Hello David, I would suggest that it is a good idea to shim this gap in the flange/block fit whether the piano is brought up to pitch or not and whether or not the gap contributes to the crack you describe in the plate. In my opinion the crack that occurs next to the strut in the tenor is a good indication of the ability of the hole for the screw to be a stress raiser. I have seen several of these cracks on 88 note B's and none, although perhaps some contributor here will report otherwise, on the 85 note B's. The difference between the two pianos is that the hole for the screw on the 85 note piano, that is, the original design, was about two and half inches or so from the plate strut.. The stress raising effect of this hole was then distributed into a region of lesser stress keeping it below the critical level of forming a crack. When the piano was enlarged, apparently without consideration of the effect of this hole as a stress raiser, it was moved much closer to the strut which then placed it into a region of, apparently, higher and more complicated stress, resulting in a propensity to crack if other factors militated in such a direction. Interestingly, I have seen this on pianos from as far back as the turn of the 19th century and as recently as B's produced in the late 80's. You would think, in a hundred years, the factory would have detected this and corrected it. All but one of these cracks that I have seen over the years come out of the screw hole and proceed roughly parallel to and close in in a slightly angled fashion to the strut. These kinds of cracks seem to have very little effect on the stability of the piano and I have two that I see from time to time that are at pitch. There is another kind of crack, much more dangerous, which I have only seen once and not on a B, which proceeds along the plate parallel to the stretcher for four, five or even six or seven inches. The only one I have ever seen was, I think, on an M. I have had one decribed to me recently which was on a B and was informed that the piano was 'extremely unstable" by a very reliable tuner, as was the M. These kinds of cracks I would take an entirely different approach to and not raise the pitch were it low. I would suggest that a possible source of these cracks, at least as they occur on B's, and probably the other models to a point, arises in the complexities of the stress distribution created by the interaction of the horn wedge and the detachable strut on the plate with a possible complication arising from poor fitting of the top of the block to the plate webbing and the stress raising effect of the screw hole along with its placement too close to the strut. Obviously complexities attaching to the removable strut should be discounted in the models without one. The fitting of the block to the flange, except as an indicator of general sloppiness, is probably secondary. This interaction may also account, although this is somewhat speculative, for the orientation of the crack whether parallel to the stretcher or parallel to the strut. All of the pianos that I am aware of with these problems have been restrung: I suspect that subsequent installation of the wedge and strut may have contributed to these problems by increasing stress in the region adjacent to the strut. In my opinion, although anyone with any experience in removing Steinway plates is readily aware that they may be flexed down somewhat during installation at the factory, it is more important to set the plate properly with a minimum of flexing on B's. Even if flexed slightly though as one frequently encounters, which may be actually innocuous, it is very important, in my opinion to install the wedge under the horn before stringing, securing it so that it neither forces the plate to be bowed back toward the stretcher or allows it to flex forward to close a small gap between wedge and horn. Then the removable strut can be reinstalled and should be ground or shimmed to function similarly to the wedge; that is to allow no motion. Waiting until after stringing is completed is highly problematic as a technique in my opinion, although the piano may be long gone before such a problem becomes evident in the form of a crack. Both the strut and the wedge are functionally, similar to nosebolts as they should merely restrain the plate, or motion in it, and not force it somewhere. Although I know sometimes the removable strut may even be removed when the piano is strung and up to pitch, even stringing the piano and leaving the wire slack may bring enough strain into the system to render inadvisable installing the wedge after stringing. The complications of the two when installed otherwise, may, along with the stress raising effect of moving the hole closer to the strut allow the strain to exceed the yield point and, over time, allow stress relief to manifest itself in the form of a crack. Finally, I would guess, although again I have nothing but incidental observation to back this up, that the orientation of the crack itself suggests some things about the interaction of the two as contributors to these cracks. These are mere speculations but it maybe that where the crack is parallel to the strut, as most I have seen are, a reasonable suspicion can attach to the installation of the strut: either independently or in conjunction with the wedge, it may be actually forcing the horn back and to the left resulting in a crack emanating from the screw hole and proceeding parallel to the strut. Where the crack is parallel to the stretcher perhaps the wedge has been installed either too tightly prior to or subsequent to stringing causing the horn to be rotated upwards and towards the stretcher with the result of stress relief now appearing as a crack proceeding parallel to the stretcher and somewhere in the neighborhood of the flange. A third possibility is that the wedge is either installed too tightly and too much to the right - again creating a tendency for the horn or rotate, increasing stress in the vulnerable region and forcing, again, a crack. There are, no doubt, combinations of these effects. In general, I think all of it is more likely to be avoided when the procedure I have outlined above is followed. Regards, Robin Hufford David Skolnik wrote: > Dear List - > I have a beautiful Rosewood B which sounds great, but has the classic crack > in the plate, emanating from one of the plate / Pinblock screws, right at > the treble side of the tenor brreak, ie. just before the bass. The > probable cause was the poor fitting of the replaced block. A gap of at > least 1/32" is detectable between the block and flange, running for about 8 > or 9 inches. > The question: If the customer determines he wishes to take the risk in > pulling the pitch (eventually) to 440, and is aware that he might, > ultimately need to replace the plate. Is it advisable to, first, drop pitch > and shim the gap? I'm having trouble visualizing how the crack alters the > stress patterns on the plate in that area. > > Many thanks. > > David Skolnik > > _______________________________________________ > pianotech list info: https://www.moypiano.com/resources/#archives
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