<!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>Yes!  And isn't this = "sluggishness" the "MOI" we've been talking about????</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>I know the image of the kids on the teeter-totter.  In fact, I've often used the image of elephants on = the teeter-totter!</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>And I suppose in a blindfold test, I = could tell by pushing if the teeter-totter was empty, or had the elephants in place.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>But here we have been discussing the = merits of placing two leads at the front of the key, or four at the = back.  In principle this makes plenty sense, but in practice , we aren't = dealing with anything like the degree of difference between the empty teeter-totter = and the one with the kids or elephants.  We are dealing with very slight differences of key lead placement in piano actions, where most of the "sluggishness" we feel comes from the hammers.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>"Sluggishness" is a powerful sounding = word, but in a situation close to the zero friction, zero gravity experiment, do you = think you could distinguish between the key with two leads at the front and = the key with four at the back (located to produce identical frontweights) by = pressing the key with your finger to produce different hammer = velocities?</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>Ed Sutton</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=eromlignod@kc.rr.com = href="mailto:eromlignod@kc.rr.com">Don A. Gilmore</A> </DIV> <DIV style="FONT: 10pt arial"><B>To:</B> <A title=caut@ptg.org href="mailto:caut@ptg.org">College and University Technicians</A> = </DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> Monday, January 05, 2004 = 9:42 PM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Re: What does the moi = feel like?</DIV> <DIV><BR></DIV> <DIV><FONT face=Arial size=2>Hi Ed:</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>All that would be left is the = "sluggishness" of the parts,<EM> i.e</EM>. the tendency of the key not to want to move and not to want to <EM>stop</EM> moving.  The force required = would be proportional to how quickly you try to change the speed of the = key.  Incidentally, if you totally balance out the weight of the hammer, the = key won't come back up to its starting position.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>Think about an ordinary playground teeter-totter.  With no one in either seat, it is easy to move it = around and it stays where you put it.  Now put a fat kid on either end = (both the same weight).  It's still balanced and stays where you put it, = but it is much more difficult to start and stop it.  The fatter the kids, = the more moment of inertia the system has.  To start one kid upward = quickly takes a big heave.  Then if you want to stop him it is also difficult; = in fact, he may actually lift you off the ground if he has enough energy at = that point.  The feel would not be the same at all for an empty teeter-totter.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>Note that since the system is = balanced, any disturbing force can tip the teeter-totter, no matter how small = (neglecting friction).  I can drop a small brick in one kids lap and = start the lever turning and it will accelerate faster and faster until he = strikes the ground.  The key concept to realize is that the teeter-totter = will accelerate at a greater rate if I drop the same brick onto it = when it's empty than with two fat kids sitting in it.  If I put two 500-lb. = slabs of concrete in each seat, the brick will accelerate them even less, = though the system is still balanced. </FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>Don A. Gilmore<BR>Mechanical = Engineer<BR>Kansas City</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=ed440@mindspring.com = href="mailto:ed440@mindspring.com">Ed Sutton</A> </DIV> <DIV style="FONT: 10pt arial"><B>To:</B> <A title=caut@ptg.org href="mailto:caut@ptg.org">College and University Technicians</A> = </DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> Monday, January 05, = 2004 5:51 PM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> What does the moi = feel like?</DIV> <DIV><FONT face=Arial size=2></FONT><BR></DIV> <DIV><FONT face=Arial size=2>Dear Physicists of the = List-</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>Please comment on this = thought:</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>When I press the piano key, the = resistance to movement I feel consists of three elements</FONT></DIV> <DIV><FONT face=Arial size=2>1) Friction</FONT></DIV> <DIV><FONT face=Arial size=2>2) The pull of gravity on the = hammer and wippen, partly counterbalanced by the pull of gravity on the keyfront.</FONT></DIV> <DIV><FONT face=Arial size=2>3) The combined MOI's of the = various moving parts.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>Therefore, if I can </FONT></DIV> <DIV><FONT face=Arial size=2>1) reduce the friction to zero, and = </FONT></DIV> <DIV><FONT face=Arial size=2>2) use a wippen assist spring to = produce a balance weight of zero, the only resistance left would be = </FONT></DIV> <DIV><FONT face=Arial size=2>3) the combined MOI's of the key, = wippen and hammer.  </FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>What I would feel then, in various = key strokes, would be whatever it is we are talking about. </FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>Could I make or buy a gauge to = measure this?</FONT> </DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>Does this line of thought seem = useful in understanding the situation?</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>For example, has anyone felt a key = such as I describe?</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>Ed Sutton</FONT></DIV></BLOCKQUOTE></BLOCKQUOTE></BODY></HTML>