Switching Linkage

[aaronwelker]

Does anyone know how hard it would be to switch linkage on a St. Petersburg 202N. I received a price quote on how much parts are for this job but have no idea how hard it is to do that. Any ideas? Is this something that I can do or something I should have a repair person do? Thanks all!

[tubaforce]

Hi! Take it to a qualified tech, or find a hobby shop with a large table and a bored proprietor. A shop tha does a lot of remote control business! Only swap out one linkage at a time, and precisely measure the adjustment on each linkage as you swap them out! Remove the back cap on each rotor as you go, being sure to note the alignment(or mis-alignment) of the index marks, in both positions! Oil each bearing as you replace the cap(s)! Play test after the 1st. replacement. If you're happy with the results, proceed to the next rotor! If not, proceed to your tech and beg for mercy, promising you'll NEVER try something like that again, so help you God!

Good luck,
Al

[skeath]

I assume you're talking about upgrading the older "S" linkage to a ball-and-socket? If that is the case, yes, you can do it, if you're handy with tools. I did it on two of my tubas in years past, using parts made for radio-controlled aircraft. BTW, the results were far superior to similar linkages installed by two nationally known repair shops familiar to TubeNet readers.

SK

[bort]

I'd pay someone to do it right.

Especially for something so critical to the functionality of the instrument, I'd want to have someone else do it for me. Otherwise, as a first-timer, the replacement might not be any better than the old one I'm taking off!

[ScottM]

I did it on my Mirafone 184 many years ago and it wasn't hard. Just take your time. I removed the roller bearing on the spatula and drilled and tapped it or the screw threads on the ball and then put a nut on the end for security. You might want to get a fresh set of valve springs and really do it right. It makes it harder but you will be happy with the result. If you have a friend who is handy and has tools, it might be easier for you.
ScottM

[Alex C]

You can make the switch to ball and socket with parts from any radio controlled airplane hobby shop. If I remember correctly, a 4mm ball fit the threads for the connecting screw on a Miraphone and a Cerveny. It might be a size up or down. The rest you just have to put together yourself. I have slightly above average mechanical skills and I took me about an hour. Cost is still under $25.

Certainly, I am not a fan of the Dubro ball and socket because of their relatively short life span, 6 to 12 mos. When they failed me, it was fairly sudden and I always kept two packages in my carry bag.

If you have a tech do it, be sure and ask what ball and socket sets he will use. I had a student pay $125 years ago and the repairman used the same parts I did.

Go for it!

[Art Hovey]

I think Rick Denny has a detailed description of the procedure on his website.
DuBro makes several different sizes and types of ball-and-sockets, some more robust than others. The tiny ones that I found in local hobby shops seemed rather fragile to me, but I never managed to break one. The ones that Rick found are much more substantial, and adjustable too, but I could not find them anywhere. (Not even on the DuBro website.) But I did find some that are almost as good on Ebay.

[imperialbari]

If there is noise and your motivation is to eliminate that noise, are you certain that the noise has its origin in the linkage?

bloke points to the quality of specific knowledge upon which a decision should be taken.

Before at all approaching the option of a replacement one should be able to exactly pinpoint the culprit for noise, binding, or sticking.

Is there end play with the rotors?

Are the bottom bearings placed to allow the rotors doing a free spin?

Are the ball&socket joints adjusted correctly?

Are the double-T links moving freely?

Has the paddle axle been checked for wear?

Are all moving parts well lubricated and free of dirt (including slide grease)?

Klaus

[TUBAD83]

I did it with my first Chinese clone and it turned out great. Just take your time. Check out this link from Rick's website:

http://www.rickdenney.com/valve_linkages.htm" target="_blank" target="_blank

Follow it to the letter and you won't go wrong. Its a great way to learn more about your axe--how to break it down and put it back together.

JJ

[aaronwelker]

Thanks everyone!