<!doctype html public "-//W3C//DTD W3 HTML//EN"> <html><head><style type="text/css"></style><title>The Richard Gertz myth</title></head><body> <div>All,</div> <div><br></div> <div>Back in 1900, if the patents-office examiner had been paying attention, Richard Gertz never would have got his patent. The sound board of a real world piano does not push outward as downbearing is applied. While the sound board shown in the piano diagram at Mason and Hamlin's website (<font face="Arial">http://www.masonhamlin.com/crown/crown.html)</font> might push outwards, real pianos do not have the sound board ribs offset higher than the cord-line as shown in their image (a jpeg conversion of the M&H website image is shown below). Notice that the M&H drawing shows both the ribs and sound board panel above the line in this exaggerated drawing. In reality the ribs are way below the line.</div> <div><br></div> <div align="center"><img src="cid:a06110401bda700c18668@[10.0.0.22].1.0"></div> <div align="center">jpeg image converted from gif at -<font face="Arial"> http://www.masonhamlin.com/crown/crown.html</font></div> <div align="center"><br></div> <div align="center"><br></div> <div>When Ron Nossaman was here in July, he mentioned that sound boards pull in when the down bearing pressure is applied.  While a crowned sound board, if it had no ribs, would push out, the ribs are much further below the cord-line than the sound board panel is above it. So the net result is that the sound board will PULL IN.</div> <div><br></div> <div>Yesterday I proved this to my satisfaction. I built and load tested a model of rib 6 (numbered from the back) for a Steinway D, attached to a 142 wide strip of 8mm thick Sitka spruce panel. This rib is 990 mm long overall (65 mm shorter than standard on account of the sound board cut-off), with an inner rim contact of 40 mm on the treble-bent side, and 30 mm on the new sound board cut-off. At 0.75 degrees of downbearing angle (a typical figure over this rib on a D), there will be 10.6 Kg down bearing from the treble bridge and 6.4 Kg from the bass. When we applied this load to the sound board test strip, with one end of the strip clamped to the bench and the other end free, it caused the free end to pull in 0.05 mm (2 thou).</div> <div><br></div> <div>So yes, a substantial back beam configuration is a good thing, but the Richard Gertz 'crown retention system' will be of virtually zero assistance.</div> <div><br></div> <div>Ron O.</div> <div><br></div> <div><font color="#0000FF">PS. Some of you may be asking, 'is he still building that Steinway D board'? The answer is yes. We completed the 'new sound board' job a couple of weeks ago. However, I didn't like to tone it produced, so we removed the sound board again last week to redo it. The re-configured panel is assembled and tapered and I expect to have the I-rbs together by the end of today. I will discuss the whys and wherefores about this project once I get the piano up and running.</font></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:info@overspianos.com.au<br> _______________________</font></div> </body> </html>