<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta content="text/html;charset=ISO-8859-1" http-equiv="Content-Type"> </head> <body bgcolor="#ffffff" text="#000000"> 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.. 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. 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. First a drawing of the rocker arm. <img src="cid:part1.00020407.07040704@broadpark.no" alt=""> 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. 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) The roller allows for a minumum of friction between the key assembly and whippen cushion. No sliding whatsoever. 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. Cheers Richard Brekne <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> </body> </html>