What's it for?

Discussion in 'Trumpet Discussion' started by crowmadic, Nov 15, 2007.

  1. Vulgano Brother

    Vulgano Brother Moderator Staff Member

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    The screw holds the valve guide onto the valve. Some valve guides are split, allowing them to be splayed over time for a better fit, or one can unscrew the old guide and put a new one in. Good luck finding replacement guides, though. A fun book to have is the Eric Brand Repair Manual, which shows how to do all kinds of fun stuff, and repair/ruin an instrument by ourselves.
     
  2. crowmadic

    crowmadic Mezzo Piano User

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    Brekelefuw, Do you know what the screw is for?
     
  3. confuoco

    confuoco Pianissimo User

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    Nov 11, 2007
    Got any pictures of what you are describing?
     
  4. oldlou

    oldlou Forte User

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    This is often the case with the second valve slide tubing. It is easily bent by impact or a too tight case, or some fool kid cramming music charts or books into a case that was made to be a nice comfortable fit for the horn. In 'most' cases, this results in the solder joint connecting the tubing to the casing is slightly stretched, allowing the tubing to very slightly impinge into the casing interior. Most techies can cure the problem in about 30 seconds.


    OLDLOU>>
     
  5. crowmadic

    crowmadic Mezzo Piano User

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    It came to me in a dream last night. The screw I'm talking about does keep the valve guide in the track of the valve stem as Vulgano Brother mentioned. It also fits into the slot inside the casing that stops the valve from spinning. Could that screw also be influential in angling the valve, and thereby be a source of correction for valves that drag when all other potential causes are elliminated?.........crow
     
    Last edited: Nov 19, 2007
  6. oldlou

    oldlou Forte User

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    If the guide key is the original in that piston it is highly doubtful that the guide key would be in any way contributory to the piston being pushed to one side in the casing. It might be worn to the point that it no longer perfectly lines the passages in the valve piston with the holes for the loops.


    The screw only holds the guide key firmly into its machined slot. This is one of those screws that should not be messed with, except by a technician in the process of replacing a worn guide key.


    OLDLOU>>
     
  7. oldlou

    oldlou Forte User

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    I just now got back from meeting Dave at The Big Boy Restaurant in Wayland,Mi., about midpoint between his home in Kalamazoo and mine in Grand Rapids. I inspected the subject valve and discovered that it had been dropped at some time prior to his ownership, slightly collapsing the bottom skirt of the piston. This caused the new dent to swell out the skirt very slightly on either side of the dent, thus impinging upon the casing wall. I dressed the high spots on the skirt with a fine cut jewelers file and the valve now runs free in the casing. I told him to acquire some ultra fine 1500-2500 auto body wet or dry sanding paper and to finish the work by polishing the file marks away, just on the edge of the skirt making it very slightly conical at that very bottom edge. The problem is solved without removing any material from the sealing portion of the piston or casing.


    I forgot to instruct Dave to clean the piston VERY completely before reinserting the piston into the casing, to make certain that there is no remaining abrasives or metal sandings to rapidly wear the piston and casing. I hope that you read this, Dave.

    OLDLOU>>
     
    Last edited: Nov 19, 2007
  8. MFfan

    MFfan Fortissimo User

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    I met with Lou today. He could see immediately that the bottom edge of the piston was somewhat damaged and though someone must have dropped the piston at some time. He had some jewelers' files with him and filed down the edge of the base down so it works nearly perfectly and rarely gets hung up. I am supposed to get some 1500-2500 wet dry sandpaper as used by body shop to smooth off the filed area, being careful not to touch the piston sides. I played the horn a lot tonite in the swing band I play in and didn't have much trouble. Dave:-)
     

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