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. > > > >
This PTG archive page provided courtesy of Moy Piano Service, LLC