This is a multi-part message in MIME format. ---------------------- multipart/mixed attachment Fred , I don't see the radius as a curve, and have not find 2.5 centred on the shank to give a very good checking, in fact too round for my desire, the checking surface is then too high on the tail or the checking is too hard, if the bottom of the tail is used. Then I had to reset all the backcheks, so I am not convinced with this process (Spurlock instructions) Indeed when looking at Steinway hammers, I see the round part to be centred somewhere above the shank, and even then I am not sure (like you) it is a pure radius. I usually prefer doing the tail shaping with the hammers hang and all hold together in a special setup (a large gig in steel), then I round the tails with a sanding machine and finish by hand. Talking about checking, for Steinway, I've been said also that low checking add power, but high checking give repetition, and checking to the highest without the tails rubbing when one pushes firmly on the hammer head while testing, give a checking around 14 mm, not less. On Bechstein hammers the checking can be made really high, then probably it is not that good to go too high. On the other hand Bechstein action are not optimum, so high checking helps them also . Here is a pic of 1980 Steinway hammers : at evidence this is not a simple curve, and the centre of the shape is not on the shank. Any comment appreciated . Best Regards. -----Message d'origine----- De : caut-bounces@ptg.org [mailto:caut-bounces@ptg.org]De la part de fssturm@unm.edu Envoyé : vendredi 31 octobre 2003 01:45 À : College and University Technicians Objet : RE: Pinning and Tone There are two things being said in this discussion. One is that there can be a perceived loss of power on repetition with high check, due to how close the hammer is to the string at the moment when the jack is re-engaged. I've never heard that complaint myself, but I'm sure it's within the realm of possibility, and Ed Foote confirms that he has had such a response from a performer. (The performer has the option of altering his/her technique, allowing the key to rise a bit more, and will then get the same power. And the key would have risen the same as it would have to rise were the check lower - or at least fairly close. But by all means we should meet the performer's desires if possible.). The other observation has to do with geometry of tail versus check. Certainly at the limits of high checking, there will be a point at which there will be drag on a hard blow. But that point will vary depending on the geometry involved. If you have optimum geometry, you can get 3/8" check without having the drag problem - I'm convinced of this through experience. What exactly is that geometry - or are there a few variations? Roger Jolly tells me that 2 1/2" radius on the tail, together with something like 70 degrees for the check is optimum. And Roger is usually right about this sort of thing (except for the rare instances when he is wrong <g>). Steinway is using 68 degrees for the check, which keeps the top of the check away from the tail a bit longer, or so I picture it to myself. However, when I was told the radius was 4 1/2", I thought that would mean the bottom portion of the tail would tend to graze on the way up, and would dig in on the way down, rather than creating a good friction bond. Hence my hypothesis that perhaps they do machine to a radius of 4 1/2", but from a point above the shank (which would kind of give you the same angle at the bottom of the tail as a far shorter radius from a point on the shank, and might actually give better clearance on the way up). In general, according to my understanding, a smaller radius on the tail and a more acute angle for the check will yield higher checking without drag. But at some point that falls apart, because the check and tail are at less and less optimum mating angle when they come together on rebound. Does all this make sense, or am I off on a shaky limb here? And is an arc of a circle the optimum shape for a tail, or is there a variant that would work better? (I am thinking of a mild parabolic curve - starts like a circle segment, but the curve gets steeper). Or is what I have suggested Steinway may be doing another wrinkle that works? Regards, Fred Sturm University of New Mexico Quoting Jim Busby <jim_busby@byu.edu>: > List > > I need to clarify that Richard Davenport says it engages slightly > when > the backcheck is close (high checking) on hard blows. As I understand > it > if it is regulated that close the tail may skim the surface on a > hard > blow because of shank flex. Could be. I'd like to see his > presentation > and those films. > > Thanks, > Jim Busby BYU > > -----Original Message----- > From: caut-bounces@ptg.org [mailto:caut-bounces@ptg.org] On Behalf > Of > Jim Busby > Sent: Tuesday, October 28, 2003 4:57 PM > To: College and University Technicians > Subject: RE: Pinning and Tone > > Alan, > > According to Richard Davenport the backcheck does slightly involve > the > tail if you look at those high speed tapes of it. I'd like to see > it, > but he says that higher checking does result in less power as > Richard > said, and Ric. clarified for me. As Ric said, more drop = slower > rep, > and higher checking = (slightly) less power. I agree. > > I misunderstood Richard and thought he meant higher checking would > give > slower rep speed but after Ric. pointed out my misreading I re-read > it > and Richard was actually very clear. My "Oh" meant "oh, do I feel > dumb > that I didn't read it right the first time." Sorry if anyone read > more > than that into it. I'm not mean spirited at all and would never > intentionally offend anyone. > > Thanks, > Jim Busby > _______________________________________________ caut list info: https://www.moypiano.com/resources/#archives ---------------------- multipart/mixed attachment A non-text attachment was scrubbed... Name: 16080011.jpg Type: image/jpeg Size: 54213 bytes Desc: not available Url : https://www.moypiano.com/ptg/caut.php/attachments/79/79/5b/b4/16080011.jpg ---------------------- multipart/mixed attachment--
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