[pianotech] Belly talk

[Dale Erwin]

 At some point my eyes kind of glaze over with splittin hairs on certain things and this is one. So I see it this way thru my smoke and mirrors.
The inner rim has an approx 1 1/2 degree bevel cut into the inner rim at the factory. Set a straight edge on it & it becomes apparent.
  We have a soundboard, be it rib crowned or other wise crowned. I don't care. It is dome shaped. So it has an angle at the edges. or...said another way...It is not flat.  It rises in elevation from the edge to the highest point in the board. So whats wrong with having an approximation of that angle cut into the inner rim which will match the rise in elevation of the board in some approximation. 
Not a damn thing and not everyone in a factory who ever designed a piano their way is an idiot Ron. 
 
For what its worth I have glued in several boards to inner rims that were cut flat and it does indeed flatten out the board a little. I'd prefer that not to happen. Do I cut the rim trying to match some idealized rise in elevation. No. A waste of time.  But to be sure.... No one would want the inner rim to be beveled in the opposite direction. Would they?
jeez
Dale


Dale Erwin R.P.T.
Erwin's Piano Restoration Inc.
 Mason & Hamlin/Steinway/U.S. pianos
www.Erwinspiano.com
Phone: 209-577-8397

 
  





-----Original Message-----
From: Jim Ialeggio <jim at grandpianosolutions.com>
To: pianotech <pianotech at ptg.org>
Sent: Sat, Dec 1, 2012 7:17 am
Subject: [pianotech]  Belly talk


Right...

Regarding the "rasten", I'd like to take a step back, and come at this 
from a "what is physically possible" perspective.

For the moment lets leave all design intent aside and look at this from 
a what is physically possible perspective.  The question is "what are 
rebuilders actually achieving when they do this, as opposed to what do 
they think they are achieving".  To be clear, I'm not talking about 
tonal results here. I'm simply talking about whether, if one of us said 
they were going to bevel so-and-so piece of wood at such-and such angle, 
they actually did what they set out to do...ie the "as built" wooden 
joint matched their intent.

As someone with a background in setting up production runs where 
hundreds of 5 surface profiled joints had to fit dead nuts without hand 
adjustment, I had to learn how to prove what I was actually achieving in 
a particular process rather than assuming that I had achieved what I set 
out to achieve, wished to achieve, or though I achieved. Learning how to 
prove the "as built" conditions is a challenging task, much harder than 
one would expect, until one learns how to create and maintain 
trustworthy indexes.

For any of us the "as built" and the intent can sometimes be wildy 
different things. Further, its hard enough to match intent to result in 
set ups where the parts are all straight lines, but with a piano where 
straight lines are few and far between, and joints are cut in tough to 
access places, its a whole other kettle of fish.

I find this tug between intent and achieved results again and again in 
piano work.  In this work the tug is accentuated because there simply is 
not a trustworthy reference point or index surface to be had, unless one 
purposely sets out to create and prove one, and then refer and correct 
all work back to that known index.

So my take on this is, given my background, simply that the mating angle 
at the "rasten" is highly variable both from the rim's and the panel's 
perspective and thus unknown in its "as built" reality.  At least from a 
rebuilder's perspective, the rasten joint is physically impossible to 
actually achieve with the intent techs claim they are shooting for.  It 
only introduces complexity where the complexity takes on a mind of its 
own. I see the added complexity trying to control such a miniscule 
detail becoming gratuitous, and even worse fueling speculations about 
what one achieved without proving that one actually created the intended 
physical joint.

This in addition to whether there is any tonal advantage at all in 
theory. However this is hypothetical anyway, because probably its never 
actually been accomplished.

Add to this, that the majority of the "rasten" is along the short 
extremely flexible grain of the panel, and the claims of its value 
become more and more questionable.

Jim Ialeggio

-- 
Jim Ialeggio	
jim at grandpianosolutions.com
978 425-9026
Shirley Center, MA


 
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