[CAUT] stack fit to keyframe

[Bob Hohf]

John,

This is a very interesting take on the scenario.  When you're the tech on
the spot, you'll certainly be free to change the bore and angle as your
solution of choice.  You've obviously spent a lot of time studying action
development.  I admire that.  I've always been fascinated by the main stream
and side roads of action evolution.  My favorite is the Lattice action
illustrated on p. 70 of "The Piano Hammer".  I actually saw one of these
once and all I could say was, "Wow, that's about as cool as they get!"  It
even worked.  But it's obvious why it never caught on. Somehow, I don't
think that lamenting the loss of the lotus-eating days of action design is a
good strategy for career development.  I get the impression that you're on a
quest for the absolutes of action function.  This is a very noble pursuit.
When you find them, please let me in on it.

Bob Hohf

> >...what we're talking about is what to do if the existing string
> >height doesn't allow optimum configuration of the action parts.  The
> >most common scenerio I've seen is string height too high.
> >
> >If you maintain the optimum line in this case several things may result:
> >
> >1.  Hammershank swings above parallel to keybed
> >2.  Hammer overcenters at strike
> >3. Hammershank so high above (nonadjustable) rest felt that the
> >action locks up on certain blows
> >4.ÊJack may jam into felt at the back of the rep window
> >5. Loss of mechanical efficiency
> >
> >Or you can raise the stack, sacrificing the line and:
> >
> >1. The wippen cushion wears out faster.
> >
> >This is the sort of real life choice that we have to make all the
> >time in action work.  What would you do?
>
> The picture you paint seems to me simply a case of an action with the
> wrong hammer-heads.  As to (1) there are many pianos with actions
> that are designed to have the shank pass the horizontal and the
> hammer heads bored to lean outwards so that they meet the string at a
> right angle.  As to (2) and (3) neither of these cases will arise if
> the hammer-heads are properly bored with regard to bore-length and
> bore-angle.  (4) means the touch is too deep.  Unless you give full
> measurements for a particular case it is difficult to follow your
> logic.  Certainly if one proceeds by trial and error with an action,
> one invites endless problems.
>
> JD
>