Changing upright bridge location & affects

[Farrell]

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Hi Dale,

Del rescaled a M&H 54" upright for me and we went from the cantilevered =
bass to a solid, directly-attached, bass bridge. However, the speaking =
lengths on note #1 only changed from 46.5" to 46.3" and from 38.7" to =
38.4" at note #26 (highest bass note).

So I guess this might confirm your though that you new speaking lengths =
will not be unusually short.

Sorry, this doesn't help you with your damping questions though. =
Interesting concern though - would sure like to hear what others may =
have found in cases such as this.

Regarding bass bridge shape and ultimate position - is it not best to =
let that be determined by rescaling data? And it might be interesting to =
see how the scaling would work out if a transition tenor bridge was =
considered.

Has anyone ever offered a class in string rescaling at the conventions?

Terry Farrell
  ----- Original Message -----=20
  From: Erwinspiano@aol.com=20
  To: pianotech@ptg.org=20
  Sent: Saturday, November 22, 2003 9:50 PM
  Subject: Chaging upright bridge location & affects


     List
      I wanted to pick your brains so here it is.=20
      Last week I took in a large 54' 1903 Schaff Bros. upright for =
restoration. It has a beautiful Victorian style case an intact & =
legitimate soundboard. Among the usual things it will also get a =
complete set of bridge caps. The bass bridge has the half moon shaped =
bridge mounted on the usual apron & the bridge body itself has a =
vertical crack thru to the apron that was repaired by installing several =
screws.=20
      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.
    Interestingly and for sake of comparison a Mason A Bass note 1 & 26 =
is approx. 49" & 36" Which is close to where a modified length will be =
on the upright. Also the tenor string lengths are fairly comparable in =
both pianos.
      Any insights will be of course be appreciated & as always =
stimulating & helpful.
     Thanks in advance--Dale Erwin
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