Baldwin SD-10

[Phillip L Ford]

Ron,
The bridge pin angle seems to be about 25 degrees.  I take it from your
response that you've seen other pianos with angles this much or more
that don't have cracking problems.  This is also tied in with where the
bridge pins are located relative to each other.  If the back holes are
directly behind the front holes with a 25 degree pin angle then you'll have
more load on the pins than if the holes are slightly offset from one
another with the 25 degree angle.  On this piano the back bridge pin
holes appear to be directly behind (in line) with the front bridge pin
holes.

Phil

---
Phillip Ford
Piano Service & Restoration
1777 Yosemite Ave
San Francisco, CA  94124

On Wed, 05 Sep 2001 20:47:53  
 Ron Nossaman wrote:
>Hi Phil, - if I may.
>
>>     I am currently rebuilding a 1982 SD-10.  I have never rebuilt one before
>>and have tuned or serviced only a few.  This one has fairly bad bridge
>>cracks in the top section of the long bridge and in the unichord section
>>of the bass bridge.  One of the other pianos that I've serviced also had
>>this problem although not as severe.  Is this typical of these pianos?
>>Although the bridge is vertically laminated with no cap I'm planning to
>>put on a cap to deal with the cracking problem?  Does anyone have any
>>comments about putting a cap on a bridge like this?
>
>Capping is certainly an option, though I would expect that it could just as
>dependably be repaired with epoxy or even Titebond.
>
>
>>     A few other observations:
>>  The angle of the bridge pins coming out of the bridges seems quite severe
>>to me and is I assume part of the reason for the bridge cracking.
>
>I would far more likely presume that the laminations weren't glued
>adequately at birth. It's awfully hard to make a case for bridges splitting
>from excessive pin angles when there are so very many with similar angles
>that are doing just fine. If you have a protractor of some sort to measure,
>knowing the angle would help with the diagnosis. Anything up to about 25°
>(guestimate) shouldn't be a problem. I'd expect something more like 20° in
>this case. Measure and let us know?
>
>
>>  The soundboard does not come all the way to the outer rim.  There is a
>>groove or channel between the soundboard and the outer rim that goes
>>down to the inner rim.  It appears to have been cut after the soundboard
>>was installed.  Does anyone know the reason for this?
>
>That's not a feature, that's a condition, or result. The soundboard just
>wasn't trimmed in the dried down state, to exactly fit the inside edge of
>the outer rim. There's a gap, with some glue squeeze-out between the
>soundboard perimeter and the outer rim, making it look like a planned
>groove. T'ain't, and it's neither here, nor there. It won't affect the
>function of the soundboard one way or another in any measurable way, no
>matter who points it out as either a feature or a flaw. If the board's
>glued to the inner rim, it's adequately terminated and anchored at the
>perimeter. Disregard.  
>
>
>>  Looking down into the groove one can see the ends of the relief cuts
>>where the ribs are let in to the inner rim.  The ends of these cuts are
>>rounded as if they were cut with a router or mill.  The ends of the ribs
>>are squared and do not come all the way to the end of the relief cuts.
>>I had always assumed that good quality pianos were built with the ribs
>>closely fitted to their relief pockets and soundboards always ending at
>>the outer rim, but apparently this is not always the case.
>>
>>Phil
>
>This is another of the wonderfully anal presumptions of entrenched
>soundboard dogma. Mechanically, and acoustically, if everything is glued
>down solidly at the inner perimeter of the inner rim, it matters not what
>sloppiness of fit prevails beyond. Functionally, if the panel is securely
>adhered to the inner rim, the .difference between a rib that is PERFECTLY
>fitted to it's inner rim mortice on all four surfaces will be acoustically
>indistinguishable from one that isn't within 2 millimeters of any of it's
>mortice sides. The rib is glued to the panel, which is glued to the rim, so
>from an acoustic standpoint, the rib is quite solidly mounted whether it
>touches all or even any of the sides or bottom of it's rim mortice. If the
>final performance of the soundboard hinges (sorry) on the fit of the ribs
>in their rim mortices, the design is doomed even before the first drop of
>glue is spread.
>
>But that's just my opinion and experience.
>
>
>Ron N
>


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