

    I've never noticed a problem playing deep into the white keys. Just messing around a bit it seems like a Bb chord played with pinky and thumb on the Bbs and fingers 3 and 2 on the D and F is a worst case scenario:

    Playing the whole chord feels fine. If I weren't thinking about this issue I don't think I'd notice at all. If I play the notes one at a time the D and F feel a little awkward. But I can't tell if it's just because I'm now aware of the weight difference or if there's really an issue here!

    I'm away from home so I can't compare on my acoustic piano right now but I'm eager to do that when I get back!

      WieWaldi I made some calculation using your test data and measurements of distance using the picture of the action. The result does support the black keys' pivot point being staggered back by 15mm or so.

      On the other hand, this photo of the RH3 action still does not show that. Instead, it show that the weight plates for black keys are different than those for the white keys. To get to the bottom of this, I guess we either need you to take your piano apart 🙃, or we could ask @KawaiJames?

        rogerch I'm away from home so I can't compare on my acoustic piano right now but I'm eager to do that when I get back!

        I was just reading an article analyzing digital piano actions. The author said touch weight (measured by putting static weight on the key) only matters when playing the keys very softly (or at very low velocity). When playing more forcefully (or at high velocity), what matter more is moment of inertia. The higher the moment of inertia, the more difficult to get the key to move at higher velocity, the heavier it feels when playing louder.

        Digital piano action usually have low moment of inertia (with the exception of wooden full length actions like Kawai's Grand Feel), but higher touch weight. So it feels slightly heavier when playing soft, but not heavy enough when playing loud.

        Acoustic piano action have high moment of inertia, but lower touch weight. So it feels lighter when playing soft, but heavier when playing loud.

        @rogerch I am eager to hear what you find out when you get a chance. Thanks!

            iternabe @rogerch I am eager to hear what you find out when you get a chance. Thanks!

            Yeah me too! Probably not until Wednesday night California time though!

              I'm home! I compared my 5'7" acoustic action with my ES920 action. On both actions the white keys feel harder to press right up against the fallboard than at the front. On the ES920 the difference between the front and back of the key is more pronounced than on the acoustic.

              On the ES920 the black keys feel harder to play right up against the fallboard. On the acoustic it doesn't feel different between front and back.

              Interesting! Practically speaking though I don't think it matters as I've never noticed issues when playing close to the fallboard on either intrument.

              12 days later

              iternabe
              The pivot on the VPC1 also is shorter than on the RHIII action of the ES920 or MP7SE. However, a seesaw action design like on the VPC1 is superior to a folded action design, so pivot length is not the only thing that matters.

                  sweelinck However, a seesaw action design like on the VPC1 is superior to a folded action design, so pivot length is not the only thing that matters.

                  This is something I have read a lot over in the other forum. Still I don't see a reason why this should be true. I mean, physics is physics and it is all about levers and weight and how the mass accelerates. If a seesaw design would be superior, the difference between Kawai wood actions and the Roland's would be night and day, but it isn't. I mean if mechanical principles would say so, the difference would be dramatic.

                  Kawai wood actions are better than folded designs, but not because of the seesaw design - it is because of the materials used and because it is constructed more costly. And because the longer pivot point - at least longer than most folded actions.

                      WieWaldi If a seesaw design would be superior, the difference between Kawai wood actions and the Roland's would be night and day, but it isn't.

                      Well, there are many parameters that go into action quality, and there is a substantial subjective component, but for me that leads to finding Kawai's seesaw actions to be significantly superior to Roland's folded actions.

                      A seesaw action has gravity from counterweighting of the other side of the balance rail to participate in resetting the key after release while a folded action must exclusively use springs.

                          sweelinck a folded action must exclusively use springs.

                          I don’t thinks the PHA-4 action in my Roland has any springs.

                            15 days later

                            iternabe
                            Do you know the pivot lenght of the Fatar TP/400Wood action?

                                harri no, but if there is an accurate side profile picture I should be able to take a measurement.

                                • TC3 likes this.

                                  @harri @TC3 Assuming the picture is proportionally accurate, here it is. Pivot length of FATAR TP/40WOOD would be 201 mm.

                                  • TC3 likes this.

                                  Is the Kawai RHCII any different than the RHC?

                                  Enthusiastic but mediocre amateur.

                                  The TP/400wood should be an upgrade of the TP/40wood but I have no idea what they have changed
                                  I am looking for the technical specs but have not found any thing yet
                                  Is there anybody who owns an DP with TP/400wood, and if so is there a description in the manual about the action?

                                  hebele

                                  I remember reading that pivot length in acoustic pianos also varies a lot. I wonder, for example, if baby grands have shorter pivots.

                                  Generally, they do. Concert grands have the longest keystick length and longest pivots. With a grand of fixed length, you only can lengthen the keysticks or pivot if the rest of the piano is shorter, so longer keysticks on a smaller grand would trade off soundboard area and string length to some extent. Uprights do not have that particular limitation.