Rotary valve mechanisms

[tubeast]

Hey people,

BLOKE mentioned Cerveny rotaries with adjustable clocksprings. Anyone want to comment on different kinds of these ?
Dad had an old alto-horn (3-valved, shaped like an oval baritone, cute) in his collection. Right next to the casings that held the clocksprings there were small wheel-thingies to make adjustments, and a tiny ratchet held the tension you wanted.

Our community band owns these three BBb-tubas that have a screw mechanism for this purpose. These are 30 years-old Meinl-Westons that had been sold under the brand of "Musik Hinteregger", a local instrument dealer and -maker.

[brianggilbert]

Windshieldbug would be a good authority to weigh in on this - try PMing him...