Rescaling and bearing

David Love davidlovepianos@earthlink.net
Thu, 3 Jan 2002 17:33:29 -0800


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This query goes back  to Dale Erwin's comment about a Steinway O for =
which the scale had been recalculated by Sanderson with a higher tension =
and it ended up choking the board such that the piano had to be restrung =
with the original scale. =20

My question is broad and I really just want to open the topic up for =
discussion as I'm interested in researching this area  and would =
appreciate any comments or recommendations for further reading. =20

My impression about Sanderson, perhaps others, is that the priority for =
scale calculation is in the area of inharmonicity rather than overall =
tension and that this sometimes leads to the case mentioned above.  My =
basic question is, if in order to get a smooth inharmonicity curve a =
higher tension scale is called for, can one simply alter the downbearing =
so that the load on the board is roughly the same?  (All other things =
being equal and assuming the additional tension doesn't create a problem =
for the plate).  =20

Additionally, is there an optimum load that the board should have in =
each section?  The other day, Ron N. was discussing the Lowell gauge and =
how do calculate the load given various dimensions and tension.  I have =
also heard Ron and others mention that they aim for a certain number of =
degrees of downbearing in different sections of the piano.  But wouldn't =
the optimum number of degrees vary with the overall tension?  And since =
there seems to be disagreement about the criteria for choices about =
tension levels  what are the important criteria?  Since creating a =
smooth inharmonicity curve seems like a reasonable goal (that the piano =
should tune well), how can one approach rescaling a piano (where it's =
called for) and maintain an optimum load on the board?    Do all of you =
who get involved in soundboard and bridge design actually calculate the =
load on the board in terms of pounds in each section or overall?  If so, =
what do you aim for?  Or do you just kind of wing it using basic rules =
of thumb (quarter, nickel, dime etc...)?

David Love



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