<HTML> <HEAD> <TITLE>Re: [CAUT] Checking</TITLE> </HEAD> <BODY> 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 (I’d get a complaint about a “sticking key” - in this case sticking on the upstroke). Thickness of the “rest” 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 hasn’t 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 don’t have a good handle on what the parameters should be, but there are a few good principles: smoothly curved profile of the tail, no “bump”; 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 “downstroke.”     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 “too short tail” 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@sympatico.ca> wrote: <BLOCKQUOTE>Jurgen it makes nosense to me either.   Ted Sambell <BLOCKQUOTE>----- Original Message ----- From: Jurgen Goering <mailto:pianoforte@pianofortesupply.com>   To: caut@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@pianofortesupply.com http://www.pianofortesupply.com <BLOCKQUOTE> 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 <BLOCKQUOTE> Attached is a S&S document about installing backchecks. Have a great break! Alan </BLOCKQUOTE></BLOCKQUOTE></BLOCKQUOTE> </BLOCKQUOTE> </BODY> </HTML>