[CAUT] CAF

[Fred Sturm]

On Aug 17, 2009, at 5:28 AM, Richard Brekne wrote:

> I'm still unsure of just how often the shank actually hits the rest  
> cushions... never really thought about it. I have run into the loose  
> rest rail thing as well, we all have but that thing will make noise  
> just in sympathetic vibration as well... so I am unsure as to what  
> that says about actual percentage of time the rail or cushions get  
> in contact with the shank. Its and interesting tidbit, a bit to the  
> side of this issue... but you've got my curiosity up :)


	There's the sympathetic buzz, but there is also a click on impact, if  
a nut is "just loose." And it happens typically from mf up in  
dynamics. Hence, the shank must be hitting the rail. I can't say I  
have done detailed research (checking exact regulation parameters and  
whatnot), but I have observed this very, very often, and with the  
shanks set at normal distance from the felt on the rail. So it is  
hitting the felt and compressing it enough to set the wood in motion.  
BTW, I find that most individual cushions on wipps have at least  
moderate indentations in the middle after years of play (especially in  
the middle where they are played more). It isn't because the shanks  
were resting on them.
	It is similar to my story about the jack top hitting the bottom of a  
flange. Try it in isolation on an action, press a key and see if you  
can get a jack to go that high. It really doesn't seem like it would  
ever happen. THere is too much distance, and even with very heavy  
pressure, there is plenty of gap. But fast, hard playing sets things  
flexing and compressing in ways that don't necessarily happen in our  
slow motion bench experience. Also true of tuning hammer flex. Tuning  
the top notes of an upright can tell you how stiff your hammer is  
(when it bangs into the case, even though there was a good large gap  
when you put it on the pin). What our common sense tells us is  
possible/impossible is often quite wrong in practice.
Regards,
Fred Sturm
University of New Mexico
fssturm at unm.edu