Baldwin Bridges

[Delwin D Fandrich]

----- Original Message -----
From: "Ron Nossaman" <RNossaman@KSCABLE.com>
To: <pianotech@ptg.org>
Sent: August 14, 2001 8:26 AM
Subject: Baldwin Bridges


> Hi Gang,
> Tuning a newer 45" Baldwin studio yesterday, I dug out my flashlight and
> was checking out the notching on the tenor bridge when the bridge cap
> shouted at me saying "Hey dummy! Over here!" These are interesting
bridges,
> if you haven't looked at one closely. The root is about 15mm thick, with
> the grain roughly paralleling the length. The cap, however, is also about
> 15mm thick, with the grain roughly perpendicular (a bit to the right) to
> the notch. It's hard to tell with the strings on and the action in.
>
> So it's a compression crowned bridge, right?
>
> Why?
>
> They've apparently been done this way for some time, so I'm wondering.
When
> did this practice start, who started it, and for what reason?

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Ron,

Your use of the word "about" is more appropriate than you might realize.
Indeed, these are "compression crowned' bridges and they were the bane of my
existence while I was with the company. (Well, at least one of them.) The
idea was to pre-crown the bridges to match the crown of the soundboard--if
there was any. And, there usually was, though you couldn't count on it.

Unfortunately the folks making the bridge blanks couldn't seem to get the
thickness of the two parts consistent and, of course, once the two pieces
were glued together and the panel was "crowned" it was impossible to
thickness plane it to height. The excuse was that they were made of wood and
everybody knew that wood was inconsistent and it changed with the weather.
The same explanation continued to be used even after our tests proved that
from oven dry to moisture saturation the height of the bridges changed by a
few thousands of an inch, not the +/- 2.5 mm (approx. +/- 0.10") we were
seeing on various batches of bridges. I suspected, but could never prove, it
had more to do with not setting the knives of the planers consistently after
they were sharpened or replaced and then using the machine gage to adjust
for panel thickness rather than run test samples, measure and adjust as
needed.

Of course, the bridge drilling and notching fixtures were all indexed from
the bottom so you can imagine what all of this did to the accuracy of those
operations.

Carrying this on a bit further down the line you'll realize that string
bearing would also affected by the height of the bridge. Unfortunately the
supervisors and/or managers most often assumed that the plates were off--it
was easier to blame an outside vendor than one that was in-house--and order
a plate change. Without bothering to inform engineering, of course. Plate
changes take time to work their way through the system (at least intentional
ones do--unintentional plate changes seem to make it through pretty fast)
and by the time the changed plates would show up on the line the bridges
would be taller or shorter or whatever and wouldn't fit the elevations of
the new plates and the cycle would start over again. An interesting way to
build pianos, all told.

It was actually a rather good idea. Just one that was very poorly executed.
I trust the process has improved some since the late 80s.

Del