drop adjustment

[A440A@AOL.COM]

Tim asks:
<< Could someone shed some light on gauging the proper amount of 
drop for grand regulation.  I'm working on a Yamaha with poor after touch.
Any help would be appreciated.>>

Greetings, 
   I set drop at the same distance from the string as I do let-off.  They are 
both dependant on the string excursion zone to set the limit on powered 
hammer travel.  
The springs need be set to lift the hammers from check as fast as possible 
without being felt in the key.  
  The aftertouch is dependant on three things:   hammer blow, let-off, and 
keydip.  It is inversely proportional to the first and proportional to the 
second and third.  Finding the optimum setting for the three requires that 
you start from somewhere, and usually for the Yamaha, 1 3/4" blow is a good 
place.  Set 1/16" let-off and 3/8" keydip and see what you have for 
aftertouch.  If you need more,  lower the keydip first to .395 or so.  After 
that, you may need to raise your hammerline,  but .020" of aftertouch is 
enough for most of these pianos.  
Regards, 
Ed Foote RPT