Farrell wrote: > I am evaluating relocation of the capstan line on my Boston grand because > the wippen heel cushion/capstan contact point lies well below the "magic > line" between the wippen center pin and the key bottom at the center rail > pin. At full key depression, the contact point comes just up to the magic > line. > Grin... just make sure you have correct hammer to string distance and letoff and drop adjustments, proper key height and dip and correct spread BEFORE you check contact point at the magic line. Assuming you have done this then ...... > I made a little adjustable capstan that I can slide back and forth along the > key to search for the "sweet spot", as defined by Bob Hohf in his recent PTG > Journal articles as the capstan location where downweight is least and > upweight is greatest. I also made a little temp capstan thingy... But it was the length of the capstan and whippen cushion combined and could be "adjusted" by adding paper punchings.. I used this to go for ideal whippen travel for a given key height / keydip. Havent tried Hohfs definition yet.. might be fun to compare the two. > Moving the capstan toward the center rail key pin will > increase action efficiency (Why does there seem to be no trade-off? Am I > missing something?). Lets say I move it 10 mm toward the center rail pin (I > know, that's alot - just an example), up and downweight is more favorable > and the contact point crossed the magic line at half its travel - Perfect! > But, I could, for the sake of arguement, install a taller wippen heel, lower > the capstan, and move it even further toward the center rail pin, thus > increasing action efficiency even more while keeping the heel/capstan > contact point right on the magic line at half key depression. What limits me > from doing this? If you go in too far you will get... shall we say... to efficient. This efficiency is also connected directly to touchweight. You are changeing leverage.. move in too far and the touch will get like really really light. You would have to have massive hammers to deal with it and there are optimums with hammer mass as well as optimums elsewhere. Until we (you and I,,,grin) know more I would suggest that you stick to getting as close to Stanwoods 9.0 grams combined key ratio and whippen radius weight figure, while at the same time shooting for optimum whippen travel (ie jack just clears the knuckle at letoff /drop). Keeping the contact point on the magic line as well. If you have to change whippen cushions to do this then do so. (tho I would be suprised if you had to in a Boston) > Key thickness? (I hope there is something else!) Common > sense (or what I perceive to be) certainly suggests that I leave good enough > alone, but I want, er a, need, to understand the what and why. What? Why? > Anyone? ?-) We arent going to get a lot of response to this thread me thinks Terry. Jon Page has been very helpfull to me, and probably the best help he has given me is to kindly and patiently kick me in the butt to get my hands on experience going. Tho I would welcome more discussion on this from others. I am really not sure how many techs actively manipulate these parameters so much. Most techs I know learn to regulate, but not how to set up regulation parameters. Have you tried sending copies of your queries directly to Bob Hohf ? I am not sure he subscribes to the list.. Keep us posted anyways. (me at least.. it helps me learn this stuff you "hear" you think and ask questions) > > > Terry Farrell > Piano Tuning & Service > Tampa, Florida > mfarrel2@tampabay.rr.com -- Richard Brekne RPT, N.P.T.F. Bergen, Norway
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