<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; = charset=us-ascii"> <META content="MSHTML 5.50.4522.1800" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#ffffff> <DIV>I have always been curious about the soundboard pre-stressing = method of targeting downbearing, but when I ask how much to push the soundboard = down, I get answers like: "enough", "not too much" and the like. The idea = of getting a feel for how much the soundboard will deflect under load I = should think would help target proper downbearing Now I see here we are = using some numbers. This is a good thing. You say David Hughes deflects the board = 3mm at the center strut. You state that you drive wedges under each strut. How = much do you deflect the board at each strut?</DIV> <DIV> </DIV> <DIV>Now the other question I have is that I assume the reason one would = pre-stress the soundboard is to incorporate into your work how much the soundboard will deflect under load. But if you deflect the soundboard = 3mm or whatever, wherever, for any given soundboard, what does that do for you = (i.e., you are pushing a stiff board 3mm down, and you would be pushing a = highly flexible board 3mm down - under strung conditions, obviously the = flexible board would deflect more under final strung downbearing)? You could simply = calculate the needed angles without pre-stressing the board. Now if you could = pre-stress the board with downward pressure approximately equal to that of the final string downbearing in the various regions of the scale, then = we would be truly simulating the soundboard's reaction to the strung-up load and accurately calculate our desired string downbearing angles, etc. Of = course to do this we would need some sort of pressure gauge/device.</DIV> <DIV> </DIV> <DIV>What about a rig similar to a pneumatic rib clamp. Just use the = half with the fire hose. Clamp it to the rim above the bridge, inflate, and there = you go with measurable pressure applied all along the long bridge in much the = same manner as downbearing would be once the piano is strung. You could also = use four segments of fire hose to apply appropriate variable pressure to each of = the four sections (and one on the bass if you want to do that). The result would = be a board stressed in very much the same manner as it would be after = stringing. Then you could set your downbearing exactly where you want it, armed with the = knowledge of exactly (or there abouts) how much the soundboard will = deflect!</DIV> <DIV> </DIV> <DIV>So now, readers..........you are thinking one of two things: Either = Terry Farrell needs to get his head screw on properly, i.e. it's a dumb idea, = or it sounds like a great idea, now go try it Terry and write us back. So what = do you think?</DIV> <DIV> </DIV> <DIV>Maybe it is the case that with a given soundboard construction, the = boards are consistent enough to yield predictable result when pre-stressed 3mm = or whatever. Is this the case, and thus would yield a more accurate = pre-stressing a waste of time?</DIV> <DIV> </DIV> <DIV>I guess I'm just thinking and probing for information. Any input = would be appreciated. I realize the thing to do is put in a couple dozen boards, = try some different methods, and see what happens. But boy oh boy, that will be = years, and I would fear, some tears. I'm just trying to arm myself with as much = info a possible before I screw up too darn many pianos.</DIV> <DIV> </DIV> <DIV>Terry Farrell</DIV> <DIV> <SPAN id=__#Ath#SignaturePos__></SPAN> </DIV> <BLOCKQUOTE style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; = BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px"> <DIV style="FONT: 10pt arial">----- Original Message ----- </DIV> <DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: = black"><B>From:</B> <A title=Erwinspiano@AOL.COM href="mailto:Erwinspiano@AOL.COM">Erwinspiano@AOL.COM</A> </DIV> <DIV style="FONT: 10pt arial"><B>To:</B> <A = title=pianotech@ptg.org href="mailto:pianotech@ptg.org">pianotech@ptg.org</A> </DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> Sunday, January 20, 2002 = 1:07 AM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Re: Baldwin accu-hitch = pins</DIV> <DIV><BR></DIV><FONT face=arial,helvetica><FONT lang=0 = face=Arial size=2 FAMILY="SANSSERIF">In a message dated 1/19/2002 9:15:16 PM Pacific = Standard Time, <A = href="mailto:davidlovepianos@earthlink.net">davidlovepianos@earthlink.n= et</A> writes:<BR><BR><BR> <BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #0000ff 2px = solid; MARGIN-RIGHT: 0px" TYPE="CITE">Subj:<B>Re: Baldwin accu-hitch pins = </B><BR>Date:1/19/2002 9:15:16 PM Pacific Standard Time<BR>From:<A = href="mailto:davidlovepianos@earthlink.net">davidlovepianos@earthlink.n= et</A><BR>Reply-to:<A href="mailto:pianotech@ptg.org">pianotech@ptg.org</A><BR>To:<A href="mailto:pianotech@ptg.org">pianotech@ptg.org</A><BR><I>Sent = from the Internet = </I><BR><BR>         David</FONT><FONT lang=0 style="BACKGROUND-COLOR: #ffffff" = face=Arial color=#000000 size=2 = FAMILY="SANSSERIF"></BLOCKQUOTE><BR><BR></FONT><FONT lang=0 style="BACKGROUND-COLOR: #ffffff" face=Arial = color=#000000 size=2 FAMILY="SANSSERIF">   David Hughes and I both drive wedges = in uder each strut to compress the board along its entire span. We start at = the central strut then first and last capo then bottom strut. Then the = dime quarter nickel business. I use 2.5 mm top treble 2.25mm first treble = an bout 2mmin tenor tapering to 1.5 or so down low on tenor. Bass is set with = about 1/2 degree at the top tapering down to 0 at the bottom.<BR>Pretty much = the same.<BR>   Dale</FONT><FONT lang=0 style="BACKGROUND-COLOR: #ffffff" face=Arial color=#000000 = size=2 FAMILY="SANSSERIF"><BR></FONT><FONT lang=0 = style="BACKGROUND-COLOR: #ffffff" face=Arial color=#000000 size=2 FAMILY="SANSSERIF"><BR> <BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #0000ff 2px = solid; MARGIN-RIGHT: 0px" TYPE="CITE"><BR>Dale:</FONT><FONT lang=0 = style="BACKGROUND-COLOR: #ffffff" face=Arial color=#000000 size=3 = FAMILY="SANSSERIF"><BR><BR></FONT><FONT lang=0 style="BACKGROUND-COLOR: #ffffff" face=Arial = color=#000000 size=2 FAMILY="SANSSERIF">My conversations and classes that I attended = with David Hughes (if I remember correctly) led me to believe that he = prestressed the board under the central plate strut by 3 mm and then set the bearing = dime, nickel, quarter, in low tenor, mid-range, treble, = respectively.  That seemed to pretty much be his method without additional = measurement.  I'm sure he arrived at this method by much experience, but he didn't = seem to sweat it beyond that.</FONT><FONT lang=0 = style="BACKGROUND-COLOR: #ffffff" face=Arial color=#000000 size=3 = FAMILY="SANSSERIF"><BR><BR></FONT><FONT lang=0 style="BACKGROUND-COLOR: #ffffff" face=Arial = color=#000000 size=2 FAMILY="SANSSERIF">David Love</FONT><FONT lang=0 style="BACKGROUND-COLOR: #ffffff" face=Arial color=#000000 = size=3 FAMILY="SANSSERIF"><BR></FONT><FONT lang=0 = style="BACKGROUND-COLOR: #ffffff" face=Arial color=#000000 size=2 FAMILY="SANSSERIF"><BR> <BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #0000ff = 2px solid; MARGIN-RIGHT: 0px" = TYPE="CITE">Dale:<BR><BR></BLOCKQUOTE><BR></BLOCKQUOTE><BR><BR></BLOCKQ= UOTE></FONT></FONT></BODY></HTML>