Bridge Pin Angles

[Phillip Ford]

>Hi Phil.
>Since we seem to need to get this most central point clear before we can 
>go further, lets get this down first :)
>
>Positive bearing at all points on the bridge says just that.  If you draw 
>a straight line from the highest point on the bridge down to the front 
>termination, then any point on the bridge that lies under this line is in 
>a state of negative bearing.  Same thing really going from the back side 
>of the bridge to the hitch pin.

So you're using the word bearing in the engineering sense, contact between 
the string and the bridge cap, not in the traditional piano sense of 
downbearing or net downforce on the bridge.  I've been equating the words 
bearing and downbearing.  I will try to make a distinction from now on.


>Negative bearing is ALSO found when the whole bridge itself is below the 
>string line... but then ... well.. there is no <<highest point on the 
>bridge>> per se as its all under the string line.

There would be negative bearing in the sense of no contact between string 
and bridge cap.  But there can be positive downbearing in this case.

>This is central to the whole line of reasoning that Rons <<theory>> rests 
>on.   If there is positive bearing at all points on the bridge, and 
>strings need seating, then Rons claims do no not hold.

I'm baffled by this.  If we're using bearing here in the sense of contact 
between string and bridge cap, and there is contact everywhere across the 
cap by the string, why would it need seating?  It's already seated.

>Most certainly string seating is indeed a far more then temporary fix in 
>this case

I would agree that it shouldn't be temporary in this case because you 
haven't changed anything.  And if this piano can somehow live the rest of 
its life without sustaining any cap indentation, then this 'fix' should be 
permanent.

>and most certainly called for.

Why?  As I said, the string is already seated.

>  It doesnt exhasperate the condition any more then is neccessary and 
> expectable given normal life spans and useage patterns for instruments... 
> I mean hey.. hammers wear with use too :)....
>
>Remember... Ron is not simply pointing out that the clamped condition of 
>the strings are partially the cause  indentation of the bridge in the face 
>of upward pressure on the strings by the bridge. This is very old news indeed.

It wasn't old news to me when we started this thread.  I guess I haven't been paying attention.

Phil F

>He has claimed that whenever the strings <<need seating>> it is because 
>this indentation has become so severe as to represent negative bearing at 
>the notch...or over the whole bridge. Or it is because the soundboard has 
>collapsed and is in a state of absolute negative bearing.  Until a couple 
>days ago, he also claimed that the dynamics of the system prevented any 
>conditon where string seating was needed in the case where said negative 
>bearing was not evident. And all this in turn has been used to tout the 
>basic futileness of string seating in all instances.
>
>We cant recommend to folks that they not seat strings based on this.
>The only time string seating is in any meaningfull sense of the phrase <<a 
>temporary fix>> is when there is indeed negative bearing at some 
>point(s)on the bridge. And clearly.. this is not always the case.
>
>Cheers
>RicB