Frame Cracked Twice, Engineering help?

[Delwin D Fandrich]

----- Original Message -----
From: Roger C Hayden <rchayden2@juno.com>
To: <caut@ptg.org>
Sent: March 21, 2000 6:28 PM
Subject: Re: Frame Cracked Twice, Engineering help?


> Del,
>
> You may be right.  I had simply taken a little material out of the
> soundboard at each bolt and turned down the nose bolts a tad, because
> there had been too little downbearing before.   I had failed to keep good
> track of shim placement when I took the piano apart, and did not
> 'rediscover' them, neatly packaged and labeled, until after the plate was
> down.   There were four 1/4 inch and less shims in the high treble under
> that last section.
>
> So I would guess that you would consider my crack caused by my torquing
> the frame at the high treble.
>
> The Crack begins near the last nosebolt, at a thin part of the frame
> under and to the right of the strut. That strut houses the highest
> nosebolt.  From there the crack heads to the upper right, ending about
> four inches in.  You make me think that I have stressed the frame by
> perhaps leaving the bolt too high, then leaving out the shims, forcing
> the frame unnaturally.
>
> Does this make sense?
>
> Roger Hayden, RPT
>
> PS, the owners were here last night, the husband said his wife had been
> crying for four days.  HOOooboy.
------------------------------------------------------

Roger,

I would say you have probably found the cause of the crack.  This is good.
It means that the problem can be corrected, the plate welded once again and
all will be as good as new.  This is an area of the plate that is normally
very lightly stressed.

Weld the plate once again per Vince's recommendation.  This is not rocket
science.  Just make sure the welder is one who is familiar with welding cast
iron.  If you can find someone who welds very old, as in antique, cast iron
engine blocks you're off to a good start.  If the antique auto rebuilders
trust him/her, so would I.  With the plate welded once again and filled and
finished neither you nor your customer should be able to see any leftover
signs of the crack.

Now.  Lower the nosebolt(s) until it, or they, are fully out of the way.
Replace the appropriate shims and/or make new ones to establish proper
downbearing and to make sure you have good, solid contact between the plate
and soundboard/rim at each rimbolt location -- i.e., make sure the plate is
not stressed at any point.  (If you are changing plate height back near the
bridges you might also want to check to see how the pinblock fits down
against the inner rim.  Pinblock thickness is often the determining factor
in establishing plate height at the fore end of the plate.  Sometimes there
are some shims that fit between the bottom of the pinblock and the inner
rim.)  With the plate screwed down tightly, bring up each nosebolt until you
just have contact.  Put the nosebolt nuts on, tighten them down and string
the piano.  You should not have any further trouble.

Regards,

Del