Tension Increase

[Billbrpt@AOL.COM]

In a message dated 1/4/00 5:18:36 PM Pacific Standard Time, 
staytuned@idirect.com (John Lillico, RPT) writes:

<< If one raises pitch 1/2 tone to A440, how much tension is added to the 
frame, either in percentage or pounds?
 
 I successfully carried this out yesterday on a Dominion (circa 1910) which 
showed signs of structural weakness with the treble pin block having pulled 
slightly forward.
 
 Just wondered how much extra stress I had caused. Tuning is scheduled in 
four weeks. >>

Hey John, it's a real pleasure to see you writing on the List.  Remember me, 
the guy who starts talking with a slight French accent whenever he is hanging 
around with those *Parti Québecois* Members?  I really appreciate all the 
work you have done in the past by serving as the Convention Director.  Too 
bad you couldn't attend the classes or you might already have known the 
answer to your question!

I have always heard that a 1/2 step pitch raise put 2 tons of tension overall 
on the piano.  Ron N.'s example bears this out:

<<Here are some figures from the original scale of a grand I rescaled. 
Total Tension:
@A=440=37555lb  at pitch
@A=428=35535lb  1/2 <> semitone down
@A=415=33409lb  1 semitone down
The figures on your piano would be different, of course, but this should
give you some place to start. >>

Regardless of how much it is though, it doesn't seem wise to try to raise the 
pitch against a condition of structural failure.  I say this even though we 
all may have done it against a cracked or checked bride cap, a severely 
cracked soundboard or bass bridge apron.  But a separating backframe 
structure is more serious than a soundboard or bridge problem.  Sometimes, 
however, a slight failure in the pinblock/backpost/backframe structure is 
little more than cosmetic.

>From what I read in this case, I would bet that when you go back, you will 
find the treble section is now considerably flat.  If repair is not going to 
be done, I would suggest that you reestablish the pitch from the average 
pitch to which the treble has settled and lower the rest of the piano to it.  
This will still take you at least 2 passes to get things straightened out and 
as stable as it can be under the circumstances.

In the future, if the treble keeps going flatter and especially if the 
separation worsens, tell the customer that repair is required.  Otherwise, 
you may eventually break the plate because it may encounter stress in the 
wrong direction.  If however, the separation is somewhat cosmetic and stable 
as another person suggested, there would be no danger in tuning at A-440.  
There still could be some stability problem.  A climate control system and 
establishing a pitch at which both the piano and the customer are 
*comfortable* would be in order.

Regards,

Bill Bremmer RPT
Madison, Wisconsin