causes of rotors clicking - and misdiagnoses

[toobagrowl]

A couple months ago, I worked on an elderly gentleman's tuba. It was a Chinese copy of the B&S 'Sonora' BBb tuba. I believe the man bought the tuba cheap from a now-defunct west coast music store. The only engraving on the tuba was "Infinity" on the bell.
The tuba itself actually played very well; nice deep sound, in tune, good response. But the rotor section was terribly clanky and not as fast & smooth as good German or even Czech rotor sets.
After smoothing out the bell creases, I looked over at the rotor section. Oiling both top & bottom bearings as well as the linkage didn't do a whole lot. I finally noticed some 'slop' or 'play' in the ball-&-socket joints as well as the T-joints near the paddles. Oiled those. I had asked him why he had athletic fiber tape around the top screws that hold the stop arms in place. He told me because they kept coming loose! So I took the top screws off, cleaned off the tape and proceeded to take the stop arms off. There was a LOT of 'slop' between where the stop arms and top rotor stems fit together. You could 'wobble' the parts with your fingers. Very loose tolerances; they were fabricated that way. The tuba was only 4-5 years old. The only thing I could then do was use GREASE on those parts and screw them back together. I also used grease on the ball-&-socket joints as there was a lot of 'slop' there too. All of this improved the linkage........a little But you can't really do much when the parts are fabricated with very loose tolerances

One thing I wanna add to this is that when I am doing rotor maintenance on my own M-W CC, I have to make sure the back bearing PLATES are on just right. This is if I actually removed the entire rotor from the casing.
If not, then there is sometimes clanking or the rotor won't move. I have to tap the back plates in alignment "just right" with a plastic/rubber mallet.

[Paul Maybery]

There are several things that I did not see covered here which do make a very real difference with regard to the clicking sound. None of these were obvious and took a lot of investigation to discover.

1. This seems ridiculous but. The neoprene bumpers often get a tear in them from the stop arm continually hitting them. It is hardly noticable particularly with the black neoprene. That little tear causes a click like sound. Replace the bumper. Care when installing the new one not to tear it as you push it into place.

2. Similar to using a torque wrench when tightening the bolts on the head of an automobile engine, a certain amount of torgue is needed with the screws that hold down the crescent shaped plate that holds the bumpers.
Sometimes "just tight" is not tight enough. Same can be the case with any screw in conjunction with the valve.
Care to be taken to use the right sized screwdriver and to monitor the tightness very carefully. Over tight of course can strip the threads.

3. The collar screws on the push rods also work loose from time to time and need to be torqued back.

I have done this on all of my rotary valves and "voila" no clicks. They are disturbingly fast and quiet.

[pjv]

I have an old 163 Alex (possibly '20's) that I paid $500 for, plays amazingly in tune and has a lovely sound all around. It's been beaten up really bad though (silver solder work on a mouthpipe crack, lots of dents, etc). Being a beat-up 4/4 BBb with an older 42.5cm bell flair (about 16 3/4") and (get this) a nickel-plated red brass tuba means I'm not really gung-ho about restoring it.
The valves are noisy, the bearing plates are loose and one is partially broken-off.

So as a temporary fix I use thicker oil on everything that makes noise and put perinet valve cap felts on the bearing plate so that bottom cap itself pushes the valve into place (reducing the vertical tolerance).

This all works in a pinch and at least makes it possible to hear how the tuba responds.

Who knows, if I ever want a 4/4 tuba I might have Alexander do whatever need to be done. But then I'd want 5 valves. Not an easy task considering the valve entrance and exit is at the typical older style 45 degree angle.

[pjv]

Agreed, but until now I haven't found any repairmen I trust to do the work. The tuba is worth it. The nickel plate does make it harder to work on I imagine. Fortunately theres only one deep dent that might be a crack danger.

If I start on it I want it done well and I want it my way, which means a 5th valve. That means a new mouthpipe (what it probably needed anyway).

And if I'm going to do THAT then I REALLY prefer a different bend in the pipe. I absolutely HATE traditional German-style mouthpipes that go up before they enter the valves because of all the build up in condensation which just sits there (or, if I'm lucky, ends up on my shirt). So it'd have to be custom bent. The mpc receiver when then be positioned higher up on the bell but this is a win/win for me. The tuba can then probably rest on the chair (not that this tuba is heavy, quite the opposite), positioning the valves lower down which is nicer for the wrist in my experience.

Blah-blah. So, yeah, I might take it to Alexander. They're unfortunately very conservative but they will have the correct mouthpipe.
Sorry for the long off-topic post.