Xn Changes (was: Need a Mason Expert)

[Bill Ballard]

On 9/28/97,  Delwin D Fandrich, pianobuilders@olynet.com wrote:
>David,
>
>Yes well, just like with the sometimes inappropriate changes made to
>action geometry, not all rescaling work is done correctly. 

Golly Del, that remark seems to beg a discussion of  "inappropriate 
changes made to
action geometry". Certainly, it's well understood that in the matter of 
string scales, the inharmonicity introduced simply by coupling these 
srtings to a (relatively) massive soundboard panel is not going to be 
adjusted by changing wre sizes, etc. Nor is the business of soundboard 
induced inharmonicity going to reduce itself to simple formulas as  
neatly as is the strings' intrinsic inharmonicity.

As to "changes made to action geometry", the consequences of 
inappropriate changes are eseentially mechanical, and (because I can 
understand them) not terribly complicated. The trouble we can get into is 
limited to 1.) setting a key ratio which may put too long keystick of a 
long grand under too much stress (and risk of failure), and 2.) accepting 
a strike ratio solution to a hammer weight problem which for its 
execution requires to deep a keydip . In the work that David Stanwood 
(and I, as his student ) do,  screwing with the action srpead doesn't 
count for much. (Remember, gang, that the 3:2 ratio of the rep lever  is 
not the most effective place to make a change in overall leverage, but 
more importantly, changing the spread, ie. moving the rep center back or 
front, is moving the contact points -at the cap and the knuckle- in the 
same direction and are not changing the rep's leverage ratio.) Yet if 
there is one palce where the motion of parts can be moved out of 
comfortable working tolerances (and into jacks crushing into the front 
end of rep lever windows), the spread is where you can get into trouble 
the fastest. 

Sacred cows and divine burgers. Ten years ago, Ken Sloane published in 
the PTJ an description of how a heavy S&S D action was cured with a set 
of shanks whose knuckle mounting made the "jack-parrallel-to 
knuckle-molding" impossible. He did sort of miss that nifty aligmnet 
while he was looking at it during that step oif the regulation. But what 
those shanks did for the action resistence was far more important than 
some traditional benchmark (which by the time the pianist sat down at it 
was burrieds deep inside the action.)

I've got plenty to learn here and am an eager student. So, when we've 
straightened out that the proof of a good rescaling is not how it looks 
coming out of the printer, but how it sounds when the pianist sits downat 
the finished product, we can move on to "inappropriate changes made to 
action geometry". I'm all curled up at your feet and waiting <g>

Bill Ballard, RPT
New Hampshire Chapter, PTG

"You'll make more money selling my advice than following it" Steve 
Forbes, quoting his father, Malcom.