Play in rotary valve double hinge mechanism

[gocsick]

I just became the new owner of a early 1970s MW 20 with the original S linkages. After a good oiling valves 2,3, and 4 are smooth, quiet, and fast with good alignment and no play anywhere. Valve 1 on the other hand has a loud clank and rattle due to excess play on both sides of the double hinge... meaning it rocks side to side both where it attaches to the paddle and also where it attaches to the S link. Other than that the horn is in really great shape mechanically. No vertical play in the bearings, only very minor dents, and no sign of red rot.

What is the correct fix? It seems to me that you would have to drill out the rivets, then ream the holes to a larger size and then seat new larger rivets.

Going to take to my repair shop next week. Just looking for information so I know what's what. I would prefer to keep the S links rather than replace.

As a side note... this thing has the longest 3rd valve pull on any tuba I've ever played. Enough that the pedal B/Cb can actually be played in tune without too much effort to lip down.

[TheBerlinerTuba]

Hi Gocsick,

unless the hinge pins are completely toast, usually one can swedge them with this type of pliers to remove excess play.

https://www.ferreestoolsinc.com/product ... ing-pliers

Technically when you replace this type of old linkage, one would completely discard the rivets and T-joints, and remachine everything for a nice snug fit.
Sometimes, the pins are actually tight enough, but the theads have unscrewed themselves a bit and the linkage starts to clank. Its not so common, but also something to check.

Hope that helps and congrats on your new old tuba!

[bloke]

The metal bearings that are embedded in the ends of the 50 year old model 20 S arms with the hole for the screw at the stop arm are probably going to be rattling on those screws. Drilling them out and replacing them with the Miraphone s arm nylon bushings (which need to be melted in with heat) will make you smile, as far as noise reduction is concerned. They are very inexpensive. I'm not going to go in to how to install them. If the person that you have do it for you doesn't know how, they're obviously the wrong person aren't they?

the wear noise in the universal "T"- joints in S-arm linkage:

Different people experience different issues, but the only issue I've ever found with those is end-play, and (so far, in my experience) no steel-rod-to-hinge-tubing fit looseness...

...so the only remedy that I've ever found that needed to be done (to eliminate T-joint clicking) is to use a larger-size "dent hammer's" smaller head and tap (carefully - and supported by an anvil or a vice's anvil surface) on the ends of those steel screws JUST TO THE POINT that they continue to rotate freely YET the up-down/left-right clicking (due to end-play) is eliminated. It's easy to go too far, and then have to spend a great deal of time "freeing them back up"...so a few taps...check / a few more taps...check...etc.

S-arm (outside/wire spring) linkage is very elegant, and relatively easy to (so-called) rebuild/re-silence. It's a damn shame to tear it off an instrument (reducing the level of visual elegance of an instrument) and replace it with sealed bearing linkage (as the sealed bearings ALSO wear, eventually click, and are NOT rebuildable)...with (again) the only "techy" upgrade being replacing the steel or bronze warbled out (colloquial for "worn/ovaled/too large") embedded bushings with the (c. a dollar-each) Miraphone nylon bushings.

[bloke]

As I recall, I was the one to suggest to Brett that he take a hacksaw and a file and get rid of that excess weight and bore constriction on those rotax rotors, but he decided to have someone else do it. Once you've cut that crap off of those rotors, all you have to do is make sure that no jagged surfaces are exposed to the casing, and make concentric sanding marks with really fine sandpaper - probably ending up with about 1000 or maybe 1200 or 1500 along those cuts. Just be careful and don't slip. Once you chopped off the majority of what needs to disappear, I'd probably use a really rough file that's probably sort of halfway between a file and a rasp to file the corners of those cuts into curves before doing the smoothing. A regular file will take too long, and putting them against a grinder is way too risky. As long as all the surfaces that articulate the casing are smooth - and particularly if you sand concentric with super fine sandpaper, they should just drop right back in.

People seem to get really frightened when thinking about altering valves. There are only a few rules: don't bend them, don't nick up surfaces that matter, and don't slip. If you hire someone else, they're going to follow all the same rules, and they probably don't do stuff like that (chopping stuff off of rotary valves) much more often than you do.

There are actually a couple of places in the top and bottom of rotors where solid heavy material can also be taken away, but I don't know of any safe fixtures that could hold the rotors while such operations were being carried out, so I never recommend or try that myself.

I still believe that the hollow rotary valves that came out several decades ago were pretty amazing. Didn't those appear on Czechoslovakian instruments?