Rotary valve - back cap adjustment

[Tortuba]

On Friday, I picked up my horn after being cleaned by a local technician. He pulled the valves and gave them a well deserved cleaning.

However...

While practicing this morning I noticed the 4th valve back cap was loose. When I tightened it (finger tight only) the valve binds and will not move. Back off the cap and it moves freely. This did not happen prior to the cleaning. I'm not comfortable playing the horn with a sloppy fitting valve cap.

I did take the cap off and applied some oil. but this did not resolvable the problem.

I'm speculating that it has something to do with the adjustment on the valve plate and the way is was re-assembled after cleaning.

The technician is not available until Monday and i will give him a call then. In the meantime, I thought that one of the technicians on this board might offer a simple solution.

Thanks

[tubaforce]

Hi!
Can you see any numbers engraved on the caps? My Cerveney has each cap numbered(hard too see)! If that doesn't work, use masking tape and mark each cap A,B,C,D, etc...then start pairing the caps with rotors. Be carefull you align the threads each time you do this, as you don't want any cross threading! Then write down how each cap worked(or didn't) with each rotor.
A 1 worked
2 didn't work
3 worked
4didn't work

Continue until you have tried all possible combinations, and you should at least 1 cap that works on each rotor. Once you are satisfied with cap placement, remove them one at a time, and scribe/scratch appropriate rotor # NEATLY on the inside of the cap. You would be surprised at how many otherwise excellent techs assume that the caps are universal, I suppose because a lot of times they are!

I hope this helps!
Al

[Matt Walters]

The rotor valve binding with the cap screwed all the way happens with some horns. It is usually the nipple inside the center of the cap that is hitting the actual rotor shaft. Miraphone addresses that issue with an adjustable screw-in piece in the middle of the valve cap.
1) If you have a Miraphone with that, the caps were mixed up and need to be readjusted.
2) If you have a different tuba that does not have the adjuster screw, then try switching the caps.

If the bottom bearing plate looks well seated and the valve works great, and every valve cap causes the rotor to bind when the cap is on tight, then likley the caps are missing some crud or something that before was not letting them screw down all the way. In which case:
1) Grind down some of the nipple inside the center of the valve cap. (risky)
2) Make a very thin shim that will around the bottom bearing area so that the valve cap hits the shim and the broad area of the bottom bearing plate before it hits the rotor shaft. I use the thin green King sousaphone top cap felt for such an occasion.

Plus, what Bloke just said.

[tubaforce]

Hi!
I had the rotors aligned on my Tuba last year, and had that same problem with my Cerveney. A sharp eyed apprentice at the shop pointed out that my caps were indeed numbered, no kidding! I could see them with my glasses! I merely placed them on their correponding rotors, and all 5 rotors were fine!

Al

[Tortuba]

The Horn is a Sonora which is a PT1 stencil.

I checked the cap numbers and all the caps are on the correct valves.

[tubaforce]

OK!
Now you have an issue best addressed in person by your tech! I'm wondering now about the qualifications of that tech, as he/she surely left the cap loose in order to allow the valve to operate! This is why I hate having a starnge tech work on my axes! I was out of state when I needed an emergency alignment.

Al

[TUBAD83]

Have had the same problem--make sure the bottom plate is completely flush and fitting properly and clean/lightly oil the the cap.

You should complain about this matter to the tech that worked on your horn (a competent tech would have addressed this before returning your axe to you) and find a replacement.

This is precisely why every tubist should learn basic repair of his/her axe---for when the time comes when (not if) you have to do an emergency repair.

JJ

[Dan Schultz]

Your tech should know better. Take it back to him. If the horn worked fine before and he says it can't be resolved.... take it to someone else.

[Tom]

I'd put my money on the bearing plate for the valve in question not being reinstalled correctly after the valves were taken apart during servicing.

I can't imagine how this goes unnoticed to the tech when the valve caps are reinstalled. They know darn well that they are not supposed to be loose and that when reasonably finger tight the valves are not supposed to bind.

[tubaforce]

HI!
If your tech doesn't, or can't take care of it for free Monday, I would insist He/She pay for someone who CAN do so! TUBAD83 is right about learning emergency repair techiques, and I for one will be watching my tech closely the next time he works on my valves. Thank god I don't have string actuated rotors! LOL!

Al

[Kevin Hendrick]

Thank god I don't have string actuated rotors! LOL!

LOL indeed -- re-stringing a rotor isn't that hard to do. Takes maybe five minutes a rotor (usually less), and only has to be done every 6 months to 2 years (my experience -- YMMV).

[Tortuba]

Lots of good replies.

How do I "eye-ball" the bearing plate to determine if it has been re-installed correctly? What should I look for?

Thanks

[Tortuba]

What's that old adage about the simplest solution being the best?

I switched the back caps between the third and fourth valves and "voila" the situation is resolved...although I'm not pleased it happened in the first place.

Thanks for all the input.

[TUBAD83]

Lots of good replies.

How do I "eye-ball" the bearing plate to determine if it has been re-installed correctly? What should I look for?

Thanks

You really cannot visually inspect, as - particularly with very precisely-fit rotary valves - even .001" - .002" tilt can cause a bind. The vast majority of the time (nearly all the time) bearing plates are supposed to line up properly when "driven home". A no-brainer way to do this (assuming one isn't clumsy and won't hit unintended parts of the instrument) is to remove the threaded cap, set a junker trombone mouthpiece on the bearing plate, and rap on the shank of the trombone mouthpiece with a rawhide mallet or wooden stick.

Joe--thanks for the tip. Will definitely add it to my toolkit--I had been using a rawhide mallet and a wooden dowel to tap around the plate until it was properly seated.

Tortuba, you still should have a word or two with the tech since you had to correct HIS screw-up.

JJ

[Daniel C. Oberloh]

Oh the stories we could share.

Daniel C. Oberloh
Oberloh Woodwind and Brass Works
http://www.oberloh.com" target="_blank