Without sounding like an idiot

[cthuba]

I have a very basic understanding of fizics and maffs and sigh-entz, BUT


I could have sworn one of my teachers played on a rotor tuba where they did not need to press far down on the valve to get the rotor to turn. At least it felt shorter than typical rotor travel.


Is this possible or am I insane?

[the elephant]

The throw of a piston is permanently attached to the bore size of the tunnels through the piston. If it is a .750" bore tuba then the throw of the piston has to be greater than the bore size of .750" to ensure that there is enough space between the two tunnels that it is both structurally sound and there is no leaking. So that means some builders design a throw of at least an inch to make this happen.

Rotors are independent of the lever throw. They are in no way related. Conical bore rotary horns that use five different bores through the valves all have the same lever throw length. The length of the throw is designed into the lever system. Think about a Miraphone 186 for a moment. If you want a shorter throw of the levers, you need to shorten the levers toward the pivot point. This makes it more difficult to press, with a stiffer touch. Lengthen the lever from the pivot point and the throw length increases, but the force needed to press on the same spring decreases a tiny bit. Builders try to hit a sweet spot of how far your finger has to travel with a spring rate that makes that comfortable.

If you want proof of this, look at the longest platen versus the shortest: 4th compared with 2nd. If you measure the travel up and down from the very same part of the platen you will see that 2nd travels a little less than 4th. But if you move your point of measurement on 4th to be the same distance as that point on 2nd they are the same. In fact, you can simply put your finger on the platen in different locations and press the valve down, and you will note that as you get closer to the hinge the travel becomes less but the effort becomes greater. Likewise in the reverse: move the finger further from the hinge and the stroke becomes longer but easier.

[bloke]

I seem to recall that when King (“Conn”) made those 5XJ tubas a decade or two ago, the valve stems, valve bearings, and stop arm plates were built at (probably, to avoid having to create parts for those tubas from scratch) trombone F attachment rotor size. The throw was very short, and some people claimed that they didn’t like it.

Short throws can be equated to higher gears on a bike. More work is concentrated into a shorter human body movement, so it’s probably going to feel harder to push in some way or another.

In my experience, short throws (most rotors, compared to most pistons) require more precision when playing legato, as the movement of the rotor or piston needs to be timed perfectly with the movement of the lip vibration and air for a slur to work nicely on a big old tuba. (I have been reminded of this – once again, now that I’m learning my way around a huge Kaiser B-flat tuba with rotary valves.)

It has always occurred to me that short action pistons and short stroke rotor mechanical set ups were probably designed by engineers to solve problems in tuba playing that really don’t exist, and that they probably actually cause problems that didn’t previously exist.

bloke “Per typical, I’ve supplied too much information – rather than a simple ‘yes’ or ‘no’ – and then an interjected a bunch of opinions“

[cthuba]

I have been playing through Rochut and have been working on smoothing out my open to 1-2 and open to 4 and open 5-2-3 transitions.

Something that didnt seem difficult on a piston .687 bore tuba now seems to need some remediation.


Thanks to both of you!

[matt g]

From memory:

I remember the throw on my MW 32 being shorter than my 188 and 186. Note that this is all over two decades ago.

I don’t notice much difference between my 0.689” bore valve set and the 0.750” valve set. I think that’s because King didn’t try to “over-optimize” the throw on the 0.689” set (likely because they would hold up longer under school use in terms of seal) and the set on my 2165 is the “small valve” setup as opposed to the “big valve” cluster that came along later. For sure that set spreads the fingers a bit more, but part of me feels like the throw is longer also. That might just be the overall bad feels from that set.

The short action valves on the 20Ks are like putting a spoiler on a Buick; it doesn’t really matter. I also had short action Holton valves on a 6/4 BBb. A cool idea, but had I kept that horn, a VMI set was going to replace it. However, back in the late 1990s I played an early creation by @Matt Walters at Dillon Music. I think it was a Buescher bell and bottom bow, King inner bows and branches, and had a Conn short action valve set. That horn was one of the nimblest 4/4-ish CC tubas I’ve ever played. It was sublime. But my current 4/4 CC has the same response characteristics, just without the “fast-forward” valves. I’d be fine with either one, but oiling Conn short action valves is a pain in the butt.

