Baldwin SD-10

[Ron Nossaman]

>Perhaps I expressed myself badly.  I didn't mean to imply that there is
>a direct correlation between pin angle and stagger angle.  However,
>if the pin angle, or the offset of the string caused by a greater pin
>angle, is causing cracking of the bridge, then the designer who wants
>to use a greater pin angle could compensate for this tendency to crack
>the bridge by deliberately creating less stagger angle by moving the
>bridge pin holes relative to one another. 

Phil, either I'm still misunderstanding, or you just did it again! True,
increased pin angle will move the string farther from the center of the pin
at bridge cap level. That will put more leverage on the bridge cap because
the string to pin contact point is further up the pin from the pin to cap
contact. If the front and rear pins are positioned in a straight line
between hitch and agraffe, then the stagger angle will increase with a
higher pin angle. The pins usually aren't on that line though, because the
bridge driller (human or otherwise) offsets the rows of holes to whatever
produces the wanted stagger angle, with the chosen expected string
diameter, pin diameter and angle. Is any of that even close?  


> If one saw a piano with a large
>bridge pin angle that did have this compensation and there was no
>cracking it might not be correct to assume that a large pin angle has
>no effect on bridge cracking.
>   However, if things are as you say, that other factors have more
>influence, then excessive pin angle probably doesn't matter to a sound
>bridge.
>
>Phil

I'd say it was a matter of degree. 
Generalities are all I have to give here, because generalities are all I
have. Staying within reasonable limits of stagger angle and pin angle with
properly oriented cap grain seems, by the process of comparing many many
old bridges that have failed with many many old bridges that haven't, to
indicate that poor cap grain orientation is the statistically likely
primary cause of the failures.


Ron N