<HTML style="FONT-SIZE: x-small; FONT-FAMILY: MS Sans Serif"><HEAD> <META http-equiv=Content-Type content="text/html; charset=iso-8859-1"> <META content="MSHTML 6.00.2900.2668" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#d8d0c8> <DIV> <DIV>I've seen several uprights with curved bc's, I know they were not Kimballs, either, or at least not all. They seem to work fine. The mechanism of checking is quite different in uprights vs. grands, of course, even though the parts look similar. Grands depend on intersecting arcs from two different pivotal centers, while uprights (I know y'all will correct me if I haven't got this just right) depend on the position of the checked whippen assembly and a slight "cocking" or "back springing" of the backcheck wire to hold the whole works in check until the whippen drops. Neither system depends all that much on friction between the backcheck and the catcher (or grand hammer tail). You need enough to prevent excessive movement while the action sort of locks in check, but it is not friction, per se, that keeps the parts from uncoupling, i.e., going out of check.</DIV> <DIV> </DIV> <DIV> <DIV>Alan Barnard</DIV> <DIV>Salem, Missouri</DIV> <DIV> </DIV></DIV></DIV> <DIV> </DIV> <BLOCKQUOTE style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid"> <DIV style="FONT: 10pt Arial">----- Original Message ----- </DIV> <DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B> <A title=741662027@theshusters.org href="mailto:741662027@theshusters.org">Cy Shuster</A> </DIV> <DIV style="FONT: 10pt arial"><B>To: </B><A title=pianotech@ptg.org href="mailto:pianotech@ptg.org">Pianotech</A></DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> 07/01/2005 11:33:32 AM </DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Kimball: curved backchecks, regulation specs</DIV> <DIV><BR></DIV><FONT size=2> <DIV><FONT size=2>I took these pictures to share a while back.  I'm pretty sure this is a Kimball.  It couldn't cost that much to staple in a regulation spec card in every piano, could it?  (I suppose it could -- and chances for error, too.).  But this is the first time I've seen curved backchecks.  I wonder what the cost/benefits of that design are?  At first glance, it seems like it might be more sensitive to misalignment than straight surfaces (bent in too far, and only the top edge will catch?).</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>--Cy Shuster--</FONT></DIV> <DIV><FONT size=2>Bluefield, WV</FONT></DIV> <DIV> </DIV></FONT></BLOCKQUOTE></BODY></HTML>