[pianotech] Measuring Action Ratios

[David Love]

No, it doesn't make sense to me either but nothing is pivoting that I can
tell.  The balance rail pin, hole, punching, shoe are all conventional.
Everything is screwed down, the regulation is correct.  However, the action
conforms much more to a 5.87 than it does to a 5.2 and so I'm making
decision about weight based on 5.87.  So far, my tests confirm that number
is correct.  

In actual practice I never rely on the key travel/hammer travel method for
actually making a decision about, say, a strike weight curve.  It's a nice
indicator but it's very easy to make a measurement error that can lead you
astray.  One-half mm error on the key dip, which can happen easily just
because of unlevel keys, can make a difference of .5 in the action ratio
(say from 5.2 to 5.7).  That's quite a bit.  So I prefer to confirm by more
conventional means where measurement error is less of a factor.  While I've
never seen the two numbers quite so far apart I do find measuring the three
levers more reliable and so I continue to use it.  This was more of an
observation that I can't really explain.  It's not really impacting my
decision making process.   

David Love
www.davidlovepianos.com


-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Jim Ialeggio
Sent: Wednesday, January 16, 2013 5:50 PM
To: pianotech at ptg.org
Subject: [pianotech] Measuring Action Ratios



David Love wrote:

<In this case the key travel/hammer travel relationship is not consistent
with the actual action ratio no matter how you measure it. 
That is the crux of the matter.

  Doesn't make sense... How about looking at the profile of the balance
rail, and/or the profile of the shoe or however the balance hole is
arranged. The theoretical pivot at the balance rail, can be different, unto
quite different from the actual way the key pivots at the balance point,
depending on how the rail/shoe is profiled. If the geometrical numbers don't
line up, some pivot somewhere, must be actually pivoting in an unexpected
way.

Jim Ialeggio

-- 
Jim Ialeggio	
jim at grandpianosolutions.com
978 425-9026
Shirley Center, MA