Chaging upright bridge location & affects

[Delwin D Fandrich]

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  ----- Original Message -----=20
  From: Erwinspiano@aol.com=20
  To: pianotech@ptg.org=20
  Sent: November 22, 2003 6:50 PM
  Subject: Chaging upright bridge location & affects


       Since I need to do extensive repairs anyway I'm considering =
building a solid bridge & attaching it to the board where the apron is =
currently joined. The current string lengths on note 1 is a very long =
51& 1/2 "& note 28 is 41 & 1/2". If I relocate the bridge It will be =
shortening those strings by 2&1/2" on note 1. & 3 & 1/2" on note 28. The =
new length will be  49'& 38 & 1/2" respectively. Still long strings.  =
Because of the half moon shape the longer strings will become even =
sorter especially if I use a straight bridge which, would be simpler. =
The middle& longer strings would be shorten by as much as 5."
     I'm looking for feedback from others who have done this or have an =
idea about it. A prime consideration for me is, will this improve or =
inhibit damping? How will it improve the sound? From what others have =
said just attaching it to directly to the board will improve mechanical =
efficiency. No argument there,
      In most uprights the dampers best location would be where the =
hammers hit the strings but obviously they can't be there. Also I don't =
want to end up with the damper on some nodal point that creates some =
harmonic that I can't resolve. In fact perhaps this is why the strings =
on most uprights are so long perhaps to mitigate that effect. I don't =
know. Will shortening the string push the optimal damping point even =
further up the string towards the tuning pins? That to me would be bad.
Actually, this is rarely (if ever) a factor effecting the damping =
efficiency of vertical pianos. This notion has been repeated so often we =
have generally come to believe it even though it has no basis in fact. =
It becomes rather like the fundamental political maxim: even the most =
blatant lie when repeated often enough will come to be accepted by the =
majority as truth.

At the risk of sounding like a broken record this subject has also =
appeared in one of my Journal articles. Several years back I naively =
thought presenting a good working introduction to the basic theoretical =
function of the piano damper in a Journal I thought was at least widely =
read, if not studied, would do some to dispel this obsolete and =
erroneous notion. I was wrong.

But to get to the crux of your question: The first issue to consider is =
what you are doing to the hammer strike point -- particularly across the =
bass/tenor break. Do you have any idea? The second is to consider what =
you are doing to the impedance relationship between the bridge and the =
soundboard system. How are you planning to alter the design of the rib =
structure to accommodate this change? Finally, knowing the speaking =
lengths of the first and last notes on the bridge provides us with just =
enough information to be dangerous. This information by itself doesn't =
tell us anything at all that will help answer your question. How does =
this information relate to the overall scale? How will the proposed =
changes relate to the overall scale? Are you prepared to knowledgably =
make the scaling adjustments needed to blend this new bass scale in with =
the rest of the piano?

Obviously, I am in favor of modifying existing pianos to improve their =
performance. But to achieve good (and predictable) results each change =
must be integrated with the overall design of the piano. A lot more =
consideration must go into making alterations like this than simply =
pondering what might happen to damping efficiency (though evidence =
suggests that some manufacturers don't even get this far before making =
even more extensive changes). Providing the background to help answer =
this question is the whole point behind the all day seminars I give on =
the subject. And even with six hours I barely have time to scratch the =
surface.=20

Del
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