1291 bbb - valve compression

[Wilco]

Hi, I get a good compression when I pull the 1st and 2nd valve slide. I get absolutely no compression when I pull the 3rd and the 4th slide???? How come? Is this a problem? I get 'some' compression when I plug the bottom valve cap with my finger....

[cjk]

Is your valve alignment lousy?

[Wilco]

Is your valve alignment lousy?

Dunno, how lousy to get no compression? how to check?

[bort]

Hi, I get a good compression when I pull the 1st and 2nd valve slide. I get absolutely no compression when I pull the 3rd and the 4th slide???? How come? Is this a problem? I get 'some' compression when I plug the bottom valve cap with my finger....

At least on my 1291 CC, the valves are vented. (You can check - take the valve out...on the side of the valve, near the bottom, does it look like there's a small hole drilled in it?)

However, I don't know why only the 3rd and 4th valves would be vented. I'd think the 1st valve would be an obvious candidate for this...

[MartyNeilan]

Hi, I get a good compression when I pull the 1st and 2nd valve slide. I get absolutely no compression when I pull the 3rd and the 4th slide???? How come?

Are there conventional water keys with corks (aka spit valves) on your 3rd and 4th slides? If so, that might explain the difference, as the corks may not maintain high air pressure.

In reference to a recent response, I am not sure how spring tension would affect valve compression. The clearance between the piston (or rotor) and sleeve should not have anything to do with spring tension, unless the springs were so weak that the pistons were sagging enough to make the ports grossly misaligned.

FWIW, Hetmas's "Classic" piston valve oil does wonders for older horns with a large tolerance between the piston and sleeve.

[Wilco]

Word from Miraphone:

Dear Mr. Ouwerkerk,

thank you for your message. We would like to explain that the tubas are built this way (compression only on 1st and 2nd valve), because this was the demand of the market.

So we can assure you that this is no defect or disadvantage.

Yours sincerely,

Eva Staudinger
Sales Assistant

[WakinAZ]

Does she mean "venting" on 1st and 2nd valve only instead of "compression"? Seems like all four valves should have good compression, which is why you are posting in the first place.

So, per Marty's post, are there water key corks that might be leaking air on these 3rd and 4th valve slides?

Eric "confused" L.

[DaTubaKid]

Does she mean "venting" on 1st and 2nd valve only instead of "compression"? Seems like all four valves should have good compression, which is why you are posting in the first place.

It sounds like she means valves 1 and 2 are not vented.

Wilco, did you get a chance to take a look at your valves and see which had a hole drilled into? I just looked at my CC 1291 valves and all of them are vented (had never even thought to look at em until now).

Part of me keeps wanting to think that all this talk about compression is in regards to the compression of the valve, instead of the compression of air when an unvented valve slide is pushed or pulled. I think that's what tubashaman might have been referring to?

Are there conventional water keys with corks (aka spit valves) on your 3rd and 4th slides? If so, that might explain the difference, as the corks may not maintain high air pressure.

If valves 3 and 4 are vented, this really wouldn't matter (much) anymore, would it?

[cjk]

maybe all 4 valves are vented, but the vents in 1 + 2 are clogged.