This is a simple question, but I will entertain Freak Jury asides.
The YFB-621 F tuba bore size is listed as "17.5-18.5mm (0.689-0.728")."
Does that mean the rotary valve is 17.5mm and the four piston valves are 18.5mm? Or are the rotary/first three pistons 17.5mm and the fourth valve is 18.5mm?
i.e., is the piston valve section on these tubas a straight bore, or is the fourth larger?
Thanks. Idly wondering and poking around tuba specs while at work.
Blake
quick question: YFB-621 bore size
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arpthark
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LeMark
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Re: quick question: YFB-621 bore size
Look up the CC and BBb versions, without the 5th valve. If it lists and same bore specs, that answers your question
Yep, I'm Mark
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arpthark
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Re: quick question: YFB-621 bore size
Smart. The YCB-621 has a graduated bore size that is the same as the F tuba's, so it seems like the rotary + first three valves are 17.5mm and the fourth valve is 18.5mm.
Thank you for the idea, Mark!
Blake
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bloke
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Re: quick question: YFB-621 bore size
I'm about as sure as I can be (??) that the rotor is a .689" rotor, since it's before the pistons and in the mouthpipe tube.
The 4th piston is the larger bore one.
The 4th piston is the larger bore one.
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arpthark
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Re: quick question: YFB-621 bore size
Interestingly, the YBB-621 offers all four pistons in .689", while the YCB and the YFB have a graduated .689"-.728" bore. But yes, it seems like the rotor is the same size as the first three pistons.
Question answered. Thanks!
Question answered. Thanks!
Blake
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bloke
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Re: quick question: YFB-621 bore size
A reasonable explanation is that a BB-flat tuba bugle expansion is more gradual than that with F and C built on the same (for lack of a better term) "frame".
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the elephant
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Re: quick question: YFB-621 bore size
5, 1, 2, and 3 are all the same. 4th is larger and the slide will not interchange with any other valve. (I played one for twelve years.)
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- arpthark (Tue Jan 31, 2023 5:45 pm)
