<html> <body> Otto- You said: <blockquote type=cite class=cite cite="">Okay, I misspoke here, & take your castigation with the proper...</blockquote> In my opinion, the main "mis-speak" would be: <blockquote type=cite class=cite cite="">...which came under the "Don't ever do that again!" category</blockquote> In fact, if you really want to know why it happened, you HAVE to do it again, with as many "controls" and measurements as possible.  Something had to have physically changed.  If so, it's discernable, and presumably, measurable.   If it did swell the knuckle, the hammer height would have changed.  That (in theory) might have caused blocking, but not, in my view, bobbling. Reiterating much of what Ed Foote said, bobbling can result  from the drop being too close to the string for a given ratio of checking efficacy, inadequate pinning friction (hammer and balancier) and excessive spring strength.  In other words, if the hammer will not check well on a soft blow, and the let off / drop is close with fast spring, bobbling will happen. (Checking problem could be due to: poor quality or condition buckskin; tail glazing; poor tail-backcheck interface angles; tail too short; too much hammer center friction; too much balancier pinning friction; excessive rep. spring - balancier friction; rep-spring too strong. There could be excess knuckle/jack friction prior to escapement (due either to jack being set too high above balancier, or too far under knuckle or quality of buckskin. How repeatable is the problem / solution?  What else did the spray contact?  Hammer pinning?  If the pinning friction was reduced, the rep spring would be relatively stronger, allowing closely regulated letoff & drop to be thrown back to the string.  Any chance spray got on tails or back checks? I'll be curious as to follow up. David Skolnik Hastings on Hudson, NY At 09:40 AM 3/4/2005 -0800, you wrote: <blockquote type=cite class=cite cite="">Ed, Okay, I misspoke here, & take your castigation with the proper consternation; eyes downcast with furtive glances at the "RPT's Guide to P.C. Technical Terminology", searching carefully for the inoffensive term. ;-)    I doubt that I'll succeed, mind you, but I'll try. I really appreciate the helpful suggestions you have all offered, and will indeed correct the problem with those in mind, praying that I don't have to re-pin the whole thing!  Without getting into a lengthy explanation, during which I'm sure I would manage to insert the other foot, what I was trying to say was that, while there did not appear to be a knuckle dragging problem (only my own) to impede the let-off, I would apply a bit of preventative maintenance in the form of a quick shot of teflon to keep them free.  (By the way Ed, your point is well-taken about the importance of the proper amount of friction in the jack/knuckle contact point -- a point I regretably forgot in the moment of transgression.)  This, of course, violated the "if it works, don't fix it" rule, setting up the subsequent chain of events. What piqued my curiosity here was the effect of the teflon spray on the problem.  I expected it to have little, if any, effect, but merely applied it as preventative measure to "keep things moving smoothly".  The results, however, provided a bit of learning which came under the "Don't ever do that again!" category, but I'm curious as to the "Why?" of the outcome.  I have used the product "Dri-lube" in the past without any ill effects.  And as such, I was wondering if any of you have had such experiences with this or similar products, and/or possible explanations. Thanks again, Otto ----- Original Message ----- From: <A440A@aol.com> To: <caut@ptg.org> Sent: Thursday, March 03, 2005 5:04 PM Subject: Re: [CAUT] knuckles & bobbles > Otto writes: > << Though there was not noticable friction on the knuckles, I decided to put a > > little teflon on them in the form of a dry aeresol spray to speed up > > repetition.  >> > >    I am not sure of the logic here.  How is reducing the friction at the > knuckle going to speed up repetition? > Repetition is dependant first on the height of the backchecking and then the > speed of the key return, (not the speed of the hammer rising from check, since > at fast repetiton, the hammer doesn't move up or down until the jack is once > again under it).  Is the very slight difference in knuckle friction going to > increase the return speed of the key? >    To my thinking, greater friction at the knuckle will cause there to be > more spring strength for the same speed of the hammer rise when released from > check.  This additional spring strength may be of use in speeding the key's > return, so reducing it may actually hamper repetition.  There is virtually no > difference in key return speed between a spring that causes a smooth steady rise > and a spring that kicks the hammer up fast enough to feel it in the key. >   If there are bobbles in the hammer, I would look first to let-off, then to > the interaction of the hammer tail and the backcheck and the friction in the > grub,(spring slot), and how much aftertouch you are allowing. Many times, I > have found bobbles when the spring was too strong for the system. Hammershank, > as well as balancier pinning is very important in this equation. If they are > too loose, the spring will be hard to regulate. >    Going even further, a loose jack pinning will allow the jack to fly back > and forth uncontrollably, and it may be that repetition will suffer from an out > of control jack.  Since my eyes are not able to discern such rapid movement, > this is only a theoretical question. > regards, > > Ed Foote RPT > <a href="http://www.uk-piano.org/edfoote/index.html" eudora="autourl"> http://www.uk-piano.org/edfoote/index.html</a> > <a href="http://www.uk-piano.org/edfoote/well_tempered_piano.html" eudora="autourl"> www.uk-piano.org/edfoote/well_tempered_piano.html</a> > > _______________________________________________ > caut list info: <a href="https://www.moypiano.com/resources/#archives" eudora="autourl"> https://www.moypiano.com/resources/#archives</a> _______________________________________________ caut list info: <a href="https://www.moypiano.com/resources/#archives" eudora="autourl"> https://www.moypiano.com/resources/#archives</a></blockquote></body> </html>