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Meaning not the details, but what kinds of objectives do designers start out with? I'm talking about the design considerations that affect how the action feels.

(I got the idea for this thread from the posts on another thread about the different key dips for Steinway and Baldwin. I was wondering whether the different key dips were a result of all the other design considerations or the designer starting out by saying to himself "I think a key dip of _______ makes for a good action design.")

I read a bit of Kawai marketing blurb once that claimed they wanted to build the action so that the piano felt like water. I don't remember more than that.

Most modern pianos have some version of the Erard/Herz action. Most of these are patterned rather directly from the design Steinway adapted something like 150 years ago. Even the modern plastic actions such as those from Kawai and Mason & Hamlin are essentially Erard/Herz actions.

For the last 50 years or so the only alternatives have been the Schwander action most recently built by Herrberger-Brooks (then owned by Kimball) and the Pratt-Read action used by Baldwin (that was mercifully done away with when Baldwin essentially ceased to exist).

So…the basic action functions and geometry are more-or-less fixed. What are variable are things like hammer mass and the overall lever ratio. Years back—as in when I started out in this business—the de facto standard hammer travel was approximately 45 mm (1 ¾”) and key travel was approximately 9.5 mm (0.375”). Even then, of course, Steinway was a bit different with a published standard key travel distance of 9.9 to 10.0 mm (approximately 0.390”). With pianos like the Steinway, of course, this could vary considerably depending on where the action stack was located and in the end key travel would be determined by how much travel was required to ensure adequate key aftertouch.

As piano hammers became heavier over the years these specifications became some unworkable. To keep key downweight within reason increasing amounts of lead weight would have to be added to the front of the keys. This looks fine for static measurements but the amount of inertia makes fortissimo and fast repetition difficult. The answer was to increase (numerically) the overall action ratio (OAR). For a given hammer mass an action with on OAR of 5.5 (a hammer travel of 5.5 mm for every 1.0 mm of key travel) will have a lighter feel than one with an OAR of 6.0 (a hammer travel of 6.0 mm for every 1.0 mm of key travel). In general manufacturers have kept the hammer travel pretty much standard choosing instead to increase the key travel. This has, I think, pretty much reached its limits now with some actions requiring as much as 11.0 mm of key travel to function properly.

Simplistically, the variables the action designer has to work with are hammer mass, hammer travel and key travel. Still very simplistically, the there are several ways to go about achieving a given OAR; the hammershank length can be varied, hammershank knuckle can be moved closer to or further away from the action center; the contact point between the key capstan and the capstan block on the wippen can be moved and the key balance point can be moved. (Key length is mostly a function of piano length.) If a relatively heavy hammer is selected the OAR will need to be numerically lower and if a relatively lighter hammer is selected a numerically higher OAR can be used. For a given hammer travel and key touchweight the action with the heavier hammer will require more key travel while the action with the lighter hammer can get by with less key travel.

ddf

Thank you Del.

And now that somebody who knows what he's talking about has arrived...

Is there a good reason why hammers have been getting heavier?

(And at least now I have some clue about what was wrong with that piano I played that had no fortissimo, slow repetition, and a very sluggish and frustrating overall feel.)

These are objectives for piano action design:
1. Pressing the key makes the note sound.
2. The volume of sound is proportional to how fast the key is pressed.
3. The note continues to sound until the key is released.
4. There are no extraneous sounds such as double-striking.
5. This can be repeated quickly and reliably.
6. The response should be even from note to note.

[though not in a linear ratio, I suspect]

Uh Del, did you mean to say the opposite?

I also stumbled over this, Dale. I would think that the higher the overall action ratio, the more dynamic force is required on the key to overcome the inertia of the hammer, making for a heavier feel, not lighter.

Hello,

may I ask, if the key length, that is the distance between center pivot and key front, is specially of concern?

I had some thoughts about it and posted these and some images here:

https://www.pianoworld.com/forum/ubb...s%20compared%20-updated.html#Post1545456



Another remark for the volume:
The cinetic energy results from the squared velocity.
So the sound energy shold be the squared velocity.
However sound energy is not the same as volume. There are many different methods to measure subjective percepted volume, but I believe all have Fechner's law in common: The percepted volume is logarithmic to the sound pressure...
Complicated ....

But I think indeed there should be a partially linear relationship between percepted volume and velocity.

Thats what I think about it. Ok, I am a technician, but not a piano technician, probably you guys know more...



