Negative bearing

[Delwin D Fandrich]

----- Original Message -----
From: "David Love" <davidlovepianos@earthlink.net>
To: <pianotech@ptg.org>
Sent: December 01, 2001 2:57 PM
Subject: Re: Negative bearing


> Ron:
>
> I've heard some (David Hughes, for example) say that he aims for zero
> bearing on the bass bridge and very minimal at bottom of the tenor bridge
> and this seems to generate the best tone at that end.  Any comments?

This depends greatly on the length of the backscale. With the typical 35 to
50 mm backscale found on some pianos this is a very good rule to follow.
However, once you get the backscale length up to some reasonable amount you
can start loading the bridge much like it is any where else in the scale.
Well, perhaps not quite as much, but certainly more than zero. We just sent
a Chickering 8' 8" (approx. 265 cm) (I think) grand out with about 1º of
string bearing across A-1. Excellent sustain and power. But, after moving
the bridge up some, it had a really long backscale.


> Does
> the bearing on the back of bass bridge give you any concerns re
compromising
> the glue joint on the cantilever?  At what point (number of degrees) would
> you be concerned?

What cantilever? I haven't remanufactured a piano of any kind or size with a
cantilever in years. There is no need for them unless you're hung up on
achieving the maximum string speaking length possible in a given size. But
in that case you are introducing several other problems as well.

But, yes. If a cantilever is there you should be careful about preloading it
with string bearing. Dig up your Journal with my article discussing
cantilevers and look at the drawing showing the stresses on the bridge and
soundboard to see what happens with them. It/s not the glue joints you need
to worry about, it's the rolling you introduce in the soundboard.

Del