Dunno. I arc at a 3 inch pivot from the tail for longer blow pianos. Ie 48 mm and 2 3/4" for shorter blow. Checking Yamahas and Steinway they vary only slightly. It works so... Understanding the actual geometry may not shed much light on the question. Dale Dale Erwin RPT- Mason & Hamlin/Steinway/U.S pianos Pre-hung Ronsen hammer sets/Abel parts Sitka Soundboards & Supplies WWW.Erwinspiano.com 209-577-8397 -----Original Message----- From: jim <jim at grandpianosolutions.com> To: pianotech <pianotech at ptg.org> Sent: Tue, Feb 28, 2012 7:08 pm Subject: [pianotech] Grand Backcheck Geometry Lets try that with a more focused example. In determining the radius of the hammer tail for a grand is 2-1/2 -3" . WNG uses an even tighter radius, 1.5" I think. Why? THe pivot for the shank is at the flange, not 1/2 or 3/4 out on the shank. This is presumably to deal with the radius described by the backcheck as it swings into full key dip, to avoid interference. So my question (more focused-ly) What is the geometrical relationship between those two arcs? Jim Ialeggio -- Jim Ialeggio jim at grandpianosolutions.com (978) 425-9026 Shirley, MA -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://www.moypiano.com/ptg/pianotech.php/attachments/20120228/cfdc582b/attachment.htm>
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