Johnmasters

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About Johnmasters

  • Rank
    Enthusiast
  • Birthday 05/08/1944

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  • Gender
    Male
  • Location
    Columbus
  • Interests
    Physics of violins
    Finite element analysis for eigenmodes, stresses, whatnot

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  1. What??? Are you shaming Columbus, Ohio or the Jackson Gulden Company? The factory has been gone for some years now, and I doubt that many locals even knew it existed. I live in Columbus, and it is a very clean and desirable place to live.
  2. Wouldn't a lucchi meter measure compression wave velocity? It seems to me that a more relevant measure would be the speed of a transverse wave in a plate or sheet of a given thickness (stiffness.) They could be made equivalent couldn't they, by juggling a few variables. At least made to correlate.
  3. Whoa !!! Have you been regraduating Strads and DG's ?
  4. Given that Heifetz was somewhat regarded as a violinist, it would be interesting to preserve any information about his playing or need for a "special neck."
  5. Is it true...? A piece of gossip I heard was that Perlman was to perform a concert on this violin, but he refused unless a new neck was fitted to it. I was appalled that a museum would allow such a thing. So did that happen? And if so, it would be pointless to ask about setup details.
  6. I have found that those jaws slip easily. I have used 400 or 600 silicon carbide paper folded so that the grit is outside. Put one under each clamp. (The paper does not tend to slide, but if it gives trouple, a dot of Titebond on the paper side.)
  7. And doubtless the violin was sold in the accompanying case.
  8. Yes, prevent the formation of oxides of Chromium. You have to know why you wound up with the oxides in the first place. (The dichromate-tannin reaction did not go to completion.)
  9. So use dichromate in an acid buffer. What is the problem?
  10. I just said that it happened with no idea what that would mean for sound. However, when people say that arching is important, the most obvious thing to me is the line of inflections and where it shoul be. The line of inflections is where the Gaussian curvature goes to zero. (Is positive in the middle and negative around the edges.) The creeping I had in mind is what I notice over a few weeks perhaps.. Even a couple of days makes a big difference sometimes with a new violin.. Not even playing, just being strung up. I have no idea what might happen over years or why it would make a difference. I don't think that the final shape is of as much importance as the stresses whichi are minimized. Perhaps the sheer stress through the plate and any damping that may be associated with them.
  11. Speaking of potassium dichromate. Most will have noticed that it sometimes has a greenish cast. This is from some oxide of chromium and results because the reaction in the wood does not go to completion. This is corrected by Carl Becker's stain. This has the dichromate in an acid buffer solution involving dilute nitric acid and boric acid. It is not a Becker "secret." Buffer solutions are commonly used in chemistry.
  12. I do not believe a violin "adjusts" itselt to a player, there are so many normal modes. Also, the normal modes are not any kind of a harmonic series such as those in musical notes. I just wonder though, if there is not a minimum potential energy that can be found by the migration of the inflection line. A simple demonstration is to clamp a length of spring steel with the ends at different elevations and the ends moved toward each other to make a kind of sine wave. One can see that the inflection of the steel is very easily pushed to one side and it immediately goes back to an equilibrium. This equilibrium is the shape that minimizes potential energy for all of the stresses. I am curious whether a poor arching might try to drift to minimize potential energy of the stresses. In fact, a force can be defined as a gradient of potential energy within a range of motion. That is fundamental mechanics. Also, the spring steel example shows that the migration of an inflection line may be the easiest path for any deformation under stress. (before the violin takes on permenent warping which is a further effect beyond the elastic approximation.)
  13. I am in Columbus, Ohio also. My name is John Masters... 262-9254 Give a call and I welcome your visit over hear. (Clintonville)
  14. I agree with Mr. Darnton that arching is important. In particular, the line of inflections is such that stresses will cause this to migrate toward the shape of minimum potential energy (in the stored stress.) The closer to ideal, the sooner this will happen. Sometimes I find that a violin will very quickly come to an equilibrium from applied forces and sometimes it takes more time. Also, sometimes the arching may be so far from equilibrium that it may never reach an optimum shape. Also, this view could suggest why makers take both the outline and arching from a classic model and copy both totaly without understanding why. The outline provides the boundary conditions for whatever the optimum shape of the inflection line should be. DON? what do YOU think ? Finding the best shape of the inflection line may be something one could find with FEA. (That is, given the major curves in the central convex part.)