"turned" rotors

[Matt G]

If you ask people who have played these horns with this procedure, that didn't have it done themselves, you'll probably find that it makes no difference.

I have played two horns of the same make that had this done and the reversal of rotors seemed to be inconsequential. I have not however played the same horn before and after this process to evaluate the difference.

The only modifications that seem to have realistic benefits on rotary horns are the venting of the valves and the scooping of the ports if it is one of those goofy Cerveny's that has rotors smaller than the tubing it is activating.

While I have seen no tangible evidence that this produces an effect at all, I believe that it benefits the player in conversation starters and placebo effect.

[CJ Krause]

***

[cjk]

The concise-length "properly-rotating" #1 rotor offers a guarded slur to that pitch, yet the extended-length "counter-rotating" #4 rotor offers a virtually guaranteed slur to that pitch.

The same "bump" is there (open 4th partial to first valve on the fifth partial) on piston tubas which allegedly slur better than rotor ones. I think the bump there is inherent regardless of which way the valve turns.


Christian

[imperialbari]

***

[JB]

I solved some problems slurring from ...C to D on my CC tuba by getting the inside of my 1st valve slide shaved/tapered a bit. Really did make a big difference...

Could you provide a more detail about the work done, please.

(Where in the valve slide was this, how much was shaved, how was it determind how much to shave, who did the work, where did you come up with this idea, etc.)

This is the first that I have heard of such a modification, and am interested in learning more.

Thanks

[JB]

I solved some problems slurring from ...C to D on my CC tuba by getting the inside of my 1st valve slide shaved/tapered a bit. Really did make a big difference...

Could you provide a more detail about the work done, please.

(Where in the valve slide was this, how much was shaved, how was it determind how much to shave, who did the work, where did you come up with this idea, etc.)

This is the first that I have heard of such a modification, and am interested in learning more.

Thanks

[Matt Walters]

You know, I've never felt or heard the difference in reversing the #3&4 rotors. I do hear and feel the diffrence in venting the valves. Bang for the buck, reversing rotors is not the way to go.

[iiipopes]

OK, since the experience seems to be counter-intuitive that for whatever reason, some people find it easier to slur Bb to C in the staff using open to 4th instead of open to 1st, it begs the question: has anyone turned their rotors so 1 & 2 are the same as 3 & 4, in "reverse" fashion, rather than turning 3 & 4 to match 1 & 2?

[Chuck(G)]

Doesn't this belong under the tuba "fads" thread?

[iiipopes]

To do it to be popular, or because, "that's neat," or for it to come and go after the celebrity tuba player of the day does it, that's one thing. My question in reviving the thread was one of other people's experiences. That goes here. After it's been said and done, if it has been discarded, then it goes to the "fads" thread.

It is quite apparent that it probably has not been done, because of the extended geometry that may be required, but I'll ask again:

Being counter-intuitive, has anyone "reversed" the first two rotors instead?

[Chuck(G)]

Being counter-intuitive, has anyone "reversed" the first two rotors instead?

I thought I mentioned it under the "fads" thread that I've just finished with a tuba that did just that--it's an old Walter Sear string-linkage horn, where the valves rotate just opposite to convention. Because of a lot of damage to the original menchanism, I converted it to uniball.

Rather than move the stop blocks and change the direction of the rotors on ALL valves, I simply brazed "ears" onto the stop arm opposite the stop pin and attached the uniballs to these.

I can't tell any difference between this horn and another more conventionally-equipped horn.

I call "fad".

[iiipopes]

With the experience related, I agree. Now it can be called "fad," and the subject moved over accordingly.

Thanks for posting your experience.

I think one aspect of all this with the rotors is the difference between flow theory and wave theory. The only reason we have any flow of air at all is because it is necessary to some degree with the anatomy of embouchure to get the buzz going and set up the compression/rarefaction cycle. Once that is set up, the actual movement of air is not what happens.

