Thanks again to Isaac Oleg for generous time taken to comment from his experience. I'm particularly interested to hear similarities and distinctions between work in Europe and work in the US. Dealing with sectional pinning issues is mostly a European challenge, although it happens to be one I have faced this week!
The extreme squaring/spacing I required of the Pleyel hammers for tonal reasons were done through shank heating, twisting/bending, and re-setting, And both of these processes are tough on the hammer centers. Some were quite loose to begin with and became very unstable by the time the work was done.
I have a method of tightening both cloth and hard bushings without additives and without disassembly, which worked with the Pleyel's through-the-butt bushings and sectional pinning. I employ the sharp point of a broach, inserting it in the bushing material, generally outside the assembled part, and turning it around the surface of an imaginary cone while applying pressure. I follow this with working the part to settle the spot I have just compressed. I can usually cut the swings of a grand hammer in half, if I want to, with stable results. My insertions are always in pairs, applying the same treatment mirror fashion to both bushings. The WNG hard bushings respond well to this treatment but require a delicate touch to not go too far. (Too far just means popping the pin, burnishing the bushings with one of their incrementally-sized burnishers, and reinserting the pin. But it's a big slow down.) Anyway, this technique worked well from the accessible inside of the sectionally-pinned bushings without taking things apart.
On another point noted in one of Isaac's comments, the picture of the treble straight-bored hammers half-filed (shown in the previous blog posting) was taken with them suspended on the support of the sliding top of a Grandwork™ Squaring Platform (SP). Because the hammers are not flared, because they have been traveled to vertical (using the SP), and because the they have been squared to vertical (again, using the SP), their being at strike is not crucial to producing an excellent job. But it is a convenient place to work on them and it is where the hammers contact and later mate with the strings. What is crucial, in my view, is that their crowns are parallel to the the plane of the action (the keybed in the piano). The Grandwork™ Regulating Rack (RR) provides the information needed for this. Then the gang filing does a superior job to hammer-by-hammer filing, particularly in achieving an overall sectional hammer shape.
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Sorry last phrase, Max correction ( papering) seem to create more instable twisting motions of the shank during the stroke. (may be there is some force orientation change at work, or the initial too inclined center generate some twist impulse. ) hammer going it’s path just for spacing, seem to send the shank a more constant excentrée force, hence à more stable motion and impact. Those are more gut feelings than tested theories, but many do that. So hammers are led directly with that progressive inclination, easily tested when gluing by comparing travel motions with 2-3 hammers. This sound as the faster but also an acute method to glue the hammers. Now sure gigs vertical references can help. To be added, all grand pianos from Yamaha or German brands use a 2 3 mm over centering to smooth let off. That mean, the shank is 2-3mm above parallel with keyboard when the hammer touch the string. The slant from bridge to can be 1 to 2-3 degrees so the hammer can be installed 90 or near 90 on he shanks. Traditionally it is 91,5degrees for a 3mm over centering, but string plane is considered horizontal/parallel to keybed, which is not in reality. I really think the rake angle influences the stroke as it plays a role on the frequency of vibration (waving) of the shank as the way it can accumulate ND release energy. Have the shank enough time to straighten between roller/jack loss of contact and hammer impact? I don’t know for use but in staccato, tone the shank is not pushed all along to 2mm from the strings. I see bass hammer impacting strings while pointing toward the pianist more than expected. That may obviously vary depending of many parameters, but pianist touch is one of them and a too linear shank flex does seem to me a poorer range, for what I heard from pianists.
Hello, you made a good description in the CG and space blog. What I learned is based on German and Yamaha methods. Basically when gluing the heads, the traveling and papering are tested. With some experience the shanks that will need a little more papering have their hammer glued slanted so less shank heating will be necessary. They are glued on parallel and ideally traveled shanks (I see how your gigs can help there to refine the job, done in 3 passes usually ) Vertical from capstan and whippen screw are the initial references (of course after action position and a few samples hammers are installed). The heads bore are adjusted with a conical reamer (5>>6 mm Dia helicoidal-for plastic or aluminium) Then glued from samples (gluing from both sides of sections avoid Bowing) The hammers around the break are travelling parallel, but need to be papered and that put them more vertical while keeping spacing) Shaping is done so the strike line is horizontal, and that matters more than anything as this is providing a reference line. On a modern piano with vacuumed plate the strike can be precise and no much compromise necessary in regard of the bowing of the strike line. But even with Grey iron plates it helps to begin with that horizontal reference, and then correct the strings plane or the crown depending of what is best. I seem to find that leaving the assembly CG “inside” the rotation plane (a little at the right of shank for a bass hammer for instance provide a smoother more energetic stroke) As you noticed that CG is about 1/2 inch above the shank, and near the hammer head on the shank. May be as we are with the circular motion that create acceleration force, sending some unbalanced effort on the center and shank, beginning with a CG more centered toward the lateral “axis” of that rotation, the energy is better balanced that way. Extreme correction of the lateral motion of the crown seem to create more in testing of the shank Sorry this would be better in your last post. Graphs would help as pictures. .. Best regards, .
I mean the left side, of course ..
Your Gig look neat, I see you can use the bottom of the tails or the shanks as a reference for gang filing or filing. I use a 2 parst wooden support S&S type, so the front keyboar side) of the heads are shaped with the tails supporting the heads, then the other rail is turned 1/4 turn then the shanks are suse , an the hammers are a little above strike height. This is for crown and back shaping – the higher spot give space for the filing strips, it is particularity necessary for treble hammers , the higher location compensate a little the twisting of the hammers that happen with gang filing, so the right side is file enough (medium hammers) I agree that the “parallel” strike line is a good idea, anyway once shaped the line of the hammers should be precise enough to show us strings level last mistakes.
Hello. To avoid being hard on centers, of course electric shank pliers are a must. If not I oscillate lightly the head while heating until I feel the wood soften. Renner sells the kotibe shanks for those actions. The trick with a needle is efficient. Not really very long lasting with seasonal changes, but a good top. (good for aluminium rails, also) Most “play” on centers come from cloth compression, hence the advantage of moisten to get things back. The shanks are oriented so they bow front back, but not sideways. But it happen we have to straighten them and it is difficult not to push on the center too much then. (using “smiling” pliers) Regards
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