<div>The ribs are shorter in the 20% of bridge length and the frequencies are much higher. </div> <div> </div> <div>I don't think of it as downbearing pressure but contact or coupling pressure. The bridge is actually pushing up so we could call it up bearing or down-bearing resistance. Coupling pressure should be around 2# to 4# per string. You have some leeway but too much coupling pressure cuts into the bridge and too little loses sound production. Yes the unisons spread out but the overall load should be less on the longer ribs and you can't change the coupling pressure that much anyway. </div> <div> </div> <div>I just did all the rib shaping and board diaphraming and cut off bar in and S&S A at Dale Erwins shop. He finished it up and it's glued in and it's time to hear it. Next time I'll be there to set the bearing, hopefully. </div> <div> </div> <div>Keith Roberts</div> <div> </div> <div><br><br> </div> <div><span class="gmail_quote">On 4/28/07, <b class="gmail_sendername">Bob Hohf</b> <<a href="mailto:rhohf@centurytel.net">rhohf@centurytel.net</a>> wrote:</span> <blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid"> <div lang="EN-US" bgcolor="white" vlink="purple" link="blue"> <div> <p><font face="Arial" color="navy" size="2"><span style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Why would you ever want to set the same downbearing force per unison when the unisons are so unevenly distributed along the length of the bridges?  The top two sections of a typical concert grand contain 43% of the strings on 20% of the total bridge length.  A smaller piano may have 46% of the strings on 29% of the bridge.  Setting a uniform downbearing per string will set up a tone-stifling imbalance in the downbearing force along the bridges.  For 20+ years I have been setting downbearing on the principle of uniform force per unit of bridge length.  This produces much less force per string in the high treble and much more in the tenor.  I don't measure angles.  In Parts 5 & 6 of "Recapping Bridges" in the 1999 Journal, I present a discussion of downbearing as force, not dimension, and describe a method of setting a more uniform load distribution.  I'm sorry it's too involved to go into detail here.  I know of one other rebuilder besides me who does something along these lines. </span></font></p> <p><font face="Arial" color="navy" size="2"><span style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"> </span></font></p> <p><font face="Arial" color="navy" size="2"><span style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Bob Hohf</span></font></p> <p><font face="Arial" color="navy" size="2"><span style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"> </span></font></p> <p><font face="Arial" color="navy" size="2"><span style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"> </span></font></p> <p><font face="Arial" color="navy" size="2"><span style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"> </span></font></p> <div> <div style="TEXT-ALIGN: center" align="center"><font face="Times New Roman" color="black" size="3"><span style="FONT-SIZE: 12pt; COLOR: windowtext"> <hr align="center" width="100%" size="2"> </span></font></div> <p><b><font face="Tahoma" color="black" size="2"><span style="FONT-WEIGHT: bold; FONT-SIZE: 10pt; COLOR: windowtext; FONT-FAMILY: Tahoma">From:</span></font></b><font face="Tahoma" color="black" size="2"><span style="FONT-SIZE: 10pt; COLOR: windowtext; FONT-FAMILY: Tahoma"> <a onclick="return top.js.OpenExtLink(window,event,this)" href="mailto:caut-bounces@ptg.org" target="_blank">caut-bounces@ptg.org</a> [mailto:<a onclick="return top.js.OpenExtLink(window,event,this)" href="mailto:caut-bounces@ptg.org" target="_blank"> caut-bounces@ptg.org</a>] <b><span style="FONT-WEIGHT: bold">On Behalf Of </span></b>RicB<br><b><span style="FONT-WEIGHT: bold">Sent:</span></b> Saturday, April 28, 2007 3:04 AM<br><b><span style="FONT-WEIGHT: bold">To:</span> </b> <a onclick="return top.js.OpenExtLink(window,event,this)" href="mailto:caut@ptg.org" target="_blank">caut@ptg.org</a><br><b><span style="FONT-WEIGHT: bold">Subject:</span></b> [CAUT] Wire Stretch</span></font><font color="black"> <span style="COLOR: windowtext"></span></font></p></div> <p><font face="Times New Roman" color="black" size="3"><span style="FONT-SIZE: 12pt"> </span></font></p> <p><font face="Times New Roman" color="black" size="3"><span style="FONT-SIZE: 12pt">Yes they do what Bob ?  Graduate downbearing angles so as to get exactly the same amount of downbearing force on each unison ?<br><br>RicB </span></font></p> <p><font face="Times New Roman" color="black" size="3"><span style="FONT-SIZE: 12pt">>Course the problem with this notion is that equal tension by no means <br>(in fact dictates the opposite) of equal amounts of downbearing pressure <br>across the scale unless one compensates by graduating the downbearing <br>angle appropriatly...which I dont think anyone does.<<br><br><br><br>Yes, they do.  Check out your July and August 1999 Journals<br><br>Bob Hohf </span></font></p></div></div></blockquote></div><br>