Blowing machine

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Terry McGee
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Re: Blowing machine

Post by Terry McGee »

Ah, very good, Tunborough. No rush this end - there are flutes, garden, music crying out for attention. Yes, life can be tough in this #MaluaBayHellHole. The good news is that it sounds like our clobbered-together blowing machine is up for the task so far.

One other thing I should mention about my newly-fangled whistle. I had aimed it to have a windway ceiling of 1.25mm, which seems to be around the average of the whistles I had measured. Since it's of the Sindt-style construction, that means it's entire windway is that height. I wondered how that would go.

I was right to wonder. When I first played it, I felt the whistle lacked verve, and there was a lot of resistance. I found I could blow a fair amount harder and get better performance, but I didn't enjoy needing to push so hard. I rationalised that I needed to reduce the resistance so that less pressure would produce more flow. This suggests tapering the windway so that it started bigger but ended at 1.25mm.

Having resolved that, I needed to decide where to put the taper. At the top of the windway so the jet points down a little? Nice idea, but a hard place to work. But if I dig it into the front top of the stopper, won't I be at risk of pointing the jet up a bit, possibly messing with the voicing? Who cares, we'll learn something, and I can always make another stopper!

I toyed with the idea of milling the taper into the top of the stopper - that wouldn't be hard to do, and would give a uniform depth across the floor. But given the question lingering about jet misdirection, I opted for the easy approach. Using a low-speed very fine sanding belt, I sanded the top of the stopper to a "curved wedge" shape - nothing off the exit end, most off the entry end. When reassembled I had an entry height at the centre of around 2mm, again about what I've been measuring in other whistles.

And playing it confirmed the benefits. The verve I was missing had appeared, and the excess resistance was gone. This was now a rather nice whistle. Which leads me to this observation. It perhaps isn't the whistle so much that needs the tapered windway. You can play it at higher pressure. Perhaps it's more the player that needs the lower pressure produced by the tapered windway? Maybe we are measuring players as well as whistles with our blowing machine.....
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Terry McGee
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Re: Blowing machine

Post by Terry McGee »

Now, is this a truism, or the product of an untutored feverish mind?

We need to set the pressure (by adjusting the windway proportions) so that we are blowing close to the top end of the first regime (low octave) throughout the range when playing comfortably. Otherwise, bumping up into the high regime (2nd octave) will be unnecessarily difficult and potentially unreliable. We risk ending up in no-mans-land in the interregnum. And we won't be getting full value out of the low range - it will play unnecessarily quieter than the upper range.

And when we consider windway proportions are we concerned or unconcerned about the actual path they take from entry to exit? Some I have measured have taken a fairly linear path, so that the height at the midway point is about half the difference between the heights at entry and exit. Others have started off much more parallel until well after the halfway point, suddenly plunging down to the exit height. These latter will presumably present less resistance, as the average height along the way is higher. But is "average height" and "exit height" all we need think about, or are there other issues to contemplate?

Should I be posing these questions to WhistleGPT?
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Re: Blowing machine

Post by hans »

Terry, you are wondering a lot about a taper in the height of the windway, towards its exit. But I think the effect is also achievable with a taper in the width, and keeping a uniform height. As to the shape of the taper (and also the length of the windway): my feeling is that it does not matter, as long as the windway does not add significant additional resistances to the prime resistance to the air flow, which is the narrowest section, namely the exit. And the shape of the exit orifice is most significant, together with its relation to the window (length, width, wall height) and the labium. That windway exit orifice is the most critical part, as it determines the smoothness of the jet ribbon, its shape and direction. Block chamfer and protusion is part of this. Unnecessary rough edges introduce unnecessary turbulence and influence the sound. From my experience that part of the geometry is the most important and needs my utmost attention when making a whistle.
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Terry McGee
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Re: Blowing machine

Post by Terry McGee »

Not convinced you can achieve it all just by lateral tapering, Hans. The windways I've been looking at typically start at around 2mm high and taper (either linearly or abruptly at the end) to around 1.25mm. That's a taper of 1.6 times. If we assumed a window width of 7.5mm, achieving the same taper using lateral tapering only would require an opening width of 12mm. I guess that's possible, but I haven't seen it. But perhaps you do something that dramatic?

