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Terence

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  1. OK then, nobody likes my question. As it happens I found the answer experimentally.
  2. In case it makes any difference, here are the relevant dimensions of the trombone in question:- What I have a problem with is a pair of 8mm ID, thin wall brass tubes, each of which of has a brass sleeve at one end, 50 mm long and firmly attached to it. There is such a sleeve on each of them. The OD of each of these collars is 12mm and they each act as a slide for another thin wall brass tube with ID of 12.5mm. The two larger tubes are meant to slide over the collars as a pair, ie both at the same time but as the outer tubes are pushed towards one extreme the assembly begins to judder, despite
  3. I forgot to mention that the only part of the tubes that are in contact with each other are two brass sleeves, 50mm long, mounted on the fully open ends of the inner tubes, something like pistons. Air blown in at the AIR IN end goes down the inner tube and cannot get back up the first outer tube because of these pistons. It goes instead down the protruding lower end of the outer tube, round the bend to the second outer tube, ie back to the other piston, from where it goes up the second inner tube. All trombones are made this way.
  4. I have a trombone whose slides vibrate at 8 Hz at they approach the fully open position whilst moving. They are not supposed to do this. Let me make it clear: they are well lubricated and are not being blown at the time and the vibration consumes all four brass tubes whereas in its normal mode the vibrations are sound vibrations and they are at much higher frequencies. The vibration that concerns me is more of a judder. The pair of inner tubes is firmly held at the AIR IN end but is floppy at the end that judders, while at the fully open position the outer tubes are held firmly at the required
  5. I have a problem with a pair of 8mm ID, thin wall brass tubes, one of which has a brass collar at one end, 50 mm long and firmly attached to it. The OD of this collar is 12mm and it acts as a slide for another pair of thin wall brass tubes with IDs of 12.5mm. The two larger tubes are meant to slide over the collars as a pair, ie both at the same time but as the two pairs of tube are pushed together the assembly begins to judder, despite adequate lubrication and despite everything being in line. Could anyone suggest a possible reason please?
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