Greenhoe valve issue?

[ChadA]

I have a Conn 88HTG, one of those built as a collaboration between pre-Schilke Greenhoe and Conn Selmer. It's not an aftermarket conversion. I love so many things about that horn, but not the valve. Maybe that's not quite true. I love the feeling of the valve once you get in it, but I can almost never slur into it smoothly. There's always a blip/pop/rough transition, especially if my handslide is moving inward at the same time (like slurring from to ). It's slightly better after my tech adjusted the spring tension to be slightly heavier and slightly better if I adjust my thumb position a certain way, but it's never easy and reliable, like on my Shires bass valves or any other tenor I've ever owned and played (Getzen 4147 IB, Benge 190F, Yamaha 882O, Elkhart 88H, corp Bach 42B).

Matthew Walker made this comment in another thread and it stuck with me, as it sounds similar to the the issue I have:

You're also reversing the direction of the valve rotation, which will.make slurring into and out of the valve notes much noisier in the transition.

Is there anything I can do do make slurring into the valve better? Out is less of an issue, but slurring in pretty much always is a problem.

[Matt K]

Are greenhoe valves vented? I had an original Shires valve from the 90s. I don’t remember the exact details but there was some degree of similarity between Greenhoe and Shires rotors or something in the 90s. At any rate, I had mine vented when I was prepping for an audition that did Saint-Saens 3 on it. Made the switch from Ab to Bb in T3 a little smoother, which is obviously super important for that excerpt. The valve might be internally vented though so that may be useless.

[Burgerbob]

This is exactly the reason I don't really like Greenhoes. I can't get a good valve legato on them, there's an audible articulation no matter what I do. I find this is present on most rotors, but the most obvious on Greenhoes. Great in every other way.

[tbonesullivan]

Does the Greenhoe rotate in a different direction than most valves? I though most were moving clockwise when viewed from the linkage side of the horn.

I've only really thought about valve rotation directly after reading the writeup for the Yamaha YBL-830, where they make a big deal about it the second valve rotating in a different direction than the YBL-613H.

[ChadA]

I talked to my tech and he had some pics of a GH rotor. The issue isn't with the valve direction (okay, I'm a doofus). It's with the webbing between the ports. It's apparently large enough that it mostly closes things off when it travels. The first pic shows a valve core with the "stuff" between the ports. The second pic shows calipers set to the diameter of the port, showing that the webbing is most of the diameter of the port.

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No other rotor I've ever taken apart has that stuff between the ports. I guess that's why I never experienced that issue before.

[Matt K]

Interesting. I thought the GHs were vented on the inside somehow but now that I think about it, I'm not sure where I heard that.

[ChadA]

The scallops do provide some venting, but not enough to counteract the mostly closed issue when it spins.

[elmsandr]

...
No other rotor I've ever taken apart has that stuff between the ports. I guess that's why I never experienced that issue before.

That's the whole point of the difference of a Greenhoe rotor. That is what "Full in-tact duct" means. That bit of web allows for the air passage to be a full tube through the rotor core rather than force the casing of the rotor to be part of the tube.

Similarly, the venting usually means that there is a path for air to escape on the attachment side of the valve when it is NOT actuated. I don't know where exactly on this rotor that would be, but the idea is that there would not be a pressure build-up on the attachment tubing that would "pop" when the valve is actuated. For example, if you moved the tuning slide without engaging the valve no pressure or vacuum would be created. On old rotors you could accomplish that by drilling a hole in the casing between the attachment ports so it would go through to the spot that is now covered by that 'web' on the attachment side. Open to the environment except when the valve is engaged. Don't think that is at all what they do here, but have not thought much about it.

Cheers,
Andy

[ithinknot]

There are two types of venting.

The kind that Andy describes - avoiding pressure build-up in the attachment tubing, achieved through venting the casing so that the valve loop leaks when not engaged - is useful on tubas and other instruments where the player is adjusting slides on the go, thus avoiding pops and kicks to the teeth when the valve is finally engaged. This doesn't really have any value on a trombone (except maybe a single valve bass with 'Bartok slide' mechanism ). It's true that there can also be pressure differentials arising in extreme or changeable environmental conditions, but in such circumstances valve popping is probably the least of the player's worries.

The other kind is allowing an extra continuous air path during valve actuation. As Chad says, the scallops provide this on the Greenhoe design pictured above. (Picture the 'above and below' scallops with the calipers rotated 90 deg, if that helps...) Within the travel of a conventional (theoretically sealing!) rotor, the travel includes two periods where there's still only one air path but with reduced aperture, and a middle period where both paths are partially open. Venting may reduce the pressure fluctuations across these transitions, but with new air routes comes the possibility of new noises.

[JoeAumann]

I got off of my Greenhoe valves for this very reason, and switched to M&W. Best, smoothest rotary valve on the market.