[Mary Ann]

bloke said:

In my experience, short throws (most rotors, compared to most pistons) require more precision when playing legato, as the movement of the rotor or piston needs to be timed perfectly with the movement of the lip vibration and air for a slur to work nicely on a big old tuba. (I have been reminded of this – once again, now that I’m learning my way around a huge Kaiser B-flat tuba with rotary valves.)
-------
I have noticed just in playing different (French) horns that the timing is different on different horns -- you HAVE to change your buzz / air exactly in time with when the valve bottoms out (or tops out, whatever.) I wonder how much that has affected what horn someone buys as their new one, if its valve timing is similar to the old one, and therefore it is "easier to play." Bloke is the first other person I've seen refer to this timing issue with rotors.

I strongly prefer rotors because I can use, basically, playing-the-piano technique on them, and only just now realized that it is because of the "timing for bottoming out" factor along with the fact that my hands are neither big enough nor strong enough to work big ole tuba pistons. Or even euph pistons, although I can otherwise play it.

Huh.

[bloke]

Short-action large-diameter pistons - built to the same tolerances as smaller diameter pistons -are not going to move as fast with the same amount of ease. The tolerances have to be looser in order (to reduce drag) for them to travel at the same speed as pistons with less contact surface area.
Regular tuba pistons really can’t be built quite the same tolerances as trumpet pistons, with an expectation of them traveling at the same speed with the same ease.

[bisontuba]

19th Century 'Allen' rotary valves...

"...This valve type is characterized by long slender rotors; the tubing entering and exiting the rotor is flatter and longer than a normal rotary valve. Its design is attributed to Joseph Lathrop Allen, a Boston brass instrument maker, who produced his first valves of this type sometime after 1853. Allen's intention was to create a quicker action by reducing the diameter of the rotors. Its seemingly effortless movement helped the Allen valve become quite popular among 19th-century American players...."

[matt g]

Short-action large-diameter pistons - built to the same tolerances as smaller diameter pistons -are not going to move as fast with the same amount of ease. The tolerances have to be looser in order (to reduce drag) for them to travel at the same speed as pistons with less contact surface area.
Regular tuba pistons really can’t be built quite the same tolerances as trumpet pistons, with an expectation of them traveling at the same speed with the same ease.

Which is why it makes no sense regarding Melton/Meinl Weston moving to those “big valve” clusters. Supposedly the porting was better? MAW valves in my older 2165 seems to mitigate that issue.

[jtm]

I'm surprised to read about rotor timing being a problem, just because I would have guessed that they're all so quick and short travel that there's not much difference. But I'll certainly believe it.

A fellow in one of my groups recently said that he was very pleased and relieved to find a piston tuba to meat his needs (he's normally a bass trombone player) because he "just can't do rotors." Something about them being too stuffy or hard to blow. That's not something I'd heard before (but I don't get around much, either).

[Mary Ann]

For me, the sheer mass of the pistons, plus their diameter, is what makes them impossible to play. Oval tubes were tried by Conn at one point -- I think I had a Conn baritone that had "oval tubes on their sides" to make valve travel shorter. And oval tubes "standing up" could make valve travel shorter for rotary valves. But -- mass being the same, I can whack my flat fingers down on rotors and cannot do that on pistons; rotors don't "catch" on the way down like pistons can. I think it depends a lot on your hand size and strength which you prefer.
And the "bottoming out factor" for rotors is most important when playing slow legato music in which the notes are not tongued; to get the slurs smooth, you just have to have the valve's "end positioning" timed right. I am the ONLY person I have heard slur on a (French) horn in slower passages like a string player does, without the audible "wah wah slurs" that you will hear from horn players (and which drives me nuts but is across the board with them, including the high level pros. It seems to be "cultural" in a sense, and people just pick it up because they don't have a background with stringed instrument slurring. I think the wah-wahs are because they have never gotten the concept that you don't have to do that if you time the valve changes correctly. But I'm off on one of my soap boxes, and not even a very big one at that, just hearing my head rattle this morning.)

