Estimating bugle length with vinyl tubing?

[LargeTuba]

I’m going to attempt to put a tuba in CC by fabricating every branch past the third. So the real question is if its possible to estimate what taper/length the bows need to be by cutting up and using vinyl tubing? Will the intonation and pitch tendencies be the same as the real deal? Is be worth my time?

Also a side question: what’s the best way to measure the bugel’s length, I have a sewing measuring tape but always feel like I’m not measuring in the best spot or getting inaccurate results.

Thanks!

[Dan Schultz]

The proportion between a BBb tuba and a CC tuba is 18/16. There is no way to use engineering to determine EXACTLY what you need to remove from the open bugle and each valve circuit but the ratio will give you a good start. I tend to leave things on the long side so I can made adjustments as needed.

I've used Vinyl tubing or garden hose to approximate lengths. I also use a seamstress tape to measure horns and try to look at the point of measurement as the centerline. If you measure on the outside of all of the bends you will be a dab long while if you measure the inside of the bends you will be a little short.

Good luck and have fun. It's all about prototyping!

[matt g]

Ideally, if you can measure the outside of the radius and the inside of the radius, the average should be pretty close to the centerline length.

One issue with brass instruments is that the fundamental frequency isn’t simply the length of the bugle but also dependent on the volume. For example, a 6/4 Yorkophone is less tubing length than a Yamaha YCB-621.

[UncleBeer]

Don't forget about the end effect.

[matt g]

Don't forget about the end effect.

That “end effect” on a conical taper, especially one like a tuba, is probably even messier mathematics. But that’s a good start. For others, note that the calculations are for an open pipe in the example.

I do wonder if the impedance drop is a bit closer on a wide throat tuba.

[UncleBeer]

For others, note that the calculations are for an open pipe in the example.

While technically a "closed pipe", due to its conicity, the tuba acts acoustically as an open pipe. https://newt.phys.unsw.edu.au/jw/pipes.html

[matt g]

For others, note that the calculations are for an open pipe in the example.

While technically a "closed pipe", due to its conicity, the tuba acts acoustically as an open pipe. https://newt.phys.unsw.edu.au/jw/pipes.html

That’s a cool find! Thank you for sharing it.

[bloke]

*Some of that is just a little bit silly:
(ie. The VAST MAJORITY of it is NOT-AT-ALL silly.)

- The B-flat clarinet (when extreme ranges of the two are compared) only plays a little bit lower than the flute, and (particularly as it jumps to the 6th partial, rather than to the 2nd) plays just about as high as a flute, as well, and both instruments (in their highest ranges) jump up to higher partials.

- The B-flat clarinet's lowest pitches are only a a few pitches lower than a flute's ("concert" D below a flute's "concert B).
- The main reason is because a B-flat clarinet is longer than a (C) flute...as a flute ends (not at the "crown", but - in reality) just barely to the left (player's orientation) of the embouchure hole.

- a demonstration of double-high "concert" B-flat on clarinet (above the 5th ledger line above the treble clef)
https://www.youtube.com/watch?time_cont ... e=emb_logo

- The flute's "official" highest pitch is a step higher ("concert" C), but some players can play a bit higher (but - then again - so can some clarinetists). Even if you can find a flautist who can squeak out an extremely-high D or E,(again) the clarinet can be played nearly as high, and the clarinet's overall range is still wider (only up to the clarinet's "official" highest pitch, which is - again - "concert" B-flat).
__________________________________________________
*again: some...I'm NOT condemning the vast majority of what's found on the link, (because I'm not of the same mindset as those so-called "fact-checkers" on fb, who quibble with 99% true articles, whereby they disagree with the use of an adjective or adverb in one sentence or one paragraph - always based on a so-called "fact-checker's socio-political p.o.v.'s)]

bloke "I don't build very many 'frankentubas' (INCREDIBLE investments in time, if they're to be built worth a crap), but either find ways to ACOUSTICALLY test (before building myself into a corner) or build in late-in-design-alteration-possible 'fail-safes', because measuring stuff often does not offer the acoustically-correct 'answers' to the questions."

[Yorkboy]

Don't forget about the end effect.

True, thank you for posting that info. So, for a conical tube, I’d assume the adjustment is based on the average of all the radii that occur over the length of the instrument? That would be messy, indeed!

Truth be told, I’ve always wanted to understand this phenomenon better - unfortunately all those numbers do nothing but give me a headache

Yorkboy “who has never claimed that higher math was a strong suit”

[UncleBeer]

all those numbers do nothing but give me a headache

Here's the important bit:

This “end effect” is equal to 61% of the radius
of the pipe. This end effect must be added to the
length of the closed pipe and added twice to the
length of the open pipe.

So...for a 20 inch bell, the radius is 10 inches. Multiply by .61 and double it (open pipe). The end effect in this case is 12.2". That's how far 'acoustical tuba' extends past the end of your 20" bell.

[matt g]

@bloke, regarding your footnote above, true assessment of a model (which the formula is) lies in observation of reality.

