The original question was whether a change in the string height accompanying by an equal and offsetting change in the bore distance changes the action leverage. My most recent comments addressed the practical aspects of making those changes even if it does to some small degree change the leverage. David Love www.davidlovepianos.com From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Jude Reveley/Absolute Piano Sent: Wednesday, March 25, 2009 5:32 AM To: pianotech at ptg.org Subject: Re: [pianotech] Increasing bridge height Sorry David, but I think I lost what the issue is? :) Please clarify...whether a change in bore/string ht affects the action leverage, whether to increase bridge height as needed or whether to adjust the bore to match string ht vagaries? My answer: Yes to all. Specifically, to address Will's case. 1. I would attempt to improve upon the plate tilt by both lowering the bass and raising the treble to an average of about 191 to 192 throughout the straight bridge. Will: What are the current bass string hts? 2. I would also try to address a vertically challenged bridge. With the s/b out, I lay the plate in place and run lines/straight edges from capo to counterbearing to see what I have to work with. The belly rail makes for an excellent reference without the s/b and bridge and allows a visualization of the longitudinal string plane prior to any loaded bearing offsets. 3. Then depending on the budget, I will use my best averaged string height to design the action from the top down. This might be as minor a modification as slight shifts in spread, rep/hmr center &/or stack location or it might get more involved by changing the key proportion with a new balancerail or even a new keyboard. 4. Whatever the case, I will "taper" my hammer bores. And yes, this in turn does have a slight affect on the action leverage but THERE IS NO PIANO OUT THERE THAT DOES NOT HAVE SLIGHT VARIATIONS IN LEVERAGE FROM NOTE TO NOTE. BTW this is still true in actions that have matched SW/FW weight ratio curves. 5. This brings us back to a previous thread on aftertouch. It is my practice to keep an even aftertouch and allow the final slight discrepencies which I have tried so anal compulsively to distill to a minimum, to be reflected in the key travel. This seems to be the preference of the concert artists and concert techs that I've had a chance to learn from. Jude Reveley, RPT Absolute Piano Restoration, LLC Lowell, Massachusetts (978) 323-4545 ----- Original Message ----- From: David Love <mailto:davidlovepianos at comcast.net> To: pianotech at ptg.org Sent: Tuesday, March 24, 2009 11:36 PM Subject: Re: [pianotech] Increasing bridge height Problems with semantics aside, there seem to be advocates for both sides of the issue. They can't both be right. Honestly, I don't know what the answer is. In terms of practicality (a separate matter) I would not hesitate to raise the string height fractionally for fear of a slight change in leverage (if there is one). Getting the bridge up to an acceptable height if it is vertically challenged would, in my view, trump any changes that might be introduced to the action. I find the opportunity to vary the bore distance in virtually every Steinway I rebuild even if I go to such pains to level the plate, raise the treble side, make the bridge height more uniform, manipulate the aliquot thicknesses, add vertical hitches, etc.. If the string heights are fractionally off, I usually don't do anything but with this B I'm currently working on I probably will account for the 3+mm rise in string height from the low tenor to the treble. It does pose a certain dilemma though: I could alter the bore distance and change the leverage, or I could use a uniform bore distance and, because the string heights vary, alter the regulation. Which is better, I wonderJ? David Love www.davidlovepianos.com -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech_ptg.org/attachments/20090325/daeb4b00/attachment-0001.html>
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