[Rick Denney]

A rotor must always turn 90 degrees no matter how big it is. So, the stop arm must spin it that far. That’s just as true for French horn rotors as for Rudolf Meinl 6/4 rotors.

The amount the end of the stop arm must move to make the rotor spin 90 degrees is entirely based on its length. The longer the stop arm, the longer its linkage end must be moved.

The other end of that linkage is on the paddle lever, which rotates around the paddle shaft. The longer the paddle lever from the shaft to the linkage, the longer it must travel.

And the longer the paddle lever from the paddle shaft to the fingertip, the farther it must move.

So, a rotary valve with a long stop arm, a long paddle lever distance from the paddle shaft to the linkage, and a long paddle lever distance from the shaft to the fingertip may have quite a long the throw. It is entirely possible to design a rotary linkage with as long a throw as a piston for the same bore. But with a short stop arm and short paddle lever dimensions, a rotor can have a very short throw.

Usually it is designed with a shorter throw than a piston valve of the same bore.

However: the longer the throw, the greater the leverage and the lighter the action. So there is a balance between speed and lightness that players have to optimize for themselves. Each player will develop preferences, and will apply that preference even if subconsciously when evaluating instruments.

And: the bigger the valve, the heavier it is for a given design. The heavier it is, the bigger the return spring must be. And that has as much effect (or more) on the heaviness of the action as the leverage built into the linkage. Rotors are usually solid and heavy despite their compact size, and pistons are hollow and light for their size.

All these competing effects lead people to draw conclusions from limited samples that they then express as immutable truth.

Rick “helping with the basic mechanics part” Denney

[matt g]

Oval entry/exit ports on a rotary valve might provide for a smaller diameter of the valve at the expense of height of the cylinder.

It’s a fairly even trade. What you might make up in mass or throw, you’d definitely lose in terms of cost to tool and assemble these valves and I’d suspect that the distortion of the waveguide through this process might introduce unwanted issues.

ETA:

What @bisontuba mentioned earlier.

http://collections.nmmusd.org/UtleyPage ... Allen.html

[bloke]

Miraphone has done a lot to help out with dealing with very large bore sizes combined with rotary valves, but there’s just so much that can be done, and then there’s still the adding or removal of vast cubic inches of space within air column (with a 21.2mm bore size) that must be dealt with by the player’s facial vibration.
With fatbastard, I would say that - via couple of strategies - Miraphone has made the rotors move almost as quickly as normal rotors, as they managed to eliminate quite a bit of the surface area - yet leaving one of the rotor bodies larger (probably thinking it would reduce resistance, but I’m thinking that but that wasn’t very helpful…but it probably didn’t hurt anything).
I would be interested in hollow rotors, but I believe only the Czech people have experimented with those (perhaps a 1/8 inch thick tapered outer wall connected to the center spindle, and then the cut-ins brazed in place and made of sheet metal).
Anyway, it makes me giggle to play a tuba this large - offering the type of resonance that it offers, with its valves moving nearly as quickly as normal-size tuba valves, and with the instrument being so easy to play in tune. It turns heads (not after people catch a glimpse of it, but) when they hear what type of sound is being emitted from it.

[bloke]

Yamaha’s porting on their larger bore pistons (.728” and .750”) is the most clever of all.
Weril copied it on its sousaphones, though the materials I and plating were crappy.

Short-action large-diameter pistons - built to the same tolerances as smaller diameter pistons -are not going to move as fast with the same amount of ease. The tolerances have to be looser in order (to reduce drag) for them to travel at the same speed as pistons with less contact surface area.
Regular tuba pistons really can’t be built quite the same tolerances as trumpet pistons, with an expectation of them traveling at the same speed with the same ease.

Which is why it makes no sense regarding Melton/Meinl Weston moving to those “big valve” clusters. Supposedly the porting was better? MAW valves in my older 2165 seems to mitigate that issue.