The nice thing about the model here is that it gives a point of departure for doing initial estimations and fabrication, knowing that a (clever) person should build in design “safety valves” to allow for alterations as needed.

Lots of little things can effect the intonation of the horn. Matt Walters pointed out a small difference on the fifth or sixth branch of some tubas making a huge difference on the overall scale.

Sometimes it’s amazing that these collections of plumbing work at all! :-)

[bloke]

I strongly suspect that the proportional diameter of large upper bows might control some of the most profound effects of all on intonation characteristics, but Frankentubists don’t really discuss this, as they don’t possess the tooling to significantly alter the large upper bows of tubas.

Old Martin 6/4 tubas - arguably - offer just about the best intonation characteristics (well...along with Miraphone 98 tubas) of any 6/4 tubas - and Martin upper large upper bows are just about the largest of all, but - in proportion to their bottom bows - they may not (??) be proportionally as large as some others on some other instruments... People can post graphs and numbers, and diagrams of tapers, but this stuff is still all a mystery, and it’s still all trial and error.
I do suspect that the shorter an instrument’s bugle, the more difficult it is to get it to be able to play be played in tune easily - when that instrument is built to huge proportions…which is probably why the C-length 6/4 tubas (as were many of the century-ago “monster” E-flat tubas) are often intonation nightmares.

[Yorkboy]

I do suspect that the shorter an instrument’s bugle, the more difficult it is to get it to be able to play be played in tune easily - when that instrument is built to huge proportions…which is probably why the C-length 6/4 tubas (as were many of the century-ago “monster” E-flat tubas) are often intonation nightmares.

(emphasis added)

After having had discussions with folks much more knowledgeable than I on the subject, I’ve come to agree that the “root” of this issue on monster E flats* most likely resides in the rapid taper of the top bow - these horns were designed using the bell and bottom bow of 18’ (BBb) tubas; in order to achieve the same required taper in 5 feet less of length (ie “Eb tubas”) they chose to accomplish the lion’s share of the reduction at that point.

Many of these problems don’t exist in the same capacity when the bugle and taper are sized accordingly to the length (such as in smaller “pea-shooter” E flat tubas).

* just to illustrate the fickle nature of all this, I’ve also played some monster E flat tubas that do not present this problem.....

[Yorkboy]

all those numbers do nothing but give me a headache

Here's the important bit:

This “end effect” is equal to 61% of the radius
of the pipe. This end effect must be added to the
length of the closed pipe and added twice to the
length of the open pipe.

So...for a 20 inch bell, the radius is 10 inches. Multiply by .61 and double it (open pipe). The end effect in this case is 12.2". That's how far 'acoustical tuba' extends past the end of your 20" bell.

Believe it or not, this is where I get lost.

I’m currently taking a York 700 and converting it from top to side-action. If I’m fortunate enough to start with a horn that plays adequately, I sit down with a tuner, figure out where it plays in tune, and then measure it multiple times before disassembly, and multiple times after it’s in pieces, as well. This particular instrument plays in tune at a length of 214.25”; with an 18.5” bell, this would mean that the acoustical length of the horn would actually be over 225 inches - (9.25” x .61) x 2 = 11.28” - could this be possible if there’s an end effect that adds almost a foot of length?

- I must be missing something here - not making an argument, just trying to grasp what is going on with all this.

Yorkboy “thick as a brick when it comes to math and science concepts”

[UncleBeer]

People can post graphs and numbers, and diagrams of tapers, but this stuff is still all a mystery, and it’s still all trial and error.

I've been dying to get my hands on a software package called Brass Instrument Analysis System (BIAS). It sends a tone through the instrument and can objectively determine intonation, early reflections (mismatched bores, blobs of solder, etc) and even do physical modeling, where one could predict the result of a (for instance) smaller top bow. Only hitch: $7,000 price tag.

[UncleBeer]

This particular instrument plays in tune at a length of 214.25”; with an 18.5” bell, this would mean that the acoustical length of the horn would actually be over 225 inches - (9.25” x .61) x 2 = 11.28” - could this be possible if there’s an end effect that adds almost a foot of length?

That's my understanding of all this.

[bloke]

Judging by the intonation characteristics of many of the fairly recent-issue new models, that program/device must be "new this year".

[UncleBeer]

I saw it used at Meinl-Weston/Melton years ago.

[bloke]

I understand... ' just being a wise-@$$...

[Tubajug]

This particular instrument plays in tune at a length of 214.25”; with an 18.5” bell, this would mean that the acoustical length of the horn would actually be over 225 inches - (9.25” x .61) x 2 = 11.28” - could this be possible if there’s an end effect that adds almost a foot of length?

That's my understanding of all this.

I'm jumping in here trying to understand a bit of this as well.

So for simplicity's sake, let's go with the 16 foot length of a CC tuba (192 inches). If it's got a 20" bell (which the one I'd like to build actually does...), the bugle itself only needs to be about 180 inches long to account for that 12 inches of end effect?

That would actually help me a lot since I'm cutting a BBb bugle. That would mean a good deal less tubing to cut (12 inches vs. a full 24).