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Tuning tárogató with mpc insert.

Discussion in 'Tárogató' started by kymarto, Feb 2, 2013.

  1. kymarto

    kymarto Content Expert/Moderator Staff Member CE/Moderator

    Middle finger top C is not usable on any horn AFAIK. Cross fingerings do not work in the upper part of the upper register as they do in the lower for acoustic reasons. If you play recorder you will know that the fingerings for Bb and C are totally different in the two registers.
     
  2. It wasn't particularly cheap, but as it is now, it is just what we call a "hanger" .. just hang it above the mantle and knowingly answer your guests who ask, "what is that?"

    I did some measurements on the TSO (tárogató shaped object). The telescoping gauges available could not reach the entire

    lengths of the two instrument joints, but the trends seemed obvious. The first figure shows the inner diameters vs

    distance from the tip of the tenon on the upper joint. The bore is very close to circular at all distances except where

    it is narrowest, so I do not believe the distortions from conical are due to shrinkage of the wood. I do restorations of

    antique guitars and need to know how wood shrinkage works.
    TSO bore measurements graph.JPG
    The spreadsheet program allowed fitting a line to the data for the lower joint, and showed a taper of 1:18.45. In the

    figures, this line is the upper one at small distances. The other line has a slope of 1:17.5 as previously suggested by

    George from similar measurements on his instrument.
    TSO bore measurements detail.JPG
    The second figure is a detail of the data, showing what is happening in the upper joint. Clearly there is a constriction

    from the top end to about 1" in, and the bore remains narrower than either the 1:17.5 or the 1:18.45 line up to about

    7-8". After that, it flares out slightly and the effect can be seen by eye when looking inside the bore. I overestimated

    the step in the bore between the upper and lower joints in my previous post - the step is due to the flaring.

    If the bore needs be conical (except, perhaps, the last 1-2 inches at the top and some part of the bell) the oversized

    portion of the upper joint from 8-10" should be filled with something and worked back down to make a smooth transition

    between the two joints. Again following George, and definitely at my own risk, I would make a conical tool with 1:18.45

    taper and enlarge the upper extreme of the bore; any filler material placed in the flared area could be leveled with the

    same tool.

    I too made a cone of maple at 1:18.5 taper. A hacksaw blade was tapered at one end, sharpened, and glued into a slot

    running the length of the cone to make a single flute reamer. It would work like a violin-peghole reamer.

    Incidentally, the URL http://mysite.verizon.net/res8o1o8/SopCompare.htm shows measurements on two C soprano saxes, with

    tapers of about 1:16.5 ("Taper" = 0.060 means 1:16.5). Chen, Smith, and Wolfe

    (http://www.phys.unsw.edu.au/jw/reprints/ChenetalAA.pdf) indicate that the half angle of the taper of a soprano sax is

    1.74 degrees, or 1/(tan(1.74deg x2)) = 1:16.4 . The TSO measurements of 1:17.5 to 1:18.5 are not much different.


    Now that George has commented (again, I think) that the bore should have a cylindrical section, I will refrain from

    working on the bore for a while. Clay in the mouthpiece has not done enough.

    Is anyone willing to make similar measurements on an instrument that plays decently in tune? What I want to know is: How

    long is any cylindrical portion of the bore nearest to the mouthpiece.


    ....... C.S.
     
  3. kymarto

    kymarto Content Expert/Moderator Staff Member CE/Moderator

    My Stowasser is beautifully in tune. Top cylindrical section appears to be about 1.5-2cm.
     
  4. As I mentioned in the Thread tárogató Remanufactured Part Deux, I could not resist applying my conical 1:18.5 reamer to my TSO. The initial results were encouraging, so I did some more reaming. Both octaves were sharpened significantly - so much so that I had to pull the mpc out about 1/4 inch. Remembering how I started this project, I removed some of the clay I had put in the mpc and pushed the mpc back on the full 1/4 inch. NOW IT IS NEARLY IN TUNE EVERYWHERE. The entire upper octave is still slightly flat, so some more reaming is in order, but not much. I'm trying to get my hands on some long handled telescoping gauges so I can document what has been done before doing any more.

    Recalling Kymarto's comments above about his Stowasser having a short cylindrical section, my TSO (rapidly becoming a real tárogató) still has a non-conforming section at the top of the upper joint, but it is not cylindrical - it is conical but in the wrong direction. It is also only 9mm at the end and yet narrower inside. This geometry is not discussed anywhere I've seen, not even in G. Scavone's dissertation. Maybe the next step would be to make it cylindrical. Any comments?

    The section of the bore I am modifying is not AT the pressure antinode of any notes except the highest in the second octave, and the amount of enlargement at those positions is very small. The largest changes have occurred closer to the top of the upper joint, but not exactly at the end. The cone frustrum effects must be at play. Now is the time to proceed even more slowly.

    At least the TSO is now playable in public. I'm modifying a Yamaha 4C sop mpc to fit. This has a much higher roof so I have hopes that it will make the lowest notes easier to play. To counteract the larger average internal diameter near the reed, this mpc has a shorter chamber.

    Thanks to all who continue to contribute to discussion of this project!!

    ........ C.S.
     
  5. kymarto

    kymarto Content Expert/Moderator Staff Member CE/Moderator

    Well, you certainly don't want it reverse-conical. I would make it cylindrical, but that will make the upper part of the second register slightly flatter. You could try first putting a bit of wet newspaper in the very upper part of the top of the tenon--making it in effect a cylinder by narrowing the enlargement at the very top. If that does something good, you could use wood putty to narrow the top, instead of taking material out a bit farther down. I've never heard of a reverse cone in that region, and I am wondering if some soul took it upon themselves to modify it in that way for some reason. If the newspaper trick makes the upper part of the second register sharp, then you could think about reaming it out to be cylindrical.
     
  6. Thanks for the suggestion! I did this and the top notes went way sharp, so I drilled out the narrow section to 9.5 mm (by steps of 0.2mm to keep it on axis). Immediately, the lowest notes became easier to play, and the entire upper octave went slightly sharper. It is getting closer, but needs some more tapered reaming.

    What I suspect is that the reamer they used was expensive, so they kept using it even after incorrect sharpening made it weird. Looking at the black lacquer in the chips in the toneholes, they didn't know and probably didn't care that it was never playable.

    Both the sockets and the tenons are tapered and sloppy. I built up the diameters of the tenons by winding with button thread (a designation for a heavy sewing thread) and CA, then put cork in the grooves. It all fits well now and doesn't wiggle and leak any more.

    Update: The Yamaha 4C mpc I modified is much mellower sounding than the Rico Metallite, as expected, and causes similar intonation. The lay could be a little more open.

    C.S.
     
    Last edited: May 13, 2013
  7. Glad to hear you're getting closer!

    The combination of bore work and a new MPC I made (separate thread) to be used with a soft reed made my instrument play in concert pitch over 2 octaves with almost no effort. Looking back, it was hard to play before these changes. And I was shooting in the dark a lot, as Toby mentioned. I got lucky.

    George
     
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