What is the "spine" in a square grand? Terry Farrell ----- Original Message ----- From: "Clark Panaccione" <threesixesinarow@yahoo.com> To: <pianotech@ptg.org> Sent: Sunday, September 23, 2001 12:19 PM Subject: Re: Grand Bending & Square Grand Cheek Lift > Farrell wrote: > > > Can anyone quantify the potential problems? I can > see that regarding > > the belly, it will lessen downbearing, and > regarding the action, it > > will cause the action frame to not sit flat on > keybed, or if it does > > curve with the keybed, the hammer height will get > affected, etc. > > The construction of squares is that the action sits > where effective framing might be. This is counteracted > a little for late squares which have substantial > wooden nameboard stretchers and nearby bass struts, > but their effect is lessened by over stringing and > relatively high tension. Bottom boards often are > oriented to the main direction of the strain but which > are coupled mostly through the case sides, with grain > oriented parallel to the bottom which can distort some > even before transmitting some of the burden to it; > further, if a bottom is solid, it cannot resist any > non-longitudinal, twisting strains so well. > > Another weak point in old squares is at the > intersection of the spine and treble end of the wrest > plank, a sort of sinusoidal distortion can be observed > by sighting along the spine. Even while there may be > no such evidence, you may see a flange or thicker > section of plates in late squares around this same > area. > > > The question being, does the amount of cheek lift in > an old square > > grand change much with strings in or out? > > Yes, but probably you're familiar with compression set > through Del Fandrich's posts regarding soundboards. > This is another sort of creep, like to old shelves and > beams sagging under continuous load which will spring > back when the load is removed but not fully. > > > Do we ever see piano case bending (front to back) in > a > > modern/traditionally designed grand ... ever bend up > (front to back) > > under string pressure? > > It is very common in old wooden framed grands. I just > checked my oldest grand, ca. 1860 which doesn't > exhibit this - however, its top strut is 70mm high and > which is mortised into the cheek. > > > Clark > > __________________________________________________ > Do You Yahoo!? > Get email alerts & NEW webcam video instant messaging with Yahoo! Messenger. http://im.yahoo.com >
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