Hallet & Davis bridge agraffes back

[Richard Moody]

James enquired, 
	"Is the effect of the downbearing
> then equalizing the upbearing?"


My guess is,  this alternating of high and low back bearing on the
agraffes is to equalize the vector forces.  I believe the speaking length
holes are on the same line, and provide an over all down bearing. The
position of the rear holes alternating high and low (above and below the
spk length side holes) is a puzzler. The rear bearing point is the same as
in all pianos, a ridge capped with felt.
	 It seems to me these holes provide a "swagger" much like bridge pins,
execpt it is in the vertical mode rather than the horizontal. The swagger
is to prevent strings buzzing inside the agraffe. I bet they found out the
hard way, agraffes with holes straight through buzzed like crazy .  Rather
than give up, Geo Davis, (my guess as to the brains behind this) some how
conceived the idea of drilling the holes slanting down. But after he
installed these while there was no buzzing, the bridge must have had a
tendency to rock forward possibly tearing itself away from the sound board
from the collective forces.  Combining Yankee ingenuity and "Scotch
determination" he pursued the only other alternative, and drilled the
other half in oposite direction and install them alternating. Indeed
looking at the marks on the bridge under the agraffes, some are indented
toward the tuning pins, some have an indentation  toward the bridge pins. 

Richard Moody  
----------
> From: pianoman <pianoman@inlink.com>
> To: Richard Moody <remoody@easnet.net>
> Subject: Re: Hallet & Davis  bridge agraffes  back
> Date: Monday, August 31, 1998 6:48 AM
> 
> Hi Richard,The Explainer.
> Thanks for the expla.  It sounds like one of those things that are easy
to
> think of but hard to do type designs.  Is the effect of the downbearing
> then equalizing the upbearing?
> James Grebe
> R.P.T. of the P.T.G.
>  St. Louis, MO.
> Competent Service since 1962
>                                         Caster Cup Center of the
Universe
>                    Home of Handsome Hardwood Caster Cups
> pianoman@inlink.com        
> 
> ----------
> > From: Richard Moody <remoody@easnet.net>
> > To: pianoman@inlink.com
> > Cc: pianotech@ptg.org
> > Subject: Hallet & Davis  bridge agraffes 
> > Date: Sunday, August 30, 1998 9:26 PM
> > 
> > 
> > Preview.   The Hallet and Davis bridge agraffes are drilled at an
angle
> so
> > that the strings appear even on a plane on the speaking side, but on
the
> > tail side they are alternatly higher and lower. Brass, machine
threaded
> > screwed into wood. The agraffes with holes higher than the speaking
side
> > have longer threaded shanks.  The bass agraffes are slotted from each
> side
> > so that the slakened string can be removed.  Which is the only way it
can
> > be done unless you want to form the hitchpin ties when the string is
> > already in the piano. ; )