Is that plate broken?

[Delwin D Fandrich]

Ken Hale wrote:
> 
> ...My question is how would one go about making sure that there are no
> fine cracks? One could be on the underside and not cause problems
> until one late night when the wood is creaking or I am sitting there
> lost, in listening to those beautiful intervals and shimmering beats.
> 
> I actually can not think of any way to be 100% sure, besides
> destringing and maybe taking it to the auto repair place for one of
> those "what-da-ya-call-its" where they test for cracks in engine
> blocks. There is insurance that would probably cover it, but is it
> really necessary?
> 
> I would appreciate hearing anyone else's experience with these kinds
> of situations.
> 
> Thank you,
> 
> Ken Hale, RPT
> ~~~~~~~~~~~~~~~~~~~~~~~~


Hi Ken,

As you suspect, there is no way to be 100% certain that there is no
hidden or residual damage from a fall of this sort. However, you can be
about 99.87% sure, which is probably good enough.

Of the several plates I've seen damaged in a drop, they have always
broken on impact. Those, such as the Steinway, using hard maple rims and
several nose bolts seem to survive with no apparent damage to the plate
or rim structure at all. Those with poplar and/or "Select Hardwood" rims
tend to have stripped out plate bolt/screws, etc. Of course, the plate
bolts/screws could well have been stripped out before the piano was set
up so the pianist could play it on his back. (We seem, somewhere, to
have gotten the idea that plate screws/bolts need to be tightened to
about 295 ft. lbs. of torque every time the piano is tuned. OK for
maple, not for Select Hardwood.)

I agree with Danny Moore. Magnaflux testing probably wouldn't tell you
much. It might frighten you more than necessary, but the results would
probably not be of much value. Plates do go through a lot of trauma as
they cool. The iron shrinks as it cools. But it doesn't shrink
uniformly. Large cross-sections cool at a different rate than do narrow
c/s's. The result is a cool plate that has all kinds of stresses in it.
Some of these manifest themselves in twisted and warped sections—have
you ever laid a straight edge along the bottom of a pinblock web, for
example. You can bet that the pattern was flat. The web rarely, if ever,
is.

So. Tighten the bolts if you must. Check the nosebolt blocks—you know,
the blocks bolted to the sides of the belly braces—to be sure they
haven’t shifted any. Fix the action. Fix the fallboard. Tune the piano.
Enjoy.

—ddf