Dents

Discussion in 'Trumpet Repair and Modification' started by Blind Bruce, Jan 20, 2010.

  1. Blind Bruce

    Blind Bruce Pianissimo User

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    I have a couple of horns that have a dent just after the leadpipe. The trumpet one is in the tuning slide and the cornet has one in a similar location. How much do dents in these places affect the "playability" or tone of the instrument?
     
  2. oldlou

    oldlou Forte User

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    If these dents are in the tuning slides they will probably leak and/or cause the slides to be stuck and not adjustable. Need I say more?


    OLDLOU>>
     
  3. Blind Bruce

    Blind Bruce Pianissimo User

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    Lou, the dents are quite far from the slide areas. They both are facing the back of the bell.
     
  4. MFfan

    MFfan Fortissimo User

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    It also depends on how deep or air restrictive the dents are. If they are minor and shallow it wouldn't make any difference to the sound. If they extended in to the air way1/4 or half way , they probably would. On my King Master, I had a dent in the narrow leader pipe pretty far in , so had it taken out to get the best playability possible. DSCN5125.JPG on Flickr - Photo Sharing! As Lou said, significant dents might effect the alignment of the slide vis vis the insertion points.
     
  5. simso

    simso Pianissimo User

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    I repair instruments and take dents out, professional players bring there instruments to me when the dent tends to be greater than 1/5 the cross sectional area of the tube its in, parents tend to bring there kids instruments in during holidays (poor kids)

    This to me indicates that 20 percent depth of pipe damage = reduction in brass instruments ability to perform at its best

    That being said also the cheaper trumpets that are not set up properly with piston heights and passage alignment of valves suffer greatly with a muffled sound, these can happen as little as 3mm misalignment
     
  6. rowuk

    rowuk Moderator Staff Member

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    The leadpipe and tuning slide are the most sensitive areas of the horn. A dent will probably affect intonation the most. If you are lucky, the dent will make double G about 3 cents sharp.

    I would get it fixed. It is in a place where the repair is cheap and then you have peace of mind, and one excuse less. I like the idea of cracked notes being me and not the horn. I have more capability to work on me!
     
  7. tipo mastr

    tipo mastr New Friend

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    Quoted for truth...especially the last part. =)

    I would get it fixed if you can get it done fairly cheaply. But on the other hand, it doesn't sound like a life or not-job (death, lol) situation, so I wouldn't be too worried about it.
     
  8. elduque

    elduque New Friend

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    I know - old thread... but!

    I would have thought that the bell would be most sensitive to dents, since any damage in the area of an anti-node would dampen the horn's vibrations and thus stifle the sound. Am I way off base?

    Check out this link, it has some pretty awesome images of the bell and the position of the vibrational notes and antinodes at different frequencies (pitches). The dark areas are the nodes (no vibrational amplitude) and the lighter areas are the anti-nodes, where the most vibrational amplitude is occurring.

    Bell Vibration Study

    Cheers,
    Doug
     
  9. s.coomer

    s.coomer Forte User

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    As John Hagstrom once told me anything you do to a horn beyond the manufacturer will change the horn in one way or another. His word is good for me.
     
  10. rowuk

    rowuk Moderator Staff Member

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    Hi Doug,
    actually the bell is the least sensitive for intonation because a dent of equal size is a much smaller percentage of the total cross section there. The actual amount of pressure is also not as great the closer you get to the mouth of the horn.

    I have tuning bell instruments and changing the bell (from a Bach 229 to a 72* for instance, does not seem to affect the intonation very much at all. The sound and feedback to the player does change a lot though. When I switch leadpipes, the "sound" does not seem to change AS MUCH, but the slotting and intonation do change a great deal. There is a shop in Switzerland where they specialize in rebuilding Bach instruments. He has clips to put a horn together for testing and you can try everything conceivable - even Schilke bells.

    As to interpreting the holograms of the bell, what you are actually seeing is the energy LEAKING through the material. This is energy that gets back to the player, but not to the audience. It is also the reason that bracing on the bell is critically positioned. The brace can be the feedback loop to the leadpipe that modifies the entire response of the horn. Stamped, forged or milled braces all have much different effects on the total response.


    A similar experiment can be found here:

    http://iwk.mdw.ac.at/Forschung/pdf_...nn_Schallbecherschwingungen-von-Trompeten.pdf

    This would be much tougher to measure at the leadpipe but there is one company that I know of where the QA for leadpipes uses something similar.
    You have to register here:

    Library - Technical Papers
     

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