---------------------- multipart/alternative attachment Hi Bill.. Excellent posting, and I thankyou for it. A couple comments.. Bill Ballard wrote: > I'm not even convinced of the importance of these "magic lines" (or > axes, as I belive engineers would prefer to call them). This was the first thing that struck me on my first real attempt at getting into this stuff. The magic line between the balance rail pin and whippen center just didnt seem to be important at all. And setting action spread based on this seemed a big error. Action spread seemed better set from aligning the hammershank perpendicular with the jack center. I was left wondering about what friction concerns this magic line might have.. you seem to deal with that below so I will get to that there. > The rep-center/knuckle-contact/hammer-center axis is simply unattainable > (excepting of course the old Aeolian shanks). Funny that this should come up just now... I bumbed into an article by Sam Powell RPT from 93 dealing with this exact subject matter. It makes a very good case for this second magic line, and for not useing large knuckles due to the increase in friction between the knuckle and repetition lever the resulting neccessity of lowering the whippen causes. This of course intrigued me so I got out my Renner action model and started looking closely at it. This " rep-center/knuckle-contact/hammer-center axis" as you call it was indeed unobtainable (unless a few major parameters were changed... hammer bore, an even smaller knuckle etc) Another thing I noticed about that second line was that attempting to get the knuckle to meet that line at letoff (by changing spread alone) was at odds with spread concerns relating to the hammer shank perpendicular / jack center. The wider the spread, the higher this second magic line was, yet the spread needs to be wide enough to keep the jack center off the B- side of the hammershank perpendicular.... > And I became > disenchanted with the key-center/heel-contact/rep-center about five > years ago. I had moved a heel forward, and moved the cap line to > match, and was wondering whether I should use the Renner heel to > match the profile of the original (moving the cap-heel contact line) > over on a horizontal line, diverging from the key-rep axis. My other > choice was a taller heel which in the new forward position, would > drop the cap-heel contact back down towards the key-rep axis. This is exactly what I have done on my Duysen grand... thinking I should play it safe... "dont screw with the magic line" ( grin until you know better at any rate) > > You'd think it would prefer the latter. You'd be wrong. Staying with > the magic line increased both the BW and the Friction. Both were > increased simply as a function of the extra weight of the tall heels. > Keeping a consistent heel height (and weight) avoided this extra > freight. Interesting.... next time through I will look very closely at this. > Sort of like the article which Ken Sloane published in the > CAUT newsletter about 10 years ago. Found that a Steinway D action > was cleared of it's "truck-ulance" by switching to 17mm shanks even > though the jack-center/knuckle-core axis got seriously bent. What > looks the prettiest doesn't always play the best. This also is very interesting... especially in light of Sam Powells very fine argument, and my dinking around with that last night, I must tell you.... it DID seem like the closer I could get the knuckle / whippen contact point to this second magic line, the lower the friction there was... very feelable really and very obvioiusly visable when you look closely at it in movement. Yet it was impossible to reach... Even lifting the shank up with my finger to string height left the knuckle well below the line. Only hammer bore or knuckle size could address that much of the problem (outside of re-designing the whippen itself,, ie one could bring in the jack center towards the whippen center and shorten the jack a bit..getting a bit fetched tho...) > Action efficiency? Yes, you can describe it in terms of the measured > friction. But once you start measuring changes in friction brought on > by the various ways to change the way an action is "hung", you > quickly find that although fooling around with spreads and axes may > fine tune it for you, the "heavy lifting" (pun intended) is really up > to this business of tuning mass and leverage in an action. Hmmm food for thought... Still cant help but think that the best results of Stannwoodizing an action would be from first assuring best possible top action spread configuration before dealing with UW/DW and BW measurements... FW, KR, and WBW can be taken independently. Guess I am just going to have to "experience" this on my own. > Yes, I be as shameless in my promotion of the Stanwood Metrology as > "the other Bill" is about HT. Well, he's certainly got me very intrigued... but like I say... before going to take his liscence class I want to work up as good and solid an understanding about as much of all this as I can. I want to get the most out of that short time when I get there. > > IMNSHO. Grin... Humbleness is over rated > > > Bill Ballard RPT > New Hampshire Chapter > -- Richard Brekne RPT, N.P.T.F. Bergen, Norway ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/eb/58/5c/d8/attachment.htm ---------------------- multipart/alternative attachment--
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