Leadpipe Article -- Help by giving a critique

Discussion in 'Trumpet Discussion' started by MUSICandCHARACTER, Mar 15, 2004.


    MUSICandCHARACTER Forte User

    Jan 31, 2004
    Newburgh, Indiana
    I wrote an article about trumpet leadpipes for my website. The website is aimed at beginners and parents, along with the advancing student. So I wanted the article technical enough to give good information, but clear enough to understand. Any advice or constructive criticism would be most welcome!


  2. dcstep

    dcstep Mezzo Piano User

    Nov 27, 2003
    Very nice. I'd just make the distinction between the mpc receiver and the leadpipe. They're really two separate things. Of course, that brings up gap, double sheathing, etc., etc. Given your target, you may have gone far enough.

  3. Tootsall

    Tootsall Fortissimo User

    Oct 25, 2003
    Yee HAW!
    Echoing Dave's response; it's pretty good as written: but as an engineer I would take exception to your "technical definition of "Venturi" which misses the essential element that creates a "venturi".. that of a narrowing followed by a subsequent conical expansion in the size of the opening that forces the flow to a) accelerate at the narrowing, and b) decelerate during the subsequent expansion.

    What this does to the airflow is that the increase in speed causes the flowing fluid (gas in this case) to exchange static pressure for dynamic pressure (if you hook a pressure gauge up to a venturi at it's narrowing you'll see that the pressure is significantly less than that where the venturi is larger and the air velocity is less). This is how a carburetor (remember them?) uses air flow through the narrowing in the "throat" to suck fuel out of the carb bowl and blend it into the airstream flowing down into the engine.

    Now, the above use of "venturi" is related to flow of a fluid ("gas" is a compressible liquid) in a conduit, but we have seen that it is possible for a trumpet to sound without actual airflow through it; studies involving building a diaphragm into a mouthpiece to prevent airflow while permitting sound waves to pass through have been performed. In one of his technical papers (ITG1999) Derek Smith demonstrated this http://www.rsmi.u-net.com/

    This leads to the question as to what effect the venturi has on sound if there is no flow through it: the answer lies in the efficient focussing and reinforcing of the sound wave due to the conical nature of the leadpipe. Again, this is brought up by Derek Smith in that same article. (and has certainly been mentioned more than once by Jack Kanstul when referring to his father's knowledge of brass instruments!)

    Anyway, the upshot of all of this is simply that the "technical" or "engineering" definition of a venturi is rooted in it's conically expanding shape and the effect on any fluid flow through that conduit and due to that particular shape. It is certainly NOT "cylindrical"!!

    MUSICandCHARACTER Forte User

    Jan 31, 2004
    Newburgh, Indiana
    You should have read the email another engineer sent to me that made me come up with that definition. It was the best I could do to make it understandable (he argued that the venturi starts with the mouthpiece and then went and took me to task!).


    My physics is in my past -- although I had a lot of it (being a undergraduate meteorology major). Thanks for the input. If anyone else has suggestions, I would gladly hear them.

    I think I will add a bit about the mouthpiece receiver without getting technical.


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