[CAUT] Bridge design/Pure sound wire

[Jim Busby]

Hi Ron,

First of all, the piano I'm trying it on is my own Vose and Sons
($500.00) so I can experiment, somewhat. Juan Mas Cabre is sketching a
new bridge design, and with Vince's help I'll make an entirely new
bridge. The grain, etc. will be somewhat like a Steinway, but with the
type of bridge cap you taught in your class.

Here are some of the suggestions Juan gave me:

Concerning the "Pure Sound Bridge" on the Vose&Sons:
1. The treble part needs to be shifted towards the capo bar by a number
of millimeters( I can calculate). It could also be made a little
narrower, to lower bridge mass a bit.
2. The cross-over section with the treble frame bar needs to be shaped
much like on a Steinway-M bridge: small S-shape, taperad down at the
bottom to reduce stiffening the sound board and at the same time smooth
out the S - bend. The "S" shape will dileberately be shaped smaller than
needed for speaking length correction, using the top surface to do the
rest of the sp.length compensation by arranging the pins more forward or
backward, making speaking lengths in a nice and regular row this way.
3. The lowest two or three notes of the unwound section would benefit
largely from a bit more speaking length. Leaving the contact area the
same as in the original, the top 2/3 of the hight of the wood could be
shaped outwards by about an inch. Hopefully the plate edge is not in the
way. In any case this bottom part of the long bridge must get little
"feet" to stand on, stepping over the rib(s) so as not to stiffen this
critical area unnecessarily.
 We need drawings, of course, but maybe this gives you an idea in which
direction I am thinking.
Maybe brass bridge pins for the front row, facing the speaking length,
are an option, or maybe just on the three top treble octaves, for more
tuning stability. The polished stainless steel wire slides perfectly
against brass. If there is very little room for slightly thicker pins,
an epoxy treatment of the top of the bridge can work wonders! These
brass pins do not need to be much thicker than steel ones, since the
string tensions in this area are relatively low.


This is where I'm starting. I've made bass bridges (eliminating
cantelevers) but never the long bridge. If it is simply a matter of
making the same design as is already on the Vose and Sons I can do that,
but I'm betting there is much improvement to be done.

See what you've started?? Now I've got the bug to stretch much more than
I've ever done! Thanks, BTW.

Jim