Rotary valve vs piston valve leakage

[P@rick]

Hi all,

Are rotary valves in general leaking more than piston valves?

You play a tuba to decide how it plays/sounds/responses, but I also do the following test:
- I pull out the 1st valve slide
- I press the 1st valve
- I block the slide where the air should come out
- I blow as hard as I can (in the mouthpiece or receiver)
- I listen to air that will leak trough the valve

With my Yamaha YEB-321 (Eb) my eyes will pop out before I notice any leakage.
However with all the rotary (old) tubas I ever tested I hear a leakage. Is this normal for rotary valve tubas? The current (Alexander) I have plays great, even with this leakage.

I don’t know anyone with a new rotary valve tuba so can anyone of you enlighten me about this?

Thanks,
Patirck

[pierso20]

Interesting observation and question. I'm curious to see if someone gives an answer....err...uh....if someone actually knows the answer....you don't need to know anything to give an "answer".

[P@rick]

Interesting observation and question. I'm curious to see if someone gives an answer....err...uh....if someone actually knows the answer....you don't need to know anything to give an "answer".

Without answering my question you gave me some answers

At least I know I am not the only one not knowing this
It seems I'm not the only one who is interested in this question which makes this thread potentially useful

[Wyvern]

A tuba with good valves - be they piston, or rotary should not leak. I have not tried your test, but the plop when I pull out slides on my rotary tubas without depressing valve, tells me they seal pretty well. This even applies to my old Haag Eb which is 50+ years old. It is important that the inside of the valve is wet to create a proper seal, so this may not be the case with one you try in a store.

[Dan Schultz]

.....It is important that the inside of the valve is wet to create a proper seal, so this may not be the case with one you try in a store.

This is very true. In fact, Mirafone used to provide information with their new horns stating that the rotors would not be properly sealed until moisture (100% humidity breath) is introduced into the horn.

It's important to remember that properly operating rotary valves never touch the inside of the casing and the only points of contact are the spindles and bearings at the opposite ends of the rotor. Once those spindles wear just a tiny bit, the rotors will begin to rub the insides of the casings. With that in mind, one should assume that rotors do not fit the inside of their casings as tightly as pistons can be fit into their bores.

[P@rick]

A tuba with good valves - be they piston, or rotary should not leak. I have not tried your test, but the plop when I pull out slides on my rotary tubas without depressing valve, tells me they seal pretty well. This even applies to my old Haag Eb which is 50+ years old. It is important that the inside of the valve is wet to create a proper seal, so this may not be the case with one you try in a store.

My experience is based on rotary tubas which I owned. They are (were) wet, oiled and greased.
I also get the well known "plop" when pulling the slides. But the plop on my Yamaha was always more ploppy

With my other test the piston valves on my Yamaha seem to be very tight. This is not the case with my current and previous owned rotary valve tubas.

[NDSPTuba]

Yamaha is notorious for excessive tight valves. Not being a bad thing, except that the slightest introduction of any foreign object ( small piece of food, etc ) will create a sticking valve. During my horn playing days, I played Yamaha custom horns ( 868D and 667VS ), and they had very tight great sealing rotary valves also. I think you are noticing a yamaha thing more so than a piston vs rotary thing.

[P@rick]

.....It is important that the inside of the valve is wet to create a proper seal, so this may not be the case with one you try in a store.

This is very true. In fact, Mirafone used to provide information with their new horns stating that the rotors would not be properly sealed until moisture (100% humidity breath) is introduced into the horn.

It's important to remember that properly operating rotary valves never touch the inside of the casing and the only points of contact are the spindles and bearings at the opposite ends of the rotor. Once those spindles wear just a tiny bit, the rotors will begin to rub the insides of the casings. With that in mind, one should assume that rotors do not fit the inside of their casings as tightly as pistons can be fit into their bores.

Does this mean that (in average) an old rotary valve tuba is likely to have more leakage than an old piston valve tuba?

My Boosey & Co (1920) piston valve tuba had less leakage (almost comparable to my Yamaha) than the three rotary valve tubas I had/have (Melton rotary valve (1930? - 1950?) / Miraphone rotary valve (1980) / Alexander rotary valve (1950?-1970?)).

[P@rick]

Yamaha is notorious for excessive tight valves. Not being a bad thing, except that the slightest introduction of any foreign object ( small piece of food, etc ) will create a sticking valve. During my horn playing days, I played Yamaha custom horns ( 868D and 667VS ), and they had very tight great sealing rotary valves also. I think you are noticing a yamaha thing more so than a piston vs rotary thing.

You are right about the excessive tight valves. That's why in the band my middle name is "oiling"

[sailn2ba]

Since I've started shopping for a new tuba, I'm interested in this thread. Years ago, I had a 1921 Conn with serious leakage around the pistons . . . had them plated and relapped. They improved, but the response was never as good as my old Miraphone, and it felt to me as though the valves still leaked a bit. (That old Miraphone (rotors) still speaks like a champ.) I've also played two other piston horns of uncertain age that were OK. My current main horn is a 25 year-old Cerveny and the rotors hold pressure well when I push or pull a slide. Might be a difference between the amount of condensate required to seal the relatively short rotor and the much longer piston. I used to have to oil pistons every time I sat down, and sometimes in between . . . The rotors require a drop of oil on each end every couple of weeks, but the walls are always wet.
In fact, a slow piston is frequently dry when you look at it, and the only dry rotors I've ever noticed were on horns that had been stored for months.