Advantages/Disadvanteges to Venting Rotary Valves

windshieldbug · Post by **windshieldbug** » Thu Apr 05, 2007 7:10 pm

You vent the valves to allow playing of the horn while pushing/pulling the valve slides- without the "pop" or "whoosh" effect of air that you get if they're not.

My 30 year-old 184 was built with all of the valves vented... and I've never encountered any problems.

(It turns out that I posted this at the same time as the pachyderm was finishing his... )

Wyvern · Post by **Wyvern** » Thu Apr 05, 2007 7:31 pm

The main disadvantage I have found (with the vented 2nd valve on my Neptune) is that air leaks when trying to trill spoiling the sound. When I played Mahler 6 which has a couple of trills, I taped over the hole.

I would be interested in how others with vented valves get around this problem with trills.

Bob Mosso · Post by **Bob Mosso** » Thu Apr 05, 2007 7:40 pm

Trilling problems may be caused by the vent hole being in the wrong location.

As soon as you partially depress the valve, the vent hole should be covered by the valve casing, and then act as if it didn't exist.

If you must press the valve nearly all the way before the vent hole is blocked by the casing, then I would understand trilling difficulty.

edit: Sorry my description was for piston venting. For rotary valves the valve blocks the hole in the casing as soon as you partially depress the lever.

Chuck(G) · Post by **Chuck(G)** » Thu Apr 05, 2007 7:53 pm

Does any manufacturer ship its piston-valved tubas already vented?

cjk · Post by **cjk** » Thu Apr 05, 2007 10:19 pm

Willsons have a vented 1st.

Tubaryan12 · Post by **Tubaryan12** » Thu Apr 05, 2007 10:31 pm

On a side note, I get a slight pop of the valves when I press the valves after a rest. I'm guessing venting will stop this from happening. My question is: Is there something else wrong with the horn that makes this happen or is this normal?

Chuck(G) · Post by **Chuck(G)** » Thu Apr 05, 2007 10:38 pm

cjk wrote:Willsons have a vented 1st.

They do? Must be something they started doing lately. My 3400 doesn't have any vented valves.

windshieldbug · Post by **windshieldbug** » Thu Apr 05, 2007 10:41 pm

Tubaryan12 wrote:On a side note, I get a slight pop of the valves when I press the valves after a rest. I'm guessing venting will stop this from happening. My question is: Is there something else wrong with the horn that makes this happen or is this normal?

If you have a slant-rotor, you should ONLY be using the main tuning slide (unless you are VERY limber). I have NEVER experienced a "popping" from mine in 30 years of use, but I can't imagine anything that would cause this besides a tiny temperature difference, and even then, so slight that it would not cause any adverse effects.

That's one reason that I love the slant-rotor design so much...

Tubaryan12 · Post by **Tubaryan12** » Thu Apr 05, 2007 10:45 pm

windshieldbug wrote:
Tubaryan12 wrote:On a side note, I get a slight pop of the valves when I press the valves after a rest. I'm guessing venting will stop this from happening. My question is: Is there something else wrong with the horn that makes this happen or is this normal?
If you have a slant-rotor, you should ONLY be using the main tuning slide (unless you are VERY limber). I have NEVER experienced a "popping" from mine in 30 years of use, but I can't imagine anything that would cause this besides a tiny temperature difference, and even then, so slight that it would not cause any adverse effects.

That's one reason that I love the slant-rotor design so much...

I didn't think so, but that little pop that I get when I press the valves is annoying and sometimes loud enough to be heard...I was just wondering should I vent them to stop this from happening?

windshieldbug · Post by **windshieldbug** » Thu Apr 05, 2007 10:50 pm

Venting the casing between the valve slide tubes would stop this, if the valves are open.

One thing to try first might be to keep the valves depressed when you're not playing for a bit, and see if that makes a difference

Rick Denney · Post by **Rick Denney** » Thu Apr 05, 2007 11:32 pm

Tubaryan12 wrote:I didn't think so, but that little pop that I get when I press the valves is annoying and sometimes loud enough to be heard...I was just wondering should I vent them to stop this from happening?

You can if you want. It also allows you to pull and dump slides without having to depress the valves.

When you play through a run, you might end up with a little residual pressure in a valve branch. If your valves hold that pressure long enough to hear the pop, consider yourself lucky.

I don't see any real downside to venting rotary valves. The hole should be small, and Bloke drills his a bit off-center to get it out of the narrowest big between the casing ports, but still in the part that opens into the valve.

Rick "warning against doing it wrong" Denney

jeopardymaster · Post by **jeopardymaster** » Thu Apr 05, 2007 11:41 pm

Tubaryan12 wrote:On a side note, I get a slight pop of the valves when I press the valves after a rest. I'm guessing venting will stop this from happening. My question is: Is there something else wrong with the horn that makes this happen or is this normal?

First, yes, venting will prevent that. Second: and I'm being unscientific, but I'll step up and be stupid anyway: no, almost certainly there isn't something "wrong" with your horn - what is, well, just, um, IS. Your horn is probably VERY tight, with really good compression - and I'll wager it's a fairly big-bore horn, right? I've noticed the phenomenon on large-bore, tight rotary horns but also on a VERY tight 2165. It has little or nothing to do with pulling slides - you're blowing like an SOB, creating all kinds of pressure inside the various pipes of the horn, and maybe you haven't used one of the valves in a while. Then you press it and you get a little fart sound and maybe even a breeze back at you through the leadpipe. If you're trying to play soft and super legato, it's apt to mess you up. For me, if a good vent job will solve that problem, and it WILL, it's worth it. However, make ABSOLUTELY sure the guy who does it knows WTF he's doing!

Tubaryan12 · Post by **Tubaryan12** » Thu Apr 05, 2007 11:54 pm

jeopardymaster wrote:and maybe you haven't used one of the valves in a while. Then you press it and you get a little fart sound and maybe even a breeze back at you through the leadpipe.

you nailed it. It's one of those things I've been thinking about getting done when I finally get around to having some work done on this thing....that and adding a bunch of spit valves.