This seems overcomplicated. Under normal conditions string height minus hammer flange center height = bore distance. Hammer shank horizontal at impact. I don’t care whether the string is at a nominal incline to the bridge. In other situations (like the Bechstein) where the formula above gives you a bore distance that compromises stretch clearance, strike point access, or a just a hammer that is of reasonable length (and weight) I throw out the shank horizontal at impact requirement and go with a reasonable bore distance to get stretcher clearance and strike point accessibility and then add some rake to get the hammer perpendicular to the string at impact. Again, ignoring any nominal incline of the string. In fact, ignoring the string incline is a good way to take into account some inevitable hammer wear. The hammer may start out slightly (almost immeasurably) undercentering, but within a hundred or so hours of playing it's probably right on. It works and worrying about cosines and various unnecessarily complicated formulas borders on mental masturbation. Of course, some people are into that. David Love davidlovepianos at comcast.net www.davidlovepianos.com -----Original Message----- From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Richard Brekne Sent: Saturday, June 21, 2008 1:53 PM To: pianotech at ptg.org Subject: Bechstein B hammer rake / more thoughts Hi Stéphane and whomelse ever. Been digging through the archives and find that this querrie of mine dont seem to have an answer. A couple interesting posts that are relevant... First one from Dale Erwin where this bit about the horizontal shank at impact being important comes up. https://www.moypiano.com/ptg/pianotech.php/2006-November/198133.html Then a similiar instrument to my own is being discussed in the following exchange between David Love and Jon Page back in 2002 where Jon more or less tells us to give up trying to make either boring protocol work. He does go for the hammer being perpendicular to the string at impact, but the angle to the shank is a whatever works affair. Jon starts this by saying one has to basically throw out the string distance minus center pin distance approach on Bechsteins. https://www.moypiano.com/ptg/pianotech.php/2002-April/106174.html All this and more reading leaves me narrowing in on a conclusion that we dont actually have a bonified bore distance formula that we can really count on. Now that doesnt sit right for some reason. There should be a way of calculating a more then usuable bore length and rake angle given a few basic measurements. Still seems obvious that the one thats been defacto standard as long as I've been reading this list is undependable. Cheers RicB
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