Low Inertia

[David C. Stanwood]

Hi Dale,

Your e-mail came through with alot of question marks!!! I think your 
computer is confused.....

As I said the cp heights were all almost 1/4" low.... and the string 
height was a little high..  we raised the stack up as high as we 
could without the drop screws being in danger of hitting the wrest 
plank. This was a 1947 D.

Chris Solliday and I worked on a 1946 D which had the cleats in 
backwards  The wip centers were way way low... no one could ever 
regulate that piano until we put the cp heights back to spec by 
replacing and reorienting the cleats.... and getting the cp heights 
back to spec...

I think it was so soon after the war effort and maybe they were out 
of practice after making so many Gliders....!

David

? David
? This?is a fascinating development! I'm curious. How high was the 
hammer flange center pin from the keybed before it you moved it 
up??The blow was the same ?
? By the way what vintage of D? Do we ever know enough...rhetorical question
? Thanks
?? Dale
?

Dear all,?
?
Before these related threads scatter into oblivion I want to restate 
what I've already mentioned in the Journal past: it is my observation 
that distance ratio divided by weight ratio yields something I call 
the efficiency ratio which is a ratio of ratios....?
?
As an example I was recently working in John Foys shop to help 
install a Precision Touch Design in a Steinway D. We found that with 
a 5.5 ratio the distance ratio was 5.0. The efficiency ratio was .9 
and the action required a .430" dip with a 1.75" blow.... We checked 
the action center elevations and the whole stack was low by almost 
1/4". Rechecking the ratios the weight ratio was 5.3 and the distance 
ratio up to 5.7 which was kind of astonishing. The efficiency ratio 
was now 1.1 and the action regulated with .400 dip...?
?
This is just one example and I'm collecting much more data to 
formally publish but I can say at this stage that it is my conclusion 
that the efficiency ratio should be above 1.0 for good results...?
?
To me distance ratio comes under the heading of geometry and is 
related to arcs and their angular interaction whereas the strike 
weight ratio is a result of vertical gravitational vectors.?
?
I like what Fenton said.... it's about Hammer Weight, Action Ratio, 
Geometry and Friction....?
?
Onward and upward....?
?
David Stanwood?