<!doctype html public "-//W3C//DTD W3 HTML//EN"> <html><head><style type="text/css"></style><title>Re: Plate Horn</title></head><body> <div>Hi Avery,</div> <div><br></div> <blockquote type="cite" cite>A question for you rebuilder types:<br> <br> I guess basically it's what is the procedure, when restringing, to ensure the plate<br> horn is snug? Here's what happened:<br> <br> My apprentice had restrung the plain wire section of a Yamaha G3. To save a little<br> time, I'd pulled up the middle strings for him with my SAT before he arrived (whole<br> step flat) and then he was in the process of pulling in the outside strings.<br> <br> I happened to be standing on the bass side and noticed a piece of gold-painted metal<br> lying on the keybed. A little quick looking and we discovered it was a wedge between<br> the horn and the belly (is that what that area's called?). Well, it wouldn't go in<br> but just a little, so I had him start lowering tension, starting at the bottom of the<br> tenor section. After several notes, the wedge fell out, so I knocked it up again as<br> far as it would go. Had to remove the sostenuto rod to give some "banging" clearance.<br> Then, same procedure done again and once more the wedge fell out. We continued this<br> until the wedge was almost all the way in. Finally, it went all the way up to where<br> it'd been originally. Plate screws had been tightened, BTW. I'm assuming everything is<br> OK now. No plate cracks, etc. :-)<br> <br> I've never had this happen before and am wondering why it did. Obviously, the plate moved/flexed a little for this to have happened. I'd never seen a wedge like this<br> before, so didn't think to check it. I don't know exactly when it fell out: while<br> unstringing, pounding in the pins when restringing, while pulling up the pitch?<br> <br> Any ideas on what I should have done to prevent this from happening?</blockquote> <div><br></div> <div>There is always a risk of a horn wedge falling out when the pins are pounded in when re-stringing.</div> <div><br></div> <div>The horn has become a rather standard item in contemporary grand piano design. Not all grands have a plate horn, eg. KG series Kawai and Bösendorfer grands. However, I believe the horn is a useful way of the improving the structural rigidity of the case/plate assembly. It can slightly improve tuning stability, and may also help the sustaining qualities of an instrument (although the sound board design is by far the most important factor for sustain). While most plates will be capable of withstanding the string tension at pitch, even when the wedge has either been left out or has fallen out during re-stringing, there may be a small risk of some of the lighter plates sustaining damage.</div> <div><br></div> <div>As a general practice, it is a good idea to use tape to hold the wedge in place until sufficient string tension has been applied to hold it. When the wedge is missing and string tension has been applied, it isn't necessary to completely release all string tension before driving the wedge home. Just the minimum tension release required to drive the wedge home will be OK. The plate and pinblock does flex down under tension if the wedge isn't in place, but the flexure will reverse once the wedge is replaced.</div> <div><br></div> <div>I find this design tendency to use just one horn, positioning it at the bass/treble break, along with most if not all of the longitudinal back beams, which also meet at what some magically (and fictitiously) call the 'Tone collector', to be quite a strange design practice/custom. After all, when one considers the belly of a grand piano and the characteristics that we should be aiming for, it is the treble areas where we require the greatest stiffness and rigidity of design, not down in the tenor area. So the traditional placement of the plate to belly bracing might be better placed at the next higher string section break.</div> <div><br></div> <div>With our current Overs 225 piano, it has a traditional cast horn at the bass/treble break. But we also fit additional braces (2) to the top two treble string section breaks. For the Kawi KG5 piano we recently remanufactured and re-named Overs - Kawai, we fitted two additional struts, one at the bass/treble break (since there was no horn in the original design) and one at the next higher break (where the capo section starts). An image of the higher strut can be found at;</div> <div><br></div> <div><font face="Lucida Grande" size="-3" color="#000000" >http://members.optusnet.com.au/ronovers/overskawai6.jpg</font></div> <div><br></div> <div>The diameter of the strut is 0.5" (12.7 mm), and the custom-made threaded fitting has a 1/2" thread with 70 mm of thread length in the belly rail. A hardwood block is glued in behind the belly rail sound board support strip, before the sound board is fitted, to provide sufficient wood depth for the 70 mm of thread to be fully engaged with the belly.</div> <div><br></div> <div>I'm a big fan of these plate to belly rail struts. This latest version is quick to make and I think they really help to stiffen the plate against downward flexure at the pin-block area when its subjected to string tension. They must be helping to keep the entire piano stable. We've found that pianos fitted with these struts seem to exhibit improved tuning stability.</div> <div><br></div> <blockquote type="cite" cite> Any other comments,</blockquote> <div><br></div> <div>We've all been there Avery. You are not alone.</div> <div><br></div> <div>Best,</div> <div>Ron O.</div> <x-sigsep><pre>-- </pre></x-sigsep> <div><font face="Times New Roman" size="+1" color="#0000FF"><b>OVERS PIANOS - SYDNEY</b></font></div> <div><font color="#000000"><i>   </i></font><font color="#0000FF"><i>Grand Piano Manufacturers</i></font><font color="#000000"><br> _______________________</font></div> <div><font size="-2" color="#000000"><br> </font><font color="#000000">Web http://overspianos.com.au</font></div> <div><font color="#000000">mailto:ron@overspianos.com.au<br> _______________________</font></div> </body> </html>