Hi Terry, Each of those metal inserts is usually called the "horn wedge." The horn is that large protrusion of the metal plate hanging down into the action cavity in the photo. Your piano is unusual in that it has three, whereas most grands have one or none (the most I have seen personally in a grand is two). As for the purpose of the horn wedge and horn, it is to allow the wooden belly rail (that large piece of wood above the back action) and the large beams under the piano to assist the plate in containing the tension of the strings. As you surely know, when at pitch, a grand has roughly 20 tons of tension (depending on the model, it could be more or less than that). All of that tension causes the cast iron plate to deform, basically pulling the front of the plate and the tail end of the plate closer together. So, the horn is cast into the plate (protruding from under a strut, most typically at the junction of the bass and tenor struts), and terminates several millimeters from the belly rail, which often has a small cast iron plate or flange at that point. Before stringing, the metal horn wedge us inserted into place between the horn and the belly rail plate, and as the piano is strung and tension is added, that horn tries to move closer to the belly rail, but it can't; instead it squeezes that horn wedge against the belly rail, thus transferring some of the load-bearing duties to the belly rail and large beams under the piano. This is supposed to accomplishes several things, including reducing stress on the plate, stabilizing the entire structure, and promoting tuning stability. As for how well it accomplishes the second and third of these things, I cannot say; some large pianos do not have this feature, yet do fine on all three counts (I am thinking of a Knabe 7'8" grand at the moment). The fact that the plate does deform (compress) under string tension is illustrated with crystal clarity by your experience; as you removed tension, the horn "relaxed" and moved away from the belly rail, allowing the horn wedges to fall out. Save them, and the person doing the restringing will reinsert them before restringing. FYI, they are usually taped into place after insertion, as all of the pounding during the driving of pins can call them to fall out before enough tension has been added to lock them into place. I know that from unfortunate experience.... Joe DeFazio Pittsburgh P.S. - your wippens seem to have a lost motion compensator. I would guess from the pictures that the soft pedal lifts the hammers nearer to the strings (instead of shifting the action), and the extra mechanism takes up the lost motion by expanding the wippen at the wippen heel, allowing the pianist finer control when using the soft pedal. That's what the picture suggests to me, anyway.... > > From: pianolover 88 <pianolover88 at hotmail.com> > Date: August 30, 2009 7:05:18 PM EDT > To: <pianotech at ptg.org> > Subject: Re: [pianotech] Weird Pease Grand > Reply-To: pianotech at ptg.org > > > Yeah it's cast iron not wood. So what is the purpose of these three > metal "inserts"? Since I sublet the stringing out to someone else- > he's the best, and many techs I know use his stringing services-I > guess I will have to alert him to these inserts to make sure that he > puts them in proper place before re-stringing! Just not sure why > they even exist, and why there are "spaces" there to begin with. > Does it make removal of the plate easier? > > Here's pics of the action and whipps. > > Terry Peterson > Accurate Piano Service > UniGeezer.com > "Over 50, and not "2" Tired!" > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20090830/1f8e1b7e/attachment.htm>
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