agraffes on bridge?

[Ron Nossaman]

At 04:55 PM 9/23/99 EDT, you wrote:
>
>In a message dated 9/22/1999 11:27:37 PM, musicmasters@worldnet.att.net 
>writes:
>
><<  However, if the bridge agraffs have
>upbearing, how does this comport with the treble section, which has
>traditional bridge pinning?    Isn't it really strange to combine upbearing 
>and downbearing
>on a bridge? >>
>
><<"Doesn't the upper "traditional" treble have downbearing?">>
>
>Brian H.;
> Del or Ron N. would be more qualified to answer this question than I 
>but......
>Yes in most cases of agraffed Sohmers the upper treble has 'normal' 
>downbearing, probably supported to some extent by the 'upbearing' on the rest 
>of the scale as well as crown built into the treble section of the board ?? 
>The bass section of these thingees also has "normal" bridges.
>
><<"Isn't it really strange to combine upbearing and downbearing on a 
>bridge?">>
> Well Brian it is at least 'unusual' :-)  But the H&D being discussed in 
>another thread has up and down bearing agraffes alternating throughout the 
>scale which is, to say the least, not "standard" :-)
>Jim Bryant (FL)
>


Hmmm... Guess I'd better start with the disclaimer. I don't really know. 
Now I can safely speculate a little. I think the up bearing on the agraffes
is the equivalent of side bearing offset in a conventional bridge. It's to
solidly couple the string to the bridge. What's the net bearing from the
front speaking length termination to the rear speaking length (bridge)
termination, to the rear backscale (aliquot - hitch) termination? That's
your real bearing reading for soundboard load. If this net bearing is
positive, then you have a more or less conventional loading with an unusual
bridge coupling. If it's not positive, then you have either a failed
traditional loading, or something intentionally unorthodox. Since loading a
crowned soundboard increases it's stiffness, raising it's impedance, and if
the board was intentionally built with no crown in the tenor, the bridge
agraffes might have been an attempt to have that low impedance and still get
good string coupling at the bridge. I really don't know, but someone went to
a lot of trouble to try to prove their ideas. 

Isn't the Sohmer the one with a slab of maple, backing the long bridge, on
the underside of the soundboard, with the ribs notched to fit over it? That
has to be a stiffener. Possibly a mass load too, but primarily a stiffener. 

Not much help, maybe Del's got gooder information.

 Ron N