An attempt to explain reverse leadpipes

Discussion in 'Trumpet Discussion' started by docfox, Dec 3, 2005.

  1. docfox

    docfox New Friend

    25
    0
    Feb 5, 2005
    It seems I get one or two emails a week asking me to explain what a "reverse leadpipe" is. Not just what it might do for the horn, but why is it called "reversed" and how do you know.

    I have rewritten my article on trumpet leadpipes:

    http://www.ibowtie.com/tmptleadpipes.html

    I would love to have any constructive criticism. It is a hard chore to do with words and and a few pictures. Hopefully I am getting closer.

    Jim
     
  2. Tootsall

    Tootsall Fortissimo User

    4,529
    8
    Oct 25, 2003
    Yee HAW!
    Jim... I believe that "venturi" is that spot of smallest diameter usually found precisely at the beginning of the leadpipe... just where the mouthpiece gap ends. From that location the leadpipe tapers outwards into an ever-larger diameter. Take a look at the GR website: http://grmouthpieces.com/tutorial.htm ("gap" link)

    Think of the venturi in a carburetor... just where the diameter is smallest down in the "throat" area. So then venturi is not the entire leadpipe or mouthpipe but rather the beginning of the mouthpipe.

    Your stated definition of "venturi" as "Venturi technically defined: a tube or tubing that is a conduit consisting of a long hollow object used to conduct gases" is incorrect. A venturi can be used to conduct fluids, either liquid OR gaseous (those water-bed emptying devices that use the kitchen or bathroom tap is an example of a venturi that uses liquid flow to create a negative pressure and "suck" the water out of the mattress).

    In "engineering speak" a venturi converts static pressure into dynamic pressure (velocity) to create a suction... that's why a carb "sucks" the gas out of the reservoir...the velocity increases through the smallest diameter but the static pressure drops so that TOTAL pressure remains the same.

    Check out "Bernoulli's Principle" at http://www.mca.k12.nf.ca/bernoulli/bernoulliprinciple.htm .
     
  3. docfox

    docfox New Friend

    25
    0
    Feb 5, 2005
    There are more definitions of venturi than you can shake a stick at it seems. Thanks though, I will look into the links you have provided.

    Jim
     
  4. docfox

    docfox New Friend

    25
    0
    Feb 5, 2005
    Ok Ed,

    I looked at the links. I understand the basics of the Bernoulli Principle. I understand that if you run fast moving water in a water bed "drain" the faster water will have less pressure and therefore a suction will be created.

    GR calls the leadpipe the venturi. But that point is not the smallest diameter. The throat of the mouthpiece is.

    Here is the American Heritage Dictionary definition:

    One definition seems to be general, and the other related to the Bernoulli Principle. So it seems the way I am using it is correct -- I got nasty emails from several people when I said the venturi and the leadpipe are synonymous without giving the explanation I did.

    Jim
    Who has an undergraduate science degree, but is NOT an engineer.
     
  5. Tootsall

    Tootsall Fortissimo User

    4,529
    8
    Oct 25, 2003
    Yee HAW!
    Yes, I agree with you that the throat in the mouthpiece is the smallest diameter in the "entire air column" ... but the tip of the leadpipe (or mouthpipe) is the smallest diameter of the leadpipe and is known as the venturi (of the leadpipe). It would be correct to say that there are two venturii but in the explanation pertinent to reverse leadpipe I think you should to stick with the one.

    To tell the truth I don't really think that "venturi" even needs be a part of your explanation for reverse vs standard tuning setups.

    I can't imagine why anyone would send you nasty emails though; you are just trying to put forward a clear explanation so that someone can determine if they think they'd prefer a reverse to a standard (and of course you can't until you experience both.. "everything else being kept equal").

    I'd just say that a standard setup has the male tube on both top AND bottom of the removable crook while the reverse has a male tube on the bottom and female on the top. Let them figure out what the theory is. :D

    (Don't think everyone is in agreement of which is better and why anyway).
     
  6. NYTC

    NYTC Forte User

    1,137
    4
    Nov 1, 2004
    Brooklyn,NY
    Guys,
    Have you ever heard people thinking of Venturi as a Bore size?
    I get a lot of that,for some reason.
     
  7. docfox

    docfox New Friend

    25
    0
    Feb 5, 2005
    Felix,

    Now that is a new one to me. I get lots of questions about how the bore size is measured, and the differences between a conical bore and a cylindrical bore. And the infamous step-bore question.

    That is why I wrote so many articles to start with. And later some others helped me out by lending their expertise.

    I have written about 5 articles on mouthpieces, starting with this one:
    http://www.ibowtie.com/mpcmain.html

    Marc Melton was kind enough to write an article on trumpet bores
    http://www.ibowtie.com/tmptbore.html

    Here is an article on one piece/two piece bells
    http://www.ibowtie.com/bellpieces.html

    And this article about the "care and feeding of your trumpet"
    http://www.ibowtie.com/tmptcleaning.html

    These along with several others and the leadpipe article I hope answer basic questions. But certainly the leadpipe issue has been the hardest to explain. And I need to write an article about the mouthpiece gap (anyone like to give it a go?).

    Jim
     

Share This Page