At this point I haven't measured any pianos other than my own at 28-5/8" or 730mm
Next I'll try more weight and if that doesn't work I'll try a softer foam.
I have a lot to learn about pianos. Is that typical to have a 2 mm crown?
Hello, is a grams.cm mesasure useful for you ?
What noticed Pfeiffer is that it is not efficient enough to just put weights on the keys, even heavy one.
He conclude that the energy provided may begin to flex a little the action parts for the piano to be efficient.
SO there is an impact notion to take in account.
Hopefully the level at which this situation arise is not very high . it seem to be above 300 g.cm that the energy provided to the hammer is less absorbed .
(for instance with 100 and 200 grms.cm the action "ratio" is reflected in the hammer work, 100 grms >5.5% "rendering" (efficieny)
200 grms.cm > 4.5% , even less than the first
300 gms > 9.8 % there is a sudden raise in efficiency at some point.
300 g.cm is a 300 g mass falling free from 1 cm height (if I understand well, so a mass just layed on the key , the key have 10 cm dip)
600 g.cm would be the work done by the same mass at 1 cm from the key, (??) 200 g.cm gives a "p" nuance, which is not strong. (400 g =mF , on actions build before WWII)
He state that the foam must be sof enough to counte rthe initial resistance of the keys and avoid rebouds.
What Pfeiffer state is that the catapult effect arise above 200 g cm at the condition there is enough speed
I believe that a pounding machine may be strong enough to raise that point where the impact is not adsorbed much by the action cloths and wood resiliency. I doubt a softer foam will help in that matter but I seem to understand what you think, it could compress then release the energy, it seem difficult to setup and probably you will need even more mass then
When the piano is played we have a short impact very soon when raising in dynamics, then if we want to play stronger we need to accelerate even more once the compressed action is felt under the fingers , but sur the pianist use the "free fall" of its arm and forearm, (and shoulders )that makes a lot of weight
THe crown in keyboards is not always find, but the rules we use to straighten the keys with paper punching are flat, with 1mm crown, or 2mm crown.
I for one tend to use the 1 mm one when all parts are new, as the center of the keyboard is the first region that flattens,
When the piano have played enough and the cloths under the balance are compressed it can be dressed flat.
But Steinways, (for instance) induce a curved key level by construction. on grands about 2 mm , on verticals 1 mm.
It could be done for visual reasons as well.
Good job ! in the end that should be a height + weight question.
The sharps are more heavy to move very often
The keyboards are noy at a so wide range in heigh as 2.5 inches but this point may be secondary.
PS, when we say a keyboard have a 50 gms "down weight" that just mean that the parts move slowly up when that weight is installed on the key.
Schimmel state about a weight they use to verify the action is well regulated and that play all notes at ppp level - an octave range I believe, not sur ethey give the exact mass of the thing.
Playing p, or ppp is not helping a lot to break in an action, but too much is probably not good either. mF sound good to me (?)