what would happen if u raise the pitch of a old piano with completely new strings .will the soundboard crack ?.i have a question.does the sound board hold the tension of all 214 strings .or the Harp??

It is common to restring old pianos. A close visual inspection of the soundboard and bridges, (and the rest of the piano), should give you the confidence to restring the piano.

Same thing would happen with the new strings as if you pitch raised with the old strings, with maybe less chance of breaking a few strings in the process. Its good to record a few benchmark measurements of the strings downbearing first with a guage and then check the crown across the back of the soundboard with a string and the condition of the bass bridge extension. In some cases with pianos in poor condition, this will indicate its not a good idea to go ahead with a large pitch raise to begin with and you can avoid a disaster or inverting the soundboard.

The question should be considered BEFORE putting all those strings on the piano, don't you think??

1. Frame
....Is the structure of the piano sound? Are the backposts, sides, and all the framing of the piano in good condition?

2. Soundboard
....Is the soundboard whole? In one piece, without seperations, cracks, splits on the bridges, etc. Are the ribs in place and still attached? Is there any crown (positive curve) left in it? The bridges must get at least SOME load from the strings, or it won't sing for you.

....If the structure is sound the piano can handle the stress of the strings, most likely.

3. Plate
....The cast-iron plate supports the tension of the strings. In an older piano, as described, the strings are likely at 165 to 185lbs. of tension each. 214 X 185 = 39,590 lbs. of tension on the plate and structure. That's 20 tons of dynamic tension to play with. The plate, and the heavy framing that supports it, hold the greater part of the tension.

4. Soundboard
....The soundboard is only loaded with the side-bearing produced by the deflection across the bridges. In a piano with decent bearing the soundboard is carrying about 2500 lbs. of stress. (...and you re-builder guys can give us a more precise range) The soundboard can't carry the whole load of the strings, and shouldn't; it is supposed to vibrate!

....Again; the piano, if sound and of decent quality, can handle being pulled to full tension with new strings. If not; it is only a Piano-Shaped-Object. The strings and the scale are designed for a tension of A4 at 440Hz (unless the piano is REALLY old, and built for some lower tension). It simply won't sound right, or the scaling work properly, unless it is pulled up to where it was designed to be. So, if all else appears good .....go for it!

Respectfully,

Working with old soundboards is unpredictable and there are no guarantees. There is always a chance that a crack will develop. However, if the workmanship is sound, it will be aesthetics issue more than a tonal issue. One of my favorite sounding Steinways has a couple of good cracks in the board.

So the lesson here is don't make unrealistic promises to a client.