Call for scaling spreadsheets

[Ron Nossaman]

>  But perhaps I should also have 
> suggested that to make a proper job of it, one ought also to have new 
> metal frame cast and a new keyboard.  Without that surely the job will 
> be a compromise, won't it?  

Of course it will, but compromised from what? If the original 
was perfect, there wouldn't be a need for even rescaling, or 
action leverage and balance changes, much less adding bracing 
and ribs, and repositioning bridges. The intent is to make a 
less compromised piano than the original to the degree that I 
am able within the limits of my own capabilities and the 
physical constraints of the plate and case. Perfection isn't 
possible, of course, but a calculated compromise is better 
than a random guess any day. Even if it doesn't work as well 
as it might, you have some information to begin to understand 
why.


>In the design of a piano the first line that 
> is drawn is the strike line, and every other significant point in the 
> design is drawn in relation to this line. 

True, but I'm not designing pianos from scratch. I'm trying to 
minimize the damage done by the original designer of an 
existing instrument.


> Suppose you now redraw your bridge to produce a tension on this note 
> (assuming for argument's sake the same gauge of wire) of about 160lbs, 
> then you will need to reduce the length of the string by 11 cm to 65 
> cm.  You will thereby achieve, nay even over-achieve, your desired 
> back-length, but what of the strike point?  This will have moved nearly 
> 14 mm. nearer the front bridge.  Surely the only ideal solution then is 
> to move the whole string back 14 mm in order to bring the strike point 
> back to the strike line.  In other words you need to reposition the stud 
> (agraffe) in the metal frame unless the hammer is to strike the string 
> at a less than ideal point and produce less than ideal harmonics.

It's unlikely that I'd make that drastic a change that high in 
the scale, but if I did, that whole section would have been 
similarly changed and it would all sound much alike, so it 
wouldn't likely be a problem.  The biggest concern with strike 
points in the lower half of the scale is at a discontinuity 
from one note to the next. This does happen at the bass/tenor 
break where I've put a transition bridge on the low tenor, 
with considerably shorter speaking lengths to improve the 
crossover. Yes, in principal you would want to move the 
agraffes to get whatever you might deem to be the ideal strike 
point, or at the very least to eliminate the discontinuity. 
I'd love to have the luxury of doing so, but I don't when I'm 
working around an existing plate, so there will be a strike 
point discontinuity there. The reality is, however, that I 
have yet to do one of these without significantly improving 
the original crossover, even with the strike point in a not 
quite ideal spot, and discontinuous at the transition between 
wrapped bichords and plain trichords. It just hasn't proved to 
be a problem in practice that low in the scale.

Ron N