[pianotech] Yamaha C7 scale

[Nick Gravagne]

Hi Conrad,

String lengths and note numbers would help (I don't have a C7 scale in my
files). The C7 is a 7' 6" piano, so I expect that the first tenor note is
#21 or so.

Still, although your intuition makes perfect sense since the larger diameter
wires would require more tension in order to pull the larger mass up to the
same frequency, the facts don't quite support it. Given that the frequency
and lengths don't change, larger diameter wires will both increase tension
and inharmonicity. 

However, the inharmonicity number at note 21 will be about 0.10 give or take
a bit. What really matters is not the absolute INh value, but its
relationship to the general scale values, especially in the octave vicinity.
INh values increase exponentially (on a good scale) all the way up to note
88. 

I'm inclined (off the cuff) to like the lower gage numbers (19/18.5/18), but
that is just a guess. The larger gages may fit into the general scale
better. 

I am curious, and since I don't have a C7 in my files, if you like you can
contact me off list with string lengths and gage numbers for all the steel
strings (either inches or mm) and I would be happy to run a spreadsheet and
graph, no charge. You may like to see what the whole plot looks like.

Regards	

Nick Gravagne, RPT
Piano Technicians Guild
Member Society Manufacturing Engineers
Voice Mail 928-476-4143
 
-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Conrad Hoffsommer
Sent: Friday, March 06, 2009 11:56 AM
To: pianotech list
Subject: [pianotech] Yamaha C7 scale

Folks,

I'm midpoint in my new block and restring project (1977 and previously 
restrung w/4/0) and find a question arising re:sizes at bottom of tenor 
section.

I carefully miked the strings and found 20/19/18.
Cleaning the bridge, I found markings for 19/18.5/18.

I was planning to reuse the bass strings, so haven't measured them, but 
wonder if those of you who rescale as a matter of course would find a 
better scaling using the larger plain wire.

Just intuitively, I would think that the larger wire at that point would 
lower the inharmonicity and make the break even harder to smooth over. 
I'm thinking that I'll go back to the bridge markings vs:found sizes.

I've been wrong before.
-- 
Conrad Hoffsommer, RPT - Keyboard Technician
Luther College, 700 College Dr., Decorah, Iowa 52101-1045
1-(563)-387-1204 // Fax 1-(563)-387-1076