so this is happening:

[bloke]

If you read a bunch of my crap that I post here, you know that I have a really large Miraphone rotary B flat, I shortened the main slide without shortening the tubes and without taking any metal off the tubes, but I really aligned them nicely - even better than Miraphone had aligned them.

Even though I'm not a fan of tuba playing stands, I'm trying one out again... at home with the stand and with the temperature around 68° ( though I'm suspecting that the stand is actually more of a factor than the temperature) nothing happens,
Being that I'm up on a riser (for this concert) my main slide is now sliding out, actually fell out once, early on, and particularly when I play as loud as hell... and for an extended period of time - such as extended time during some pops piece.

Knowing barely a little bit about physics, I don't see how I could possibly "blowing it out". Without my body absorbing vibration (using the stand) with the riser not absorbing nearly as much vibration as the floor in my house, I suspect it's being vibrated out.

Not really interested in screwing up the alignment of this slide - and also interested in continuing to be able to pull it quickly and reinsert it quickly - now I'm trying to imagine some Little device that is non-metallic and barely drags along the outside slide tube, just enough to discourage movement, but which I can defeat just by pulling on the slide... probably either held down with a spring, or screw adjusted.
----
... I hope I didn't screw up too many words or sentences.. this is a new phone, a new phone platform, and I couldn't even get it to go to this site for over a day.

[bort2.0]

String?

[Mary Ann]

You will hate me but put in a Joy key so you don't have to dump water. Mine worked perfectly on the NStar, the only problem being I needed a drip rag.

[MikeMason]

Why do you need to pull it all the way out to dump? One of the things I’m enjoying about a rotor valve horn is all the water easily comes out in one place, the main slide water key. I’ve used Velcro with good success on my wiseman that had same loose mts problem

[bloke]

You will hate me but put in a Joy key so you don't have to dump water. Mine worked perfectly on the NStar, the only problem being I needed a drip rag.

I bought some packing tape at the dollar store last night and I'm using the water key.
Being huge, this tuba generates a tremendous amount of water, the water key works okay, but dumping every two or three minutes (pops concerts...constant strong playing) is tablespoonS.

I'm probably going to braze the current hole shut, redrill off to the side - so the bottom of the water key is in playing position, and drill a considerably larger hole with rounded inside edges - much like undercut woodwind tone holes - so the water rolls out really easily.

... but I still think I'm going to also install some nylon dragging device.

I'm more fascinated by how and when this is happening than the solution.

[kingrob76]

Please feel to correct me if I'm wrong, but, most materials we apply to slides seem to change viscosity depending on the temperature. A warmer room / slide could certainly be enough to allow the slide to move with vibrations. If the slide moves very free in your house it's going to move even more freely in a warm room. My 1291 tuning slide regularly bailed out if I set it 1/4" from the end in warmer conditions (which is when I tended to need the extra slide). My Wessex had the same issue until I got the longer tuning slide. A heavier lubricant might be enough to keep it in place.

[bloke]

sure...all that...but it never even hinted at moving at home - and not on any warm days at home.

[Mary Ann]

It's the CIA.

[bloke]

I tried to link a performance of "If he would need the F.B.I."...but don't know how to do it with this Android phone.

[UncleBeer]

Slide expander. I bet you've got one.

[bloke]

Slide expander. I bet you've got one.

would rather not.

It's not loose. The only problem is that it is perfect.
(Individual pairs of tubes do not rock, and are the same as oem.)

[LittleJon1]

Slide expander. I bet you've got one.

I had this exact problem on a new Miraphone 289 a few years back . I asked for advice on the other forum . My mts would move while in its gig bag while laying on its side . Very weird . I ended up having the tubes expanded. There is no evidence that any repairs were ever done , except that the slide doesn’t migrate any more .

[bloke]

I just don't like messing up stuff that isn't broken (and which is actually just a little bit too good).
It's not leaky...

[peterbas]

.

[hrender]

Total amateur suggestion: stickier grease? Most MTS grease is stickier than I like, but it might fix this.

[bloke]

yeah...
I had a friend with a perfectly aligned courtois trombone main tuning slide which would move, and thicker grease or thinner grease didn't make any difference.. plus, this slide is very close to one of the rotors - and I don't really want to gum up any rotors.

pretty sure I'm going to use some lever style thing that looks a lot like a water key which drags on the outside slide tube - and that I'll be able to push it to release the drag and pull the slide right out. It will be convenient.

[Mary Ann]

ah, a friction-adding device. Cool.

[hrender]

sorry, double post

[hrender]

yeah...
I had a friend with a perfectly aligned courtois trombone main tuning slide which would move, and thicker grease or thinner grease didn't make any difference.. plus, this slide is very close to one of the rotors - and I don't really want to gum up any rotors.

pretty sure I'm going to use some lever style thing that looks a lot like a water key which drags on the outside slide tube - and that I'll be able to push it to release the drag and pull the slide right out. It will be convenient.

Yeah, silicone pad in place of the cork, that would work so long as it's kept clean.

[jtm]

It'll be a slide brake