Is that plate broken?

[Delwin D Fandrich]

Maxpiano@aol.com wrote:
> 
> List -
> 
> In my first attempts at restringing grands, I was very uneasy that all the
> plates rocked a bit and I seemed unable to get a perfect fit, I believe
> always with the tail horn high.  Nothing has ever broken over the 20 years or
> so.
> 
> Then I bought an old Hamilton grand to fix up and resell.  Then when I began
> to take it apart I discovered that half the plate bolts were missing!
> 
> Nothing had broken, and when I set the plate back in, it rested perfectly
> flat.  Did the missing bolts help?
> 
> Bill Maxim, RPT

----------

No. But having them missing probably didn't hurt all that much either.
You just happened to find a relatively flat plate. (It does make one
wonder, though. Why were they missing?) 

Plates warp and twist quite a bit as they cool. There is often no way to
use a plate unless it is flexed somewhat on installation. This is quite
safe as long as areas of local stress are avoided such as over
tightening a bolt with no support under it. 

The only plate I've seen with a broken outer flange was one of these.
The plate was mounted on tapered wooden wedges that were set--not
glued--on the soundboard next to the plate bolts. Normally the pressure
of the bolted plate flange held these blocks in place. At some time,
however, one of them had loosened and fallen out. When the technician,
acting on advice he had received in a PTG Convention classe, tightened
the plate bolts down, this one never "bottomed." Instead, the outer rim
of the plate cracked across the bolt hole and into the plate panel about
3 or 4 inches. 

Fortunately, this was an area of otherwise very low stress. The piano
wasn't worth a whole lot and, with the owners knowledge and permission,
nothing was done to repair the crack. I advised the technician involved
to remove the bolt, measure the distance between the bottom of the plate
and the soundboard, make a new block and fit it in place and reinstall
the bolt. This was done and, the last I heard--it's been some years--the
piano was still fine.

--ddf