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Whenever, while playing, I use the second valve, the rotor sticks for a fraction of a second and then releases. When I stop playing and depress the paddle while the horn is quiet, it never sticks. The orientation of the tuba makes no difference in either case. The horn was chem cleaned in March.

Any ideas?

Is it a rotary Hirsbrunner?

Good question. When I get a Hirsbrunner (or?) it will have pistons. I was seriously tempted by a 1p this week, but haven't decided I can live with four valves on my main, full-sized CC.

But no, this is a new development on my Mackbrass 410. I just finished taking the valve apart wiping everything down, and putting it back together with plenty of oil. I didn't find any explanation, but it seems not to be doing it right now. That could mean it's resolved, or it could just be because it's got more lubricant in there than usual. We'll see.

I'm still curious about the phenomenon, though. I would have thought it would stick or not stick.

talleyrand wrote:I'm still curious about the phenomenon, though. I would have thought it would stick or not stick.

How many miles on it? Is it possible that it has developed enough play in the bearings that the air pressure is moving the rotor while being played? And the oil taking up just enough and.or lubricating ...

Lets hope your recent cleaning and oiling solved the problem.

If the leadpipe rubs a little against the lining of the case or of the gig bag, tiny fibers of fluff find their way into the tubing, where the wind pressure may put one or more of them into places where they affect the valve movement.

With my old style Blues Reunion euph bag I put a clean and tightly woven kitchen cloth over the leadpipe aperture of the YEP641.

Klaus

Yes, I reckon dirt or lint (as Klaus suggests) are likely culprits. I just can't understand why they would only make it stick when the horn is in use. Doesn't really matter. It seems to have stayed fixed for another few hours.

talleyrand wrote:Yes, I reckon dirt or lint (as Klaus suggests) are likely culprits. I just can't understand why they would only make it stick when the horn is in use. Doesn't really matter. It seems to have stayed fixed for another few hours.

Close tolerances/metal expansion from breath

I'd bet this has to do with the angle at which you are pressing the rotors being different when playing vs. not playing. Pressing with a slightly different part of the finger tip, on a slightly different part of the rotor will put different stress on different parts of the rotor. The same concept applies for pistons. Make sure your wrist, fingers, finger tips, and button positioning is consistent.

Good luck.

talleyrand wrote:... putting it back together with plenty of oil.

May be, that' the problem.
Only a half drop of not too thin oil to both bearings! No oil on the rotors, at most a breath of very thin corrosion inhibitor oil.

It has happened to me, and I believe like euphoni that it's a difference in how I handle the valve when playing, as opposed to just operating it to see if I can make it stick. I don't know that it's the angle, though. It could be, for example, that I've held it down for a length of time, and a certain force, that squashes something just a little thinner. Don't know. I doubt it's air pressure, as there isn't enough of that to be of any consequence. Anyway, the fix is just what you'd do for sticky valves in any case. My old clock springs need a lot of oil.

I believe Mark and Joe have gotten this one right.

As a trombone player what the hell do I know, but maybe it's the linkage that's sticking and not the valve.

TubaRay wrote:I believe Mark and Joe have gotten this one right.

Did I miss something - Mark and Joe explain why a valve might stick only when playing?

There is a lot of lore here, and I don't want to call a halt to the discussion. In this particular instance, it looks like the dirt-or-lint theory seems the most likely, because I just finished the third performance of the day, and the valve didn't offer to stick once. I must have wiped something away yesterday without noticing it.