Regulating Without Specs

[Delwin D Fandrich]

Please, oh please, keep it metric. Even the inventors of the ridiculous Imperial
system of measure have abandoned it.
 
Del
Delwin D Fandrich
Piano Design & Manufacturing Consultant
620 South Tower Avenue
Centralia, Washington 98531  USA
Phone  360.736-7563
<mailto:fandrich at pianobuilders.com> 


  _____  

From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of
A440 Piano Service
Sent: February 04, 2008 6:00 PM
To: PTG List
Subject: Regulating Without Specs


Hello List,
 
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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