string seating - was bridge caps

[Richard Brekne]

Ron Nossaman wrote:

That he didnt think strings could ever leave the edges of the bridge unless the
bridge at this area was indented to a degree that made any form for seating of
bridge pins a waste of time because said indentation would be below the gradient
of the string bearing angle....(and a fine explanation of why he thinks so.)
...grin.. I think that was the jist of it...

> >I have no doubt that the bridge is moving, what I questioned was whether
> >this was the reason (or how much of the reason) for the string indentations. As
> I
> >said, with positive down bearing it would seem to me the same indentations
> would come
> >about anyways.

I made this point and today decided to pull out the old calculator and at least
contribute with this one factor...Given a 1 degree string downbearing... equal
bearing front and back of the bridge and a say... half inch distance from the
middle of the bridge to the edge one should expect that the string would indent
the bridge such that at that edge the indentation should be sin 1 * 0.5.... I
would think. That would give a result of about =.0087 inch... a little under 2
hundreths of a millimeter.

Thats not much of an indentation... would be nice to measure some of these and
compare to real downbearing gradients to see if the indentations deeper then this
rekoning would account for. In the case that indentations are deeper... then I
would aggree that any seating measures taken would be temporary at best.

On the side of this I had to change a string on an older grand today... 90 years
old or so.. and noticed that the indentation the string made on the bridge was
such that at the very middle point of the bridge you could hardly see it, but very
gradually and evenly it got deeper in both directions. This is that "rounding"
over the bridge condition I maintain has to be a partial factor in bridge
indentations.

--
Richard Brekne
RPT, N.P.T.F.
Bergen, Norway
mailto:rbrekne@broadpark.no