B&S Rotary - something weird going on after reassembly

[Patrase]

Hi

I have just got PT6 tuba back from the repairer who did an amazing job fixing it up after a car accident damaged it. I was play testing it and noticed the 5th valve (or the first of the 5 valves) now has it's routing out of sync - in the normal non depressed position the air is going though the 5th valve circuit. I rang my repairer (he is interstate) and he said that when he was putting it back together he was confused as the order in which he stored the valves didn’t align with the numbers on the casings vs the number on the rotor. So when he put it back together he matched up the numbers, rather than the order in which he stored them (which should have been the order they came out).

So firstly should the rotors match up to the numbers on the casings? It’s a conical bore valve section so surely it should be the numbers that match up? Are the valves themselves different sizes ie do the rotors become larger along with the bore?

It’s a 1995 model if that makes any difference. Also there is no way the cam on the rotor can be rotated 90 degrees (which would fix the problem) without machine work as the bearing shaft on the rotor has a rectangular cut with a half moon section – so it can only be installed one way

My repairer was very helpful on the phone and suggested I pull it apart and play around with the rotors to get them right. Otherwise I will have to send it back to him

I am going to give it more of a play test tonight but is playing like a flat Bb tuba at the moment!

Any tips or insights?

Many Thanks

[Untersatz]

It sounds like you are pleased with the actual repair work performed on your horn, so I would have to assume the the tech. knows what he is doing. But I can't for the life of me believe that any competent repair person wouldn't play-test an instrument after a major repair, just to see "how it plays" if nothing else. Maybe Bloke, TubaTinker, Dan O. or Wade R. might chime in on whether or not they play instruments after repairs are completed? I'm guessing from what I've heard from these guys, that all of them DO play tubas after any major repair?

[bort]

Sounds like the linkage was reattached with the 5th rotor 90 degrees out of place... or something like that. When you take the back cap off of the 5th valve, what do the alignment marks on the center part look like?

Besides that, Ian is right. Take it back to him, and ask him to fix it.

[Dan Schultz]

It's certainly possible that either the rotors are mixed up or the 5th linkage is reversed.

Take it back to your tech.

I have a Chinese tuba come to the shop where the linkage was backwards FROM THE FACTORY!

[Patrase]

FIXED!,

I had a look at the cam and the factory made a mistake - it was machined 90 degrees out. So when reassembling it based on appearance it created the problem. But the factory must have filed it enough so it could be put in the correct orientation. Good news it was an easy fix. My tech said he played it for sound but not a full blow through.

I had a good play through with it fixed and checked it against a tuner - it is incredibly in tune - much better than the yamaha Neo Bb I play in band.

Hopefully I can get another 20 plus years out of it