hollow rotors

[bloke]

I suspect that I may have a different opinion of what a dent is.

When the circular valve casing is exposed, that casing exposed surface is convex. When someone puts an artificial span on a rotor and makes two round holes into what many incorrectly assume to be a round-and-bore-sized passage, that span is concave. I consider dents to be concave, and I consider that artificial span - as it is clearly concave and dent-shaped - to be a dent.

Also, your picture of the tubes leading into rotors are shapes that I see occasionally, but otherwise, there's a rounded extension on the outside edge, and even casings themselves are rounded (feeding into their casings and - again - rarely sharp-edged... but when two people having a discussion, both start becoming redundant, and end up making the same points over and over, that's when it's clear that either they completely disagree on a point or that neither understands the other. I've already admitted that I'm skeptical regarding acoustical claims being things that are necessarily better or worse for the sound or the musician - even if they can be demonstrated on scopes and such. Whether your design or a classic design disturbs the airflow more or less doesn't necessarily mean that some player is going to "like" ("like" being a very unscientific word) it more or less.

I don't actually "like" Martin Wilk's pistons due to the things that they do through the porting (whereby the volume of one passage is diminished in order to avoid interrupting the smoothness of the other two). Admittedly, I personally "like" Martin's pistons because I can drive them just as fast as heavier pistons - yet with lighter springs (as they weigh so much less). I'm interested in speed and light touch, with both pistons and rotors. If yours offer speed and light touch, I can easily cut out the chunk of metal between the two round holes - and smooth off the edges (again: if I don't "like" the dent-which-you-represent-as-anti-dent, whether I were to either "like" or "dislike" that feature for a scientific, non-scientific. or even aesthetic reason).


I don't judge your opinions (in regards to sound or ease of playing not related to speed or touch) of what you are showing me to be correct for certain and I don't necessarily judge my opinions to be correct for certain. A skeptic is biased against everything until they are convinced, and a proper skeptic is also skeptical of their own opinions.

As another example, Vienna valves certainly aren't particularly acoustically luxurious on paper, but people have told me that they sure have been impressed with some horns on which those valves are installed.

Further, I've had all these same sorts of discussions with people who sell water keys they've designed which attempt to avoid using a nipple. They've convinced me of nothing and I've convinced them of nothing.

lighter touch and faster motion:
Those features are pretty easy (for me) to observe.
Beyond those observations, I'm probably shrugging my shoulders.

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to review once again:
- I cannot hope to (nor even hope to order a 3D printer to) build one of your rotors, and I assume you absolutely can...amazing, and a very sincerely offered "bravo"
- If it can be made so as to drop into an existing casing WITHOUT lapping and WITH the factory rotor still fitting as well as ever, it is intriguing, and I don't need any acoustical/sound claims (assuming it's lighter and faster) to be intrigued...
...so (again)
- it's important to me that you not interpret my verbiage as negative, as I strive to consistently be (though - admittedly - I often fail) a classical skeptic.

https://plato.stanford.edu/entries/skepticism-ancient/

[bloke]

I just saw where Mark Atkinson is currently fabricating a set of hollow rotors for (I believe) an Engelbert Schmid TRIPLE horn.

...likely slightly oversize to replace old worn rotors...with new (hopefully) lighter/faster ones.

[bloke]

...so Mark Atkinson is showing off his completed set of three triple rotors...not made of bored out solid cylindrical brass, but (basically) made from stock very similar to slide tubing.

These are fitted to the casings and ready to call the owner to pick up.

[MiBrassFS]

It’s nice when people are proud of their work.

[Mary Ann]

Just my passing meaningless comments about acoustical claims etc.: Seems that somewhere in there, turbulence, (lack of) has to come into it. Would there exist a mathematical curve somewhere showing a range of turbulence related to either sound or playability or both? Certainly seems like lack of rough edges and correct alignments would have something to do with that.With resonance, I just remembered way back with two-stroke motorcycles, that their pipes were resonance chambers, and at certain rpms we said the engine was "on the pipe" and that was max horsepower. The concept seems to have relevance to overall instrument design, and I wonder if ever there was an exchange of math.
I will always wonder what was up with that Hagen that did not want to have air blown through it.

