RE Leverage

[Kenneth Sloane]

                      Subject:                              Time:  11:04 AM
  OFFICE MEMO         RE Leverage                           Date:  8/13/95

-----------ORIGINAL POSTING-------------

Is it another symptom of incorrect leverage if you have a piano in
good regulation, with hammers correctly bored,  but the dip is too
deep?  To have 1 3/4" blow and .025"aftertouch, the dip has to be
over .400".

---
vince mrykalo  rpt

-----------------------MY REPLY---------------------

Vince- If you have a piano with "high leverage" shanks (17 mm distance between
knuckle core and action center) and an action with a key ratio close to to 2:1
(or at least 1.9:1), you will probably have an action that "wants" to have key
travel in excess of 3/8". Plain and simple, you are using levers that give
less hammer travel per unit of key travel. I agree with Stanwood's reply that
you can "cheat" on after touch to reduce the key travel. Be reminded that you
only need enough after touch to bring the jack behind the knuckle during
playing so that rebounding does not occur.
Also be reminded that pianists don't seem to mind keyboards with key travel
over 3/8" as long as the piano feels "even". The key travel can even vary
throughout an action as long as it does so gradually. Many fine regulators
compensate for string height irregularities in pianos (many pianos have
greater string height in the middle than on the ends) by gradually changing
key travel to give a uniform after touch.

And to reply to a comment David Stanwood made to your question. In regard to
the theoretical, straight-line relationship between the wip action center,
capstan/wip contact point, and the key fulcrum. I thought
David posted some conclusions recently about changing the key ratio on a
piano. If my memory serves me correctly, the conclusions indicated that as the
ratio was taken closer to 2:1 (at least with this piano), the "straight-line"
relationship improved, causing a reduction in friction along with the increase
in leverage. I think, David, that you said the opposite in your reply to
Vince's posting. I know just recently I changed the key ratio on one of our
pianos at Oberlin to get more leverage (changed key ratio on average from
about 1.84:1 to 1.93:1) and reduced friction a couple of grams in the action
also. There was actually visible skating at the capstan before the move and no
apparent skating afterwards. However, I do not know if getting the ratio
closer to 2:1 will always improve the "straight-line" relationship.

Ken Sloane, Oberlin Conservatory