pinning bridges

[Susan Kline]

Hi, Ron

Without any direct experience, I can still think of an alternative, similar
to what woodworkers do when tenons are going to collide: shorten a few of
the pins, preferably the rear ones, I would think. It wouldn't take much,
would it? 

Heresy? Well, since I haven't learned the orthodox answers, just call it
ignorance instead ...

Susan
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At 10:56 AM 9/20/98 -0500, you wrote:
>Hi gang, a few more harmless observations and speculations for your general
>entertainment, enlightenment, discussion, annoyance, or trash can.
>
>For some time now I have been looking at how different manufacturers notch
>bridges and install bridge pins. (Yea, I know, but I need *something*
>interesting to do while I'm tuning) Making new bass bridges for verticals is
>simple and nearly goof proof. Recapping treble bridges in grands is
>considerably more involved, but *most* folks work from a pattern made from
>the old bridge and try to reproduce what was there originally. How about if
>you are designing a scale and making a treble bridge from scratch? 
>
>At a certain point in the treble scale, somewhere around the beginning of
>octave 5, give or take depending on the length of the scale (the longer the
>piano, the higher in the scale this should occur, yes?), the back bridge
>pins of a given note, say C5 (52), will intersect the front pins of B5 (51)
>somewhere below the bridge surface unless something is repositioned. There
>seems to be four ways around this.
>
>1. Scaling: This involves foreshortening the speaking lengths of the scale
>(coming down from the treble) just enough to maintain pin clearance through
>the 'crossover point', and jumping back to the natural (I assume) length
>progression at the change in wire size. The 'benefit' here seems to be that
>the distance between the front and back rows of bridge pins can remain
>constant through the scale, possibly to simplify automated drilling
>procedures. Yamaha does this in some models. Oddly enough, this is probably
>the least noticeable (visually) of the various compromises. BTW, to minimize
>typing trauma, and since Merle didn't supply me with an official name for
>it, I will call this distance the 'black'. 
>
>2. Floating the 'black': Leaving the scale progression alone, the black can
>be progressively lengthened from about three unisons up scale, down to the
>'crossover' point, shortened enough for clearance at that point, and blended
>back into the 'standard' length a couple of unisons down scale. This is a
>very common way of dealing with, not only bridge pin interference, but
>fitting the scale on the bridge at scale breaks where the bridge dog leg
>isn't severe enough to center the 'black'. Some pretty severe examples of
>this can be seen in some models of Baldwin and Steinway, but it is a widely
>practiced and very common technique. Quite noticeable, especially if the
>back row of pins isn't offset correctly and the stagger angle increases
>severely as the 'black' narrows. 
>
>3. Aiming the pins: When the builder feels the pin placement is where it has
>to be, and no further relocation compromise is desirable, or possible, All
>that is left to do is modify the fore and aft (not the side) drilling angle
>to make clearance where none exists. This is a very common technique, and
>when found in tandem with #2, results in that charming snaggle toothed
>bridge look we all know and love so well. noticeable to the point of
>screaming at you from across the room if over done.
>
>4. Getting lucky: If the crossover point coincides with a plate strut,
>option #1 could be used with no visible indication that any compromise was
>made. I don't know how much leeway a designer has on placement of plate
>struts, or if they even normally consider such things. Invisible, but I'd
>like to see the tension and inharmonicity curves.
>
>
>That's it, mostly. Sorry if it reads like a lecture, it wasn't intended to,
>but I didn't see any graceful way to get it into a discussion type format
>so... Any comments, observations, dissention, flushing sounds?
>
>PS: Has anyone got a Yamaha (or any other) scale (speaking lengths as well
>as wire sizes) exhibiting method #1. I'd like to lay it into a scaling
>program and see how everything fits. 
>
>Back to work,
> Ron 
>
>
>

Susan Kline
P.O. Box 1651
Philomath, OR 97370
skline@proaxis.com