<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; = charset=iso-8859-1"> <META content="MSHTML 5.50.4134.600" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#ffffff> <DIV> Dale, Carl, et al, As I understand it, the = vertical hitchpin arrangement was developed as a manufacturing expediency. It enables the manufacture of the bridge assembly—including drilling, notching = and pinning—prior to anything being fitted to the piano. The finished = bridge is simply glued to the soundboard and the whole assembly is then glued into = the piano. The plate elevation is set to the bridge using the threaded bolt = system concurrently developed with the hitchpin system. String bearing, i.e., soundboard loading, is then established by the vertical alignment of the = strings on the vertical hitch. The vertical hitchpin system by itself has = nothing to do how much string bearing, or soundboard loading, is required or is = present. It simply provides a method of adjusting that load after the piano is = strung. The purpose of string = “downbearing” is to place load on the crowned soundboard assembly and deflect it from its as-installed condition. Considering the soundboard assembly as a large, irregularly shaped disc spring, this load provides the piano builder = with a means of increasing its stiffness without increasing its mass. How much = string bearing, i.e., string downforce against the bridge, any individual = soundboard assembly must have for best performance is a function of the soundboard = design and, to some extent, such factors as the design and shape of the rim, = the relative tensions of the string scale, the length of the string = backscale, etc. Mostly, how much loading any = specific soundboard must have is a function of how massive and how stiff the = soundboard assembly is. This is not a universal constant. Dale’s string = deflection numbers would not work all for one of our boards. As to whether they would work = for one of Baldwin’s current boards—I can’t say. With the = Accu-Just system Baldwin has used a fairly light crown radius—72’ (about 22 m) if I = recall correctly—machined into the ribs. I believe the rib-to-soundboard press cauls are crowned = the same. I don’t recall the MC of the board at the time of ribbing, but I = don’t recall it being overly dry. Excessive loading—and it doesn’t take much = to be excessive—on one of these boards will overload it, hence the relatively shallow = string deflection angles and the traditionally percussive, short sustain, = sound. (And I think that’s 0.5%, 1.0% and 1.5% downforce as a funciton of = string tension as indicated by 1, 2 or 3 lines of gradation each indicating 17 minutes of arc on the Baldwin bubble gage, not 0.5°, = 1.0° and 1.5° of string deflection). Personally, I would load them just a bit more = than the Baldwin specification calls for always being aware of the relatively = shallow initial crown specification. If you’re replacing a = soundboard in a Baldwin—or if you have converted some other piano to the vertical = hitch pin system—and you’re using your own standard soundboard = design—I would recommend that you use the string deflection angles you’re already = accustomed to. As Ron has indicated, you want to end up with the string about 4 to 5 mm off = the plate surface. You have a bit more leeway with this on a Baldwin plate = designed to accomodate the vertical hitch; the hitchpin panel has been made some = thicker to accommodate the additional torsional stress of the string riding higher = on the pin. Be very careful with other pianos and other plates. Of course, string bearing can = be measured and altered after it has been set. That is one of the inherent = advantages of the system. Why that statement would appear in the Baldwin instruction sheet = baffles me. What you will find, though, is that once you have established some = amount of string deflection—how much varies with the soundboard design and = string backscale length—tapping the strings down further won’t give = you much more measurable string deflection. Except at the extreme end of the tenor = bridge and, sometimes, at the low end of the bass bridge, the soundboard will just = continue to deflect as you tap the strings down. Yes, I know, there should be = some noticeable change in the string deflection angle, but there won’t = be. At least none that will be readily measurable. Try it and see. Perhaps Baldwin took that = approach to keep technicians from continuing to tap strings down until they had = achieved a condition of permanent reverse crown. If so, it didn’t work since = that is an all-to-common problem with the system. I’ve fielded questions from = technicians who considered it a matter of poor workmanship to have the strings = riding up on the hitch and tapped them fully down against the plate surface. Ruining = the soundboard and any semblance of tone quality in the process, of course, = but at least the strings were now ‘properly’ seated. This is an excellent string = termination system, the benefits of which extend well beyond manufacturing = expediency. I have an idea if it was understood some better it would also be used more = frequently. Del Delwin D = Fandrich Piano Designer & Builder Hoquiam, Washington  USA E.mail:  = <A href="mailto:pianobuilders@olynet.com">pianobuilders@olynet.com</A> = Web Site:  <A href="http://www.pianobuilders.com">www.pianobuilders.com</A></P= ></DIV></BODY></HTML>