Cracked plate

[Mark Wisner]

A small caliber gunshot. 

Mark Wisner
Piano Service
Yamaha Corporation
mwisner@yamaha.com

>>> stephen_airy@yahoo.com 12/13/01 10:20AM >>>
I'm curious about something -- what does it SOUND like
when a plate cracks, as compared to when a
double-covered string breaks in the bass section?


--- John Delacour <JD@Pianomaker.co.uk> wrote:
> At 7:13 AM -0600 12/13/01, Todd Mapes wrote:
> 
> >This week I experienced my first cracked plate. ...
>  I then 
> >explained the pitch raise procedure that I
> performed and told him 
> >that to the best of my knowledge, I had exercised
> due professional 
> >care ....
> >So, that brings me to the questions - Have you or
> anyone you know 
> >been sued because of a cracked plate?  If so, how
> did you defend 
> >yourself in court and what was the ultimate
> outcome?
> 
> I'm sure your client hasn't a leg to stand on.  If a
> plate cracks, it 
> is almost certainly the maker's fault and in this
> case the plate 
> almost certainly had a crack 3/4 the way through the
> metal either 
> since new or for a long time.
> 
> In Europe every technician is familiar with cracking
> plates in 
> certain old Bechstein grands.  These plates were
> installed "green", 
> ie. without being weathered, and besides, the
> pattern-maker made the 
> corners far too sharp and inadequately filleted so
> that the plates 
> have terrific internal stress from the beginning. 
> These plates can 
> crack in four or five places.  If one of these
> should open up during 
> a pitch raise or a move or just spontaneously,
> that's just the 
> owner's bad luck.
> 
> Whenever I restring a piano now, I warn the customer
> that in the very 
> unlikely event of the plate breaking, I will take no
> responsibility. 
> I was very lucky once to notice an incipient crack
> in a bar of an 
> Ibach grand I was about to rebuild.  I phoned the
> customer and warned 
> her the bill would be higher, since I'd need to have
> the plate 
> stitched.  Indeed, when I took off the tension, the
> crack widened and 
> the bar parted.  I thanked goodness I'd covered
> myself.  The cause of 
> the original crack was pure maker error;  the plank
> did not mate with 
> the underside of the plate and the forcible screwing
> down of the 
> plate to the plank when the piano was made had
> introduced an 
> insupportable stress.
> 
> The piano you are dealing with is obviously for the
> scrap heap, but 
> cracked plates can be stitched successfully using
> the Metallock 
> process.  This involves a special dumbbell-shaped (
> =O=O=O=O= ) 
> "rivet" of high-tensile nickel which joins the two
> parts together. 
> Metallock have centres in various places and a man
> comes out to the 
> job. Very impressive and, in my limited (thank
> goodness) experience, 
> quite successful.  Cast iron CANNOT be welded or
> brazed.
> 
> Good luck with your client.  The best thing is to
> get one or two 
> reputable technicians to write to you explaining the
> situation and 
> show the letters to your client.  If he's adamant,
> it's his own 
> look-out.  You can sleep easy.
> 
> JD
> 


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