[bloke]

First, I'm going to discuss andl observed personal exception, and then I'm going to discuss what usually occurs, at least in my opinion:
-------------
I have noticed with the giant B-flat tuba of mine that the first valve slide (which is remarkably well-aligned and actually requires a stop rod to not fall on the floor, YET not leaky...ie fitting as well as a perfectly parallel and coplanar pair of piston valves) will actually jump a bit when I'm playing certain pitches which involve the first circuit and ONLY when I'm putting an extraordinarily large amount of air through the instrument during some particularly loud passage, but - otherwise - when I'm playing (and when we are all playing) our embouchures generally dictate that we are trying to NOT blow very much air at all through our instruments, as we nearly allow our lips to touch and blow very small amounts of air between them with the two lips vibrating as if a double reed and vibrating the air which is already in the instrument setting up very little additional flow of air through our instruments, and particularly not through tubas) is why I always sort of make a bit of a face when anyone starts to discuss "flow of air" through a wind instrument (again, particularly when through a tuba).

To put it more simply, so many people make a big deal about "torturous bends" and jutting out places within instruments when the most resistance that we encounter is between our own lips. I do think it's sort of neat to build an instrument whereby the interior is fairly elegantly smooth, but I'm not sure that it accomplishes a whole lot.

[peterbas]

Just my passing meaningless comments about acoustical claims etc.: Seems that somewhere in there, turbulence, (lack of) has to come into it. Would there exist a mathematical curve somewhere showing a range of turbulence related to either sound or playability or both? Certainly seems like lack of rough edges and correct alignments would have something to do with that.With resonance, I just remembered way back with two-stroke motorcycles, that their pipes were resonance chambers, and at certain rpms we said the engine was "on the pipe" and that was max horsepower. The concept seems to have relevance to overall instrument design, and I wonder if ever there was an exchange of math.
I will always wonder what was up with that Hagen that did not want to have air blown through it.

For an engine you need to pass a lot of air through it for it to be efficient.
For a tuba you want as little as possible of air going through it to be efficient.
The air molecules in the tuba just move a little front to back.
About 10% of the energy gets lost at the bell to be converted to a sound.

[Mary Ann]

It is the waves moving back and forth that need a lack of rough edges, and also the waves that need resonance. I don't think the comparison of air flows is apropos to what I was talking about.

[bloke]

A stack of rotors is a series of zigzags and pinched/distorted-shaped (regardless of whose diagram) bore areas. Columns of vibrating air seem to be able to negotiate them.

[peterbas]

It is the waves moving back and forth that need a lack of rough edges, and also the waves that need resonance. I don't think the comparison of air flows is apropos to what I was talking about.

In an exhaust you don't normally want reflected waves because they slow down the exhaust gasses.
In a tuba reflected waves are essential to create the standing waves. The question is if early reflections makes playing easier or not and does it matter at which distances they are created. Remember the plastic insert from years back that was supposed to make notes start easier.


But, that two stroke exhaust is designed to generate two reflected waves. One to get a vacuum when the outlet valve is open so to empty the cylinder as fast as possible and second to get a high pressure at the same place when the inlet is opening to stop the fresh air leaving through the closing outlet. The expansion creates the first wave and the decrease in diameter creates the second wave.

[Mary Ann]

I remember that silly plastic insert -- at the time I had a MW 182 F and the low C was inaccessible to me. The seller of those things assured me it would fix the problem, so I spent the $3 or whatever it was. I realized pretty quickly it fit the description of "placebo" and sent it back for a refund, apparently one of the very, very few who did that, probably because most people would just blow off that small amount of money. Under protest, they refunded my money. I really don't like scammers. There is the guy though, whom I love to refer to, who fixed his low C by dropping his mouthpiece on the bell branch, apparently fixing the node problem.

[bloke]

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