[CAUT] Checking

[Fred Sturm]

Hi Jurgen,
    I have a guess. The felt shoulders of the hammers can tend to hit the
tops of the checks (with the flexes and compression of shank/felt/leather)
on return. This will happen more, obviously, with the thicker hammers than
thin, hence the taper bass to treble. I have certainly had problems relative
to this with Steinways, in tenor especially, where the shoulders actually
catch and stick to the checks (I¹d get a complaint about a ³sticking key² -
in this case sticking on the upstroke). Thickness of the ³rest² felt
(pillow, or newer damper style on the end of the wipp) and its relationship
to the shank position at rest plays into this, as does check height. I guess
Steinway is addressing this problem in making that recommendation for
tapered check height. I suspect they also recommend tapered check distance.
    Which brings up another issue that hasn¹t been mentioned, or very
little, in the discussion of checking issues. That is the upstroke, and the
geometry involved in allowing the tail to miss the check. This includes the
profile of the tail, its length, the angle and profile of the check, and its
height. I don¹t have a good handle on what the parameters should be, but
there are a few good principles: smoothly curved profile of the tail, no
³bump²; there is a limit to how high the check can be relative to the shank
at rest, and this varies a bit with tail length; angle of check needs to be
within fairly tight parameters, and these seem to be essentially the same as
for good checking on the ³downstroke.²
    One can figure out quite a bit about what might be wrong with a checking
system by setting the check distance a wee bit close, then playing a key
while offering resistance to the hammer and observing what happens: where
and how does the hammer hit the check on the upstroke? What change would
allow it to miss? 
    The bottom line is that seemingly tiny differences in angle, height,
curvature, surface condition etc. can make all the difference in function. I
have long been puzzled as to why Steinways seem more touchy than many other
brands (leaving aside the ³too short tail² problem). And why some Steinways
are much more problematic than others, even with apparently identical
geometry and parts.
Regards,
Fred Sturm
University of New Mexico


On 12/22/06 5:18 PM, "Ted Sambell" <edward.sambell at sympatico.ca> wrote:

> Jurgen it makes nosense to me either.
>  
> Ted Sambell
>> ----- Original Message -----
>> From: Jurgen Goering <mailto:pianoforte at pianofortesupply.com>
>> To: caut at ptg.org
>> Sent: Thursday, December 21, 2006 2:04 PM
>> Subject: Re: [CAUT] Checking
>> 
>> Yes, Thanks Alan for the S&S backcheck info.
>> 
>> One question: Given an assumed constant tail length and bore length (within
>> bass and treble) I don't quite understand why the backcheck height "increases
>> linearly (with respect to note number) from 3 3/8" for note # 1 to 3 9/16"
>> for note # 88".
>> 
>> Can someone clarify this?
>> Also, would these dimensions be the same in all models?
>> 
>> 
>> Jurgen Goering
>> Piano Forte Supply
>> (250) 754-2440
>> info at pianofortesupply.com
>> http://www.pianofortesupply.com
>> 
>>> 
>>> Alan,
>>> Thanks for the copy of the instructions.
>>> 
>>> The first time I heard of raising the backchecks was from Scott Jones
>>> teaching at a regional seminar. I think he also talked about using a snap
>>> ring pliers. Kevin Stock, also with S&S for a time, had a modified snap
>>> ring pliers with a slot cut out for the wire. He would just lift them, then
>>> even them out. I think that's because he knew what he was doing
>>> intuitively. It was Roger Jolly that I first heard put some numbers which I
>>> need with the idea;.... tail arc radius at 1/2 the hammer hanging distance
>>> (usually right around 2 1/2), shank intersecting roughly the top 1/3 of the
>>> backcheck (this does not need to be fussed with if the hammer line gets
>>> raised from filing or whatever), and the backcheck angled back 18 degress
>>> from vertical (pretty similar to the 68 or 70 degrees you work from, just
>>> different point of reference and 4 deg. different). I always enjoy hearing
>>> the different approaches to the same thing, because not all things work the
>>> same for everyone, (not wrong, just different) and it is also good to get
>>> something reaffirmed by a seperate source. A different perspective can
>>> turn the light bulb on.
>>> 
>>> Tim G
>>>> 
>>>> Attached is a S&S document about installing backchecks.
>>>> 
>>>> Have a great break!
>>>> 
>>>> Alan
>>>> 
> 


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