<!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> <DIV><FONT color=#000080>Comments below:</FONT></DIV> <DIV><FONT color=#000080></FONT> </DIV> <DIV><FONT color=#000080>Terry Farrell</FONT></DIV> <DIV> <SPAN id=__#Ath#SignaturePos__></SPAN> </DIV> <DIV>----- Original Message ----- <DIV>From: "Richard Brekne" <<A href="mailto:Richard.Brekne@grieg.uib.no">Richard.Brekne@grieg.uib.no</= A>></DIV> <DIV>To: <<A = href="mailto:pmc333@earthlink.net">pmc333@earthlink.net</A>>; "Pianotech" <<A href="mailto:pianotech@ptg.org">pianotech@ptg.org</A>></DIV> <DIV>Sent: Friday, April 25, 2003 3:11 AM</DIV> <DIV>Subject: Re: Key Leads and Inertia</DIV></DIV> <DIV><BR></DIV> <DIV>> Paul McCloud wrote:<BR>> <BR>> > John:<BR>> >         I fail to see what = this has to do with real-world dynamics.<BR>> > Since the lead is integral = with the keystick, not suspended by a thread,<BR>> > the inertia is going = to be the same no matter how much acceleration is<BR>> > generated by the = pianist's finger.  What am I missing?<BR>> >         Paul = McCloud<BR>> >         San Diego<BR>> = <BR>> I've wondered about this two, scratching my head a bit. But taking = things at<BR>> face value I do have a couple questions if somebody has the = answers handy.<BR>> <BR>> 1. Isnt this question about lead in the key = really about its total mass, and<BR>> if you first were going to conceptually <<de-couple>> the lead mass and<BR>> dangle it on a = string, wouldnt you have to do that for the wood mass as well<BR></DIV> <DIV><FONT color=#000080>Well yes, but...... John is trying to = demonstrate what the <EM>addition</EM> of lead to a key makes. The key with no lead = with have certain inertia characteristics. The key with the lead will have = different inertia characteristics. Comparing the force required to push the key = down slowly (less than the acceleration due to gravity) with no lead and with = the lead will reveal that less finger force is required when you have = lead in the front portion of the key. Comparing no lead and lead when = applying a forte blow (much greater acceleration than that due to gravity), it = will require more force applied to the key with the lead to accelerate the key at the same rate as with no lead. Decoupling the lead in = the diagram is simply to help visualize this = phenomena.</FONT><BR> <BR>> 2. How fast is the approximate fastest we could expect the key to = be<BR>> accelerated by human fingers in the first place ?</DIV> <DIV> </DIV> <DIV><FONT color=#000080>Lift the front of the key up. Drop it. That = is the acceleration due to gravity. A forte blow is many times (est.) the = acceleration rate due to gravity.</FONT><BR> <BR>> 3. Exceeding 980/sec^2 = just means you are not getting any more <<help>> as<BR>> it were = from the force that is gravity. But this isnt the same as saying<BR>> that = doing so somehow creates an increase in resistance to<BR>> acceleration....yes = ?? Its not like gravity has a kind of reverse gear<BR>> affect here.</DIV> <DIV> </DIV> <DIV><FONT color=#000080>No, gravity does not change, = it is an acceleration force that is consistent. The pianist is the one = that is applying an additional acceleration force. If the finger force is less = than that of gravity, adding lead to the key will decrease the amount of = force required to push the key down at some acceleration rate less = than that of gravity. If the finger force is greater than that of gravity, adding = lead to the key will increase the amount of force required to push the key down at some acceleration rate greater than that of gravity.</FONT><BR> <BR>> 4. From your (Johns) diagram about how = to figure Inertia I have a question<BR>> that goes along the same lines. = Seems like it would be better to measure<BR>> points independant of lead = placement, and rather symetrical accross the<BR>> front half of the key... or = what ?</DIV> <DIV> </DIV> <DIV><FONT color=#000080>Perhaps I missed something (did I?). Did = someone post regarding calculating inertia? Could you repost? (Please!)? </FONT><BR> <BR>> Cheers<BR>> RicB<BR>> <BR>> = --<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>&= gt; <A href="http://home.broadpark.no/~rbrekne/ricmain.html">http://home.broad= park.no/~rbrekne/ricmain.html</A><BR>> <BR>> <BR>> = _______________________________________________<BR>> pianotech list info: <A href="https://www.moypiano.com/resources/#archives">http://www.ptg.org= /mailman/listinfo/pianotech</A></DIV></BODY></HTML>