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<DIV>Hi Dale,</DIV>
<DIV>An uneducated guess here. Are you also reducing the size of the rib =
some,
seeing that it is also stronger?</DIV>
<DIV>Joe Goss RPT<BR>Mother Goose Tools<BR><A
href="mailto:imatunr@srvinet.com">imatunr@srvinet.com</A><BR><A
href="http://www.mothergoosetools.com">www.mothergoosetools.com</A></DI=
V>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>
<A title=Erwinspiano@aol.com
href="mailto:Erwinspiano@aol.com">Erwinspiano@aol.com</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A =
title=pianotech@ptg.org
href="mailto:pianotech@ptg.org">pianotech@ptg.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Saturday, February 18, =
2006 9:04
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: laminated =
ribs</DIV>
<DIV><BR></DIV><FONT id=role_document face=Arial color=#000000 =
size=2>
<DIV>
<DIV> <FONT size=3> Ok, now this is an interesting =
discussion.
Admittedly not being a math guy I'm still interested in putting some =
numbers
on some scales of things I've seen as a bench marks for
comparison.</FONT></DIV>
<DIV><FONT size=3> Let's just take one case I have =
first
hand knowledge of. I rebuilt & 1960 Stwy L 3 years ago that =
lived in
a Fresno area church from the beginning of it's creation to the =
present so it
has survived wonderfully well.</FONT></DIV>
<DIV><FONT size=3> I was keenly impressed by the =
balance of
sound, both in power & sustain. I measured the bearing =
with a
lowell gauge & though I don't have numbers any more to give you my =
recall
is that the top capo had over 2 degrees of deflection & the =
2nd capo
about 2 or more & the middle was 1 1/2 =
degrees
tapering down to 1/2 in the bottom & the bass had =
positive but
minimum bearing as it should be with a cantalever. The crown =
string
stretched across the boards underside revealed lots of residual crown =
in the
strung condition & more than any other C.C. board I've ever seen =
up
to that time. All that to say it was in my opinion a text =
book
Steinway/belly set up both in terms of crown & =
bearing.
These are IMO the kinds of observations that are important to =
make
when we find something that is working really well. </FONT></DIV>
<DIV><FONT size=3> The Stwy L scale as I recall has an average =
treble
tension at 160 lbs per string. It is obvious to see that the majority =
of the
bearing pressure on the long bridge is increasing gradually the =
higher
up the scale we go. </FONT></DIV>
<DIV><FONT size=3> So knowing all of the above, what is the =
equation
that will calculate an approximate string bearing load under the =
conditions I
describe?</FONT></DIV>
<DIV><FONT size=3> If it's the one- 40th rule for simplicity =
then
40 divided into 160 strings equals 4 pounds per =
string. Let's
remove most of the bass strings from this equation for now, since
theoretically there isn't much bearing there & we have approx. 160 =
strings
times 4 pounds equals 720 lbs. add in say 80 lbs for the bass =
& it's
about 800 total pounds give or take</FONT></DIV>
<DIV><FONT size=3> There is a much more =
accurate &
glamorous formula for this but I dont' have it at my finger tips. =
If the
scale tension averages 180 lbs per string then we're talking 4 1/2 =
pounds per
string which bumps total bearing load up another 100 =
ish
pounds.</FONT></DIV>
<DIV><FONT size=3> My point in all this is that if we are =
using stronger
engineering materials & principles which building better stronger =
rib
structure, which we are<STRONG>, <U><EM>then</EM></U></STRONG><U><EM> =
surely
our rib crowned & supported boards will survive as well & IMO =
longer
than this example of a C.C Steinway L I cited above
</EM></U></FONT></DIV>
<DIV><FONT size=3> Don't you think?</FONT></DIV>
<DIV><FONT size=3> Dale Erwin</FONT></DIV>
<DIV><FONT size=3></FONT> </DIV>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px =
solid"><FONT
style="BACKGROUND-COLOR: transparent" face=Arial color=#000000 =
size=2>
<DIV dir=ltr><SPAN class=953463523-18022006><FONT face="Comic =
Sans MS"
color=#000080 size=3>Consider a basic scale of moderately high =
tension. Say
40,000 lbs. overall. With this string tension 1,000 lbs of string =
down force
equals 2.5% of scale tension. That is quite a lot considering that =
most
companies are claiming string down force more on the order of 0.5% =
to 1.5%
of string tension (which would be 200 to 600 lbs). I thought I was =
setting
my initial string down force pretty high at around 1.0 to 1.5%. I =
don't like
thinking about what I'd be doing to a board loading it up to 2.5%. I =
can't
imagine it being happy enough at that level to want to stay
there.</FONT></SPAN></DIV>
<DIV dir=ltr><SPAN class=953463523-18022006><FONT face="Comic =
Sans MS"
color=#000080 size=3></FONT></SPAN> </DIV>
<DIV dir=ltr><SPAN class=953463523-18022006><FONT face="Comic =
Sans MS"
color=#000080 =
size=3>Del</FONT></SPAN></DIV></FONT></BLOCKQUOTE></DIV>
<DIV></DIV>
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