[CAUT] capsizing / catstrophic action failure

[Cramer@BrandonU.CA]

I often encounter repetition springs strong enough to hurl 
the hammer up out of check, but not strong enough to 
support the hammer assembly while winking the jack tender:

Symptoms: The jack won't return under "test" conditions, 
even with the rep. lever set much higher than tolerance. 

Note: The back end of the lever "bobs" (Ed Foote started 
the maritime metaphor!) up/down when you wink the jack. 

After several discussions and experiments, I'd kind of 
resolved loose repetition-flange pinning was the sole 
culprit.

However, on two recent instruments (Yamaha/Steinway) it 
was the hammer-flange pinning causing the problem. 

In each case, both the hamnmer and rep-lever flanges were 
in the 1g friction range, or less. Repinning the rep-
levers even to 7 or 8g slowed hammer-rise very little, 
meaning the springs couldn't be strengthened much, and 
didn't solve the support problem. 

However, repinning the hammer flanges to 3-4grams, did.

Regarding Steinway, the loose pinning (currently 20% RH at 
this particular venue), coupled with raising the hammer 
line several mm (key-dip; a very skinny .400") brought 
about the dread CAF on several notes. (see Eric's test)

I called David Kirkland at Steinway for help, and he had a 
set of rest cushions on their way before I could spit out 
the last digit of the instrument's serial number. 

Thanks David! 

Mark Cramer,
Brandon University

PS Sometimes the traditional rep-spring strength-test is 
indicating a loose center, not sufficient spring strength. 
Try the hammer center first.    




> >>
> >>"catastrophic action failure".  
> >>
> >>I have a test for this that I call the "absolute test 
for minimum action
> >>function" i.e. - will the note work?
> >>
> >>Play a note at a normal blow and after it checks, 
lower it to rest
> >>position very slowly. Then give the note a sharp blow. 
This will uncover
> >>a myriad of little problems which can result in non-
functionality.
> >>
> >>Eric Wolfley, RPT
> >>Head Piano Technician
> >>Cincinnati College-Conservatory of Music
> >>University of Cincinnati
> >>
>> >>Yea,  I learned that knots will capsize if tied 
incorrectly or used 
> >>incorrectly, just seemed to fit the action condiition 
formerly referred
> >>to as 
> >>"catastropic action failure".  
> >>Regards, 
> >>
> >>
> >>
> >>Ed Foote RPT 
> >>http://www.uk-piano.org/edfoote/index.html
>