[pianotech] Increasing bridge height

[Ron Nossaman]

Will Truitt wrote:
> Hi Ron:  
> 
> One question that has not been asked by me or anyone else is what changes
> you are making to the height of the bridge other than in the high treble.
> We are talking here about of Note 88 having a bridge height of  30 mm (Del
> says elsewhere that 32 mm is ideal for the A-2 in question).  Are you making
> the bridge height along its entire length the same height as in the  high
> treble, or are you raising it by a corresponding amount along its length (as
> in adding 5 mm. or whatever everywhere?). 

Hi Will,
I'm adding height to the high treble by changing the thickness 
taper of the long bridge. I don't need to raise the height of 
the low tenor, do I? Making the high treble taller will make 
positioning the plate higher in the treble, which will make 
the string height through the treble more uniform which will 
make boring the hammers simpler. I don't know of a simpler way 
to state this.


> Is there sufficient benefit to be
> had by increasing  the bridge height along its length to merit doing so, or
> is the bang for the buck best realized only in the treble?

I haven't yet found a compelling need to make the entire 
bridge taller, but I haven't seen one of every kind of piano 
yet, so I'll think that one over when it shows up in the shop. 
The treble is the problem in the Steinways, as has been said. 
I make the bass bridge a few millimeters taller to accommodate 
vertical hitches, and the transition bridge taller to 
accommodate the much longer back scale, but I usually leave 
the low tenor bridge height at about where it was.


> I would be
> grateful if you would describe your method for the entire treble bridge for
> the sake of clarity.  From your other comments, it sounds to me like you are
> making it fairly uniformly one height.

More nearly one height throughout than it originally was. 
That's why I keep saying to make the treble taller rather than 
saying to make the entire bridge taller.


 >If I bore the treble hammers
> to only one value, it seems a matter of choosing my poison - I am going to
> be overcentering, undercentering, and just right depending on what note I am
> on.  If all else is equal, it seems a candidate for a tapered bore, unless
> there is some sublime mystery to Steinway's one size fits all boring that I
> am missing here.
> 
> Will  

The standard piano to the world can't be wrong can it? But 
maybe it can be made more nearly right, if not exactly.

I can't give you absolute numbers that will work on pianos of 
which no two on the planet are the same. If the TREBLE end of 
the bridge is made TALLER, the string height can be made MORE 
NEARLY the same throughout the tenor and treble than it 
typically is, which may or may not mean you can bore all the 
tenor and treble hammers the same length and accommodate the 
"close enough" near quasi uniformity of string height 
resulting from propping up the treble end of the plate to 
accommodate the increased treble height of the long bridge. At 
some point you have to decide how many decimal points to round 
to as a working value and do what you have to do to stay 
within your tolerance. This situation seems to be an 
indication that the manufacturer didn't like measurements at 
all, or what they did would have a more logical look about it. 
Making the treble end of the bridge taller will both make the 
treble stiffer, which is a good thing, and it will make the 
string heights closer to the same than they were, which also 
strikes me as a good thing, especially if the string heights 
get close enough (post decimal tolerance rounding) to the same 
to be able to bore all the long bridge hammers the same length.

Sometimes it takes a fair amount of work to make something 
simpler.
Ron N