As I stated above: I won't resurrect this old thread unless I have something further to share.
Today I fixed a LOT of niggling pitch issues all over the horn by shortening the 2nd slide. I had chopped the second slide and added a much more robust pull ring that was larger, longer, and had a more solid flange to the slide crook. However, I was too busy to remove the outer tubes (and the brace to the 3rd slide) to shorten and reinstall them.
Today I did that, and I also worked on the alignment of the upper 3rd slide, which looked a little crooked despite having an excellent, smooth pull. It was a tiny bit off, but it looked wonky because the two tubes had brace flanges at opposite ends that stuck out on opposing faces of the tubes, so they genuinely looked very far out of alignment. After measuring several times and studying some photos I decided to get out the granite surface plate, and the adjustable parallels, and line up the slide itself a little better. (It *was* off, being nicely parallel but out of the plane by about a quarter of a millimeter. Once I was happier with the slide I then was able to heat the short tube's joint with the piston casing as well as the adjustable brace until I got that satisfying *tink* that happens when the pressure is released from a slightly bound-up joint.
It is amazing to me every time I correct a too-long slide that it affects so much of the horn's scale. I have been happily playing stuff for the last two hours with no lipping or <ahem> wincing. What a fun tuba!
Finally, The new 2nd slide pull ring I made earlier ended up with the long rod slightly crooked. Once I corrected the subtle slide alignment issue, unskewed the slightly askew rod, and then shortened the slide by 10mm the visual difference is subtle but real. And I really need to get a long break from work to take this horn apart and fully clean up all the exposed and ugly work. (1st week of June?)
Further, there was a definite leak somewhere near the 2nd valve. It seemed to leak on the open horn but was worse with the 2nd or 1st down. I suspect a cracked knuckle between the two pistons. Anyway, the heating with the torch seems to have blocked up whatever it was. I cannot explain what I did, which was nothing intentional, to fix this, but it is a big difference. One of the outer tubes was leaking at the valve case, I think, and that was the major issue, but something else changed in the tone and the whole horn plays with a better focus. I can't explain it, but I screwed up in reverse, I guess. Whatever — I'll happily take it.
Before…
After…
Slide and brace off…
Cutting the outer tubes…
Slide cut…
This looks better…