<!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 6.00.2800.1106" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#ffffff> <DIV>Ric,</DIV> <DIV> </DIV> <DIV><FONT face=Arial size=2>A conceptual tool that helps us = visualize this problem is the "free body diagram".  Draw a hammer and shank, then = draw an arrow for each force acting on the hammer:  gravity, jack, rep. = lever, center pin, string.  period.  Between let-off and impact, the = jack, rep lever, and string are not in contact with the knuckle.  = The list of forces acting on the hammer/shank assembly consists = of gravity and center pin.  period.  Both are acting to decelerate the hammer.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>keystroke before let-off, and rebound = after impact, are more complicated because there are more forces involved, and they = are not all acting in the same direction, but the method would be the = same.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>hope this helps,</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>Mike Spalding RPT</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2></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=Richard.Brekne@grieg.uib.no href="mailto:Richard.Brekne@grieg.uib.no">Richard Brekne</A> </DIV> <DIV style="FONT: 10pt arial"><B>To:</B> <A = title=kevin.e.ramsey@cox.net href="mailto:kevin.e.ramsey@cox.net">Kevin E. Ramsey</A> ; <A title=pianotech@ptg.org = href="mailto:pianotech@ptg.org">Pianotech</A> </DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> Sunday, April 27, 2003 = 5:25 AM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Re: hammer = velocity</DIV> <DIV><BR></DIV>  <P>"Kevin E. Ramsey" wrote: <BLOCKQUOTE TYPE="CITE"><FONT face=Arial><FONT size=-1>Richard Brekne</FONT></FONT><FONT face=Arial><FONT size=-1>I believe = there is a letoff position (just under 1mm) that is so close that the hammer = does not have a chance to start de-acceleration. I havent gotten into all = this side of things very much yet, so I am not sure of myself here, but isnt = there some sort of "left over" force that keeps an object in acceleration = for some small period of time even tho the origional applied force is removed = ?  Like a bullet coming out of a rifle ?? Doesnt that meet its maximum acceleration some few milliseconds after the explosion of the shell ?</FONT></FONT> <FONT face=Arial><FONT size=-1>RicB</FONT></FONT> <FONT face=Arial><FONT size=-1>    No, Richard, no "left over" force is = there to continue accelerating an object after it's direct influence is = removed. If you really want to know what happens inside a rifle, feel free to = write me privately. No, the bullet doesn't continue accelerating after = leaving the barrel.  The only thing that I think could possibly continue accelerating a hammer after the jack has tripped would perhaps be = the flex of the shank becoming straight again, but at 1 mm, I'm not sure that = it could be measured without high-speed cameras to capture the action.</FONT></FONT><FONT face=Arial><FONT = size=-1>    In reality, the pianist has the skill to adapt to the instrument, and = still make music.  All we can do is to provide them with the best = regulated and voiced instrument we can, and they can take it from there, if = they are truely "musicians".</FONT></FONT><FONT face=Arial><FONT size=-1>Kevin.</FONT></FONT></BLOCKQUOTE> <P><BR>Well like I say guys... I havent brushed up my inertia physics = in a long time :) Another fellow (who knows I like Star Trek series) wrote = privatly to me as asked me if I'd ever seen the episode where the Enterprise = does a saucer seperation... and he aske me "now is the saucer accelerating = away from the ship, or is the ship just slowing down faster"... I kinda got the = point :) <P>Still, there does seem to be some pent up force in the entire = system that is throwing the hammer upwards. Key and shank flex are two that get = mentioned a bit in this connection. Seems to me that all this is the direct = result of the amount of force put on the keyfront. Just where and how this pent = up energy gets released I am unsure of. Within the space of 1mm  of = key travel perhaps ? <P>btw... the rifle thing... I dont think I mentioned anything about = after leaving the barrel... did I ? I think I said quite clearly after the = initial explosion. <P>Cheers <P>-- <BR>Richard Brekne <BR>RPT, N.P.T.F. <BR>UiB, Bergen, Norway = <BR><A href="mailto:rbrekne@broadpark.no">mailto:rbrekne@broadpark.no</A> = <BR><A = href="http://home.broadpark.no/~rbrekne/ricmain.html">http://home.broad= park.no/~rbrekne/ricmain.html</A> <BR>  </P></BLOCKQUOTE></BODY></HTML>