Fw: scaling, hi-lo tension and other ponderables

[Carl Meyer]

Seems I sent this to the wrong address.  Sorry.    Carl

----- Original Message ----- 
From: "Carl Meyer" <cmpiano@comcast.net>
To: <pianotech-owner@ptg.org>
Sent: Sunday, July 20, 2003 1:33 PM
Subject: scaling, hi-lo tension and other ponderables


> I've had the urge to respond to many of the recent threads, but have
> successfully suppressed it till now.
>
> I'm going to tell you about my latest wild endeavor.
>
> Awhile back I found a Sohmer grand about 5'6" made in 1923. Since it had
> agraffes on the bridge (that has always fascinated me) I couldn't resist
and
> got it for $450.
>
> Now that a young man (compared to me) is interested in pianos, we are
going
> to rebuild???? it together.
>
> It sounded very bright and I thought it needed voicing.  Now, that we're
> getting into it,  here's what I've found.
>
> Note one    192 lbs tension
> note 12 (last unichord)   310 lbs
> note 13 (first bichord) 241 lbs (each string)
> note 26 (last bichord) 204 lbs
> note 27 (first trichord)109 lbs
> note 64 (highest tension trichord) 219 lbs
> note 88 189 lbs
>
> The total tension for the piano per pscale is 43672 lbs.
>
> So!!! A great opportunity to rescale.  Wound strings on the treble bridge?
> Sure!  I rescaled using pscale.  Total tension now 39423 lbs.
>
> OMG!  How do I get the wound strings through the agraffe on the bridge????
> I've used 6 notes of bichord wound to replace 6 trichord plain.  I'm
wearing
> my ear plugs now.  I know you all have ideas about that.  Here's what I've
> decided to do.  I will double up strings on 3 hitch pins, enlarge the 2
> outside holes of the agraffes of those 6 notes to .0625 to clear the
> windings and if necessary I'll elongate the hole at the bottom to clear
the
> swage.  The string pulls up on the agraffes and goes over a grassy knoll
on
> its way to the hitch pin.
>
> The board has good crown and downbearing, but I can't remember how I
> measured the downbearing.  I think I used the Lowell gauge.
>
> When I removed the agraffes from the bridge I thought they must have been
> touching the floor.  The threads were 1 1/4 inches long.  I wasn't
expecting
> that but it makes sense.  The threads were going through the bridge, the
> soundboard and a 3/8 strip of wood below the sound board.  No wonder I had
> problems trying to measure the crown with a string under the piano.  I
don't
> think this bridge will ever roll.
>
> Back to the scaling.  Not being that savvy about scaling, I was surprised
to
> find the breaking point percentage of note 88 to be 83%.  Changing the
wire
> size didn't do anything.  Hello?  I should have known that.  The speaking
> length was 58 mm.  Ah Ha!  Here the plot thins.  I'm sure you'll all say
> recap the bridge. (no agraffes for the top 18 notes and the bass bridge).
>
> If the breaking point percentage is 83 at pitch,  I don't even want to
know
> what it is at 20-30 cents stretch.  There was one wire broken when I got
the
> piano and one wire that had been replaced, but not at the top.  Maybe 8
> notes from the top.
>
> It has lasted since 1923 so I will just close my eyes, put on my goggles,
> pray and string it like it was at the top octave.
>
> As always your comments are welcome, but be warned.  My decisions are
always
> filibuster proof.
>
> I had first thought that I should sell it to a jazz musician who would
> appreciate a bright bright sound, but they would be the ones to break
> strings so I guess I should sell it to a light weight grandmother that
only
> plays rock-a-bye-baby.
>
> Regards to all
>
> Carl Meyer Ptg assoc
> Santa Clara, Ca.
>
>
>
>