[CAUT] Lacquered hammers

[Delwin D Fandrich]

Mine shows it a little lower but still higher than I'd consider safe. 

Considered switching from a wrapped bi-chord to a plain steel tri-chord?
According to my spreadsheet this might actually work better. F#-3 (note 34,
right?) with a length of 865 mm and plain wire of 0.041" to 0.043" diameter
looks acceptable depending, of course, on what is above and below. 

ddf

Delwin D Fandrich
Piano Design & Fabrication
620 South Tower Avenue
Centralia, Washington 98531 USA
del at fandrichpiano.com
ddfandrich at gmail.com
Phone  360.736.7563

-----Original Message-----
From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of Ron
Nossaman
Sent: Sunday, February 20, 2011 2:22 PM
To: caut at ptg.org
Subject: Re: [CAUT] Lacquered hammers


Speaking of less than stellar scales in production pianos (and speaking of
Samick), last week I tuned a Samick SU-143M, that I had tuned for the last
five years or so. The low string of the F#-3 bichord popped as I pulled it
up to pitch. Two splice attempts also popped, so I brought it home for
replacement. Out of curiosity, I took measurements and put them in my
scaling spreadsheet. It's an 0.032" core, 0.047" outside wrap diameter, and
an 865mm speaking length. According to Sanderson's math, that puts it at 73%
of breaking strength at pitch. That goes a ways toward explaining why the
splices failed.

So here we are. The wrap is about 0.007, which is already smaller than I
like, so there's no hope of increasing the core and reducing the wrap. 
You know that in plain wire, the break% doesn't meaningfully change with a
wire size change. With wrap this small, a similar situation occurs. By
increasing core size to 0.036", with 0.007" wrap, I can get 66% break, and
let the inharmonicity fall where it may. What I'd like is about a 100mm
shorter speaking length, but that's hard to get with a field repair.

Welcome to the world,
Ron N