Posted by Joe S. on August 24, 1999 at 22:45:56:
In Reply to: Re: Valves posted by Gerald J. on August 24, 1999 at 20:19:34:
Don't do this. It would be a disaster. I'm not wasting paragraphs explaining why. I'm asking you to trust my judgement. Your valves can be remanufactured to better-than-new specs.
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re materials: The best pistons that I have come across are some of the old ones constructed of very thin (and lightweight) nickel-silver base metal. A lot of newer ones are made of THICKER nickel-silver, monel, or stainless steel and are "clunky", requiring stronger springs to achieve the same velocity; thus tired fingers, less agility, or both, due to excessive effort. Maybe this extra weight doesn't matter much, but I hardly ever play tuba music and spend a lot of time monkeying around with other instruments' solo literature. Virtually no instruments' solo repertories (whether very advanced tuba solos, Beethoven violin pieces, or whatever) lend themselves to a lot of physical "work" required for simply moving instruments' mechanisms.
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The pistons on an old York Eb sousa (which I converted to a Helicon) are remarkably lightweight and FAST, even though I have installed STANDARD WEIGHT BARITONE HORN SPRINGS under them. I use this instrument to play in two or three different traditional jazz bands in Memphis. I also have a very old Buescher "TrueTone" 3+1 upright baritone with "paper-thin" and very light and fast pistons. I have also noticed that the VERY OLD Conn pistons (NON-short-action) are much more lightweight and delicate than those from later vintages. King pistons, on the other hand, seem to have always been made out of fairly heavyweight material.
Maybe one reason why I have NEVER really liked any BIG rotary valve instruments is that their valves seem to move in "slow motion". Jay Bertolet has a "Big Mama" rotary, but it is a Cervany. Cervany "cheeses out" by mis-matching smaller mass .795" bore rotors in their huge .8XX" bore instruments. Jay got around this by custom grinding the air passages in his cast rotor assemblies to add back the bore size required. In doing so, he reduced the mass of his rotors even more, making them even faster! Personally, I spend a lot of time with a six-rotor B&S F. The mass on those rotors is quite low (very small centers between the bore cut-outs) and those rotors "fly" with low spring tension. The only drawback to skeletonized rotors like Jay's or those on my B&S is that when they begin to wear just a bit, you only have a quarter on an inch or air-seal area on the rotor (rather than the typical 3/8" or so) and they leak more air than typical rotors in their early stages of wear. I just oil mine A LOT, so they wear as slowly as possible.
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