While I still maintain that this topic is, in its entirety (including but not limited to stack height, magic lines, other friction, capstan height, and more), too large an issue in scope for email discussion, there are perhaps a few components (especially the one's already focused on) that shed light on solving the not so rare problem of lock-up on hard fast repetition, or as named by Eric Wolfley "catastrophic action failure." One of the reasons that this is considered rare is that it is not tested for frequently enough. And in many cases pianists don't challenge the action in this way so there is little complaining. But that does not mean that the potential is not present. Tighter pinning (within reason) of the balancier flange is a good first step in prevention. I very much like Susan K.'s description/rationale for this. Think for a moment back in time to an era when almost all wippens had balancier bridles attached to the support arm, made of soft bendable metal with felt cushions on the balancier, to prevent over travelling of the balancier. Those two parts disappeared as two things replaced them. Tighter pinning from Steinway and firmer felt covering for the rest cushions. For a while there were "bridles" and felt coverings. (Boy they must really have been afraid of this issue). I have covered soft cushions with strips of firmer felt just like generations of wippens gone by used to be, and found that this band aid works fairly well. I wished, however, that I could've added the bridle wire (probably a better name is available than this, but for now it is descriptive) in some cases. I think, however, that it is a band aid, just as adding felt of whatever firmness with glue to the top of a soft rest cushion firms the cushion enough to prevent over travel. I do not think that the dimension gained (or narrowed depends on which way you're looking) is as important as the firmness which is the real preventer of over travelling. Firm rest cushion and firm center with a firm spring. Three firms. Lately since "firm but free" (or is it "as free as possible without making noise?") has taken over action center design this problem has come back. I repeat that it is not this simplistic and that other issues of friction and geometry must be examined and corrected as well. However, I believe that we can fix (in the absence of the balancier bridle) most of the blame on "firm but free." I'm all for "firm but free" but not for the balancier. Here it does not work. Also the hammer flange cannot be too free either as I recall others mentioning and for good reason. The rest felt sold by Pianotek is currently made of a firmer felt and in different sizes for this very reason. Or you can cover the old very soft felt with a strip of firmer felt just like the older wippens did. I think that in this case history shows us the answers. Chris Solliday -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/caut.php/attachments/20090817/8c8994ed/attachment.htm>
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