[pianotech] Increasing bridge height

[Will Truitt]

Hi Ron:

I'm at home and not at the shop, so I'm trying to do this from memory.  I
believe #21 is 193 mm. If you want the rest of the measures at the section
ends, I'll get that tomorrow.

"I'm still trying to figure out where you plan to set the plate and bridge
heights, and why. Are you planning on boring hammers to accommodate what's
there without changing bridge or plate heights?"

Changing bridge heights is why I started this thread, and the whole point
was to explore the ramifications of increasing the bridge height in targeted
areas. I'm putting a new board in this piano, and wanted to explore this for
the many reasons already discussed.  I have not fixed yet where it will end
up, but it looks like I will raise the high treble end from 25 mm to 32 or
33 mm.  At note 21 the present bridge height is 33 mm. and I will likely
make the bridge along its length fairly consistent in height.  I will not be
using vertical hitch pins, however, so the finished bridge heights will have
to accommodate targeted downbearing values as well as the curvature of the
plate. I still have not yet pulled the plate as I have just begun teardown,
so I have a lot more groundwork to lay before I know where my feet are. 

It's premature for me to try to get into the whys and how much, as I am
still learning as much as I can before proceeding (and I have learned a
great deal from all of you so far, THANK YOU VERY MUCH!)

Whatever values I end up with on the finished bridge, I will still likely
end up tapering the bore, The bore will be derived from the measured string
heights of the strung piano after all modifications.  The taper could at
least be partially mitigated if I end up tilting the plate down in the bass
and up in the treble to help level the string plane out (as Jude has
suggested). I will likely be changing both plate and bridge heights, so
obviously the original string heights serve only as a starting point and
frame of reference. 

I don't know if it matters if the bore is a tad shorter or longer.  What
qualifies as a "tad"?  Does 6.5 mm. difference within the treble string
plane qualify as a tad?

"Play better".  I can't speak for Bruce Clark, and it would not be fair to
attribute this to him verbatim as what I quoted is my second hand recounting
in my class notes.  I think it would be best to leave the explanation of
that to him at another time.  

Will 


-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Ron Nossaman
Sent: Wednesday, March 25, 2009 7:16 PM
To: pianotech at ptg.org
Subject: Re: [pianotech] Increasing bridge height

Will Truitt wrote:
> 1.       The current bass string heights are 198 mm. on note 1 and 
> 200mm. on note 20.
>
> 4.       With this piano, I will definitely taper the bore within each 
> section, as the high point on the treble plane is 195 mm. at note 51 and 
> the low point is 188.5 mm. at note 88.  That being 6.5 mm. difference, 
> it seems to me that the over and undercentering  issues trump the hammer 
> leverage one you raised in terms of what we would actually feel and be 
> able to regulate with the least compromise.

Ok, we now have the #1, and #20 heights, the #88 height, the 
bridge height at #88 and #21, and the unspecified highest 
point  of the plain wire strings. What's the string height of 
#21? Or did I miss that?


>  It seems to me that if I 
> had to choose a poison, proper bore distance, albeit a longer one, would 
> be the best choice to make.    

Whatever you decide. I'm still trying to figure out where you 
plan to set the plate and bridge heights, and why. Are you 
planning on boring hammers to accommodate what's there without 
changing bridge or plate heights?


>By the way, I found some notes that I 
> took in Bruce Clark's WNG class last year in Nashua.  This is what I 
> wrote, and I hope I have understood Bruce correctly in his comment, 
> "Pianos play better with a shorter hammer bore, all else being equal, 
> because the center of mass is better located with a short bore than a 
> longer one."  The operative phrase here is "all else being equal".  OK, 
> Ron, now you can chime in your charming and curmudgeonly fashion Jand 
> say, "Since when is ANYTHING equal in a Steinway!"

I'm wondering how it matters if the bore is a tad shorter or 
longer if the hammer hits the string squarely and is 
reasonably well aligned with it's vertical travel. What does 
"play better" mean?
Ron N