(I'm typically seeing around 8mm, a taper of only 1.07 times. And that mild taper probably only intended to help remove the moulded mouthpiece from its mould.)

And I'm not convinced that we only need to take into account the size of the thinnest point, the exit, in assessing resistance and determining flow. If you blow down a drinking straw, you will feel a certain amount of resistance, and it will take you a certain amount of time to exhaust a lungful of air through it. Now snip off a cm of the straw and try blowing through that instead. I reckon you will feel much less resistance, and your lungs will empty much more quickly. It's not just the minimum cross sectional area, it's a factor of length and cross sectional areas. Help us out here, fluid dynamicists!

(It has to be admitted that my chief experience in fluid dynamics is limited to how long it takes me to down a glass of Jameson's. Speaking of which...)

I do agree that the details of the exit are critical to setting up the performance of the whistle. But I'm suggesting that the details of the windway are critical in setting up the performance of the player.

Hmmm, irony. Our topic is blowing machine, to get us away from the limitations of the player. And what have we come back around to?
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Re: Blowing machine

Post by stringbed »

Terry McGee wrote: Hmmm, irony. Our topic is blowing machine, to get us away from the limitations of the player. And what have we come back around to?
I would have thought that the parameters that can be controlled on a blowing machine will be a subset of those utilized by a player, pretty much by definition. Unless we’re heading into the whistle facet of the AI discussion, needing to deal with the “limitations” of the player is surely less a matter of irony than it is of inevitability.
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Re: Blowing machine

Post by Terry McGee »

Remember that this discussion initiated by Tunborough has been largely concerned with flow rates, as these translate easily into wind speeds, which gives him the best comparison with his modelling. Hans (I think) raised blowing pressure, but Tunborough explained why that wasn't so important to the topic at hand from his perspective. None the less, I connected up the manometer to the rig to see what we could learn about that, although I haven't progressed data capture too much as I'm still struggling with setting the base parameters. But having cooked up a new whistle in the meantime, I'm suddenly becoming aware that while the whistle is only concerned with flow, the player is more concerned with pressure. (Hans probably already knew that!) Unless presumably you reduced resistance low enough that the poor player ran out of air, or kept inadvertently falling into the second octave.

So the irony, as I see it, is that we started out aiming to get away from players to discover the base physics of what we are dealing with, but we, or at least I, have been dragged back to seeing it from the player's point of view. Or point of puff....
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Re: Blowing machine

Post by Tunborough »

The theory says that, for a given whistle, the air speed varies directly with the flow rate, the constant being the area of the windway exit. It also says that, for a given whistle and air density, the air speed varies with the square root of the pressure difference. This would mean air flow should vary as the square root of pressure. Once you get your air flow and pressure measurement sorted, you might want to check this by (on one whistle) measuring air flow and pressure over a wide range, and plot air flow and the square root of air pressure to see if you get a straight line that goes through zero.
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Re: Blowing machine

Post by hans »

Terry McGee wrote: Wed Feb 01, 2023 4:25 am Not convinced you can achieve it all just by lateral tapering, Hans. The windways I've been looking at typically start at around 2mm high and taper (either linearly or abruptly at the end) to around 1.25mm. That's a taper of 1.6 times. If we assumed a window width of 7.5mm, achieving the same taper using lateral tapering only would require an opening width of 12mm. I guess that's possible, but I haven't seen it. But perhaps you do something that dramatic?
Terry, I just speak from my experience of making lots of whistles, and they are generally regarded as easy or soft blowers, starting to speak easily with not a great pressure, but still having substantial dynamic range for each note. And I use only a mild taper, the entry perhaps 2mm wider than the exit of the windway, on a typical length of 35mm, and with no taper of height, height being about 1mm or slightly more. I have tried many other whistles which need more blowing pressure, so I can assure you that a whistle capable of being softly blown, as well as firmly, does not need a super large taper of the windway.
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Re: Blowing machine

Post by david_h »

Terry McGee wrote: Wed Feb 01, 2023 6:55 am Unless presumably you reduced resistance low enough that the poor player ran out of air, or kept inadvertently falling into the second octave.
At the optimum jet speed for the note, and the same windway exit, how would reducing the required pressure increase air usage ? Is a player's preferred pressure to do with control?

