Backpost delamination

[Carlos Ralon]

Cy,
In the 60's I was sent by the selling dealor to tune a fairly new Gulbransen 
console. It was about 30cts low -- brought up to A440. The next week she 
complained that it was "way out" in the mid section. I returned and pulled 
the mid section up again about 30-35cts. You guessed it, next week the same 
problem. I had on all previously visits checked the plate and the entire 
structure.  This time with the lower panel off, I was again bringing it up 
when I heard the loudest bang, like a shotgun. A hitch pin flew out at the 
break hit my leg and came to rest on the other side of the room.  I think 
the lady had an accident in the kitchen. Thank God the piano was in 
warrentee and was replaced.  Morale, don't think only of back post 
seperation, absolve yourself of any responsibilty before continuing, and, oh 
yes, leave the lower panel on when pitch raising.  ( This was my only one in 
over 50 years of tuning).
Carlos Ralon, RPT
----- Original Message ----- 
From: "Cy Shuster" <cy at shusterpiano.com>
To: "Pianotech List" <pianotech at ptg.org>
Sent: Thursday, April 05, 2007 7:42 PM
Subject: Backpost delamination


>I tuned a 1980's Wurly studio last August, and brought it up maybe 40 cents
> to pitch.  I measured the pitch before tuning it this month, and this is 
> one
> time that measuring really helped identify a problem.  The bass was maybe
> five cents sharp, but after middle C, it dropped off to 80 cents flat.
>
> I use TuneLab for pitch raises, and as I got to about C5, I heard the
> unmistakeable sound of wood fibers letting go with each movement of the
> tuning hammer (torque was OK).  The bridges were fine, so I looked over 
> the
> top at the backposts.  Each one is made of three sections of oak, and one
> joint had come unglued part way (about 1/4" deep):
>
> http://tinyurl.com/2rhoug
> (also see attachment)
>
> I've never heard such an immediate splitting noise in a backpost with
> raising pitch (and there wasn't much overpull at this point).  I'm 
> concerned
> about the pinblock separating, too, but its top is covered with veneer.
> What's the best way to unglue it to take a look?  Just iron a damp cloth?
> Should I look for a plate crack, too?
>
> It seems that a couple three carriage bolts should do the trick.  I could
> wick in some thin CA, too; I don't know if I could work epoxy in.  Is 
> there
> a better fix?
>
> --Cy--
>
>
>