My piano, Chickering

[Delwin D Fandrich]

Michael J. Wathen wrote:
> 
> So, as I understand your reasoning (ddf's) the angle that the strings pass
> through after leaving the V bar or agraffee determines how much of the
> string energy is reflected back in to the standing wave on the speaking
> length.  

Yes, that's basically correct.


> Would you use the same argument for greater side bearing at the
> terminating bridge pin?  Why not?

Yes. There are several other factors involved here, though. The bridge
pin is typically angled with reference to the bridge surface. This helps
to clamp the string against the top surface of the bridge. There is a
second bridge pin located 15 to 25 mm behind the first that also helps.
In the case of the V-bar its best to stop all of the wave energy and
keep it in the string. At the bridge, the idea is to actually get some
amount of energy to couple through the bridge and move the soundboard
assembly.
> 
> Yes, your interpretation of the picture http://ucccm56.ccm.uc.edu/duplex.jpg
> is indeed correct.  Since the board was over a hundred I felt that I need to
> control the amount of bearing across the back side of the bridge and reduce
> it to a bare minimum.  The ability to select the correct diameter and the
> lubraciousness of the copper wrapping led me in this direction.
> 
> Originally the Chickering had felt glued to the plate just in front of the
> hitch pins.  Would you have left the felt there?  If so why?

Actually, I'd have replaced the soundboard and capped the bridges. There
is no way that a soundboard that old can have the necessary amount of
stiffness that it needs to provide the proper impedance load to the
strings. Both sustain and tone quality will have suffered. Assuming that
wasn't an option for you, I'd suggest that you still need a certain
minimum amount of string load on the soundboard. Forget about crown,
there isn't going to be much left after a hundred years, if any. But
without some sting load against the bridge (i.e., downbearing) you're
going to have a tough time realizing even what little tone performance
the old board does have left to give. 

I'm not a fan of felt strips substituting for proper bearing surfaces in
the back scale, so I'd probably have taken it out if I could. But
whatever you use for the back bearing surface, I'd try to get at least
1/4 degree of string deflection through the bass and 1/2 degree through
the tenor if at all possible.

--ddf