[CAUT] stack fit to keyframe

[John Delacour]

At 6:13 am -0500 13/9/06, Bob Hohf wrote:

>...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