[pianotech] Action ration measuring

[David Love]

I'm glad this was reposted on this list as I've tried to respond to the
other list via email with no success.  I use the following guidelines for
measure action ratios.  Different people use different methods, I find this
one to be the most accurate and meaningful. 

 

This is the beginning of addressing the other question which appeared on
that other list but which I was unable to respond to with some hoop jumping.
This had to do with different ratios between sharps and naturals.  The
bigger question is what is the overall ratio of the system and the second
question would be what are the hammer weights (or strike weights if you
prefer) that will give an indication of whether the match between leverage
and hammer weight was correct.  The issue of different ratios for sharps and
naturals is a non issue, in my opinion.  I agree with Nick G. that concern
about the magic line is overrated. 

 

Once the action ratio is known then with a combination of various other
criteria, the hammer weight or strike weight can be optimized always (as it
should with the action ratio) keeping in mind the implication for regulation
specs.    

 

Sorry I don't have a picture.

 

 

Ea = is the actuating segment of the lever


Ra = is the reacting segment of the lever


 

-Key Ea is measured from front of key to center of balance pin at punchings
measured along the bottom of the key.                                      

-Key Ra is measured from center of balance pin to perpendicular line which
passes through center of capstan top measured along the bottom of the key.


-Wippen Ea is measured from the wippen center pin to a line perpendicular to
the contact point of the wippen heel/capstan contact point measure along a
line between the wippen flange center pin and the jack center pin.


-Wippen Ra is measured from the wippen center pin to the jack center pin.


 

-Shank Ea is measured from the hammer flange center pin to the center of the
knuckle core measured along the shank.                                   

-Shank Ra is measured from the hammer flange center pin to the center of the
hammer molding measured along the shank.

 

Calculate the ratio of each lever according to following example RA/EA. The
action ratio will be a product of the ratio of the three levers.  In this
case .49 * 1.59* 7.47 = 5.79                              

 

	
Ea

Ra

	Ratio


Key

262

128

	0.49


Wippen

63

100

	1.59


Shank

17

127

	7.47

                              

	
Action ratio:

5.79

 

 

David Love

www.davidlovepianos.com

 

 

-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Brown, David
Sent: Wednesday, September 19, 2012 4:00 PM
To: pianotech at ptg.org
Subject: [pianotech] Action ration measuring

 

All -

 

Asked this question on the wrong list....

 

 

I have enjoyed very much the ratio discussions, especially the ongoing one
as few weeks ago ( key in , key out etc) that Nick and several others
contributed to. My question-

 

What is a practical way to actually take those measurements, especially the
key measurements? Many times I will put a long center pin in a wip flange,
tie off some carpet thread and use that to look at the lines of compliance
for key- wip- capstan, but how to measure key in- key out accurately and
predictably? Calipers? Rulers? Also, I have seen a couple of ways to measure
for key in - from balance point to the end  of the keytop, from balance
point to where the front pin enters the key. This relates some to what Fred
was posting, but thought another topic would not muddy things up.

 

Thanks for this interesting discussion

 

David

 

David C. Brown RPT

Piano Technician

Division of Music

Meadows School of the Arts

Southern Methodist University

Dallas Texas 1-214-768-3976

 <mailto:dcbrown at smu.edu> dcbrown at smu.edu
[cid:244020A4-F74B-47C9-84DB-458AE37E6657]

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