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jim mcavoy

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Everything posted by jim mcavoy

  1. This also works when using a little skill and is equal to a light tap with a felt hammer
  2. sometimes working on an old Junker too ....it is, for me, an 'in situ' application
  3. yup....my knuckles tend to be a little tender ....arthritis
  4. these are designed to shed and have to be replaced...not a big deal they are consumed more by re-flattening ..it's just a finishing stone... pressure is quite light
  5. I use a 'home brew' hard felt hammer at about 7 grams +/- ..it is non resonant and won't mar the finish ... a striking mallet from a piano would also work ...the convention is to soften it with olive oil on old mallets (I like 3 in 1 oil...it doesn't harden up as much) The thinking is that with a hard mallet you also hear the striking head resonance (and the impact) I find a knuckle to be variable Edit...I use this for evaluations mostly Jim
  6. perhaps you are simulating the pressure of the strings (to some degree) to see what else moves or doesn't move?(in the static state)...kind of like mini-turning moments?
  7. this is bench learning .... make up some practice pieces various sizes and shapes (violin like segments)and play with them 1)First blush...stop when good enough 2) it follows mass and stiffness...try it on a bow (dampened) to see what it is like
  8. nodes and anti-nodes a super simple explanation :(see watch it) http://www.physicsclassroom.com/class/waves/Lesson-4/Nodes-and-Anti-nodes
  9. the procedure here,for me, is with a thimble lightly tap on a dampened plate (you only hear the wood) To adjust sand or scrape accordingly, It doesn't take much to get an (uniform) increasing or decreasing tap tone .....You are really hearing the taper and the tap tone is rather subtle, and the pitch is quite high I also use this on a cheap bow that has problems...Quick fix .....(I got this from another member on this forum, who will speak up if he wishes) a few licks with 600 grit sand paper or the same thing with a scraper makes a big change! soft ground: in concepts, one is adjusting mini-nodes on a progressive spring Jim
  10. good advice and the clue is building to stiffness ....It works for some, but not all I believe no two builders would use the same technique (flexing)to arrive at a finished violin...not something that can be packaged and sold on the street corner....It is learned at the bench , and only then if any one builder can do it at all! the trick is to get off home base, some can And others can't ..... There are other ways to get to the same point
  11. This is soft ground for me...I think it is an over-view to see how the plate is coming, if there is an evaluation, it is subtle (but there)
  12. Why not ...if you use colored caulk on a plate and overcoat it with spray lacquer you have a lasting record... best if there is no color key
  13. Davide, have you spent any time looking at the transitions (flexing)in the lower bout ...longitudinal, torsional, and traverse bending ...say using clock points 3 to 9? (I and 2 points at a time) (and conversely in the upper bout) ....not for a 300 pound gorilla Jim
  14. I know this is a reach....Have you drilled down in the production of sound to see if this applies ....I'm thinking in the areas of self replication complete with accidents
  15. Re: Davide's schema tap-tones.JPG this is the way to get the actual mode frequencies on an "any Plate"...I think ...useful for testing and documentation Well done Davide! Jim
  16. this is the piece in question ...Quality is not the greatest... to read it, it is best to print it out This is the cross-over with good documentation Jim
  17. I think it is a note that has trumpet like qualities (not violin) and the sound is harsh and distinctive...content is messed up for me , a 'wolf' has a destructive warble ( 2 resonances beating, within 19 cents ) To find it, I use a mechanics stethoscope and listen to the plate while plucking the string ..if not an open string, I use a capo ...There are others that can find a vibration just with fingers (but I can't) for me a trumpeting response is quite rare...2 times in 40 some years Jim
  18. Harris says that string tension causes the top length to shrink and width to grow and has numbers to back that up How ever I like Don's thoughts better...K.I.S.S ..(keep it simple stupid)
  19. I have a violin that was made 30 some years ago and it held very well ...not true for the glue you get today! Jim
  20. I had a sneaking suspicion (hence the thumb nails) but if I was called on it, I would be dead in the water! ....it's still murky for me thank you for your thoughts....If there is a connection, I expect the modes will show up by default! and they are easy to test for. Jim
  21. This makes more sense in the Why is the back plate arched topic....nice try though I have my senior moments also Jim
  22. I think, The above, coupled with Connor's nuance is what I was looking for ...I do know...There are times when subjective 'tip the scales' I am sure there are other clues, that have yet to come out.. ( I think Davide is chewing on something ...within the modes) Jim
  23. thank you Connor this speaks volumes to me ...a nuance, perhaps, but one that I can understand Jim
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