Frame Cracked Twice, Engineering help?

[Roger C Hayden]

Del,

Thanks for the advice on resetting the frame.  I'll pay closer attention
to my methodology the next time.

Roger Hayden, RPT

On Tue, 21 Mar 2000 22:51:13 -0800 "Delwin D Fandrich"
<pianobuilders@olynet.com> writes:
> 
> ----- 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
> 
> 
> 

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