Steingraeber factory pictures, bridge agraffes & adjustable vertical hitchpins

[Ric Brekne]

Hi Colin

Correct me if I am wrong in understanding your observation below. You 
point out that the string vibrating vertically doesnt consist of a 
<<dump>> of string energy, but rather simply directs more of the whole 
of the strings energy towards driving the board.  The boards impedance 
characteristics are unchanged (all other things being equal).  Ok, one 
can view the partial horizontal vibrational direction as an impedance to 
the strings overall vibrational energy...  tho I am not sure this is the 
case. Strikes me as just as likely (if not more)  that if the string 
vibrates longer in a vertical direction then more of the overall string 
energy will simply drive the board up and down.  It also strikes me 
that  a good deal of the sideways energy in horizontal vibration could 
just get lost as waist rather then shall we say <<stored >> and allowed 
to dissapate slowly (read longer sustain)

Cheers
RicB

 > Someone mentioned something about a presumed vertical vibrational mode
 > enhancement being automatically something that would simply pump more
 > string energy directly into the soundboard and actually decreasing
 > sustain.  I would say that was rather premature stated.... tho I 
would be
 > delighted to see any science that backs that idea up.

Bizarre.  This seems so obvious to me :  the board is driven by the string
(via the bridge).  If the string vibrates in a mode that is normal
(perpendicular) to the board, then all of its energy contributes to make 
the
board vibrate in a way that will in the end favor the acoustic pressure 
wave
that we hear.  If the string (partly)  vibrates in a plane that is parallel
to the board surface, that energy will result in bridge twisting and board
compressions that will transfer only a tiny bit of energy into acoustic
pressure wave that we can hear.  Now, in the case that the string vibrates
in the vertical plane, thus, I think, transferring it's energy efficiently
to the board, this doesn't always mean (or am I wrong) that the sustain
would dininish, like in the case that the impedance of the board is too
close to the impedance of the string.  In this case, impedances 
respectively
are the same, it is just the vector of the forces acting that is more close
to the shape that maximizes the transfer of energy (vertical in this case).

Best regards.

Stéphane Collin