[pianotech] Increasing bridge height

[Will Truitt]

Well, JD, you certainly are a good salesman for the concept.  I was
certainly left with a positive impression of the 6' 7" Kimball Viennese
edition sustain and volume, it's many other flaws notwithstanding.  I am
thinking more and more that I will be wanting to raise the bridge height on
this Steinway A.  The bridge height at note 88 is about 25.5 mm, about 28
around note 70, 30 at note 40, and 33 just below note 21 (it's a 20 note
bass piano). Del's practice is to take 88 up to at least 30 mm.  

There are some things associated with making the change of the plate
elevation that must accompany the taller bridge that I want to have a better
sense of.  One, the higher string plane will likely necessitate the use of
new damper wire, as the old may be too short, yes?  

The other concern that I have is the need for a longer hammer bore that must
accompany the change to the string plane height. Not the boring or
calculating of the measure - I've been doing that for over 20 years - but
rather the low entrance into the action cavity that Steinways have at the
bottom of the stretcher.  As you know, there is often scant clearance for
the hammer drop screws, which leaves little room to raise the action stack
if that becomes part of the overall equation.  Of concern too is whether the
longer bored hammers will fit under the stretcher if I have added 4 or 5 mm
to the bore distance even though the bottoms of the shanks are pressing into
the hammer rest felt. I can see it now - go to all the trouble of raising
the bridge, installing the soundboard, stringing the piano, and boring the
hammers - and not being able to slide the action into the cavity.  Saturday
night, all dressed up, with nowhere to go.  

I hope others who have experience doing this on Steinways are following the
thread here and will chime in with the benefit of their experience.

Will Truitt  



-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of John Delacour
Sent: Monday, March 23, 2009 6:00 PM
To: pianotech at ptg.org
Subject: Re: [pianotech] Increasing bridge height

At 23:30 +0000 22/3/09, John Delacour wrote:

>Kirkman's tall bridges, on the grands at least, were built of spruce 
>with a thick (about 1/2") beech capping and steep notches.  Sound 
>travels faster in spruce.

I've just dusted off one of the uprights, which has a bridge fully 
45mm at the treble end.  This also has a slow-grown spruce (about 1.5 
mm per annum) root with the rings parallel to the soundboard, and the 
top is of beech about 15 mm deep.  This piano advertises itself as a 
"Vertical Iron Grand".  I remove the name-rail and the fall when 
asking people to assess it and everyone comments that it sounds and 
behaves like a grand, without knowing what it is.  I am convinced 
that its quality is due largely to the bridge, combined with a very 
good string scale (agraffes all through).

JD