<!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 6.00.2600.0" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#ffffff> <DIV><FONT face=Arial size=2>David, hysteresis in electronics is = sometimes referred to as dead band.  It may be desirable in certain applications.  An air compressor that turns off at 120 psi and then = turns on again at 90 psi has 30 lbs. of hysteresis.  If it had no = hysteresis then it would never know what to do.  Some is necessary.  Your = thermostat is another good example of a device with lots of hysteresis.  I = would say that even a single leaf spring would have a bit of hysteresis due to the = small amount of friction at the contact.  A coil spring should have = minimal hysteresis unless there were some friction present.</FONT></DIV> <DIV> </DIV> <DIV><FONT face=Arial size=2>A feedback servo system whether = electronic mechanical or hydraulic needs at least some hysteresis because without = it they would be prone to become unstable and oscillate.  The dead band is = the amount of error required to cause a correction from the = system.  Weird, huh??</FONT></DIV> <DIV> </DIV> <DIV><FONT face=Arial size=2>Carl Meyer  Assoc. PTG<BR>Santa = Clara, California<BR><A href="mailto:cmpiano@attbi.com">cmpiano@attbi.com</A> = </FONT> </DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><B>From:</B> <A title=davidlovepianos@earthlink.net href="mailto:davidlovepianos@earthlink.net">David Love</A> </DIV> <BLOCKQUOTE dir=ltr style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; = BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px"> <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, February 10, 2002 = 8:19 PM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Hysteresis: was = Soundboard springs ...</DIV> <DIV><BR></DIV> <DIV><FONT size=2>Sorry Del, it was Ron Overs actually.  I'm = still not sure what hysteresis is exactly and why a leaf spring might have a = problem compared to a coil spring?  Ron, if you're = listening?</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>David Love</FONT></DIV> <BLOCKQUOTE dir=ltr 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=pianobuilders@olynet.com href="mailto:pianobuilders@olynet.com">Delwin D Fandrich</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> February 10, 2002 7:27 = PM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Re: Soundboard = springs and hysterisis: question for Del F.</DIV> <DIV><BR></DIV> <BLOCKQUOTE dir=ltr style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; = BORDER-LEFT: #000080 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=davidlovepianos@earthlink.net href="mailto:davidlovepianos@earthlink.net">David Love</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> February 10, 2002 = 11:14 AM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Soundboard springs = and hysterisis: question for Del F.</DIV> <DIV><BR></DIV> <DIV><FONT size=2>Del:</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>Been reading the past posts on soundboard = springs and have come to your comments that a leaf spring arrangement would be = subject to "hysterisis" and would not be as effective.  Could you = define what you mean by that term as it applies here?</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>Thanks</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>David love</FONT></DIV></BLOCKQUOTE> <DIV dir=ltr><FONT size=2></FONT> </DIV> <DIV dir=ltr><FONT size=2> <DIV><FONT color=#000080>Did I say that? Surely not. </FONT></DIV> <DIV><FONT color=#000080></FONT> </DIV> <DIV><FONT color=#000080>Hysteresis would only be a problem if = leaf springs of multiple layers were used. Then the breakaway friction between = the various leaves might cause a response problem. (Bearing in mind that = I've not actually tried this.) Otherwise, with a single leaf, I = don't see the problem. And I can't think of any reason to use a multiple leaf = spring arrangement for this application. Using a single leaf spring it = should be relatively easy to figure out a virtually frictionless coupling = between a leaf spring and the soundboard. Assuming, of course, that one really = wanted to use a leaf spring.</FONT></DIV> <DIV><FONT color=#000080></FONT> </DIV> <DIV><FONT color=#000080>Del</FONT></DIV></FONT></DIV></BLOCKQUOTE></BLOCKQUOTE></= BODY></HTML>