Grand Bending & Square Grand Cheek Lift

[Farrell]

Hello Joe???? Or anyone. Joe recently described "cheek lift", where a square
grand case will twist and the back left corner and/or the front right corner
will rise up due to string tension. 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 belly troubles can be largely corrected upon rebuilding
by recapping bridges and/or lowering plate (remember, we are not talking
about the ultimate in performance anyway), but the action troubles would
persist.

How much cheek lift commonly causes how much trouble? Just reletive terms. I
can easily imagine 1/16" to 1/8" cheek lift will be of no major significance
on an instrument (furniture?) like this. At the other extreme, one-inch of
cheek lift would likely make the piano unplayable. About where is the point
at which performance is commonly significantly affected?

I measured 1/4" of cheek lift in the square I am refurbishing - with the
plate out for several months. How much can I expect the cheek lift to
increase when I reinstall the plate and bring strings up to tension? The
question being, does the amount of cheek lift in an old square grand change
much with strings in or out?

Do we ever see piano case bending (front to back) in a modern/traditionally
designed grand - i.e. does a Steinway D, a Bechstein A, or a Brambach grand
ever bend up (front to back) under string pressure? If a normal grand does
not bend, but the square does bend, is that because the case on the regular
grand resists bending more, and/or is it the plate on the modern grand that
is more stiff?

Thanks.

Terry Farrell