Hi Ron, My apologies for misinterpreting your question. I understand now what = your asking, and I have tried a very un-scientific, but possibly = enlightening experiment this evening. I am currently doing some work on my personal piano in my shop. I = rebuilt this piano (a Bradbury 5'6" reproducer grand) about six years = ago, and it happened to be my first bridge recapping job. Because of = this some of the bridge pin placement is, well, pretty embarasingly = wacky. A few pins are placed in such a way that there is very little, = if any side bearing. The rest of the job is fine: good downbearing, nice = tight well angled bridge pins etc. I took some strings off and checked = bridge pins and found no *visible* notching in them. I got to thinking that this would be a great situation to test if side = bearing played a major role keeping the strings off the bridge. Here's what I did: With the piano up to pitch, I simply pulled up on the = speaking lenght side of a couple of strings until they lifted off the = bridge, then let go and watched what happened. The strings that had no = side bearing went right back down to the bridge. The strings that had = decent side bearing stayed up! I did several in the sixth octave of the = piano (this is where the misplaced pins are) and the strings rode up = above the bridge anywhere from 10 to 15 thousandths according to my = feeler gauge. This little test, while not very controlled, would seem to point to side = bearing, and its attendant friction as one of the major contributing = factors in keeping those suckers up in the air. Comments anyone? John McKone, RPT St. Louis Park, Minnesota (612) 280-8375 ----------------------------------------------- >From : Ron Nossaman <nossaman@southwind.net> Sent : 04/11/97 To : pianotech@byu.edu Subject: Re: bridges/seating At 08:58 PM 4/10/97 -0600, you wrote: >Ron, > >If you're asking why the string can creep up against the pressure of = downbearing and friction, you need look no further than the impact of = the hammer (on a grand anyway) Especially on a hard use piano. > >John McKone, RPT >St. Louis Park, Minnesota >(612) 280-8375 > Nope, nope, not at all. It's quite obvious that a string can be knocked = up hill against tension, friction, or anything else you care to name. = You can here it happening if you work at it. It's quite clear to me how = a string GETS up a bridge pin. I'm saying that it's not possible for it = to STAY up off the bridge, AT REST, against tension and side/down = bearing and pin angle, unless there is something physically wrong with = the bridge pin. What else would hold it up there magically???? David = Copperfield plating? There has to be a real reason for an observable = physical phenomenon. I get enough mysticism and "have faith, trust me" = metaphysics from Government. Demonstrations can illustrate that it's = possible (I'm still working on that one), but I don't think anyone can = realistically champion a fix without a clear understanding of what's = broke. Let's talk "mechanism". I'm willing to accept the notion that = this happens only in the context of a rational explanation as to WHY it = is possible. Wouldn't you like to know too? Ron Nossaman
This PTG archive page provided courtesy of Moy Piano Service, LLC