Even though I am not a good fisherman by any sense of the imagination, I have watched waves and wakes of boats. Have you noticed that even though the waves lap at stationary objects, that if you float something aways from shore, that what mostly happens as the waves hit is that the object merely bobs in place up and down without moving significantly laterally as the wave "passes" by.

Air, like water, and as all the engineer members of the forum can correct if I'm stating it wrong, although definitely oversimplified, is also a fluid, and so with the exception of compression properties, reacts very similar: the compressions and rarefactions progress through the horn, but except for the force applied by the breath just to get the buzz going, there is very little lateral movement of the air -- as the "smoke" tests show.

So, I would conclude, and not having any engineering training, just reading and observing others' experiments and experiences, and someone please articulate it better, that the critical element is not how the rotors turn, but just that they're not placed at the critical nodes where the turns or redirection by the rotors, or for that matter pistons, water keys, elbows in the tubing, etc., would interfere with the orderly progression of the compressions and rarefactions. This has been demonstrated for the water keys and to a certain extent a node's "tuneability" by Schilke's experiments.

Boy, what a long-winded way of saying, "FAD!"

Hey, Chuck(G) -- would you post a picture of your converted Sear? Thanks.

[Chuck(G)]

Hey, Chuck(G) -- would you post a picture of your converted Sear? Thanks.

Well consider that the flow rate through a tuba is probably volumetrically almost glacially slow. It's hard to see any fluid dynamic reason for rotor direction to have any bearing on it.

The Sear's being gotten ready for lacquer (buffing and ragging time ) so the keywork and rotors are off, but when that's done, I'll post a photo.

[Chuck(G)]

Doesn't a three-year-old discussion, in and of itself, conflict with the term "fad" anyways?

http://dictionary.reference.com/browse/fad

http://www.bartleby.com/61/89/F0008900.html

Perhaps it was a fad, if so, why are we re-hashing it now?

Because, like hemlines and freezing horns and pistons versus rotors, it's something to talk about.

[Kevin Hendrick]

Doesn't a three-year-old discussion, in and of itself, conflict with the term "fad" anyways?

http://dictionary.reference.com/browse/fad

http://www.bartleby.com/61/89/F0008900.html

Perhaps it was a fad, if so, why are we re-hashing it now?

Because, like hemlines and freezing horns and pistons versus rotors, it's something to talk about.

Sounds like we're not quite "fad up" with it yet ...

[tubamirum]

Awhile ago,Bloke posted the obvious: the rotor has to return to it's original position.

[iiipopes]

Doesn't a three-year-old discussion, in and of itself, conflict with the term "fad" anyways?

http://dictionary.reference.com/browse/fad

http://www.bartleby.com/61/89/F0008900.html

Perhaps it was a fad, if so, why are we re-hashing it now?

Those who do not study history are doomed to repeat it.

[windshieldbug]

"doom"?!?!? maybe you're right

I hear Bill O’Reilly's free..

[kegmcnabb]

.The only modifications that seem to have realistic benefits on rotary horns are the venting of the valves and the scooping of the ports if it is one of those goofy Cerveny's that has rotors smaller than the tubing it is activating.

I have never heard of this particular issue with Cervenys. Please enlighten me further. What models/years were affected by this? Also (forgive my ignorance), what is involved with this"scooping" and is it effective?

[Rick Denney]

I have never heard of this particular issue with Cervenys. Please enlighten me further. What models/years were affected by this? Also (forgive my ignorance), what is involved with this"scooping" and is it effective?

Here is a post by Jay Bertolet describing mods he made, including this one, when he was selling his modified Cerveny 601.

http://www.chisham.com/tips/bbs/mar2000 ... 25105.html

Apparently, Cerveny uses the same valves for their .835-bore tubas as they do for their .810-bore tubas, or something like that.

We haven't heard from Jay in a while but perhaps he still lurks and will add detail.

Rick "who misses Jay's input" Denney