Drop

[A440A@aol.com]

Bradley  writes:
 
>Hummm . . . I tend to set the springs so that there is a slight feel to
>the 'recoil.' I feel that the recoil is not felt in fast repetitive sections,
> which is my primary reason for setting the springs tighter in the first
> place. 

   I agree, the recoil isn't felt in fast repetition because the hammer 
doesn't go upwards like it does when we are setting the springs and checking 
the amount of tension by the speed of the hammer's upward travel.  In fast 
repetition, the hammer remains motionless until the jack resets and the key 
begins to lift it again.  Try it and see; put the hammer into check and 
rapidly let go of the key, the hammer doesn't move upwards at all, it just 
drops as soon as the key has returned to its at rest position.   If you can, 
play the note repeatedly and rapidly and you will see the hammer moves from 
its position in check to the string and back, but only under power from the 
jack.  

>It would really only be a problem in slow softer types of passages,
> but since the faster sections are far more prevalent in the concert
> literature than the slower sections, I think that the pianist can/should
> simply compensate for the slight recoil. 

    I don't think it is a matter of compensation so much as a degree of 
effortless expression in the ppp passages. If there was a need for an 
intrusive spring tension, I would accept the compromise in sensitivity on  
softer play, but I don't think there is a need for a recoiling spring, and I 
haven't seen the need for it. (see below)
  
i said:  
>     Setting the springs higher than what it takes to lift the hammers as 
fast
> as possible without feeling the recoil will gain you virtually nothing in
> repetition speed,(unless there is something else wrong that excessive spring
> is making up for).

RicB writes: 
>Hmm...dont know if I buy this Ed. I find I can get rapid fire repetition if I
>push that as far as I can get away with. Perhaps you might be so kind as to 
give
>your complete list of ingredients in your "fastest fire" recipie. :) Maybe 
I'm
>missing something.

    I find that, assuming all pinning to be correct, repetition speed is 
dependant both on the velocity of key return and the distance it must do so 
to reset the jack.  So,  if I may address these two independantly: 
       The key must move upwards far enough to allow the jack to reset. The 
factors involved are, in order of importance, 
1. backcheck height=  the higher the height, the less distance needed for key 
travel, but also the less power     available in fast repetition, (you can't 
get much power out of a 1/4" hammer blow...)
2. aftertouch = See Roger Jolly's description of aftertouch as a "black 
hole"; it is dead space the key must    rise through before reengaging the 
jack.  distance is time
3. minimum tangent requirment between jack and knuckle for the jack to grab 
rather than skip 
    a. this is affected by leather surface, knuckle shape, and condition of 
the leading edge of the jack, as well,      to a lesser extent, by the spring 
tension on the the jack.

The key's return speed is dependant on its own list of factors,  I am not 
sure of the order of importance, but some things to consider: 
1.  Mass =  excessive leading will move slower
2.  action ratio.  excessively high ratios reduce the effort required to 
depress the key, but also can slow the  spring's effect on inertia, thus 
slowing the keys' acceleration upwards
3.  friction,(of course), friction losses in the grub translate directly to 
reduced force of the spring acting      through the whippen to raise the key. 
 Keybushing is also a factor.
4.  Spring strength 
      What I have seen is that the difference in key return velocity changes 
very, very little between a spring that will lift a hammer smoothly and a 
spring that can be felt to recoil in the key. A difference can be seen when 
comparing a spring that is extremely weak and one that is far to strong to 
use, but between a recoiling spring and one that can't quite be felt, the 
difference is indistinguishable.  I think the elements of distance listed 
above yield greater gains than the difference in spring strength.  
   The importance of the spring can be seen in a side by side comparison, ie, 
 on a well-regulated action, depress the C4 slowly, so that it is at drop but 
not in check.  Then strike the B3 so that it goes into check.  Release both 
keys at the same instant and see which one will return most rapidly.  The key 
with the spring powering it from check moves much faster.  
     Now, of course, the hammer that is at drop is much higher than the one 
at check, so it may be that the jack will reset under it faster due to the 
lesser distance.  However, I am not sure this is of much use to the pianist, 
as it would be difficult to play rapidly so softly that the hammer is not 
checking.  
   Pianist's technique varys quite a bit.  I have seen some that wanted 
repetition to occur with virtually no rise of the key, they wanted to play in 
the very bottom of the keystroke. for this, I reduce aftertouch, either by 
lengthening hammer blow or reducing keydip, and I raise the checking height 
to the max.  Others, that can drill Ravel scores from well above the keyboard 
don't need that high a check, and often prefer the additional power available 
from a little more hammer blow.  
   Everything in the action has a range, from overly dependable and 
insensitive on one extreme, to white-knuckle-edge-of-failure maximum 
performance on the other, (like jacks as far proximal as possible and let-off 
just a heartbeat away from blocking, etc).   I personally prefer to make the 
action as sensitive as possible and that means working towards as transparent 
an escapement as I can, while still maintaining speed power and 
dependability.  A strong spring, coupled with any more drop than is 
absolutely necessary, makes control on the softest passages more difficult.   
Achieving evenness will also, at times, force a compromise on some of these 
ideals. 
Regards, 
Ed Foote RPT