Peter

From physic laws follows: If OAR increases then the ratio (mass inertia)/(static weight) increases.

So, yes, it mass inertia aka dynamic weight is kept constant and OAR decreases then static weight increases.

If static weight is kept constant and OAR increases, then dynamic weight (mass inertia) increases.

The point of view is different depending from those parameters that are kept constant.

And it is only valid if the keys contribution to static weight and dynamic weight is constant or zero as it is the case for thin plastics keys.

Ok, complicated words, but simple formula:

Friction and key mass neglected:

W = static key weight
M = dynamic key weight respective percepted Mass inertia of key.
OAR = total leverage Key-Hammer.

M = OAR * W
W = M / OAR


Peter

Yes, but I my question was meant to be more about objectives that might not be a given so that a piano maker could make some kind of choice. In other words, I'm assuming each manufacturer consciously designs their action to have a certain feel.

Your formulas and words are misleading. The dynamic force is a result of moment of inertia and is not calculated by the formula you give. The static weight required to push down the key is a simple function of the masses at various points in the action, and the lever ratios through which they work. For example, mass ahead of the key's pivot point reduces the static weight felt by the pianist, and mass behind the key's pivot point increases the static weight felt by the pianist. Static force, or down weight as it is often called, is well understood by the piano community. Dynamic force, as caused by moment of inertia is not well understood, or should I say, not commonly well understood by the piano community.

My very good tech once told me that his job "wasn't brain surgery", but based on some of the posts in this thread I think it is!

Sorry thats a misunderstanding.

I did not calculate any forces or masses but relative magnitudes.

The dynamic force depends from acceleration and is impossible to calculate without additional parameters.
Its easy to calculate the energy: e = m*v^2 /2

If massinertia is not understood, then its impossible to understand a piano action.

To make it clearer:

OAR = (key-inertia measured in gramm)/ (key-weight measured in gramm)

Peter

Uh, yes, I did. My only excuse is that it was quite late and it had been a very long day.

I changed the appropriate words in the original post.

Thanks,

ddf

Most manufacturers do not design actions. They copy others.

Case in point would be upright actions. There are two methods of springing them that have been used in recent years, springs on the rail, and springs on the butt with a loop. The latter does not work as well, but is cheaper, so now everyone uses them. One could make a hybrid that would work better and be even cheaper, but nobody thinks about designing actions any more, so no one does that.

Your formula is still incorrect. First of all, the units of inertia are not grams, and key weight and key inertia are both independently adjustable with respect to each other and to the action ratio.

Oh, a variety of things I should think. Somewhere during the 1960s and 1970s a few builders discovered that you didn’t really need to use those really expensive and difficult hardwoods like maple or beech in their rims. Woods like “select hardwoods” were much cheaper and much easier to bend. The only downside was a moderate loss of sustain. This could be resolved by making the soundboards and ribs a bit heavier and stiffer. It doesn’t take much. Sustain improved but it was at the loss of power. The power issue was resolved by hanging heavier, denser hammers. That increased the touchweight to an unacceptable level so the overall action ratios started changing…and here we are.



Well, not necessarily. Even a nicely designed and balanced actions will play poorly if not properly regulated and balanced.

ddf

Piano action design, from the ground up, is a bit like brain surgery. Bringing a known piano action up to spec by testing, adjusting, and repairing it, or modifying it for a purpose; beyond my capability but not brain surgery.

Yes, it is. But there is generally not much that can be done about it. Key length is primarily a function of piano length. With a longer piano the speaking lengths of the strings are longer and the hammer strike points are further away from the front of the piano. Hence, the longer keys in the longer pianos.

One of the drawbacks to very short pianos is the significant change in touch as the finger moves from the front of the key toward the back of the key (keytop). There is always a change no matter how long or short the keys are it is just more noticeable with shorter keys.

Occasionally a maker of very short pianos will attempt to alleviate the problem by moving the key balance point back (away from the front of the piano). Knabe did this with some of their short pianos. Unfortunately, they did nothing to compensate for the change in geometry and the touchweight was quite low and the key travel was quite high. Repetition and control were both significant problems with this action. In the pianos I have encountered with this action setup I have compensated by relocating the capstans to change the overall action ratio to something within reason. This means modifying the new Renner wippens some—the capstan block has to be relocated—but the results are well worth the effort. I can’t see any over-riding downside to this arrangement and it does seem like an idea worth exploring in shorter pianos.

ddf