so this is happening:

[bloke]

It'll be a slide brake

Precisely...an elongated water key with no hole to cover but just some drag. I'll post a picture after I build it. It will be easy, and it won't wreck the horn like a slide expander.

[humBell]

If you play upside down, does it vibrate inwards?

Postulating that the vibration just causes it a momentary freedom from friction, and that gravity then is the force actually causing it to move...

Otherwise, also do long (loud?) tone scales in both places, and see if it is a particular frequency that it moves during?

Times i've had this issue the most are top action that hold with my left hand (and i gotta if it has a plus 1 i plan on using) where my forearm tends to push the first valve slide out, and it takes me an embarrassing number of wonky notes before i figure it out (or sometimes, it makes surprisingly little difference, which is even more disconcerting... am i lipping it back up? Or does the setting of the slide really affect the note less than it theoretically should? Is my instrument that leaky?)

[bloke]

I only took a couple of physics classes, but again I suspect that not dampening the instrument with my legs as well as transferring the vibration through a stand to a hollow wood riser acts as a vibration amplifier... similar to the effect with an acoustic guitar body... and I'm probably wrong, because I'm guessing about stuff that I've barely studied.

[Mary Ann]

Hurry, submit a patent application!!

[bloke]

Hurry, submit a patent application!!

LOL...for an elongated water key to function as a slide drag...

...It needs to be titanium, though, and have some exotic copyrighted name, such as "Kamba".

[peterbas]

.

[Mary Ann]

Go on, Peterbas. I really like physics although my grades were less than I would have liked. My definition of a college physics text is one in which the problems at the end of the chapter have absolutely nothing to do with the material presented in the chapter. (I still got As because apparently everybody else understood it less than I did.)

[bloke]

I only took a couple of physics classes, but again I suspect that not dampening the instrument with my legs as well as transferring the vibration through a stand to a hollow wood riser acts as a vibration amplifier... similar to the effect with an acoustic guitar body... and I'm probably wrong, because I'm guessing about stuff that I've barely studied.

Yep, wrong.

excellent...and thank-you so much...

...so (as an expert with THE ANSWER - as my premise is - hands-down - wrong) THE REASON why my slide slips out ONLY when using a tuba stand and sitting on a hollow/low-mass riser RATHER THAN with the tuba resting on my legs and seated on a solid floor (and having nothing to do with "bloke needs to be called out" and having everything to do with the proper application of physics and the Scientific Method) IS

___________________________________________________________________________________________________________________________________________.

[peterbas]

.

[peterbas]

.

[bloke]

...so (since you don't know) you're only bullshitting me, to support the "bloke is stupid, because he and I view sociological and political issues very differently" narrative.

NO...I'm NOT claiming that my premise(s - combinations thereof) is/are correct...nor that any of those changes are the cause or causes.

...but to go to the trouble to claim that any/all of them are automatically wrong (particularly as you claim scientific/technical knowledge) "just because" is pretty damn tedious.

>>> I believe (??) that I may (??) have eliminated temperature, because I've been heating up the bloke tuba shack (former master bedroom) all the way up into the 70's (around 22c. - about the same as when it was falling out/slipping out in the hall, as there is a posted thermometer - union requirement - on stage). At the hall (when it WAS slipping) I tried lamp oil vs. something about the consistency of "key oil" (I'm simply not contaminating my rotors via migration of anything thicker than that), and it continued to slip just as quickly.

ALL of that having been reported, (again) I was really involved in some fairly consistent "loud-ass" playing at the hall...and that's (well...) something that I only do on a limited basis at home...but with no real "pressure" on the air column (or is there?) I just don't "get" the possibility of (re: mere mortal) "blowing the slide out".

[peterbas]

.

[bloke]

I have posted two things to try out but no, you are once again back whining about "Bloke is stupid", being something I never said.

Once again my threshold of Bloke-isme has been greatly surpassed.
See y'all in a couple of months

As (you present yourself as) an "engineer/scientist", you know as well as I do that "trial and error" (ref: "I have posted two things to try out") and "science/engineering" (ie. cause/effect) are not overlapping realms - just as are not biases (against theories or individual personalities).

ex: Someone can "fool around with" a mouthpiece shape or bugle taper until it works pretty well, but have NO EARTHLY IDEA regarding the physical causes of WHY those things work pretty well. (That is ME - fwiw.)

Scientific Method-wise, I'm not asking a Step 2 question, I'm asking a Step 5 question. I simple "I don't know" or "no post" would suffice.

Further, to label a group of premises as "wrong" without testing (nor without stating/explaining/proving what is "right") defines you (in my book) as a troll (and as a troll, I can recognize trolls).

I've already solved the damn problem (an extremely ergonomic "slide brake")...but am ONLY wondering about the friggin' CAUSE.

...so you're now saying that (not enjoying being "called out") you're going to cry, and run home for a few weeks...but (after getting over it) will come back out to "play" some more...??

bloke "here - with bated breath"

[Mary Ann]

Dis gonna get locked.

[bloke]

I already got my answer - and from the most renowned research scientist/engineer/physicist/machinist on the board:

I dunno, but your hypotheses are wrong.

[matt g]

I’ll take a swag as a mathematician…

If your slide is staying out at home when PhatBlaster is cuddled in your lap, but sliding out when on stage and seated on a tuber stand (is it portable???), then I’d reckon that it’s other instruments and stuff getting the stage itself to resonate a bit that might get some sympathetic vibrations moving up the stand and into the tuba. Just enough to get the slide to comply with 9.8ms-2.

And not that it’s important, but have you tried something like that thick old Selmer pink cork grease/slide lube on the leg opposite the rotor only? Maybe that stuff is viscous enough to hold.

[Mary Ann]

That pink stuff is genius at finding valves. Much experience here with that. I like his friction device, also the idea of just wedging a rag should one be found to fit. "Whatever." Now tell me how to tip my tuba out at an extreme angle so I can get my chops solid on the cup.

[matt g]

I used to cut the pink stuff with valve oil on my old 188 and never had issues. YMMV. That’s why I mentioned putting it on the opposite leg, as getting it to transverse that distance would require a bit extra work.

[bloke]

OK...
At tonight's rehearsal at the next church, it was just sitting on my legs on a really solid floor, and it moved.

...and this was some more BTTW playing...
This church even hired a scream trumpet player.. one of those guys with messy long hair who plays out of the side of his mouth...

... so maybe it does have something to do with playing loud as hell and a lot of friggin' air going past the main slide.

After all, the thing ain't that big by the time it reaches there... Maybe 24 or 25 mm diameter...??

============

The parking lot attendant (raining hard) was an extremely nice man who found me a parking place in a lot that was jam-packed with cars with no places left. There were two cars parked temporarily, he went inside, found those people, and told them to finish up their business and leave - so that I could have the one place of those two that was allowed.
After everyone was parked and everything was settled, he was able to go inside, sit and listen to the rehearsal. He was very kind to me on the way out and complimented the tuba playing.

[Mary Ann]

And I have found that on my new-to-me CC the first valve slide will not stay put where I want it. Clearly has been massaged so as to be easily movable for the slide-pulling crowd. I have some custom sticky-goo that the local tuba repair guy gave me, that I put on the necessary parts of it so it doesn't slide down and make all first valve notes sharp. And if that doesn't work I'll put a rubber band around the tube in the appropriate place.
I think you're just blowing too hard, bloke. Scaring the hell out of the tuba so it drops its pants.