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We've recently been discussing the Yamaha AvantGrand hybrid piano in the digital forum and learned that the action is not actually the action from the 9 foot concert grand, but from a smaller grand, which means the key length is smaller. This caused some amount of consternation.

However, though 9 foot grands have a longer overall key length, what I'm not clear about is whether they actually have a longer length from the keyslip to the fulcrum. This is the dimension, if I understand correctly, that is important for making the back of the key not harder to play than the front. I read a website that seemed to indicate that this distance is a standard 10-3/8 inches.

There are two questions I don't know the answer to that I thought you might:

1. Does the distance between keyslip and fulcrum vary by grand size, or is it just the distance from fulcrum to the back that varies?

2. By virtue of their geometry are concert grand actions actually better than, say, the action of a 6-foot grand? In other words, does it make sense to wish that AvantGrand had used a 9-foot grand action instead of the smaller one they did use?

If you want, you can answer in the digital forum thread that starts "Presto: from a Kawai MP10 to a Yamaha AvantGrand..." Or here is fine too. Thanks!

1. As you will see from the illustration below,
the fulcrum is almost exactly at half the key length.
This ratio is unchanged (depending on each manufacturer's design)
whether it's a 4'6" model, or a 9' concert grand.

2. In a word, yes.
The key 'dip' is -again depending on manufacturer- between 9 to 10mm.

Imagine a 20 foot long piece of wood/whatever, hinged at one end.
If you were to press the other end down 10mm, it would still be virtually horizontal.
If it was only 6 inches long, the angle would be considerably steeper.

Another thing is that with longer keys, the 'balance' tends to be much better.

So the longer the key, the more playable/sensitive it is.

Excellent. Thanks for the insight!

Up to the point where the flexibility of the key makes it mushy. That happens in some old (ex-)players.

Also excellent. Thanks. I was kind of wondering if there was a sweet spot for key length. It seems like a very, very long key wouldn't be a good thing either, for exactly the reason you describe: at some point the wood bends enough to be a problem.

So is the consensus that the length of key associated with a 9-foot grand is pretty much as good as it is possible to get? Could a piano in which keys were designed from a more rigid material be made with longer, more sensitive and yet not mushy keys?

Food for thought.

True, BUT - old player pianos generally do not use the higher grade

wood found in quality concert grands.

gv, The point that the above diagram shows is the finger force required for equal dynamic play at different parts of the key. The key length will directly effect this ratio which can become an issue depending on the brand and quality of design.

I think, the length of the key is decided by finding a common usable down force ratio that fits the hand in a manner that contributes to practical techniques.

BDB’s point is well made. The keys on pianos like the Steinway Duo-Art grands had to be thinned to allow room for the vacuum tubes to pass through. This made the keys weaker and more flexible. The quality of the wood has little to do with this; old players—reproducers—such as the Steinway Duo-Art typically used wood of the same quality as was used on normal Steinway grands.

Long grands often have problems with bending and flexing keys which is why the action saturation point in concert grands can be reached well before it would be reached in a shorter piano. That long key lever simply bends more easily. In the bass section the problem can be exacerbated by the increased mass of the hammers and the flare, or offset, of the keys which allows the keys to twist fairly easily. The keys in longer pianos are usually made some taller to compensate for all this increased bending and twisting.

ddf

Although there is a limit to how tall the keys can be made before you need custom balance rail pins.

One would think that a thin layer of oriented carbon fiber applied to the top and bottom of long keys near the pivot could make them as stiff as desired.

I think we must be a bit careful about our words. Longer keys mean that the key ratio is less sensitive to changes in where the pianist's finger depresses the key. Perhaps that's what you meant by saying a long key is more playable/sensitive. However, we mustn't forget that longer keys increase the moment of inertia of the action, which, in many, if not most,cases might be considered to reduce the playability of the piano. Long keys are subject to more flex, as has been discussed.

Also, piano actions are not designed to achieve balance. The goal is to have a desired down weight along with a desired moment of inertia, all while providing sufficient hammer kinetic energy to provide the desired tone and volume.

I said that 'cos the OP clearly stated he was 'visiting' from the Digital forum,
so I said things in a simple way,
trying to avoid confusing the issue with gobbledegook.



I'm sorry, but I don't buy that theory.

I have put up shelves made from very cheap timber, that have supported,
for example, dozens of books, with absolutely minimum 'warpage/flex'.

The weight of the lever/damper/hammer is only a matter of a few ounces,
and even taking into account the rebound of the hammer going into check,
it still would not put any significant strain on the key.

The weakest point of the key is obviously where the balance pin hole is drilled,
but this is reinforced anyway by the key chase.

IF there is any flex at all in the key, it would surely be the minutest fraction of a millimeter?

The flex in long keys is not caused by the static load on the key, but on the dynamic load caused by the force of the pianist's finger. When a pianist strikes a key to play fff, the dynamic force applied to the key is many, many times the static load. This force results from accelerating the moment of inertia of the key/wippen/hammer assy. Think of it this way--the force of the pianist's finger multiplied by the distance between the finger and the key pivot is the dynamic torque applied to the key.

Key saturation is a well-known effect, which has been noted by lots of players and techs.













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Slightly OT maybe but here are some long piano keys:
http://www.youtube.com/watch?v=ct3MMyWjRhc

This is not theory; it is measured and documented fact. There are a number of studies—including one of my own—on the phenomenon called action saturation. Action saturation is the point at which the hammer does not start to move until front of the key has fully bottomed and its motion has fully stopped. Beyond this point striking the keys harder will not produce any further increase in acoustic power from the piano.

Action saturation is the result of the bending, flexing and compressing of the various wood, felt and leather parts of the action. The biggest contributor to action saturation is the bending and flexing that takes place in the keys and the classic examples are the Steinway Ds built back in the 1960s and 1970s (or thereabout) using Pratt, Read keys. With the action on the bench and with the hammers blocked it took relatively little force on the front of the keys to cause them to fully bottom, particularly in the bass section. With the action in the piano these keys would bottom out very noticeably before the hammers started moving with what could only generously be called mezzo forte levels of key force. Most of the bending and twisting took place in the keys.

Earlier concert grand keys had used both bottom plates and top plates (the top plate being located between the top of the key and the keybuttons) making the key lever taller and increasing its stiffness considerably. During this era Steinway removed the bottom plate to make room for their bottom roller and Pratt, Read removed the top plate because it cost a couple of dollars more. The result was a piano that ran out of power about half way up the hill.

Pratt, Read keys of the same basic design but, of course, shorter were used in the smaller Steinway pianos of the same era where they worked quite well. Because the key lever arms were shorter neither bending nor twisting—even though key flare is greater—were problematic and action saturation occurred at much higher levels of key force.

ddf