rotary valve noise

[stufarris]

Hello All,

I am an amateur tuba player playing a miraphone 186. I've had the horn for about 4 years now. I took it in for first time routine maintenance (cleaning and lube) 6 months ago and since that time the first valve starts to make a metal-on-metal noise after it has been warmed up for about 15-20 minutes. The noise occurs with moderate (normal) or hard depression of the finger paddle, but not with very soft depression. No noise during the warm up or early playing before that half hour or so. The noise seems to be occurring more quickly now. A few months ago it took over 45 minutes or so for this to happen, and it happened intermittently.

The rubber bumper on top of the rotor seems no different in size, position, or appearance than the other bumpers. All screws are tight. The linkage arm from the finger paddle to the rotor has more play in it than the others, but the attaching screws are tight. I have tried many time to figure out where the noise is coming from, and guess I am just not smart enough to do it. I will probably need to take the horn back to the shop where the work was done, but they are an hour and a half away. I've posted here in the hopes that maybe I am missing something relatively simple that I just don't know about.

I have two questions about this: 1) what is causing it, and 2) is this damaging anything (should I stop playing until this is sorted out) ?

[jonesbrass]

Since the shop is so far away, why not just call them and inform them of the issue?it might be an easy fix you can do yourself, and might save you the trip. Good luck.

[imperialbari]

It is hard to add anything sensible to bloke’s list, yet I use different words:

You mention there being play in the linkage arm, which hardly is possible. The play would rather be in one or both linkages at the ends of the arm. In my experience the noise most often comes from places in the rotor/linkage set-up, where there is an unwanted play.

The short-term fix is the use of fairly heavy oil on the worn linkage, if there are no easy adjustment options.

Klaus

[stufarris]

Thank you all very much for your advice. Does this have anything to do with metal expansion (warming up)?

Stu

[Dan Schultz]

#1 cause: rotor bearing wear (usually vertical)
#2 cause: hardened (exposed to air/oil) neoprene bumpers
#3 cause: linkage wear/adjustment issues
#4 cause: loose center screw
#5 cause: compressed CORK bumpers allowing the stop arm to hit the cork plate
#6 cause: failed neoprene/silicone bumpers allowing the stop arm to hit the cork plate
#7 cause: MNS (mysterious noise syndrome)

Another cause for noise that's not so common on the Mirafones but one thing I'm seeing more and more of is sloppy fit between the stop arm and the rotor spindle. This should be a tapered fit and there should be clearance between the bottom of the stop arm and the bearing in the rotor housing. Secondly... the rotor screw should force the stop arm down onto the taper. If the screw bottoms out on the end of the spindle... the stop arm will loosen.

[imperialbari]

Thank you all very much for your advice. Does this have anything to do with metal expansion (warming up)?

Stu

Unless the rotor bearings get warmed and hence looser, I would doubt this being the cause. Rather it might be about your hand getting warmed up and taking firmer grips somewhat into the practice session.

Klaus

[Dan Schultz]

Thank you all very much for your advice. Does this have anything to do with metal expansion (warming up)?

Stu

Probably not. It's probably due to the lubricants moving out of the contact areas. How often are you lubing the spindles and linkages?

[stufarris]

Thanks again for your replies. I lube it up every 2-3 weeks. I don't think I am pressing too hard on the paddles, I actually make an conscious effort to not press to aggressively, which I've not had to do before. I think I might have to take this back to the shop after all. Am I damaging anything if I continue to play?

Stu

[The Big Ben]

I'd suggest taking it back for an adjustment. Bloke's list has eight items.Could be any one of them. I had a rotor service on a 186 I had and needed to take it back for further adjustment after about a month. The adjustment was done while I waited because, like you, I had to come some distance. There was no additional charge.