Walter Coupling Strap

[Delwin D Fandrich]

> -----Original Message-----
> From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org]On
> Behalf Of Phillip Ford
> Sent: April 06, 2004 9:18 AM
> To: pianotech@ptg.org
> Subject: RE: Walter Coupling Strap
>
>
> >
> >It is simply a steel strap (approx. 1" w x 5/8" thick) that extends from
the
> >bottom of the plate at the bass/tenor "X" over to the top of the
bellyrail.
> >Mostly it prevents the plate from drifting down as tension is applied to
the
> >strings but it does couple some moderate amount of string load to the top
of
> >the bellyrail directly in line with a bellybrace. Not as much as the
> >Steinway horn/wedge arrangement, but some. Most of the string load is
still
> >born by the plate.
> >
> >Del
>
> If I'm picturing this correctly, it sounds like something I've seen
> on some older Knabes.  A piece of bar stock angled at about 45
> degrees down from the underside of the plate at the crossover.  It
> was a removable piece fitted into a notch on the underside of the
> plate and butted against a plate on the bellyrail.  The point on the
> plate was forward of (to the keyboard side of) the point on the
> bellyrail, so it was in compression.  When I saw the word strap I was
> imagining (for no good reason) that this thing might be in tension.
>
> Phil Ford
> _______________________________________________

I would guess the function is similar. Not a lot of the direct sting load is
coupled through these devices but they do serve the function of helping to
prevent the middle of the plate pinblock panel from rotating forward and
down. This does take some of the bending stress off of the inherently weak
plate strut located between the bass and tenor sections and, in theory at
least, should aid tuning stability.

No, the strap is not under tension. Nor much compression. Mostly bending as
in a beam, I should think.

Del