This is a multi-part message in MIME format. ---------------------- multipart/related attachment ------=_NextPart_001_00E9_01C543B1.B27A2970 Hey Ric, Cool design! :-) 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? 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. 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? Always interesting to see your innovations! Peace, Sarah ----- Original Message -----=20 From: Ric Brekne=20 To: pianotech=20 Sent: Sunday, April 17, 2005 5:26 PM Subject: Capstans... which brings me back to.... 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. 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=20 Richard Brekne 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 ------=_NextPart_001_00E9_01C543B1.B27A2970 An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/4a/dc/42/00/attachment.htm ------=_NextPart_001_00E9_01C543B1.B27A2970-- ---------------------- multipart/related attachment A non-text attachment was scrubbed... Name: not available Type: image/jpeg Size: 5078 bytes Desc: not available Url : https://www.moypiano.com/ptg/pianotech.php/attachments/f4/95/30/31/attachment.jpe ---------------------- multipart/related attachment--
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