<!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 6.00.2800.1491" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY text=#000000 bgColor=#ffffff> <DIV><FONT face=Arial size=2>Hey Ric,</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>Cool design! :-)</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>It seems like a lot of mass, though, = particularly on the backside of the keystick.  How much does this gizmo = contribute to the DW of the key?</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>Out of curiosity, have you considered a = felted (or rubber <gasp>) roller for the wippen heel, combined with a = conventional capstan on the keystick?  That would give you the adjustable = capstan height without all the additional mass, and it would still yield relatively frictionless travel.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>Also, with the introduction of a = roller, either on the keystick or on the wippen, do you anticipate "clicky" bearing points = as the action wears?</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>Always interesting to see your innovations!</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>Peace,</FONT></DIV> <DIV><FONT face=Arial size=2>Sarah</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <BLOCKQUOTE 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=ricbrek@broadpark.no = href="mailto:ricbrek@broadpark.no">Ric Brekne</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> Sunday, April 17, 2005 = 5:26 PM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Capstans... which = brings me back to....</DIV> <DIV><BR></DIV>And update on my Magnetic Assist mechanism for the = grand action. The Virtual capstan of a couple years back that btw has = been  up and working just dandily this past year now.  8 hours a day they = are banging away on this instrument..<BR><BR>But too the point.... I have = not been satisfied trying to deal with the standard capstan adjustment when = using the fold down magnet assembly.   So... I've come up with a new = version of the old rocker arm... which I think has many good = points.<BR><BR>Note... The following  amounts to Public Disclosure of an invention. True = to style any one is free to open source develope the concept as they = wish, but no patents can follow unless one devises a clear improvement on the basic = idea.<BR><BR>First a drawing of the rocker arm.<BR><BR><IMG alt="" src="cid:00e701c543d3$3974e610$6b6b8f41@earlinelaptop"><BR><BR>The = assembly features an axled roller (brass) instead of a standard capstan for the = interface with the whippen cushion. It is also axled to the key (red = dot on the half round in the middle) The magned assembly is just behind that, = and the height adjustment is in the front.  It employs a lock nut on both = the under and top sides of the rocker arm.  This allows for precise = adjusment of the roller height with the use of only one screw instead of the old = two screw type. Further, only one screw is needed as the assembly is held = in place both by the front adjustment screw and the center pinnning in the middle.<BR><BR>All this allows for complete freedom of adjustment of both  the  physical <<capstan>> height (in the = form of the roller) and the virtual capstan height (magnet)<BR><BR>The roller = allows for a minumum of friction between the key assembly and whippen = cushion. No sliding whatsoever.<BR><BR>An article on this is in the works and I = expect to publish soon. The Magnetic Assist Grand Action by Richard Brekne is an = open source development project and can be used to replace significant = amounts of lead in the keys.  Read the article in both the PTG Journal last = year and the European for more infomation.<BR><BR>Cheers <BR>Richard = Brekne<BR><BR><BR><PRE>A common misperception. It does slide. The = involute curve is the standard gear tooth profile. The important quality of the involute curve, is = that it transmits uniform angular velocity. So that as the driving gear = rotates at constant RPM, the driven gear also rotates at constant RPM, with = minimum noise and vibration. But they do slide. Make your self a paper cutout = and try it. It's also interesting to consider the angle of gear teeth. Standard = angles for spur gears are 14 and 20 degrees. 14 degree teeth are smoother and quieter, and have a longer wear life because at a given load they have lower contact stress. In fact, zero angle or negative angle would be = even better, from a contact stress point of view, but with small or negative angles there is a geometry problem known as "undercutting", where the = base of the tooth ends up narrower than the contact area, and is prone to fracture. 20 degree teeth are a compromise, used for pinions with very = few teeth to prevent undercutting. So does a capstain slide on the wippen cushion felt, except for the = instant that the contact point passes through the "magic line". Before and afer that point, the Overs capstain slides the least, standard vertical = capstan slides a little more, and the Steinway backwards leaning capstan slides = a little more than that. more than you wanted to know, and it still does not explain why S&S = might have done that. Mike</PRE><BR></BLOCKQUOTE></BODY></HTML>