Regulating Without Specs

[Erwinspiano at aol.com]

Hi Jon  Dorr
    I just wanted to commend your outside the  box thinking on the topic of 
key travel/Dip.  It obviously stimulated a lot  of discussion & proved once 
again that great minds can think a like or  .....Not!.
   but each has a different way of doing one thing  common to us all that we 
are comfortable with.  Your way will give insight  to many. 
   There are other ways to measure the complete  action movement which i will 
report on later.  Bob D. got me thinking about  his comment about changing 
action ratio thru the course of entire  movement.(which is true) & so I wanted 
to check out some other  things.
  For what tis' worth.....The action ratio gauge isn't  designed to give as 
accurate an overall ratio as say a complete Stanwood  analysis but it will be 
close enough to get some very good info. for a starting  point
  Dale
 
  Dale

I'm writing an article about regulating pianos  when you don't have 
specifications.  I'll paste in the simple nuts and  bolts of it below.  I'd appreciate 
your feedback.  I know there are  some setup caveats and pitfalls, and some 
other considerations, but rather  than lay all of them out, I thought I'd wait 
and hear from you guys about what  you see as strong points, weak points, yeah 
buts, and any other  considerations.
 
Anyway, here's a simple rough draft:
 
 
No Regulation Specs?  Regulate by action ratio analysis! 
What if you had no regulation  specs, or the specs you had were not working 
out.  Wouldn’t it be great if there was a  way that you could come up with 
workable specs in minutes?  Specs that you could custom design  depending on your 
performance priorities? 
I got to thinking that if you  knew what the action ratio was on a piano, you 
could just do the math and come  up with a workable set of specs to regulate 
it with.  By making algebraic equations of the  variables, you could even 
customize a regulation based on what your priorities  were, be it key dip or blow 
distance. 
Here’s how it works:  First you determine what the action  ratio is by 
measuring how much the hammer moves compared to how much the key  moves.  
(Mechanical Action Ratio,  or MAR) You’ll need to move the key LESS than letoff and 
eliminate lost motion  first, so you can directly measure the hammer movement that 
results from key  movement.  Now say you move the  key down ¼” and the hammer 
moves 1 ¼”.   You divide the hammer movement by the key movement and discover 
an  action ratio of 5:1.  With this  number, you can now determine regulation 
specs for blow distance, key dip,  letoff and aftertouch. 
Let’s just say you want  something typical like a 3/8” key dip, 1/8” letoff, 
and .050” aftertouch.  (Later I’ll show the equations for  solving for 
different variables)    Given the 3/8” key dip (.375”) and the .050” aftertouch, 
we subtract  aftertouch from key dip and know then that we have .325” of 
useable key dip to  move the hammer.  How far will it  move?  It will move 5xs the 
amount  of keydip.  5 x .325” =  1.625”.  But that’s not the hammer  blow 
distance, because we haven’t accounted for letoff.  If we want 1/8” (.125”) 
letoff, we  need to ADD that to the hammer travel of 1.625”, so the blow distance 
is then  1.75”, or 1 ¾”. 
OK, let’s make that work out  algebraicly.  
Key travel  = Kt 
Hammer travel = Ht 
Action Ratio = Ar 
Blow Distance = Bd 
Key Dip = Kd 
Aftertouch = At 
Letoff = Lo 
Equation 1:  Determine Action Ratio 
Ht/Kt = Ar 
Equation 2: Determine Blow  Distance  (you pick key dip,  aftertouch and 
letoff specs, as in the above example) 
Bd = [(Kd – At) x Ar] + Lo 
Equation 3:  Determine Key Dip  (you pick blow distance, aftertouch,  and 
letoff) 
Step one: determine Hammer Travel    
Bd –  Lo = Ht 
Step two: determine Key Travel for that hammer travel 
Ht/Ar  = Kt 
Step three: add desired aftertouch to Key Travel to get Key Dip. 
Kt + At = Kd 
OK, Lemme know whatcha  think! 
John Dorr, RPT  (<---  brand NEW RPT, but I love writing this!) 
Helena, MT 








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