From Terry's drinking straw analogy can blowing pressure be changed by changing the windway length? How short can a windway be and still do it's job?
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Re: Blowing machine

Post by hans »

david_h wrote: Wed Feb 01, 2023 9:10 am
Terry McGee wrote: Wed Feb 01, 2023 6:55 am Unless presumably you reduced resistance low enough that the poor player ran out of air, or kept inadvertently falling into the second octave.
At the optimum jet speed for the note, and the same windway exit, how would reducing the required pressure increase air usage ? Is a player's preferred pressure to do with control?

From Terry's drinking straw analogy can blowing pressure be changed by changing the windway length? How short can a windway be and still do it's job?
Ha, what Terry wrote sounds like a familiar story for a beginner in whistle playing battling with a mass-produced whistle with the common injection-moulded head!

David, a player's preferred pressure is probably a key variable, we all like it differently. And it has all to do with control and expression. I doubt that there is something like "optimum jet speed", or, at the least, it need to be qualified, as to what it should be the optimum for. And Terry observed earlier in this thread, that as players we become experts at pushing a note to the limit, before it breaks into the higher octave. Or some messy in-between. In fact, pushing a note more than what may be its optimum stable state, is giving it extra texture, some harmonics may start sounding at the same time, and a player will try to control this and use it for good effect.

So, yes, from a player's perspective, pressure and the control of it is the key. But flow comes into it when you start running out of air, and that may be too quickly. This gets quite important playing low whistles.

I think a windway can be pretty short, as short as it is still doing its job as part of the beak, to keep it between the lips. As short as ~10mm, half an inch...
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Re: Blowing machine

Post by david_h »

hans wrote: Wed Feb 01, 2023 10:20 am I doubt that there is something like "optimum jet speed",
I was meaning to play the note in tune on that whistle.
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Re: Blowing machine

Post by Terry McGee »

I wonder if we'd learn anything useful or interesting by asking readers to tell us how close to the breaking point they play say Low D. We'd need to come up with some instructions, eg:

Warm up your whistle by playing some tunes. Then tune the whistle so that Low D is in tune when you play it with your usual pressure. To check this play a run of notes such as D, E, F#, G, F#, E, D, checking the low D against a tuner when you get there. Repeat that run and retune as needed until you are convinced that its in tune with your normal pressure.

Now, play Low D and increase the pressure slowly, noting how many cents sharp you are when it breaks to the next octave or goes unstable. Repeat that process until you are confident that you have a reliable figure for where it breaks. Tell us that figure.

What do we think? Any merit? And are those instructions adequate?

And would we only want the figure, Eg 15 cents, or would we like to know which whistle it applies to? And if they have access to a number of whistles, do we want figures on as many as they are prepared to give us?

And include any other notes? Retune the whistle to that note first?

I've tried a few whistles, and I'm seeing about 10 cents on each of them on Low D. Which given their variety (Killarney, 11.7mm bore; my newly made whistle, 12.7mm bore; Mellow D, 13.5mm bore) is interesting. And I arrive at the pressure on each instantly and assuredly. Seems we humans can be trained. At least by whistles.....
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Re: Blowing machine

Post by Terry McGee »

Now, this thread started out...
Tunborough wrote: Wed Jan 18, 2023 2:31 pm
Terry McGee wrote: Sun Jan 29, 2012 5:25 pm[https://forums.chiffandfipple.com/viewt ... 6#p1056956]
It should be possible with a blowing machine and a good rigid setup. I do hope to get on to building such a machine when I get my backlog under control, and I'll be happy to look at it then.
So, Terry, we're just shy of 11 years on this. How's the blowing machine going?

More seriously, a blowing machine would make a huge difference in our ability to model whistles. Ideally, this blowing machine would deliver a controlled volume flow (ml per second, say) to the whistle. I'm guessing that we'd need a range around 100 ml/sec through 1000 ml/sec. A university lab in France has a blowing machine that delivers a controlled air pressure, but for whistles the volume flow has a more direct impact on what the whistle is doing. (What really matters is the air speed across the window, but volume flow is close enough.)

