If you really want to start analyzing the key stroke, the location of the capstan on the key will determine where the jack will end up at the end of the key stroke with a given dip, hammer length & blow parameters. An O, I have in now, did not have the jack clearing the knuckle sufficiently with the original parts or any combination from the Renner USA Parts Kit. The capstan was at a considerable angle (105 degrees) but needed to move back to move the wip through the needed distance. What ended up was to have the capstan 92 degrees (procedure described below) to the key, keeping the head in the same location. The hole was drilled back 1/8" and the angle changed. It actually dropped the KR .01 on both naturals and sharps. Now the jack is just in from of the knuckle at check-in (optimum) in stead of bobbling. A short hammer blow was needed to correct it before. A few observations I have made on well regulating actions are, for lack of a better phrase, vector alignment. Two items in particular for discussion: The juxtapositions of the jack to the shank and the capstan to the whippen. 1 In selection of action spread and/or knuckle to center pin radius, the jack should be perpendicular to the shank at rest, its interaction friction at this tangent will be lowest initially. 2 In selection of capstan location, the capstan should be perpendicular to the whippen when the key is depressed one half the dip minus letoff. (ie: .390 - 1/16"(.062) = .328 .328 / 2 = .164 .164 + .062 = .226) A spacer of .226 (arbitrary at this point) placed on the front rail punching will hold the weighted key in position. For the "O", I used 7/32 (.216). (A spacer of 3/16" did not allow for jack clearance). * While the key is held at this juncture a string is drawn from the bottom of the balance rail hole to the whippen center pin and a mark is placed at its intersection with the whippen cushion. The whippen is removed and a line is drawn through this mark perpendicular to the whippen support. Reinstall the whippen and reset the key to that half-way position. Place a rule along the line on the whippen and extend it on the side of the key. That is the location and angle of the capstan. Rig up a temporary capstan (two damper inserts on a wire) and see how it regulates, if the jack has sufficient clearance; fine. If not, find the location along the key stick for optimum regulation for your set parameters. Cushion height may have to be adjusted for br/cp line and determine capstan angle by above procedure. I was lucky, it was right where it was supposed to be. This half stroke/perpendicular setting will have the two pieces moving through the same arcs during play, while allowing sufficient after touch. The angle created between the whippen and key lines at rest will be the mirror image of the angle of them at check-in. The jack should be just in front of the knuckle with the key fully depressed not pressed into the stop felt at the end of the balancier. I have applied this theory to the last few actions and have had favorable results. I look at the capstan as moving through a distance, pushing the whippen through a distance. The whippen only needs to move_so_far. Change the capstan location and the capstan will move the whippen through a different distance. That distance determines the 'sweep' of the jack, so to speak. * The numbers I gave above are just examples and certainly not necessarily a point of contention, the procedure in general is what I wanted to pass along. Your figures may vary. No doubt. I also have a new photo of my new and improved capstan boring jig :-) The old capstan holes were drilled out to 1/4" and plugged with long plugs cut from old keys. Regards, Jon Page At 08:44 AM 04/12/2000 -0700, you wrote: >Seems to me that whatever is occurring at the end of the cycle (bottom >of dip, top of action) is probably due to the "more than a minimal >amount of aftertouch." Where the wippen is to begin with, as adjusted by >the capstan, really isn't relevant here (referring to the slapping >noise). It's how far it goes after the cycle is completed. So among >other things, shimming the stack definitely wouldn't help. > Sounds like a very strange setup. Reduced dip, I can understand. > Tastes >vary in that regard. But coupled with increased letoff _and_ aftertouch? >Boggles the mind. Close letoff is non-negotiable in my book (other than >keeping string breakage down in the practice rooms). Most pianists would >complain of loss of control. > 3/8 dip and 1 5/8 to 1 3/4 blow should work reasonably well as > long as >aftertouch is minimized. Check might need to be increased a bit to allow >clearance between check and tail on upswing. I have regulated >successfully to client's satisfaction in that ballpark. Increased >aftertouch _would_ lead to repetition problems in this scenario - >aftertouch is lost motion in reverse on key rise, with respect to >"re-loading" for a second blow. Coupled with increase in check, I can >see this might become pretty noticeable. > On another subject, where exactly is everyone (particularly Steinway) >measuring precise keydip (to within .001 inch)? Front of key? Just >behind the lip? Mid key? (I remember years ago being told Steinway >called for a 3/8 keydip at the front, but it should be measured with the >top of the block even with the underside of the keytop. I always figured >about 13/32 (.406"), measured at the front of the key was a good >starting place, to be adjusted in tandem with desired blow and >aftertouch.) I note that the Steinway manual fails to specify where it >is measured (I have assumed front of key, but would love to hear an >official version). > >Regards, >Fred Sturm >University of New Mexico > >Jeff Stickney wrote: > > > After a couple tries at reversing the process, the piano now > invites him > > to play again with the dip at 3/8", a "generous" let-off, and the hammers > > 1/2" above the rest cushions (I think blow ended up between 1 5/8 - 1 > > 3/4"). However, the bass hammers are brushing the pin block as the action > > is pushed in, repetition is not what it should be, and on a very hard blow > > there is a clicking/knocking sound that I believe is the jack slapping up > > against the hammer flange because the wippen is so high. What can be done > > about this situation? Does the stack need to be shimmed higher? The > > "inviting" touch the pianist wants seems to require a shallow dip, but more > > than a minimal amount of aftertouch. Any light you can shed on this would > > be greatly appreciated. Thanks. > > Jeff Stickney, RPT > > University of Montana > > jpage@selway.umt.edu Jon Page, piano technician Harwich Port, Cape Cod, Mass. mailto:jonpage@mediaone.net ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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