not for the faint of heart...valve spring operation

Discussion in 'Trumpet Discussion' started by crowmadic, Feb 26, 2009.

  1. crowmadic

    crowmadic Mezzo Piano User

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    Oct 3, 2006
    I'll be surprised if I don't hear from rowuk on this one. I've been unhappy with the action of the valves on my vintage Olds Ambassador. Without getting too complicated let me just say that I CUT THE SPRINGS DOWN. I didn't take much off, but the difference in length made a positive difference in feel and speed. My logic said, "the longer it is the harder to compress," and these springs seemed too long. I know there are variables like diameter of wire etc. You engineers can go hog wild with this one. All I can say is it worked. This operation should not be mimiced by sensible people!

    crow
     
  2. tony h

    tony h Pianissimo User

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    Feb 21, 2008
    It was a bit risky but what was the worst thing that could have happened , a new set of springs, on the other hand, some times if you don't stick your neck out you'll never get anywhere. I'm glad it worked for you ( I just love it when a plan comes together).
     
  3. rhosch

    rhosch New Friend

    35
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    Feb 19, 2009
    (An engineer's perspective)

    Cutting down the length reduces the amount of pre-compression in the extended position. This compression generates a static force pushing up on the valve, and is the initial resistance you encounter when you first start pressing down the valve. During the valve stroke, force is increased linearly with respect to the distance you press down the valve. Say the initial compression generates 10 pounds of force (I know, way out of scale, but I like simple numbers). During the stroke of the valve you develop another 10 pounds of force. The net result is that you have a starting resistance of 10 pounds and an ending resistance of 20 pounds. If you cut down the spring, it would change that intial 10 pounds. Let's say it's now only 1 pound. But the linear force developed during stroke would be the same since you haven't altered wire type, diameter, etc. So you have a range from 1 pounds at the top to 11 pounds at the bottom of the stroke.

    So long as you don't cut the spring down so much that the valves can't hold up their own weight under gravity, or jiggle when you move the horn around, or worse yet have actual slack at the top of the stroke and are not resting in the fully extended position, then you have accomplished exactly what you wanted... reduced force for any given position of the valve.

    I'm sure it's a delicate engineering balance, but the factory setup is probably on the conservative side to make sure the valves don't jiggle too easily.
     
  4. rowuk

    rowuk Moderator Staff Member

    Age:
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    Germany
    Crow,
    You proved that there is quite a bit of leeway and overengineering in a trumpet. It does not surprise me that you were successful. Congratulations!

    Remember, less tension means that the lube job has to be better!
     
  5. max3k

    max3k Mezzo Piano User

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    Jan 7, 2007
    E=mc2 ?
     
  6. skankin'dan

    skankin'dan Pianissimo User

    186
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    Mar 14, 2007
    Winnipeg
    F= kx, actually.

    The smaller x is (length of spring), the less force that is required to compress it :lol:. Am a nerd.....
     
  7. operagost

    operagost Forte User

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    Jan 25, 2009
    Spring City, PA, USA
    Only if your fingers move slower than light speed. Otherwise, you might end up at last week's gig or something.
     
  8. tedh1951

    tedh1951 Utimate User

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    The Wide Brown Land
    Just remember "practical engineering" started before the engineering theory - I'm sure the Australian Aborigines didn't 'know' the theory of flight before they created the boomerang.

    Clever people (engineers) built stuff then "mathematicians" quantified what had been done to either explain, or reliably replicate, it. Nice job - you have discovered the 'science of gut feeling' or for the girls, 'intuition'.
     
  9. oldlips48

    oldlips48 Piano User

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    Mar 1, 2007
    Do you have to know how to make things fly in Australia? I thought everything just fell off the bottom half of the world!:lol:

    (BTW, Tom Terrific, sweet.......)
     
  10. tedh1951

    tedh1951 Utimate User

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    The Wide Brown Land
    .... fell off the bottom of the world ..... directly from Down-under to "up above" - from Oz directly to Heaven (have I ever mentioned that trumpets are played in Heaven (and Oz, BTW).

    oldlips48 - tut! tut! - familiarity with Tom Terrific - now you ARE showing your age - and, and, and, Mighty Manfred the Wonder Dog.
     

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