Does anyone know how I can buy or build such a device on a limited budget?
...but has wandered off a bit since.

Do you still have aspirations to build a blowing machine, Tunborough, in which case should we return to answering the question "how"? Or have we successfully scared you off? Or do you feel we might be able to gather enough data for your modelling purposes without you having to go there?

Where are we at?
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Re: Blowing machine

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Terry McGee wrote: Sat Feb 04, 2023 12:27 am...but has wandered off a bit since.
Well, from my seat in the gallery . . .

1) I wouldn't say "wandered". It has simply emphasized tuning issues. (i.e. at what "feed" (pressure+flow) a whistle speaks "in-tune/on-pitch", or jumps octaves)

2) When I was "dreaming" of making a setup, I had 2 interests: a) how much sound (whistle volume - db) for energy in (pressure*L/m), and b) "voice". My interest in "voice" is the range between "tuning-fork-purity" and the "richness" obtained by a skilled flute player. My own dabblings show that the "rich" voice comes from lots+lots of harmonics.

2) Terry, you have a marvelous set-up. I applaud your "can-do" industriousness :) !

3) One easy thing to do was noted by Tunborough:
Tunborough wrote: Wed Feb 01, 2023 7:36 am . . .you might want to check this by (on one whistle * ) measuring air flow and pressure over a wide range, and plot air flow and the square root of air pressure to see if you get a straight line that goes through zero.
4) Terry, I have a question: can you give some info about your manometers ? Make ? model ? A picture ? I'd be very grateful.

trill

* underline emphasis mine.
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Re: Blowing machine

Post by Terry McGee »

trill wrote: Sat Feb 04, 2023 1:56 am
Terry McGee wrote: Sat Feb 04, 2023 12:27 am...but has wandered off a bit since.
Well, from my seat in the gallery . . .

1) I wouldn't say "wandered". It has simply emphasized tuning issues. (i.e. at what "feed" (pressure+flow) a whistle speaks "in-tune/on-pitch", or jumps octaves)
Well, it's certainly thrown up a lot of issues we need to consider if we want repeatable and meaningful results. And there will probably be more!
2) When I was "dreaming" of making a setup, I had 2 interests: a) how much sound (whistle volume - db) for energy in (pressure*L/m), and b) "voice". My interest in "voice" is the range between "tuning-fork-purity" and the "richness" obtained by a skilled flute player. My own dabblings show that the "rich" voice comes from lots+lots of harmonics.
When we come to wanting to take spectral or level readings (as opposed to pitch and frequency readings) we have to start thinking about the acoustic environment. Once you have continuous tones, you tend to get "standing waves" set up in the room, and these can really mess with your readings. Two easy fixes - hang every spare doona (quilt) in the house around the room, and over and below the test area. Or, take it outside and do the measurements over the lawn. This is where you find out how short-tempered the neighbours are.....
2) Terry, you have a marvelous set-up. I applaud your "can-do" industriousness :) !
So far so good. But as I've said, I'm willing to upgrade if we run into a problem.
3) One easy thing to do was noted by Tunborough:
Tunborough wrote: Wed Feb 01, 2023 7:36 am . . .you might want to check this by (on one whistle * ) measuring air flow and pressure over a wide range, and plot air flow and the square root of air pressure to see if you get a straight line that goes through zero.
Yeah, I reckon that's doable. I'll do a rough tryout and see if we run into any problems. If that's promising, I'll go in deeper.
4) Terry, I have a question: can you give some info about your manometers ? Make ? model ? A picture ? I'd be very grateful.
I have two manometers - the classic U-tube type, which is what I'm using, and a hand-held digital one, which I need to experiment with as I'm not convinced it's working properly.

The U-tube is one I've made - a quick look on the web threw up these YouTube items on how they work and how to make one:

https://www.youtube.com/watch?v=9SQ2FPH ... iChemistry
https://www.youtube.com/watch?v=tWNFVRv ... furnaceman

(Hmmm, U-tubes on YouTube? What will they think of next?)

Let me know if that answers your questions!
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